CH701210A1 - Method for operating a gas turbine power plant with fuel cell. - Google Patents

Abstract

The invention relates to gas turbine power plants with fuel cell (15), which incorporates a new process management, which optimizes a CO 2 capture optimized in the power plant process, and a method for operating such a power plant. The gist of the invention is a method of operating a gas turbine power plant with exhaust gas recirculation into the intake stream of the gas turbine (6) and a fuel cell (15), wherein CO 2 is separated from the non-recirculated exhaust gases in the fuel cell. The recirculation mass flow (21) is controlled to optimize the overall performance and the overall efficiency of the power plant so that under the boundary condition of a stable, efficient gas turbine operation, the exhaust gas composition of the gas turbine enables optimal operation of the downstream at least one fuel cell (15). Furthermore, a power plant for carrying out the method is the subject of the invention.

Description

Technical area

The invention relates to a method for operating a gas turbine with a molten carbonate fuel cell and a power plant with gas turbine and Schmelzkarbonatbrennstoffzelle.

State of the art

Due to the generally recognized risk of climate change, there is a worldwide interest in the emission of greenhouse gases, in particular to reduce CO2 (carbon dioxide). As a realistic step to reduce the CO2 emissions into the atmosphere within a relatively short time becomes the so-called CO2 (carbon capture and storage) or CO2 sequestration, ie the separation of CO2 from the thermal power of a power plant and the atmosphere separate storage of the separated CO2 , viewed. The CO2 separation occurs either from the exhaust gases after the combustion of a carbonaceous fuel or by a chemical reaction in which the carbon is separated from the fuel before combustion. The regeneration of absorbers, adsorbers or other means of CO2 capture is part of the CCS process.

Post-combustion CO2 capture, also called backend capture or post-combustion capture, is one of the most promising CCS technologies and also applicable to gas turbine and combined cycle power plants.

[0004] Conventional CO2 technologies require relatively high power. To minimize the negative impact of CO2 on performance and efficiency, US Pat. No. 3,796,603 proposed the combination of conventional power plants with molten carbonate fuel cells.

The use of molten carbonate fuel cells to reduce CO2 emissions from gas turbine power plants has been further described by J. Milewski et al. in THE REDUCTION OF CO2 EMISSIONS OF GAS TURBINE POWER PLANTS BY USING OF A MOLTEN CARBONATE FUEL CELL (ASME Turbo Expo 2007: Power Land, Sea Air, 2007, Montreal, Canada, GT2007-27030).

However, the use of molten carbonate fuel cells to reduce the CO2 emissions of gas turbine power plants is not without problems, since the CO2 content in the gas turbine exhaust gases, as well as by J. Milewski et al. described is low for effective operation of molten carbonate fuel cells. Due to the large exhaust gas mass flow of a gas turbine to be treated also large arrangements of fuel cells are necessary, which are associated with high costs. Further, the exhaust gas temperature and exhaust gas composition of a gas turbine greatly change depending on the operating conditions. In particular, the compressor inlet temperature and the load of the gas turbine lead to changes in the exhaust gas temperature and exhaust gas composition, so that an optimal operation of the fuel cell can not be guaranteed.

Presentation of the invention

The present invention has the object of providing a cost-effective method for optimized overall efficiency operation of a gas turbine fuel cell power plant with CO2 deposition, and to propose a power plant for performing this method.

According to the invention, this object is solved by the subject matter of the independent claims. Advantageous embodiments are the subject of the dependent claims.

As gas turbine fuel cell power plant while a gas turbine based power plant is referred to, from the exhaust gases or at least from a partial mass flow of the exhaust gases with the aid of at least one molten carbonate fuel cell (hereinafter referred to as fuel cell) CO2abschiedieden. Typically, the usable heat or waste heat of the exhaust gases in at least one waste heat boiler is used. The steam generated in the at least one waste heat boiler is expanded to produce electrical energy in a steam turbine under work or used as process heat in a combined heat and power.

The essential element of CO2 capture is the fuel cell. It is supplied with exhaust gas from the gas turbine on the cathode side and supplied with fuel on the anode side. In a fuel cell with internal reforming fossil fuel gases such as methane or natural gas can be used directly. In other fuel cells, hydrogen is used as fuel gas or it is an external reforming before the fuel cell provided.

In the fuel cell, the reformed hydrogen of the anode side reacts with the exhaust gases of the cathode side. Electrical energy is generated and most of the CO2 transported to the anode side and derived via the exit of the cathode side. Next arises as reaction product water, which is also released in vapor form on the anode side. The water can be easily separated by condensation. Depending on further use, the CO2 rich exhaust stream of the anode can be forwarded directly after condensation of the water or be fed to a further treatment. Exhaust gas with reduced CO2 and oxygen content escapes from the cathode side, which can be released to the environment via a chimney.

The essence of the invention is a method for operating a gas turbine power plant with exhaust gas recirculation in the intake stream of the gas turbine and at least one fuel cell, wherein CO2 is separated from the non-recirculated exhaust gases in the at least one fuel cell, and a power plant for performing the method , The method is characterized in that the recirculation mass flow is controlled to optimize the overall performance and the overall efficiency of the power plant. For this purpose, the recirculation mass flow is controlled such that, under the boundary condition of a stable gas turbine operation, the exhaust gas composition of the gas turbine enables optimum operation of the downstream at least one fuel cell. For optimum operation of the fuel cell, the CO2 content of the exhaust gases is increased by recirculation, to the extent that this permits the associated reduction in the oxygen content.

As a stable gas turbine operation is understood to mean an operation in which the combustion is complete and without strong Brennkammerpulsationen, as they can occur at too low combustion temperature and low oxygen content occurs.

In the proposed new method can be adjusted to the requirements of the downstream fuel cell by regulating the Rezirkulationsmassenstroms the exhaust gas composition for the entire operating range, especially for partial load.

The exhaust gas composition of a gas turbine, in particular the CO2 and oxygen concentration of the exhaust gases or the CO2 content and oxygen content, is dependent on the composition of the compressor intake gases and various operating parameters. A regulation of the recirculation mass flow for adaptation to the requirements of the downstream fuel cell can be regulated accordingly as a function of at least one operating parameter of the gas turbine. For example, the recirculation mass flow can be regulated as a function of the load of the gas turbine and / or the turbine inlet temperature and / or the position of the at least one adjustable Verdichtervorleitreihe to optimize the exhaust gas composition for the downstream fuel cell.

In a further embodiment, an online gas analysis of the gas turbine exhaust gases between gas turbine and entry into the fuel cell is proposed for the regulation of the exhaust gas composition. Alternatively, an online gas analysis of the recirculation mass flow or of the gas turbine intake air can also be carried out after admixing the recirculation mass flow.

In addition to the content of CO2 and oxygen content in the exhaust gas, the TAT (turbine outlet temperature) and thus the inlet temperature into the fuel cell can also be readjusted by varying the recirculation mass flow and / or the temperature of the recirculation mass flow. In particular, the temperature to which the recirculation mass flow is recooled can be used for this purpose.

As long as the gas turbine is not limited by a TAT limit, the TAT is proportional to the compressor inlet temperature at a constant relative load. In this case, the ratio of current power to full load power at the same ambient boundary conditions, in particular at the same inlet temperature is referred to as a relative load. For example, increasing the compressor inlet temperature at a constant relative load will increase the TAT. The TAT can therefore be influenced or readjusted by regulating the compressor inlet temperature without interfering with the operating concept of the gas turbine.

In a further embodiment, the inlet temperature is controlled in the fuel cell with a, arranged between the gas turbine and the fuel cell, temperature control waste heat boiler. This has mainly the function of cooling the gas turbine exhaust gases to the optimum for the operation of the fuel cell fuel cell inlet temperature. Depending on the design of the gas turbine and its operating point, the TAT is above the optimum fuel cell inlet temperature. With a waste heat boiler whose dissipated heat can be regulated, the fuel cell inlet temperature can be regulated over wide load ranges. The fuel cell inlet temperature can be controlled solely by a temperature control waste heat boiler or in combination with the TAT control. The waste heat dissipated in this boiler is used profitably, for example in a water-steam cycle.

An important step towards increasing the efficiency is to increase the CO2 content of the exhaust gases by exhaust gas recirculation for effective operation of the fuel cell. In a further embodiment, CO2 is recirculated from the anode outlet of the fuel cell to increase the CO2 content in the cathode mass flow before or when entering the fuel cell. The diversion to recirculation is possible immediately after the fuel cell, to or from the anode downstream waste heat boiler, after the separation of water or after further treatment of the anode exhaust stream. At a branch off the waste heat boiler, a separate waste heat boiler may be provided for the recirculated CO2 rich mass flow to maintain the inlet temperature to the fuel cell in the optimum operating range. In the case of recirculation of CO2 after the separation of water or after further treatment, it may be advantageous to preheat the recirculated CO2 stream before it is added to the cathode mass flow. This can take place for example by heat exchange in one of the waste heat boiler or take place in heat exchange with the exhaust gases. Upon removal from the waste heat boiler, the recirculation mass flow can be diverted directly to the optimum temperature level. This CO2 recirculation provides an additional parameter for controlling the CO2 content and temperature of the cathode mass flow at the fuel cell inlet.

In order to allow a recirculation of CO2, a reduction of the exhaust gas recirculation may be required to ensure sufficient for the fuel cell oxygen content.

By controlling the Rezirkulationsmassenstroms, the temperature of the recirculated exhaust gases and the recirculated CO2 stream and the temperature of the recirculated CO2 stream to get new Regeigrössen with which the TAT or the fuel cell inlet temperature even at partial load in the for the operation the fuel cell required temperature range can be maintained.

As a constraint in the regulation of the recirculation mass flow of the gas turbine must be ensured that the oxygen content in the gas turbine intake air sufficient for clean complete combustion, and that the oxygen content in the gas turbine exhaust gases sufficient for the operation of the fuel cell.

Depending on the further use of the CO2-rich anode exhaust gases, a water separation with subsequent CO2 deposition may be required. Due to the high CO2 concentration in the anode exhaust gases, CO2 capture is possible, for example, through CO2 absorption with relatively little energy expenditure. This can be particularly advantageous when the fuel cell is operated with incomplete fuel conversion and a relatively high proportion of unburned fuel gases remains in the anode exhaust gases. The unburned fuel can continue to be used after CO2 capture. For example, the unburned fuel may be beneficially recirculated to the anode inlet along with other gases remaining in the exhaust gas.

Operation of the fuel cell with incomplete fuel conversion typically results in a higher efficiency of the fuel reacted in the fuel cell, therefore, operation with incomplete fuel conversion and CO2 separation may be beneficial.

Another way to operate the fuel cell with incomplete fuel conversion is the combination with at least one catalytic burner. This can either be integrated in the outlet region of the fuel cell or be arranged separately in the exhaust gas streams of the fuel cell.

Depending on the type of fuel cell and operating condition, the exhaust gases are loaded with high emissions and impurities. By subsequent combustion in a catalytic burner, the purity of the exhaust gases can be increased. This can be advantageous in particular if only a water separation is provided as aftertreatment. This simplifies the overall structure and process. The heat released by the catalytic combustion is also usefully used in the downstream waste heat boiler.

An advantage of the method with exhaust gas recirculation is the increase in the CO2 content in the exhaust gases, which leads to an increase in the fuel cell efficiency. Further, the cathode mass flow of the exhaust gases to be treated is reduced, whereby the size of the fuel cell and thus the equipment costs can be reduced.

Furthermore, the CO2 content can be kept close to the optimum over a wide operating range, so that the partial load efficiency of the fuel cell and thus of the entire power plant is also increased.

In order to achieve a high overall efficiency of the power plant, the usable waste heat from at least part of the recirculation streams and the exhaust gas streams is used in at least one waste heat boiler for steam generation in other embodiments. The steam can be usefully used for combined heat and power or be relaxed under work to drive a generator in a steam turbine.

In a further embodiment, the method is proposed to a power plant with a gas turbine with sequential combustion. Conventional gas turbines with sequential combustion are known, for example, from EP0 620 362. Such a gas turbine has at least one compressor followed by a first combustion chamber and a first turbine. The exhaust gas flow of the first turbine is reheated in a second combustion chamber before it is further expanded in a second turbine. Gas turbines with sequential combustion typically have the advantage of a high turbine exit temperature. Thus, in a wide operating range, typically from about 40% to 50% relative load to full load, boundary conditions for a temperature control waste heat boiler are created, which make it possible to set the cathode inlet temperature of the fuel cell to the optimum temperature. This is model specific and is typically in the range of about 550 ° C to 650 ° C, for example about 600 ° C.

In addition to the method, a power plant for carrying out the method of the invention. A power plant for implementation consists of at least one gas turbine, at least one fuel cell and at least one line for exhaust gas recirculation of a portion of the exhaust gas stream of the gas turbine in the intake air of the gas turbine.

To control the recirculation mass flow either an adjustable flap, a fixed exhaust divider with subsequent control element, such as a flap or a valve, a controllable fan or other suitable control member is provided in the exhaust stream of the gas turbine.

In order to use the waste heat of the gas turbine and / or the fuel cell, typically at least one waste heat boiler is arranged downstream of the gas turbine and / or downstream of the fuel cell. Typically, a waste heat boiler is further disposed in the recycle stream.

For better control of the input temperature of the fuel cell, a waste heat boiler between gas turbine and cathode inlet of the fuel cell can be arranged. In order to allow a temperature control, this waste heat boiler is characterized for example by the fact that the feed water quantity is regulated depending on the outlet temperature of the exhaust gases.

In order to provide a further possibility for regulating the CO2 content of the cathode inlet gases of the fuel cell, a CO2 recirculation line can be arranged from the exhaust gases of the anode side of the fuel cell in the exhaust gas line of the gas turbine upstream of the cathode inlet of the fuel cell. As a control element, for example, a valve or an adjustable flap in combination with a blower can be provided in the recirculation line or in its connections. Alternatively, for example, a controllable CO2 recirculation fan can be arranged in the CO2 recirculation line or in its connections.

With this additional control element, in combination with the exhaust gas recirculation of the gas turbine, the CO2 content in a wide operating range of the power plant can be regulated for optimized operation of the fuel cell. As a broad operating range, this typically refers to the range from full load to about 50% load. Depending on the design of the gas turbine and the recirculation lines, the proposed combination can even optimize the CO2 content up to a lower partial load, for example up to 30% partial load or less.

Further advantages and embodiments of the invention are described in the dependent claims and will become apparent from the description and the accompanying drawings. All explained advantages can be used not only in the respectively specified combinations, but also in other combinations or alone, without departing from the scope of the invention.

An embodiment is characterized for example by an exhaust gas bypass to the fuel cell. This allows operation of the gas turbine without the fuel cell, as long as the exhaust gases of the gas turbine at start or very low part load, i. Load points of training up to, for example, about 30% partial load, for the operation of the fuel cell are too cold. In addition, it allows the operation of the gas turbine when the fuel cell, for example, for maintenance out of service.

Brief description of the drawings

The invention is illustrated by means of embodiments in FIGS. 1 to 3 schematically.

In the drawings:

1 shows a gas turbine power plant with a fuel cell for CO2 separation, an exhaust divider for dividing the gas turbine exhaust gases into a recirculation mass flow and a cathode inlet flow, [0042] FIG.

2 shows a gas turbine power plant with a fuel cell for CO2 separation, a temperature control waste heat boiler, an exhaust divider for dividing the gas turbine exhaust gases into a recirculation mass flow and a cathode inlet flow, and in the fuel cell on the cathode and Annodenseite to the fuel cell subsequent catalytic burner .

3 shows the example of the course of the CO2 content in the exhaust gases of a conventional gas turbine without recirculation, the course of the CO2 content in the exhaust gases of a gas turbine of a gas turbine power plant with fuel cell and exhaust gas recirculation and the associated profile of the recirculation rate over relative load.

Embodiment of the invention

Fig. 1 shows schematically a gas turbine power plant with fuel cell for CO2 separation for carrying out the inventive method. It consists of a gas turbine 6 and at least one fuel cell 15. The gas turbine 6 comprises in known manner at least one compressor 1, at least one combustion chamber 4 and at least one turbine 7. Typically, a generator 25 at the cold end of the gas turbine 6, that is on the compressor 1, coupled.

The fuel 5, gas or oil is mixed in the combustion chamber 4 with compressed in the compressor 1 gases and burned. The hot gases are released under work delivery in the following turbine 7. According to the invention, the exhaust gases of the gas turbine are divided in an exhaust divider 29 into two partial mass flows. A first partial mass flow, the recirculation mass flow 21 is recirculated into the intake air 2 after discharge of the usable heat in a first waste heat boiler 9 and recooling in an exhaust gas recirculation recooler 27. The exhaust gas recirculation recooler 27 typically has a condensate trap (not shown). Various types of exhaust gas recirculation recoolers 27 are known. For example, they can be designed as an air heat exchanger and the waste heat emitted to the ambient air. If sufficient amounts of cooling water are available, water cooling is beneficial. In particular, if so on hot days, the inlet temperature can be lowered into the gas turbine to improve their performance. In addition, the size is smaller.

The live steam 30 of the waste heat boiler 9 is passed to a steam turbine 13 for power output. In the example shown, the steam turbine 13 drives a second generator 26 via a shaft. The waste heat boiler 9 with steam cycle is shown greatly simplified. Condenser, feedwater pumps and other known components of the steam cycle are not shown for simplicity. Typically, the steam cycle is performed as a multi-pressure circuit.

A second partial mass flow, which is passed as Katodenmassenstrom 20 in the cathode 17 of the fuel cell 15. The CO2 arms exit gases of the cathode 17 are passed into a second waste heat boiler 33, where they give their usable heat for steam generation. This steam can be used for power delivery to a steam turbine or beneficial for combined heat and power. The waste heat boiler 33 may be connected to the steam cycle of the first waste heat boiler 9 (not shown) and thus a common steam turbine can be driven. The cathode exhaust gases are emitted as low-CO2 exhaust gas 22 from the second boiler 33 via a chimney 32 to the environment.

The exhaust gases or a part of the exhaust gases of the gas turbine can be passed from the exhaust divider 29 via an exhaust gas bypass 24 also directly to the chimney 32. This is regulated, for example, via a bypass flap or a bypass valve 12. Thus, for example, to start the gas turbine whose exhaust gases are discharged directly through the chimney 32, as long as they are still too cold for the operation of the fuel cell 22. In addition, the bypass 24 allows the operation of the gas turbine 6, when the fuel cell 15 is turned off, for example, for maintenance purposes. The bypass 24 further allows in combination with the recirculation mass flow, a flexible control of the exhaust gas mass flow, which is passed through the fuel cell 15.

The anode 18 of the fuel cell 15 is supplied with fuel for fuel 28. The fuel 28 is tuned to the type of fuel cell 15. For example, hydrogen can be used. For fuel cells 15 with internal reforming, natural gas or pure methane can be used. The fuel 28 reacts in the fuel cell 15 while delivering electric power 8.

The CO2 rich exit gases of the anode 18 are conducted in a third waste heat boiler 34, where they give their usable heat for steam generation. This steam can be used for power delivery to a steam turbine or beneficial for combined heat and power. The waste heat boiler 34 may be connected to the steam cycle of the first waste heat boiler 9 and / or the second waste heat boiler 33 (not shown), thereby driving a common steam turbine.

The moisture contained in the exhaust gases of the anode side of the fuel cell 15 is removed after the third boiler 34 in a water separator 23. The remaining anode exhaust gases 35 have a high CO2 concentration. In the example shown, they are sent directly for further use, for example for compression for transport and disposal. But they can also be fed to a further treatment.

In the example shown, a recirculation of CO 2 rich anode exhaust gases of the fuel cell 15 is further provided in the cathode inlet. By means of a CO2 recirculation blower 38, a portion of the CO2-rich anode exhaust gases of the fuel cell 15 can be conveyed to the cathode inlet by means of the CO2 recirculation line 38 shown. The CO2 recirculation flow can be regulated via the CO2 recirculation fan 38 and / or via the flap or valve for the CO2 recirculation flow 39. If no CO2 recirculation is required, the recirculation fan 38 can be switched off and closed by closing the flap or the Valve for the CO2 recirculation flow 39 an unwanted bypass of the gas turbine exhaust gases are prevented by the fuel cell 15 in the anode exhaust gases 35.

In a further embodiment, the second and third waste heat boiler 33/34 are combined in a boiler. Furthermore, the second and / or the third waste heat boiler can be combined with the first waste heat boiler 9.

In the example shown, an exhaust gas blower for the recirculation mass flow 11 is provided and an exhaust gas blower for the cathode mass flow 10 is provided. Depending on the pressure of the exhaust gases from the turbine 7 and the pressure losses in the flow paths of the two partial streams can be dispensed with the blower.

In order to realize a good control of the gas composition for gas turbine 6 and fuel cell 15, in the example shown, an intake air CO2 and / or 02 measuring instrument 36 and a gas turbine exhaust CO2 and / or 02 measuring instrument 37 are provided.

Fig. 2 shows schematically a second example of a gas turbine power plant with fuel cell for CO2 deposition. In this example, a temperature control waste heat boiler 43 is additionally arranged between the turbine 7 and the exhaust divider 29. By controlling the waste heat, which is withdrawn from the gas turbine exhaust gases 19, the inlet temperature of the gases of the cathode 17 of the fuel cell is controlled.

Further, in Fig. 2, a fuel cell 15 is shown with downstream catalytic burner 40 on the anode side and with downstream catalytic burner 41 on the cathode side. The catalytic burners allow the operation of a fuel cell 15 with incomplete fuel conversion. As fuel conversion while the proportion of the fully oxidized fuel is referred to the entire fuel 28 for the fuel cell 15.

A fuel cell 15, for example, under the boundary conditions, as given by the gas turbine exhaust gases 19, at partial fuel gas conversion achieve a higher efficiency based on the converted fuel gas for the fuel cell 28, as if a virtually complete combustion gas conversion is sought. As a complete fuel gas conversion, a conversion of more than 99% of the fuel gas 28 can typically be considered. Further, by reducing the fuel conversion, the cell voltage and the power density of the fuel cell 15 can be increased and thus the size of the fuel cell 15 can be reduced.

Depending on the course of the fuel cell efficiency via conversion of the fuel gas 28 in the fuel cell 15 and the downstream third waste heat boiler 34 with associated water vapor cycle, the optimal implementation will be, for example, 80% to 90%. The implementation for an optimal overall efficiency of the power plant is lower, the better the heat released during the catalytic combustion can be used in the subsequent water-steam cycle.

The remaining parts of the power plant shown in Fig. 2 correspond to the parts with the same reference numeral from Fig. 1st

FIG. 3 shows by way of example the course of the CO2 content in the exhaust gases of a conventional gas turbine without recirculation GT-CO2, the course of the CO2 content in the exhaust gases of a gas turbine of a gas turbine power plant with fuel cell and over the relative load Prei of the gas turbine 6 Exhaust gas recirculation R-CO2 and the associated course of the recirculation rate rr. The CO2 content of the exhaust gases is standardized in the example for both the conventional gas turbine and for the gas turbine with recirculation with the CO2 content at full load of the gas turbine with recirculation.

The recirculation rate rr is normalized with the recirculation rate at full load of the gas turbine with recirculation. As the recirculation rate, the quotient of Rezirkulationsmassenstrom 21 is designated by the total exhaust gas mass flow of the gas turbine.

In the example shown, the CO2 content of the exhaust gases with recirculation R-CO.sub.2 in the entire load range is kept clearly above the CO2 content without recirculation GT.sub.2 CO.sub.2. At partial load below about 60% pri, the recirculation rate rr is reduced in this example to ensure complete, stable combustion of the gas turbine. Combined with a CO2 production of the gas turbine which decreases at partial load, this leads to a noticeable reduction in the CO2 content in the exhaust gases with exhaust gas recirculation R-CO2. The CO2 content in the exhaust gases during exhaust gas recirculation R-CO2, however, remains significantly above the CO2 content without Exhaust gas recirculation GT-CO2.

Since the residual oxygen content in the exhaust gases in the case of exhaust gas recirculation is inversely proportional to the CO2 content in the exhaust gases, in this example below about 60% Prei a CO2 recirculation can be carried out from the anode outlet of the fuel cell 15 into the cathode inlet and thus the CO2 content can be set to the optimal value for the fuel cell 15 even at low partial load.

The possible embodiments of the invention are not limited to the examples presented here. On the basis of the examples, the person skilled in the art will be able to realize a multitude of equivalent combinations of gas turbines with fuel cells and methods for their operation. In particular, in the arrangement of the various components of the power plant, the use of waste heat for combined heat and power, also called cogeneration, or for example for fuel gas preheating are many possibilities. For example, the temperature control waste heat boiler 43 may also be arranged between the exhaust manifold 29 and the fuel cell 15. Furthermore, a large number of combinations is also possible for the aftertreatment of the exhaust gases and the CO2-rich exhaust gas stream.

In a further embodiment in which the recirculation rate rr at partial load is not limited by an unstable combustion as in the example shown in FIG. 3, the CO2 content of the gas turbine exhaust gases 19 can be increased up to a low partial load by increasing the recirculation rate rr be kept at the optimal level for the fuel cell 15. So can be dispensed with a recirculation to the fuel cell (15) even at low partial load.

However, in one embodiment with high recirculation rate rr at low part load, the CO emissions of gas turbine 6 typically increase. As high, CO emissions (carbon monoxide emissions) are typically considered to be 10 ppm and more. The CO emissions at part load with high recirculation mass flow can quickly increase to over 100 ppm or even a few hundred ppm.

Due to the advantageous inventive arrangement, the gas turbine exhaust gases 19 are passed with the high CO emissions in the fuel cell 15. There the CO reacts with water vapor to CO2 and hydrogen H2. The hydrogen will continue to react on the cathode side. Due to the low CO concentrations and resulting low hydrogen concentrations, the hydrogen conversion is easily tolerated. Furthermore, a catalytic conversion of the CO with residual oxygen of the exhaust gases 19 to CO2 is possible. For this purpose, for example, a catalytic burner 41 on the cathode side is suitable, which is designed as a surface catalyst with nickel. The CO2 exits according to the implementation in the fuel cell 15 from the anode 18 of the fuel cell 15.

LIST OF REFERENCE NUMBERS

[0070] <Tb> 1 <sep> compressor <Tb> 2 <sep> ambient air <Tb> 3 <sep> Verdichteransauggas <Tb> 4 <sep> combustion chamber <tb> 5 <sep> fuel for GT <tb> 6 <sep> Gas Turbine GT <Tb> 7 <sep> Turbine <tb> 8 <sep> Electrical power <tb> 9 <sep> first waste heat boiler (HRSGheat recovery steam generator) <tb> 10 <sep> exhaust fan for cathode mass flow (to the fuel cell) <tb> 11 <sep> Exhaust blower for recirculation mass flow (exhaust gas recirculation) <tb> 12 <sep> Bypass damper or by-pass valve <Tb> 13 <sep> steam turbine <Tb> 14 <sep> capacitor <Tb> 15 <sep> Fuel Cell <Tb> 16 <sep> feed water <Tb> 17 <sep> cathode <Tb> 18 <sep> anode <Tb> 19 <sep> gas turbine exhaust gases <tb> 20 <sep> cathode mass flow (exhaust pipe to the fuel cell) <tb> 21 <sep> recirculation mass flow (line for exhaust gas recirculation) <tb> 22 <sep> CO2 low exhaust gas <Tb> 23 <sep> Water <Tb> 24 <sep> exhaust bypass <tb> 25 <sep> First generator <tb> 26 <sep> Second generator <tb> 27 <sep> Exhaust recirculation recooler (for recirculation mass flow) <tb> 28 <sep> fuel for fuel cell <Tb> 29 <sep> exhaust manifold <Tb> 30 <sep> steam <Tb> 31 <sep> <Tb> 32 <sep> Fireplace <tb> 33 <sep> Second waste heat boiler (for cathode outlet) <tb> 34 <sep> Third waste heat boiler (for anode outlet) <Tb> 35 <sep> anode exhaust gas <tb> 36 <sep> intake air CO2 and / or 02 meter <tb> 37 <sep> Gas turbine exhaust CO2 and / or 02 meter <tb> 38 <sep> CO2 recirculation fan <tb> 39 <sep> Flap or valve for CO2 recirculation flow <tb> 40 <sep> Catalytic burner, anode side <tb> 41 <sep> Catalytic burner, cathode side <Tb> 42 <sep> Water <tb> 43 <sep> Waste heat boiler for exhaust gas temperature control <tb> Prel <sep> Relative load of the gas turbine <Tb> rr <sep> recirculation <tb> GT-CO2 <sep> CO2 Concentration of gas turbine exhaust gases without recirculation <tb> R-CO2 <sep> 2 CO2 Concentration of gas turbine exhaust gases with recirculation

Claims (15)

1. A method for operating a gas turbine power plant with a fuel cell (15) for separating CO2 from the exhaust gas stream of the gas turbine (6), characterized in that the gas turbine exhaust gases (19) are divided into a Katodenmassenstrom (20) and a Rezirkulationsmassenstrom (21), the Katodenmassenstrom (20) is introduced into the cathode inlet of the fuel cell (15) and the recirculation mass flow (21) is cooled and is recirculated into the intake flow of the gas turbine (3). 2. The method according to claim 1, characterized in that the CO2 and / or oxygen concentration of the gas turbine exhaust gases (19) is regulated by regulating the recirculation mass flow. 3. The method according to any one of claims 1 or 2, characterized in that the recirculation mass flow is regulated as a function of an operating parameter of the gas turbine (6). 4. The method according to any one of claims 1 to 3, characterized in that the recirculation mass flow as a function of the load of the gas turbine (6) and / or the turbine inlet temperature and / or the position of the at least one adjustable Verdichtervorleitreihe is regulated. 5. The method according to any one of claims 1, 3 or 4, characterized in that the CO2 and / or oxygen concentration of the gas turbine exhaust gases (19) and / or the compressor intake air of the gas turbine (3) are measured and this measured value as an input for the Regulating the recirculation mass flow is used. 6. The method according to any one of claims 1 to 5, characterized in that the Einstrittstemperatur of the Katodenmassenstroms (20) in the cathode side of the fuel cell (15) by regulating the Rezirkulationsmassenstroms (21) and / or a recooling temperature of the recirculation mass flow (21) is readjusted. 7. The method according to any one of claims 1 to 6, characterized in that between gas turbine (6) and fuel cell (15) at least one temperature control waste heat boiler (43) is arranged with controllable waste heat and the inlet temperature of the cathode mass flow (20) in the Katodenseite the fuel cell (15) via the regulation of the waste heat output of this temperature control waste heat boiler (43) is controlled. 8. The method according to any one of claims 1 to 7, characterized in that for controlling the CO2 concentration of the cathode mass flow (20) in the cathode inlet of the fuel cell (15) a part of an outlet stream from the anode (18) recirculated into the cathode mass flow (20) becomes. 9. The method according to any one of claims 1 to 8, characterized in that the conversion of the fuel of the fuel cell (28) in the fuel cell (15) is incomplete and a remainder of this fuel of the fuel cell (28) in at least one catalytic burner (40, 41 ) disposed in or downstream of the fuel cell (15) is burned. 10. The method according to any one of claims 1 to 9, characterized in that usable waste heat from the cathode mass flow (20) and / or the recirculation mass flow (21) and / or at least one of the exhaust gas streams of the fuel cell (15) in at least one waste heat boiler (9, 33, 34, 43) is used to generate steam. 11. The method according to any one of claims 1 to 10, characterized in that in the cathode mass flow (20) CO contained in the fuel cell (15) reacts and emerges as CO2 from the anode (18) of the fuel cell. 12. A gas turbine power plant with fuel cell for CO2 separation consisting of at least one gas turbine (6), at least one fuel cell (15), at least one exhaust divider (29) from which at least one recirculation line to the compressor suction side of the gas turbine (6) leads and at least one line to the cathode inlet of the fuel cell (15) leads. 13. A power plant according to claim 12, characterized in that between gas turbine (6) and fuel cell (15) at least one temperature control waste heat boiler (43) for controlling the inlet temperature of the cathode mass flow (20) arranged in the cathode side of the fuel cell (15) is. 14. A power plant according to claim 12 or 13, characterized in that at least one recirculation line leads from the anode outlet to the cathode inlet of the fuel cell (15). 15. A power plant according to any one of claims 11 to 14, characterized in that at least one catalytic burner (40, 41) for combustion of fuel residues in the outlet gases of the fuel cell (15) in or downstream of the fuel cell (15) is arranged.