JP3132627B2 - Water recovery system for fuel cell power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water recovery apparatus for recovering water in exhaust gas of a fuel cell power generator including a fuel reformer and supplying the recovered water to a water treatment apparatus, and more particularly to recovered water recovered from combustion exhaust gas. The present invention relates to a water recovery apparatus having a function of reducing the concentration of carbon dioxide.

[0002]

2. Description of the Related Art Phosphoric acid type fuel cells using phosphoric acid as an electrolytic solution convert hydrogen in fuel gas and oxygen in air obtained by steam reforming a raw fuel such as methane gas into a fuel cell. They are supplied to a fuel electrode and an air electrode, respectively, and generate power based on an electrochemical reaction. For reforming raw fuel into fuel gas, a fuel reformer is used, which adds steam to methane as raw fuel and promotes the 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 steam used for reforming the fuel. As this water, ion-exchanged water from which impurities have been removed by an ion-exchange type water treatment device or the like is used. However, water generated by the electrochemical reaction of the fuel cell or water (combustion) in the combustion exhaust gas of the fuel reforming substrate burner is used. The use of recovered water condensed (produced water) has less impurities than tap water, and the load on the ion-exchange type water treatment device can be reduced by that amount. Therefore, a water recovery device is usually added to the fuel cell power generator. Measures have been taken to recover the moisture in the exhaust.

FIG. 3 is a block diagram showing a conventional make-up water recovery and treatment system in a fuel cell power generator. In the figure, a fuel cell main body 1 is schematically shown, and is composed of a laminate of unit cells in which a fuel electrode and an air electrode are arranged with a matrix holding phosphoric acid therebetween. By supplying the fuel gas generated by the fuel reformer 2 to the fuel electrode and supplying air to the air electrode, power is generated based on an electrochemical reaction. The off-gas from the fuel electrode is sent to the fuel reforming burner 2B, where the remaining hydrogen is burned, and the heat of combustion is used as the reaction heat of the fuel reforming reaction. Combustion exhaust gas 2 containing water generated by the combustion of hydrogen (combustion water)
The air off-gas 1A containing G and water generated by power generation (power generation water) is sent to the water recovery device 3 to recover water. The water recovery device 3 has, for example, a structure in which a water-cooled heat exchanger 5 is housed in a water recovery tower 4, and water condensed by the heat exchanger 5 is stored as recovered water 6 at the bottom of the water recovery tower 4. The recovered water 6 is sent to an ion-exchange type water treatment device 8 by a pump 7A, accumulated in a water tank 9 as makeup water 10 from which impurities have been removed, and sent to a fuel reformer 2 by a pump 7C as necessary. Is added to the raw fuel as high-temperature steam, and is used as reaction water required for steam reforming of the raw fuel.

[0004]

The recovered water obtained by condensing flue gas with a heat exchanger contains carbon dioxide having a saturation concentration proportional to the carbon dioxide concentration in the flue gas. Therefore, a large amount of carbon dioxide gas is dissolved in the conventional recovered water obtained by condensing the moisture in the exhaust gas in which the combustion exhaust gas and the air off-gas are mixed by one heat exchanger. When such recovered water is supplied to the ion-exchange type water treatment apparatus, the carbon dioxide gas acts as a load on the ion-exchange resin, and the regeneration cycle of the ion-exchange resin is shortened. The problem of increase occurs. If the recovered water is degassed to remove carbon dioxide gas and then supplied to the ion-exchange type water treatment apparatus,
The regeneration cycle of the ion exchange resin can be extended, but this requires the installation of a new degassing tower and its power, which leads to complicated equipment, upsizing and economic disadvantages, as well as auxiliary equipment for the equipment. The problem that loss increases and efficiency falls arises.

[0005] An object of the present invention is to provide a recovery apparatus capable of generating recovered water with a small amount of carbon dioxide gas without causing the equipment to be complicated and large-sized and lowering the power generation efficiency, thereby extending the regeneration cycle of the ion exchange resin. To obtain a fuel cell power generator.

[0006]

In order to solve the above-mentioned problems, in the present invention, water contained in air off-gas discharged from a fuel cell body and combustion exhaust gas discharged from a fuel reformer is recovered. In a water recovery system of a fuel cell power generator, which is supplied to an ion-exchange type water treatment system and is used as make-up water for fuel reforming, (1) air off-gas and combustion exhaust gas are introduced, and the supplied cooling water Moisture contained by direct contact is condensed and collected, and a moisture collection tower that discharges treated gas and an air off-gas are introduced to directly contact the supplied cooling water to condense and collect the contained moisture. And a decarbonation tower for discharging the treated gas is communicated via a throttle mechanism in a water tank provided at each lower part, and recovered water (condensed water) of a water tank provided at the lower part of the moisture recovery tower. To cooler After the, a part as the cooling water supplied to the water recovery column, and the cooling water and supplies the remainder decarboxylation tower. Further, the recovered water (decarbonated water) of the water tank provided at the lower part of the decarbonation tower is set so that its water level is always higher than the level of the recovered water of the water tank provided at the lower part of the water recovery tower. Hold it and supply it to the ion exchange type water treatment equipment.

(2) In the above, the water recovery tower is further provided with a water supply port for supplying water purified by the ion exchange type water treatment apparatus. (3) Further, in the above, the water recovery tower and the decarbonation tower are disposed adjacent to each other in the same vessel, and the air offgas introduced together with the combustion exhaust gas into the water recovery tower as the air offgas after passing through the decarbonation tower, In addition, the air off-gas and the combustion exhaust gas from which the moisture has been removed by the moisture recovery tower and the decarbonation tower are discharged from the same outlet.

[0008]

According to the present invention, the water contained in the air off-gas discharged from the fuel cell main body and the flue gas discharged from the fuel reformer is recovered and supplied to an ion-exchange type water treatment apparatus for fuel reforming. As described in (1) above, the water recovery device of the fuel cell power generator, which is used as make-up water for water supply, is provided with a moisture recovery tower that directly contacts and collects water contained in the air off-gas and combustion exhaust gas with the cooling water, A decarbonation tower for recovering the water contained in the off-gas by directly contacting with the cooling water, and communicating between the water tanks attached to each lower part through a throttle mechanism,
After the condensed water collected in the water tank of the water recovery tower is sent to the cooler to cool, a part of the water is supplied to the water recovery tower, and the remaining part is supplied to the decarbonation tower as cooling water. The decarbonated water collected in the water tank is kept at a level that is always higher than the level of condensed water in the water tank of the water recovery tower, and is supplied to the ion-exchange type water treatment apparatus. The decarbonated water of the decarbonation tower flows to the water tank of the water recovery tower, and especially flows through the throttle mechanism at a certain speed, so the condensed water diffuses into the decarbonated water and flows into the water tank of the decarbonation tower. Is prevented.

The combustion exhaust gas containing carbon dioxide gas is introduced into the water recovery tower and taken into the condensed water. The condensed water is not only the cooling water supplied to the water recovery tower but also the cooling water supplied to the decarbonation tower. The water is diluted with a large amount of water to which decarbonated water flows into the water tank of the water recovery tower through the above-described throttle mechanism. Therefore, the carbon dioxide concentration of the cooling water which is cooled again by the cooler and supplied to the decarbonation tower and the water recovery tower is maintained at a low level, so that the decarbonation supplied to the ion-exchange type water treatment apparatus is maintained. The concentration of carbon dioxide contained in water can be suppressed to a low level, and the burden on the ion exchange resin can be reduced.

Further, if the water recovery tower is provided with a water supply port for supplying the water purified by the ion-exchange type water treatment apparatus as described in the above (2), not only the water recovery tower but also the water recovery port is provided at the same time. Also for the decarbonation tower, it is possible to effectively secure the initial water or adjust the shortage of the recovered water. Further, as described in (3) above, the water recovery tower and the decarbonation tower are arranged adjacent to each other in the same vessel, and the air offgas introduced into the water recovery tower together with the combustion exhaust gas is supplied to the air offgas after passing through the decarbonation tower. If it is assumed that the air off-gas and the combustion exhaust gas from which moisture has been removed in the water recovery tower and the decarbonation tower are to be discharged from the same outlet, the ion-exchange water treatment is performed from the decarbonation tower as described in (1) above. The concentration of carbon dioxide contained in the decarbonated water supplied to the apparatus can be suppressed to a low level, and a water recovery apparatus having a small installation area and high economic efficiency can be obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 is a sectional view schematically showing a first embodiment of a water recovery device for a fuel cell power generator according to the present invention. In the figure, a water recovery device includes a water recovery tower 11 and a decarbonation tower 1.
2. In the water recovery tower 11, a nozzle 13A for water sprinkling is provided at an upper part, and collected water (condensed water) 6A which is communicated with a water tank 15B of a decarbonation tower 12 to be described later via a throttle 16 is stored at a lower part. A water tank 15A is provided, and an air off-gas supply port 17A, a combustion exhaust gas supply port 18, and a replenishment water supply port 20 are provided above the water tank 15A. Also, in the decarbonation tower 12,
A nozzle 13B for sprinkling water is provided at an upper part, and a water tank 15B for storing recovered water (decarbonated water) 6B is provided at a lower part, and an air off-gas supply port 17 is provided at an upper part of the water tank 15B.
B is provided. Liquid-to-liquid cooler 2 by pump 7B
1 and cooled by heat exchange with the low-temperature cooling water, a part of the recovered water is sprinkled by the nozzle 13A to the packed bed 14A of the water recovery tower 11, and the air off-gas supply port 17A
And the air off-gas 1 introduced from the flue gas supply port 18
By directly contacting with A and the combustion exhaust gas 2G, the water in these gases is condensed and stored in the water tank 15A as recovered water (condensed water) 6A. On the other hand, the remaining portion of the recovered water is sprinkled by the nozzle 13B onto the packed bed 14B of the decarbonation tower 12, and is brought into direct contact with the air off-gas 1A introduced from the air off-gas supply port 17B to condense water and collect the recovered water (dewatering) into the water tank 15B. (Carbonated water) 6B. Water tank 15
The level of the recovered water (decarbonated water) 6B stored in B is kept higher than the level of the recovered water (condensed water) 6A stored in the water tank 15A, and a part of the decarbonated water 6B is
To the water tank 15A, and together with the condensed water 6A, is sent to the liquid-to-liquid cooler 21 to be recovered water to be cooled. The remainder of the decarbonated water 6B is sent to the ion-exchange type water treatment device 8 by the pump 7A to be purified, and is sent to a fuel reformer (not shown) as necessary.

In this configuration, the carbon dioxide gas in the flue gas 2G introduced from the flue gas supply port 18 of the water recovery tower 11 is diluted by a large amount of recovered water. Decarbonated water 6 sent to
The carbon dioxide gas concentration of B can be kept low, and the regeneration cycle of the ion exchange resin can be lengthened. The aperture 16
The condensed water 6A
In the water tank 15B, and at the same time, adhesion of foreign matter can be prevented. Also,
The replenishing water supply port 20 provided at the upper part of the water tank 15A of the moisture recovery tower 11 is for replenishing clean water for securing initial water or adjusting for lack of recovered water. . If this water supply port 20 is used, the water recovery tower 1
In addition to replenishing the water tank 15A, the decarbonation tower 1
Replenishment to the second water tank 15B is also possible at the same time, and there is no need to provide a separate water supply port in the decarbonation tower 12 for efficiency.

FIG. 2 is a cross-sectional view schematically showing a second embodiment of the water recovery apparatus for a fuel cell power generator according to the present invention. Components having the same functions as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The difference between the second embodiment and the first embodiment is that the water recovery tower 11 and the decarbonation tower 1
2 is provided adjacently, and as an alternative to the air off gas supply port 17A of the first embodiment, the air off gas 1A passing through the An air off-gas inlet 22 for sending to the decarbonation tower 12 is provided, and a gas outlet 19 sharing these functions is provided instead of the gas outlets 19A and 19B of the first embodiment. Is to be. In this configuration, the carbon dioxide concentration of the decarbonated water 6B sent to the ion-exchange type water treatment device 8 is suppressed to be low similarly to the water recovery device of the fuel cell power generation device of the first embodiment, and the ion-exchange resin is regenerated. The cycle can be lengthened, and a water recovery device with a small installation area and high economic efficiency can be obtained.

[0014]

According to the present invention, the water contained in the air off-gas discharged from the fuel cell main body and the flue gas discharged from the fuel reformer is recovered and supplied to the ion-exchange type water treatment apparatus. A water recovery device of a fuel cell power generator as a make-up water for reforming, (1) introducing the air off-gas and the combustion exhaust gas,
A moisture recovery tower that directly contacts the supplied cooling water to condense and recover the contained water, and discharges the treated gas;
Introducing the air-off gas, condensing and recovering the contained water by directly contacting the supplied cooling water, and a decarbonation tower for discharging the treated gas, in a water tank attached to each lower part. The cooling water is conveyed through a throttle mechanism, and the recovered water (condensed water) in a water tank attached to the lower part of the water recovery tower is sent to a cooler to be cooled, and a part of the water is supplied to the water recovery tower. Cooling water, the rest of which is the cooling water supplied to the decarbonation tower, and the recovered water (decarbonated water) in a water tank attached to the lower part of the decarbonation tower,
The water level is maintained at a position that is always higher than the level of the recovered water in a water tank attached to the lower part of the water recovery tower,
Since it is supplied to the ion-exchange type water treatment equipment, it is possible to keep the carbon dioxide concentration of the decarbonated water sent to the ion-exchange type water treatment equipment low. A water recovery device for a fuel cell power generator with a long regeneration cycle of an ion exchange resin can be obtained without lowering the power generation efficiency.

(2) In the above, the water recovery tower is further provided with a replenishing water supply port for supplying water purified by the ion exchange type water treatment apparatus. There is no need to install a water supply port, and it is possible to obtain a water recovery device for a fuel cell power generation device that can efficiently secure initial water or adjust for shortage of recovered water. (3) Further, in the above, the water recovery tower and the decarbonation tower are disposed adjacent to each other in the same vessel, and the air offgas introduced together with the combustion exhaust gas into the water recovery tower as the air offgas after passing through the decarbonation tower, Since the air off-gas and the combustion exhaust gas from which water has been removed in the water recovery tower and the decarbonation tower are discharged from the same outlet, the carbon dioxide concentration of the decarbonated water sent to the ion-exchange type water treatment equipment is low. Not only can the regeneration cycle of the ion-exchange resin be suppressed to be prolonged, but also a water recovery device for a fuel cell power generator with a small installation area and high economic efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a first embodiment of a water recovery device for a fuel cell power generator according to the present invention.

FIG. 2 is a cross-sectional view schematically showing a second embodiment of the water recovery device for a fuel cell power generator according to the present invention.

FIG. 3 is a configuration diagram showing a conventional make-up water recovery and treatment system in a fuel cell power generator.

[Explanation of symbols]

 Reference Signs List 1 phosphoric acid type fuel cell 1A air off-gas 2 fuel reformer 2G combustion exhaust gas 3 conventional water recovery device 6A recovered water (condensed water) 6B recovered water (decarbonated water) 7A pump 7B pump 7C pump 8 Ion exchange type water treatment Apparatus 11 Moisture recovery tower 12 Decarbonation tower 13A nozzle 13B nozzle 14A packed bed 14B packed bed 15A water tank 15B water tank 16 throttle 17A air off gas supply port 17B air off gas supply port 18 combustion exhaust gas supply port 19 gas discharge port 19A gas discharge port 19B Gas outlet 20 Water supply port 21 Liquid-to-liquid cooler 22 Air off-gas flow port

Claims (3)

(57) [Claims] 1. A method for recovering water contained in air off-gas discharged from a fuel cell body and combustion exhaust gas discharged from a fuel reformer, supplying the recovered water to an ion-exchange type water treatment apparatus, and supplying water for fuel reforming. In the water recovery apparatus for a fuel cell power generation apparatus, the air off-gas and the combustion exhaust gas are introduced, and the water contained therein is brought into direct contact with the supplied cooling water to condense and recover the contained water and discharge the treated gas. And a decarbonation tower that introduces the air off-gas, condenses and collects the water contained by directly contacting the supplied cooling water, and discharges the treated gas, at the bottom of each. In the attached water tank, it communicates via a throttle mechanism, sends the collected water in the water tank attached to the lower part of the water recovery tower to a cooler, cools it, and then supplies a part of the water to the water recovery tower. Cooling water The remaining part is used as the cooling water to be supplied to the decarbonation tower, and further, the decarbonation tower uses the recovered water of a water tank provided at the lower part, and the water level is provided at the lower part of the water recovery tower. A water recovery device for a fuel cell power generation device, wherein the water recovery device keeps the water level at a level higher than the level of recovered water in a water tank and supplies the water to an ion-exchange type water treatment device. 2. The water recovery device for a fuel cell power generator according to claim 1, wherein the water recovery tower is provided with a water supply port for supplying water purified by an ion exchange type water treatment device. 3. The water recovery tower and the decarbonation tower are arranged adjacent to each other in the same vessel, and air off-gas introduced into the water recovery tower together with combustion exhaust gas is used as air off-gas after passing through the decarbonation tower. The water of the fuel cell power generator according to claim 1 or 2, wherein the air off-gas from which water has been removed by the water recovery tower and the decarbonation tower and the combustion exhaust gas are discharged from the same discharge port. Collection device.