JPH10223246A - Phosphoric acid type fuel cell power-generating plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a water treatment facility small and simple, and make the whole plant compact in a phosphoric acid type fuel cell power-generating plant. SOLUTION: A piping having a valve 20 is arranged in a condensing heat exchanger 8. The valve 20 is constituted to open, when condensed water is phosphoric acid condensed water containing a large amount of phosphoric acid product. A phosphoric acid condensed water recovery tank 21 is connected to the end of the piping. By recovering the phosphoric acid, condensed water in the phosphoric acid condensed water recovery tank 21, the inflow of the phosphoric acid condensed water into a water treatment facility 11 is prevented, and load on the water treatment facility is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power plant employing a phosphoric acid type fuel cell, and more particularly, to condensing water vapor contained in exhaust gas after passing through a fuel cell body to recover condensed water. The present invention relates to a phosphoric acid-type fuel cell power plant having a water self-supporting function for re-supplying water to a plant system after performing the purification process.

[0002]

2. Description of the Related Art In recent years, emphasis has been placed on environmental harmony, and research and development of power generation plants employing fuel cells have been advanced. A fuel cell is a device that directly extracts electric energy from chemical energy by causing an electrochemical reaction between hydrogen of a fuel electrode and oxygen of an air electrode via an electrolyte. Since such a fuel cell has no internal combustion cycle, it emits less SOx and NOx, which are polluting factors, has low vibration,
It has the advantage of low noise. Further, in a fuel cell, a large amount of exhaust heat and water vapor are generated due to a chemical reaction. Therefore, in the fuel cell power plant, in addition to the system for collecting electricity generated from the fuel cell, a system for collecting heat and water discharged by the fuel cell and a system for re-supplying the collected water to the plant system are provided. Have been. According to such a fuel cell power generation plant, it is possible to effectively use the water as a heat source for hot water supply and cooling and heating, and to make the water independent of the plant system, thereby improving the efficiency of the plant system.

Here, as an example of a fuel cell power plant, a power plant of a phosphoric acid type fuel cell using phosphoric acid as an electrolyte will be specifically described with reference to FIG. The phosphoric acid type fuel cell power plant has, as main components, a phosphoric acid type fuel cell main body 1, a steam separator 2, an air supply device 1
2, a reformer 3 and a condensation heat exchanger 8 are provided.

[Fuel Cell Body 1] A matrix 1a impregnated with phosphoric acid as an electrolyte is provided in the fuel cell body 1, and a fuel electrode 1b to which fuel gas is supplied across the matrix 1a and an air supply. The air electrode 1c is provided. Further, the temperature of the fuel cell main body 1 is set to 190 ° C. which is the optimum operating temperature.
Cooling plate 1 through which cooling water flows for the purpose of maintaining
d is installed.

In such a fuel cell body 1, the fuel electrode 1
Hydrogen in the fuel gas supplied to b and oxygen in the air supplied to the air electrode 1c undergo an electrochemical reaction via the phosphoric acid of the matrix 1a to generate power. At this time, reaction heat is generated at the same time as power generation in the fuel cell body 1, but the cooling plate 1
The function d allows the fuel cell main body 1 to be maintained at about 190 ° C.

[Air-water separator 2 and air supply device 12]
The steam separator 2 stores the cooling water 2b that has come out of the cooling plate 1d,
After separating water and steam, the reforming steam 2a is supplied to the reformer 3
And the cooling water 2b at a predetermined temperature is sent to the cooling plate 1d by a pump or the like. Air supply device 1
Numeral 2 is configured to supply the reaction air 5a to the air electrode 1c of the fuel cell body 1 and to supply the combustion air 5b to a burner 3b (described later) of the reformer 3.

[Reformer 3] The reformer 3 is provided with a reaction section 3a and a burner 3b as a heating source thereof. The reforming steam 2a and hydrocarbon fuel such as city gas are sent to the reaction section 3a. The reformer 3
The two are mixed to generate a hydrogen-rich reformed gas 4 containing hydrogen as a main component by a steam reforming reaction, and the reformed gas 4 is further supplied to the fuel electrode 1b.

[Condensation heat exchanger 8] By the way, some hydrogen remains in the reformed gas 4 which has been reacted at the fuel electrode 1b of the fuel cell body 1. Therefore, the reformed gas 4 discharged from the fuel electrode 1b enters the burner 3b of the reformer 3 and burns together with the combustion air 5b. The burner 3b discharges the flue gas 6 and this flue gas enters the condensation heat exchanger 8. Further, the reaction air 5a which has completed the reaction at the air electrode 1c of the fuel cell body 1
Holds water generated by the electrochemical reaction,
It enters the condensation heat exchanger 8 as exhaust air 7. That is, exhaust gas such as the combustion exhaust gas 6 and the exhaust air 7 is supplied to the condensation heat exchanger 8. The condensing heat exchanger 8 has heat transfer fins. The condensing heat exchanger 8 recovers the retained heat from the exhaust gas 6 and 7 and condenses water vapor to collect the heat.

[Water Treatment System] The power plant shown in FIG. 7 is provided with a water treatment system for purifying condensed water recovered by the condensation heat exchanger 8. The water treatment system is configured by sequentially connecting a decarbonation tower 9 for degassing carbon dioxide, a water tank 10 for storing condensed water, and a water treatment facility 11 including an ion exchange resin and the like. The collected condensed water is taken in. Water treatment equipment 1
The water purified in 1 returns to the plant system again and becomes the reforming steam 2a and the battery cooling water 2b to circulate in the plant. According to the power plant provided with the water treatment system as described above, the water can be re-supplied to the plant after the water treatment is performed, and the water can be provided with a water independent function.

[0010]

As described above, the fuel cell main body 1 of the phosphoric acid type fuel cell power plant usually has one fuel cell.
Since the battery is operated at about 90 ° C., phosphoric acid, which is an electrolyte of the battery body 1, is partially evaporated from the matrix 1a in the form of phosphorus oxide. Therefore, the flue gas 6 and the exhaust air 7 contain a trace amount of phosphorus oxide. When the condensing heat exchanger 8 cools the combustion exhaust gas 6 containing phosphorus oxide and the exhaust air 7, the condensation of phosphorus oxide starts at about 150 ° C. under general gas conditions (however, the concentration of phosphorus oxide in the gas, water vapor The temperature varies depending on conditions such as partial pressure). The dew point of water vapor is about 65 ° C.

The condensed phosphorus oxide takes in water vapor in the combustion exhaust gas 6 and the exhaust air 7 and hydrates, and a part of the condensed phosphorus is corroded in the metal part of the heat exchanger 8 to become a phosphoric acid product. It dissolves in the condensed water as ions and flows to the water tank 10 together with the phosphoric acid product. It is known that condensed water containing such a phosphoric acid product has a particularly high phosphoric acid content when the plant is started. This is because when the plant is started, water vapor condenses on the upstream side with respect to the flow direction of the exhaust gas passing through the condensing heat exchanger 8, and condenses on the heat transfer fins on the upstream side of the condensing heat exchanger 8. This is because the phosphoric acid product that has been washed out by the condensed water flows out in large quantities.

Therefore, conventionally, as a measure for treating condensed water containing a large amount of a phosphoric acid product (hereinafter, referred to as phosphoric acid condensed water), the phosphoric acid content of the transiently flowing phosphoric acid condensed water is taken as a measure. , The water treatment capacity of the water treatment facility 11 was increased. In addition, in addition to the ion exchange resin, a filter for treating a phosphoric acid product and a backwashing device for the same are indispensable for the water treatment facility 11. As a result, the water treatment equipment 11 has become complicated, and the compactness of the entire plant has been impaired. As described above, in the prior art, since phosphoric acid condensed water containing a large amount of phosphoric acid product may flow into the water treatment facility transiently, the load on the water treatment facility increases and the facility becomes complicated, This led to an increase in the size of the entire plant.

The present invention has been proposed in view of such conventional circumstances, and in a phosphoric acid fuel cell power plant, the water treatment equipment can be reduced in size and simplified, thereby contributing to downsizing of the entire plant. The purpose is to do so.

[0014]

In order to achieve the above object, the present invention is directed to a fuel cell body in which a matrix using phosphoric acid as an electrolyte is sandwiched between a fuel electrode and an air electrode; A reformer that reforms fuel to supply reformed gas to the fuel electrode, an air supply device that supplies reaction air to the air electrode, and a combustion exhaust gas discharged from the fuel electrode and the air electrode. A condensing heat exchanger that collects retained heat and condensed water from these exhaust gases by taking in the exhaust air that is discharged, a water tank that stores the condensed water collected by the condensing heat exchanger, and water that is stored in the water tank. In a phosphoric acid type fuel cell power plant including a water treatment facility for performing a purification process, a pipe through which the condensed water flows is provided in the condensing heat exchanger, and an openable / closable valve is provided in the pipe, The valve flows through the pipe Is opened when the condensed water is phosphoric acid condensed water containing a large amount of phosphoric acid product. A water recovery tank is connected.

According to the first aspect of the present invention, when the phosphoric acid condensed water flows through the pipe, the valve is opened, and the phosphoric acid condensed water collecting tank collects the phosphoric acid condensed water. In the phosphoric acid condensed water recovery tank, the phosphoric acid product and the condensed water are separated by standing, the condensed water is returned to the system, and the phosphoric acid product can be discharged out of the plant system. Therefore, the phosphoric acid condensed water containing a large amount of phosphoric acid product does not flow into the water treatment facility, and the load on the water treatment facility can be reduced.

According to a second aspect of the present invention, in the phosphoric acid type fuel cell power plant according to the first aspect, the water tank is divided into two layers, one of which is configured as the phosphoric acid condensed water recovery tank. It is characterized by.

According to the second aspect of the invention, in addition to the same operation as the first aspect of the invention, the conventional water tank can be integrally provided with the phosphoric acid condensed water recovery tank. Can be simplified.

A third aspect of the present invention provides a fuel cell body in which a matrix using phosphoric acid as an electrolyte is sandwiched between a fuel electrode and an air electrode, and a reformed gas is supplied to the fuel electrode by reforming a hydrocarbon-based fuel. A reformer to be supplied, an air supply device to supply air for reaction to the air electrode, and a combustion exhaust gas discharged from the fuel electrode and an exhaust air discharged from the air electrode taken in and retained from these exhaust gases. Phosphoric acid comprising a condensing heat exchanger for collecting heat and condensed water, a water tank for storing the condensed water collected by the condensing heat exchanger, and a water treatment facility for purifying the water stored in the water tank. In the fuel cell power plant, a separation tank having a built-in filter for removing a phosphoric acid product is provided between the condensation heat exchanger and the water treatment facility.

According to the third aspect of the present invention, the filter in the separation tank can remove the phosphoric acid product in the condensed water. Therefore, the phosphoric acid product does not flow into the water treatment facility, and the load on the water treatment facility can be reduced.

According to a fourth aspect of the present invention, in the phosphoric acid type fuel cell power plant according to the third aspect, the filter is provided with fins on an inner surface and is rotatable about a rotation axis. A drive source for rotating the filter is connected to the shaft.

According to the fourth aspect of the invention, in addition to the same operation as the third aspect of the invention, the filter is rotated to remove the moisture of the phosphoric acid product, thereby preventing the filter from being clogged. A fine, high-performance filter can be used. Therefore, it is possible to reliably prevent the phosphoric acid product from flowing into the water treatment facility, and it is possible to further reduce the load on the water treatment facility.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings, the same portions as those in FIG. 7 which is a conventional example are denoted by the same reference numerals, and description thereof will be omitted.

(1) First Embodiment [Configuration] A first embodiment corresponding to the first aspect of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of the first embodiment. FIG. 2 is a configuration diagram of a main part of the first embodiment.

As shown in FIGS. 1 and 2, in the condensing heat exchanger 8, apart from the pipe for flowing the condensed water to the decarbonation tower 9, the flow direction of the exhaust gas passing through the condensing heat exchanger 8 is smaller than this pipe. Upstream (condensing heat exchanger 8 shown in FIG. 2)
A pipe having the valve 20 is provided immediately downstream of the tube bundle 8a. The valve 20 is openable and closable, and is configured to be opened only when the plant is started. Further, a phosphate condensed water recovery tank 21 is connected to the end of the pipe having the valve 20 separately from the water tank 10 as a tank for recovering the condensed phosphoric acid.

[Effects] In the first embodiment, the valve 20 is opened only when the plant is started, in which the condensed phosphoric acid flows from the condensing heat exchanger 8, and the condensed water recovery tank 21 is opened. Is temporarily collected. In the phosphoric acid condensed water recovery tank 21, the phosphoric acid product and the condensed water can be separated by standing. Then, only the supernatant condensed water can be sent to the water tank 10 by a pump or the like, and returned to the plant system again. On the other hand, the phosphoric acid product after the standing separation can be discharged out of the plant system.
When a predetermined time has elapsed after the start, the valve 20 closes,
The condensed water from the condensing heat exchanger 8 flows to a normal water treatment system (from the decarbonation tower 9 to the water tank 10). The opening and closing of the valve 20 can be automatic or manual.

According to the first embodiment described above,
The phosphoric acid condensed water transiently flowing out at the time of startup is
Since it is possible to temporarily collect the phosphoric acid condensed water into the water treatment facility 11, it is possible to temporarily collect the phosphoric acid condensed water into the water treatment facility 11. As a result, the load on the water treatment facility 11 can be reduced, and a large phosphoric acid treatment capacity is not required. As a result, the size of the water treatment equipment can be reduced, and the plant can be made more compact.

(2) Second Embodiment [Configuration] Referring to FIG. 3, a second embodiment corresponding to the second aspect of the present invention will be described.
An embodiment will be described. FIG. 3 is a main part configuration diagram of the second embodiment. The second embodiment is characterized in that a two-layer water tank 22 is provided.
The two-layer water tank 22 is obtained by integrally providing the conventional water tank 10 with the phosphoric acid condensed water recovery tank 21 of the first embodiment. That is, the water tank 22 includes the phosphoric acid condensed water recovery unit 22a and the water recovery unit 22 connected to the water treatment facility 11.
b.

[Operation and Effect] In the second embodiment as described above, in addition to the operation and effect of the first embodiment, the conventional water tank 10 and the phosphoric acid condensed water recovery tank 21 are combined with each other. Since the role can be fulfilled only by the two-layer water tank 22, it can contribute to further downsizing of the plant.

(3) Third Embodiment [Configuration] A third embodiment corresponding to the third aspect of the present invention will be specifically described with reference to FIGS. FIG. 4 is a main part configuration diagram of the third embodiment, and FIG. 5 is a side sectional view of a separation tank of the third embodiment.

As shown in FIG. 4, a separation tank 23 is provided between the condensation heat exchanger 8 and the decarbonation tower 9. This separation tank 23 has a filter 23 for removing the phosphoric acid product 24.
and a discharge port 23d for taking out condensed water from the separation tank 23 is formed (see FIG. 5). The filter 23a has a mesh size of about several tens of microns, which is the average particle size of the phosphoric acid product 24, and is replaceable.

[Operation and Effect] In the third embodiment, the condensed water that has exited the condensing heat exchanger 8 enters the separation tank 23. Then, the filter 23a in the separation tank 23 removes the phosphoric acid product 24 contained in the condensed water. The condensed water from which the phosphoric acid product 24 has been removed flows from the outlet 23d of the separation tank 23 to the decarbonation tower 9.

According to the third embodiment described above,
Since the filter 23a filters the condensed water, the water treatment equipment 1
No phosphoric acid product 24 flows into 1. Therefore, the load on the water treatment equipment 11 can be reduced, and the plant can be made compact.

(4) Fourth Embodiment [Configuration] A fourth embodiment corresponding to the invention of claim 4 will be specifically described with reference to FIG. 6 which is a side sectional view of a separation tank. As shown in FIG. 6, the fin 23b is provided on the inner surface of the filter 23a, and the filter 23a is configured to be rotatable around a rotation shaft 23c. And the filter 23
The motor 25 is connected to the rotation shaft 23c of the motor a as a drive source for rotating the filter 23a.

[Effects] In the fourth embodiment, the filter 23a is rotated by the operation of the motor 25 and the water attached to the filter 23a is blown off. Clogging with a phosphoric acid product is less likely to occur than in the filter 23a. Therefore, a high-performance filter with a fineness of several microns to several tens of microns, which is close to the minimum particle size of the phosphoric acid product 24, can be used. Therefore, the filter 23a can remove the phosphoric acid product 24 having the minimum particle diameter, and the load on the water treatment facility 11 can be further reduced.

[0035]

According to the phosphoric acid type fuel cell power plant of the present invention, the phosphoric acid condensate can be reduced by a very simple structure including a tank for recovering only the phosphoric acid condensate containing a large amount of phosphoric acid product. Since it is possible to reduce the load on the water treatment facility by discharging the water to the outside of the plant, the size of the water treatment facility can be simplified and contribute to the compactness of the entire plant.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a phosphoric acid fuel cell power plant according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a main part of the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a main part of a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a main part of a third embodiment of the present invention.

FIG. 5 is a side sectional view of a separation tank according to a third embodiment of the present invention.

6A and 6B show a separation tank according to a fourth embodiment of the present invention, in which FIG. 6A is a side sectional view, and FIG. 6B is a view taken along the line AA of FIG.

FIG. 7 is a configuration diagram of a conventional phosphoric acid fuel cell power plant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel cell main body 1a ... Matrix 1b ... Fuel electrode 1c ... Air electrode 1d ... Cooling plate 2 ... Steam separator 2a ... Reforming steam 2b ... Battery cooling water 3 ... Reformer 3a ... Reaction part 3b ... Burner 4 ... reformed gas 5a ... reaction air 5b ... combustion air 6 ... combustion exhaust gas 7 ... exhaust air 8 ... condensation heat exchanger 8a ... tube bundle 9 ... decarbonation tower 10 ... water tank 11 ... water treatment equipment 12 ... air supply Device 20 ... Valve 21 ... Phosphate condensed water recovery tank 22 ... Two-layer water tank 22a ... Phosphate condensed water recovery part 22b ... Water recovery part 23 ... Separation tank 23a ... Filter 23b ... Fin 23c ... Rotating shaft 23d ... Condensed water Outlet 24 ... phosphoric acid product 25 ... motor

Claims (4)

[Claims] 1. A fuel cell body in which a matrix using phosphoric acid as an electrolyte is sandwiched between a fuel electrode and an air electrode, and a reformer for reforming a hydrocarbon-based fuel and supplying a reformed gas to the fuel electrode And an air supply device that supplies reaction air to the air electrode, and takes in combustion exhaust gas discharged from the fuel electrode and exhaust air discharged from the air electrode to convert retained heat and condensed water from these exhaust gases. A phosphoric acid fuel cell power plant comprising: a condensing heat exchanger to be recovered; a water tank for storing the condensed water recovered by the condensing heat exchanger; and a water treatment facility for purifying the water stored in the water tank. In the condensing heat exchanger, a pipe for flowing the condensed water is provided, and a valve that can be opened and closed is installed on the pipe, and the valve contains a large amount of phosphoric acid product in the condensed water flowing in the pipe. In the phosphoric acid condensate A phosphoric acid condensed water recovery tank for recovering the phosphoric acid condensed water is connected to an end of the pipe. . 2. The phosphoric acid-type fuel cell power plant according to claim 1, wherein the water tank is divided into two layers, one of which is configured as the phosphoric acid condensed water recovery tank. 3. A fuel cell main body in which a matrix using phosphoric acid as an electrolyte is sandwiched between a fuel electrode and an air electrode, and a reformer for reforming a hydrocarbon-based fuel and supplying a reformed gas to the fuel electrode And an air supply device that supplies reaction air to the air electrode, and takes in combustion exhaust gas discharged from the fuel electrode and exhaust air discharged from the air electrode to convert retained heat and condensed water from these exhaust gases. A phosphoric acid fuel cell power plant comprising: a condensing heat exchanger to be recovered; a water tank for storing the condensed water recovered by the condensing heat exchanger; and a water treatment facility for purifying the water stored in the water tank. The phosphoric acid-type fuel cell power plant according to any one of claims 1 to 3, wherein a separation tank having a filter for removing a phosphoric acid product is provided between the condensation heat exchanger and the water treatment facility. 4. The filter has a fin provided on an inner surface thereof and is configured to be rotatable about a rotation axis, and a driving source for rotating the filter is connected to a rotation axis of the filter. The phosphoric acid fuel cell power plant according to claim 3, wherein