Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
Universidade Federal de Santa Catarina
Centro Tecnológico
Departamento de Engenharia Mecânica
Coordenadoria de Estágio do Curso de Engenharia
Mecânica
CEP 88040-970 - Florianópolis - SC - BRASIL
www.emc.ufsc.br/estagiomecanica
[email protected]
Internship’s Report– 1st out of 3
Period: from 16th of February 2009 to 16th of April 2009
Siemens Fuel Gasification Technology GmbH & Co. KG
Intern: José Lourenço Magri
Internship’s Supervisor: Dr. Joachim Lamp
UFSC Supervisor: Prof. Edson Bazzo
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
Freiberg, 16th of April 2009
Table of Contents
1.
Gasification and The Siemens Fuel Gasifier .................................................................................... 3
a.
The Siemens Fuel Gasifier ................................................................................................................ 4
b.
The Siemens Gasification Test Center ............................................................................................. 6
2.
Developed Activities – Determination of Slag Viscosity Behavior .................................................. 7
a.
Basic Definitions and Chronogram of Activities .............................................................................. 7
b.
Ash Fusibility Tests........................................................................................................................... 9
c.
Ash Viscosity behavior and Measurement System ........................................................................ 10
d.
Flux Admixture............................................................................................................................... 16
e.
Results’ Evaluation ........................................................................................................................ 18
3.
Summary ....................................................................................................................................... 20
4.
Bibliography................................................................................................................................... 21
5.
Attachments .................................................................................................................................. 22
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
1. Coal Gasification and The Siemens Fuel Gasifier
High oil and gas prices have led to a resurgence of coal as an affordable energy source. Especially coal
rich regions have increasingly been tapping their local resources. This allows them to reduce their
reliance on foreign imports of natural resources and at the same time achieving stable prices to meet
the ever growing energy demands.
In its widest sense, the gasification process covers the conversion of any carbonaceous fuel to a
gaseous product with a useful heating value. Therefore, it includes processes such as pyrolysis,
partial oxidation and hydrogenation. The dominant process is partial oxidation which produces
synthesis gas (syngas) consisting of hydrogen and carbon monoxide in varying ratios [1], whereby the
gasification media can be pure oxygen, air and/or steam. This process can be applied to solid, liquid
and gaseous feed stocks.
During the gasification the coal is exposed to temperatures that would normally cause it to combust
but, by carefully regulating the amount of oxygen in the gasifier and adding steam, the coal does not
completely burn but rather cracks its molecules into syngas. This gas can also be ‘shifted’ with
additional steam added as gasification medium, intending the production of more hydrogen and to
convert the carbon monoxide into carbon dioxide
Figure 1-1: Process of the Coal's Gasification
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
The environmental requirements are becoming more and more stringent all over the world. Coal
Gasification offers one of the cleanest and most flexible ways to convert coal and low-grade fuels
into high-value products – electricity, chemicals or synthetic fuels. The combination of gasification
with modern gas turbines results in a highly efficient technology for coal-based power generation,
the so called Integrated Gasification Combined Cycle (IGCC). Coal is combined with oxygen and steam
in the gasifier to produce the syngas. The gas is then cleaned to remove impurities, such as sulfur –
posterior sold in the market as a by-product – and the syngas is used in a gas turbine to produce
electricity. Waste heat from the gas turbine is recovered to create steam which drives a steam
turbine, producing more electricity – hence a combined cycle system. IGCC efficiencies typically reach
the mid-40s, although plant designs offering around 50% efficiencies are achievable. Furthermore,
they can also be combined with readily available technology for CO2 Capture and Storage (CCS). For
the CO2 removal, standard chemical or physical absorption processes can be applied. After the
sequestration, CO2 is compressed and transported to underground storage sites for Enhanced Oil
Recovery, for example.
a. The Siemens Fuel Gasifier
For the gasification of coal are mainly three types of reactors used, as described in table below:
Table 1- 1:Reactors' Types
Moving-Bed Gasifiers
Fluidized-Bed Gasifiers
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Entrained-Flow Gasifiers
Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
Moving-Bed Gasifiers are Fluidized-Bed Gasifiers offer extremely Entrained-Flow
characterized by a bed in good
mixing
between
feed
Gasifiers
and operate with feed and blast in
which coal moves slowly oxidant, which promotes both heat co-current flow. The residence
downward under gravity and mass transfer. This ensures an time in these processes is short,
as it is gasified by a blast, even distribution of material in bed, and
high-temperatures
are
that can be counter- and hence a lower percentage of required to guarantee a good
current to the coal’s partially reacted material is removed conversion, and therefore all
movement. In such a with the ash. The use of this type of entrained-flow gasifiers work in
arrangement,
syngas
the
from
hot gasifiers usually limits the process the slagging range. Pro aspects
the temperature to levels below the of the process are the high
gasification zone is used softening point of the ash, since the oxygen demand, on the other
to pre-heat and pyrolysis formation of slag will disturb the hand these gasifiers do not
the downward flowing fluidization [3]. The average size of have any technical limitations
coal [3]. This process is particles is also critical, as material on the type of coal used,
characterized by the low that is too fine tends to become although
high-moisture
oxygen consumption , entrained with the syngas and leave content coals may find in other
but high pyrolysis’ sub- the overhead. The lower temperature processes better economical
products
quantity operation means that the process is advantages. [3]
present in the product more suited for gasifying reactive
gas.
Coal + O2
feedstocks, such as low-rank coals and
Coal
biomass.
Coal
Slag + Gas
Steam +
O2
Slag / Ash
Steam +
O2
Slag / Ash
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
The SFG process features a top-fired reactor where the reactants are
introduced into the reactor through a single centrally mounted burner.
This concept has a number of special aspects, such as a simple
asymmetrical construction, use of a single burner, reducing the number
of flows to be controlled to three (coal, oxygen and steam). And finally,
the slag and hot gas leave the reactor together. This characteristic
reduces any blockages an slag tap, as well as allowing for both partial
and total water quenches, depending on the application.
The gasifiers are equipped with a cooling screen, consisting of spiralwounded tubes filled with pressured cooling water. The first molten slag
drops from the gasification process affix to this cooling screen and
solidify. This builds up a protection layer against the high reaction
temperatures. Later liquid slag from the reaction phase comes only in
contact with this solidified slag layer, and hence no corrosion of the
reactor wall can take place.
The cooling screen design ensures long gasifier availability periods
Figure 1 -2: Siemens
Entrained-Flow Gasifier
before requiring repair or relining. Compared with traditional refractory
lining the cooling screen is insensitive to coals with high ash content or
fluctuating ash composition. Furthermore, the gasifier can start up or shut
down within few minutes. Cold start up can be done in less than two hours, whereas by refractory
lined gasifiers this can take days.
Noxious components such as particulates, sulfur and nitrogen compounds which are typical of
gasification are removed by conventional gas treatment and conditioning processes downstream the
gasification process.
The Siemens Coal Gasifier SFG500, for example, is 18 meters long with an inside diameter of 3
meters and weigh 220 tones, are among the world’s largest and most powerful.
b. The Siemens Gasification Test Center
The Gasification Test Center in Freiberg, Germany, is considered to be one of the most
comprehensive gasification test facilities in the world. The heart of the Siemens Gasification Test
Center is a 5MWth gasification reactor and can operate with pressures up to 26 bar. The test gasifier
Figure 1-2: Siemens
Gasification Test Facility
in Freiberg, Germany.
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
is complemented by a range of feed stock preparation systems and related gas cleaning process
units. Further equipment for coal and slag analysis (like slag viscosity measurement) is available also
in the facility. With these equipments, a broad range of test conditions can be simulated in order to:
Determine detailed analytical data of feed stock and gasification
products;
Optimize feed stock preparation to maximize gasification efficiency and carbon conversion
rate;
Determine the optimum gasification process conditions;
Gain valuable experience about the expected products and environmental performance.
c. Siemens’ Solutions
Siemens gasifiers are suited for power generation also in the so called Integrated Gasification
Combined Cycle (IGCC), as well as production of chemicals and synthetic fuels. The resulting products
can be used in the most different purposes, as refineries, fertilizer production, transportation, etc.
Values of the company are to deliver a more reliable, efficient, competitive and easier to maintain
technology. The Siemens scope of supply are:
Licensing of the Siemens Fuel Gasification Technology;
Process Design Package (PDP) and Basic Engineering Design Package (BEDP);
Supply the key equipment like reactor, cooling screen, burner and more;
Feasibility and FEED studies ;
Fuel Assessment;
Engineering Services and Technical Field Assistance.
2. Developed Activities – Determination of Slag Viscosity Behavior
a. Basic Definitions and Chronogram of Activities
In the gasifier, organic material in coal is gasified under high temperature and high pressure
conditions. The ash (the inorganic components) exposed to high-temperature conditions liquefies,
forming slag. The molten ash particles accumulate on the internal walls of the gasification chamber ,
namely the cooling screen; and cool down. The wall is covered by a layer of solid slag, over which the
liquid slag will flow under the force of gravity and get out by the bottom of the gasifier into a water
quenching system [2]. Fig. 2-1 shows a slag deposit and the Temperature Distribution of a typical
Entrained-Flow Gasifier’s Slag Deposit. Because of small temperature excursions, the boundary
between solid and liquid slag will move a little, so that the solid and liquid slag transform each other
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with variation of temperature. The properties of the liquid slag layer formed between ash and solid
slag are important for the successful operation of a slagging gasifier. Thus there is need to
characterize ash and slag properties, such as the physical properties, fusion temperature, viscosity,
the influence of fluxing material, the temperature of critical viscosity (Tcv).
TSiC
SiC
Figure 2-1: Slag Deposit and the Temperature Distribution of a typical Entrained-Flow Gasifier’s Slag Deposit
It is important that no slag can be accumulated on the exit of the gasifier, obstructing it, as well as on
the walls of the gasifier, reducing the reaction room and minimizing the heat exchange. The viscosity
of 25 Pa∙s is generally accepted to be the upper limit for the slag fluidity required for its removal from
slagging entrained flow gasifiers. The corresponding temperature is referred as T25. The optimum slag
viscosity for tapping is between 8 and 12 Pa∙s at normal operating temperatures. The determination
of this temperature is normally based on a test called Ash Fusibility Test (which shall be explained in
a later section), whose results are based on visual observations of the solid sample of ash and then
heated up until the sample liquefies. Empirical tests showed that the proper the ideal viscosity can be
achieved at temperatures 250K above the fusion temperature [3].
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
Another way to determine these figures use of a proper viscometer. In this procedure a sample is
melted and the viscosity is measured directly upon cooling and controlled reducing atmosphere. This
method delivers more reliable results, as they are obtained directly from a liquid sample and the
boundary conditions can be approached to the real process.
Therefore for the first part of the internship was to measure the viscosity of molten slag, under
boundary conditions, that shall imitate the gasification process ones, and verify the gasification
potential of a determined coal. Parallel to that, for caparison purposes, the Ash Fusibility Test of the
same coal was also made. Also during the viscosity trials it was researched the influence on the
viscosity of the addition of different amounts of limestone (the most common type of flux) to the
sample of ash. The admixture of limestone (CaCO3) to the coal as flux is recommended to weaken or
break crystal lattices of compounds such as Al2O3 and SiO2 (parts of the slag composition), whose
existence modifies the viscosity, reducing it. [1]
Having that in mind the following chronogram of activities was proposed for the first eight weeks:
Table 2-1: Chronogram of Activities
Period
Activities
16th Feb – 28th Feb (2 Weeks)
Literature Research
2nd of Mar – 11th Mar (1 and ½ Week)
Devices’ Calibration.
11th of Mar – 3rd Apr ( 2 and ½ Weeks)
6rd Apr – 16th Apr (2 Weeks)
Melting of Samples, Viscosity Measurements
and Emptying of Crucibles.
Result Analysis and Report writing.
b. Ash Fusibility Tests
The coal ashes were prepared on muffle furnaces under ambient atmosphere and the slag samples
were obtained during the gasification trial at Siemens Fuel Gasification Technology Co & KG. (SFGT).
The test material was analysed and the ash fusibility behaviour studied by an external laboratory
contracted by SFGT.
The method for determination of the fusibility temperatures of coal ash and slag are described in the
norm ISO 540 – Hard coal and coke – Determination of ash fusibility, which provides information
about the fusion and melting behaviour of the coal ash. This procedure occurred after preparing
small cubic samples (3 mm edges) of compressed ash or slag and then melted under a reducing
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
atmosphere, in order to reproduce the gasification conditions, at a constant heating rate. Using a
microscope the deformation of the samples was observed.
The Fusibility is characterized by four main temperature points, described as follows:
Table 2-2: Ash Fusibility Key Points
Temperature Point
Deformation Temperature (DT)
Definition
Appereance
Temperature at which the first signs of
rounding, due to melting, of the edges.
Temperature at which the edges of the test
Sphere Temperature (ST)
pieces become completely round with the
height remaining unchanged.
Temperature at which the sample forms
Hemisphere Temperature (HT)
approximately a hemisphere, i.e. when the
height becomes equal to half of the base
diameter.
Temperature at which the ash melt is spread
Flow Temperature (FT)
out over the supporting tile in a layer, the
height of which is one-third of the height of
the test piece at the hemisphere temperature.
Considering that just the visible modifications are taken in account to determine that the sample is
totally melted, shows the incertitude of the procedure, depending mainly on the operator’s visual
ability and/or on the quality of the optical devices. This means that the results of duplicate
determinations, performed in each of two different laboratories on representative portions taken
from the same sample, can differ up to 80°C (see ISO 540). For the results please see section 2-e of
this report.
c. Ash Viscosity behavior and Measurement System
Coal slag, as a multi compound system, does not usually have a distinct melting point like chemical
elements or pure compounds. During the solidification process, the viscosity of molten slag increases
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
gradually in a broad range in dependence of the temperature and composition. Above liquidus
temperature the completely molten slag behaves like a Newtonian fluid. The types of slag are
defined based on their different flow characteristics (see figure 2-3).
The Know How of the relationship between slag viscosity and temperature is of great interest. The
slag viscosity is a function of temperature and slag composition and plays a key role in determination
of the performance and usability of a certain feedstock in a slagging gasifier. This may be conquered
by either adding a flux or blending with another coal with more suitable ash characteristics.
Figure 2-2: Slag flow Parameter
A Rotational Viscometer, which is based on a cylindrical arrangement, is the most widely used
apparatus for the measuring of dynamic viscosity of fluids under high temperature conditions. They
can be two distinguished types, the Couette and the Searle Viscometer, at which either the crucible
containing the molten compound (Couette) or the spindle merged in the slag (Searle principles)
rotates. For the measurements, having in mind the construction principles and simplicity of use, the
Searle Measuring System was chosen.
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
Torsional
Moment
Measuring
System
Figure 2-3: Couette (left) and Searle (right) and Viscometers.
In both cases the molten slag moves between the two cylinders. The crucible or the gauging unit (a
spindle) rotates with constant rotational speed. The melted mass is then displaced the torsional
moment on the gauging unit transmitted und measured. Then the viscosity will be determined on the
torsional moment and the angular velocity, making use of the following equation:
η – Dynamic Viscosity [Pa.s]
L – Spindle’s Height [m]
M – Torsional Moment [Nm]
Ri – Spindle’s Internal Radius [m]
Φ – Angular Velocity [rad/s]
Ra – Crucible’s Internal Radius [m]
This equation is valid only for infinite cylinders. Applying the needed correction factors, the following
equation can be used for practical cases:
η – Dynamic Viscosity [Pa.s]
τ – Shearing Constant [N/m2]
M – Torsional Moment [Nm]
– Shear Rate
n – Frequency [1/s]
– Shearing Stress Constant
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
– Shear rate Constant
Table 2-4: DIN versus Relative System
DIN-System
Relative System
General
Dimensions
>2
Flow Velocity
Profile in the
Measuring Gap
Results
Evaluation
k shall be determined through
calibration measurements
CL is a cross sectional area factor.
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
There are two most common ways to obtain the correction coefficients, namely a relative and a
direct procedure. The difference between both of the is correlated to the geometry of the measuring
systems. By the direct procedure a proper geometry for the crucible and bob are regulated under the
DIN norms (DIN 53019), as well as all the mathematical calculation needed for an approach of the
possible solutions. By the relative procedure the correlation factors should be obtained through
calibration of the system with standard oils (room temperature) and standard melted glasses (high
temperatures). A comparison of both methods can be seen on the above table 2-4. For construction
reasons the relative measuring system as adopted.
The complete high temperature viscosity measurement device employed in this research is
schematically shown in Figure 2-4 and 2-5. The melting temperature and viscosity measurements
were carried out in a bottom loaded tube furnace LORA (Laboratory Oven for Reducing
Atmospheres). Argon 5.0 was used to maintain an inert atmosphere in the furnace to protect the
molybdenum resistors. An inner cylinder rotational viscometer was adapted to a high temperature
measuring instrument with a molybdenum shaft and bob assembly. The crucible is also made of the
same material. The temperature measuring devices are purged with forming gas (95% Argon plus 5%
Hydrogen). Moreover a ceramic protection tube is positioned above the crucible to prevent incidents
of over expansion of slag due to bubble formation and hence preventing damages to the experiment
apparatus.
The measuring system was developed under the DIN norms series 53108 and 53019. For the high
temperature calibration a Soda-Lime-Glass G1, which is certified in the temperature range from
525°C up to 1500°C, was used as standard. From the calibration results (see attachments, chapter 5)
it is to be seen, that the measuring system is in accordance with the respective norms.
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
Figure 2-4: High Temperature Viscosity Measurement Station
The effective range of this viscometer together with the slag measurement system is from 2 to 140
Pa∙s. According to ASTM (American Society for Testing and Materials), the maximal allowed cooling
rate is recommended to be maximum 4 K/min in viscosity measurement on glass melts. The slag
viscosity measurement was undertaken upon cooling at 2 K/min until solidification or the slag
viscosity turned to be at least 40 Pa.s. Record of data of dynamic viscosity and temperature where
taken every 15 seconds. The temperature was measured by a thermocouple, positioned directly next
to the crucible.
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Protection
Pipe
Mo Crucible
Melted Slag
Mo-Spindel
Figure 2-5: Geometry of the gauging elements.
Figure 2-6: Laboratory furnace LORA
d. Flux Admixture
As prior discussed in section 2.c., coal has silicates and aluminates as main compounds where the
greater part is composed of silicates. Therefore the slags can be also described as a silicate melts. The
slag components can be arranged in three groups as network formers, network modifiers and
amphotherics. Network formers are cations, which will occupy tetrahedral positions and hence, act
as building blocks. The Network Modifiers, on the other hand, act weakening this chain, having a
disruptive effect. And amphotherics can play both roles.
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Figure 2-7: An alkaline earth metal ion (such as Ca+2) can weaken the silica network by lengthening a bond between two
silicon atom.
The addition of limestone (the most common type of flux, CaCO3) increases the amount of Calcium
Oxides in the slag, which act as a network modifiers [1]. With the addition of alkaline earth oxide
(CaO, BaO, MgO, for example) to silica, Si±O bonds are broken and the cations are randomly
distributed throughout the lattice, giving rise to two major effects :
weak points in the silica network introduced by the rupture of Si ± O bonds;
a general loosening of the lattice owing to the polarizing effect of the cation that weakens
the Si±O bonds near the metal ion, i.e. weakening the silicate and aluminates lattices
(network formers), resulting in minimized viscosities.
Therefore, to research the effect of addition of flux directly on the viscosity relationship with the
temperature, the following samples with CaO as flux addition were prepared for the viscosity
measurements:
Table 2-5: Analysed Coal + Flux Samples
Fraction of Flux added to the
Sample [%]
Prepared
5
Samples
10
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Internship’s Report – SIEMENS Fuel Gasification Technology GmbH & Co. KG
e. Results’ Evaluation
The fusibility behaviour shows that the gasification temperature for the analysed Coal is within the
acceptable temperature range (approximately 1600°C) [3].
Table 2-3: Ash Fusion Temperature (AFT) for pure SFG-Slag
Point
Temperature [°C]
Deformation Temperature (DT)
1126
Sphere Temperature (ST)
1226
Hemisphere Temperature (HT)
1310
Flow Temperature (FT)
1333
For further investigations to fix and optimize the necessary gasification temperature additional
viscosity tests with the coal slag were carried out. The pure slag viscosity analysis showed that the
sample has a glassy behaviour, so its gasification temperature can be obtained through the point T25.
It also observed that the slag viscosity started decreasing at high temperature levels, so the T25 point
was just reached at the temperature of 1639°C, as shows the blue curve on the graphic below (figure
2-8). The tapping temperature should be 100 - 150K higher than the T25 to avoid plugging of the slag
discharge according to the uncertainty in adjusting the gasification temperature. So the minimal
gasification temperature should be between 1710 ̊C – 1750°C, applicable values, as the maximum
temperature for the SIEMENS Gasifier is by 1850 C
̊ limited.
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Figure 2-8: Temperature - Viscosity Behavior with Flux Admixture
This result differ more than 100°C of the suggested temperature of the AF Test. Having in mind that
for the proper use of the cooling screen, the properties of the fluid slag should be taken in account, a
viscosity analysis gives more reliable results. These are taken directly from the liquid sample over a
range of temperatures. By the AFT a solid sample is observed and from this observation, is the
gasification temperature is appraised.
The addition of flux showed a good correction of the values to a future applicability of this type of
coal to the gasification process. In the cases of flux addition of 5% to the sample, the result shows a
T25 value of 1555°C. By increasing the limestone admixture to 10% the T25 value decreases to 1457°C.
A possible overall gasification temperature starts at 1650°C until 1550°C, hence practicable values.
One can say that, if more flux is added the viscosity can be reduced at the cost of additional heating.
This is required for the fusion of the limestone and for its calcinations (thermal decomposition of
limestone which releases the calcium oxide).
+178.4 kJ/mol + CaCO3  CaO  CO2
But in the reality this extra thermal energy is already available in the gasifier. The addition of
limestone reduces the gasification temperature, representing an economy for the process regarding
needed coal and oxygen quantities to be burned, in order to reach such temperature levels.
Disadvantages of the limestone addition is the quantity of slag formed during the process (as calcium
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oxide goes completely to the slag composition) and posterior treatment of the waste. Therefore an
economically optimum has to be found.
3. Summary
The former ash fusibility analyses indicates a coal, which is suitable for the SFGT Gasification, with a
process temperature of 1600°C. Nevertheless a more detailed analysis of the real relationship
between temperature and viscosity showed that for the analysed coal that the real practicable
gasification temperature should be at values around 1700°C. With the addition of flux the gasification
temperature can be corrected to optimized values, regarding economy of fuel, oxygen and waste
disposal. Further analytical and/or experimental investigation with new mixtures of flux are
necessary in order to dwindle the gasification temperature to the optimized values.
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4. Bibliography
[1] WU, Baoting. Praktische und theoretische Untersuchungen zum Viskositätsverhalten an
Aschen und Schlacken von Vergasereinsatzstoffen. 2007. 118 p. Diplomarbeit (Diploma) Technische Universität Bergakabemie Freiberg, Freiberg - Germany, 2007.
[2] SONG, Wenjia et al. Fusibility and flow properties of coal ash and slag. Fuel, Shanghai,
China, p. 297-304. 07 out. 2008.
[3] HIGMAN, Cristopher; VAN DER BURGT, Maarten. Gasification. 2nd Edition Oxford: Gulf
Professional Publishing, 2008.
[4] VARGAS, S.; FRANDSEN, F. J.; DAM-JOHANSEN, K.. Rheological properties of hightemperature melts of coal ashes and other silicates. Progress In Energy And Combustion
Science, Lyngby, Denmark, p. 237-429. 15 jul. 2000.
YUN, Yongseung; YOO, Young Don; CHUNG, Seok Woo. Selection of IGCC candidate coals by
pilot-scale gasifier operation. Fuel Processing Technology, Republic of Korea, p. 107-116. 05
ago. 2004.
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5. Attachments
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