JP3928675B2 - Combined generator of fuel cell and gas turbine - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a combined power generation device of a fuel cell and a gas turbine.
[0002]
[Prior art]
Molten carbonate fuel cells have characteristics that are not found in conventional power generators, such as high efficiency and low environmental impact, and are attracting attention as a power generation system following hydropower, thermal power, and nuclear power. Intensive research and development is conducted in each country. In particular, in a power generation facility using a molten carbonate fuel cell using natural gas as fuel, a reformer 10 for reforming a fuel gas 1 such as natural gas into an anode gas 2 containing hydrogen as illustrated in FIG. A fuel cell 12 that generates electricity from the anode gas 2 and a cathode gas 3 containing oxygen, and the anode gas 2 produced by the reformer is supplied to the fuel cell, and most of it (for example, 80%), the anode exhaust gas 4 is supplied to the combustion chamber of the reformer 10. In the reformer 10, combustible components (hydrogen, carbon monoxide, methane, etc.) in the anode exhaust gas are combusted in the combustion chamber, and the reforming pipe is heated by the high-temperature combustion gas to reform the fuel passing through the reforming pipe. The flue gas 5 exiting the reforming chamber joins with the pressurized air 6 supplied from the pressure recovery device 15 to become the cathode gas 3, and supplies the required carbon dioxide to the cathode side of the fuel cell. A part of the cathode gas (cathode exhaust gas 7) partially reacted in the fuel cell is circulated to the upstream side of the fuel cell by the blower 14, and the rest is recovered by the pressure recovery device 15 and is recovered by the heat recovery device 18. Heat is recovered and discharged out of the system. In this figure, 8 is water vapor.
[0003]
[Problems to be solved by the invention]
As described above, the anode exhaust gas 4 exiting from the anode side of the fuel cell is required for the cell reaction by supplying the entire amount to the reformer 10 and burning it, and supplying the exhaust gas to the cathode side of the fuel cell. Recycled carbon dioxide into fuel cells.
[0004]
However, as the operating pressure of the fuel cell and the gas turbine generator rises, there is a problem that the carbon dioxide concentration in the recycle gas (CO ₂ concentration) and the CO ₂ concentration in the cathode gas increase too much.
[0005]
That is, CO ₂ gas is indispensable for the cell reaction at the cathode, but when this partial pressure becomes too high (for example, 0.5 to 0.6 at or more), Ni in the electrode elutes in the electrolyte, There is a problem that the battery life is shortened. For this reason, when the anode exhaust gas is fully recycled at a low pressure from normal pressure to several ata as in the conventional case, the CO ₂ partial pressure is low and there is no problem, but the operating pressure further increases, for example, about 10 ata or more. Therefore, it was necessary to keep the CO ₂ partial pressure in the cathode gas low and to secure the amount of CO ₂ necessary for the cell reaction.
[0006]
The present invention has been made to solve such problems. That is, the object of the present invention is to circulate the CO ₂ gas generated on the anode side of the fuel cell by a necessary and sufficient amount on the cathode side, and to keep the CO ₂ partial pressure on the cathode side low. An object of the present invention is to provide a fuel cell and gas turbine combined power generation device that can maintain high overall power generation efficiency.
[0007]
[Means for Solving the Problems]
According to the present invention, a reformer that reforms fuel gas into an anode gas containing hydrogen, a fuel cell that generates electricity from the anode gas and a cathode gas containing oxygen, and anode exhaust gas is supplied to the combustion chamber of the reformer. A gas recycling line, a combustor that burns anode exhaust gas with cathode exhaust gas to generate high-temperature gas, a gas turbine generator that is driven by the high-temperature gas to compress air and generate electric power, and anode exhaust gas that is supplied to the combustor and a control unit for controlling an amount and a pressure detector and a concentration detector for detecting the pressure and the CO ₂ concentration of the cathode gas, so the combustion exhaust gas in the combustion chamber is supplied to the cathode of the fuel cell and which, by the control device, calculates the CO ₂ partial pressure in the cathode gas from the pressure and the CO ₂ concentration of the detected cathode gas from the concentration detector and the pressure detector , The CO ₂ partial pressure is controlled anode exhaust gas quantity supplied to the combustor so as to have a predetermined range, combined cycle power generation system of a fuel cell and a gas turbine is provided, characterized in that.
[0008]
According to the configuration of the present invention, the control device can control the amount of anode exhaust gas supplied to the combustor to control the CO ₂ partial pressure in the cathode gas within a predetermined range. That is, when the operating pressure is low, the anode exhaust gas is not supplied to the combustor as in the conventional case, and the entire amount is mixed into the cathode gas through the gas recycle line, thereby reducing the total amount of CO ₂ generated on the anode side. It can supply to a cathode side and can use for the cell reaction in a cathode. If the operating pressure is high and CO ₂ partial pressure becomes a problem, a part of the anode exhaust gas is supplied to the combustor without being recycled and driven to drive the gas turbine generator. The CO ₂ partial pressure can be reduced and the CO ₂ partial pressure can be lowered. The rate of decrease in the CO ₂ partial pressure decreases rapidly as the amount of combustion in the combustor increases. For example, by burning about 10%, the CO ₂ partial pressure in the cathode gas can be increased at an operating pressure of 10 at or more. The pressure can be kept low and the amount of CO ₂ required for the battery reaction can be secured.
[0009]
Further, a pressure detector and a concentration detector for detecting the cathode gas pressure and the CO ₂ concentration are provided, and the CO ₂ partial pressure in the cathode gas is calculated from the detected cathode gas pressure and CO ₂ concentration, and the CO ₂ since the partial pressure controls the anode exhaust gas quantity supplied to the combustor to a predetermined range, the control device, to accurately grasp the CO ₂ partial pressure and the amount of CO ₂ of the anode gas, them to the desired range Can be controlled.
[0010]
【Example】
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each drawing, common parts are denoted by the same reference numerals.
FIG. 1 is a configuration diagram of a combined power generation apparatus of a fuel cell and a gas turbine according to the present invention. In this figure, the combined power generator of the present invention includes a reformer 20 that reforms a fuel gas 1 into an anode gas 2 containing hydrogen, a fuel cell 22 that generates power from the anode gas 2 and a cathode gas 3 containing oxygen, A gas recycle line 23 for supplying the anode exhaust gas 4 to the combustion chamber 20b of the reformer 20, a combustor 24 for combusting the anode exhaust gas 4 with the cathode exhaust gas 7 to generate a high temperature gas, and the generated high temperature gas. And a gas turbine generator 25 for compressing air and generating electric power.
[0011]
The reformer 20 includes a reforming pipe 20a filled with a reforming catalyst and a combustion chamber 20b for heating the reforming pipe 20a. The combustion chamber 20 b is supplied with the anode exhaust gas 4 from the gas recycle line 23, and combusts the anode exhaust gas 4 with the pressurized air 6 supplied from the gas turbine generator 18. In addition, a separate supply line for the fuel gas 1 is provided in the combustion chamber 20b so that the fuel gas 1 can be combusted as necessary. The combustion exhaust gas 5 generated in the combustion chamber 20 b is mixed in the pressurized air 6 supplied from the gas turbine generator 25 and supplied to the cathode side C of the combustion cell 12 as the cathode gas 3.
[0012]
The fuel cell 22 includes an electrolyte plate t, an anode a (electrode), a cathode c (electrode), and a separator plate s. The electrolyte plate t is a flat plate made of sintered ceramic powder, and holds molten carbonate in a high-temperature molten state in the gaps. The flat plate-like anode a and cathode c each made of sintered metal powder sandwich an electrolyte plate t therebetween. A single battery (single cell) is composed of the anode a, the electrolyte plate t, and the cathode c. The plurality of conductive separator plates s have gas flow paths on the upper and lower surfaces thereof, sandwich a single cell therebetween, and an anode gas containing hydrogen and a cathode containing oxygen and carbon dioxide gas along the anode a and the cathode c, respectively. Gas is allowed to flow. Electricity is generated by the following reaction by holding the fuel cell 22 at a high temperature of, for example, about 650 ° C. and flowing anode gas and cathode gas along the anode a and the cathode c, respectively.
[0013]
Anode reaction H ₂ + CO ₃ ²⁻ → H ₂ O + CO ₂ + 2e. . . Formula 1
Cathode reaction CO ₂ +1/2 O ₂ + 2e → CO ₃ ²⁻ . . . Formula 2
As is apparent from Equations 1 and 2, carbon dioxide (CO ₂ ) is generated by the anode reaction, and the same amount of CO ₂ is consumed by the cathode reaction. Therefore, by circulating the CO ₂ gas generated on the anode side to the cathode side, the reaction can be promoted without supplying CO ₂ from the outside.
[0014]
A recycle blower 29 is installed in the gas recycle line 23, and the anode exhaust gas 4 is supplied to the combustion chamber 20 b of the reformer 20. Thereby, a part of the anode exhaust gas 4 is combusted in the combustion chamber 20b of the reformer, and the exhaust gas is mixed into the cathode gas, whereby the CO ₂ gas can be circulated from the anode side to the cathode side. In addition, as shown by a thin line in FIG. 1, a part of the anode exhaust gas may be supplied to the inlet side of the anode. Thereby, the gas flow rate on the anode side can be increased.
[0015]
The combustor 24 is supplied with the anode exhaust gas 4 and the cathode exhaust gas 7 and combusts the anode exhaust gas 4 with the cathode exhaust gas 7 to generate a high temperature gas. A flow rate adjusting valve 26 is installed in the line for supplying the anode exhaust gas 4 to the combustor 24 so that the flow rate can be adjusted. Furthermore, a separate supply line for the fuel gas 1 is provided in the combustor 24 so that the fuel gas 1 can be combusted as necessary.
[0016]
The gas turbine generator 25 includes a gas turbine T, a compressor C, and a generator G, which are connected via a coaxial or reduction gear, and drive the gas turbine T with high-temperature gas generated in the combustor 24. The air is compressed by the compressor C driven by the gas turbine T and supplied to the reformer 20 and the like, and at the same time, the generator G is driven to generate electric power. Therefore, in the combined power generation device of the present invention, power generation is performed by both the fuel cell 22 and the gas turbine 25.
[0017]
The combined power generator of the present invention further includes a control device 30 that controls the amount of anode exhaust gas supplied to the combustor 24. Further, pressure detectors 27a and 27b and concentration detectors 28a and 28b for detecting the pressure of the cathode gas and the CO ₂ concentration are provided at the cathode side inlet or outlet (both in this example) of the fuel cell. Controller, a pressure detector 27a, 27b and concentration detectors 28a, calculates the CO ₂ partial pressure in the cathode gas from the pressure and the CO ₂ concentration of the cathode gas detected by 28b, the CO ₂ partial pressure is given The amount of anode exhaust gas supplied to the combustor 24 is controlled by adjusting the flow rate control valve 26 so as to be in the range. The predetermined range of the CO ₂ partial pressure is, for example, 0.6ata or less, and is set to a CO ₂ partial pressure at which Ni elution does not occur or is allowable. With this configuration, the CO ₂ partial pressure and CO ₂ amount of the cathode gas are accurately grasped by the control device, Ni elution does not occur or is an allowable CO ₂ partial pressure, and is required for the cathode reaction (Formula 2). it can be controlled to a sufficiently large amount of CO ₂ than the amount made.
[0018]
As described above, according to the configuration of the present invention, the control device 30 can control the amount of anode exhaust gas supplied to the combustor 24 to control the partial pressure of CO ₂ in the cathode gas within a predetermined range. That is, when the operating pressure is low, the anode exhaust gas 4 is not supplied to the combustor 24 as in the prior art, and the entire amount is mixed into the cathode gas via the gas recycle line 23, whereby the CO ₂ generated on the anode side. Can be supplied to the cathode side for cell reaction at the cathode.
[0019]
Further, when the operating pressure is high and the CO ₂ partial pressure becomes a problem, a part of the anode exhaust gas 4 is supplied to the combustor 24 without being recycled and driven to drive the gas turbine generator 25. It is possible to reduce CO ₂ in the recycle gas and lower the CO ₂ partial pressure. The rate of decrease in the CO ₂ partial pressure rapidly decreases as the amount of combustion in the combustor increases. For example, by burning about 10%, the CO ₂ partial pressure in the cathode gas is increased at an operating pressure of 10 at or more. The pressure can be kept low and the amount of CO ₂ required for the battery reaction can be secured.
[0020]
Of course, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.
[0021]
【The invention's effect】
As described above, the combined power generation device of the fuel cell and gas turbine of the present invention can circulate the CO ₂ gas generated on the anode side of the fuel cell by a necessary and sufficient amount on the cathode side, and CO ₂ on the cathode side. The partial pressure can be kept low, the elution of Ni can be suppressed, and the battery life can be extended. Moreover, since the entire amount of the anode exhaust gas is effectively used without waste by the fuel cell and the gas turbine, the overall power generation efficiency can be maintained high. Furthermore, a combustor fuel anode exhaust gas of the gas turbine, because it contains a large amount even vapor generated in the reaction, it is possible to suppress the occurrence of simultaneous NO _x Increasing the gas turbine output.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a combined power generation device of a fuel cell and a gas turbine according to the present invention.
FIG. 2 is an overall configuration diagram of a conventional power generation facility using a molten carbonate fuel cell.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel gas 2 Anode gas 3 Cathode gas 4 Anode exhaust gas 5 Combustion exhaust gas 6 Air 7 Cathode exhaust gas 8 Steam 9 Cooling water 10 Reformer 12 Fuel cell 14 Blower 15 Pressure recovery device 16 Turbine 17 Compressor 18 Heat recovery device 20 Reformer 20a reforming pipe 20b combustion chamber 22 fuel cell 24 combustor 25 gas turbine generator 26 flow control valves 27a, 27b pressure detectors 28a, 28b concentration detector 29 recycle blower 30 control device

Claims (1)

A reformer that reforms the fuel gas into an anode gas containing hydrogen, a fuel cell that generates electricity from the cathode gas containing the anode gas and oxygen, a gas recycle line that supplies anode exhaust gas to the combustion chamber of the reformer, A combustor that burns anode exhaust gas with cathode exhaust gas to generate high-temperature gas, a gas turbine generator that is driven by the high-temperature gas to compress air and generate electric power, and a control device that controls the amount of anode exhaust gas supplied to the combustor And a pressure detector and a concentration detector for detecting the pressure of the cathode gas and the CO ₂ concentration, and the combustion exhaust gas in the combustion chamber is supplied to the cathode of the fuel cell,
The controller calculates the CO ₂ partial pressure in the cathode gas from the cathode gas pressure and CO ₂ concentration detected from the pressure detector and the concentration detector , and the CO ₂ partial pressure falls within a predetermined range. The combined amount of anode exhaust gas supplied to the combustor is controlled so that the combined power generation device of a fuel cell and a gas turbine.

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