JPH0684538A - Product water recycling device for fuel cell power generator - Google Patents

Abstract

PURPOSE:To simplify the system structure of a product water recycling device by constituting a direct contact type heat exchanger and a demister of the filling layer of a metallic meshy body to simultaneously serve as a reaction type phosphoric acid collection part and at the same time providing a cleanout operation facilitation means. CONSTITUTION:A direct contact type heat exchanger and a demister comprise a filling layer of a metallic meshy substance and simultaneously act as a reaction type phosphoric acid scavenger part, and at the same time a clean operation facilitation means 21 for periodically cleansing for removal of scavenged water soluble and nonacqueous phosphoric acid compounds is provided. That is, since a product water recycling device 11 simultaneously acts as a phosphoric acid scavenger, so that the operation of cleaning the scavenged phosphoric acid compounds becomes necessary, a means 21 for hermetically coupling the side plate 18 in one of the surfaces of the square tower-like container 12 of the device 11 with the flange 20 of the main body side through a packing 19 is provided. As a result, since the side plate 18 can be removed during the operation of the device and the operation of cleaning the accumulated phosphoric acid compounds and so forth can be easily performed from the outside of the container, the system construction of the device may be simplified and the initial cost thereof and so forth can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a produced water recovery device for recovering the water contained in the exhaust gas of a phosphoric acid fuel cell power generator including a fuel reformer and supplying it to a water treatment device, and more particularly to recovered water. The present invention relates to a structure for reducing phosphoric acid concentration.

[0002]

2. Description of the Related Art A phosphoric acid fuel cell using phosphoric acid as an electrolyte is prepared by steam reforming a raw fuel such as methane gas and hydrogen in the fuel gas and oxygen in the air. It is supplied to the electrode and the air electrode, respectively, and power is generated based on the electrochemical reaction. To reform raw fuel into fuel gas,
A fuel reformer is used in which steam is added to methane as a raw fuel to promote a reaction between water and methane with a catalyst.
Therefore, it is necessary to supply water to the fuel reformer in accordance with the amount of water vapor used for reforming the fuel. As this water, ion-exchanged water (pure water) from which impurities have been removed by an ion-exchange type water treatment device is used, but the water generated by the electrochemical reaction of the fuel cell and the combustion exhaust gas of the fuel reformer burner Since the amount of impurities is smaller than that of tap water when the collected water in which the water content (combustion product water) is condensed is used, and the load on the ion-exchange water treatment device can be lightened accordingly, the product water recovery device can be used in the fuel cell power generator. Is added to collect water in the exhaust gas.

FIG. 4 is a system diagram showing a conventional produced water recovery device and a water treatment device in a phosphoric acid fuel cell power generator. A schematic representation of the phosphoric acid fuel cell 1 has a matrix holding phosphoric acid. And a fuel electrode produced by the fuel reformer 2 are supplied to the fuel electrode, and air is supplied to the air electrode, whereby a fuel cell and an air electrode are arranged. Power is generated. Further, the fuel electrode off-gas 1F discharged from the fuel electrode is sent to the fuel reforming burner 2B to burn the remaining hydrogen, and the combustion heat is used as the reaction heat of the fuel reforming reaction. The combustion exhaust gas 2C containing water (combustion product water) generated by the combustion of the remaining hydrogen, and the air electrode offgas 1A containing water (power generation product water) generated by power generation are sent to the generated water recovery device 3. Collection is done.

The produced water recovery device 3 is, for example, a water recovery tower 3
The heat exchanger 4 cooled by cooling water is housed in A, and the water condensed in the heat exchanger 4 is stored as recovered water 3W in the recovered water tank 3T at the bottom of the water recovery tower 3A. The recovered water 3W is sent to the ion exchange-type water treatment device 8 by the pump 7A, and the water tank 9 serves as makeup water 10 from which impurities are removed.
Is stored in the fuel reformer 2 by the pump 7B and added to the raw fuel as high-temperature steam as necessary.
Used as reaction water required for steam reforming of raw fuel.
Further, the combustion exhaust gas and the air electrode off-gas for which the water collection is completed are discharged to the outside of the system after trapping the water vapor by the demister 3D. A cooling water circulation system for maintaining the phosphoric acid fuel cell 1 at a predetermined operating temperature, or a heat exchanger for recovering exhaust heat of the air electrode offgas 1A and the combustion exhaust gas 2C is also known. , Omitted to avoid complication of explanation.

By the way, water is generated on the oxidizer electrode side by the electrochemical reaction of the phosphoric acid fuel cell 1, and when the generated water is released into the reaction air as water vapor, a small amount of phosphoric acid is involved. The release of phosphoric acid causes scattering of phosphoric acid. Phosphoric acid scattered in the air electrode offgas 1A and discharged from the fuel cell has a very strong corrosive property, corrodes the metal parts on the downstream side of the cell, and collects the recovered water by the generated water recovery device 3. There is a problem of polluting 3W. Therefore, a phosphoric acid collector 6 is connected to the discharge system of the air electrode off-gas 1A, the air electrode off-gas 1A in which the phosphoric acid mist is collected is guided to the generated water recovery device 3, and is cooled by cooling water to be condensed. It is known that the generated water is collected as collected water 3W. Further, as the phosphoric acid collector 6, a cooling system that utilizes the fact that the saturated vapor pressure of phosphoric acid greatly changes depending on the temperature and solidifies and collects phosphoric acid,
A reaction system is known in which phosphoric acid is converted into a phosphoric acid compound, solidified and collected by utilizing the corrosiveness of phosphoric acid against metals.

[0006]

By recovering phosphoric acid with the phosphoric acid collector 6, the concentration of phosphoric acid in the air electrode offgas 3A flowing into the produced water recovery device 3 can be greatly reduced.
The phosphoric acid concentration in the recovered water 3W condensed and recovered in the heat exchanger 4 can be significantly reduced. However, the provision of the phosphoric acid collector 6 causes a new problem that the system configuration of the phosphoric acid fuel cell power generation device becomes complicated, which causes a problem that the initial cost of the device increases. To do.

An object of the present invention is to simplify the system configuration of a phosphoric acid fuel cell power generator by making the produced water recovery device also function as a phosphoric acid collector.

[0008]

In order to solve the above problems, according to the present invention, the produced water contained in the air electrode off-gas discharged from the fuel cell and the combustion exhaust gas discharged from the fuel reformer is provided. A direct contact heat exchanger for recovery, a water tank arranged below it to store recovered water, and a demister arranged on the gas discharge side of the direct contact heat exchanger are housed in a rectangular tower. In the produced water recovery device for supplying the recovered water to the ion-exchange water treatment device while recovering the produced water by countercurrently contacting the recovered water as cooling water with the air electrode off-gas and the combustion exhaust gas, the direct contact heat The exchanger and demister consist of a packed bed of metal mesh, and also serve as a reaction-type phosphoric acid trap, as well as a cleaning operation for regularly washing and removing the trapped water-soluble or water-insoluble phosphate compound. Content And it made comprise means.

Further, the side plate on one surface of the rectangular tower container is
Air-tightly flanged to the body side through packing,
It is provided with means for facilitating the cleaning work for removing and removing the phosphoric acid compound accumulated by removing the side plate while the operation is stopped. Further, the side plate of one side of the rectangular tower vessel facing the direct contact heat exchanger and the demister is airtightly flange-connected to the main body side through packing, and the side plate is removed and accumulated during operation stop. It shall be equipped with means for facilitating the cleaning work for cleaning and removing the phosphoric acid compound.

[0010]

In the structure of the present invention, the direct contact heat exchanger and the demister housed in the rectangular tower of the produced water recovery device are packed beds of metal nets, so that the air discharged from the fuel cell is discharged. A function of collecting the produced water contained in the combustion offgas discharged from the pole off-gas and the fuel reformer in countercurrent contact with the cooling water as the collected water, and the phosphoric acid contained in the air pole off-gas to the metal mesh And a function as a reaction type phosphoric acid trapping portion for trapping as a phosphoric acid compound are obtained, so that recovered water having a low phosphoric acid concentration can be obtained without providing a phosphoric acid trap. ,
The load of the ion exchange resin in the ion exchange type water treatment device can be reduced and the regeneration treatment cycle can be extended.

Further, as a means for facilitating the cleaning work for regularly cleaning and removing the collected water-soluble or water-insoluble phosphoric acid compound, the side plate on one surface of the rectangular columnar container is packed through the main body. It is flange-tightly connected to the side, and the side plate is removed during the operation stop to wash the accumulated phosphate compound,
If configured so that the removal work can be performed, the newly-produced water recovery device can also function as a phosphoric acid collector, facilitating the newly required cleaning work, and stably supplying recovered water with a low phosphoric acid concentration. The function to do is obtained.

Further, as a means for facilitating the cleaning operation, a portion of the side plate on one surface of the rectangular tower-shaped container facing the direct contact heat exchanger and the demister is hermetically flanged to the main body side through packing. With this configuration, it is possible to obtain the function of avoiding the possibility of water leakage in the recovered water tank portion without adversely affecting the cleaning work.

[0013]

EXAMPLES The present invention will be described below based on examples. FIG. 1 is a sectional view schematically showing a produced water recovery device of a fuel cell power generator according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view showing a rectangular tower-shaped container portion in the embodiment. In the figure, the makeup water recovery device 11 has an exhaust 1
Inside the rectangular column-shaped container 12 having a discharge port 12D of 1A, a metal demister, for example, a wire-mesh demister 13 is provided in the vicinity of the discharge port 12D, and a pair of direct contact type heats is divided into two below. It has a structure in which the exchangers 14A and 14B and the recovered water tank 15 are stored on the bottom side,
Nozzle 17 arranged above direct contact heat exchanger 14B
The recovered water 16 in the recovered water tank 15 via the pump 7A
W is supplied and the recovered water 16W is sprayed as cooling water to the direct contact heat exchangers 14A and 14B to cool the direct contact heat exchanger.

The rectangular tower 12 has an inlet 12C for the combustion exhaust gas 2C at an intermediate position in the height direction and an inlet 12A for the air electrode offgas 1A below the inlet 12C, and the inflowing gas is in the direct contact heat exchanger. By being in countercurrent contact with the cooling water 16W sprinkled in, the condensed generated water is collected in the recovered water tank 15 as the recovered water 16W.
Therefore, the direct contact heat exchanger 14A mainly functions to recover water in the air electrode offgas 1A as condensed water, and the direct contact heat exchanger 14B functions to recover water in the combustion exhaust gas 2C as condensed water. To do. Further, the recovered water 16W condensed in the direct contact heat exchanger and mixed in the recovered water tank 15 is partially used as cooling water via the pump 7A, and the remaining part is an ion exchange water treatment device. It is sent to 8 for purification treatment and becomes ion-exchanged water 10 for reuse.

Further, the direct contact heat exchangers 14A and 14B are composed of a packed bed of metal mesh bodies, for example, Raschig rings made of stainless alloy or iron, and the air electrode offgas 1A flowing into the tower vessel 12 from the inlet 12A. , In the process of recovering the produced water discharged from the outlet 12D through the direct contact heat exchangers 14A and 14B, the phosphoric acid mist contained in the air electrode off-gas adheres to the surface of the Raschig ring and is captured, and immediately reacts with the Raschig ring. Then, it becomes a phosphoric acid compound, and is collected by the direct contact heat exchanger as a reactive phosphoric acid collecting section. The phosphoric acid dissolved in the water vapor is collected by the metal demister 13 as a reaction type phosphoric acid collecting section. Therefore, 16 W of recovered water recovered in the recovered water tank 15
Since the concentration of phosphoric acid in the inside can be reduced, the phosphoric acid collector 6 required in the conventional phosphoric acid fuel cell power generator (see FIG. 4) is not required, and the structure of the device can be simplified. Since the load of the ion exchange resin in the ion exchange water treatment device 8 can be reduced and the regeneration treatment cycle can be extended, the regeneration treatment cost and maintenance management cost can be reduced, and the initial and operation of the phosphoric acid fuel cell power generator can be reduced. The effect of reducing the cost can be obtained.

On the other hand, since the produced water recovery device 11 also functions as a phosphoric acid collector, it is necessary to newly clean the collected phosphoric acid compound. Therefore, the produced water recovery device 1
The side plate 18 on one surface of the rectangular tower container 12 of No. 1 is configured to be provided with the cleaning facilitation means 21 having a structure in which the side plate 18 on one surface of the rectangular tower container 12 is airtightly coupled to the flange 20 on the main body side via the packing 19. As a result, the side plate 18 is removed during the operation stop of the phosphoric acid fuel cell power generator, and the Raschig ring of the direct contact heat exchanger 14, the metal demister 13, and the cleaning work of the phosphoric acid compound deposited on the inner wall surface of the container 12 are performed. ， Cleaning work,
Alternatively, since the corroded Raschig ring and the replacement work of the demister can be easily performed from the outside of the container, an increase in maintenance management man-hours due to the produced water recovery device 11 also serving as a phosphoric acid collector is suppressed to a minimum. be able to.

FIG. 3 is a schematic sectional view showing a produced water recovery apparatus according to another embodiment of the present invention, which is a direct contact heat exchanger 14A for the side plate on one surface of the rectangular tower 12.
14B and a portion 28 facing the demister 13 are configured to be airtightly flange-connected to a flange 30 on the main body side via a packing 29, which is different from the above-described embodiment, and the recovered water tank 15 portion has a flange connection structure. The advantage is that the possibility of water leaks caused by doing so can be avoided without affecting the cleaning operation.

In the above-mentioned embodiment, the case where the inlet 12A of the air electrode off-gas 1A is arranged below the inlet 12C of the combustion exhaust gas 2C has been described as an example. It is possible to expect the same action and effect as in the example.

[0019]

As described above, according to the present invention, the direct contact heat exchanger and the demister contained in the rectangular tower of the produced water recovery device are used as the packed bed of the metal net-like body to provide the produced water recovery device. It was constructed so that it also functions as a reaction type phosphoric acid trap. As a result, the phosphoric acid collector that was required in the past to remove the phosphoric acid contained in the air electrode off-gas and prevent the contamination of the recovered water is no longer required, and the system configuration of the phosphoric acid fuel cell power generator is improved. Advantages that can be simplified, reduce the load of ion exchange resin in the ion exchange water treatment equipment, and extend the regeneration treatment cycle, and reduce the initial cost and operating cost of the phosphoric acid fuel cell power generator Is obtained.

Further, the side plate on one surface of the rectangular tower-like container is configured to be detachable so that the produced water recovery device also functions as a reactive phosphoric acid trap, thereby facilitating the required cleaning work. By adopting the means, it becomes possible to easily perform the cleaning operation of the collected phosphoric acid compound from the outside of the tower-like container, and there is an advantage that an increase in maintenance cost can be suppressed to a minimum.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a produced water recovery device of a phosphoric acid fuel cell power generator according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a developed rectangular tower-shaped container portion in the embodiment.

FIG. 3 is a cross-sectional view schematically showing a produced water recovery device according to another embodiment of the present invention.

FIG. 4 is a system diagram showing a conventional produced water recovery device and water treatment device in a phosphoric acid fuel cell power generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Phosphoric acid fuel cell 1A Air electrode off-gas 2 Fuel reformer 2C Combustion exhaust gas 3 Generated water recovery device 3A Moisture recovery tower 3W Recovered water 4 Heat exchanger 5 Demister 6 Phosphoric acid collector 8 Ion exchange water treatment device 11 Generated water recovery device 12 Square tower 12A Air electrode off-gas inlet 12C Combustion exhaust gas inlet 12D Exhaust outlet 13 Metal demister 14A Direct contact heat exchanger 14B Direct contact heat exchanger 15 Recovered water tank 16W Recovered water 17 Nozzle 18 Side plate 19 Packing 20 Flange 21 Means for facilitating cleaning work 28 Side plate 29 Packing 30 Flange 31 Means for facilitating cleaning work

Claims (3)

[Claims] 1. A direct contact heat exchanger for recovering produced water contained in air electrode off-gas discharged from a fuel cell and combustion exhaust gas discharged from a fuel reformer, and recovered water disposed below the heat exchanger. And a demister arranged on the gas discharge side of the direct contact heat exchanger are housed in a rectangular tower, and the recovered water is used as cooling water to countercurrent with the air electrode offgas and the combustion exhaust gas. In the produced water recovery device that collects the produced water by contacting it and supplies the recovered water to the ion exchange type water treatment device, the direct contact heat exchanger and the demister consist of a packed bed of a metal net-like body, and the reaction type A fuel cell power generator characterized in that it also comprises a means for facilitating a cleaning operation which also functions as a phosphoric acid collecting portion and which regularly cleans and removes the collected water-soluble or water-insoluble phosphoric acid compound. Raw Water recovery system. 2. A side plate on one surface of a rectangular tower is hermetically flanged to the main body side via packing, and the side plate can be removed during operation to wash and remove the accumulated phosphoric acid compound. The produced water recovery apparatus for a fuel cell power generator according to claim 1, further comprising means for facilitating cleaning work. 3. A portion of a side plate of one surface of the rectangular tower-like vessel facing the direct contact heat exchanger and the demister is hermetically flanged to the main body side via a packing, and the side plate is kept closed during operation stop. 2. The produced water recovery device for a fuel cell power generator according to claim 1, further comprising means for facilitating a cleaning operation for removing and accumulating the phosphoric acid compound accumulated and removed.