Procedure for starting up a fuel cell system having an anode exhaust recycle loop
First Claim
1. A procedure for starting-up a fuel cell system that is shut down, the shut down system comprising a source of hydrogen containing fuel, a fuel cell including a cathode flow field adjacent the cathode of the cell on one side of the cell electrolyte and an anode flow field adjacent the anode of the cell on the other side of the cell electrolyte, an anode recycle loop for recirculating at least a portion of the anode flow field exhaust through the anode flow field, wherein both the anode flow field and cathode flow field are filled with air, and the primary electricity using device is disconnected from the fuel cell external circuit, the start-up procedure comprising the steps of:
- (A) initiating a recirculation, through the recycle loop, of the anode flow field exhaust, which is initially 100% air, and then providing a limited flow of hydrogen containing fuel into the recirculating anode exhaust to create a mixture of hydrogen and air within the recycle loop;
(B) catalytically reacting hydrogen and oxygen within the mixture on a catalyst within the recycle loop as the hydrogen and oxygen circulates through the recycle loop in contact with a catalyst to form water, and continuing to add hydrogen containing fuel to the recirculating mixture until substantially no oxygen remains in the recycle loop, including regulating the rate at which fuel is added such that the recirculating gases do not contain a flammable ratio of hydrogen and oxygen when they contact the catalyst or when the enter the anode flow field; and
, (C) after substantially no oxygen remains in the recycle loop, (i) increasing the rate of fuel flow into the anode flow field to a normal operating flow rate, (ii) providing an oxidant into the cathode flow field at a normal operating flow rate, and, (iii) connecting the primary electricity using device to the external circuit.
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Accused Products
Abstract
A procedure for starting up a fuel cell system that is disconnected from its primary load and that has air in both its cathode and anode flow fields includes a) connecting an auxiliary resistive load across the cell to reduce the cell voltage; b) initiating a recirculation of the anode flow field exhaust through a recycle loop and providing a limited flow of hydrogen fuel into that recirculating exhaust; c) catalytically reacting the added fuel with oxygen present in the recirculating gases until substantially no oxygen remains within the recycle loop; disconnecting the auxiliary load; and then d) providing normal operating flow rates of fuel and air into respective anode and cathode flow fields and connecting the primary load across the cell. The catalytic reaction may take place on the anode or within a catalytic burner disposed within the recycle loop. The procedure allows start-up of the fuel cell system without the use of an inert gas purge while minimizing dissolution of the catalyst and corrosion of the catalyst support during the start-up process.
76 Citations
26 Claims
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1. A procedure for starting-up a fuel cell system that is shut down, the shut down system comprising a source of hydrogen containing fuel, a fuel cell including a cathode flow field adjacent the cathode of the cell on one side of the cell electrolyte and an anode flow field adjacent the anode of the cell on the other side of the cell electrolyte, an anode recycle loop for recirculating at least a portion of the anode flow field exhaust through the anode flow field, wherein both the anode flow field and cathode flow field are filled with air, and the primary electricity using device is disconnected from the fuel cell external circuit, the start-up procedure comprising the steps of:
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(A) initiating a recirculation, through the recycle loop, of the anode flow field exhaust, which is initially 100% air, and then providing a limited flow of hydrogen containing fuel into the recirculating anode exhaust to create a mixture of hydrogen and air within the recycle loop;
(B) catalytically reacting hydrogen and oxygen within the mixture on a catalyst within the recycle loop as the hydrogen and oxygen circulates through the recycle loop in contact with a catalyst to form water, and continuing to add hydrogen containing fuel to the recirculating mixture until substantially no oxygen remains in the recycle loop, including regulating the rate at which fuel is added such that the recirculating gases do not contain a flammable ratio of hydrogen and oxygen when they contact the catalyst or when the enter the anode flow field; and
,(C) after substantially no oxygen remains in the recycle loop, (i) increasing the rate of fuel flow into the anode flow field to a normal operating flow rate, (ii) providing an oxidant into the cathode flow field at a normal operating flow rate, and, (iii) connecting the primary electricity using device to the external circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 23, 24, 25, 26)
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20. A procedure for starting-up a fuel cell system that is shut down, the shut down system comprising a hydrogen containing fuel source, a fuel cell including a cathode flow field filled with air adjacent the cathode of the cell on one side of the cell electrolyte and an anode flow field filled with air adjacent the anode of the cell on the other side of the cell electrolyte, and an anode recycle loop for recirculating anode flow field exhaust through the anode flow field, the recycle loop including one or more burners, wherein during shut-down the primary electricity using device is disconnected from the fuel cell external circuit, the start-up procedure comprising the steps of:
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(A) connecting an auxiliary resistive load across the cell;
(B) initiating a recirculation of anode flow field exhaust through the recycle loop, including through the burners;
(C) providing a controlled flow of hydrogen containing fuel into the burners and consuming, in each burner, (i) at least some of the oxygen in the anode exhaust and (ii) at least some of the fuel provided to the burners; and
(D) continuing the controlled flow of fuel into the burners and the recirculation of the anode flow field exhaust through the burners at least until there is substantially no oxygen remaining in the anode exhaust, and, thereafter, (i) providing a fuel flow to the anode flow field and air flow to the cathode flow field at normal operating flow rates, and (ii) connecting the primary electricity using device to the external circuit, wherein the auxiliary load remains connected at least until there is substantially no oxygen remaining in the anode exhaust to limit the cell voltage during the start-up process. - View Dependent Claims (22)
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Specification