Method and device for purifying air for fuel cells

#The invention relates to auxiliary systems ensuring functioning of alkaline fuel cells (AAFC), in particular to a method and device for sorptive purification of air used in an AFC of carbon dioxide.

#Atmospheric ambient air is often used as the oxidant in an AFC. There are from 200 to 400 ppm of carbon dioxide in ambient air, which, reacting with the alkaline electrolyte, form carbonates which to a significant degree impair the load characteristics of the AFC. In order to increase the lifetime of the air electrodes of the AFC, deep purification of the air of carbon dioxide is necessary.

#A method for removing carbon dioxide from the air used in an AFC is known (U.S. Pat. No. 5,595,949, class B 01 J 20/34, 21 Jan. 1997). The method comprises passing air through replaceable containers provided with granules of a porous material, which are impregnated with an alkaline solution. After utilization, the containers with spent material are removed from the device and subjected to regeneration. Regeneration is carried out by decomposing thermally the granules at temperatures of 900-1400° C., at which the carbonates are removed. After decomposing the granules are subjected to hydrolyzation to form alkalis.

#FIG. 1 shows one variant of the basic pneumatic diagram of the claimed device.

#FIG. 2 shows another variant of the basic pneumatic diagram of the claimed device.

#FIG. 3 shows a section view of a possible variant of embodiment of the construction of an adsorber 3.

#Another variant of embodiment of the device for purification of air (FIG. 2) comprises an air flow blower (compressor or ventilator) 1, connected to an inlet of one of the adsorbers 3(1) and 3(2) positioned in one housing and separated by a partition 7. A heater 4 is mounted at an inlet to one of the adsorbers (regenerated) connected to an outlet of the AFC 6.

#The proposed method is realized in the following manner. A sorbent on the base of hydrated oxides of transition metals in the form of granules having a size of 1.5-2 mm or in the form of blocks with ducts of different diameter is loaded into the adsorbers 3(1) and 3(2). Then heaters 4(1) and 4(2) are mounted at the inlets of the adsorbers and the adsorbers are connected through flow switches 2 and 5 to the flow blower 1 and fuel cell 6 as is shown in the diagram of FIG. 1. After that the air flow blower 1 is turned on and the starting air at room temperature (15-25° C.) is fed through the flow switch 2 to the adsorber 3(1) in which deep removal of carbon dioxide is carried out as a result of interaction of the latter with the sorbent. Air purified of carbon dioxide is fed through a turned-off heater 4(1) and a flow switch 5 to the inlet of the fuel cell 6 in which the process of generation of electric power takes place as a result of oxidation of hydrogen by oxygen of air and production of water vapors. Wherein, spent moist air with a reduced content of oxygen through the outlet of the fuel cell 6 is fed through the flow switch 5 to the heater 4(2) in which the air used in the fuel cell is heated to a temperature of 60-120° C. and fed to the outlet of the adsorber 3(2). Wherein regeneration of the adsorbent takes place with desorption of carbon dioxide. The air leaving an adsorber is discharged into the atmosphere through the switch 2, since it is not suitable for further use because of the presence of carbon dioxide and the low content of oxygen. After the process of desorbing is over, the switches 2 and 5 are set to the second position (shown by dotted line). Wherein the starting air is purified of carbon dioxide in the adsorber 3(2), while the adsorber 3(1) is set to the regeneration mode. Wherein the time of sorption is kept equal to the regeneration time. In the device executed in accordance with FIG. 2, one of the inlets of the adsorbers is constantly connected to the air flow blower 1, another inlet is constantly connected through the heater 4 to the outlet of the AFC 6. Switching the adsorbers for purification of the air or for regeneration is carried out by rotating the adsorbers about a longitudinal axis. One adsorber, connected to the blower, purifies air entering the AFC, the other, connected to the outlet of the AFC, regenerates. Then the adsorbers change places by rotation about the axis.

#Example of Realization.