JPH03236166A - Power generating method for molten carbonate fuel cell - Google Patents

Abstract

PURPOSE:To decrease the steam quantity generated for reformation, miniaturize a steam generator, and reduce consumed energy by using the steam separated from anode gas as part of the steam for reforming the reform raw material gas. CONSTITUTION:Part of the steam in the anode gas AG cooled and discharged from the anode 3 of a fuel cell 1 via heat exchangers 24, 26 and a shift reactor 25 is permeated and separated by a separation film type steam separating device 27 and recovered to the permeation side 27a. Carbon dioxide and moisture S are further removed from the remainder by an absorption liquid type carbon dioxide separating device 28, and it is fed to the device 27 as purge gas PG to accelerate permeation and separation. The gas containing moisture S is fed to a reformer 8 via a compressor 29 as part of the steam required for reforming natural gas NG. The quantity of the steam S generated by a steam generator and mixed with natural gas NG via a steam line 17 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a power generation method using a molten carbonate fuel cell used in the energy sector, which directly converts the chemical energy of fuel into electrical energy.

[Prior Art] Molten carbonate fuel cells that have been proposed to date include an electrolyte plate (tile) made by impregnating a porous material with molten carbonate, and a cathode (oxygen electrode) and seven nodes ( One cell is one in which electricity is generated by the potential difference generated between the cathode and the anode by sandwiching them between both sides with fuel electrodes, supplying oxidizing gas to the cathode side and supplying fuel gas to the anode side. The structure is such that each cell is stacked in multiple layers via a hibernate.

The fuel gas used as the fuel for the molten carbonate fuel cell may be one produced in a reformer, or, for example, in a conventional natural gas reforming molten carbonate fuel cell power generation system that reformes natural gas. An example of this is a configuration as shown in FIG. That is, in order to supply oxidizing gas OG to the cathode 2 of the fuel cell 1, air A is compressed by the compressor 4 on the air supply line 6, preheated by the air preheater 5, and supplied to the cathode 2. , a part is supplied to the reformer 8 by a branch line 7, and the gas discharged from the cathode 2 is led to a turbine 10 via a line 9 and further discharged through the air preheater 5.

On the other hand, natural gas (for example, methane) NG as a reforming raw material gas supplied to the anode 3 of the fuel cell 1 is pressurized by the blower 18 on the natural gas introduction line 22, and is sent to the natural gas preheater 11 and the desulfurizer. 23 to the reformer 8, where it is reformed as fuel gas FG and supplied to the anode 3 via the fuel gas line 19, and the 7 node gas AG discharged from the anode 3 contains moisture. Therefore, after part of the moisture in this anode gas AG is separated from the gas, the separated water is mixed with natural gas NG on the input side of the reformer 8 as steam. For this purpose, conventionally, the anode gas AG discharged from the anode 3 of the fuel cell 1 is passed through the natural gas preheater 11 via the anode output log gas line 20, cooled and condensed in the condenser 12, and then passed through the gas-liquid separator. 14, the gas G is guided to the reformer 8 by the blower 13 and used as a combustion gas, and the water (H2O) is pressurized by the pump 15 and sent to the steam generator 16. It is heated here and supplied to the natural gas introduction line 22 at the inlet side of the reformer 8 via the steam line 17 as steam S.
The combustion exhaust gas containing carbon dioxide discharged from the reformer 8 passes through the exhaust gas line 21 and is mixed with the natural gas NG in the fuel cell 1 along with the air flowing through the air supply line 6. It is intended to be supplied to 2.

[Problem to be solved by the invention] However, in the case of the above-mentioned conventional molten carbonate fuel cell power generation system, all the steam necessary for the reforming reaction is obtained from water. A large steam generator 16 is required, and a large amount of energy is consumed to generate the steam.

Therefore, the present invention makes it possible to obtain part of the steam necessary for reforming raw material gas without relying on a steam generator, thereby reducing the size of the steam generator and reducing the consumption required to generate steam. The present invention aims to provide a power generation method using a molten carbonate fuel cell that can reduce energy consumption.

[Means for Solving the Problems 1] In order to solve the above-mentioned problems, the present invention introduces reforming raw material gas together with water vapor into a reformer to reform the reformed fuel gas, and supplies the reformed fuel gas to the anode of a fuel cell. In a power generation method for a molten carbonate fuel cell, the oxidizing gas is supplied to the cathode of the fuel cell, and an electrochemical reaction is caused between the anode and the cathode to generate electricity. Part of the water vapor in the anode gas discharged from the battery anode is permeated and separated by a separation membrane type water vapor separator, and the water vapor obtained by separation is used as part of the water vapor necessary for reforming the reforming raw material gas. A power generation method using a molten carbonate fuel cell is characterized in that the fuel cell is introduced into the reformer.

In addition, in order to promote the permeation of water vapor, the anode gas is treated to remove some of the carbon dioxide gas and water vapor.
It is preferable that the gas from which a portion of the membrane-type steam separator is removed is supplied as a purge gas to the permeation side of the membrane-type steam separator.

Furthermore, a part of the reformed raw material gas may be used as the purge gas.

[Function] When the anode gas is guided to the separation membrane type steam separator,
Since some of the water vapor contained in the anode gas is permeated, this permeated water vapor can be led to the reformer and used as part of the water vapor necessary for reforming the reforming raw material gas. This reduces the amount of steam required for reforming by 1 q, making it possible to reduce the amount of steam generated from water, thereby reducing the size of the steam generator and the consumption required to evaporate the water. This means that it is possible to reduce energy consumption.

In the above, if the anode gas is treated to remove part of carbon dioxide and water, or part of the reformed raw material gas is supplied as a purge gas to the permeation side of the separation membrane type steam separator, the water vapor permeates. can be promoted,
Further, the water vapor that has passed through the separation membrane can be included in the purge gas and supplied to the reformer, and at this time, the water vapor concentration can be increased.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the main parts of a power generation system for carrying out the method of the present invention. A heat exchanger 24, a shift reactor 25, a heat exchanger 26, and a separation membrane steam separation device 2 are connected to the anode outlet gas line 20 that guides the high temperature anode gas AG to be discharged.
7. The absorption liquid type carbon dioxide gas separation device 28 is installed sequentially from the upstream side, so that a part of the water vapor S in the 7-node gas AG can be permeated and recovered by the separation membrane type water vapor separation device 27, and The absorption liquid type carbon dioxide gas separation device 28 can remove a portion of carbon dioxide and water contained in the anode gas AG after a portion of the water vapor S has been removed by the separation membrane type water vapor separation device 27,
In addition, the permeation side 27a of the separation membrane type steam separation device 27 and the reforming side of the reformer 8 are connected by a steam line 30 equipped with a compressor 29, and the separation membrane type steam separation device 2
7 supplies the water vapor S separated from the anode gas AG to the reformer 8, and the natural gas line 22
It is used as a part of the steam S necessary for reforming the natural gas NG as a reforming raw material gas introduced into the reformer 8 through A purge gas line 31 is connected between the side and the permeation side 27a of the separation membrane type water vapor separator 27, and the gas from which carbon dioxide and a portion of water have been removed by being processed by the absorption liquid type carbon dioxide gas separator 28 is converted into water vapor. The purge gas PG for promoting the permeation of S is supplied to the permeation side 27a of the separation membrane type steam separator 27.

The 7-node gas AG in the anode outlet gas line 20 discharged from the anode 3 of the molten carbonate fuel cell 1 is cooled by the heat exchanger 24, and further cooled by the heat exchanger 26 via the shift reactor 25, and then Separation membrane type steam separator 2
7, where a part of the water vapor S is separated by passing through a separation membrane and collected on the permeation side 27a.

Anode gas AG after some of the water vapor S has been removed
is further introduced into the absorption liquid type carbon dioxide gas separation device 28, where a process is performed to remove part of the carbon dioxide gas and water contained in the anode gas AG, and this process lowers the concentration of carbon dioxide gas and water. The gas is passed through the purge gas line 31 as purge gas PG to the separation membrane type steam separator 2.
7 to the transmission side 27a. Therefore, the purge gas PG promotes the permeation and separation of the water vapor S in the separation membrane type water vapor separator 27, so that the purge gas line contains the water vapor S. When this gas containing water vapor S is compressed by the compressor 29 and then supplied to the reforming side 27a of the reformer 8 through the steam line 30, the water vapor contained in this gas is used to reform the natural gas NG. This gas is introduced into the reforming side of the reformer 8 as part of the water vapor S necessary for A reforming reaction is performed by a gas mixture of natural gas NG as a reforming raw material gas introduced through the steam line 17 and steam S from the steam line 17, and the natural gas NG is converted into fuel gas (reformed gas) FG.
The reformed fuel gas FG is reformed as fuel cell 1.
It will be supplied to the anode 3 side of.

In the present invention, as described above, the anode gas AG is permeated through the separation membrane type steam separator 27 as part of the steam necessary for reforming the natural gas NG as the reforming raw material gas in the reformer 8. Since the steam S obtained by the separation is used, it is possible to reduce the rate of steam S generated in the steam generator 16 and mixed into the natural gas NG through the steam line 17. The size of the container 16 can be reduced, and the energy consumption for turning water into steam can be reduced accordingly.

Next, the above-mentioned steps will be explained in detail based on specific experimental results.

When the fuel cell 1 is a pressurized type, the pressure is 2.9K.
g/cfflA, temperature 680'C, moisture 39%
After cooling the anode gas AG to 190'C in the heat exchanger 24, it is subjected to low temperature shift reaction 1;i in the shift reactor 25.
5 and further cooled to 110° C. using a heat exchanger 26.

At this time, the pressure of the anode gas AG after cooling is 2.7
It contained 36% water in 'J/criA. next,
This anode gas AG was supplied to a separation membrane type water vapor separator 27, and 25% of water (steam) was passed through and separated. The anode gas AG from which a portion of the moisture has been separated is further supplied to the absorption liquid type carbon dioxide gas separation device 28 to remove a portion of the carbon dioxide gas and moisture, resulting in a pressure of 2.66 Ng/
A gas containing 17% water at a temperature of 80° C. was obtained. When this gas is supplied as purge gas PG to the permeation side 27a of the separation membrane type water vapor separator 27, this gas contains the water vapor S that has permeated through the separation membrane type water vapor separator 27, and the water vapor concentration reaches 32%. Rose.

Next, the gas with the increased water vapor S degree is transferred to the compressor 2.
9 to raise the pressure to 2.8 Kl/criA, then reformer 8
supplied. At this time, the steam S supplied from the steam line 30 and the steam S supplied from the steam line 17 as reformed steam were approximately the same amount. That is, by separating and recovering the steam S in the separation membrane type steam separator 27, the amount of steam S generated and supplied by the steam generator 16 for reforming could be reduced by half. .

Incidentally, in the above embodiment, an absorption 4 carbon dioxide gas separation device 28 is installed on the permeation side 27a of the separation membrane type water vapor separation device 27.
Although the case is shown in which the gas obtained in the above is supplied as purge gas PG through the purge gas line 31, for example, as shown by the two-dot chain line in FIG. 32 is connected to the permeation side of the separation membrane type steam separator 27,
A part of the natural gas NG as the reforming raw material gas may be used alone or in combination as the purge gas PG, and it goes without saying that various changes can be made without departing from the gist of the invention. be.

[Effects of the Invention] As described above, the power generation method using a molten carbonate fuel cell of the present invention exhibits the following excellent effects.

(1) The steam separated and recovered from the 7-node gas is used as part of the steam necessary for reforming the reforming raw material gas, so the amount of steam generated and supplied for reforming is reduced. This allows the steam generator to be made smaller.

(11) Moreover, since the amount of water vapor generated and supplied can be reduced according to the above (1), the energy consumed to generate water vapor can be reduced.

(iii) By introducing the gas obtained by treating the anode gas to remove a portion of carbon dioxide gas and water, or a portion of the reformed raw material gas, as a purge gas to the permeation side of the separation membrane type steam separator, water vapor can be removed. Permeation can be promoted.

[Brief explanation of drawings]

FIG. 1 is a partial diagram showing an example of a system for implementing the power generation method using a molten carbonate fuel cell of the present invention, and FIG. 2 is a system diagram showing an outline of an example of a conventional system. 1...-fuel cell, 2... cathode, 3... anode, 8... reformer, 17... steam line, 19...
- Reformed gas line, 20... Anode outlet gas line, 22... Natural gas introduction line, 27... Separation membrane steam separation device, 27a... Permeation side, 30... Steam line, NG・・・Natural gas (reformed raw material gas), FG・
...fuel gas, OG...oxidizing gas, AG...anode gas, S...steam, PG...purge gas.

Claims (3)

[Claims] (1) Reforming raw material gas is introduced into the reformer together with water vapor to be reformed, and the reformed fuel gas is supplied to the anode of the fuel cell. On the other hand, oxidizing gas is supplied to the cathode of the fuel cell, and the anode In a power generation method using a molten carbonate fuel cell, which generates power by causing an electrochemical reaction between the cathodes, a part of the water vapor in the anode gas discharged from the anode of the fuel cell is removed using a separation membrane. The water vapor obtained by the separation is permeated and separated using a type steam separator.
A power generation method using a molten carbonate fuel cell, characterized in that the steam is introduced into the reformer as part of the steam necessary for reforming the reforming raw material gas. (2) A gas obtained by treating the anode gas to remove a portion of carbon dioxide and water is supplied to the permeation side of the separation membrane type steam separator as a purge gas that promotes water vapor permeation. A method of generating electricity using a molten carbonate fuel cell. (3) The molten carbonate fuel cell according to claim (1) or (2), wherein a part of the reformed raw material gas is supplied to the permeation side of the separation membrane type steam separation device as a purge gas that promotes water vapor permeation. How to generate electricity.