JP2800286B2 - Water recovery device for fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention aims to obtain high-purity water required for steam reforming of raw fuel by recovering generated water contained in off-air of a fuel cell. The present invention relates to a generated water recovery apparatus.

[Conventional technology]

Methane as fuel gas for fuel cells. A hydrogen-rich reformed gas obtained by steam reforming a raw fuel such as methanol is used. On the other hand, since the cell reaction of a phosphoric acid fuel cell is also a reaction that generates water from hydrogen and oxygen, a method is generally known in which this generated water is collected, added to raw fuel, and used for a steam reforming reaction. I have. The water used for the reforming must be of high purity so as not to adversely affect the catalyst in the reformer or to generate scale. The water recovered by condensing the water produced by the battery reaction can be used as raw water added water if it is subjected to simple treatment with high purity.
Although the generated water can be recovered as a drain of a heat exchanger such as an exhaust heat recovery device provided on the outlet air side of the fuel cell, the recovered amount is not sufficient. Therefore, the fact is that the shortage is replenished by treating the clean water with an ion exchange resin or the like.

[Problems to be solved by the invention]

The reason that the amount of generated water is small is that firstly, the gas must be cooled to a temperature as low as possible to obtain sufficient generated water. In other words, the value of exhaust heat from hot water decreases. Second, since the latent heat contained in the generated water is large, a large amount of heat exchange must be performed. However, heat exchange with gas is inefficient per unit area and the heat exchange efficiency is reduced due to the condensed water film. This is because a large heat exchanger must be installed. Thirdly, a large heat-to-heat exchanger causes a large gas pressure loss. However, if the discharge pressure of the reaction air blower supplied by the fuel cell is increased, the power of the blower increases and the efficiency of the entire power generation system decreases. .

An object of the present invention is to provide a small-sized product water recovery device capable of recovering product water that cannot be sufficiently recovered by an exhaust heat recovery device.

[Means for solving the problem]

In order to solve the above-mentioned problems, according to the present invention, provided in a reaction-air outlet-side piping system of a fuel cell, for recovering fuel cell generated water contained in off-air,
An exhaust pipe at the top, a cylindrical body having a recovered water tank at the bottom, and a filler layer disposed in the flow path of the off-air flowing above the recovered water tank and rising toward the exhaust pipe; And a generated water recovery tower having a spray nozzle disposed above the filler layer, and after reducing the temperature of the recovered water in the recovered water tank with a liquid-cooled heat exchanger, the filler is supplied through the spray nozzle. And a collected water circulation system for spraying the collected water into the bed, and a device for collecting generated water of a fuel cell for exchanging heat between the off-air and the filler.

[Action]

In the above-mentioned means, off-air of the fuel cell is sent from below to a filler layer disposed in the generated water recovery tower, and recovered water cooled by a liquid-cooled heat exchanger is sprayed from above by a spray nozzle. By doing so, a counter-current heat exchanger whose heat exchange area is expanded by the filler is formed,
The generated water contained as steam in the off-air can be efficiently condensed and recovered in the recovery water tank at the bottom of the recovery tower. In addition, since the heat exchange area is expanded by the filler layer, the heat exchanger that cools the generated water is made water-cooled, so that it can be smaller than an air-cooled heat exchanger, and the cooling supplied to the filler layer By using high-purity recovered water as the medium, the purity of the recovered water can be maintained at a high level.

EXAMPLES The present invention will be described below based on examples.

FIG. 1 is a schematic sectional view showing a configuration of a product water recovery apparatus according to an embodiment of the present invention. In the figure, the generated water recovery tower 1 is composed of a tubular body having a recovered water tank 4 at the bottom and an exhaust pipe 1B at the top, and a side slightly higher than the liquid level of the recovered water tank 4 whose water level is regulated by an overflow pipe 8A. An inlet pipe 1A for the off-air 19 is provided on the wall surface, and a flow path of the off-air 19 from the inlet pipe 1A to the exhaust pipe 1B is formed. On this flow path, a plastic bead, a plastic pipe, a plastic chip, or the like is formed. And a mist filter 5 made of plastic fiber or the like is provided near the exhaust pipe above the filler layer 2 in which the filler is filled so as not to obstruct the flow of off-air. The filler layer 2 and the mist filter 5
The spray nozzle 3 is provided in between. On the other hand, the recovered water tank 4 and the spray nozzle 3 are connected by a recovered water circulation system 6 having a circulation pump 6A. The recovered water circulation system 6 is provided with a liquid-cooled heat exchanger 7, and the recovered water circulation system 6 is connected to the spray nozzle 3. The recovered water 8 flowing toward the filler layer 2 is cooled by the cooling water flowing through the water-cooled serpentine pipe 7A of the heat exchanger 7, and the cooled recovered water 8A is injected toward the filler layer 2 through the spray nozzle 3 to serve as a filler. After being formed on the surface of the plastic material chip to form a heat exchange surface having a large area, it is dropped into the recovery water tank 4 and collected.

In the product water recovery device configured as described above, the reaction-air outlet-side piping system 11 of the fuel cell 10 is connected to, for example, a phosphate removal device 12 that removes a phosphate mist as an electrolyte and a waste heat recovery device 13. The off air 19 is connected to the inlet pipe 1A.
In this state, the off-air is cooled to such an extent that hot water with high waste heat utilization efficiency is obtained by the exhaust heat recovery device 13, and therefore, although the amount of water generated as water vapor in the off-air is somewhat reduced, It contains a significant amount of product water. The off-air 19 in such a state is applied to the filler layer 2 from below.
The water is efficiently cooled by countercurrent heat transfer, which is in direct contact with the cold recovered water flowing down the pellet-shaped surface, for example, and the product water condensed by cooling is merged with the recovered water flowing down and falls. , And is collected in the collected water tank 4. Since the recovered water 8 thus recovered has sufficient purity for practical use, the recovered water flowing out of the overflow pipe 8A is sent directly to the steam reformer side, or to the steam reformer side through the ion exchange resin. By sending the recovered water, the recovered water can be effectively used as added water necessary for steam reforming of the raw fuel. The off-air from which water has been removed is sent to, for example, a burner of a reformer via an exhaust pipe 1B and used as supporting air.

In the above-described embodiment, the cooled recovered water flowing down the heat exchange surface expanded by the filler and the off air flowing in the opposite direction are in direct contact with each other to perform countercurrent heat transfer, thereby efficiently cooling the off air. To condense the generated steam,
Since the condensed water does not merge with the recovered water flowing down and does not hinder heat transfer, a heat exchanger having high thermal efficiency can be obtained, and thus the product water recovery tower can be downsized.

Also, by configuring the heat exchanger to be liquid-cooled to cool the recovered water circulating through the spray nozzle,
Since heat efficiency is higher than air-cooled heat exchangers, the heat exchanger can be downsized, and the cooling temperature of the heat exchanger can be lowered without adversely affecting the waste heat utilization efficiency of the waste heat recovery device. In addition, generated water that cannot be recovered by the exhaust heat recovery device can be effectively recovered. As a result, the amount of pure water to be replenished through the ion exchange resin can be significantly reduced as compared with the related art, so that the exchange frequency of the ion exchange resin and the amount of use thereof can be reduced.

Furthermore, by using high-purity recovered water as a heat transfer medium for the filler layer, high-purity recovered water can be stably obtained without reducing the purity of condensed water.

In the embodiment, the case where off-air of the fuel cell is supplied to the generated water recovery device via the phosphoric acid removing device or the waste heat recovery device has been described as an example. It goes without saying that both devices may not always be required depending on the purpose of use.

[Effects of the Invention] As described above, the present invention sprays the recovered water cooled by the liquid-cooled heat exchanger onto the filler layer in the generated water recovery tower from above, with the off air flowing in the opposite direction. It was configured to conduct countercurrent heat transfer in direct contact. As a result, high heat exchange efficiency can be obtained, and the generated water recovery tower and the heat exchanger can be miniaturized, and the generated water of the fuel cell, which has not been conventionally used due to the restriction of the exhaust heat utilization efficiency, can be efficiently recovered and used. A fuel cell power generation system including the generated water recovery device can be provided. Further, since the additional supply amount of pure water decreases due to an increase in the recovered water, the ion exchange resin used in the production of pure water and the number of exchange cycles thereof also decrease, and therefore, an advantage that the running cost of the entire power generation system can be reduced is obtained. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a produced water recovery apparatus according to an embodiment of the present invention. 1 ... generated water recovery tower, 2 ... filler layer, 3 ... spray nozzle, 4 ... recovered water tank, 5 ... mist filter,
6 ... recovered water circulation system, 7 ... heat exchanger, 8 ... recovered water,
10 ... fuel cell, 11 ... outlet side piping system, 19 ... off air.

Claims (1)

(57) [Claims] The present invention is provided in a piping system on the outlet side of reaction air of a fuel cell for recovering water generated by the fuel cell contained in off-air, and has an exhaust pipe at an upper part and a recovered water tank at a bottom part. A filler layer formed of a cylindrical body, disposed above the recovered water tank, and disposed in the flow path of the off-air rising toward the exhaust pipe, and a spray disposed above the filler layer A product water recovery tower having a nozzle, and a recovered water circulation system that sprays the recovered water in the recovered water tank toward the filler layer through the spray nozzle after lowering the temperature with a liquid-cooled heat exchanger. Wherein a heat exchange is performed between the off-air and the filler.