JP2000212580A - Integrated gasification fuel cell power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an integrated gasification fuel cell power generation system generating electricity by utilizing carbon dioxide obtained secondarily in wet fine desulfurization for a fuel cell. SOLUTION: This integrated gasification fuel cell power generation system where a fused carbonate fuel cell is incorporated into an integrated gasification combined cycle is operated as follows: (1) sulfur content in gasified gas generated is desulfurized in a wet fine desulfurizer 13; (2) carbon dioxide absorbed in a desulfurizing fluid of the desulfurizer is separated to be fed to the cathode 21 of a fuel cell 20, and part of gasified gas after desulfurized is fed to the anode 22; (3) exhaust gas discharged from the anode is returned to the desulfurizer through a water scrubber such as a wet deduster 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined gasification fuel cell power generation system in which a fuel cell is incorporated into a combined gasification fuel cell system.

[0002]

2. Description of the Related Art In an integrated gasification combined cycle system (IGCC), gasification gas (H ₂ , CO ₂ ) is generated by supplying coal slurry (or heavy oil + steam) and oxygen to a gasification furnace. After refining this, it is supplied to a combined cycle to generate electric power by the gas turbine, and heat generated by the gas turbine and heat collected by the gasifier are collected by a waste heat boiler to generate electric power.

[0003] A gasification fuel cell combined cycle system (IGFC) in which a molten carbonate fuel cell (MCFC) is incorporated in the IGCC has been studied.

[0004]

In this IGFC, the hydrogen to be supplied to the anode of the molten carbonate fuel cell may be obtained by purifying the hydrogen generated in the gasification furnace of the IGCC and supplying it. Supply carbon dioxide (C
The challenge is where to supply O ₂ ) and air from the system, and how to treat anode exhaust gases exhausted from the anode.

Usually, carbon dioxide gas required for the cathode may be supplied mainly by burning anode exhaust gas, but the H ₂ utilization at the anode of the fuel cell is 80% or less. As a result, more than 20% of the combustion heat is only recovered.

In the system for directly supplying the anode exhaust gas to the gas turbine, the carbonate of the fuel cell may be mixed in the anode exhaust gas, so that it is expected that the gas turbine will be adversely affected.

On the other hand, in IGCC, wet precision desulfurization using an amine-based desulfurization liquid has been widely adopted for the removal of H ₂ S contained in gasified syngas from the comprehensive evaluation of results and economics. I have. However, the amine-based desulfurization liquid absorbs more carbon dioxide in the gasification gas as the desulfurization rate increases, so that increasing the desulfurization rate relatively decreases the amount of gasification gas, This will reduce plant efficiency. Further, the sulfur content and the carbon dioxide absorbed in the desulfurization solution are separated thereafter, but it is not environmentally preferable to discharge the separated and concentrated carbon dioxide as it is.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a gasification fuel cell combined power generation system for generating electric power by utilizing carbon dioxide gas obtained as a secondary by wet precision desulfurization for a fuel cell. It is in.

[0009]

Means for Solving the Problems To achieve the above object, the invention of claim 1 has been developed in a combined gasification fuel cell combined power generation system in which a molten carbonate type fuel cell is incorporated in a combined gasification combined power generation system. Sulfur content in gasification gas,
Desulfurization is performed by wet precision desulfurization, carbon dioxide absorbed in the desulfurization liquid is separated and supplied to the cathode of a molten carbonate fuel cell, and a part of the gasified gas after desulfurization is supplied to the anode. This is a gasified fuel cell combined power generation system in which anode exhaust gas discharged from the system is returned to wet precision desulfurization through a water scrubber such as wet dust removal.

[0010] According to a second aspect of the present invention, the generated gasified gas is supplied from the wet dust removing section to the wet precision desulfurizing section through the COS conversion and ammonia removing section, and the anode exhaust gas is supplied to the wet dust removing section or the ammonia removing section. The combined gasification fuel cell power generation system according to claim 1, wherein the system is returned to a water scrubber.

According to a third aspect of the present invention, the carbon monoxide and the vapor in the gasified gas supplied to the anode are reformed into hydrogen and carbon dioxide using a catalyst and supplied to the anode as a hydrogen-rich gas. It is a gasification fuel cell combined cycle system.

According to a fourth aspect of the present invention, the high-pressure hydrogen-rich gas is expanded by an expander and supplied to the anode, and the anode exhaust gas is pressurized by a compressor connected to the expander to increase the pressure of the wet exhaust gas or the ammonia removal. The combined gasification fuel cell power generation system according to claim 2, wherein the system is returned to the water scrubber.

According to a fifth aspect of the present invention, there is provided the combined gasification fuel cell power generation system according to the first aspect, wherein the pressure of the carbon dioxide gas separated from the desulfurization solution is increased, and the mixed gas is supplied to the cathode after being mixed with the increased air.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows an integrated gasification combined cycle system (IGC).
C), a combined gasification fuel cell power generation system (IGF) of the present invention in which a molten carbonate fuel cell (MCFC) is incorporated.
FIG. 3C shows a block diagram.

Referring to FIG. 1, first, the IGCC will be described.

Coal slurry (or heavy oil + steam) and oxygen separated by an air separation unit (AUS) are supplied to a fuel gasification section 10 composed of a gasification furnace, and H ₂ , CO, etc. are supplied. Is generated. The crude gas is removed of solids and the like through a water scrubber in a wet dust removing section 11, and then COS (carbonyl sulfide) and ammonia contained in the crude gas are converted into COS conversion and a catalyst tower in an ammonia removing section 12. By passing through the scrubber, COS and steam are reformed into hydrogen sulfide and carbon dioxide, and ammonia is absorbed.

Next, hydrogen sulfide (H ₂ S) in the crude gas is removed from the crude gas in a wet precision desulfurization unit 13 using an amine-based desulfurization solution, and at the same time, carbon dioxide gas contained in the crude gas is converted into a desulfurization solution. Absorbed.

The crude gas desulfurized in the wet precision desulfurization section 13 is called a purified gas, supplied to a combined cycle 16 composed of a gas turbine through a purified gas branch section 14 and a purified gas heating section 15, and used for power generation.

The combustion exhaust gas from the gas turbine is supplied to an exhaust heat recovery boiler (HRSG), and the boiler water from the exhaust heat recovery boiler (HRSG) is supplied to a fuel gasification section 10.
Is supplied to the steam turbine via the HRSG to generate power.

The removal of the crude gas in the wet dust removal section 11 is as follows.
The crude gas passes through the water scrubber with the washing water supplied from the ash water separation unit 17 to remove solids and the like, and the COS conversion and ammonia removal unit 12 similarly removes the ash water separation unit 17.
A scrubber is formed with the wash water supplied from the plant where ammonia is absorbed.

The solids removed in the wet dust removal section 11 and the ammonia recovered in the COS conversion and ammonia removal section 12 are separated in the ash water separation section 17. First, solid-liquid separation is performed to remove solid components. In the liquid in this solid-liquid separation,
Ammonia, carbon dioxide, hydrogen sulfide, etc. are dissolved, and are degassed and supplied to a sulfur recovery section 18 together with a desulfurization off-gas (H ₂ S, CO ₂ ) separated in a wet precision desulfurization section 13 to recover sulfur. The unit 18 collects sulfur and separates carbon dioxide gas and the like as exhaust gas.

In the present invention, when incorporating the molten carbonate fuel cell 20 into the IGCC, the carbon dioxide gas separated from the sulfur recovery section 18 is supplied to the cathode 21 of the fuel cell 20 together with the atmosphere (air) A, The anode gas is
The purified gas branched at the purified gas branching section 14 is supplied to the anode 22 as a H ₂ -rich gas through the CO shift section 19, and the anode exhaust gas is subjected to the wet dust removal section 11 or COS
This is to return to the conversion and ammonia removal unit 12.

First, although not shown in detail, the molten carbonate fuel cell 20 is formed by sandwiching an electrolyte tile between an anode electrode and a cathode electrode, and stacking this in a multi-stage manner with a separator for dividing the anode chamber and the cathode chamber. The laminated body is formed in a sealed container.

The purified gas generated by the IGCC and desulfurized in the wet precision desulfurization section 13 is branched in a purified gas branch section 14 and partly supplied to a CO shift section 19. Since the purified gas contains CO unnecessary for the reaction in the fuel cell 20, steam S is supplied to the CO shift unit 19 to reform CO and steam into hydrogen and carbon dioxide using a catalyst. Since this shift reaction is an exothermic reaction, it can be heated with H ₂ rich gas.

The H ₂ -rich gas generated in the CO shift unit 19 has an IGCC operating pressure of 20 to 30 atm.
Since the operating pressure of the fuel cell 20 is about 3 atm, the H ₂ -rich gas from the CO shift unit 19 is sent to the expander 24 via the line 23 to expand and reduce the pressure, and the fuel is passed through the anode gas gas heat exchanger 26 from the line 25. Battery 20
To the anode 22.

On the other hand, the gas containing a large amount of carbon dioxide discharged from the sulfur recovery section 18 is supplied from the line 27 to the compressor 2.
8 and mixed with the air A pressurized by the compressor 29 and passed through the steam gas heater 31 through the line 30 where it is heated by the steam from the HRSG and further heated by the GT exhaust gas heater 32 in the HRSG. , And further heated through the cathode gas heat exchanger 33 and supplied to the cathode 21 of the fuel cell 20.

In the fuel cell 20, the anode gas and the cathode gas supplied to the anode 21 and the cathode 22 react via the electrolyte tile to generate power.

At this time, a part of the cathode exhaust gas is recycled to the cathode 21 through a line 34 through a heat recovery unit 35 and a compressor 36, and the remainder is discharged into a waste heat recovery boiler (HRSG) through a cathode gas heat exchanger 33. )
And exhausted after heat recovery.

The anode exhaust gas is supplied from line 37
After the heat is recovered through the anode gas gas heat exchanger 26, the pressure is raised to the operating pressure of the IGCC by the compressor 38 connected to the expander 24, and the pressure is increased from the anode recycle gas line 39 to the wet dedusting unit 11 or the line 39. It is returned to the COS conversion and ammonia removal unit 12 via 40.

Since the pressure increase by the compressor 38 cannot be covered by the expansion energy of the H ₂ -rich gas passing through the expander 24, the shortage is made up by the motor 41.

In the above, when precision desulfurization is performed in the wet precision desulfurization unit 13 using an amine-based desulfurization solution, when the desulfurization rate is increased, a large amount of carbon dioxide gas is absorbed into the desulfurization solution along with hydrogen sulfide in the gasified gas. Therefore, by supplying the exhaust gas after sulfur recovery of the sulfur recovery unit 18 which becomes a gas containing a large amount of carbon dioxide to the cathode 21 of the fuel cell 20, the carbon dioxide gas can be effectively used while increasing the desulfurization rate, and High efficiency can be maintained.

The hydrogen generated in the IGCC is expanded by an expander 24 and supplied to the anode 22 of the fuel cell 20. The anode exhaust gas is recovered after heat recovery.
The pressure is increased by the compressor 38 connected to the
1 or by returning to the COS conversion and ammonia removal unit 12 and mixing it with the crude gas, the hydrogen utilization rate in the fuel cell 20 can be set low. In addition, since carbonate is considered to be mixed in the anode exhaust gas in addition to unreacted hydrogen, the carbonate is removed by passing this through a water scrubber in a dust removing section 11 or a COS conversion and ammonia removing section 12. This can prevent problems when supplying to the GT.

Further, when the concentration of carbon dioxide in the crude gas increases due to the anode exhaust gas, the amount of carbon dioxide recovered during desulfurization also increases, so that the capacity and efficiency of the fuel cell 20 can be increased.

[0035]

In summary, according to the present invention, it is possible to effectively use carbon dioxide gas, which has been secondaryly recovered by wet precision desulfurization of gasified gas, in a fuel cell and to remove anode exhaust gas from a water scrubber such as a dust removing section. By circulating the gas into the gasified gas, even if the hydrogen utilization rate of the fuel cell is reduced, the overall plant efficiency is not affected, and as a result, effective utilization of hydrogen can be achieved. Further, by passing the anode exhaust gas through a water scrubber, the carbonate contained in the gas can be removed, so that the GT is not adversely affected.

[Brief description of the drawings]

FIG. 1 is a block flow diagram showing an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 fuel gasification unit 11 wet dust removal unit 12 COS conversion unit and ammonia removal unit 13 wet precision desulfurization unit 18 sulfur recovery unit 20 molten carbonate fuel cell 21 cathode 22 anode 39 anode recycle gas line

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C10K 1/34 C10K 1/34 3/04 3/04 H01M 8/00 H01M 8/00 A 8/04 8 / 04 J 8/06 8/06 R 8/14 8/14

Claims (5)

[Claims] 1. A gasification combined cycle power generation system in which a molten carbonate fuel cell is incorporated in a combined gasification combined cycle system, desulfurization of sulfur in the generated gasified gas by wet precision desulfurization, and the desulfurization liquid The carbon dioxide gas absorbed therein is separated and supplied to the cathode of the molten carbonate fuel cell, and a part of the gasified gas after desulfurization is supplied to the anode. The anode exhaust gas discharged from the anode is subjected to wet degassing. A gasification fuel cell combined cycle system characterized by returning to wet precision desulfurization through a water scrubber such as dust. 2. The generated gasified gas is discharged from
The combined gasification fuel cell power generation system according to claim 1, wherein the anode exhaust gas is supplied to the wet precision desulfurization unit through the OS conversion and ammonia removal unit, and the anode exhaust gas is returned to the water scrubber in the dust removal unit or the ammonia removal unit. 3. The gasified fuel cell composite according to claim 1, wherein carbon monoxide and vapor in the gasified gas supplied to the anode are reformed into hydrogen and carbon dioxide using a catalyst and supplied to the anode as a hydrogen-rich gas. Power generation system. 4. The high-pressure hydrogen-rich gas is expanded by an expander and supplied to an anode, and the anode exhaust gas is pressurized by a compressor connected to the expander and returned to a wet dust removing section or an ammonia removing section. The combined gasification fuel cell power generation system according to the above. 5. The gasification fuel cell combined cycle system according to claim 1, wherein the pressure of the carbon dioxide gas separated from the desulfurization liquid is increased, and the mixed gas is mixed with the increased air and supplied to the cathode.