Method and device for operating a fuel cell system

Claim 3

The method according to claim 1, wherein the fresh gas is added in the area of cathode inlet.

Claim 4

The method according to claim 1, wherein the cathode gas is caused to circulate by a blower device located inside protective housing.

Claim 5

The method according to claim 1, wherein the circulating cathode gas is fed through a heat exchanger to decouple useful heat.

Claim 6

The method according to claim 1, comprising the further step of guiding said circulating cathode gas through a catalytic combustion device to burn flammable residues of added anode gas.

Claim 7

The method according to claim 4, wherein catalytic combustion takes place in heat exchanger.

Claim 8

A gas circulation arrangement for a fuel cell system of the type in which fuel cells arranged in a stack are surrounded by a protective housing with an anode inlet for adding combustion gas to the anodes of the fuel cells, an anode outlet for carrying away the burnt combustion gas from the anodes, a cathode inlet for adding cathode gas to the cathodes of the fuel cells, and a cathode outlet for carrying away the used cathode gas from the cathodes, as well as with a combustion gas inlet device which provides a seal with respect to the interior of protective housing for supplying the combustion gas to anode inlet, said arrangement comprising: a cathode outlet of the fuel cell stack which opens to discharge used cathode gas inside the protective housing; a blower device provided inside the protective housing for causing the used cathode gas to circulate to the cathode inlet of the fuel cell stack inside protective housing; an anode outlet of the fuel cell stack which opens to discharge burnt anode gas inside the protective housing, whereby the burnt anode gas is mixed with a used cathode gas stream circulating inside protective housing; and an air intake for replacing a portion of the gas mixture circulating inside the protective housing with fresh gas from the outside the housing.

Claim 9

A gas circulation arrangement for a fuel cell system of the type in which fuel cells arranged in a stack are surrounded by a protective housing with an anode inlet for adding combustion gas to the anodes of the fuel cells, an anode outlet for carrying away the burnt combustion gas from the anodes, a cathode inlet for adding cathode gas to the cathodes of the fuel cells, and a cathode outlet for carrying away the used cathode gas from the cathodes, as well as with a combustion gas inlet device which provides a seal with respect to the interior of protective housing for supplying the combustion gas to anode inlet, said arrangement comprising: a cathode outlet of the fuel cell stack which opens to discharge used cathode gas inside the protective housing; a blower device provided inside the protective housing for causing the used cathode gas to circulate to the cathode inlet of the fuel cell stack inside protective housing; an anode outlet of the fuel cell stack which opens to discharge burnt anode gas inside the protective housing, whereby the burnt anode gas is mixed with a used cathode gas stream circulating inside protective housing; and an air intake for replacing a portion of the gas mixture circulating inside the protective housing with fresh gas from the outside the housing.

Claim 10

The gas circulation arrangement according to claim 7, wherein a heat exchanger is provided inside the protective housing for decoupling useful heat from the circulating cathode gas stream.

Claim 11

The gas circulation arrangement according to claim 8, wherein the heat exchanger is located upstream from cathode inlet of the fuel cell stack.

Claim 12

The gas circulation arrangement according to claim 9, wherein a space between an outlet side of the heat exchanger and the cathode inlet is sealed off from an interior of protective housing.

Claim 13

The gas circulation arrangement according to claim 8, further comprising means for catalytic combustion of flammable residues of the anode gas added to the circulating cathode gas stream.

Claim 14

The gas circulation arrangement according to claim 11, wherein the means for catalytic combustion comprise a catalytic coating on a surface of heat exchanger that is exposed to the circulating gas mixture.

Claim 15

The gas circulation arrangement according to claim 7, wherein the blower device has a drive located outside protective housing, said drive being coupled with the blower device by a drive shaft guided through the protective housing, said shaft being designed so that fresh gas can be supplied through the drive shaft to cool it.

Claim 16

The gas circulation arrangement according to claim 7, wherein an overpressure flap is provided to discharge surplus exhaust gas from protective housing.

Claim 17

The gas circulation arrangement according to claim 8, wherein the heat exchanger is mounted on upper and lower end plates of the fuel cell stack.

Claim 18

The gas circulation arrangement according to claim 9, wherein a surrounding gap between the heat exchanger and the fuel cell stack is closed by a continuous seal.

Claim 19

The gas circulation arrangement according to claim 16, wherein the seal comprises fibers made from a material selected form the group consisting of glass and ceramic.

Claim 20

The gas circulation arrangement according to claim 16, wherein the seal comprises a brush.