JP2015050162A - Gasification fuel cell hybrid power generation system and operational method thereof - Google Patents

Abstract

A gasification fuel cell combined power generation system capable of improving combined power generation efficiency using existing technology such as a gas turbine used in IGCC or the like is provided. A fuel gas obtained by gasifying carbonaceous solid fuel in a gasification furnace 10 and purified by a gas purification unit 20 is supplied to generate power by a solid oxide fuel cell 30 and a gas turbine 40 to drive a generator. Gasified fuel that performs power generation using the steam turbine 51 that operates by introducing steam generated by using the exhaust heat of the combustion exhaust gas discharged from the gas turbine 40. In the combined battery power generation system, the fuel gas supply system F includes a fuel cell gas supply system Fs that supplies the fuel gas by connecting the fuel gas from the gas purification unit (20) to the solid oxide fuel cell 30, and a gas. The gas turbine gas supply system Fg is connected to the turbine 40 and supplies fuel gas. [Selection] Figure 1

Description

  The present invention relates to a fuel gas obtained by gasifying a carbonaceous solid fuel in a gasification furnace, such as an integrated coal gasification fuel cell combined power generation system (IGFC) using a fuel gasified from coal. TECHNICAL FIELD The present invention relates to a gasification fuel cell combined power generation system including a fuel cell using a gas generator and performing a combined power generation and an operation method thereof. The carbonaceous solid fuel referred to here includes biomass fuel such as thinned wood, waste wood, driftwood, grass, waste, sludge, tires, etc. in addition to coal and petroleum coke.

In recent years, demand for thermal power generation has been increasing, but more efficient thermal power generation is required in consideration of environmental problems.
As one of the future plant high efficiency technologies for thermal power plants, for example, a coal gasification fuel cell combined power plant disclosed in Patent Document 1 below is known. This prior art combines a combined fuel gasification combined cycle facility (hereinafter referred to as “IGCC”) with a fuel cell such as a solid oxide fuel cell (hereinafter referred to as “SOFC”). It is configured and is also called a coal gasification fuel cell combined power generation system (hereinafter referred to as “IGFC”).

In other words, IGFC uses a fuel gas that is gasified by supplying carbonaceous solid fuel to a gasification plant, and in addition to power generation in SOFC, it generates power by driving a generator with a gas turbine and a steam turbine. System.
For example, as shown in FIG. 2, a conventional IGFC is a gasification furnace 10 that gasifies coal and a gas that is refined by applying necessary treatment to the fuel gas (coal gasification gas) generated in the gasification furnace 10. And a purification unit 20. The fuel gas generated in the gas purification unit 20 is supplied to the SOFC 30 to generate power, and the exhaust gas (unburned fuel gas) of the SOFC 30 is supplied to the combustor 41 of the gas turbine 40 that drives the generator G. Supplied as The gas turbine 40 includes a compressor 42 and a turbine 43 as main components in addition to the combustor 41 described above.

The combustion exhaust gas that has worked in the gas turbine 40 is supplied to an exhaust heat recovery boiler (hereinafter referred to as “HRSG”) 50 that recovers exhaust heat and generates steam. The steam generated by the HRSG 50 is supplied to the steam turbine 51 that drives the generator G. Although the illustrated generator G is coaxially connected to the gas turbine 40 and the steam turbine 51, a dedicated generator may be connected to the gas turbine 40 and the steam turbine 51 to generate power.
Therefore, the illustrated IGFC is a combined power generation facility in which power generation by the SOFC 30 and power generation by the generator G using the gas turbine 40 and the steam turbine 51 as drive sources are combined.
In the figure, reference numeral 60 denotes an oxygen production apparatus, 70 denotes an extraction air booster, and 52 denotes a chimney.

JP 2000-48844 A

  By the way, the conventional IGFC generally receives part or all of the air pressurized and heated at the compressor 42 of the gas turbine 40 with respect to the air electrode of the SOFC 30. Further, the air supplied to the air electrode of the SOFC 30 consumes a certain amount of oxygen for the reaction in the SOFC 30 and then is supplied to the combustor 41 as combustion air for the gas turbine 40 at a lower oxygen concentration than the normal atmosphere. The That is, the IGFC air system has a configuration in which the SOFC 30 and the gas turbine 40 are connected in series.

In addition, since the unburned fuel gas discharged from the SOFC 30 is also used in the fuel gas supplied to the gas turbine 40, the amount of heat generated from the fuel gas varies depending on the influence of the power generation status of the SOFC 30. Become.
For this reason, the following restrictions (problems) in design and operation have been pointed out for SOFC 30 and gas turbine 40 of IGFC.

The first constraint is the fuel gas heating value used in the gas turbine 40.
Along with the power generation in the SOFC 30, the fuel gas supplied to the gas turbine 40 is reduced in the heat generation amount of the fuel gas. In order to keep the performance of the gas turbine 40 constant using the fuel whose calorific value has decreased (to keep the gas turbine combustor combustion temperature constant), it is necessary to increase the amount of fuel gas at the gas turbine inlet, That is, it is necessary to increase the coal heat input supplied to the gasification furnace 10. However, as the coal heat input increases, the flow rate of gas flowing from outside the system, such as coal transfer inert gas and oxygen, also increases, so the effect on plant performance, especially plant efficiency, is limited, or There is also the possibility that it will be offset and will have no effect.

The second constraint is the required oxygen concentration of the combustor of the gas turbine 40.
In general, oxygen necessary for completely burning fuel gas in the combustor 41 of the gas turbine 40 is supplied by air introduced from the compressor 42 of the gas turbine 40. On the other hand, the combustor 41 has a minimum oxygen concentration for stable combustion. However, in the IGFC, for example, as in the configuration disclosed in Patent Document 1, air that consumes oxygen in the SOFC 30 may be supplied, so depending on the operating conditions of the SOFC 30, there is a possibility that it will be lower than the minimum oxygen concentration. .

The third constraint is differential pressure control during high pressure operation in the SOFC 30.
It is known that the performance of the SOFC 30 improves as it operates at a higher pressure. However, in order to operate the SOFC 30 at a high pressure in the current system, it is necessary to further increase the pressure of the gas turbine extraction air. For this reason, since the compressor power is too large and the temperature is limited by the material, the system becomes complicated for heat recovery. Furthermore, in the IGFC system, since the fuel gas pressure supplied from the gasifier varies, the differential pressure control becomes more difficult.

  Further, in the IGFC system in which the SOFC 30 is combined upstream of the gas turbine 40, the higher the fuel utilization rate in the SOFC 30, the higher the plant efficiency. However, since the system having the conventional configuration is subject to the first to third constraints described above, it is difficult to maximize the performance of the gas turbine 40 and the SOFC 30 simultaneously. For this reason, some measures are required, such as a new design dedicated to the IGFC in advance for components such as the gas turbine 40, or an additional device installed in the system.

Against this background, a gasified fuel cell combined power generation system that enables combined power generation with high plant efficiency by maximizing performance using existing technology gas turbines and the like by solving the above-described restrictions and operation thereof Development of a method is desired.
The present invention has been made in order to solve the above-described problems, and the object of the present invention is to provide a gas that can improve combined power generation efficiency using existing technologies such as a gas turbine used in IGCC and the like. An improved fuel cell combined power generation system and an operation method thereof are provided.

In order to solve the above problems, the present invention employs the following means.
The combined gasification fuel cell power generation system according to the present invention supplies a fuel gas obtained by gasifying a carbonaceous solid fuel in a gasification furnace and purified by a gas purification unit, and generates power by a solid oxide fuel cell, and a gas turbine. Power generation using a generator as a drive source of the generator, and power generation using a steam turbine operated by introducing steam generated by using the exhaust heat of the combustion exhaust gas discharged from the gas turbine as a drive source of the generator In the gasification fuel cell combined power generation system to be performed, the fuel gas supply system includes a fuel cell gas supply system in which the fuel gas is connected to a solid oxide fuel cell from the gas purification unit, and the fuel gas is supplied. The gas turbine gas supply system is connected to the gas turbine and supplies the fuel gas.

  According to such a gasification fuel cell combined power generation system, the fuel gas supply system includes a fuel cell gas supply system in which the fuel gas is connected to the solid oxide fuel cell from the gas purification unit and the fuel gas is supplied. And the gas turbine gas supply system that is connected to the gas turbine and supplies the fuel gas, so that the correlation of the fuel gas can be eliminated between the solid oxide fuel cell and the gas turbine. . That is, in the fuel gas supply system, the fuel cell gas supply system and the gas turbine gas supply system are provided in parallel. Therefore, in both the solid oxide fuel cell and the gas turbine, after purification after gasification in a gas furnace. It becomes possible to introduce and use fuel gas in each.

In the gasified fuel cell combined power generation system, the fuel cell gas supply system preferably includes a pressure regulator that supplies the solid oxide fuel cell with the fuel gas reduced to normal pressure. Thereby, the normal pressure operation of the solid oxide fuel cell becomes possible.
In this case, an expander may be employed as the pressure regulator to recover the power.

The gasification fuel cell combined power generation system includes an unburned gas combustor that burns unburned fuel gas discharged after power generation from the solid oxide fuel cell and discharges unburned gas combustion exhaust gas. It is preferable that the steam can be generated by effectively using the exhaust heat of the unburned gas combustion exhaust gas, and the plant efficiency can be improved.
In this case, a catalytic combustor may be employed as the unburned gas combustor.

  The operation method of the combined gasification fuel cell power generation system according to the present invention is to supply a fuel gas obtained by gasifying a carbonaceous solid fuel in a gasification furnace and purified by a gas purification unit, and generating power by a solid oxide fuel cell; A steam turbine that performs power generation using a gas turbine as a drive source of a generator and introduces and operates steam generated by using exhaust heat of combustion exhaust gas discharged from the gas turbine is used as a drive source of the generator An operation method of a combined gasification fuel cell power generation system that performs power generation, wherein the fuel gas supply system includes: a fuel cell gas supply system that connects the fuel gas from the gas purification unit to a solid oxide fuel cell; Operation is performed by branching to each of the gas turbine gas supply systems connected to the gas turbine and supplying the fuel gas to the solid oxide fuel cell and the gas turbine, respectively. And it is characterized in Rukoto.

  According to such an operation method of a gasification fuel cell combined power generation system, a fuel gas supply system includes a fuel cell gas supply system that connects the fuel gas from the gas purification unit to a solid oxide fuel cell, and a gas turbine. Branching to each of the gas turbine gas supply systems connected to the gas turbine, and supplying the fuel gas to the solid oxide fuel cell and the gas turbine for operation, respectively, between the solid oxide fuel cell and the gas turbine. The correlation of fuel gas can be eliminated. That is, in the fuel gas supply system, the fuel cell gas supply system and the gas turbine gas supply system are provided in parallel. Therefore, in both the solid oxide fuel cell and the gas turbine, after purification after gasification in a gas furnace. It becomes possible to introduce and use fuel gas in each.

  In the operation method of the gasified fuel cell combined power generation system described above, it is preferable that a pressure regulator is provided in the fuel cell gas supply system, and the fuel gas is reduced to normal pressure and supplied to the solid oxide fuel cell. As a result, the solid oxide fuel cell can be operated at normal pressure.

  In the operation method of the gasified fuel cell combined power generation system described above, an unburned gas combustor for combusting the unburned fuel gas discharged after power generation from the solid oxide fuel cell is provided, and is discharged from the gas turbine. It is preferable to operate by using the exhaust heat of the unburned gas combustion exhaust gas discharged from the unburned gas combustor for the generation of the steam. The plant efficiency can be improved.

  According to the present invention described above, since the fuel gas supply system of the solid oxygen fuel cell and the gas turbine is independent of each other, it becomes possible to maximize the performance using the gas turbine of the existing technology, Combined power generation with high plant efficiency can be realized. That is, without newly developing a dedicated gas turbine suitable for IGFC, for example, by using an existing gas turbine used in IGCC, it becomes possible to improve combined power generation efficiency.

It is a schematic block diagram which shows one Embodiment of the gasification fuel cell combined power generation system which concerns on this invention, and its operating method. It is a schematic block diagram which shows the conventional gasification fuel cell combined power generation system.

Hereinafter, an embodiment of a gasification fuel cell combined power generation system according to the present invention will be described with reference to the drawings.
The gasification fuel cell combined power generation system of this embodiment is a coal gasification fuel cell combined power generation system (hereinafter referred to as “IGFC”) that performs combined power generation using fuel obtained by gasifying coal (hydrocarbon fuel). And a fuel cell using fuel gas purified by gasification in a gasification furnace. The carbonaceous solid fuel gasified in the gasifier is not limited to the coal of the present embodiment. For example, biomass fuel such as thinned wood, waste wood, driftwood, grass, waste, sludge, tires, etc. It is also applicable to.

The IGFC shown in FIG. 1 supplies fuel gas obtained by gasifying coal in the gasification furnace 10 and refined by the gas purification unit 20, generating electricity by a solid oxide fuel cell (hereinafter referred to as “SOFC”) 30, A steam turbine 51 that performs power generation using the gas turbine 40 as a drive source of the generator G and introduces and operates steam generated by using exhaust heat of the combustion exhaust gas discharged from the gas turbine 40 is connected to the generator G. It is configured to perform combined power generation in combination with power generation as a drive source.
The coal gasification gas gasified in the gas furnace 10 becomes fuel gas used for the operation of the SOFC 30 and the gas turbine 40 by performing various processes such as desulfurization necessary in the gas purification unit 20.

This fuel gas is supplied to the SOFC 30 and the gas turbine 40 through the piping flow path of the fuel gas supply system F. More specifically, the fuel gas supply system F is connected to the SOFC 30 and supplied to the fuel cell gas supply system Fs for supplying fuel gas, and to the gas turbine 40 on the downstream side of the gas purification unit 20. It is branched into each of the gas turbine gas supply systems Fg for supplying gas.
The fuel cell gas supply system Fs is provided with a pressure regulator 31 on the upstream side of the SOFC 30. The pressure regulator 31 is a device that depressurizes the fuel gas to a normal pressure and supplies the fuel gas to the SOFC 30. For example, an expander that can recover power is suitable. The normal pressure is a pressure that takes into account the pressure loss of the downstream equipment at atmospheric pressure.

The SOFC 30 is supplied with fuel gas and an oxidant (for example, air or oxygen-enriched air) and generates power by an electrochemical reaction via an electrolyte. In the present embodiment, power generation by normal pressure operation is performed using fuel gas supplied at normal pressure via the pressure regulator 31 and air introduced from the atmosphere.
The fuel gas and air used for power generation in the SOFC 30 are discharged as exhaust gas including unburned fuel gas (combustible gas), and between the SOFC 30 and the exhaust heat recovery boiler (hereinafter referred to as “HRSG”) 50. Flows through the exhaust gas system Es connecting the two. The exhaust gas system Es is provided with an unburned gas combustor 32 so as to burn unburned fuel gas and discharge unburned gas combustion exhaust gas. In this case, the temperature of the unburned gas combustion exhaust gas may be increased to a temperature at which heat recovery by steam is possible (for example, about 600 ° C.).

The unburned gas combustion exhaust gas described above is supplied to the HRSG 50 together with the combustion exhaust gas of the gas turbine 40 described later. As a result, the unburned gas combustion exhaust gas is effectively used as a heat source for generating steam, which contributes to improvement in plant efficiency (power generation efficiency).
The unburned gas combustor 32 can also employ a catalyst combustor.

The gas turbine 40 includes a combustor 41, a compressor 42, and a turbine 43. The combustor 41 receives supply of compressed air directly from the compressor 42 and burns fuel gas to generate high-temperature and high-pressure combustion exhaust gas. When this combustion exhaust gas is supplied to the turbine 43, the turbine 43 is rotated to generate a shaft output. In this case, the pressure of the gas fuel supplied to the combustor 41 can be kept constant by installing the pressure regulating valve 44 on the upstream side of the combustor 41. Since the shaft output generated by the turbine 43 drives the generator G connected coaxially, power generation is performed using the gas turbine 40 as a drive source.
A part of the shaft output of the gas turbine 40 described above is used for continuous operation of the compressor 42.

Since the combustion exhaust gas that has worked in the turbine 43 still has a sufficient amount of heat, it is supplied to the HRSG 50 via the combustion exhaust gas system Eg. In the HRSG 50, the combustion exhaust gas supplied from the gas turbine 40 and the unburned gas combustion exhaust gas supplied from the unburned gas combustor 32 are used as heat sources, and heat is exchanged with water to generate steam. Since this steam is supplied to the steam turbine 51, power is generated by the generator G using the steam turbine 51 as a drive source. Further, the combustion exhaust gas and the unburned gas combustion exhaust gas used for generating steam are appropriately subjected to exhaust gas treatment as necessary, and then released from the chimney 52 to the atmosphere.
Although the illustrated generator G is coaxially connected to the gas turbine 40 and the steam turbine 51, a dedicated generator may be connected to the gas turbine 40 and the steam turbine 51 to generate power.

By the way, in the compressor 42 of the gas turbine 40 mentioned above, a part of compressed air is extracted. The air is boosted to a desired pressure by a bleed air booster 70 and supplied to the gasification furnace 10 to be used for coal gasification.
An oxygen production apparatus (hereinafter referred to as “ASU”) 60 is provided to produce oxygen and nitrogen (inert gas) used for coal gasification in the gasification furnace 10. The oxygen produced by the ASU 60 is merged with the air boosted by the extraction air booster 70 to be input into the gasification furnace 10 to be oxygen-enriched air used for gasification.

As described above, the IGFC of the present embodiment includes the fuel cell gas supply system Fs connected to the SOFC 30 for supplying the fuel gas from the fuel gas supply system F connected to the outlet of the gas purification unit 20, and the gas The fuel gas supply system is connected to the turbine 40 and is branched into each of the gas turbine gas supply systems Fg for supplying the fuel gas directly, and the fuel gas supply system connects the SOFC 30 and the gas turbine 40 in parallel.
Therefore, an operation method for supplying the fuel gas to the SOFC 30 and the gas turbine 40 is possible, and the correlation of the fuel gas between the SOFC 30 and the gas turbine 40 can be eliminated.

That is, since the fuel cell gas supply system Fs and the gas turbine gas supply system Fg are provided in parallel, the purified fuel gas gasified in the gas furnace 10 is introduced into both the SOFC 30 and the gas turbine 40, respectively. Operation is possible.
As a result, in the IGFC described in the related art, the calorific value of the fuel gas varies according to the power generation state of the SOFC 30 as in the case where unburned fuel gas discharged from the SOFC 30 is supplied to the gas turbine 40. There is nothing, and a stable calorific value can be maintained.

Also, the air used to burn the fuel gas in the combustor 41 of the gas turbine 40 is not directly introduced from the SOFC 30 for power generation, but is directly introduced from the compressor 42. The minimum oxygen concentration does not fall under the influence accompanying the.
Therefore, the 1st and 2nd restrictions regarding the gas turbine 40 are eliminated by making the fuel cell gas supply system Fs and the gas turbine gas supply system Fg in parallel.

Further, in order to branch the fuel gas supply system supplied from the gas purification unit 20 to the fuel cell gas supply system Fs and the gas turbine gas supply system Fg, the gas supply of the SOFC 30 and the gas turbine 40 is performed. It is important to adjust the gas pressure supplied for each system.
Therefore, in the present embodiment, the pressure regulator 31 for pressure reduction is installed in the fuel cell gas supply system Fs on the SOFC side, and the combustor 41 is installed in the gas turbine gas supply system Fg on the gas turbine 40 side. Since the pressure regulating valve 44 is installed at the inlet, the pressure control can be easily performed in the two branched gas supply systems. Further, since the SOFC 30 is generated by normal pressure operation, the third restriction relating to the SOFC 30 is also eliminated.

Moreover, the gas turbine gas supply system Fg mentioned above can employ | adopt the structure and operating method similar to the existing IGCC as it is about the electric power generation system by the gas turbine 40 to the HRSG 50 and the steam turbine 51. Therefore, there is an advantage that it is easy to remodel the IGFC by adding the SOFC 30 using the existing IGCC.
In other words, technically advanced IGCC plants can be easily remodeled into IGFC using existing IGCC in the future, so output and efficiency can be improved with minimum additional cost. It becomes possible.

  Specifically, for example, by using the equipment of an IGCC plant equipped with an air-blown gasification furnace 10 as it is and operating the gasification furnace 10 with oxygen blowing, the gasification furnace can be entered without changing the equipment size. Heat can be increased. Therefore, by changing the SOFC 30 corresponding to the increase in heat input in parallel with the gas turbine 40, it is possible to change the IGCC plant to the IGFC plant.

As described above, according to the above-described embodiment, the fuel gas supply systems of the SOFC 30 and the gas turbine 40 are independent from each other, and therefore, an operation that maximizes the performance using the gas turbine 40 of the existing technology is possible. Therefore, combined power generation with high plant efficiency can be realized. In other words, without newly developing a dedicated gas turbine 40 suitable for IGFC, for example, by diverting and using an existing gas turbine 40 used for IGCC as it is, It becomes possible to improve the combined power generation efficiency of IGFC by modifying the existing IGCC.
In addition, this invention is not limited to embodiment mentioned above, For example, the gasification furnace 10 is not limited to oxygen-enriched air blowing or oxygen blowing etc., For example, it can change suitably in the range which does not deviate from the summary. it can.

10 Gasifier 20 Gas Refiner 30 Solid Oxide Fuel Cell (SOFC)
31 Pressure regulator 32 Unburned gas combustor 40 Gas turbine 41 Combustor 42 Compressor 43 Turbine 44 Pressure regulating valve 50 Waste heat recovery boiler (HRSG)
51 Steam turbine 60 Oxygen production equipment (ASU)
70 Extraction Air Booster F Fuel Gas Supply System Fs Fuel Cell Gas Supply System Fg Gas Turbine Gas Supply System Es Exhaust Gas System Eg Combustion Exhaust System G Generator

Claims (6)

Supplying fuel gas obtained by gasifying a carbonaceous solid fuel in a gasification furnace and purified by a gas purification unit, power generation by a solid oxide fuel cell, power generation using a gas turbine as a drive source of the generator, and the gas turbine In a gasification fuel cell combined power generation system that performs power generation using a steam turbine that operates by introducing steam generated by using exhaust heat of combustion exhaust gas discharged from
The fuel gas supply system includes a fuel cell gas supply system in which the fuel gas from the gas purification unit is connected to the solid oxide fuel cell to supply the fuel gas, and a fuel turbine connected to the gas turbine. A gasification fuel cell combined power generation system, which is branched into a gas turbine gas supply system for supplying gas.   2. The gasification fuel cell according to claim 1, wherein the fuel cell gas supply system includes a pressure regulator that depressurizes the fuel gas to a normal pressure and supplies the fuel gas to the solid oxide fuel cell. Combined power generation system.   3. An unburned gas combustor that discharges unburned gas combustion exhaust gas by burning the unburned fuel gas discharged from the solid oxide fuel cell after power generation. A gasification fuel cell combined power generation system according to 1. Supplying fuel gas obtained by gasifying a carbonaceous solid fuel in a gasification furnace and purified by a gas purification unit, performing power generation by a solid oxide fuel cell and power generation using a gas turbine as a drive source of a generator, This is a method for operating a combined gasification fuel cell power generation system that performs power generation using a steam turbine that operates by introducing steam generated by using exhaust heat of combustion exhaust gas discharged from a gas turbine as a drive source of the generator. And
The fuel gas supply system is branched into a fuel cell gas supply system that connects the fuel gas from the gas purification unit to a solid oxide fuel cell and a gas turbine gas supply system that connects to the gas turbine, respectively.
A method for operating a combined gasification fuel cell power generation system, wherein the fuel gas is supplied to the solid oxide fuel cell and the gas turbine for operation.   5. The gasification fuel cell combined power generation according to claim 4, wherein a pressure regulator is provided in the fuel cell gas supply system, and the fuel gas is decompressed to a normal pressure and supplied to the solid oxide fuel cell. How to operate the system. An unburned gas combustor for burning the unburned fuel gas discharged after power generation from the solid oxide fuel cell is provided, and in addition to the combustion exhaust gas discharged from the gas turbine, the unburned gas combustor 6. The operation method of a gasification fuel cell combined power generation system according to claim 4, wherein the exhaust gas combustion exhaust gas discharged is used for generating the steam.

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