JP2003036876A - Molten carbonate type fuel cell power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate electricity without discharging cathode exhaust gas to atmosphere as highly concentrated CO2 gas. SOLUTION: A reformer 10 is installed at the each entrance side of a cathode 2 and an anode 3 of a fuel cell I. Natural gas NG is reformed at the chamber of the reformer 10 to supply to the anode 3 as a fuel gas. An anode exhaust gas and a high-dens oxygen produced at an oxygen production facility 32 are supplied to the combustion chamber of the reformer 10. An exhaust gas burned at the combustion chamber of the reformer 10 is supplied to the cathode 2. An exhaust heat recovery boiler 29, cooling apparatus 30, CO2 recovery system 31 are provided on a cathode exhaust gas line 28 in order from upper stream. CO2 is recovered by removing H2 O from cathode exhaust gas that becomes only CO2 and H2 O.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power generation device for a molten carbonate fuel cell among fuel cells used in the energy sector for directly converting chemical energy of fuel into electric energy.

[0002]

2. Description of the Related Art In a molten carbonate fuel cell, an electrolyte plate (tile) made by impregnating a molten carbonate as an electrolyte into a porous material is used as both a cathode (oxygen electrode) and an anode (fuel electrode). One cell is sandwiched from both sides, and one cell is configured to generate power by supplying an oxidizing gas to the cathode side and a fuel gas to the anode side to cause the cathode and the anode to react with each other. Are laminated in multiple layers via a separator to form a stack.

As a power generator using a molten carbonate fuel cell having such a structure, a system system configuration as shown in FIG. 3 is available as a power generation device using natural gas as a fuel.

That is, after the cells are compressed by the compressor 4, the cathode 2 of the fuel cell I is constructed by stacking cells in which the electrolyte plate 1 is sandwiched by both electrodes of the cathode 2 and the anode 3 via the separator. The air A cooled by the cooler 5 and further compressed by the compressor 6 is preheated by the air preheater 7 and supplied by the air supply line 8, and a part of the air A is branched by the branch line 9 in the reformer 10. The cathode exhaust gas, which is supplied to the combustion chamber and is discharged from the outlet side of the cathode 2, is introduced into the turbine 12 through the cathode exhaust gas line 11 to drive the turbine 12, and then released into the atmosphere through the air preheater 7. I am doing it. on the other hand,
In the anode 3 of the fuel cell I, natural gas NG is introduced into the reforming chamber of the reformer 10 via the natural gas preheaters 13 and 14 and the desulfurizer 15 to be reformed, and then the reformed gas is used as the fuel gas FG. The anode exhaust gas discharged from the outlet of the anode 3 while being supplied from the fuel gas supply line 16 is used as the heat exchanger 1.
7. After passing through the natural gas preheater 14, the evaporator 18, and the natural gas preheater 13, the condenser 19 cools and condenses and guides them to the gas-liquid separator 20, where the water in the anode exhaust gas is separated. The gas containing CO ₂ , CO ₂ is pressurized by the blower 21, and is then heat-exchanged with the anode exhaust gas by the heat exchanger 17 through the line 22 and then introduced into the combustion chamber side of the reformer 10 from the reformer 10. The exhaust combustion exhaust gas is combined with the air A and supplied to the cathode 2. Further, the water 23 separated by the gas-liquid separator 20 is pressurized by the pump 24 and sent to the feed water heater 25, where it is heated and becomes steam as steam through the steam line 26 to the evaporator 18 and the reformer. It is supplied with natural gas NG to 10 reforming chambers, and steam reforming is performed.

[0005]

However, in the conventional molten carbonate fuel cell power generator, air A is used as the oxidizing gas to be supplied to the cathode 2 as described above, and CO ₂ +1 is provided on the cathode 2 side. / 2O ₂ + 2e ⁻ → CO ₃ ⁻⁻ is performed, and the reaction of CO ₃ ⁻⁻ + H ₂ → H ₂ O + CO ₂ + 2e ⁻ is performed on the anode 3 side, and the cathode 2 side and anode 3 side Electric power is generated by the progress of the reaction. In the case of the conventional molten carbonate fuel cell, the anode exhaust gas containing CO ₂ obtained by the reaction at the anode 3 is converted into water H _{2 by the} gas-liquid separator 20. since O from being separated is combusted is led into the combustion chamber of the reformer 10, it is possible to reduce the CO ₂ emissions per power generation by the power generation efficiency is improved, it is zero The flaws are discharged to the atmosphere, and the air branched and introduced into the combustion chamber of the reformer 10 contains nitrogen. Therefore, the combustion temperature in the combustion chamber of the reformer 10 is high. Case (especially when the burner burns at startup)
May generate NO ₂ .

As described above, the exhaust gas of the conventional molten carbonate fuel cell has low NO _x and low CO ₂ , but the emission of air pollutants is not zero, and the exhaust gas is emitted to the atmosphere. I also needed a chimney.

Therefore, in the present invention, the cathode exhaust gas is made into a high-concentration CO ₂ gas and CO ₂ is recovered to eliminate the atmospheric emission of air pollutants, and to use nitrogen gas for barge and battery holding. It is intended to provide a molten carbonate fuel cell power generation device that can be covered by what is obtained in the system.

[0008]

In order to solve the above-mentioned problems, the present invention has a reformer installed at the inlet side of the cathode and anode of a molten carbonate fuel cell, and the reformer of the reformer is installed. While supplying the fuel gas reformed in the chamber to the anode,
In a molten carbonate fuel cell power generator configured to supply the exhaust gas discharged from the combustion chamber of the reformer to the cathode, a high concentration oxygen and the total amount of anode exhaust gas are supplied to the combustion chamber of the reformer. So that the inlet side of the combustion chamber of the reformer is connected to the high-concentration oxygen supply line extracted from the oxygen production facility and the anode exhaust gas line connected to the outlet side of the anode, and to the outlet side of the cathode. In the connected cathode exhaust gas line, an exhaust heat recovery boiler, a cooling device that cools H ₂ O in the cathode exhaust gas to recover it as water, and a CO ₂ gas that has exited the cooling device are collected in order from the upstream side. and a CO ₂ recovery facility to further the steam obtained by water some of the water recovered by the cooling device to the exhaust heat recovery boiler, is introduced into the reforming chamber inlet side of the reformer Yo C and exiting the cooling device
A part of the O ₂ gas is returned from the outlet side of the cooling device to the cathode inlet side, and a part of the CO ₂ gas exiting the cooling device is fed from the outlet side of the cooling device to the cathode inlet side. instead of was made in the back to the side structure, a structure to allow a portion of the CO ₂ gas recovered by the CO ₂ recovery facility returned to the cathode inlet side.

Since the high-concentration oxygen taken out from the oxygen production facility and the anode exhaust gas are all burned in the combustion chamber of the reformer and discharged from the combustion chamber are supplied to the cathode of the fuel cell as oxidizing gas. , C in the reaction at the cathode
O ₂ and high concentration _{O 2} is used, the cathode exhaust gas to be consequently discharged from the cathode may be only CO ₂ and _{H 2} O, and separating the CO ₂ and _{H 2} O, _{H 2} O can be cooled and recovered as water, and CO ₂ can be recovered by a CO ₂ recovery facility, and emission to the atmosphere can be reduced to zero.

Further, since the gas returned to the cathode for cooling the cathode is CO ₂ gas, the CO ₂ concentration on the cathode side can be increased.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.
Then, the electrolyte plate 1 is connected to the cathode 2 and the anode 3 from both sides.
It is sandwiched between the two and supplies the oxidizing gas to the cathode 2 side, and
Separate the cell configured to supply fuel gas to the
Molten carbonate type fuel that is laminated as a stack
Fuel cell (hereinafter simply referred to as fuel cell) I
A reformer 10 is installed on the inlet side of both electrodes of the cathode 2 and the anode 3.
Place the natural gas NG as the reforming raw material gas in the desulfurizer 2
After desulfurization in 7, reformer in the reformer 10 reformer
It is supplied as anode FG to the anode 3 and reformed.
The combustion exhaust gas discharged from the combustion chamber of the reactor 10 to the cathode 2
High concentration oxygen in the above configuration.
Anode exhaust gas is supplied to the combustion chamber of the reformer 10
The reformer 1 is introduced into the combustion chamber and burned, and the reformer 1
High concentration O from 0 combustion chamber_TwoAnd CO _TwoAnd H_TwoO is caustic
Supply to the cathode 2 and the outlet side of the cathode 2
The exhaust heat recovery boiler is connected to the cathode exhaust gas line 28 connected to the
LA 29, cooling device 30, CO _TwoUpstream of the recovery facility 31
From the cathode 2 at high temperature _Two
And H_TwoVapor H in cathode exhaust gas consisting of O only_TwoO
CO by removing and recovering_TwoCollected and released into the atmosphere
Try not to let it.

More specifically, in the combustion chamber of the reformer 10, a high-concentration oxygen O ₂ supply line 3 produced by the oxygen production facility 32 is provided.
3, the anode exhaust gas line 34 connected to the outlet side of the anode 3 of the fuel cell I, and the natural gas supply branch line 36 branched from the downstream side of the desulfurizer 27 of the natural gas supply line 35 are connected to produce oxygen. Oxygen in the air is taken out by the equipment 32 and the reformer 1 is supplied by the high-concentration oxygen supply line 33.
Nitrogen N
₂ as previously housed in nitrogen tank 37, to allow the use of N ₂ gas of nitrogen tank 37 without using purchased when requiring a large amount of N ₂ gas as purge, etc. .

Combustion chamber outlet side of the reformer 10 and the fuel cell
The inlet side of the cathode 2 of I is through a combustion exhaust gas line 38.
Then connect the high concentration oxygen and some natural gas or anode
The exhaust gas after burning the exhaust gas is supplied to the cathode 2.
And CO emitted from the cathode 2_TwoAnd H_Two
Cathode exhaust gas containing only O
Use the exhaust heat recovery boiler 29 in the middle of the in 28 to generate steam.
Then, in the cooling device 30, a low temperature N described later_TwoWith gas
Steam H_TwoRemove O as water
High concentration of CO_TwoGas only, high concentration CO_TwoPart of
Is C for cooling the cathode from the outlet side of the cooling device 30.
O_TwoTake out to line 39_TwoHalfway line 39
CO_TwoThe compressor 53 boosts the pressure and returns it to the cathode 2 inlet side.
And high concentration CO_TwoThe rest of the CO_TwoRecovery
By sending it to the equipment 31 and compressing it with a compressor here
High concentration of CO_TwoCO,_TwoBy collection line 40
CO _TwoEither store it in the tank 41 or store it.
Ruiha CO_TwoProviding to user industries or disposing to the ocean
In this way, the release to the atmosphere is made zero.

The steam generated by the heat of the cathode exhaust gas in the exhaust heat recovery boiler 29 is supplied to the inlet side of the reforming chamber of the reformer 10 through the steam line 42 as the reforming steam. The water supplied to the exhaust heat recovery boiler 29 is separated and removed from the cathode exhaust gas by the cooling device 30 so that a part of the water recovered from the drain line 43 can be used. The drainage line 43 is connected to the water supply line 44 so that the remaining water can be used as makeup water.

Further, on the cathode 2 side and the anode 3 side of the fuel cell I, bypass lines 47 and 48 having open / close valves 45 and 46 respectively are provided on the way, and a connecting portion between the cathode exhaust gas line 28 and the bypass line 47 is provided. An on-off valve 49 and a control valve 50 are provided on the upstream side and the downstream side, and an on-off valve 51 and a control valve 52 are provided on the upstream side and the downstream side of the connecting portion between the anode exhaust gas line 34 and the bypass line 48, respectively.

Reference numeral 54 is a pressure vessel containing the fuel cell I, 55 is an anode blower provided in the anode exhaust gas line 34, 56, 57, 58, 59 and 60 are control valves, and 61.
Is a pump.

In the initial stage of starting the reformer 10, the oxygen production facility 3 is used.
The high concentration oxygen produced in 2 is supplied from the supply line 33 to the reformer 1
0 to the combustion chamber, and part of the natural gas NG is supplied from the natural gas supply branch line 36 and burned by the burner, and the natural gas NG introduced into the reforming chamber of the reformer 10 is subjected to an endothermic reaction. The fuel gas FG is reformed and supplied to the anode 3 side, while the combustion exhaust gas discharged from the combustion chamber of the reformer 10 is supplied to the cathode 2 side. At this time, since what is supplied to the combustion chamber of the reformer 10 is high-concentration oxygen and contains almost no nitrogen, there is no possibility of NO _x generation during burner combustion.

At the time of starting the fuel cell I, the cathode 2 and the anode 3 are heated by a heater, and the bypass lines 47 and 48 are opened during that time, and the combustion exhaust gas of high-concentration oxygen as the oxidizing gas is discharged to the cathode 2 side. The fuel gas FG is bypassed through the bypass line 47.
The bypass line 48 on the anode 3 side is used for bypass.

Under normal operating conditions, the natural gas supply
The control valve 58 of the branch line 36 is closed, and the bypass line 4
Both 7, 48 are closed, and the oxidizing gas of the reformer 10
Burns combustion exhaust gas containing high-concentration oxygen discharged from the combustion chamber
Of the reformer 10 while supplying it to the cathode 2 of the fuel cell I.
Fuel gas F obtained by reforming natural gas NG in the reforming chamber
G is supplied to the anode 3, and the cathode 2 and the anode 3
Each of them causes a battery reaction to generate power, and
CO discharged from node 3_TwoAnd H_TwoAnode containing O
The exhaust gas is passed through the anode exhaust gas line 34 and the anode exhaust gas is discharged.
The lower pressure boosts the pressure and sends it to the combustion chamber of the reformer 10,
High-concentration oxygen O from supply line 33_TwoBurn with
The combustion exhaust gas as an oxidizing gas to the cathode 2.
It The oxidizing gas supplied to the cathode 2 is as described above.
Since it was burned with high concentration oxygen,
The cathode exhaust gas discharged from the cathode 2 is the conventional oxidizing gas.
When using air and combustion exhaust gas from the reformer as
Higher concentration CO compared to_TwoAnd steam H _TwoO only.
This cathode exhaust gas is first treated with water in the exhaust heat recovery boiler 29.
After being used to generate steam, it is sent to the cooling device 30, where
And low temperature N_TwoThe gas can be used to cool the cathode exhaust gas.
And CO_TwoAnd H_TwoExhaust of cathode only O
Vapor H in gas_TwoO is cooled to water and the water is drained.
The waste heat recovery boiler 29
To be used as water supply to On the other hand, used for cooling
N_TwoThe gas should be released to the atmosphere.

Low temperature N ₂ used for cooling in the cooling device 30
As the gas, the low temperature N ₂ gas obtained when the high concentration oxygen is produced in the oxygen production facility 32 is used.

H in the exhaust gas of the cathode is cooled by the cooling device 30.
When _{2 O} is recovered is cooled as water, cathode exhaust is only the high concentration of CO ₂ gas, a part is pressurized by CO ₂ compressor 53 is taken out to the CO ₂ line 39 for the cathode cooling the cathode 2 Back to CO, the rest is CO
_{2 By} introducing it into the recovery facility 31 and compressing it with a compressor, it is recovered as high-concentration CO ₂ gas, stored in the CO ₂ tank 41 for storage, and provided to customers and disposed on the seabed. To do so. This makes it possible to reduce the emission of air pollutants to zero without releasing CO ₂ gas to the atmosphere.

Next, FIG. 2 shows another embodiment of the present invention. After cooling the cathode exhaust gas with the cooling device 30, the vapor H ₂ O is recovered as water, and then only the CO ₂ gas is obtained. CO ₂ line 3
9 instead of the configuration of FIG. 1 to return to the cathode 2 through is obtained by returned to the cathode 2 takes out the CO ₂ gas stored in CO ₂ tank 41. The other configurations are the same as those shown in FIG. 1, and the same components are designated by the same reference numerals.

With such a configuration, the same effects as those of the embodiment shown in FIG. 1 can be obtained, and it is not necessary to branch the CO ₂ line 39 from the cathode exhaust gas line 28, and all the CO ₂ gas can be converted to CO _{2. 2} It can be guided to the recovery facility 31 and recovered.

[0025]

As described above, according to the molten carbonate fuel cell power generator of the present invention, the reformer is installed at the inlet side of the cathode and the anode of the molten carbonate fuel cell, and the reformer is installed. Carbon dioxide fuel cell power generation in which the fuel gas reformed in the reformer chamber of the reformer is supplied to the anode and the combustion exhaust gas discharged from the combustion chamber of the reformer is supplied to the cathode In the apparatus, a high-concentration oxygen supply line taken out from an oxygen production facility is provided at the inlet side of the reformer combustion chamber to supply high-concentration oxygen and the total amount of anode exhaust gas to the combustion chamber of the reformer, and the anode. of connecting the anode exhaust gas line connected to the outlet side, and to the cathode of the outlet side cathode exhaust gas line connected to the exhaust heat recovery boiler in order from the upstream side, of H _{2 O} in the cathode exhaust gas is cooled by water A cooling device so as to recover, and a CO ₂ recovery facility for recovering CO ₂ gas exiting the cooling device, further water a portion of the water recovered by the cooling device to the exhaust heat recovery boiler The steam thus obtained is introduced into the reforming chamber inlet side of the reformer, and part of the CO ₂ gas exiting the cooling device is returned from the outlet side of the cooling device to the cathode inlet side. In this way,
Some of the CO ₂ gas exiting the cooling unit instead be configured to become in the back to the cathode inlet side from the outlet side of the cooling device, part of the CO ₂ gas recovered by the CO ₂ recovery facility Since it is configured to return to the cathode inlet side, the cathode exhaust gas can be made into a high-concentration CO ₂ gas and can generate electricity without releasing the high-concentration CO ₂ gas into the atmosphere. CO ₂ with high concentration and no dust
CO can be recovered and provided to the CO ₂ utilization industry, and the CO required for the molten carbonate fuel cell power generator is required.
It is possible to cover the ₂ gases with the recovered CO ₂ gas, and since the high-concentration oxygen is supplied to the combustion chamber of the reformer for combustion, the nitrogen gas obtained by the production of the high-concentration oxygen is supplied to the fuel cell. It can be used for purging of batteries, storage of batteries, etc., eliminating the need to purchase N ₂ gas for these purposes, and further supplying air as oxidizing gas to the cathode. Compared with the method, it is possible to achieve excellent effects such as downsizing of equipment.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a molten carbonate fuel cell power generator of the present invention.

FIG. 2 is a schematic diagram showing another embodiment of the molten carbonate fuel cell power generator of the present invention.

FIG. 3 is a schematic diagram showing an example of a conventional molten carbonate fuel cell power generator.

[Explanation of symbols]

I fuel cell 1 electrolyte plate 2 cathode 3 anode 10 reformer 28 cathode exhaust gas line 29 exhaust heat recovery boiler 30 cooling device 31 CO ₂ recovery facility 32 oxygen production facility 33 supply line 34 anode exhaust gas line 38 combustion exhaust gas line 39 CO ₂ line 40 CO ₂ recovery line 42 Steam line 43 Drain line NG Natural gas FG Fuel gas

Claims (2)

[Claims] 1. A reformer is installed on the inlet side of a cathode and an anode of a molten carbonate fuel cell, and the fuel gas reformed in a reforming chamber of the reformer is supplied to the anode.
In a molten carbonate fuel cell power generator configured to supply the exhaust gas discharged from the combustion chamber of the reformer to the cathode, a high concentration oxygen and the total amount of anode exhaust gas are supplied to the combustion chamber of the reformer. So that the inlet side of the combustion chamber of the reformer is connected to the high-concentration oxygen supply line extracted from the oxygen production facility and the anode exhaust gas line connected to the outlet side of the anode, and to the outlet side of the cathode. In the connected cathode exhaust gas line, an exhaust heat recovery boiler, a cooling device that cools H ₂ O in the cathode exhaust gas to recover it as water, and a CO ₂ gas that has exited the cooling device are collected in order from the upstream side. and a CO ₂ recovery facility to further the steam obtained by water some of the water recovered by the cooling device to the exhaust heat recovery boiler, is introduced into the reforming chamber inlet side of the reformer Yo C and exiting the cooling device
A molten carbonate fuel cell power generator, wherein a part of O ₂ gas is returned from the outlet side of the cooling device to the cathode inlet side. 2. A Instead of a portion of the CO ₂ gas exiting the cooling device has a structure formed by the back to the cathode inlet side from the outlet side of the cooling device, CO ₂ recovered by the CO ₂ recovery facility The molten carbonate fuel cell power generator according to claim 1, wherein a part of the gas is returned to the cathode inlet side.