Fuel cell stack system and operating method

A fuel cell stack comprising:

• at least first and second cells and a separator assembly;
• said cells each comprising:
• an anode;
• a cathode;
• an electrolyte between the anode and the cathode;
• and
• a cell peripheral edge;
• and
• said separator assembly comprising:
• a fluid separator having a fuel side and an oxidant side and a separator peripheral edge;
• an anode spacer element between the fuel side and the anode of the first cell;
• a cathode spacer element between the oxidant side and the cathode of the second cell;
• a cathode exhaust passageway having a catheter exhaust outlet and a catheter exhaust inlet between the oxidant side and the cathode of the second cell;
• and
• an anode feed passageway having a fuel inlet and a generally continuous-loop anode feed tube spaced apart from the cell peripheral edge and located between the fuel side and the anode of the first cell;
• and
• the anode feed tube having a plurality of fuel outlets therealong.

A fuel cell stack comprising:

• at least first and second cells and a separator assembly;
• said cells each comprising:
• an anode comprising an anode central region;
• a cathode comprising a cathode central region;
• an electrolyte between the anode and the cathode;
• and
• a cell peripheral edge;
• and
• said separator assembly comprising:
• a fluid separator having a fuel side and an oxidant side and a separator peripheral edge;
• an anode spacer element, made of a fluid-permeable material, between the fuel side and the anode of the first cell;
• a cathode spacer element, made of a fluid-permeable material, between the oxidant side and the cathode of the second cell;
• a cathode exhaust passageway having an exhaust outlet and an exhaust inlet between the oxidant side and the cathode of the second cell;
• an anode feed passageway having a fuel inlet and a plurality of fuel outlets between the fuel side and the anode of the first cell, the fuel outlets located between the cell peripheral edge and the anode central region;
• and
• an anode recycle passageway having a recycle inlet fluidly coupled to spent fuel, including cell reaction product water, at the anode central region and a recycle outlet fluidly coupled to the anode feed passageway;
• and
• means for causing spent fuel, including cell reaction product water from the anode central region, to flow into the recycle inlet, along the anode recycle passageway, out the recycle outlet and into a flow of fuel passing into the anode feed passageway towards the fuel outlet so the cell reaction product water can be used as a steam source for reforming.

A fuel cell stack comprising:

• at least first and second cells and a separator assembly;
• said cells each comprising:
• an anode comprising an anode central region;
• a cathode comprising a cathode central region;
• an electrolyte between the anode and the cathode;
• and
• a cell peripheral edge;
• said separator assembly comprising:
• a fluid separator having a fuel side and an oxidant side and a separator peripheral edge;
• a porous anode spacer element, having an anode central region and an anode spacer peripheral edge, between the fuel side and the anode of the first cell;
• a porous cathode spacer element, having a cathode central region and a cathode spacer peripheral edge, between the oxidant side and the cathode of the second cell;
• a cathode exhaust passageway having a cathode exhaust outlet and a cathode exhaust inlet at the cathode central region;
• an anode feed passageway comprising a fuel inlet and a generally continuous-loop anode feed tube spaced apart from the cell peripheral edge between the fuel side and the anode of the first cell, said feed tube having inwardly-directed and outwardly-directed fuel outlets so that spent fuel, including residual fuel, moves both inwardly towards the anode central region and outwardly towards the anode spacer peripheral edge to pass through the anode spacer peripheral edge;
• an anode recycle passageway having a recycle inlet fluidly coupled to spent fuel, including cell reaction product water, at the anode central region and a recycle outlet fluidly coupled to the anode feed passageway;
• and
• means for causing spent fuel, including cell reaction product water from the anode central region, to flow into the recycle inlet, along the anode recycle passageway, out the recycle outlet and into a flow of fuel passing into the anode feed passageway towards the fuel outlets so the cell reaction product water can be used as a steam source for reforming;
• and
• an air deflector spaced-apart from and overlying the anode separator element to help prevent generally radially-inwardly moving air from contacting the anode while permitting the generally radially-inwardly moving air access to the cathode spacer peripheral edge.

A method for operating a fuel cell stack comprising:

• accessing a fuel cell stack comprising alternating cells and separator assemblies, each said cell comprising an anode, a cathode and an electrolyte between the anode and the cathode, the anodes each having an anode peripheral edge and an anode central region, the cathodes each having a cathode peripheral edge and a cathode central region, each said separator assembly comprising a fluid separator with a separator peripheral edge;
• flowing an oxygen-containing gas generally radially inwardly to said cathode peripheral edges;
• deflecting said oxygen-containing gas away from the anode peripheral edges;
• and
• feeding a fuel to the anodes to a position spaced-apart from the anode peripheral edge of each said anode.

A method for operating a fuel cell stack comprising:

• accessing a fuel cell stack comprising alternating cells and separator assemblies, each said cell comprising an anode, a cathode and an electrolyte between the anode and the cathode, the anodes each having an anode peripheral edge and an anode central region, the cathodes each having a cathode peripheral edge and a cathode central region, each said separator assembly comprising a fluid separator with a separator peripheral edge;
• flowing an oxygen-containing gas generally radially inwardly to said cathode peripheral edges;
• and
• feeding a fuel between the anode peripheral edge and the anode central region of each said anode by flowing the fuel generally radially inwardly and outwardly using a generally continuous-loop anode feed tube having inwardly-directed and outwardly-directed fuel outlets located spaced-apart from the anode peripheral edge and the anode central region.

A method for operating a fuel cell stack comprising:

• accessing a fuel cell stack comprising alternating cells and separator assemblies, each said cell comprising an anode, a cathode and an electrolyte between the anode and the cathode, the anodes each having an anode peripheral edge and an anode central region, the cathodes each having a cathode peripheral edge and a cathode central region, each said separator assembly comprising a fluid separator with a separator peripheral edge;
• flowing an oxygen-containing gas generally radially inwardly to said cathode peripheral edges;
• feeding a fuel to the anodes to a position between the anode peripheral edge and the anode central region of each said anode using anode feed passageways so that spent fuel, including residual fuel and cell reaction product water, flows radially inwardly and outwardly;
• and
• recycling spent fuel, including cell reaction product water, from the anode central regions using anode recycle passageways, each said anode recycle passageway having a recycle inlet at the anode central region and a recycle outlet, by flowing the spent fuel from the recycle inlets, through the anode recycle passageway and into a flow of fuel passing along the anode feed passageway towards the fuel outlet.

A fuel cell system comprising:

• a fuel cell module comprising:
• a module interior;
• a plurality of the fuel cell assemblies housed within the module interior, each said fuel cell assembly comprising first and second cells and a separator therebetween, said cells each comprising an anode, a cathode and an electrolyte therebetween, the separator comprising:
• a fluid separator having a fuel side and an oxidant side and a separator peripheral edge, an anode spacer element, having an anode spacer peripheral edge, between the fuel side and the anode of the first cell, a cathode spacer element, having a cathode spacer peripheral edge, between the oxidant side and the cathode of the second cell, a cathode exhaust passageway having an exhaust inlet between the oxidant side and the cathode of the second cell, and an anode feed passageway having a fuel outlet between the fuel side and the anode of the first cell spaced-apart from the anode spacer peripheral edge so that spent fuel, including residual fuel, can move outwardly and pass through the anode spacer peripheral edge;
• a cathode exhaust line coupling the cathode exhaust passageway to a flue gas exit exterior of the module enclosure;
• and
• a fuel line fluidly coupled to the anode feed passageway;
• a source of oxygen-containing gas fluidly coupled to the module interior so to supply said housing interior with oxygen-containing gas;
• and
• a source of fuel gas fluidly coupled to the anode feed passageways of the fuel cell assemblies.