JPH0652879A - Exhaust gas treatment device of fuel cell power generating unit - Google Patents

Abstract

PURPOSE:To efficiently and compactly perform removal of phosphoric acid in exhaust gas, recovery of waste heat and recycling of condensed water by integrating a high temperature portion heat exchanger, a phosphoric acid recycling pallet, a low tempera ture portion heat exchanger and a condensed water recycling tank with one another. CONSTITUTION:When the exhaust gas of a fuel cell main body 11 is allowed to flow into a high temperature portion heat exchanger 21, it is cooled by cooling water to a temperature range where phosphoric acid is deposited, and the phosphoric acid deposited is collected by a phosphoric acid recycling pallet 22. The exhaust gas flowing into a low temperature portion heat exchanger 23 is cooled to a temperature range where generated steam condenses, and the condensed water is collected into a recycling tank 26. The cooling water is allowed to flow out into an outlet line 28b from an inlet line 28a through the heat exchangers 23, 21 and a series of heat transfer pipes 27. Since the exchangers 21, 23 and the recycling pallet 22 and tank 26 can be integrated with one another, removal of phosphoric acid, recovery of waste heat and recycling of condensed water are efficiently performed and the device can be made compact as a whole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphoric acid fuel cell power generator, and more particularly to an exhaust gas treatment device for removing phosphoric acid contained in the exhaust gas of a fuel cell to recover condensed water and exhaust heat in the exhaust gas. It is a thing.

[0002]

2. Description of the Related Art A fuel cell power generator is a device for converting chemical energy of a fuel such as city gas or propane gas into electric energy, and produces hydrogen from fuel such as city gas or propane gas. It is composed of a device, a fuel cell main body, a converter for converting a direct current into an alternating current, a heat exchange device for maintaining the temperature of the working gas at a temperature suitable for the operation of the fuel cell main body and hydrogen generation. The fuel cell body directly converts the binding energy of hydrogen generated by the hydrogen generator and oxygen in the air into electricity, but at the same time, heat is also generated.

Such a fuel cell power generator is evaluated as a clean power generator because it has a high power generation efficiency due to power generation by a chemical reaction, emits less air pollutants, and emits less noise.

However, in a phosphoric acid fuel cell power generator using a phosphoric acid electrolyte in the fuel cell body, water vapor generated by the electrochemical reaction of phosphoric acid between hydrogen and oxygen and air used in the fuel cell body. It is discharged outside the battery together with the exhaust gas of.

FIG. 5 shows a structural example of a treatment system for exhaust gas discharged from a fuel cell main body of a conventional fuel cell power generation system. In FIG. 5, the cell exhaust gas discharged from the fuel electrode 1a and the air electrode 1b of the fuel cell body 1 contains a phosphoric acid solution produced by phosphoric acid and water vapor that gradually flow out to the outside due to the operation of the cell. However, since this phosphoric acid solution has high corrosiveness to carbon steel and alloy steel, it is necessary to remove the phosphoric acid solution from the exhaust gas.

Therefore, generally, a phosphoric acid removing device 2 is installed in the exhaust gas system 5a of the fuel cell main body 1, where phosphoric acid is adsorbed and collected, and equipment, pipes and the like installed downstream thereof are corroded. I try not to.

On the other hand, since the exhaust gas from the fuel electrode 1a of the fuel cell body 1 is generally used as a gas for a combustion burner of a reformer (not shown), the exhaust gas temperature is high. Therefore, the exhaust heat recovery device 3 installed on the downstream side of the phosphoric acid removal device 2 lowers the exhaust gas temperature to a low temperature region, and the condensed water recovery device 4 installed further on the downstream side of the exhaust gas recovers the water vapor component in the exhaust gas. The condensed water is recovered and reused by returning it to the battery cooling water or the like, and the exhaust gas from which the water vapor component has been removed is released to the atmosphere. In this case, the phosphoric acid removing device 2 has been devised and implemented a method of removing phosphoric acid in exhaust gas by causing a corrosive reaction with iron wool or the like.

Further, a heat exchanger is installed in the exhaust heat recovery device 3, and the exhaust gas from which phosphoric acid has been removed is flown to the high temperature side of the heat exchanger.
By flowing water as a cooling medium to the low temperature side, this water is recovered as high temperature water heated by the heat of exhaust gas, and this is supplied to an exhaust heat utilization device (not shown) through an exhaust heat recovery line.

Further, a heat exchanger is installed in the condensed water recovery device 4, and the exhaust gas temperature is generally recovered as a drain by lowering it to a temperature at which steam components can be recovered as condensed water.

[0010]

However, the exhaust gas treating apparatus of the fuel cell power generator having such a structure has the following problems.

That is, of the treatment system for exhaust gas discharged from the fuel cell body, the phosphoric acid removing device 2 is
Since the structure is such that iron wool is enclosed in the container,
By increasing the size of the device and installing this device,
Since the pressure loss of the exhaust gas system increases, the discharge pressure of the air blower that supplies the air to the air electrode of the fuel cell main body increases, which increases the required power amount and reduces the efficiency of the system. .

Further, the exhaust heat recovery device 3 and the condensed water recovery device 4 are respectively provided with heat exchangers, and the condensed water recovery device 4 has a large amount of latent heat of condensation for condensing condensed components. A large amount of heat area is required. Therefore, the apparatus becomes large in size, and there is a problem similar to that of the phosphoric acid removing apparatus.

As described above, in the exhaust gas treatment device of the conventional fuel cell power generator, since the phosphoric acid removing device, the exhaust heat recovery device, and the condensed water recovery device are separately installed, the respective devices are enlarged. At the same time, the capacity of the plant equipment is increased, which further increases the cost of the plant.

According to the present invention, the phosphoric acid removing device, the exhaust heat recovery device, and the condensed water recovery device of the exhaust gas treatment system of the fuel cell body are integrated to achieve compactness, and at the same time, the phosphorus contained in the exhaust gas of the fuel cell body. An object of the present invention is to provide an exhaust gas treatment device of a fuel cell power generation device capable of efficiently removing acid, recovering exhaust heat, and recovering condensed water.

[0015]

In order to achieve the above-mentioned object, the present invention provides a fuel cell power generator having a fuel cell body using a phosphoric acid electrolyte, in which a gas diffuses from the electrolyte of the fuel cell body. The high temperature heat exchanger that introduces the exhaust gas containing the phosphoric acid solution discharged together with the generated steam and cools the temperature of the exhaust gas to the temperature range in which phosphoric acid precipitates, and is provided below the high temperature heat exchanger. A phosphoric acid recovery pallet for recovering the phosphoric acid solution deposited by cooling the high temperature heat exchanger, and cooling the exhaust gas introduced by removing the phosphoric acid solution by the high temperature heat exchanger into the exhaust gas. The low temperature section heat exchanger that lowers the generated steam contained therein to the temperature range where it is condensed, and the condensed water recovery tank that is provided under the low temperature section heat exchanger and recovers the condensed water of the generated steam, these high temperature section heat Exchanger Phosphoric acid recovery pallet, the low-temperature portion heat exchanger and condensed water recovery tank with integrally configured,
By arranging a series of heat transfer tubes for cooling water in the low temperature section heat exchanger and the high temperature section heat exchanger, and circulating cooling water from the low temperature section heat exchanger side to the high temperature section heat exchanger side. ,
The heat quantity retained in the exhaust gas is collected as hot water.

[0016]

In the exhaust gas treatment device of the fuel cell power generator having such a structure, when the exhaust gas containing the phosphoric acid solution together with the generated steam flows into the high temperature heat exchanger, the exhaust gas temperature is changed in the high temperature heat exchanger. By cooling to a temperature range in which phosphoric acid precipitates, phosphoric acid in the exhaust gas is removed and recovered in the phosphoric acid recovery pallet. Furthermore, when the exhaust gas from which phosphoric acid has been removed by this high temperature heat exchanger flows into the low temperature heat exchanger, this exhaust gas temperature is cooled to a temperature range where the generated steam in the exhaust gas is condensed, and the generated steam in the exhaust gas is condensed. Water is recovered in the condensed water recovery tank.

Therefore, as a treatment system for exhaust gas containing phosphoric acid liquid together with generated steam, a high temperature heat exchanger for removing phosphoric acid, a low temperature heat exchanger for condensing generated steam, and a condensed water recovery tank can be integrated. Therefore, removal of phosphoric acid, recovery of exhaust heat, and recovery of condensed water can be efficiently performed, and the entire apparatus can be made compact.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a schematic structure of an exhaust gas treating apparatus of a fuel cell power generator according to the present invention. In FIG. 1, reference numeral 12 is an integrated exhaust gas treatment device provided in a supply system 13a for the exhaust gas flowing out from the fuel electrode and the air electrode of the fuel cell main body 11. This integrated exhaust gas treatment device 12 is a high temperature fluid, that is, exhaust gas and low temperature. Each of the phosphoric acid removal function 12a, the condensed water recovery function 12b, and the exhaust heat recovery function 12c is configured to function by heat exchange with the fluid, that is, the cooling water. Further, the exhaust heat recovery function 12c recovers the amount of heat contained in the exhaust gas supplied through the exhaust gas supply line 13a to the cooling water flowing in from the cooling water inlet line 14a,
The high-temperature water can be supplied to the exhaust heat utilization device 15 through the exhaust heat recovery supply line 14b.

FIG. 2 is a schematic sectional view showing an example of a schematic structure of the integrated exhaust gas treatment apparatus 12. As shown in FIG. 2, the integrated exhaust gas treatment device 12 includes a high temperature part heat exchanger 21 having a phosphoric acid removing function, and a low temperature part heat exchanger 2 provided below the high temperature part heat exchanger 21 via a phosphoric acid recovery pallet 22.
3 and the condensate water recovery illuminator 24 further below
And a condensed water recovery tank 26 provided via a condensed water recovery seat 25.

A series of cooling water heat transfer tubes 27 are arranged in a zigzag shape in the high temperature part heat exchanger 21 and the low temperature part heat exchanger 23, and the cooling water inlet provided on the low temperature part heat exchanger 23 side. When the cooling water flows in from the line 28a, the cooling water meanders in a zigzag manner through the cooling water heat transfer pipe 27 and rises, and flows out from the cooling water outlet line 28b provided on the high temperature heat exchanger 21 side. Has become.

On the other hand, the fuel electrode 11a of the fuel cell main body 11,
The exhaust gas flowing out from the air electrode 11b flows in from the upper part of the present apparatus through the exhaust gas supply line 29a, passes through the high temperature heat exchanger 21 and the low temperature heat exchanger 23, and flows out to the exhaust gas outlet line 29b provided in the lower part. It is like this.

FIG. 3 is a perspective view showing the internal structure of the integrated exhaust gas treatment apparatus 12 of FIG. 2 more specifically. The same parts as those of FIG. 2 are designated by the same reference numerals, and a duplicate description will be omitted. To do. In FIG. 3, reference numeral 30 denotes a removable lid installed on the upper part of the present apparatus. The lid 30 is for removing phosphoric acid deposits and other deposits attached to the outer surface of the heat transfer surface of the high temperature part heat exchanger 21. It is removed when cleaning the fuel cell power plant or when performing an internal inspection. The phosphoric acid recovery pallet 22 is arranged so as to be able to be drawn out between the high temperature part heat exchanger 21 and the low temperature part heat exchanger 23, and is deposited on the heat transfer surface of the high temperature part heat exchanger 21 and flows down. The phosphoric acid is collected, and when the plant is stopped, the phosphoric acid can be withdrawn laterally from this equipment to remove the phosphoric acid, and the inside of the pallet can be washed.

Next, the operation of the exhaust gas treating apparatus of the fuel cell power generator having such a structure will be described. When the exhaust gas flows in from the exhaust gas supply line 29a in the upper part of the apparatus, the exhaust gas is processed through the high temperature heat exchanger 21 and the low temperature heat exchanger 23, and is exhausted from the lower exhaust gas outlet line 29b.

On the other hand, the cooling water flows into the heat transfer pipe 27 of the low temperature part heat exchanger 23 from the cooling water inlet line 28a at the lower part of the apparatus, rises in the pipe in opposition to the flow of the exhaust gas, and further heat exchange in the high temperature part. It is heated by flowing in the tube of the vessel 21,
It becomes high-temperature water and flows out from the cooling water outlet line 28b, and this high-temperature water is used as a heat source such as an exhaust heat utilization device.

Here, the exhaust gas treatment function in this apparatus will be described in detail. Exhaust gas that has flowed in from the exhaust gas supply line 29a is first subjected to heat exchange in the high temperature section heat exchanger 21, and the exhaust gas temperature is lowered until all phosphoric acid in the exhaust gas has completely precipitated, so that the phosphoric acid contained in the exhaust gas is removed. , Are recovered in the phosphoric acid recovery pallet 22. In this case, if the phosphoric acid precipitation portion is made of a metal having high phosphoric acid resistance or the like, phosphoric acid can be precipitated and recovered without corroding the present apparatus.

FIG. 4 summarizes the qualitative relationship between the phosphoric acid concentration and its vapor pressure, and the relationship between the phosphoric acid concentration and the corrosion rate and temperature of the metal material. The phosphoric acid in a gaseous state in the high temperature gas falls to a certain temperature due to its concentration, and precipitates when the vapor pressure is reached. The concentration of phosphoric acid in fuel cell exhaust gas is sufficiently low, and by lowering it to around 120 ° C,
All is completely deposited.

Further, the lower the phosphoric acid concentration is to some extent and the higher the temperature is, the higher the corrosion rate of the metal material becomes. However, the metal material having a high corrosion resistance to phosphoric acid, such as SUS316L, is contained in the exhaust gas of the fuel cell. It has been known from experiments that the corrosion is a safe area where corrosion does not proceed under the condition that is precipitated.

Therefore, as described above, the heat exchanging member in the phosphoric acid removing function is made of a material having a high phosphoric acid resistance in the region where phosphoric acid is deposited, so that phosphoric acid is deposited and recovered from the exhaust gas. can do.

When the exhaust gas from which phosphoric acid has been removed flows into the low temperature part heat exchanger 23, the exhaust gas temperature is lowered to a temperature at which the steam component in the exhaust gas is condensed, and condensed water adheres to the heat transfer surface of the heat exchanger member. To do. In this case, due to the partial pressure of the condensed component in the fuel cell exhaust gas component, the condensation is started by lowering the temperature to around 70 ° C., and the condensed amount increases as the temperature decreases. Therefore, in order to lower the temperature of the exhaust gas, it is advantageous that the temperature of the cooling water flowing to the low temperature side of the low temperature part heat exchanger 23 is low.

The water condensed on the surface of the heat transfer surface of the low temperature heat exchanger 23 is transmitted through the heat transfer tubes, fins, etc., and flows down, and is recovered by the condensed water recovery eliminator 5 installed at the lower part thereof and condensed. It passes through the water recovery seat 6 and collects in the condensed water recovery tank 7 at the bottom.

As described above, in this embodiment, the phosphoric acid deposited in the high temperature section heat exchanger does not flow down to the low temperature section heat exchanger 23, so that the low temperature section heat exchanger which requires a large heat transfer area is resistant to phosphorus. Since copper, aluminum, carbon steel or the like can be used without using a material having an acid, the cost of the device can be reduced and the device can be made compact.

In order to lower the temperature of the exhaust gas, cooling water is made to flow to the low temperature side of the heat exchanger having the phosphoric acid removal function and condensed water recovery function to cool the exhaust gas. By flowing in the opposite direction, the heat exchange rate is increased and the cooling water is also heated. Therefore, this heated water can be taken out as waste heat recovery water and supplied to the waste heat utilization device.

Further, the conventional phosphoric acid removing device has a problem that the pressure loss of the exhaust gas system is large as described above, but in this embodiment, the high temperature part heat exchanger 21 cools the phosphoric acid until it precipitates. As a result, the pressure loss in the exhaust gas system is reduced, and the exhaust gas flow velocity can be increased by the amount of the pressure loss having a margin, so that the apparatus can be made compact.

On the other hand, in the above-mentioned embodiment, the pallet 22 for recovering the phosphoric acid deposited by the exhaust gas passing through the high temperature heat exchanger 21 is installed outside the apparatus, and the lid 30 is removable on the upper side of the apparatus. Since it is installed in the plant, the exhaust gas heat exchanger can be easily cleaned and inspected while it is still installed in the plant, which was difficult in the past, and the maintainability is improved. Dirt adhering to the inside of the exchanger 21 can be removed, and the performance and efficiency of the plant can be improved without adversely affecting the heat transfer performance. in this case,
When cleaning the pallet, if contaminated water falling down is prevented from flowing into the condensed water recovery tank, the condensed water recovery seat 25 in FIG. Furthermore, the cleaning can be easily performed.

The high temperature heat exchanger, the phosphoric acid recovery pallet, the low temperature heat exchanger and the condensed water recovery tank are arranged on the left and right sides of one housing, and the high temperature exhaust gas is discharged from the left side of the housing. You may make it introduce | transduce and you may make it discharge low temperature exhaust gas from the right.

[0037]

As described above, according to the present invention, the phosphoric acid removing device, the exhaust heat recovery device, and the condensed water recovery device of the exhaust gas treatment system of the fuel cell body are integrated to achieve compactness, and at the same time, the fuel is removed. It is possible to provide an exhaust gas treatment device for a fuel cell power generator that can efficiently remove phosphoric acid contained in the exhaust gas of the cell body, recover exhaust heat, and recover condensed water.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an exhaust gas treatment device of a fuel cell power generator of the present invention.

FIG. 2 is a schematic sectional view of the embodiment.

FIG. 3 is a perspective view showing a specific internal structure of the embodiment.

FIG. 4 is a curve diagram showing the relationship between the phosphoric acid concentration and its vapor pressure, temperature, and the corrosion rate and temperature of metallic materials.

FIG. 5 is a configuration diagram showing an exhaust gas treatment system of a conventional fuel cell power generator.

[Explanation of Codes] 11 ... Fuel cell main body, 11a ... Fuel electrode, 11b ...
Air electrode, 21 ... high temperature heat exchanger, 12 ... integrated exhaust gas treatment device, 22 ... phosphoric acid recovery pallet, 23 ...
Low temperature heat exchanger, 24 ... Eliminator for collecting condensed water,
25 ... seat for collecting condensed water, 26 ... tank for collecting condensed water,
27 ... Cooling water heat transfer tube, 28a ... Cooling water inlet line, 28b ... Cooling water outlet line, 29a ... Exhaust gas supply line, 29b ... Exhaust gas outlet line, 30 ... Lid.

Claims (1)

[Claims] 1. A fuel cell power generator having a fuel cell body using a phosphoric acid electrolyte, wherein an exhaust gas containing a phosphoric acid solution which is diffused from an electrolyte of the fuel cell body and is discharged together with generated steam is introduced. A high temperature heat exchanger that cools the temperature of this exhaust gas to a temperature range where phosphoric acid precipitates, and a phosphoric acid solution that is deposited by cooling the high temperature heat exchanger that is provided below this high temperature heat exchanger is recovered. A phosphoric acid recovery pallet, and a low temperature heat exchanger that cools the exhaust gas introduced by removing the phosphoric acid liquid by the high temperature heat exchanger and lowers it to a temperature range where the generated water vapor contained in the exhaust gas is condensed. ,
A condensate recovery tank is provided below the low temperature part heat exchanger to recover the condensed water of the generated steam, and the high temperature part heat exchanger, the phosphoric acid recovery pallet, the low temperature part heat exchanger and the condensed water recovery device are provided. The tank is integrally configured, and a series of cooling water heat transfer pipes are arranged in the low temperature part heat exchanger and the high temperature part heat exchanger, and the high temperature part heat exchanger is arranged from the low temperature part heat exchanger side. An exhaust gas treatment device of a fuel cell power generator, wherein the amount of heat retained in the exhaust gas is recovered as hot water by circulating cooling water to the side.