US6849352B2 — Fuel cell system and method of operating a fuel c…

Claim 1

Independent Claim 193 words

A fuel cell system comprising a plurality of fuel cells, in particular in the form of low temperature fuel cells, which are assembled into a stack and are adapted to permit oxygen or an oxygen containing gas to react with hydrogen or a hydrogen containing gas to generate electricity and produce first exhaust gases containing residual oxygen and second exhaust gases containing residual hydrogen, said system comprising: a cathode side with a cathode inlet for receiving said oxygen or oxygen containing gas and a cathode outlet for said first exhaust gases; an anode side with an anode inlet for receiving said hydrogen or hydrogen containing gas, an anode outlet for said second exhaust gases; a feedback loop for returning at least a part of the second exhaust gases arriving at the anode outlet back to the anode inlet; and a line which leads from the anode side to the cathode side and is designed to supply second exhaust gases to the cathode inlet which, after reaction of said residual hydrogen with oxygen at said cathode side to form water, leave the fuel cell system with said first exhaust gases via said cathode outlet.

Claim 2

Dependent Claim 193 words

A fuel cell system comprising a plurality of fuel cells, in particular in the form of low temperature fuel cells, which are assembled into a stack and are adapted to permit oxygen or an oxygen containing gas to react with hydrogen or a hydrogen containing gas to generate electricity and produce first exhaust gases containing residual oxygen and second exhaust gases containing residual hydrogen, said system comprising: a cathode side with a cathode inlet for receiving said oxygen or oxygen containing gas and a cathode outlet for said first exhaust gases; an anode side with an anode inlet for receiving said hydrogen or hydrogen containing gas, an anode outlet for said second exhaust gases; a feedback loop for returning at least a part of the second exhaust gases arriving at the anode outlet back to the anode inlet; and a line which leads from the anode side to the cathode side and is designed to supply second exhaust gases to the cathode inlet which, after reaction of said residual hydrogen with oxygen at said cathode side to form water, leave the fuel cell system with said first exhaust gases via said cathode outlet.

Claim 3

Dependent Claim 31 words

A fuel cell system in accordance with claim 1 , said system further having a switching valve which can be switched on and off and which is provided in said line.

Claim 4

Dependent Claim 31 words

A fuel cell system in accordance with claim 1 , said system further having a control valve which controls or regulates the quantity of second exhaust gases flowing through said line.

Claim 5

Dependent Claim 29 words

A fuel cell system in accordance with claim 3 , characterized in that said control valve is provided in said line at the downstream side of the switching valve.

Claim 6

Dependent Claim 93 words

A fuel cell system in accordance with claim 1 , said anode side of said fuel cell system belonging to an anode circuit including said feedback loop, said system further having a branch point in said anode circuit at which said line branches off from said anode circuit, a hydrogen supply point for supplying said hydrogen or hydrogen containing gas to said anode circuit, said hydrogen supply point being provided in said anode circuit downstream of said branch point, and a non-return valve provided between said hydrogen supply point and said branch point.

Claim 7

Dependent Claim 23 words

A fuel cell system in accordance with claim 5 , said system further having an exhaust gas pump provided in the anode circuit.

Claim 8

Dependent Claim 28 words

A fuel cell system in accordance with claim 6 , said branch point for said line being provided in said anode circuit downstream of said exhaust gas pump.

Claim 9

Dependent Claim 28 words

A fuel cell system in accordance with claim 6 , said branch point for said line being provided in said anode circuit upstream of said exhaust gas pump.

Claim 10

Dependent Claim 32 words

A fuel cell system in accordance with claim 6 , said anode exhaust gas pump being adapted to be driven by the hydrogen or hydrogen containing gas supplied to said anode circuit.

Claim 11

Dependent Claim 41 words

A fuel cell system in accordance with claim 1 , there being a fuel cell catalyst at said cathode side for the reaction of said residual hydrogen of said second exhaust gases with oxygen at the cathode side to form water.

Claim 12

Dependent Claim 63 words

A fuel cell system in accordance with claim 1 , said cathode side including a cathode supply line for supplying said oxygen or oxygen containing gas to said cathode inlet, a catalyst being provided as a coating within said cathode supply line, said line being designed to lead said second exhaust gases to said cathode supply line upstream of said fuel cell catalyst.

Claim 13

Dependent Claim 46 words

A fuel cell system in accordance with claim 1 , said cathode side including a heat exchanger with a catalyst coating arranged before said cathode inlet and said line being designed to lead said second exhaust gases to said cathode side upstream of said heat exchanger.

Claim 14

Dependent Claim 57 words

A fuel cell system in accordance with claim 1 , said cathode side including a housing disposed upstream of said cathode inlet, a flow permeable body accommodated in said housing and coated with a catalyst, said line being designed to supply the anode exhaust gases directly or indirectly into said housing and thus to said cathode side.

Claim 15

Dependent Claim 18 words

A fuel cell system in accordance with claim 13 , said flow permeable body comprising a material network.

Claim 16

Dependent Claim 18 words

A fuel cell system in accordance with claim 13 , said flow permeable body comprising a porous monolith.

Claim 17

Dependent Claim 68 words

A fuel cell system in accordance with claim 1 , said system further having an exhaust gas mixing device located downstream of said cathode outlet, a second line which leads from said anode side to said exhaust gas mixing device, said exhaust gas mixing device being designed to mix second exhaust gases branched off via said second line with said first exhaust gases received from said cathode outlet.

Claim 18

Dependent Claim 21 words

A fuel cell system in accordance with claim 16 , said system further having a valve incorporated into said second line.

Claim 19

Independent Claim 211 words

A method of operating a fuel cell system comprising a plurality of fuel cells, in particular in the form of low temperature fuel cells, assembled into a stack and are adapted to permit oxygen or an oxygen containing gas to react with hydrogen or a hydrogen containing gas to generate electricity and produce first exhaust gases containing residual oxygen and second exhaust gases containing residual hydrogen, said system comprising: a cathode side with a cathode inlet for receiving said oxygen or oxygen containing gas and a cathode outlet for said first exhaust gases; an anode side with an anode inlet for receiving said hydrogen or hydrogen containing gas, an anode outlet for said second exhaust gases; and a feedback loop for returning at least a part of the second exhaust gases arriving at the anode outlet back to the anode inlet, said method comprising the step of supplying at least a part of said second exhaust gases continuously or discontinuously to said cathode inlet and discharging them with said first exhaust gases from said fuel cell system, with said residual hydrogen contained in said second exhaust gases being reacted with said oxygen or oxygen containing gas at said cathode side to form water at the catalyst present at said cathode side.

Claim 20

Independent Claim 211 words

A method of operating a fuel cell system comprising a plurality of fuel cells, in particular in the form of low temperature fuel cells, assembled into a stack and are adapted to permit oxygen or an oxygen containing gas to react with hydrogen or a hydrogen containing gas to generate electricity and produce first exhaust gases containing residual oxygen and second exhaust gases containing residual hydrogen, said system comprising: a cathode side with a cathode inlet for receiving said oxygen or oxygen containing gas and a cathode outlet for said first exhaust gases; an anode side with an anode inlet for receiving said hydrogen or hydrogen containing gas, an anode outlet for said second exhaust gases; and a feedback loop for returning at least a part of the second exhaust gases arriving at the anode outlet back to the anode inlet, said method comprising the step of supplying at least a part of said second exhaust gases continuously or discontinuously to said cathode inlet and discharging them with said first exhaust gases from said fuel cell system, with said residual hydrogen contained in said second exhaust gases being reacted with said oxygen or oxygen containing gas at said cathode side to form water at the catalyst present at said cathode side.

Claim 21

Dependent Claim 70 words

A method in accordance with claim 18 , including the step of controlling the quantity of second exhaust gases supplied to the cathode side by means of a valve, so that on mixing of the second exhaust gases with oxygen or an oxygen containing gas supplied to said cathode side to form a mixture having an ignition limit, the residual hydrogen contained in said mixture lies beneath said ignition limit.

Claim 22

Dependent Claim 52 words

A method in accordance with claim 18 , including the step of supplying additional hydrogen to said anode side when supplying second exhaust gases to said cathode side in order to flush the fuel cells at said anode side with hydrogen and to ensure a higher hydrogen concentration at said anode side.

Claim 23

Dependent Claim 33 words

A method in accordance with claim 18 , including the further step of mixing at least a part of said second exhaust gases with said first exhaust gases downstream of said cathode outlet.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2008-02-01	2008-08-02	2009-02-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2012-02-01	2012-08-02	2013-02-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2016-02-01	2016-08-02	2017-02-01	$7700.00	Window Closed / Lapsed

Fuel cell system and method of operating a fuel cell system

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