POLITECNICO DI MILANO Facoltà di Ingegneria Industriale Corso di Laurea in Ingegneria Energetica Mathematical model of Lublin-Wrotków Power Plant (Combined Cycle) by using GateCycle Software Relatore: Prof. Paolo CHIESA Co-relatore: Dr. Jarosław MILEWSKI (Warsaw University of Technology) Tesi di Laurea di: Diego SANTIN Anno Accademico 2010 - 2011 Matr. 740374 Table of Contents RESEARCH MOTIVATIONS ............................................................................................... 5 1 INTRODUCTION ........................................................................................................... 7 1.1 Elektrociepłownia Gorzów .............................................................................................................................. 9 1.1.1 Technical features ................................................................................................................................. 10 1.1.2 New summer configuration .................................................................................................................. 10 1.2 Elektrociepłownia Lublin-Wrotków ............................................................................................................ 11 1.2.1 Technical features ................................................................................................................................. 12 1.3 Elektrociepłownia Nowa Sarzyna ................................................................................................................. 15 1.4 Elektrociepłownia Rzeszów ........................................................................................................................... 16 1.4.1 Summer and winter configurations ....................................................................................................... 16 1.5 Elektrociepłownia Zielona Góra ................................................................................................................... 18 1.5.1 Technical features ................................................................................................................................. 19 1.6 Summary ........................................................................................................................................................ 21 2 THEORY ..................................................................................................................... 23 2.1 Thermodynamic cycles .................................................................................................................................. 23 2.1.1 Carnot cycle .......................................................................................................................................... 23 2.1.2 Brayton cycle ........................................................................................................................................ 23 2.1.3 Rankine cycle ....................................................................................................................................... 25 2.1.4 Combined cycle .................................................................................................................................... 26 2.2 Heat Exchange (T-Q diagram) ..................................................................................................................... 27 2.3 Steam and water calculation ......................................................................................................................... 27 2.4 Chemical reaction of combustion ................................................................................................................. 28 2.4.1 GateCycle methods ............................................................................................................................... 28 2.5 LHV and HHV ............................................................................................................................................... 29 2.6 Pump ............................................................................................................................................................... 30 2.7 Steam turbine ................................................................................................................................................. 30 2.8 Total efficiency of the system ........................................................................................................................ 31 2.9 Summary ........................................................................................................................................................ 31 3 MODELING OF LUBLIN-WROTKÓW CHP POWER PLANT .................................... 32 3.1 Presentation of the work ............................................................................................................................... 32 3.1.1 Properties methods ............................................................................................................................... 32 3.1.2 Data paper............................................................................................................................................. 32 3.2 Software analisys ........................................................................................................................................... 33 3.2.1 Design point conditions ........................................................................................................................ 33 2 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 3.2.8 3.2.9 3.2.10 3.2.11 3.2.12 3.2.13 3.2.14 3.2.15 3.2.16 3.2.17 3.2.18 3.2.19 3.2.20 3.2.21 3.2.22 3.2.23 3.2.24 3.2.25 3.2.26 3.2.27 3.2.28 3.2.29 3.2.30 3.2.31 Gas turbine V94.2 ................................................................................................................................. 33 Superheater n. 3 .................................................................................................................................... 36 Pipeline n.1 ........................................................................................................................................... 38 Steam Turbine n.1 ................................................................................................................................ 39 Steam Turbine n.2 ................................................................................................................................ 40 Superheater n.2 ..................................................................................................................................... 41 Evaporator n.2 ...................................................................................................................................... 43 Superheater n.1 ..................................................................................................................................... 45 Pipeline n.2 ........................................................................................................................................... 46 Mixer n.2 .............................................................................................................................................. 47 Economizer n.2 ..................................................................................................................................... 48 Evaporator n.1 ...................................................................................................................................... 49 Economizer n.1 ..................................................................................................................................... 50 Steam Turbine n.3 ................................................................................................................................ 52 Valve n.1 .............................................................................................................................................. 53 Heat Exchanger n.1............................................................................................................................... 56 Splitter n.2 ............................................................................................................................................ 57 Pump n.1, Pump n.2 ............................................................................................................................. 59 Steam Turbine n.4 ................................................................................................................................ 61 Splitter n.3 ............................................................................................................................................ 62 Steam Turbine n.5 ................................................................................................................................ 63 Condenser n. 1 ...................................................................................................................................... 65 Pipeline n.3 ........................................................................................................................................... 66 Temperature Control Mixer n.1 ............................................................................................................ 68 Feedwater Heater n.1 ............................................................................................................................ 69 Pump n.3, Pump n.4, Mixer n.3 ............................................................................................................ 71 Economizer n. 3 .................................................................................................................................... 72 Exhaust Gas Conditioning System ....................................................................................................... 74 Mixer n.4, Splitter n.5 ........................................................................................................................... 75 Complete model .................................................................................................................................... 78 3.3 Corrections and modifications to calibrate the cycle in design mode ....................................................... 79 3.3.1 Suction loss ........................................................................................................................................... 79 3.3.2 Pressure and energy losses ................................................................................................................... 79 3.3.3 Isentropic efficiency of steam turbine .................................................................................................. 80 3.3.4 Dimensions of steam turbine ................................................................................................................ 81 3.3.5 Choice of evaporating pressure. ........................................................................................................... 81 3.3.6 Changes made to the Gas Turbine curves ............................................................................................. 81 3.3.7 Further modifications ........................................................................................................................... 82 3.4 Results after corrective actions ..................................................................................................................... 82 4 MATHEMATICAL MODEL OF LUBLIN-WROTKÓW POWER PLANT (COMBINED CYCLE) BY USING GATECYCLE SOFTWARE ............................................................... 86 4.1 Modeling the off-design operation ................................................................................................................ 86 4.1.1 How an off-design case works .............................................................................................................. 86 4.1.2 70% gas turbine load in winter configuration (T amb=0,9 °C) ................................................................ 86 4.1.3 100% gas turbine load in summer configuration (T amb=14 °C) ............................................................ 87 4.1.4 70% gas turbine load in summer configuration (T amb=14 °C) .............................................................. 88 4.2 Gas turbine analysis....................................................................................................................................... 89 4.2.1 Performances of V94.2 in the six cases considered .............................................................................. 90 4.2.2 Correction factors analysis ................................................................................................................... 91 4.2.3 Evaluation of Gas Turbine modeling .................................................................................................... 95 4.3 Steam cycles analysis ..................................................................................................................................... 95 4.3.1 Evaluation ............................................................................................................................................. 97 4.4 Combined cycles analysis .............................................................................................................................. 97 3 4.4.1 Evaluation ............................................................................................................................................. 99 5 CONCLUSIONS ........................................................................................................ 100 5.1 Final evaluation ............................................................................................................................................ 100 5.2 GateCycle evaluation ................................................................................................................................... 101 APPENDIX ...................................................................................................................... 102 BIBLIOGRAPHY & REFERENCES ................................................................................ 108 4 RESEARCH MOTIVATIONS From the beginning of my academic path, I have always been interested in studying Power Plants and, specifically, Gas Turbines and Combined Cycle. Hence, when my supervisor at Warsaw University of Technology suggested to me to develop a mathematical model of a combined cycle, I did not hesitate to accept. Considering my past experience, this proposal involved a completely new task for me, something which I had never done before, so I was keen on expanding my understanding in this field. One of the most stimulating aspects of this work has been the application of my theoretical knowledge to a real process. In this respect, the visits organized by the IHE Department to the plants of Starachowice and Siedlce have been extremely useful to see in reality most of what I learnt during my academic studies. Furthermore, my ability in using the software GateCycle and, generally, the skill of modeling a power plant, which I developed thanks to the present research, could help me in my future career. The choice of writing my final dissertation in a foreign country as an exchange student originates from different reasons. I have always thought that such an experience could have enriched myself both at a professional and personal level. On the one hand, it allowed me to improve my English and to develop a project autonomously. On the other, my staying in Warsaw has been a good occasion to grow up, start to be independent and meet people from other nationalities and cultures. In conclusion, I would like to thank those ones who helped me in the development of my work. I strongly thank my Italian supervisors Prof. Paolo Chiesa and Ing. Matteo Romano, my supervisor at WUT Dr. Jarosław Milewski and all the people working at the IHE division (Prof. Miller, Prof. Badyda, Łukasz, Marcin). I also thank my family, my Italian friends (C., D., F., F., G., L., M., N., R., S., S.), my university classmates (C., G., G., L., M. N., N., S., T.) who supported me in the choice to go abroad, and my friends in Warsaw (A., A., B., J., J., K., M., M., N.), who made my Polish experience unforgettable. (Some special thanks go to Marco, Nima and Rafa, who helped me with some language advice and to Filo and Linda, who taught me the bases of CAD drawing). Finally, I hope that my work will be useful for someone else, who will be interested in conducting further research in this sector. 5 6 1 INTRODUCTION Technologies of electricity production are many and various but they can be classified in two big branches: the ones which utilize renewable font of energy (as wind, water, solar radiation) and the one which utilizes non-renewable font of energy (coal, natural gas, oil, nuclear). These lasts are the most popular and they convert the chemical energy of the fuel in electric energy by using thermodynamics cycles. According to International Energy Agency, in 2008 more than 65% of electric energy has been generated by entailing fossil fuels with a strong part from coal. PRODUCTION FROM Coal Oil Gas Biomass Waste Nuclear Hydro Geothermal Solar PV Solar thermal Wind Tide Other sources ELECTRICITY PRODUCTION PERCENTAGE (GWh) 8262523 40,781% 1111311 5,485% 4300963 21,228% 197756 0,976% 69327 0,342% 2730823 13,478% 3287554 16,226% 64608 0,319% 12016 0,059% 898 0,004% 218504 1,078% 546 0,003% 4009 0,020% TOTAL 20260838 Table 1. World Electricity Production in 2008. [from International Energy Agency web site] 7 World Electricity Production by source Wind Solar thermal Tide Solar PV Other sources Geothermal Hydro Coal Nuclear Waste Biomass Gas Oil Picture 1. World electricity production by source. Gas Turbine Combined Cycle technology is almost present in every modern country from USA to Asia passing all over the Europe. Focusing on this last, one of the country which decided to invest on GTCC is Italy, especially with the “repowering” of many old oil power plants (substitution of the boiler by a gas turbine keeping the steam part for the bottoming cycle). A combined cycle is the result of coupling a Bryton cycle and a Rankine cycle. The first cycle is called “topping” and it works at high temperature by using a gas turbine. The heat of the exhaust gas is transferred to the steam cycle by an HRSG (Heat Recovery Steam Generator). The second cycle is called “bottoming” because it receives the residual heat coming from gas turbine and it works at lower temperature by using a steam turbine. This technology guarantees efficiency of 50÷55% on LHV of fuel which is higher in comparison to the other technologies of electricity production. Furthermore, combined cycles systems have a good flexibility of operating due to the possibility of burning different kinds of fuels (natural gas, coal syngas, residual oil fuels) and they can be used for both baseload and mid-range duty. They are characterized by a low environmental impact because they are fed by clean fuels (in most of the cases natural gas, no sulfur) and the combustion takes place with a big excess of air (no presence of unburned fuel). The installation of the plant takes less time than a conventional steam plant because the majority of the components are manufactured and packed in the factory and only the assembly is made at the operating site. Poland has not so many combined cycle plant and the power of the operative ones is not so high in comparison to the biggest GTCC power plants which reach thousands of MW, but they are often linked with district heating stations fed by coal. Most of the GTCC plants is quite new (less than 10 years) and they are located in the same places of the district heating plants. 8 The following section will provide an overall view of the most important GTCC technology power plants which are operative nowadays in Poland, presenting the main technical data and specific features for each plant. The following plant are described: 1. Elektrociepłownia Gorzów 2. Elektrociepłownia Lublin-Wrotków 3. Elektrociepłownia Nowa Sarzyna 4. Elektrociepłownia Rzeszów 5. Elektrociepłownia Zielona Góra GORZÓW Start operating year Electric power (MW) Net electric efficiency (%) Thermal power (MW) Table 2. 1.1 1999 94 300 LUBLINNOWA ZIELONA WROTKÓ SARZYNA RZESZÓW GÓRA W 2002 2000 2002 2004 235 115 101 221 48,28 49,04 592 332 322 Main characteristics of the power plants. Elektrociepłownia Gorzów Picture 2. Location of Gorzów CHP plant. “Gorzów” Heat and Power Station is a heating and power plant based on GTCC technology. The plant is located in Gorzow Wielkopolski in western Poland, approximately 50 kilometers from the border with Germany. In 1996 ABB Zamech Ltd, received the order to convert the existing coal power plant into a modern combined cycle and supplied a 55-megawatt type GT8C gas turboset, the associated heat recovery steam generator, the overall plant control system and various electrical infrastructure 9 equipment. Presently the power plants produces electricity and heat (both steam and hot water) based on fuel (natural gas) supplied by local resources. The Electric power reached is 94 MW and the Thermal power available is 300 MW and in addiction this plants produces raw and decarbonized water provided to local recipients. According to the 2007 rapport (the last available on PGE’s website) the plant produced 678 708 MWh of electric energy (gross) and 1 846 235 GJ of heat in that year. 1.1.1 Technical features UNIT 1 (ECI) Gas-Steam block Gas turbine type GT8C with the power output of 54,5 MW. 12-stage axial compressor. Silo type combustor. 3-stage turbine. Waste-heat boiler with the power output of 112,5 MWt. The Thermal-Electric Power Station I co-operating with the gas-steam block: Non condensing DDM – 55 type with the reachable power of 5 MW. Pass-out non condensing 3P6-6 type with the reachable power of 6 MW. UNIT 2 (ECII) Thermal-Electric Power Station II Two steam boilers type OP-140 with the reachable power of 98,4 MWt each. Pass-out non condensing type TC 32 steam turbine with the reachable power of 32 MW. One water boiler WP-70 with the reachable of 81,4 MWt. In 2007 the most important investment has been the installation of an electro-filter for the OP140 No. K-101 boiler and other upgrades in the steam system, electrical system and control system for a total amount of 9660 thousand zloty ( about 2.4 M€). 1.1.2 New summer configuration In 2008 a new configuration of operating in the summer period has been applied with very good results: the two steam turbine (T4, T5) integrated with the combined cycle had been switched off and replaced by the more efficient pass-out and condensing turbine (T6) which was integrated with the coal fired boilers. This project increased the net efficiency of the plant (especially in the summer period) and at the same time decreased CO2 emissions. PARAMETER Electricity generation efficiency Chemical energy consumption per MWh el Electricity production CO2 emission OLD NEW CONFIGURATIO CONFIGURATIO N N 0,379 0,423 COAL FIREL BOILER SHUTTING DOWN Fuel chemical energy saved Avoided CO2 emission Total avoided CO2 emission 10 9,50 GJ/MWh 8,51 GJ/MWh 144515 MWh 75509 ton 144515 MWh 67640 ton - 189634 GJ 7869 ton 26832 ton Table 3. 1.2 Comparison between the two different working configuration. Elektrociepłownia Lublin-Wrotków Picture 3. Location of Lublin-Wrotków CHP plant. Lublin-Wrotków CHP plant is the perfect demonstration of the present state and the evolution of polish CHP market. The history of the Lublin-Wrotków CHP plant goes back to 1973 when the decision about the construction of the new heat source fed by pulverized coal in City of Lublin was taken by the former Power Union. Due to economical trouble, it was decided to build only one section and provided it with large hot water boilers. The first (operating in 1976) had a thermal output of 81 MW. In the following years (1976-1985) one identical and two larger (140 MW) had been built for a total amount of 442 MW. In the middle of nineties was decided the expansion of the plant by a gas-steam unit and in 1997 the project for a turn-key project realization was shown: restructuring of the Lublin-Wrotków CHP plant and construction of the gas-steam unit. Civil works started in August 2000 and the gas turbine with generator was delivered in January 2001 whereas the waste-heat recovery boiler was delivered in March 2001 and the steam turbine was delivered in August of the same year. In January 2002 started the first synchronization of the generator with a capacity of 15 MW and the second one took place in March 2002 reaching the power of 20 MW. The test of the complete steam-gas unit started in March 2002 achieving the power of 210 MW and the group was ready for the trial run. 11 The present layout of the plant is constituted by: One steam-gas cogeneration unit: gas turbine set, waste heat recovery boiler and condensing steam turbine with a total thermal output of 150 MW and 236 MW of electric power. Two water boilers with total thermal capacity of 162 MW (81 MW each). Two water boilers with total thermal capacity of 280 MW (140 MW each). The total thermal power reaches 592 MW and the total electric power reaches 236 MW. The power island had been totally furnished by Ansaldo Energia (the entire structure had been manufactured in Genoa) and it is constituted of one V94.2 gas turbine (159 MW), one SCSF steam turbine (80 MW) and two air-cooled generators (WY21Z-097LLT linked to the gas turbine and WX18Z-066LLT linked to the steam turbine). The total amount of the restructuring was about 550,4 million PLN (137,6 million €). The quantity of coal decreased from 300000 ton/year to 70000 ton/year and at the same time the consumption of gas is 370000000 m3/year. 1.2.1 Technical features The V94.2 gas turbine is equipped by a 16-stage axial flow compressor and a 4-stage axial flow turbine. There are two combustors which has 8 burners each and they are set vertically on the side of the machine designed to work with natural gas and oil. WINTER (0.9 °C) 167,62 538,6 540,4 9,99 Net electric power (MW) Exhaust gas mass flow (kg/s) Exhaust gas temperature (°C) Fuel demand (kg/s) Table 4. SUMMER (14.0 °C) 155,52 517,2 546,2 9,43 Performance of the plant during winter season and summer season. The HRSG has two levels of pressure (LP, HP) and it has an horizontal disposition. The walls are made of steel sheet and isolated from the inside. The heating modules are hung up on a steel frame and there are collectors which permit dehydration and venting. The last drum increases the temperature of part of the district heating water. 12 WINTER (0.9 °C) PARAMETER 8,29 Mpa / 528 °C / 67,3 kg/s 0,60 Mpa / 219 °C / 14,2 kg/s 85,0 °C 538,6 0,8863 HP steam LP steam Exhaust gas temperature (°C) Exhaust gas mass flow (kg/s) Boiler efficiency Table 5. SUMMER (14.0 °C) 8,1 Mpa / 528 °C / 65,9 kg/s 0,59 Mpa / 219 °C / 13,5 kg/s 85,0 °C 517,2 0,8879 Features of the HRSG. The steam turbine is equipped with one HP part and one LP part and it has two extraction line, one direct to the deaerator (unregulated) and the other direct to the heat exchanger of the district heating water (regulated). PARAMETER Net electricity power (MW) Heat exchanger thermal power (MW) HP steam LP steam Unregulated extraction Regulated extraction Condenser thermal power (MW) Table 6. 71,55 SUMMER (14.0 °C) 76,62 131,93 23,37 7,99 Mpa / 525 °C / 67,3 kg/s 0,54 Mpa / 217 °C / 14,2 kg/s 0,27 Mpa / 143 °C / 2,2 kg/s 0,05 Mpa / 94 °C / 58,2 kg/s 46,5 7,82 Mpa / 525 °C / 65,9 kg/s 0,52 Mpa / 517 °C / 13,5 kg/s 0,26 Mpa / 144 °C / 2,9 kg/s 0,07 Mpa / 95 °C / 9,9 kg/s 143,0 WINTER (0.9 °C) Features of the steam turbine. All the boilers had been renovated by changing of the entire pressure circuits and installing low-emission burners in order to decrease NOx emissions. PARAMETER Construction year Nominal power (MW) Water temp. out of the boiler (C°) Water press. out of the boiler (MPa) Water mass flow (ton/h) Exhaust temperature out (°C) Guaranteed efficiency Table 7. WP-70 #1 1976 81 max. 165 WP-70 #2 WP-120 #3 WP-120 #4 1976 1979 1985 81 140 140 max. 165 max. 165 max. 165 max. 1,96 max. 1,96 max. 2,05 max. 2,05 1530 ± 5% 117 ÷ 132 0,84 1530 ± 5% 117 ÷ 132 0,84 2650 ± 5% 117 ÷ 146 0,84 2650 ± 5% 117 ÷ 146 0,84 Features of the boilers. 13 Picture 4. Simplified scheme of Lublin-Wrotków CHP plant. 14 1.3 Elektrociepłownia Nowa Sarzyna Picture 5. Location of Nowa Sarzyna CHP plant. Nowa Sarzyna CHP plant started commercial operation the 1st June 2000. The technology is a gas turbine combined cycle based on a GE Frame 6 gas turbine which reaches the electric power of 115MW. The electric energy is acquired by the Mercuria Energy Trading Sp. z o.o., the HP steam and LP steam by the chemical plant Zakłady Chemiczne „Organika-Sarzyna" S.A. and the hot water for the heating of Nowa Sarzyna by Zakład Gospodarki Komunalnej Nowa Sarzyna Sp. z o.o. PARAMETER Net electricity power (MW) Gas turbine Table 8. 115 GE Frame 6 Basic features of the plant. The average amount of NOx emission is 35 mg/Nm3 (the max level permitted is 75 mg/Nm). 15 1.4 Elektrociepłownia Rzeszów Picture 6. Location of Rzeszów CHP plant. The gas-steam unit of Rzeszów CHP plant was put into operation the 24 May 2003 and nowadays the layout of the plant is composed by two water boiler (WR-25, WP-120) plus the already quoted gas-steam unit (GSU-100). 1.4.1 Summer and winter configurations GSU-100 works as the basic load unit of the plant. During the summer period it is the only element which works and it covers completely the thermal demand (warm water) of Rzeszòw generating the necessary electricity at the same time. In the winter season the higher heat demand is supplied by the switching-on of the two additional boiler (peak generation working). GSU-100 gives the city the 65% of the entire thermal demand during the whole year and it produces almost all the needed electricity. 16 Picture 7. Operating conditions as the external temperature changes. [from official web site of Rzeszów power plant] PARAMETER Amount unit Electric power (MW) Thermal power (MW) Table 9. GAS AND STEAM WATER BOILER WATER BOILER UNIT (GSU-100) WR-25 WP-120 1 4 1 101 76,3 116 141 Performance of the different component parts. The total amount of thermal power is 332.3 MW and over 80% is destined to the Municipal Thermal Energy Company. All electric power, generated by gas and steam unit, is bought by PPGC Inc. (Polish Power Grid Company) and is almost all used to satisfy city’s requirements. PARAMETER Fuel demand (kg/s) Exhaust mass flow (kg/s) Net electric power (MW) Electric efficiency Fuel utilization index Table 10. HEATING SEASON 3,97 190,00 93,90 0,4851 0,8888 SUMMER SEASON 3,75 183,00 92,04 0,4989 0,6080 Gas turbine performances. Gas turbine is V64.3A geared with 17-stage axial-flow compressor, annular combustor with 24 low-emission hybrid burner and 4-stage axial flow-turbine. The air used in the cooling system is drawn from the compressor and then discharged into the exhaust air flow. The HRSG has two pressure levels and the steam generated, after passing through the steam turbine, is condensed in a close cooling water system with fans. The steam turbine use the bleeding-condensation system. Both turbine are linked with one electric generator reaching an electric efficiency level of 50% and a total efficiency of fuel energy of 89%. 17 1.5 Elektrociepłownia Zielona Góra Picture 8. Location of Zielona Góra CHP plant. Zielona Góra power plant had been commissioned in 1976 in order to satisfy the increasing request of heat from the town of Zielona Góra. The coal fired island has been completed between 1974 and 1986. It was composed by four boilers type OR and six boilers type WR-25. In 1976 the first backpressure steam turbine had been installed (O-PR 1915) and in 1996 the second one (VE 1932) with a capacity of 10,5 MW for the first and 12,87 for the second. The gas-steam island started to be built in August 2002 and it is fed by natural gas coming from the new gas-pipeline between Kościan and EC Zielona Góra (96 km), expressly projected to supply the plant. Commercial run took place in 2004 with an overall electric power of 221,4 MW and thermal power of 322 MW. 18 PARAMETER Electric power (MW) Thermal power (MW) Table 11. GASSTEAM UNIT 198 135 CARBON BLOCK TOTAL 23,4 187 221,4 322 Overall view of the power generated by the plant. In the heating season the hot water is generated both in the gas-steam unit and in the coal unit: the water coming from the district heating increases its temperature initially passing through two heat exchanger linked to the steam turbine of coal island, then passing through the heat exchanger linked to the steam turbine of the gas-steam island and if necessary in boilers WR-25. Coal boilers do not work except in the heating season and the maintenance periods of the gas-steam unit. 1.5.1 Technical features The gas turbine is a General Electric F9E class PG9171 type equipped with a 17-stage axial compressor, 14 burners radially arranged on the shell of the machine and a 3-stage axial turbine. PARAMETER Electricity power output (MW) Heat rate (kJ/kWh) Compression ratio Compression stage Turbine stage Exhaust gas mass flow (kg/s) Exhaust gas temperature (°C) Table 12. 126,1 10650 12,6 17 3 418 543 Basic technical data of the turbine PG917E (nominal terms). The HRSG is OU-292 produced by RAFAKO. It is an horizontal boiler characterized by 2 levels of pressure and natural circulation. 19 PARAMETER Max. sustainable vield (MW) HP steam mass flow (kg/s) HP steam pressure (bar) HP steam temperature (°C) LP steam mass flow (kg/s) LP steam pressure (bar) LP steam temperature (°C) Approach point ΔT (°C) Table 13. 202,4 53,3 75 505 10,4 7,1 213 8,9 Basic technical data of the HRSG OU-12 (design parameters). The steam turbine is an Alstom 7CK65 fed by two LP steam flows coming from coal boilers and one HP steam flow coming from the HRSG. It has two stages of condensing to heat up the water of the district heating. All the machine (including the electric generator) is supported by three bearings. PARAMETER Steam pressure from HRSG (bar) Steam temperature from HRSG (°C) Steam mass flow from HRSG (kg/s) Electric power (MW) Heat rate (kJ/kWh) Table 14. DISTRICT HEATING & CONDENSING CONFIGURATION 72 72 CONDENSING CONFIGURATION 505,55 505,55 52,79 53,31 64,2 11035 59,8 5454 Basic technical data of steam turbine 7CK65 in different operating conditions. The coal island is constituted by four boilers type OR-32 (equipped by a mechanical conveyor grate, natural circulation, two levels of steam superheating), six water boilers type WR-25 (equipped by a mechanical conveyor grate, maximum power 25 Gcal/h) and two steam turbines. PARAMETER Construction year Electric power (MW) Table 15. TG-1 (O-PR TG-2 (VE-32) 15.0) 1973 1995 10,5 18,87 Basic technical data of the coal block steam turbines. Nowadays turbine TG-1 is used only in case of emergency. The two heat exchanger exploit the steam coming from turbine TG-2: the first receives the steam at 0.2 MPa and the second at 0.5 MPa. They have vertical disposition. Since the gas-steam unit started to work, three boilers type WR-25 had been shot down. 20 Picture 9. Scheme of Zielona Góra CHP plant. 1.6 Summary The power plants analyzed in the previous paragraphs are all quite new. They had been built in the same area where there were already district heating plants and sometime they had been integrated with them. All the plants produce both electric power and heating power. Picture 10. Global map of the GTCC plants in Poland. GORZÓW LUBLINNOWA ZIELONA WROTKÓ SARZYNA RZESZÓW GÓRA W 21 Electric power (MW) Net electric efficiency (%) Thermal power (MW) Number of working GT Number of working ST Number of working boilers Table 16. 94 300 1 3 235 48,28 592 1 1 115 1 - 101 49,04 332 1 1 221 322 1 3 3 4 - 5 7 Summarizing table about the power plants. 22 2 THEORY The following chapter will provide a short introduction about the theoretical principles which are the bases on where the software works. 2.1 Thermodynamic cycles In this section it is possible to find a brief analysis focused on the ideal thermodynamic cycles on which a combined cycle is structured. 2.1.1 Carnot cycle The Carnot cycle is composed by four reversible transformations: (1-2) isotherm expansion, (23) adiabatic expansion, (3-4) isotherm compression, (4-1) adiabatic expansion. Picture 11. Carnot cycle. It is the highest efficiency cycle working between two temperatures (Tmax and Tmin) and the definition of the efficiency is: Tmin Tmax It is not possible to practically realize a Carnot cycle (it should need huge heat exchangers and very long time for the heat transfer), but it is used as reference for other ideal or real cycles (as in the following pictures) to see how they are efficient. 2.1.2 Brayton cycle The ideal Brayton cycle is an all-gas cycle composed by the following transformations: (1-2) adiabatic compression, (2-3) heat addition at constant pressure, (3-4) adiabatic expansion, (4-1) heat rejection at constant pressure. 23 Picture 12. Ideal Bryton cycle. The efficiency is defined in the following manner: Qout Q which written in function of the pressure ratio β = p2/p1 becomes: where k is the ratio between cp and cv (about 1,4 for air). Considering a cycle which works between two temperatures T3 and T1, it produces the maximum specific work for a particular value of pressure ratio which is: The temperature of the exhaust gas is higher than the outlet temperature from the compressor, so it is possible to heat the inlet air by using a particular heat exchanger called regenerator. This permits to save fuel and to increase the efficiency of the cycle because the temperature of the gas discharged into the atmosphere is lower. The regenerative configuration gives advantages for low values of pressure ratio and in little power cycles. This practice works only if the outlet temperature from the compressor is lower than the exhaust gas one and it has a proper efficiency defined in this way: Q Q The efficiency of the cycle becomes: 24 2.1.2.1 Advantages and disadvantages Advantages : Low environmental impact. Possibility of recover the heat from the exhaust gas. All-gas cycle (no changes of phase). Disadvantages: Use of expansive fuel. High enthalpy of the exhaust gas. A big part of the work is spent in the compression process. 2.1.3 Rankine cycle The ideal Rankine cycle is composed by the following transformations: (1-2) isentropic compression, (2-3) heat addition at constant pressure, (3-4) isentropic expansion, (4-1) heat rejection at constant pressure. It is possible to use different fluids but this section will refer to water Rankine cycle which is the most popular and the one utilized in combined cycles. Picture 13. Ideal water Rankine cycle. The cycle is characterized by changes of phase during the heat addiction (evaporation) and the heat rejection (condensation). Actually in most of the cases, heat addition is composed by three part: the increase of water temperature, the evaporation and the superheat. The efficiency is defined in the following way: Qout Q There is a great number of solutions to improve it. One is to diminish Tmin (decreasing condensing pressure) and to enhance Tmax (increasing temperature of superheating). Another one is to extract from the turbine a little fraction of the steam mass flow and put it in contact with the feed 25 water to increase the temperature of this latter. This practice takes place in some heat exchangers called regenerators and it allows to increase the average temperature of introduction of the heat. 2.1.3.1 Advantages and disadvantages Advantages : Use of every kind of fuel (external combustion). Use of water which is cheap and plentiful. Low energy spent to increase water pressure. Disadvantages: Tmax limited by the construction material (not more the 650 °C). A big part of the heat is spent for the evaporation of the water. 2.1.4 Combined cycle The real transformations of the two cycles are neither isentropic (machines are not ideal) nor isobar (pressure losses in the components), but for this section, which is only a brief introduction to the GTCC technology, it is sufficient to consider the ideal cycles. The bottoming steam cycle has the function of recovering the heat from the exhaust gas, which otherwise, in a simple cycle configuration, would be discharged into the atmosphere. Picture 14. Combined cycle schematic diagram. The efficiency of a combined cycle is defined in the following manner: Q 2.1.4.1 Advantages and disadvantages Advantages : High efficiency (50% or more). Combination of two well known technologies. Disadvantages: All the cycle depends on the Brayton cycle. Use of expansive fuel. 26 2.2 Heat Exchange (T-Q diagram) The Heat Recovery Steam Generator is the most typical component of combined cycle. It has three functions exploiting the remaining heat of exhaust gas: Increase water temperature in the economizer. Generate steam in the evaporator. Superheat the steam. The disposition of the two flows is upstream to recover the maximum heat from the exhaust gas. This short section will refer to the simplest configuration of an HRSG: one level of pressure. Other possible configurations depend on the mass flow and temperature of the exhaust gas, for example increasing levels of pressure (two or three) and introducing reheating sections. Picture 15. HRSG heat exchange diagram. There are three significant differences of temperature which characterize the heat exchange: Pinch-point ΔT: difference between the temperature of exhaust gas coming from evaporator and the evaporation temperature. Approach-point ΔT: difference between the temperature of exhaust gas coming from the gas turbine and the maximum temperature of the steam. Subcooling ΔT: difference between the evaporation temperature and the temperature of the steam coming from the economizer. Working on these parameters (and on the evaporation pressure) is possible to match the desired operating configuration of the steam cycle. 2.3 Steam and water calculation Four property methods are available to calculate steam and water properties in GateCycle. Method 1 is a tabular look-up procedure based on Keenan & Keyes – the maximum P is 2208 psia, maximum T is 2500 °F. Method 2 is the 1993 ASME steam property formulations - the maximum P is 14000 psia, maximum T is 1600 °F. This method is equivalent to the 1967 ASME steam property formulations with updated FORTRAN code and a few bug fixes. 27 Method 3 is based on a publication from Stanford (Thermodynamic Properties in SI Units , or TPSI) – the maximum P is 14000 psia, maximum T is 2500 °F. Method 4 is the newest standardized property method for steam and water: IAPWSIF97. This method is also known as the 1999 ASME steam tables. – the maximum P is 1000 bar with a maximum T of 2000 °C in the 1 to 100 bar pressure range and 800 °C in the 100 to 1000 bar range. Methods (2), (3) and (4) are the only GateCycle steam property methods that can be used to model supercritical steam cycles. Method (3) is probably the most stable; IAPWS-IF97 or TPSI are the most recommended steam property methods for all GateCycle models. 2.4 Chemical reaction of combustion One of the correct ways to calculate a chemical reaction is to consider that it will be completed when the equilibrium is reached. This means that there is a constant ratio between the reactants and the products and it is expressed by the equilibrium constant K. Considering a close control volume (T and P fixed), equilibrium is reached when Gibbs energy is minimum. where H is enthalpy, T is temperature and S is entropy. Analyzing a generic reaction between two products (A,B) and two reagents (C,D) K is defined in the following way where [A], [B], [C], [D] are the molar concentrations of the chemical species and a, b, c, d are the stoichiometric coefficients. It is important to remember that only species in either the gas or aqueous phases are included in this expression because the concentrations for liquids and solids cannot change. K is a characteristic of every reaction and it can be influenced by different parameters like pressure and temperature according to the kind of reaction. Other methods to calculate a chemical reaction are the following: Assume that there is a fix value of the conversion of reagents into products. Study it from the kinetic point of view and analyze the parameters which influence the reaction rate (pressure, temperature, catalyst). 2.4.1 GateCycle methods For gas flows, the calculations are performed for each individual constituent in a gas mixture (N2, O2, H2O, etc.) and then mixing laws are applied to determine the properties of the gas mixture. The method used for calculating the gas properties of the eleven gas constituents in GateCycle analysis (H2 O2 CHx CO CO2 N2 SO2 AR H2S COS H2O) is only one currently: "NASA Properties; Proposed PTC 4.4" uses NASA thermodynamic data for all constituents. This method is the proposed, but not yet accepted, 1998 ASME PTC 4.4 gas property method. Fuel flows are handled in a special manner. It is possible to specify the fuel used in GateCycle combustor, Gas Turbine, Gas Source and Duct Burner models by entering the Lower Heating Value of the fuel and the mass or volume percentages of the major constituents. Stoichiometric 28 calculations are used to determine the composition of combustor exit flows from the supplied fuel and air makeup (complete combustion is assumed). When a fuel flow uses the System Gas composition, the GateCycle application does allow for calculation of the CHx and LHV for the user based upon fuel constituents. There is also the possibility of an automatic calculation (based on the input composition) of the Lower Heating Value by the GateCycle application, instead of requiring this input from the user, according to the ASTM D3588-98 LHV method. 2.5 LHV and HHV Combustion is a chemical reaction between a fuel and a combustive agent which produces heat and its quantity is called Heating Value. The precise definition of LHV (Lower Heating Value) comes from the analysis of the enthalpy flows of the reagents which are involved in the combustion: the fuel, the combustive agent and the exhaust gas, taking them to a referring condition defined by a temperature (T0) and a pressure (P0). The water in the exhaust flow is considered as a gas. The Higher Heating Value definition is different from the previous one because the water of the combustion product is considered as a liquid. Its value is higher because also the condensing enthalpy is taken in consideration. GateCycle has a default value of LHV for natural gas of 47450,6252 kJ/kg, but it can calculate it starting from a user-defined composition. The allowed constituents of the fuel are the following: CONSTITUENT Hydrogen (H2) Oxygen (O2) Methane (CH4) Carbon Monoxide (CO) Carbon Dioxide (CO2) Nitrogen (N2) Sulfur Dioxide (SO2) Argon (Ar) Hydrogen Sulfide (H2S) Carbonyl Sulfide (COS) Steam (H2O) Ammonia (NH3) Methanol (CH3OH) Ethanol (C2H5OH) Propanol (C3H7OH) Hydrogen Cyanide (HCN) Methyl Mercaptane (CH4S) Ethane (C2H6) Propane (C3H8) n-Butane (C4H10) iso-Butane (C4H10) n-Pentane (C5H12) iso-Pentane (C5H12) 29 neo-Pentane (C5H12) n-Hexane (C6H14, gas) n-Heptane (C7H16, gas) n-Octane (C8H18, gas) Naphtalene (C10H8) DecaHydroNaphtalene (C10H18) Distillate (C12H26) Ethylene (C2H4) Acetylene (C2H2) Nitric Oxide (NO) Nitric Dioxide (NO2) Table 17. 2.6 Chemical spices allowed by the software to define a fuel. Pump A pump is a machine which increases the pressure of a liquid flow absorbing work from an external source. In case of using the pump curve to calculate the efficiency as a function of flow rate, it must be indicated whether this flow rate is a volumetric flow rate or a mass flow rate. Leaving the check-box, Use Volumetric Flow, un-checked indicates that the flow rate is a massflow rate. Similar to the equation used to model the head, a dimensionless equation is used. with The pump curve shape is symmetrical around the maximum efficiency. The shape of the curve can be influenced by changing the Flow Rate Coefficient Z. 2.7 Steam turbine A steam turbine is a machine which is able to convert the enthalpy of a steam flow into mechanical energy and to furnish it to an electric generator. The flow exchanges energy with the blades of the turbine, which puts in rotation the generator. GateCycle uses the GE Spencer, Cotton, and Cannon methodologies to automatically calculate the efficiency (Spencer, Cotton e Cannon 1974). The Spencer, Cotton, and Cannon methodology was developed to predict the design and normal part-load efficiency of large (16.5 MW and up) steam turbines for conventional fossil-plant operation. This methodology analyzes turbine performance section-by-section (HP, IP, and LP). These correlations were based on data gathered from heat rate tests on actual turbine units and experience gained from detailed stage-by-stage calculations. The result is a series of curves which can be used to calculate overall design-point performance of typical steam turbine designs. The methodology can also be used to predict the partload performance of a turbine operated with throttling control, or to predict the performance of a turbine operating with small changes in inlet conditions. The methodology has been incorporated into GateCycle and extended to enable it to be applied to general off-design operation. The efficiency expression for a steam turbine stage is the following: 30 2.8 Total efficiency of the system The net cycle power is the sum of the net steam cycle and gas turbine powers. The total fuel consumption includes all of the fuel consumed in gas turbines, duct burners, and gas sources, expressed in lower-heating value (LHV) since all fuel energy content in the GateCycle application is input in LHV. The net cycle heat rate is the total fuel consumption divided by the total power. The net efficiency is the inverse, expressed in percent. 2.9 Summary The chapter contains all the necessary definitions to read and understand the modeling section. The theory section can be useful in case of question about how the software makes its calculation and to know all the nomenclature used in the next section. 31 3 MODELING OF LUBLIN-WROTKÓW CHP POWER PLANT 3.1 Presentation of the work The modeling work of the whole plant is structured in the following way: the first component modeled is the gas turbine and, starting from this point, every other component is modeled following the layout connection of the plant. For instance the subsequent stage is Superheater n.3 and step by step every other linked element to represent the whole plant. The basic idea is to give every element an input data which is the output data obtained from the previous element trying to insert the minimum quantity of constriction in order to see how the software works. In case of lack of necessary data, it is possible to use those one included in the data paper furnished by WUT (Appendix). This paper contains a detailed layout of the plant and the main thermodynamic properties (Pressure, Temperature, Mass flow, Enthalpy) of every stream in every point of the plant. In case of problems, conflicts or errors generated by the software, some particular options are selected to give the software enough input parameters and/or additional hypotheses or assumptions which are formulated. Of course they are shown, explained and justified. At the end of every stage, a comparison of the most relevant parameters between the output data generated by GateCycle and the ones on the data paper are structured. In some cases, the changes caused by the addition of a new component to the whole plant model are analyzed. The pressure losses along the exhaust gas and water/steam lines have not been considered but the possible default values in every element of the software have not been changed. The HP steam line pressure value has been set at 82,000 bar (outlet from Superheater n.3). The LP steam line value has been set at 6,8856 bar (inlet of Supeheater n.1); and the exhaust gas line pressure value has been set at 1,0440 bar (outlet from gas turbine). However, these values are indicatives, because they will be calculated by the software when the model will be completed. The referring pressure on the data paper are the evaporation ones. In case of some splitting or extraction of mass flows, their value have been defined using the same proportion of the flows on the data paper. All the elements on the exhaust gas line had been configured by using the outlet temperature of the exhaust gas as a fix parameter, according to the value on the data paper. During the explanation of the modeling procedure, only the input operation into the software will be shown in detailed manner. As the rest of input data, it is necessary to consider the output data resulting from the previous steps. 3.1.1 Properties methods Steam Properties Method: 1993 ASME steam properties formulations (default). Gas Properties Method: NASA properties S. Grodon, B.J. McBride (default). 3.1.2 Data paper A data paper is a technical scheme of the plant in which the main thermodynamics properties of every flow are listed. It also includes the values of the electric and thermal powers generated for the chosen operating condition. Warsaw University of Technology provided about ten of these scheme (furnished by the power plant in the previous years), each one representing a specific working condition. The ones chosen to develop this work are the following. 100% gas turbine load in winter configuration (Tamb=0,9 °C) (Referring Case). 32 70% gas turbine load in winter configuration (Tamb=0,9 °C). 40% gas turbine load in winter configuration (Tamb=0,9 °C). 100% gas turbine load in summer configuration (Tamb=14 °C). 70% gas turbine load in summer configuration (Tamb=14 °C). 40% gas turbine load in summer configuration (Tamb=14 °C). The referring data paper is in the Appendix n.1. 3.2 Software analisys In the following sections, it will be possible to find every component modeled to obtain a complete model of the entire power plant. 3.2.1 Design point conditions Winter operating configuration is set as the design point characterized by gas turbine full load and maximum electric power generated by the whole plant. Design point conditions: External temperature: 0,9 ºC Gas turbine load: 100% Heat generated by gas turbine island: 150,00 MW Net electric power (gas turbine): 167,621 MW Net electric power (whole plant): 239,17 MW LHV Fuel: 48,82 MJ/kg Pressure loss through the GT: 0,010÷0,035 bar All these data are enumerated on the data paper. 3.2.2 Gas turbine V94.2 According to the scheme given by the WUT, the properties of Inlet Air, Fuel and Exhausted Gas are the following: PAPER DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) LHV (MJ/kg) Table 18. INLET AIR 1,0170 0,9 528,610 0,907 - FUEL 25 10,000 9,99 21,313 48,82 EXHAUST GAS 1,0440 540,400 538,600 588,425 - Properties of the gas turbine fluid flows. The gas turbine is modeled by using the following configuration option: Calculation Method → GT Curve Sets Select → Curve Table File Name Gas Turbine choosing the “V942” Curve Set (already present in the software database). The fuel stream has been modeled by selecting this input set: Fuel Type → User-specified Gas → Fuel LHV Method flag → User-defined LHV inserting the value 48820 kJ/kg. 33 Picture 16. GT Data Sets model in GateCycle and relatives streams. 34 INLET AIR INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) LHV (kJ/kg) OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) LHV (kJ/kg) VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) Table 19. EXHAUST GAS 1,017 0,9 528,610 - 25,000 10,000 9,990 48820 - 1,0170 0,9 532,563 -14,745 25,000 10,000 10,075 -11,356 48820,001 1,044 537,787 542,638 567,190 - + 0,000 + 0,792 + 0,000 + 0,958 + 0,000 + 0,456 + 0,794 Software data of the gas turbine fluid streams. PARAMETER GT shaft power (MW) Net GT power (MW) GT generator losses (MW) Efficiency on LHV (%) Table 20. FUEL 172,858 170,265 2,593 34,617 Power parameters generated by software calculation. First of all, it is important to consider that the enthalpy referring system is different between the data paper and the GE software, therefore the analysis cannot be focused on this parameter. According to the results obtained after the model run, it is possible to see that the values of pressure are unchanged. 3.2.2.1 Influence of fuel In order to study how the gas turbine works with different fuels, it is fed by two types of syngas. Syngas 1: diluted syngas from coal gasification. Syngas 2: syngas from coal gasification after CO2 capture. Ar CO CO2 H2 H2 O N2 Table 21. SYNGAS 1 SYNGAS 2 0,46% 0,51% 30,22% 1,10% 1,41% 2,26% 13,99% 48,02% 11,05% 15,32% 42,87% 32,79% Composition of the two syngas. 35 The option which links Heat Rate, Power, Exhaust Gas Mass Flow and Exhaust Gas Temperature must be checked in the curve editor, choosing the correction type Default(Built-in) Curve. The LHV is calculated automatically by GateCycle. GAS TURBINE Net electric power (MW) Net efficiency (%) NATURAL GAS 170,472 34,604 SYNGAS 1 SYNGAS 2 194,114 33,022 191,374 33,196 INLET AIR Pressure (bar) Temperature (°C) Mass flow (kg/s) 1,0170 0,9 532,547 1,0170 0,9 426,612 1,0170 0,9 472,895 FUEL Pressure (bar) Temperature (°C) Mass flow (kg/s) LHV (kJ/kg) 25,000 10,000 10,091 48820,001 25,000 10,000 116,026 5066,2059 25,000 10,000 69,743 8265,7619 EXHAUST GAS Pressure (bar) Temperature (°C) Mass flow (kg/s) 1,044 537,787 542,638 1,044 537,787 542,638 1,044 537,787 542,638 Table 22. Output data of V94.2 gas turbine for different kinds of fuel. The properties of exhaust gas are identical in every case, while the output power and the efficiency change value. This results is unusual, it seems that the software does not account of the different composition of the exhaust gas: keeping constant the pressure ratio (β) and changing γ=cp/cv (due to the different composition), the Temperature Outlet Turbine mast vary. Considering the Temperature Inlet Turbine (T3) constant in order to keep the same value of efficiency, the value of β is defined according the following equation, valid for an ideal cycle: For the rest of the calculation, the option selected before is unchecked because its influence is minimal. 3.2.3 Superheater n. 3 Starting from the output data given by GateCycle during the previous stage, it is now possible to model Superheater n.3. The main problem is that in the data paper there is no information about the inlet condition of the HP steam, but only the outlet flow data . The way of operation used is the following: Inlet steam pressure set as the same value of the outlet steam pressure of 82,000 bar. Inlet steam temperature found using directly the model. Defining the steam outlet temperature given by the data paper (528,000 ºC) as the goal of the model run, it is possible to run it and find the steam inlet temperature which gives a value of steam outlet temperature close to 528,000 ºC. The final value of the steam inlet temperature is 453,500 ºC giving an outlet steam temperature of 528,1228 ºC. 36 To give the software a sufficient number of parameters, Superheater Method Flag is set in this way: Calculation Mode → Superheater Method Flag → Gas Outlet Temperature → Desired Gas Outlet Temperature set at the value of 517,615 ºC (according to the data paper). Picture 17. Superheater n.3 model. INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) HP INLET INLET HP OUTLET OUTLET STEAM EXAUST GAS STEAM EXAUST GAS 82,000 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) VARIATION (%) Temperature (°C) Mass flow (kg/s) Table 23. 453,500 - - 517,615 67,392 - - - 82,000 1,044 82,000 1,044 453,499 537,787 528,123 517,615 67,392 3280,29 542,638 567,19 67,392 3464,94 542,638 544,03 - - +0,023 + 0,000 - - - - Software data concerning Superheater n.3. According to Table 23, the conditions calculated by using the software are very similar to the scheme data, so it can be said that the hypothesize value of the temperature of inlet steam is quite similar to the real one. This situation could be verified in the next model stage: if the model run 37 without problems and the obtained temperature (in the same point) is quite similar, the accuracy of this hypothesis will be demonstrated . 3.2.4 Pipeline n.1 In order to take into account the pressure losses between Superheater n.3 outlet and inlet of steam turbine, the pipeline is modeled by a specific icon of GateCycle. The way of calculation applied is to set a fractional value of the pressure losses, but it will be explained later. The properties of inlet HP steam are not modified. According to the data paper, these are the admission conditions of steam: PARAMETER Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) Table 24. ADMISSION STEAM 79,994 525,000 67,392 3459,50 Properties of the steam turbine admission flow. The options chosen to model the pipeline are the following: Calculation Mode → Pressure Change Method → Fractional Pressure Change inserting the value -0,02446%. This value is calculated by using the difference of pressures between the steam at the exit of Superheater n.3 and the steam at the entrance of throttle valve of the turbine. All this information is on the data paper. Calculation Mode → Temperature Control Method → No Enthalpy Change as an isenthalpic process (default). Picture 18. Pipeline n.1 model. OUTPUT DATA Pressure (bar) Temperature (°C) 79,994 527,237 38 67,392 3464,94 Mass flow (kg/s) Enthalpy (kJ/kg) VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) Table 25. + 0,000 + 0,426 + 0,000 Properties of the admission steam after the model run. As it is possible to see from Table 25, there are only minimal differences concerning temperature and specific enthalpy. 3.2.5 Steam Turbine n.1 Each of the five sections of the steam turbine is modeled by fixing two variables as input: the isentropic efficiency and the outlet pressure. The isentropic efficiency is calculated by using the Enthalpy-Entropy diagram for steam (Appendix). If the control valves are present in the plant layout, their number is also set. The properties of inlet steam are the same as the ones of the steam which comes from Pipeline n. 1 (output data from GateCycle) but no configuration is needed to set this option. The options set to configure Steam Turbine n.1 before running the software are the following: Calculation Mode → Number of Control Valves set at 1. Calculation Mode → Design Efficiency Method → Isentropic Expansion Efficiency inserting the value 0,7435. Calculation Mode → Inlet and Outlet Pressure Setting → Outlet Pressure inserting the value 50,033 bar (according to the data paper). Calculation Mode → Inlet and Outlet Pressure Setting → Design Pressure Method selecting Throttle Pressure Set Upstream (default). Picture 19. Steam Turbine n.1 model. 39 INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) OUTLET STEAM 50,033 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 50,033 465,680 67,392 3354,09 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) - 0,000 + 0,748 + 0,000 Table 26. Software data concerning Steam Turbine n.1. Changes concern only the temperature and the enthalpy of HP steam but the differences are lower than the 1% point. 3.2.6 Steam Turbine n.2 The properties of inlet HP steam are those of the steam which comes from Steam Turbine n.1 (output data from GateCycle) but no configuration is needed to set this option. No control valves are needed for this section. The options set to configure Steam Turbine n.2 before running the software are the following: Calculation Mode → Number of Control Valves set at 0 (default). Calculation Mode → Design Efficiency Method → Isentropic Expansion Efficiency inserting the value 0,8476. Calculation Mode → Inlet and Outlet Pressure Setting → Outlet Pressure inserting the value 5,514 bar (according to the data paper). Calculation Mode → Inlet and Outlet Pressure Setting → Design Pressure Method selecting Throttle Pressure Set Upstream (default). 40 Picture 20. Steam Turbine n.2 model. INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) OUTLET STEAM 5,5174 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 5,5174 212,059 67,392 2878,58 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 0,000 + 3,741 + 0,000 Table 27. Software data concerning Steam Turbine n.2. The most significant difference concerns the temperature of the steam (more than 3%). This is probably caused by how the isentropic efficiency is calculated. Using a precise method instead of graphic diagrams, it is possible to reach the real efficiency value. 3.2.7 Superheater n.2 Considering the exhaust gas line once again, Superheater n.2 is modeled. At the moment, the attemperation stream is not considered (very low mass flow) and it will be examined later. In this section of the work, a great deal of errors are generated by the software. One of the problems is that it is impossible to settle a layout with two superheaters at a stretch. However, this problem is solved by using a general heat exchanger icon instead of a superheater one. The model is run several times trying to insert the minimum quantity of input data, but it keeps on generating errors. The only successful configuration is the following: 41 Properties of Inlet HP steam defined according to the data paper. Data source → Calculation (flash) Method → Pressure-Enthalpy inserting the values 6,88561 bar and 2752,49 kJ/kg. The mass flow value inserted is 67,3921 kg/s. All these data are drawn from the data scheme. Superheater n.2 modeled as a “General Heat Exchanger” with gas exhaust as hot side and steam as cold side. Calculation Mode → Design Method → Hot Side Outlet Temperature → Desired Hot Side Outlet Temperature inserting the value 460,368 ºC (according to the data paper). Furthermore, hereafter is the most important option, set in order to let the software work and not to generate errors: Calculation Mode → Design Method → Demand Flow Method → Generate Cold Side Demand Flow. Other considerations regarding this last setting will be discussed after having shown the results of the run. Picture 21. Superheater n.2 model. INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) VARIATION (%) Temperature HP INLET STEAM INLET EXAUST GAS HP OUTLET STEAM OUTLET EXAUST GAS 82,000 - - - 299,210 - 453,500 460,368 67,392 - - - 82,000 1,044 82,000 1,044 299,210 517,615 453,499 460,368 68,715 2770,90 542,6375 544,03 68,7152 3280,29 542,6375 478,88 + 0,000 - - 0,000 + 0,000 42 (°C) Mass flow (kg/s) Table 28. + 1,963 - + 1,963 - Software data of the Superheater n.2 fluid flows. As Table 28 shows, the main difference concerns the steam mass flow. This is related to the last option set before running the model (“Generate Cold Side Demand Flow”): giving the software this new degree of freedom, it can calculate the necessary HP steam flow to reach the outlet temperature which has been set. This option will influence all the HP steam circuit. The hot side is linked to the gas turbine so it cannot be subjected to variations and this is the reason why only the HP steam mass flow changes. Consequently, the parameters of Superheater n.3 are affected. PARAMETER (SH3) Outlet exhaust gas temperature (°C) Outlet steam temperature (°C) Outlet steam specific enthalpy (kJ/kg) Table 29. BEFORE MODEL RUN AFTER MODEL RUN VARIATION (%) 517,615 517,615 + 0,000 528,123 526,656 - 0,278 3464,94 3461,38 + 0,103 Comparison of properties of Superheater n.3 steam before and after the model run. Only the steam side is influenced by the addition of Superheater n.2, while the exhaust gas side is not subjected to changes. However, the differences between the steam properties calculated in the previous steps and the ones calculated after Superheater n.2 addition are unimportant. 3.2.8 Evaporator n.2 During the modeling of Evaporator n.2, blowdown stream is not considered because its mass flow value is very small compared to the main water one (lower than 0,002%). The input conditions inserted in the software are the following. Evaporator’s configuration: Calculation Mode → Evaporator Method Flag → Steam Production without setting a value (it is generated automatically). This is the only option which allows the automatic generation of the steam flow. Inlet HP water configurations: Data source → Calculation (flash) Method → Pressure-Enthalpy with the values of 82,000 bar and 1391,46 kJ/kg. No specifications about the mass flow are needed. 43 Picture 22. Evaporator n.2 model. 44 INPUT DATA Pressure (bar) Mass flow (kg/s) Enthalpy (kJ/kg) HP INLET WATER INLET EXAUST GAS HP OUTLET STEAM OUTLET EXAUST GAS 82,000 1391,46 - - - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 82,000 1,044 82,000 1,044 296,697 460,368 296,697 307,217 66,8818 1391,46 542,6375 478,88 66,8818 2756,98 542,6375 308,88 VARIATION (%) Temperature (°C) Mass flow (kg/s) - 0,853 - - 0,853 + 0,374 - 0,004 - - 0,006 - Table 30. Software data of Evaporator n.2 fluid streams. The addition of Evaporator n.2 modifies the parameters of HP steam, and, consequently, the steam turbine performance. For instance, the steam outlet temperature of Superheater n.3 changes from 526,656 ºC to 528,697 ºC after the model run. The most important change concerns the HP steam mass flow, owing to the choice of generating it automatically. Its value can vary for every addition of new elements connected with this stream in order to match a working configuration. Table 31 lists the changes concerning the most relevant properties of HP steam. STEAM STREAM PARAMETER Steam turbine inlet pressure (bar) Steam turbine inlet temperature (°C) SH3 outlet temperature (°C) Mass flow (kg/s) Table 31. BEFORE MODEL RUN 79,9943 AFTER MODEL RUN 79,9943 VARIATION (%) + 0,000 525,765 527,813 + 0,389 526,656 68,7152 528,697 66,8818 + 0,388 - 2,668 Changes concerning the most relevant parameters of the steam stream. 3.2.9 Superheater n.1 Superheater n.1 is modeled in a very similar way as Superheater n.3. The inlet LP steam is defined in the following manner: Data source → Calculation (flash) Method → Pressure-Enthalpy inserting the values 6,88561 bar and 2761,29 kJ/kg. The mass flow value inserted is 13,6178 kg/s. All these data are drawn from the data scheme. The operating condition of the superheater is defined in the following way: Calculation Mode → Superheater Method Flag → Gas Outlet Temperature → Desired Gas Outlet Temperature inserting the value 305,324 ºC (according to the data paper). 45 Picture 23. Superheater n.1 model. INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) LP INLET INLET EXAUST STEAM GAS 6,8856 13,618 2761,29 - LP OUTLET STEAM OUTLET EXAUST GAS - 305,324 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 6,8856 164,293 13,619 2761,29 1,044 307,217 542,638 308,87 6,8856 199,020 13,619 2842,66 1,044 305,324 542,638 306,84 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 0,000 - - + 14,612 - 9,451 - + 0,000 - Table 32. Software data concerning Superheater n.1. As Table 32 shows, the main differences concern the outlet steam flow. 3.2.10 Pipeline n.2 Pipeline n.2 is modeled in the same way as the number.1. The fractional value of the pressure losses is calculated by using the same method. The properties of inlet HP steam are not modified. According to the data paper, these are the steam conditions before entering the mixer: PARAMETER Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) Table 33. LP STEAM FLOW 5,5174 217,793 13,618 2890,95 Properties of Pipeline n.2 flow. The options selected to model the pipeline are the following: 46 Calculation Mode → Pressure Change Method → Fractional Pressure Change inserting the value -0,0816129%. This value is calculated by using the difference of pressure between the pressure of the LP steam stream at the exit of Superheater n.1 and the pressure of LP steam stream before entering the mixer. All this information is on the data paper. Calculation Mode → Temperature Control Method → No Enthalpy Change as an isenthalpic process (default). Picture 24. Pipeline n.2 model. OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) LP STEAM FLOW 6,3237 197,614 13,619 2842,66 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 14,613 - 9,265 + 0.010 Table 34. Output data concerning Pipeline n.2 flow. The most relevant differences concern the pressure and the temperature of the steam stream. 3.2.11 Mixer n.2 The modeling of mixer n.2 is quite simple and quick. No input conditions are set and GateCycle does not generate errors. According to the data paper, these are the conditions of the outlet steam: PARAMETER Pressure (bar) Temperature (°C) Mass flow (kg/s) OUTLET STEAM 5,5174 206,651 81,010 47 2866,86 Enthalpy (kJ/kg) Table 35. Properties of the outlet stream. Picture 25. Mixer n.2 model. OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) OUTLET STEAM 5,5174 209,579 80,507 2873,22 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 0,000 + 1,417 - 1,176 Table 36. Output data concerning the outlet stream. The most relevant differences concern the temperature and the mass flow of the steam stream, but they are lower than 1,5%. 3.2.12 Economizer n.2 Economizer n.2 is modeled as a General Heat Exchanger because, trying to use the specific software icon (Economizer), a great deal of errors is generated. The configuration selected is the following: Economizer n.2 modeled as a “General Heat Exchanger” with gas exhaust stream as hot side and HP steam stream as cold side. Calculation Mode → Design Method → Hot Side Outlet Temperature → Desired Hot Side Outlet Temperature inserting the value 220,780 ºC (according to the data paper). Calculation Mode → Design Method → Second Design Method → No Second Method (default). Inlet stream configuration: Data source → Calculation (flash) Method → Pressure-Temperature inserting the values 82,000 bar and 124,283 ºC. The mass flow value is automatically generated. 48 Picture 26. Economizer n.2 model. INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) INLET WATER INLET EXAUST GAS OUTLET EXAUST GAS OUTLET WATER 82,000 154,283 - - - 220,780 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 82,000 154,283 66,888 655,35 1,044 305,324 542,638 306,83 82,000 296,697 66,888 1388,02 1,044 220,780 542,638 215,61 VARIATION (%) Temperature (°C) Mass flow (kg/s) + 0,000 - 0,003 - - 0,840 - 0,003 + 0,000 - Table 37. Software data concerning Economizer n.2. The results are very similar to the ones provided by the data paper, although the economizer is modeled by using the General Heat Exchanger icon. 3.2.13 Evaporator n.1 During the modeling of Evaporator n.1, blowdown stream in not considered because its mass flow value is unimportant compared to the main LP water one (lower than 0.010%). The input conditions inserted in the software are the following. Evaporator’s configuration: Calculation Mode → Evaporator Method Flag → Gas Outlet Temperature → Desired Outlet Gas Temperature inserting the value 172,523 ºC (according to the data paper). LP inlet water configuration: Data source → Calculation (flash) Method → Pressure-Enthalpy inserting the values 6,8856 bar and 726,959 kJ/kg (according to the data paper). 49 Picture 27. Evaporator n.1 model. INPUT DATA Pressure (bar) Mass flow (kg/s) Enthalpy (kJ/kg) LP INLET WATER INLET EXAUST GAS LP OUTLET STEAM OUTLET EXAUST GAS 6,8856 726,959 - - 172,523 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 6,8856 164,293 13,559 726,96 1,044 220,780 542,638 215,62 6,8856 164,293 13,559 2761,31 1,044 172,523 542,638 164,27 VARIATION (%) Temperature (°C) Mass flow (kg/s) + 0,000 - 0,439 - + 0,000 - 0,428 + 0,000 - Table 38. Software data concerning Evaporator n.1. The differences between the output data generated by the software and the paper ones are minimal (lower than 0,5%). The addiction of Evaporator n.1 modifies the parameters of LP steam flow but, as it is possible to see from Table 39, these variations are small. LP STEAM STREAM PARAMETER SH1 outlet temperature (°C) Mass flow (kg/s) Table 39. BEFORE MODEL RUN 191,275 13,619 AFTER VARIATION MODEL (%) RUN 191,404 + 0,007 13,559 - 0,441 Changes concerning the most relevant parameters of LP steam flow. 3.2.14 Economizer n.1 Economizer n.1 is modeled in a very particular way in order to represent the real element. This component is unique in the plant: it has two inlet water streams (one HP and one LP) in parallel disposition, so they come into contact with the exhaust gas flow at the same moment. 50 This element is modeled by using two different economizer icons (one for HP stream and one for LP stream), which are fed by two different exhaust gas flows resulting from the splitting of the main one. The mass flow of exhaust gas for each economizer is fractioned according to the quantity of heat exchanged by each water flow. The 79,8% supplies the HP stream and the 20,2% supplies the LP stream. In order to obtain a single outlet flow of exhaust gas, the two ones coming from the economizers converge into a mixer. The input configurations are the following. Mixer configuration: Primary Port Control Method → Specify Flow Fraction inserting the value 0,202. This port is connected to the LP economizer. Secondary Port Control Method → Remainder port. This port is connected to the HP economizer. LP economizer configuration: Calculation Mode → Economizer Modeling Method → Gas Outlet Temperature → Desired Gas Exit Temperature inserting the value 117,283 ºC (according to the data paper). HP economizer configuration: Calculation Mode → Economizer Modeling Method → Gas Outlet Temperature → Desired Gas Exit Temperature inserting the value 117,283 ºC (according to the data paper). Inlet LP water configuration: Data source → Calculation (flash) Method → Pressure-Temperature inserting the values 6,8856 bar and 64,1468 ºC (according to the data paper). The mass flow value will be automatically generated. HP inlet water configuration: Data source → Calculation (flash) Method → Pressure-Temperature inserting the values 82,000 bar and 65,000 ºC (according to the data paper). The mass flow value will be automatically generated. No configuration is needed for the mixer. Picture 28. Economizer n.1 model. INPUT DATA INLET LP WATER INLET HP WATER INLET OUTLET OUTLET OUTLET EXAUST LP HP EXAUST GAS WATER WATER GAS 51 Pressure (bar) Temperature (°C) Mass flow (kg/s) 6,8856 64,147 - 82,000 65,000 - - - - 117,283 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 6,8856 64,147 13,190 269,00 82,000 65,000 66,888 278,78 1,044 172,523 542,638 164,97 6,8856 158,737 13,190 670,04 82,000 153,501 66,888 651,99 1,044 119,112 542,638 107,97 VARIATION (%) Temperature (°C) Mass flow (kg/s) - - - - 3,382 - 3,139 - 0,826 + 0,003 + 1,552 - Table 40. Software data concerning Economizer n.1. As table.. shows, the main differences concern the LP steam stream and this influences all the heating line. For example, the outlet temperature of steam from SH3 passes from 191,4042 ºC (before the model run) to 184,7972 ºC. 3.2.15 Steam Turbine n.3 The model of Steam Turbine n.3 is similar to the previous ones. The only difference is the presence of one splitter which redirects part of the mass flow toward the deaerators. The amount of the redirected mass flow is calculated by keeping the same proportion between the flows on the data paper. The conditions of the inlet steam are the same as the ones of the flow which comes from Mixer n. 2 (output data from GateCycle), but no configuration is needed to set this option. The options to configure Steam Turbine n.3 before running the software are the following: Calculation Mode → Number of Control Valves set at 0 (default). Calculation Mode → Design Efficiency Method → Isentropic Expansion Efficiency inserting the value 0,8714. Calculation Mode → Inlet and Outlet Pressure Setting → Outlet Pressure inserting the value 2,66789 bar (according to the data paper). Calculation Mode → Inlet and Outlet Pressure Setting → Design Pressure Method select Throttle Pressure Set Upstream (default). Splitter’s configuration: Primary Port Control Method → Specify Flow Fraction → Primary Port Desired Flow inserting the value 0,9686 (according to the data paper). This port is connected to Steam Turbine n.4. Secondary Port Control Method → Remainder Port. This port is connected to Deaerator n.1. 52 Picture 29. Steam Turbine n.3 model. INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) MAIN OUTLET STEAM 2,66789 - DEAERATOR STEAM 2,66789 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 2,6679 141,851 77,556 2745,80 2,6679 141,851 2,516 2745,80 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 0,846 - 1,158 + 0,846 - 1,143 Table 41. Software data concerning Steam Turbine n.3. The output results are very similar to the ones on the data paper, only the values of the steam mass flow are different more than 1%. 3.2.16 Valve n.1 The only input condition is the value of fractional pressure drop set at 0,47799. This is calculated by using the upstream and downstream values of pressure provided by the data paper. No other options are set and the process is modeled as an isenthalpic one (default). These are the input options selected: Calculation Mode → Pressure Control Method → Pressure Drop → Desired Pressure Drop Flag → Desired Pressure Drop inserting the value 0,47799. The second configuration needed concerns the upstream splitter, because when the connection line is deleted to insert the valve, all the previously set inputs go lost. Secondary Port Control Method → Remainder Port. This port is connected to Deaerator n.1. 53 Picture 30. Valve n.1 model. INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Table 42. OUTLET STEAM - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 1,3927 136,399 2,516 2745,80 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) - 0,439 + 1,104 - 1,143 Software data of the steam flow after passing through Valve n.1. The properties of the steam flow are very similar to the ones on the data paper. The upstream splitter (n.4) is not considered because about 99,942% of the incoming flow from Valve n.1 goes into Dearator n.1. The remaining part (0,058%) is divided in turn in a heat exchanger and Deaerator n.2. The operating condition of Deaerator n.1 is defined in the following way: DA Method Flag → Vent Method Flag → 1-Constant Pressure: Vent Steam Flow for Energy Balance (default). The inlet water is configured in the following manner: Data source → Calculation (flash) Method → Pressure-Temperature inserting the values 1,21000 bar and 88,704 ºC. The mass flow value is 78,4651 kg/s. All these data are drawn from the data paper. 54 Picture 31. Deaerator n.1 model. 55 INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) INLET STEAM - INLET BWF OUTLET BWF WATER STEAM 1,21000 88,704 78,4651 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 1,3927 136,399 2,516 2745,80 1,2100 88,704 78,465 371,53 1,2100 105,048 80,803 440,38 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) - - + 0,000 + 0,000 - 1,721 Table 43. Software data concerning Deaerator n.1. The value of the mass flow is lower because the reinstatement flow coming from the depuration water area is not considered. This has a minimum influence on the energy balance of the whole power plant; in fact, the same amount of water is extracted from the main flow before arriving to the BWF pump section. 3.2.17 Heat Exchanger n.1 The model of heat exchanger n.1 includes also its bypass system. The choice of considering everything as a unique element does not create problems or errors. These are the options concerning the inlet water upstream from the bypass: Data source → Calculation (flash) Method → Pressure-Temperature inserting the values 1,26246 bar and 45,6471 ºC. The mass flow is 78,4649 kg/s. All these data are drawn from data paper. These are the options concerning the splitter in order to set the right values of mass flows: Primary Port Control Method → Remainder Port. This port is connected to the main stream. Secondary Port Control Method → Specify Flow Fraction→ Secondary Port Desired Fraction inserting the value 0,2142984 (calculated using the data paper). This port is connected to the bypass flow. No configuration is needed for both the heat exchanger and the mixer. 56 Picture 32. Heat exchanger n.1 model. FROM INPUT DATA CONDENSER Pressure (bar) 1,26246 Temperature (°C) 45,6471 Mass flow (kg/s) 78,4649 BYPASS WATER INLET HOT WATER - OUTLET HOT WATER - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) - 1,2625 45,647 16,815 191,16 1,2625 105,725 80,980 443,24 1,2625 64,208 80,980 268,80 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) - + 0,000 + 4,339 + 0,644 - 1,506 + 4,339 + 0,206 - 1,506 Table 44. Software data concerning Heat Exchanger n.1. The main differences concern the mass flow and the pressure. As previously said, the mass flow value is lower because the depurated water flow is not considered. The pressure value is higher because the pressure losses through heat exchanger n.1 and its bypass system are ignored. 3.2.18 Splitter n.2 Splitter n.2 has the function of dividing the water flow into two streams, one direct toward the HP pump, one direct toward the LP pump. The options set to configure it are the following: Primary Port Control Method → Remainder Port. This port is connected to the HP water stream. 57 Secondary Port Control Method → Specify Flow Fraction→ Secondary Port Desired Fraction inserting the value 0,168101 (calculated using data on the paper). This port is connected to the LP water stream. The inlet water is the one which gets out from heat exchanger n.1, but no input specifications are needed about this. Picture 33. Splitter n.2 model. 58 INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) HP WATER OUTLET STREAM LP WATER OUTLET STREAM - - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 1,2625 64,208 67,368 268,80 1,2625 64,208 13,613 268,80 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 4,339 + 0,206 - 0,046 + 4,339 + 0,206 - 0,046 Table 45. Software data concerning Splitter n.2. The output values of the mass flows are very similar to the data paper ones. The only variation concerns the pressure as already explained. 3.2.19 Pump n.1, Pump n.2 This modeling stage requires some particular expedients regarding some components because the LP and HP circuits have to be closed. This operation is critical from the point of view of mass balance. The first component added is Makeup n.1, which automatically calculates the necessary mass flow in order to conserve the mass balance. It needs only two inputs: pressure and temperature of its water stream. The value are set as the ones of the inlet flow from the condensers: Outlet pressure inserting the value 1,2625 bar (according to the data paper). Outlet temperature inserting the value 45,647 ºC (according to the data paper). Other changes concerning the already modeled components are listed below. Configuration of the splitter downstream of steam turbine n.3 (SP2): Primary Port Control Method → Remainder Port. This port is connected to steam turbine n.4. Secondary Port Control Method → Down Stream Flow Control. This port is connected to are Deaerator n.1. Deaerator n.1 configuration: DA Method Flag → 2-Constant Pressure: Demand Pegging Steam Flow → Pegging Steam Control Method → Control Main Steam Flow. The value of pressure is not inserted. Configuration of the flow coming from the condenser: The value of mass flow is deleted. Splitter n.2 configuration: Primary Port Control Method → Remainder Port. This port is connected to the main steam flow. Secondary Port Control Method → Down Stream Flow Control. This port is connected to Deaerator n.1. Pump n.1 configuration: 59 No configuration is needed, it calculates the outlet pressure automatically because it depends on the HP evaporator. Pump n.2 configuration: Calculation Mode → Pump Exit Pressure Method Flag → Pump Exit Pressure → Desired Pump Exit Pressure setting the value as 6,8856 bar (according to the data paper). Picture 34. Pumps n.1 and n.2. model. The analysis is focused only on the streams which enter or leave the whole system, but not on the inlet flows of gas turbine, which are fixed. 60 EXAUST GAS STEAM TO ST4 WATER FROM CONDENSER S - WATER FROM MAKEUP INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 1,044 119,424 542,638 108,29 2,668 141,743 77,565 2745,57 1,2625 45,647 0,000 191,158 1,2625 45,647 77,565 191,158 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 3,060 + 1,825 + 0,750 + 0,000 + 0,770 - 1,147 + 0,000 + 0,000 - + 0,000 + 0,000 - Table 46. 45,647 1,2625 - Software data of the most important flows after the addition of the two pumps. Makeup n.1 supplies all the necessary water mass flow but, when the whole circuit will be close, its mass flow will have a smaller value. Its presence is necessary for the mass balance of the plant because it gives the software a degree of freedom for calculations. The output data of the other fluid streams are similar to the data paper ones. The outlet pressure of the exhaust gas is higher because pressure losses on the exhaust gas line are not considered. 3.2.20 Steam Turbine n.4 The condition of the inlet steam are those of the outlet steam coming from the splitter of Steam Turbine n.3 (output data from GateCycle) but no configuration is needed to set this option. No control valve are needed for this section. The options chosen to configure Steam Turbine n.4 before running the software are the following: Calculation Mode → Number of Control Valves set to 0 (default). Calculation Mode → Design Efficiency Method → Isentropic Expansion Efficiency inserting the value 0,8826. Calculation Mode → Inlet and Outlet Pressure Setting → Outlet Pressure inserting the value 0,47814 bar (according to the data paper). Calculation Mode → Inlet and Outlet Pressure Setting → Design Pressure Method selecting Throttle Pressure Set Upstream (default). An ulterior configuration concerns the splitter of Steam Turbine n.3 because, when the connection line is deleted to add Steam Turbine n.4, all previously set input go lost. Primary Port Control Method → Remainder port. This port is connected to splitter n.3. 61 Picture 35. Steam Turbine n.4 model. INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) OUTLET STEAM 10,47814 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 0,47814 80,236 77,565 2498,09 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 0,000 + 0,000 - 1,147 Table 47. Software data concerning Steam Turbine n.4. The value are very similar except for the steam mass flow (the difference is more than 1%). 3.2.21 Splitter n.3 Splitter n.3 has the function of dividing the water flow in two streams, one direct toward Condenser n.1 pump, one direct toward Steam Turbine n.5. The options selected to configure it are the following: Primary Port Control Method → Remainder Port. This port is connected to Steam Turbine n.5. Secondary Port Control Method → Specify Flow Fraction → Secondary Port Desired Fraction inserting the value 0,7250 (according to the data paper). This port is connected to Condenser n.1. The properties of inlet steam are those of the steam which exits from Steam Turbine n.4 but no input specifications are needed. 62 Picture 36. Splitter n.3 model. INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) TO STEAM TURBINE N.5 TO CONDENSER N.1 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 0,4781 80,236 21,331 2498,09 0,4781 80,236 56,234 2498,09 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 0,000 + 0,000 - 1,147 + 0,000 +0,000 - 1,147 Table 48. Software data concerning Splitter n.3. The output value of the steam flows are very similar to the data paper one. Only difference concerning the mass flow is more the 1 point percentage. 3.2.22 Steam Turbine n.5 The conditions of the inlet steam are those of the outlet steam from Splitter n.3 (output data from GateCycle) but no configuration is needed to set this option. The options chosen to configure Steam Turbine n.5 before running the software are the following: Calculation Mode → Number of Control Valves set to 1 (according to the data paper). Calculation Mode → Design Efficiency Method → Isentropic Expansion Efficiency inserting the value 0,5530. Calculation Mode → Inlet and Outlet Pressure Setting → Outlet Pressure inserting the value 0,02594 bar (according to the data paper). Calculation Mode → Inlet and Outlet Pressure Setting → Design Pressure Method selecting Throttle Pressure Set Upstream (default). 63 Configuration of the splitter of Steam Turbine n.3 (SP2): Primary Port Control Method → Remainder Port. This port is connected to condenser n.1. Picture 37. Steam Turbine n.5 model. 64 INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) MAIN OUTLET STEAM 0,02594 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 0,02594 21,699 21,331 2289,56 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) - 0,006 - 1,147 Table 49. Software data concerning Steam Turbine n.5. The output results are very similar to the data paper ones except for the mass flow (the difference is more than 1%). 3.2.23 Condenser n. 1 Condenser icon needs two inputs to be modeled and this are the ones chosen: Calculation Mode → Condenser Modelling Method → Desired Pressure → Desired Exit Pressure inserting the value 0,2594 bar (the same of the steam incoming from steam turbine n.5). Calculation Mode → Cooling Water Method Flag → Fixed Cooling Water Temperature Rise → Desired Cooling Water Temperature Rise inserting the value 5,100 ºC (according to the data paper). The inlet cooling water is settled in the following manner: Data source → Calculation (flash) Method → Pressure-Temperature inserting the values 4,0000 bar and 12,000 ºC. The mass flow is generated automatically. All these data are drawn from the data paper. Steam turbine n.5 needs to be configured again: Calculation Mode → Inlet and Outlet Pressure Setting → Outlet Pressure inserting the value 0,02594 bar (according to the data paper). 65 Picture 38. Condenser n.1 model. 0,02594 - INLET COOLING WATER 4,0000 12,000 - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 0,0259 21,699 21,331 2289,56 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) - 0,006 - 1,147 INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) Table 50. INLET STEAM OUTLET COOLING WATER OUTLET WATER - - 4,0000 12,000 2197,865 50,76 0,0259 21,699 21,331 90,97 4,0000 17,098 2197,865 72,10 - 1,631 - - 10,314 - 0,008 - 1,631 Software data concerning Condenser n.1. There is a big difference (more than 10%) concerning the outlet pressure of cooling water. This is due to the fact of not have considered the pressure losses through the condenser. 3.2.24 Pipeline n.3 Pipeline n.3 is modeled in the same way as the others. The fraction value of the pressure losses is calculated using the same method. The properties of the inlet steam are not modified. According to the data paper, these are the steam conditions before entering Feedwater Heater n.1: PARAMETER Pressure (bar) INLET STEAM 0,43618 66 77,978 56,8868 2502,08 Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) Table 51. Properties of outlet stream from Pipeline n.3. The options chosen to model the pipeline are the following: Calculation Mode → Pressure Change Method → Fractional Pressure Change inserting the value -0,0877567. This value is calculated using the difference of pressures between the exit of Splitter n.3 and the entrance of Feedwater Heater n.1. All of these information is on the data paper. Calculation Mode → Temperature Control Method → No Enthalpy Change as an isenthalpic process (default). Picture 39. Pipeline n.3 model. 67 OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) INLET SECONDARY STEAM 0,4362 77,981 56,234 2498,09 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 0,023 + 0,004 - 1,147 Table 52. Output data concerning Pipeline n.3. The most relevant difference concerns the mass flow. Its value is about one point percentage as in the previous stages. 3.2.25 Temperature Control Mixer n.1 It is now possible to model the attemperation flow which had been missed out before. The splitter upstream Temperature Control Mixer n.1 (Splitter n.1) is added at the same time to let the software work in the correct way. These are the options concerning the splitter: Primary Port Control Method → Remainder Port. This port is connected to the main stream. Secondary Port Control Method → Down Stream Flow Control. This port is connected to the temperature control mixer. These are the options concerning the mixer: Temperature Control Method → Outlet Temperature → Desired Outlet Temperature inserting the value 453,500 ºC as explained in the previous stages. Picture 40. Temperature Control Mixer n.1 model. INPUT DATA INLET MAIN STREAM OUTLET MAIN STREAM 68 ATTEMPERATIO N STREAM Pressure (bar) Temperature (°C) Mass flow (kg/s) OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) Table 53. - - - - 453,500 - - - - 82,737 82,737 82,737 453,497 453,497 65,1205 66,888 3279,19 66,888 3279,19 0,000 279,35 Software data concerning Temperature Control Mixer n.1. No data concerning the outlet flow are on the data paper so it is not possible to make a comparison with the GateCycle ones. The properties of inlet flows are both defined in the previous stages. At the moment the mass flow value of attemperation stream is void but it will vary in the next stages. 3.2.26 Feedwater Heater n.1 Feedwater Heater n.1 icon needs two parameters to work in its design configuration. The first one is the terminal temperature difference (TTD): its value is hypothesized (5ºC ) because there is no information about the outlet flow from the feedwater heater. The second is the drain cooling approach temperature, which is calculated using the data paper. The temperatures to calculate the drain cooling approach are the ones downstream of pumps n.3 and n.4. Their value is very similar to the real one. The compression ratio is not high and the temperatures of the fluids is similar. Pressure losses through the feedwater heater are not considered. The feedwater heater operating condition is defined in the following way: Calculation Mode → Design Method → Terminal Temperature Difference → Desired Terminal Temperature Difference inserting the value 5,000 ºC. Calculation Mode → Use Drain Cooler → Drain Cooler Approach Temperature → Drain Cooler Approach inserting the value 2,6724 ºC. The inlet water is configured in the following manner: Data source → Calculation (flash) Method → Pressure-Temperature inserting the values 14,1359 bar and 52,1227 ºC. The mass flow is 1431,85 kg/s. All these data are drawn from the data scheme. 69 Picture 41. Feedwater Heater n.1 model. 70 INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) INLET FEEDWATE R INLET STEAM OUTLET WATER OUTLET FEEDWATE R - - 14,1359 52,1227 1431,85 - - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 0,4362 77,981 55,620 2498,05 14,1359 52,123 1431,850 219,33 0,4362 54,795 55,620 229,34 14,1359 72,981 1431,850 306,59 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 0,004 - 2,228 - - 2,228 - Table 54. Software data concerning Feedwater Heater n.1. In this section, only the values of mass flow are comparable. 3.2.27 Pump n.3, Pump n.4, Mixer n.3 The addition of these last elements coincides with the closure of the entire steam turbine circuit. The only setting concerns the mixer because the pumps regulate the outlet pressure according to the downstream element. In order to make the plant layout simpler, the makeup is connected directly to Mixer n.3 and the outlet stream of this latter goes toward Heat Exchanger n.1. The setting of Mixer n.3 is the following: Equalize Inlet Pressure → Equalize Inlet Pressure Method → Equalize Pressure to Minimum Inlet Pressure. Picture 42. Pump n.3, Pump n.4, Mixer n.3 model. 71 INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) FROM PUMP N.3 OUTLET WATER STREAM FROM PUMP N.4 - - - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 1,2625 21,706 21,928 91,11 1,2625 54,802 55,629 229,44 1,2625 45,448 77,556 190,33 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) + 0,000 + 0,876 + 1,619 + 0,000 + 0,012 - 2,212 + 0,000 - 0,436 - 1,158 Table 55. Software data concerning the two pumps and the mixer. The most important differences concern the mass flows while the other thermodynamics properties are very similar to the ones on the data paper. 3.2.28 Economizer n. 3 Economizer n.3 is the last element on the exhaust gas line. The configuration of the economizer is the following: Calculation Mode → Economizer Modeling Method → Gas Outlet Temperature → Desired Gas Exit Temperature inserting the value 85,000 ºC (according to the data paper). The configuration of inlet water is the following: Data source → Calculation (flash) Method → Pressure-Temperature inserting the values 13,5000 bar and 65,000 ºC (according to the data paper). The mass flow value is 168,856 kg/s. . 72 Picture 43. Economizer n.3 model. 73 INLET EXHAUST INPUT DATA GAS Pressure (bar) Temperature (°C) Mass flow (kg/s) - OUTLET EXAUST GAS INLET WATER OUTLET WATER 13,500 65,000 168,856 85,000 - - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 1,044 119,411 542,638 108,28 13,500 65,000 168,856 273,12 1,044 85,000 542,638 72,25 13,500 92,339 168,856 387,76 VARIATION (%) Temperature (°C) Mass flow (kg/s) + 1,814 - - + 0,000 - + 1,938 - Table 56. Software data concerning Economizer n.3. As Table 56 shows, the temperatures of water stream are higher (about 2%). 3.2.29 Exhaust Gas Conditioning System This section of the plant is composed of two valves, one mixer, one splitter and one pump. It is more significant to model all these elements together and see which are the consequences on the whole model. The valves are configured in the following way: V1: Calculation Mode → Pressure Control Method → Pressure Drop → Desired Pressure Drop (fractional) inserting the value 0,09273552. This value is calculated using the data paper. V2: Calculation Mode → Pressure Control Method → Pressure Drop → Desired Pressure Drop (fractional) inserting the value 0,0500000. This value is calculated using the data paper. Splitter n.6 is configured in the following way: Primary Port Control Method → Remainder Port. This port is connected to mixer n.4. Secondary Port Control Method → Specify Flow Fraction → Secondary Port Desired Fraction inserting the value 0,33364. This port is connected to valve V1. Pump n.5 is configured in the following way: Calculation Mode → Pump Exit Pressure Method Flag → Pump Exit Pressure → Desired Pump Exit Pressure inserting the value 13,5000 bar (according to the data paper). The inlet water is configured in the following way: Data source → Calculation (flash) Method → Pressure-Temperature inserting the values 14,1359 bar and 52,1227 ºC (according to the data paper). The mass flow is 112,519 kg/s. 74 Picture 44. Model of the Exhaust Gas Conditioning System. INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) PUMP N.5 INLET WATER OUTLET WATER - - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 12,8243 65,888 168,871 391,496 13,4991 93,117 112,519 276,783 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) - 0,005 + 1,366 + 0,009 - 0,007 + 2,918 + 0,000 Table 57. Software data concerning the Gas Exhaust Conditioning System. The temperature of the outlet stream, and consequently the enthalpy, is higher compared to the one provided by the data paper. This is due to the fact that the inlet temperature of exhaust gas coming from economizer n.3 is 119,411 ºC instead of 117,283 ºC (data paper). 3.2.30 Mixer n.4, Splitter n.5 The addition of these two elements leads the model to the closure of all the circuits belonging to the combined cycle island. These are the options concerning the splitter: Primary Port Control Method → Remainder Port. This port is connected to the feedwater heater. Secondary Port Control Method → Specify Flow Fraction → Secondary Port Desired Fraction setting the value as 0,07285754. This port is connected to Mixer n.5. 75 These are the options concerning the inlet water coming from the boiler island: Data source → Calculation (flash) Method → Pressure-Temperature with the values of 14,1359 bar and 52,1227 ºC. The mass flow set value is 1544.37 kg/s. All these data are drawn from the data paper. Picture 45. Mixer n.4 and Splitter n.5 model. 76 INPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) MIXER N.5 INLET SPLITTER N.6 OUTLET BOILER ISLAND INLET FWH N.1 OUTLET - - - - OUTPUT DATA Pressure (bar) Temperature (°C) Mass flow (kg/s) Enthalpy (kJ/kg) 14,1359 52,113 112,518 219,33 13,4991 93,228 112,518 391,50 14,1359 72,981 1431,852 306,59 13,4991 74,470 1544,370 312,77 VARIATION (%) Pressure (bar) Temperature (°C) Mass flow (kg/s) - 0,001 - 0,007 + 2,918 - 0,001 + 0,000 - 0,007 - 0,640 - Table 58. Software data concerning Mixer n.4 and Splitter n.5. The main differences concern the temperature and the enthalpy of the flow which passes through Economizer n.3 as already explained. 77 3.2.31 Complete model Picture 46. Complete model of Lublin-Wrotków power plant. DATA PAPER 78 GATECYCL E MODEL Net electric power (MW) GT net electric power (MW) ST net electric power (MW) Net cycle efficiency (%) STEAM PART HPevap (bar) LPevap (bar) Pcond (bar) HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) 239,166 167,621 71,545 49,038 241,188 170,265 70,923 49,037 84,977 6,886 0,026 66,879 13,618 82,737 6,880 0,026 66,888 13,190 GAS TURBINE Fuel mass flow (kg/s) 9,990 Inlet air mass flow (kg/s) 528,610 Temperature Outlet Turbine 540,400 (°C) Table 59. Final results of the design case. 3.3 10,075 532,563 537,787 Corrections and modifications to calibrate the cycle in design mode After having structured the entire cycle, some modifies are defined to make the model as similar as possible to the real plant. The operations concern: Introduction of a pressure loss in the suction section. Choice of a correct value of pressure and heat losses in every element of the HRSG. Choice of a more precise value of isentropic efficiency of steam turbine sections. Definition of some dimensional characteristics of the steam turbine by using some information furnished by the constructor (Ansaldo). Choice of the evaporating pressure in both circuits according to the data scheme. Editing of the Gate Cycle curves database of the V94.2 gas turbine. Other minor actions regarding other features of the cycle. In the following pages all the operations are explained in detailed manner, referring directly to the manual work made on the software . 3.3.1 Suction loss The chosen value of the suction loss is 1% of the ambient pressure (1,017 bar) and it is directly inserted as pressure of the inlet air by using the value: 1.017 – 1% = 1.007 bar. The inlet air is configured in the following way: Data source → Inputs → Pressure inserting the value 1.007 bar. 3.3.2 Pressure and energy losses Considering now the exhaust gas line and the steam lines, the fractional pressure losses (both gas and water/steam sides) are inserted in each heat exchanger and they are calculated referring to the values on the data paper. Superheater n.3 is configured in the following manner: 79 Losses → Hot side Pressure Drop Fraction Flag → Hot side pressure loss inserting the value 0,0048 (according to the data paper). Losses → Cold side Pressure Drop Fraction Flag → Cold side pressure loss inserting the value 0,0175 (according to the data paper). Losses → Energy Loss Fraction inserting the value 0,005. Superheater n.2 is configured in the following manner: Losses → Hot side Pressure Drop Fraction Flag → Hot side pressure loss inserting the value 0,0048 (according to the data paper). Losses → Cold side Pressure Drop Fraction Flag → Cold side pressure loss inserting the value 0,0175 (according to the data paper). Losses → Energy Loss Fraction inserting the value 0,005. Evaporator n.2 is configured in the following manner: Losses → Gas Pressure Drop Fraction Flag → Gas Pressure Drop inserting the value 0,0048 (according to the data paper). Losses → Energy Loss Fraction inserting the value 0,003. Superheater n.1 is configured in the following manner: Losses → Hot side Pressure Drop Fraction Flag → Hot side pressure loss inserting the value 0,0048 (according to the data paper). Losses → Cold side Pressure Drop Fraction Flag → Cold side pressure loss inserting the value 0,1274 (according to the data paper). Losses → Energy Loss Fraction inserting the value 0,003. Economizer n.2 is configured in the following manner: Losses → Hot side Pressure Drop Fraction Flag → Hot side pressure loss inserting the value 0,0048 (according to the data paper). Losses → Cold side Pressure Drop Fraction Flag → Cold side pressure loss inserting the value 0,0223 (according to the data paper). Losses → Energy Loss Fraction inserting the value 0,003. Evaporator n.1 is configured in the following manner: Losses → Gas Pressure Drop Fraction Flag → Gas Pressure Drop inserting the value 0,0048 (according to the data paper). Losses → Energy Loss Fraction inserting the value 0,003. Economizer n.1 (Low Pressure side) is configured in the following manner: Losses → Hot side Pressure Drop Fraction Flag → Hot side pressure loss inserting the value 0,001 (according to the data paper). Losses → Cold side Pressure Drop Fraction Flag → Cold side pressure loss inserting the value 0,123 (according to the data paper). Losses → Energy Loss Fraction inserting the value 0,003. Economizer n.1 (High Pressure side) is configured in the following manner: Losses → Hot side Pressure Drop Fraction Flag → Hot side pressure loss inserting the value 0,001 (according to the data paper). Losses → Cold side Pressure Drop Fraction Flag → Cold side pressure loss inserting the value 0,011 (according to the data paper). Losses → Energy Loss Fraction inserting the value 0,003. 3.3.3 Isentropic efficiency of steam turbine In order to represent better the steam machine, the isentropic efficiency are re-calculated with a Microsoft Excel macro called Xmollier (furnished by Energy Department of Politecnico di Milano) instead of the steam diagram (Appendix). This macro permits to calculate water and steam properties in a more precise way than before. 80 The precise values of the efficiency are listed in Table 60. Steam Turbine n.1 Steam Turbine n.2 Steam Turbine n.3 Steam Turbine n.4 Steam Turbine n.5 Table 60. PREVIOUS IS. EFFICIENCY RECALCULATE D IS. EFFICIENCY 0,7435 0,7326 0,8476 0,8617 0,8714 0,8588 0,8826 0,8513 0,5530 0,5410 Final results of the design case. 3.3.4 Dimensions of steam turbine Considering the steam machine, some dimensional data (furnished by Ansaldo) are inserted into GateCycle to increase the level of precision. Steam Turbine n.1: Calculation Mode → Number of Control Valves set to 1. Steam Turbine n.5: Calculation Mode → Condensing Section Flag → Exhaust Loss Calculation Method → Last Stage Bucket Length inserting the value 660,4 mm. Calculation Mode → Condensing Section Flag → Exhaust Loss Calculation Method → Last Exhaust Annulus Area inserting the value 3.49 m2. Calculation Mode → Number of Control Valves set to 1. 3.3.5 Choice of evaporating pressure. According to the data paper, the evaporating pressure is set by the user: Calculation Mode → Pressure Method Flag → Send Operating Pressure → Desired Operating Pressure inserting the value 84,9766 bar (HP circuit) and 6,886 bar (LP circuit). 3.3.6 Changes made to the Gas Turbine curves Investigating on the performances curve sets of the V94.2 present on the GateCycle database, it is found that the flag related to the partial load and the fuel LHV is not checked. The decision is of editing the original curve by using the specific feature of GateCycle and save it with the name “V942 mod”. Selecting the curve sets from the properties window of the gas turbine, this is the way of operating: Edit → Part Load Fraction → Heat Rate selecting the option Default(Built-in) Curve. Edit → Part Load Fraction → Exh. Flow selecting the option Default(Built-in) Curve. Edit → Part Load Fraction → Exhaust Temperature selecting the option Default(Builtin) Curve. In this manner, the software can use its default correlations (already present in the database) to run the part load cases. 81 Picture 47. Curve Set Editor window. The same work is done for the Fuel LHV section. 3.3.7 Further modifications Economizer n.1 Calculation Mode → Economizer Modeling Method → Exit Subcooling → Desired Exit Subcooling inserting the value 0,0 ºC (according to the data paper). GateCycle calculation General → Miscellaneous checking the flag “Ignore Compressor Power Requirement” Temperature Control Method → Outlet Temperature → Desired Outlet Temperature inserting the value 528,000 °C as explained in the previous stages. 3.4 Results after corrective actions This actions permit to obtain an appreciable result which is listed in Table 61. Net electric power (MW) GT net electric power (MW) ST net electric power (MW) Net cycle efficiency (%) STEAM PART HPevap (bar) LPevap (bar) BEFORE AFTER CORRECTIONS CORRECTIONS 241,188 238,897 170,265 167,795 70,923 71,102 49,037 49,010 82,737 6,880 82 84,877 6,886 DATA PAPER 239,166 167,621 71,545 49,038 84,977 6,886 Pcond (bar) HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) GAS TURBINE Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Temperature Outlet Turbine (°C) Table 61. 0,026 66,888 13,190 0,026 66,322 13,408 0,026 66,879 13,618 10,075 532,563 9,984 527,156 9,990 528,610 537,787 539,247 540,400 Comparison of the model performances before and after the corrective actions. Furthermore, Table 62 shows a point by point analysis of the HRSG, reporting a comparison of all the temperature and pressure values for each element. SH 3 Exh. Gas IN Exh. Gas OUT H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. 540,4 539,2468 -0,21% 1,044 1,044 517,615 517,615 0,00% 1,039 1,039 448,4997 83,4882 528,000 527,996 0,00% 82 82,0259 SH 2 Exh. Gas IN Exh. Gas OUT H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. 517,615 517,615 0,00% 1,039 1,039 460,368 460,368 0,00% 1,034 1,034 299,21 299,2114 0,00% 84,9766 84,9766 453,2926 83,4882 EVAP 2 Exh. Gas IN Exh. Gas OUT H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. 460,368 460,368 + 0,00% 1,034 1,034 308,37 308,37 + 0,00% 1,029 1,029 299,21 299,2109 + 0,00% 84,9766 84,9766 299,21 299,2114 + 0,00% 84,9766 84,9766 % 0,00% 0,00% 0,00% 0,00% SH 1 Exh. Gas IN Exh. Gas OUT H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. 308,37 308,37 + 0,00% 1,029 1,029 305,324 305,324 + 0,00% 1,02401 1,02401 164,293 164,2927 + 0,00% 6,88561 6,8856 219,793 220,2026 + 0,19% 6,00775 6,0084 % 0,00% 0,00% 0,00% 0,01% ECO 2 Exh. Gas IN Exh. Gas OUT H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. 305,324 305,324 0,00% 1,02401 1,02401 220,78 221,1605 0,17% 1,019 1,0192 154,283 154,5243 0,16% 86,9157 86,9142 299,21 299,2109 0,00% 84,9766 84,976 % 0,00% 0,02% 0,00% 0,00% EVAP 1 TEMPERATURE (°C) 83 PRESSURE (bar) % 0,00% 0,00% 0,03% % 0,00% 0,00% 0,00% Exh. Gas IN Exh. Gas OUT H2O IN H2O OUT DATA P. CALC. 220,78 221,1605 172,523 172,523 164,293 164,2915 164,293 164,2927 % DATA P. 0,17% 1,019 0,00% 1,014 0,00% 6,88561 0,00% 6,88561 CALC. 1,0192 1,0143 6,8856 6,8854 % 0,02% 0,03% 0,00% 0,00% ECO 1 (LP) Exh. Gas IN Exh. Gas OUT H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. 172,523 172,523 0,00% 1,014 1,0143 117,283 123,4388 5,25% 1,013 1,0133 64,1468 66,6094 3,84% 7,84922 7,8511 164,293 164,2915 0,00% 6,88561 6,8854 ECO 1 (HP) Exh. Gas IN Exh. Gas OUT H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. % 172,523 172,523 0,00% 1,014 1,0143 0,03% 117,283 117,283 0,00% 1,013 1,0133 0,03% 65 65,5327 0,82% 87,8853 87,8809 - 0,01% 154,283 154,5243 0,16% 86,9157 86,9142 0,00% Table 62. % 0,03% 0,03% 0,02% 0,00% Comparison of the model performances before and after the corrective actions. ST 1 H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. % 525,000 525,991 + 0,00 79,994 80,020 + 0,03 462,2222 464,169 + 0,42 50,032 50,033 + 0,00 ST 2 H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. % 462,2222 464,169 + 0,42 50,032 50,033 + 0,00 204,411 207,349 + 1,44 5,517 5,517 + 0,00 ST 3 H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. % 204,411 209,162 + 1,33 5,517 5,517 + 0,00 140,661 144,431 + 2,68 2,558 2,668 + 4,30 ST 4 H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. % 140,661 144,431 + 2,68 2,558 2,668 + 4,30 80,236 80,236 + 0,00 0,478 0,4781 + 0,00 ST 5 H2O IN H2O OUT TEMPERATURE (°C) PRESSURE (bar) DATA P. CALC. % DATA P. CALC. % 80,236 80,236 + 0,00 0,478 0,4781 + 0,00 21,700 21,699 - 0,01 0,026 0,026 - 0,15 Table 63. Comparison of the model performances before and after the corrective actions. 84 According to Table 62 the heat exchangers of HRSG are correctly modeled. The only relevant difference concerns the gas output temperature and the water inlet temperature of Economizer n.1 (LP). In the model of steam turbine there are differences about temperature and pressure. 85 4 MATHEMATICAL MODEL OF LUBLINWROTKÓW POWER PLANT (COMBINED CYCLE) BY USING GATECYCLE SOFTWARE The first section of the chapter explains how to configure an off-design case in GateCycle and lists the operations which the user made for each case. The second section is the analysis of results generated as output by the software. The analysis of results is developed in three sections: Single Gas turbine Steam cycles isolated Combined cycle model 4.1 Modeling the off-design operation In this paragraph the way of operating in off-design condition is explained referring to the specific features of GateCycle. 4.1.1 How an off-design case works The off-design case is directly connected with the design case (referring) and read the necessary data from it. Every icon switched into off-design configuration is linked with its corresponding icon in the design case and it conserves the original geometry. An off-design case permits to change some parameters (ambient conditions, load of the gas turbine, etc.) in order to see how the performances of the plant vary. GateCycle needs some help to obtain the convergence of calculation. According to the manual(Getting Started and Insallation Guide, GateCycle™ s.d.), there are four ways to obtain the convergence in an off-design case: Increasing the pressure in the evaporators and feedwater pumps to prevent boiling in economizers tubes. Bypassing economizers to prevent boiling. Varying mass flow specifications in splitters to satisfy deaeration and other steam requirements. Determining whether admission/extraction steam turbines are admitting or extracting and setting splitter and mixing flags to accomplish the model. The following pages list all the operation made by the user to configure the software properly. It is also important to underline to consider only the necessaries operations to be made for each of the three type of configuration (Gas turbine, Steam cycle, Combine cycle). 4.1.2 70% gas turbine load in winter configuration (Tamb=0,9 °C) The changes concerning this configuration are the following. Splitter n.5: Primary Port Control Method → Remainder Port. Secondary Port Control Method → Specify Flow → Secondary Port Desired Flow setting the value as 67,9176 kg/s. All this data are drawn from the data paper. Splitter n.6: 86 Primary Port Control Method → Remainder Port. Secondary Port Control Method → Specify Flow → Secondary Port Desired Flow setting the value as 32,9563 kg/s. All this data are drawn from the data paper. Steam Turbine n.1 (switched in design mode): Calculation Mode → Design Efficiency Method → Isentropic Expansion Efficiency inserting the value 0,740819 (according to the data paper). Calculation Mode → Inlet and Outlet Pressure Setting → Outlet Pressure inserting the value 39.8949 bar (according to the data paper). Calculation Mode → Inlet and Outlet Pressure Settings → Off-Design Pressure Method → Throttled: Pressure Set Upstream Steam Turbine n.5: Calculation Mode → Inlet and Outlet Pressure Setting → Outlet Pressure inserting the value 0,01883 bar (according to the data paper). Calculation Mode → Inlet and Outlet Pressure Settings → Off-Design Pressure Method → Throttled: Pressure Set Upstream Inlet cooling water of Condenser n.1: Mass flow value inserted is 1078,59 kg/s (according to the data paper). Temperature Control Mixer n.1: Temperature Control Method → Downstream SPTH Outlet Temperature → Desired Downstream Max T inserting the value 528,000 ºC (according to the data paper). Gas turbine V94.2: Calculation Method → Part Load Method → Specify Part Load Fraction → Desired Part Load Fraction inserting the value 0.7. Economizer n.2: Losses → Energy Loss Fraction inserting the value 0,001. Evaporator n.1: Calculation Mode → Pressure Method Flag → Send Operating Pressure → Desired Operating Pressure inserting the value 68,0122 bar. Evaporator n.2: Calculation Mode → Pressure Method Flag → Send Operating Pressure → Desired Operating Pressure inserting the value 5,52298 bar. Splitter n.3: Primary Port Control Method → Remainder Port. Secondary Port Control Method → Specify Flow Fraction → Secondary Port Desired Flow Fraction inserting the value 0,09147. 4.1.3 100% gas turbine load in summer configuration (Tamb=14 °C) The changes concerning this configuration are as following. Splitter n.5: Primary Port Control Method → Remainder Port. Secondary Port Control Method → Specify Flow → Secondary Port Desired Flow setting the value as 83,6585 kg/s. All this data are drawn from the data paper. Splitter n.6: Primary Port Control Method → Remainder Port. Secondary Port Control Method → Specify Flow → Secondary Port Desired Flow setting the value as 59,1402 kg/s. All this data are drawn from the data paper. Steam Turbine n.1: Calculation Mode → Inlet and Outlet Pressure Settings → Off-Design Pressure Method → Throttled: Pressure Set Upstream Steam Turbine n.5 (switched in design mode): 87 Calculation Mode → Design → Design Efficiency Method selecting Spencer Cotton Cannon Method. Calculation Mode → Inlet and Outlet Pressure Setting → Outlet Pressure inserting the value 0,08007 bar (according to the data paper). Inlet cooling water of Condenser n.1: Mass flow value inserted is 3351,54 kg/s (according to the data paper). Temperature value inserted is 22 °C (according to the data paper). Water coming from boilers island: Mass flow value inserted is 205,104 kg/s (according to the data paper). Pressure value inserted is 11,5046 bar (according to the data paper). Temperature value inserted is 45,0912 °C (according to the data paper). Inlet air of gas turbine: Temperature value inserted is 14 °C (according to the data paper). Gas turbine V94.2: Calculation Method → Part Load Method → Base Load. Pump n.5: Calculation Mode → Pump Exit Pressure Method Flag → Pump Exit Pressure → Desired Pump Exit Pressure setting the value as 11,500 bar (according to the data paper). Economizer n.2 (switched in design mode): Calculation Mode → Design Method → Effectiveness → Desired Effectiveness inserting the value 0,99. Losses → Energy Loss Fraction inserting the value 0,001. Evaporator n.1: Calculation Mode → Pressure Method Flag → Send Operating Pressure → Desired Operating Pressure inserting the value 6,83920 bar. Evaporator n.2: Calculation Mode → Pressure Method Flag → Send Operating Pressure → Desired Operating Pressure inserting the value 84,7266 bar. Splitter n.3: Primary Port Control Method → Remainder Port. Secondary Port Control Method → Specify Flow Fraction → Secondary Port Desired Flow Fraction inserting the value 0,2776. 4.1.4 70% gas turbine load in summer configuration (Tamb=14 °C) The changes concerning this configuration are the following. Splitter n.5: Primary Port Control Method → Remainder Port. Secondary Port Control Method → Specify Flow → Secondary Port Desired Flow setting the value as 49,9537 kg/s. All this data are drawn from the data paper. Splitter n.6: Primary Port Control Method → Remainder Port. Secondary Port Control Method → Specify Flow → Secondary Port Desired Flow setting the value as 34,4579 kg/s. All this data are drawn from the data paper. Steam Turbine n.1 (switched in design mode):: Calculation Mode → Design → Design Efficiency Method selecting Spencer Cotton Cannon Method. Steam Turbine n.5 (switched in design mode): Calculation Mode → Design → Design Efficiency Method selecting Spencer Cotton Cannon Method. 88 Calculation Mode → Inlet and Outlet Pressure Setting → Outlet Pressure inserting the value 0,06247 bar (according to the data paper). Inlet cooling water of Condenser n.1: Mass flow value inserted is 3340,15 kg/s (according to the data paper). Temperature value inserted is 22 °C (according to the data paper). Water coming from boilers island: Mass flow value inserted is 237,131 kg/s (according to the data paper). Pressure value inserted is 11,5109 bar (according to the data paper). Temperature value inserted is 45,0912 °C (according to the data paper). Inlet air of gas turbine: Temperature value inserted is 14 °C (according to the data paper). Gas turbine V94.2: Calculation Method → Part Load Method → Specify Part Load Fraction → Desired Part Load Fraction inserting the value 0.7. Pump n.5: Calculation Mode → Pump Exit Pressure Method Flag → Pump Exit Pressure → Desired Pump Exit Pressure setting the value as 11,500 bar (according to the data paper). Economizer n.2 (switched in design mode): Calculation Mode → Design Method → Effectiveness → Desired Effectiveness inserting the value 0,99. Evaporator n.1: Calculation Mode → Pressure Method Flag → Send Operating Pressure → Desired Operating Pressure inserting the value 5,54755 bar. Evaporator n.2: Calculation Mode → Pressure Method Flag → Send Operating Pressure → Desired Operating Pressure inserting the value 66,4791 bar. Splitter n.3: Primary Port Control Method → Remainder Port. Secondary Port Control Method → Specify Flow Fraction → Secondary Port Desired Flow Fraction inserting the value 0,3268. 4.2 Gas turbine analysis This paragraph is structured in two sections. The first one is a simulation of the six cases by using only the V94.2 gas turbine in order to see if the performances declared by Lublin-Wrotków power plant coincide with the ones calculated by Gatecycle. The second one is a comparative analysis between the official correction curves (furnished by Ansaldo) and the correspective ones built by using GateCycle.. The correction curves take in consideration the following parameters: Temperature of ambient air Inlet pressure loss (TAMB=15°C) Relative Humidity of ambient air (TAMB=15°C) Altitude (TAMB=15°C) The analysis is structured on the comparison between the Correction Factor declared and the Correction Factor calculated. If they are similar, it is possible to claim that the gas turbine is properly modeled by the software. Calling PFR the referential performance and PFX the generic performance, CF is defined in the following manner: 89 The referential data are highlighted with a blue line in the relative table and the CF value is obviously 1. In the appendix it is possible to find the CF table furnished by the constructor. 4.2.1 Performances of V94.2 in the six cases considered Table 64 summarizes the performances of the gas turbine for each case analyzed (3 winter cases, 3 summer cases). TAMB=0,9 °C / LOAD=100% GT net electric power (MW) Net cycle efficiency (%) Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) TAMB=0,9 °C / LOAD=70% GT net electric power (MW) Net cycle efficiency (%) Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) TAMB=0,9 °C / LOAD=40% GT net electric power (MW) Net cycle efficiency (%) Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) TAMB=14 °C / LOAD=100% GT net electric power (MW) Net cycle efficiency (%) Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) TAMB=14 °C / LOAD=70% GT net electric power (MW) Net cycle efficiency (%) Fuel mass flow (kg/s) Inlet air mass flow (kg/s) DATA GATECYCL VARIATION PAPER E CASE (%) 167,621 167,795 0,104% 34,369 34,424 0,159% 9,990 9,984 -0,059% 528,610 527,156 -0,275% 538,600 537,140 -0,271% 540,400 539,247 -0,213% 117,335 31,335 7,670 425,230 432,900 118,241 31,191 7,765 428,061 435,825 0,772% -0,462% 1,236% 0,666% 0,676% 540,400 537,646 -0,510% 67,048 26,209 5,240 372,860 378,100 67,726 25,901 5,358 370,866 376,224 1,011% -1,175% 2,248% -0,535% -0,496% 462,500 536,952 16,098% 155,518 9,430 507,770 517,200 155,955 33,877 9,429 507,512 516,941 0,281% 0,284% -0,007% -0,051% -0,050% 546,200 544,602 -0,293% 108,863 30,630 7,280 411,720 109,825 30,679 7,322 412,073 0,884% 0,160% 0,582% 0,086% 33,781 90 Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) TAMB=14 °C / LOAD=40% GT net electric power (MW) Net cycle efficiency (%) Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) Table 64. 419,000 419,406 0,097% 546,200 543,147 -0,559% 62,207 25,332 5,030 357,370 362,400 62,304 25,255 5,053 356,766 361,821 0,156% -0,306% 0,459% -0,169% -0,160% 477,700 544,895 14,066% Comparison of the GT performance output by Gatecycle and the ones on the data paper. 4.2.2 Correction factors analysis In the following sections the comparison between the CF declared and calculated is developed considering the change of some external parameter, as explained at the beginning of the paragraph. 4.2.2.1 Influence of ambient air temperature TAMB (°C) 0 10 15 20 30 40 LOAD GT OUTPUT CF CF DECLARED (%) POWER (MW) CALCULATED 100 170,303 1,100 1,087 100 161,025 1,030 1,028 100 156,685 1,000 1,000 100 151,641 0,970 0,968 100 142,154 0,905 0,907 100 131,755 0,840 0,841 VARIATION (%) -1,19% -0,22% 0,00% -0,23% 0,25% 0,11% 0 10 20 30 40 90 90 90 90 90 153,273 144,992 136,477 127,939 118,579 0,990 0,930 0,870 0,815 0,760 0,978 0,925 0,871 0,817 0,757 -1,19% -0,50% 0,12% 0,19% -0,42% 0 10 20 30 40 Peak Peak Peak Peak Peak 183,928 173,907 163,773 153,526 142,295 1,150 1,120 1,050 0,980 0,920 1,174 1,110 1,045 0,980 0,908 2,08% -0,90% -0,45% -0,02% -1,29% Table 65. TAMB (°C) LOAD (%) Comparison of the output power CFs varying TAMB. EFFICIENCY (%) CF DECLARED 91 CF CALCULATED VARIATION (%) 0 10 15 20 30 40 100 100 100 100 100 100 34,562 34,154 33,901 33,650 33,054 32,189 1,030 1,010 1,000 0,990 0,970 0,940 1,019 1,007 1,000 0,993 0,975 0,950 -1,02% -0,25% 0,00% 0,26% 0,52% 1,01% 0 10 20 30 40 90 90 90 90 90 33,885 33,484 32,990 32,406 31,558 1,015 0,995 0,975 0,950 0,925 1,000 0,988 0,973 0,956 0,931 -1,53% -0,73% -0,19% 0,62% 0,64% 0 10 20 30 40 Peak Peak Peak Peak Peak 35,268 34,851 34,336 33,728 32,846 1,035 1,020 1,000 0,980 0,955 1,040 1,028 1,013 0,995 0,969 0,51% 0,79% 1,28% 1,52% 1,45% Table 66. TAMB (°C) 0 10 15 20 30 40 LOAD (%) 100 100 100 100 100 100 Comparison of the efficiency CFs varying TAMB. 538,01 542,07 544,49 547,21 554,21 563,93 1,020 1,050 1,000 1,065 1,075 1,095 CF CALCULATED 0,988 0,996 1,000 1,005 1,018 1,036 TOT (°C) CF DECLARED VARIATION (%) -3,13% -5,18% 0,00% -5,63% -5,32% -5,41% 0 10 20 30 40 90 90 90 90 90 538,01 542,07 547,21 554,21 563,93 0,985 0,995 1,050 1,020 1,035 0,988 0,996 1,005 1,018 1,036 0,31% 0,06% -4,29% -0,21% 0,07% 0 10 20 30 40 Peak Peak Peak Peak Peak 538,01 542,07 547,21 554,21 563,93 1,020 1,050 1,065 1,075 1,095 0,988 0,996 1,005 1,018 1,036 -3,13% -5,18% -5,63% -5,32% -5,41% Table 67. TAMB (°C) LOAD (%) Comparison of the TOT CFs varying TAMB. EXH. MASS FLOW (kg/s) CF DECLARED 92 CF CALCULATED VARIATION (%) 0 10 15 20 30 40 100 100 100 100 100 100 541,98 526,42 518,64 508,96 489,59 465,74 1,050 1,015 1,000 0,980 0,945 0,905 1,045 1,015 1,000 0,981 0,944 0,898 -0,48% 0,00% 0,00% 0,14% -0,11% -0,77% 0 10 20 30 40 90 90 90 90 90 507,83 493,25 476,89 458,75 436,40 0,970 0,940 0,910 0,875 0,840 0,979 0,951 0,920 0,885 0,841 0,94% 1,18% 1,04% 1,09% 0,17% 0 10 20 30 40 Peak Peak Peak Peak Peak 569,29 552,95 534,61 514,27 489,21 1,050 1,015 0,980 0,945 0,905 1,098 1,066 1,031 0,992 0,943 4,54% 5,04% 5,18% 4,93% 4,23% Table 68. Comparison of the Exh Gas mass flow CFs varying TAMB. 4.2.2.2 Influence of inlet pressure losses Δp IN (bar) 0 0,005 0,010 0,015 0,020 0 0,005 0,010 0,015 0,020 LOAD GT OUTPUT CF CF DECLARED (%) POWER (MW) CALCULATED 100 156,385 1,000 1,000 100 155,137 0,993 0,992 100 151,431 0,985 0,968 100 150,196 0,977 0,960 100 148,961 0,969 0,953 EFFICIENCY (%) 100 33,901 1,000 1,000 100 33,812 0,998 0,997 100 33,550 0,990 0,990 100 33,463 0,985 0,987 100 33,377 0,980 0,985 VARIATION (%) 0,00% -0,05% -1,69% -1,70% -1,70% 0,00% -0,01% -0,04% 0,21% 0,46% TOT (°C) 0 0,005 0,010 0,015 0,020 100 100 100 100 100 0 0,005 0,010 100 100 100 544,49 545,23 547,42 548,14 548,87 EXH. MASS FLOW (kg/s) 518,64 515,97 508,06 93 1,000 1,001 1,003 1,005 1,006 1,000 1,001 1,005 1,007 1,008 0,00% 0,01% 0,22% 0,17% 0,20% 1,000 0,998 0,994 1,000 0,995 0,980 0,00% -0,27% -1,49% 0,015 0,020 100 100 505,43 502,79 0,985 0,980 0,975 0,969 -1,06% -1,08% Comparison of the performances CFs varying Δp IN. Table 69. 4.2.2.3 Influence of altitude Alt.(m) 0 300 600 900 1200 LOAD GT OUTPUT CF CF DECLARED (%) POWER (MW) CALCULATED 100 156,386 1,000 1,000 100 147,609 0,965 0,944 100 139,082 0,925 0,889 100 130,801 0,895 0,836 100 122,760 0,860 0,785 Table 70. VARIATION (%) 0,00% -2,19% -3,85% -6,55% -8,72% Comparison of the output power CFs varying the altitude. 4.2.2.4 Influence of Relative Humidity (Tamb=15°C) RH (%) 60 20 40 80 100 60 20 40 80 100 LOAD GT OUTPUT CF CF DECLARED (%) POWER (MW) CALCULATED 100 156,385 1,000 1,000 100 156,373 0,994 1,000 100 156,373 0,997 1,000 100 156,373 1,001 1,000 100 156,373 1,002 1,000 EFFICIENCY (%) 100 33,901 1,000 1,000 100 33,900 1,003 1,000 100 33,900 1,001 1,000 100 33,900 1,000 1,000 100 33,900 0,999 1,000 VARIATION (%) 0,00% 0,60% 0,29% -0,09% -0,17% 0,00% -0,26% -0,05% 0,05% 0,10% TOT (°C) 60 20 40 80 100 100 100 100 100 100 60 20 40 80 100 100 100 100 100 100 544,49 544,50 544,50 544,50 544,50 EXH. MASS FLOW (kg/s) 518,64 518,61 518,61 518,61 518,61 Table 71. 1,000 0,998 0,999 1,001 1,002 1,000 1,000 1,000 1,000 1,000 0,00% 0,20% 0,10% -0,10% -0,20% 1,000 1,002 1,001 0,999 0,998 1,000 1,000 1,000 1,000 1,000 0,00% -0,21% -0,11% 0,09% 0,19% Comparison of the performances CFs varying RH. 94 4.2.3 Evaluation of Gas Turbine modeling The GateCycle model works properly at full load and 70% load. The 40% model presents very high difference concerning the TOT in both winter and summer cases (about 70 °C higher). In order to verify if GateCycle calculates the TOT or reads its value in the data curve set, independently from the other parameters, a simplified energy balance of the gas turbine is developed. Picture 48. Simplified GT energy balance. The value of the energy losses calculated by using the output data of GateCycle is compared with the ordinary value of a generic gas turbine, which is about 2% or 3%. The energy balance has the following expression: The gives values of loss is negative. This results is the prove that GateCycle does not calculate the energy balance, but it just reads the curve set and shows the output data. Speaking about the full load and 70% load cases, the differences between the data paper performances and the calculated one are lower than 1%, except for the fuel mass flow in the winter 70% load case (+1,24%). Considering now the CF section, the influence of TAMB is properly model except for the TOT (relative difference around 5 % in all the simulations). The same situation appears for the exhaust gas mass flow during the peak load simulation. The change of inlet pressure loss and RH is correctly model in the considered cases, contrary to the altitude CF calculated by GateCycle which is not coherent with the declared data. 4.3 Steam cycles analysis The following paragraph contains four simulations concerning the steam cycle, two winter cases (100% and 70% load) and two summer cases (100% and 70% load). Each steam cycle is fed by a gas mass flow set with the same thermodynamics properties of the one on the data paper. The composition is defined by the user in the following way Nitrogen (N2) Oxygen (O2) Water (H2O) Carbon Dioxide (CO2) MASS COMPOSITION (%) 75,42 13,96 6,44 3,28 95 0,90 Argon (Ar) Table 72. Composition of the exhaust gas defined for the simulation. GateCycle is not able to reach convergence modeling the two 40 % load cases, so they are not considered. WINTER 100% ST net electric power (MW) HPevap (bar) LPevap (bar) Pcond (bar) HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) Table 73. Output data of the TAMB=0,9 °C, 100% load case. WINTER 70% ST net electric power (MW) HPevap (bar) LPevap (bar) Pcond (bar) HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) Table 74. DATA GATECYCL VARIATION PAPER E MODEL (%) 76,620 76,284 -0,439% 84,727 84,727 0,000% 6,839 6,839 0,003% 0,080 0,111 38,625% 62,998 64,978 3,143% 13,436 12,621 -6,067% Output data of the TAMB=14 °C, 100% load case. SUMMER 70% ST net electric power (MW) HPevap (bar) LPevap (bar) Pcond (bar) HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) Table 76. DATA GATECYCL VARIATION PAPER E MODEL (%) 52,938 50,036 -5,481% 68,012 68,015 0,005% 5,523 5,459 -1,168% 0,019 0,017 -9,474% 52,713 50,903 -3,433% 11,176 10,516 -5,906% Output data of the TAMB=0,9 °C, 70% load case. SUMMER 100% ST net electric power (MW) HPevap (bar) LPevap (bar) Pcond (bar) HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) Table 75. DATA GATECYCL VARIATION PAPER E MODEL (%) 71,545 71,962 0,582% 84,977 84,977 0,000% 6,886 6,885 -0,009% 0,026 0,026 -0,385% 66,879 65,501 -2,061% 13,618 13,287 -2,428% DATA GATECYCL VARIATION PAPER E MODEL (%) 61,842 58,798 -4,923% 66,479 66,479 0,000% 5,458 5,457 -0,003% 0,062 0,075 19,417% 49,682 50,813 2,276% 10,996 9,598 -12,711% Output data of the TAMB=14 °C, 70% load case. 96 4.3.1 Evaluation The output power of the two full load cases is close the data paper one, but as Tables 73 and 75 show the HP and LP steam mass flows are very different. Speaking about the 70% load cases, all the parameters taken in consideration for the analysis are far from the data declared by the plant, except for the HP and LP pressures (but they are set by the user). In both of the cases the output power is lower than about 5%. 4.4 Combined cycles analysis This paragraph analyzes the complete model of the combine cycle: one design (100 % load) case and three off-design cases: one winter simulation (70% load) and two summer simulations (100 % and 70 % load). The design cases is properly model as explained at the end of Chapter 3. GateCycle is not able to reach convergence modeling the two 40 % load cases, so they are not considered. WINTER 100% Net electric power (MW) GT net electric power (MW) ST net electric power (MW) Net cycle efficiency (%) STEAM PART HPevap (bar) LPevap (bar) Pcond (bar) HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) GAS TURBINE Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) Table 77. DATA GATECYCL VARIATION PAPER E MODEL (%) 239,166 238,897 -0,113% 167,621 167,795 0,104% 71,545 71,102 -0,620% 49,038 49,010 -0,056% 84,977 6,886 0,026 66,879 13,618 84,977 6,886 0,026 66,322 13,408 0,000% -0,006% -0,385% -0,832% -1,544% 9,990 528,610 538,600 9,984 527,156 537,140 -0,059% -0,275% -0,271% 539,247 -0,213% 540,400 Comparison of performances between the GateCycle model and the data paper ones. WINTER 70% Net electric power (MW) GT net electric power (MW) ST net electric power (MW) Net cycle efficiency (%) STEAM PART (Evaporators) HPevap (bar) LPevap (bar) Pcond (bar) DATA OFF-DESIGN VARIATION PAPER CASE (%) 170,273 170,974 0,412% 117,335 117,457 0,104% 52,938 53,517 1,095% 45,473 45,143 -0,727% 68,012 5,523 0,019 97 68,012 5,675 0,018 0,000% 2,745% -6,316% HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) GAS TURBINE Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) Table 78. 53,001 10,906 0,546% -2,420% 7,670 425,230 432,900 7,758 427,863 435,621 1,142% 0,619% 0,628% 540,400 539,247 -0,213% Comparison of performances between the GateCycle model and the data paper ones. SUMMER 100% Net electric power (MW) GT net electric power (MW) ST net electric power (MW) Net cycle efficiency (%) STEAM PART HPevap (bar) LPevap (bar) Pcond (bar) HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) GAS TURBINE Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) Table 79. 52,713 11,176 DATA OFF-DESIGN VARIATION PAPER CASE (%) 232,138 231,826 -0,135% 155,518 155,760 0,155% 76,620 76,066 -0,723% 50,4238 50,368 -0,111% 84,727 6,839 0,080 62,998 13,436 84,727 6,839 0,112 65,827 12,384 0,000% 0,004% 40,375% 4,491% -7,827% 9,430 507,770 517,200 9,427 507,460 516,887 -0,028% -0,061% -0,060% 544,895 -0,239% 546,200 Comparison of performances between the GateCycle model and the data paper ones. SUMMER 70% Net electric power (MW) GT net electric power (MW) ST net electric power (MW) Net cycle efficiency (%) STEAM PART HPevap (bar) LPevap (bar) Pcond (bar) HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) DATA OFF-DESIGN VARIATION PAPER CASE (%) 170,705 170,242 -0,271% 108,863 109,032 0,155% 61,8424 61,211 -1,022% 48,0306 47,604 -0,889% 66,479 5,456 0,062 49,682 10,996 98 66,478 5,458 0,080 53,675 9,575 -0,001% 0,001% 28,222% 8,037% -12,922% GAS TURBINE Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) Table 80. 7,280 411,720 419,000 7,325 411,870 419,196 0,620% 0,037% 0,047% 546,200 544,895 -0,239% Comparison of performances between the GateCycle model and the data paper ones. 4.4.1 Evaluation Global performances of all the cases are similar to the data paper ones: the maximum difference is around 1,1 % (ST electric power in the two 70 % load cases). In all the off-design cases the value of HP and LP mass flows are different: the HP steam mass flow is higher and, consequently and correctly, the LP one I lower. The value of relative variation regarding the condensing pressures is very high, but this is due to the fact the absolute value is small. There is no need to speak about the gas turbine because it has been already done in paragraph 4.2. 99 5 CONCLUSIONS The thesis work contains an introductive part concerning GTCC operative plants in Poland to present the current situation about this technology. Subsequently, a brief theory section which speaks about the ideal cycles, the properties calculation methods and the key components is developed. This chapter gives the reader the possibility of know the theoretical principles on which the software is built. The next one is the icon by icon setting up of the model in design configuration. It includes an analysis of the thermodynamic properties for every element of the plant, a comparison with its corresponding one on the technical data paper and conclusive section about the modifications made to calibrate the design case. Afterward, the study of the complete model in design and off-design configuration is presented. Investigation is composed by six cases: three in winter operating condition (Gas Turbine load: 100%, 70% and 40%) and three in summer operating condition (Gas Turbine load 100%, 70% and 40%). The chapter is composed by three sections: the first analyzes the gas turbine, the second analyzes the steam cycle and the third analyzes the combined cycle. The last chapter is a conclusive part with the comments about the obtained results and a final evaluation of the model and the software. 5.1 Final evaluation Summarizing all the developed work, it is useful to keep the same structure of Chapter 4 dividing the evaluation in three sections. Speaking about the gas turbine, GateCycle does not create problem of convergence. It is able to calculate all the cases considered with good global results. The only important difference concerns the Turbine Outlet Temperature at the two 40% load cases. Also the Correction Factor analysis gives interesting results with some exception as TOT (again) in cases with TAMB changed and output power varying the altitude. The steam cycle analysis is the one with the most different output. The global performances of the part load cases are lower about 5 % and the steam cycle parameters (especially the mass flows) are not corrected. The software is not able to reach convergence of the two 40% load cases. The combine cycle section gives an almost proper result about the design case (T AMB=0,9 °C, 100% GT load) due to the calibration explained in paragraph 3.3. In the off-design cases, the global performances are correct but mass flows and condensing pressure are quite far from the declared results. To sum up, there are for cases which work correctly in each analyzed situation: 100% gas turbine load in winter configuration (TAMB=0,9 °C) 70% gas turbine load in winter configuration (TAMB=0,9 °C) 100% gas turbine load in summer configuration (TAMB=14 °C) 70% gas turbine load in winter configuration (Tamb=14 °C) Considering these cases just listed in their combined cycle configuration, Table 81 lists the percentage differences of some key parameters between the obtained values and the ones on the data paper. Net electric power (MW) GT net electric power (MW) ST net electric power (MW) Net cycle efficiency (%) 100% W. -0,113% 0,104% -0,620% -0,056% 100 70% W. 0,412% 0,104% 1,095% -0,727% 100% S. -0,135% 0,155% -0,723% -0,111% 70% S. -0,271% 0,155% -1,022% -0,889% STEAM PART HPevap (bar) LPevap (bar) Pcond (bar) HP Steam mass flow (kg/s) LP Steam mass flow (kg/s) GAS TURBINE Fuel mass flow (kg/s) Inlet air mass flow (kg/s) Exhaust gas mass flow (kg/s) Temperature Outlet Turbine (°C) Table 81. 0,000% -0,006% -0,385% -0,832% -1,544% 0,000% 2,745% -6,316% 0,546% -2,420% 0,000% 0,004% 40,375% 4,491% -7,827% -0,001% 0,001% 28,222% 8,037% -12,922% -0,059% -0,275% -0,271% 1,142% 0,619% 0,628% -0,028% -0,061% -0,060% 0,620% 0,037% 0,047% -0,213% -0,213% -0,239% -0,271% Final evaluation table. The global performances of the whole cycle are similar to the declared ones. The net electric power of the gas turbine is higher in all of the cases but with a relative difference les than 0,2%. The net electric power of the steam turbine is lower in all the cases, with the maximum difference in the part load cases (around 1%).Considering the steam cycle, the sections with more imprecision are the ones concerning the HP and LP steam flow. The condensing pressure varies a lot from case to case, but the absolute values obtained are realistic. Examining the gas turbine features, the performances are very similar. The obtained value of fuel mass flow is higher in all the part load cases, with a maximum of 1,1 % in the 70% load winter simulation. Choosing 1,5% as limit of accuracy of the model, between the 52 analyzed percentage differences (13 parameter four times) in Table 81, ten surpass this limit (but two are lower than 3%). After all this comments, the model of the plant can be consider correct in its operating configurations and able to give an ideal representation of the real power plant. In particular, if it would be necessary to study the proceeding of the global performances in case of add of some new elements, replacement of a component with a different one and changes of technical and environmental parameters (especially at the full load operating condition of the gas turbine). 5.2 GateCycle evaluation The opinion of the writer is that GateCycle is quite intuitive and not too complicated to use but during the modeling some disguises happened. The most important inconvenience is that some elements, both heat exchangers and steam turbines, which sometimes do not work in off-design configuration and they need to be in design to make the software converge. Another important aspect concerns the output data of the gas turbine which are not calculated but read from the data curve sets. In our case with had some strange results only with the TOT at 40% load case, but probably all the output data are taken from the curves. It should be interesting to investigate more on the software about the methodology of calculation, the order of the operation and some other practical aspect which a ordinary user (as who is writing) does not know. 101 APPENDIX Document 1: h-s steam diagram utilized to calculate the isentropic efficiency of steam turbine. Document 2: Data Paper of the design case: 100% gas turbine load in winter configuration (Tamb=0,9 °C). Document 3: Correction curves for gas turbine furnished by Ansaldo. 102 103 104 105 106 107 BIBLIOGRAPHY & REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] www.ansaldoenergia.com. www.abb.com. www.ecg.com.pl. www.ec.lublin.pl. www.ens.pl. www.ec.rzeszow.pl. www.ec.zgora.pl. www.ge.com. Cengel, Yunus A. Termodinamica e trasmissione del calore. Seconda. Milano: McGraw-Hill, 2005. Chase, David L. Combined-Cycle Development Evolution and Future, GER-4206. GE Power Systems. Schenectady, NY, Gennaio 2004. Electricity/Heat data for world http://www.iea.org/stats/electricitydata.asp?COUNTRY_CODE=29. Frassoldati, Alessio. «Termodinamica dell'ingegneria chimica.» GateCycle Help, GateCycle™. Getting Started and Insallation Guide, GateCycle™. Lozza, Giovanni. Turbine a gas e cicli combinati. Seconda. Bologna: Progetto Leonardo, 2006. Spencer, R. C., K. C. Cotton, e C. N. Cannon. «A Method for Predicting the Performance of Steam Turbine Generators - 16,500 kW and Larger.» ASME Winter Annual Meeting. New York, 1974. Veatch, Black &. Power plant engineering. London: Chapman & Hall, 1996. 108
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