Proceedings of GT2007
ASME Turbo Expo 2007: Power for Land, Sea and Air
May 14-17, 2007, Montreal, Canada
GT2007-28336
The Air Injection Power Augmentation Technology Provides Additional
Significant Operational Benefits
Eiji Akita, Deputy Manager Service Department, Mitsubishi Heavy Industries;
Shin Gomi Manager of Services, Sales, Marketing, Mitsubishi Power Systems
Scott Cloyd, Technical Director, Mitsubishi Heavy Industries
Dr. Michael Nakhamkin, Chief Technology Officer, ESPC
Madhukar Chiruvolu, Director of Engineering, ESPC
Introduction
The AI Power Augmentation technology (HAI for humid Air injection and DAI for dry air injection) has
primary benefits of increasing power of combustion turbine/combined cycle (CT/CC) power plants by 1530% at a fraction of the new plant cost with coincidental significant heat rate reductions (10-15%) and
NOx emissions reductions (for diffusion type combustors up to 60%) (See References 1, 2, 3):
Figure 1 is a simplified heat and mass balance for the PG7241 (FA) combustion turbine (CT) with HAI
and is self-explanatory. Figure 2 presents the heat and mass balance for the PG7142 CT based combined
cycle (CC) power plant with HAI. This is similar to that presented on Figure 1 except that the humid air is
created by mixing of steam, extracted from the steam turbine, with the supplementary airflow from the
auxiliary compressor.
CT-HAI at Sea Level
Equivalent to 3.5% SI
COMPRESSOR TRAIN
Power = 12.3 MW
M
GE7FA COMBUSTION TURBINE
C
C
T
G
Fuel
Ambient Air
95 F (35C),
58 Lb/sec (26 kg/s)
5.5% H2O (M)
Ambient Air
95 F (35C),
896 Lb/sec (406 kg/s)
Steam-Air
Mixture
ESTIMATED PERFORMANCE AT 95 F(35C):
(Max. Power)
CT
CT-HAI
NET POWER, MW
150.4
177
INCREMENTAL POWER,MW 0
27.4
NET HEAT RATE, Btu/kWh 9,760
9,380
kcal/kWh (LHV)
2,460
2,364
HRU
STACK
30 Lb/sec (14 kg/s)
Make-up Water
Figure 1: Heat and mass balanced for the CT-HAI Plant based on PG7241 (FA) combustion turbine.
CC-HAI at Sea Level
GE7FA COMBUSTION TURBINE
Steam Turbine
C
Evap Cooler
Ambient Air
95 F (35C)
896 Lb/sec (406 kg/s)
COMPRESSOR TRAIN
Power = 12.3 MW
M
C
T
G
Fuel
G
Stack
SteamAir
Mixture
410 psia (28 bar)
Ambient Air
95 F (35C), 58 Lb/sec (26 kg/s)
ESTIMATED PERFORMANCE AT 95 F(35C):
CC
CC-HAI
NET POWER, MW
221
250.3
INCREMENTAL POWER,MW 0
29.3
NET HEAT RATE, Btu/kWh
6,508
6,.690
kcal/kWh (LHV)
1,640
1,686
HRSG
SF Fuel
Recuperator
Figure 2: Heat and Mass balance for the CC-HAI Plant based on PG 7241 (FA) Combustion Turbine.
The latest project development by ESPC in cooperation with CT/CC users and OEMs identified a number
of additional effective operational benefits of the AI technology that sometimes are driving factors for the
AI technology applications in addition to the prime application for power augmentation. These additional
operational benefits are generic and applicable to variety of CT/CC plants and for variety of power
generation markets.
This paper describes technical and commercial findings of these specific operational benefits of the AI
technology based on its application for the power augmentation of M501F based 2x1 combined cycle
power plant with capacity of approximately 500 MW - a Mitsubishi Heavy Industry (MHI) project in
South America. In this paper, the estimated by ESPC benefits of the application of the AI technology are
based on the performance characteristics and the equipment and operating limits provided by MHI. It
should be expected that MHI will identify additional operating and equipment capabilities limits
particularly for specific projects, such as GT generator limits, etc.
The main operational benefits of the AI technology could be summarized as follows:
•
•
•
The incremental power introduced by the AI technology meets the spinning reserve requirements and
allows CT/CC plants operate at full load with the best efficiency.
The AI technology power augmentation provides the opportunity for CC/CT plants to deliver the
required power at lower turbine Firing Temperatures (FT) as compared to a CC/CT without the AI
technology with significant increase of “hot” components life and operational performance benefits.
The AI technology can function as the load management plant
HAI Provides Spinning Reserve
Typical combined cycle power plants operate at 93-95% load factor to meet the spinning reserve
requirements, i.e. the 7-5% of valuable capital cost and operational assets are not being effectively used.
The application of the AI power augmentation technology can augment/increase the combined cycle
power plant power by 15%-20% within seconds thus allowing users to run CTs or primarily the highest
efficiency combined CC power plants at full load with the design point efficiency.
In order to quantify the effects of the use of the AI technology as a spinning reserve, ESPC conducted
economic analysis of the application of the AI technology as the spinning reserve for operating the
Mitsubishi M501F based on 2x1 CC power plant with total capacity of approximately 500 MW at 92F and
60%RH ambient conditions. Figure 2 presents estimated performance characteristics of the CC power plant
for two modes of operations: two curves represent the power and heat rate of the CC plant operating at a
reduced load to meet spinning reserve requirements and another two curves represent the power and heat
rate of the CC plant operating at a full load with the AI system to meet the spinning reserve requirements
as well as providing a significant power augmentation.
6,200
110.00
GTCC With HAI For Spinning Reserve
6,150
105.00
GTCC
6,100
100.00
Spinning Reserve
6,050
95.00
6,000
90.00
GTCC + HAI
5,950
P o w e r O u tp u t % Is o R a tin g
H e a t-R a te B T U /k w h
GTCC + HAI
85.00
GTCC
5,900
30
40
50
60
70
80
90
100
80.00
110
Ambient Temperature oF
Figure 2- CC operations with Spinning reserve margins and with the AI for the spinning Reserve
The basic analysis of economic benefits of using the AI technology to provide a spinning reserve (as well
as power augmentation) and utilizing the full 500 MW M501F based 2x1 combined cycle power plant
capacity (otherwise operating at 92% load factor to provide the spinning reserve capacity) could be
summarized as a follows:
Capital Assets Recovery:
•
If the 500 MW CC plant operates at 92% load factor, approximately $30M capital value associated
with the unused approximately 40MWs are practically not utilized and kept as the spinning reserve.
The AI technology functioning as a spinning reserve allows the combined cycle power plant to
operate at full load with full utilization of the capital assets. The capital cost of the 40 MW power
augmentation of the M501F based 2x1 CC plant using the AI technology are estimated as
approximately $8M. Thus, the application of the AI power augmentation for the spinning reserve
allows the recovery of approximately 22 MWs of stranded assets’ and capital cost.
Additional revenues:
•
Additional revenues associated with full utilization of the M501F based 2x1 CC plant (additional
40 MW) could be as high as $24M/year (based on 6000 hrs/year and $100/MWh electricity costs)
•
During peak demand situations the M501F based 2x1 CC plant can operate at full capacity
(500MW) plus additional the AI power augmentation of 40MW for a total power of 540MW. This
capability adds additional strategic and operational flexibility and revenues.
Fuel Saving:
The increase in the CC load from 92% to 100% will reduce the heat rate by approximately 1%.
Economic evaluations for various installations have shown that, for application of the AI power
augmentation for the spinning reserve of CC power plants, the payback- period will be less than a year.
The AI Technology Allows Reduction of the FT with Significant Reduction of Maintenance Costs,
NOx Emissions and Fuel Savings
The AI technology provides other significant operational and performance benefits by the fact that it
allows CT/CC power plants to operate at lower FT as compared to the plants without the AI technology.
Figure 3 represents the performance parameters of the Mitsubishi M501 F operating at 35C (95F) ambient
temperature over a wide range of loads with and without the AI power augmentation technology. Figure 3
demonstrates that the AI technology increases power from approximately 170 MW (design load) to
approximately 200-210 MW with the heat rate reduction by approximately 700-1000 kJ/kWh.
Figure 3, also, shows that the CT with the AI technology operates with the reduced firing temperatures
over the whole rage of operating loads with coincidentally reduced heat rates. For example, at the design
point of approximately 170 MW and at lower loads the FT is reduced by approximately 110C (200F), as
compared to the FT without the AI technology, with approximately 500-700 kJ/kWh heat rate reduction.
These benefits of the AI technology are similarly applicable to the various heavy duty as well as aircraftderivative CTs of various sizes.
.
13000
1400
Firing
Temperature
without HAI
1200
12000
Heat Rate (kJ/kWhr)
800
11000
600
Heat Rate
without HAI
Firing Temperature (C)
1000
Firing
Temperature
with HAI
400
10000
Heat Rate
with HAI
200
9000
50
70
90
110
130
150
170
190
210
0
230
Power (MW)
Figure 3 TIT and Heat Rates of M501F Operating
without and with the AI technology
The reduction of the TIT provides the following additional benefits of the AI technology:
•
It significantly increases the life of CT blades and other “hot” components and consequently
reduces maintenance costs of CT/CC plants;
•
It provides significant fuel savings;
•
It further reduces NOx emissions.
Reduction of the FT Increases lives of CT blades and other “hot” Components and Reduces of
Maintenance Costs of CT/CC plants
A number of papers by OEMs and operators quantify the significant effect of the increase/reduction of the
FT on the component life. For example the leading OEM, GE, concludes that “Significant operation at
peak load, because of the higher operating temperatures, will require more frequent maintenance and
replacement of hot-gas path components. For a MS7001EA turbine, each hour of operation at peak load
firing temperature (+100°F/56°C) is the same, from a bucket parts life standpoint, as six hours of
operation at base load. This type of operation will result in a maintenance factor of six. Figure 12 defines
the parts life effect corresponding to changes in firing temperature. It should be noted that this is not a
linear relationship, as a +200°F/111°C increase in firing temperature would have an equivalency of six
times six, or 36:1”. GE Publication: GER-3620k, “Heavy-Duty Gas Turbine Operating and Maintenance
Considerations”, Dec., 2004.
Other operator concluded that “Each hour of operation at 100oF/56oC under base conditions is equivalent
to 0.2 hours of operation at the base load” Paper No: 05-IAGT-2.2
Based on data provided by OEMs and users, ESPC developed Figure 4 representing generic correlations
between FT increase/reduction from design level and the maintenance interval changes for major “hot”
section inspections of CTs with conservatively diminished effects of the reduced FT on maintenance. This
Figure 4 demonstrates that the reduction of FT by the AI technology by approximately 110C (200F)
increases maintenance intervals by a factor of two (2), i.e. reduces maintenance costs also by a factor of 2.
With the typical maintenance costs of $2.5-3/MWh the associated saving will be approximately $1.251.5/MWh
Reduction of the FT Provides Fuel savings.
As it was mentioned above, Figure 3 shows that at the design load of approximately 170 MW the AI
technology, with the reduced FT of approximately 100 C, allows reduction of the heat rate by
approximately 500-700 kJ/kWh (i.e. approximately 5-7% heat rate reduction). This FT and heat rate
reductions take place over the whole range of part load operations.
In addition,” hot” gas path components are cleaner for longer duration; this contributes to fuel savings of
approximately1.0 to 1.5% as an average between maintenance intervals.
Therefore the reduction of the FT will reduce currently very high fuel costs (approximately $10-12
/MWh) by 6-8%.
TIT Vs Maintenance Interv al
100
50
0
o
Change In TIT ( C) from Base Load TIT
150
-50
-100
-150
1%
10%
100%
1000%
M aintenance Inteval as % of Base load interval
Figure 4: Correlations between FT Changes and Intervals for “Hot” Sections Inspections
Reduction of the FT Reduces NOx Emissions.
The AI technology reduces the NOx emissions as demonstrated by two independent diffusion combustor
tests conducted by Textron and Aero Industrial (USA) technology (Britain) and presented in the Figure 5.
(see Reference 4)
NOx Emissions Tests with Humid Air Injection
100.0
10.0
U
ns
ta
bl
e
NO x PPM
1000.0
1.0
0.1
0
10
20
30
40
% H2O /AIR
Actual tests of combustors operating with humid air demonstrated significant NOx reductions
from 75 ppmv for dry to single digits for humid air operations. Reference: Combustion Studies of
Natural Gas and Syn-Gas with Humid Air, EPRI 1994, TR-103382
Figure 5. Tested Combustors NOx Emissions as
Function of the Humidity
Figure 6. NOx Concentration vs. Flame Temperature
Based on the general theory the NOx production by combustors is directly proportional to the residence
time of mass particles in the combustor and exponentially proportional to the flame temperature. The
injection of the humid/dry air flow (approximately 10-15%) upstream of combustors increases the total
mass flow through the combustors and reduces (by approximately 10-15%) the residence time of the flow
particles in combustors and, therefore, reduces (by approximately 10-15%) NOx emissions.
The reduction of the operational FT by 110C/200F for a given combustor will provide similar reduction
of the flame temperature and associated additional reduction of NOx emissions as shown on the figure
below.
References.
1.
2.
3.
4.
Air Injected Power Augmentation is Validated By Fr7FA Peaker Tests, GTW, March-April, 2002.
“Humidified Air Injection Raises Peak Turbine Output,” Power Engineering, November 1999.
Injecting Humidified and Heated Air to meet peak Power Demands, 2000-GT-0596.
“Combustion Studies of Natural Gas and Syn-Gas with Humid Air.” EPRI Conference on
Gasification Power, 1994.
5. R. Hall, D. Bradshaw, TVA “Advanced Combustion Turbine Cycles Meet the Needs of the Utility of
the Future, Power-Gen, 1999.