JPH04334870A - Fused carbonate type fuel cell generating set - Google Patents

Abstract

PURPOSE:To improve the recovery percentage of a carbon dioxide and to improve the efficiency of a total system by providing combustion equipment for burning at least part of an off gas exhausted from an adsorption type gas separator. CONSTITUTION:There is provided a system for supplying a fuel-based gas (a) to the anode 2 of a fuel cell main body 1, a system for supplying an air-based gas (d) to a cathode 3, an adsorption type gas separator 6 for recovering a carbon dioxide contained in an anode outlet gas (b), and combustion equipment 16 for burning at least part of an off gas released from the separator 6. This obtains a gas (i) having a temperature of about 1200 degrees C and consisting mainly of carbon dioxide free from combustible component. The efficiency of a total system is increased by recovering the resulting heat by a heat exchanger 17. In addition, the improvement and the effective utilization of the recovery percentage of the carbon dioxide are available by supplying the gas (i) to the cathode 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten carbonate fuel cell power generating apparatus, and more particularly to a fuel cell power generating apparatus equipped with an adsorption type gas separation device for separating carbon dioxide gas.

0002

[Prior Art] FIGS. 4 and 5 are, for example, Japanese Patent Application Laid-Open No. 62-2
Pressure swing adsorption type gas separation device (hereinafter referred to as
1 is a configuration diagram illustrating a carbon dioxide recovery method using a carbon dioxide gas recovery method (referred to as PSA); in the figure, a is a reformed gas system, b is an anode exhaust gas system, c is an anode reaction gas system, d is an air system, and e is a cathode gas system. Exhaust gas system, f is cathode reaction gas system, g is anode recycle gas system, 1 is molten carbonate fuel cell main body, 2 is fuel electrode (anode), 3 is air electrode (cathode), 4 is electrolyte, 5 is Fuel preheater, 6
is a PSA type gas separation device, 7 is an anode gas recirculation blower, 8 is an air compressor, 9 is an air preheater, 10 is a heat exchanger, 11 is a cathode gas recirculation blower, 12 is a mixer, 1
3 is an expansion turbine, 14 is a generator, and 15 is a combustor (or catalytic combustor). Moreover, FIG. 6 shows, for example, "Chemical equipment" (Kawai, Suzuki; vol. 31, No. 8, p. 54 (
This is the adsorption isotherm of PSA shown in 1989), which shows the amount of carbon dioxide in the adsorbent (g/g) relative to the partial pressure of carbon dioxide.
is shown using temperature as a parameter.

Next, the operation will be explained. The unit cell of the fuel cell main body 1 is constructed by interposing an electrolyte 4 between a fuel electrode (anode) 2 and an air electrode (cathode) 3. The reaction gas supply systems to the fuel electrode 2 and air electrode 3 are as follows. The reformed a and the anode exhaust gas b that have passed through the fuel preheater 5 are sent to the fuel electrode 2 as PS
The anode gas recycle g, which consists of components from which carbon dioxide has been removed after passing through the A-type gas separation device 6 and is circulated by the anode gas recirculation blower 7, is mixed and supplied as the anode reaction gas c. On the other hand, the air d and P that have passed through the air compressor 8 and the air preheater 9 sequentially go to the air electrode 3.
The carbon dioxide desorbed from the SA separator 6 and a portion of the cathode exhaust gas e that passes through the heat exchanger 10 and is circulated by the cathode gas recirculation blower 11 are transferred to the mixer 12.
The ingredients are mixed and adjusted to a carbon dioxide concentration of 5 to 50%.
It is supplied as a cathode reaction gas f. Direct current is generated in the molten carbonate fuel cell main body 1 by supplying these reaction gases. Further, a part of the cathode exhaust gas e is sent to the expansion turbine 13 and then released into the atmosphere. A part of the output of the expansion turbine 13 is used as power for the air compressor 8, and the remaining part of the output is used as power for the generator 14.

0004

[Problems to be Solved by the Invention] Conventional molten carbonate fuel cell power generation devices are as described above, so if the PSA is operated at high temperatures, the carbon dioxide recovery rate will be poor, whereas if it is operated near room temperature, the carbon dioxide recovery rate will be poor. There were problems such as the need for a separate heat source to raise the temperature of the recovered carbon dioxide.

The present invention was made to solve the above-mentioned problems, and provides a molten carbonate fuel cell power generation device that can improve the recovery rate of carbon dioxide gas and improve the efficiency of the entire system. The purpose is to provide

[0006]

[Means for Solving the Problems] A molten carbonate fuel cell power generation device according to the present invention includes a molten carbonate fuel cell main body, a system for supplying a fuel system gas to an anode of the fuel cell, and a system for supplying a fuel system gas to an anode of the fuel cell. A system that supplies air-based gas to the battery cathode, an adsorption gas separation device that recovers carbon dioxide contained in the anode outlet gas, and a combustion system that combusts at least a portion of the off-gas discharged from the adsorption gas separation device. The device is configured to include a device.

[0007]

[Operation] The combustion device of the present invention burns unrecovered carbon dioxide and off-gas from the adsorption gas separation device containing combustible gas in an adsorption gas separation device, thereby converting carbon dioxide containing no combustible components into the main component. This increases the efficiency of the system by producing hot gas that

[0008]

【Example】

Example 1. FIG. 1 is a block diagram showing the main parts of a fuel cell power generation system according to an embodiment of the present invention.
17 is a combustion device, 17 is a heat exchanger, 18 is a mixer, h is a recycled off-gas system, i is a combustion non-gas system, and j is a recycled mixed gas system. The other symbols are the same as or correspond to those of the conventional device, so the explanation will be omitted.

Next, the operation will be explained. In a fuel cell main body 1 composed of a fuel electrode (anode) 2, an air electrode (cathode) 3, an electrolyte 4, etc., a fuel system gas a and an anode exhaust gas b are supplied to the anode 2 and converted into carbon dioxide by a PSA type gas separation device 6. is composed of the separated PSA offgas h excluding the gas supplied to the combustion device 16, and after being mixed with the anode recycle gas g circulated by the anode gas circulation blower 7, passes through the fuel system preheater 5, Supplied as anode reaction gas c. on the other hand,
Air-based gas d passed through the air compressor 8 to the cathode 3,
The cathode gas circulates through the heat exchanger 10 and the cathode gas circulates through the blower 1.
A part of the cathode exhaust gas e circulated by 1 is mixed in a mixer 12, and a recycled mixed gas j is preheated again in a heat exchanger 10, carbon dioxide gas desorbed from a PSA type gas separation device 6, and a PSA type gas separator 6. Part or all of the PSA off-gas h after carbon dioxide has been separated in the gas separation device 6 is combusted in the combustion device 16, and the combustion exhaust gas i that has passed through the heat exchanger 17 is mixed in the mixer 18, and then air system preheating is performed. 9 and is supplied as a cathode reaction gas f. Further, a portion of the cathode exhaust gas e is sent to the expansion turbine 13, and a portion of its output is used as power for the air compressor 8, and the rest is used as power for the generator 14.

According to the above embodiment, by burning the combustible gas in the PSA off-gas, it is possible to obtain a gas whose temperature has risen to around 1200° C. and whose main component is carbon dioxide containing no combustible components. By recovering the heat contained in this gas, the efficiency of the entire system and equipment can be increased. Furthermore, even if the anode exhaust gas is introduced into the PSA in a high-temperature state, the PSA gas that has not been recovered in the PSA and the PSA off-gas that contains combustible gas can be burned in the combustion device, resulting in a gas that is mainly composed of carbon dioxide and does not contain combustible components. is obtained, and by supplying this to the cathode side, the carbon dioxide recovery rate can be improved and carbon dioxide gas can be used effectively.

Example 2. FIG. 2 is a block diagram of main parts showing another embodiment of the present invention, and the reference numerals in the figure are the same as those in the embodiment shown in FIG. In this embodiment, the gas d from the air system compressed by the air compressor 8 is directly guided to the heat exchanger 17. This embodiment provides substantially the same effects as the embodiment shown in FIG. 1, and also has the advantage that the mixer 12 in FIG. 1 can be omitted.

Example 3. FIG. 3 is a block diagram showing still another embodiment of the present invention. In the figure, 19 is a heat exchanger, and 20 is a turbine generator. Other symbols are the same as those in the embodiment shown in FIG. 1, so their explanation will be omitted.

In the above configuration, the fuel system gas a is preheated by the heat of the anode exhaust gas b by the heat exchanger 19, and then is sent to the fuel preheater 5. On the other hand, the anode exhaust gas b passes through the heat exchanger 19 and is then fed to the PSA type gas separation device 6. Further, the PSA off-gas combusted by the combustion device 16 is sent to the generator 20, and after releasing a part of the thermal energy as electrical energy, it is sent to the heat exchanger 17. In this embodiment, in addition to the effects of the above embodiment, it is expected that the efficiency of the system can be further improved.

Additionally, in order to operate the PSA at a temperature lower than the anode outlet gas temperature, the anode outlet gas system may be provided with a heat exchanger or a heat exchanger and a drain separator. In addition, in the above example, the case where the combustion exhaust gas of the combustion device is used for preheating gas in a heat exchanger or used for power generation is explained, but the present invention is not limited to these and any heat recovery device may be used. . Further, the adsorption type gas separation device is not limited to the PSA type. Furthermore, the combustion device is not limited to this, and may be of any type, such as a catalytic combustion device.

Furthermore, the configuration of each device in the carbon dioxide recovery/circulation method of the molten carbonate fuel cell power generation apparatus of the present invention is not limited to that shown in the above embodiments.

[0016]

As described above, according to the present invention, the recovery rate of carbon dioxide can be improved by being configured to include a combustion device that burns at least a part of the off-gas discharged from the adsorption type gas separation device. This has the effect of providing a molten carbonate fuel cell power generation device that can improve the efficiency of the entire system.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram illustrating the main parts of a molten carbonate fuel cell power generation device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the invention.

FIG. 3 is a configuration diagram showing still another embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional device.

FIG. 5 is a configuration diagram showing another example of a conventional device.

FIG. 6 is a characteristic diagram showing the amount of carbon dioxide gas (g/g) in the adsorbent with respect to the partial pressure of carbon dioxide gas, using temperature as a parameter.

[Explanation of symbols]

a Reformed gas system b Anode exhaust gas system 1 Molten carbonate fuel cell body 2 Fuel electrode (anode) 3 Air electrode (cathode) 6 Adsorption type gas separation equipment 16 Combustion device

Claims (1)

[Claims] Claim 1: A molten carbonate fuel cell main body, a system for supplying fuel gas to the anode of the fuel cell, a system for supplying air gas to the cathode of the fuel cell, and a gas contained in the anode outlet gas. A molten carbonate fuel cell power generation device comprising an adsorption gas separation device that recovers carbon dioxide gas and a combustion device that burns at least a portion of off-gas discharged from the adsorption gas separation device.