Compact air preheater for solid oxide fuel cell systems
View Patent ↗The present invention provides, among other things, a method of operating a solid oxide fuel cell system including a fuel cell stack. The method can include the acts of combining an exhaust flow from an anode side of the fuel cell stack and an exhaust flow from a cathode side of the fuel cell stack, transferring heat from the combined exhaust flow to a first air flow, and combining a second air flow and the heated first air flow upstream from the fuel cell stack to control a temperature of the combined air flow entering the cathode side of the solid oxide fuel cell.
1. A method of operating a solid oxide fuel cell system including a fuel cell stack, the method comprising the acts of:
combining an anode exhaust flow from an anode side of the fuel cell stack and a cathode exhaust flow from a cathode side of the fuel cell stack to form a combined exhaust flow;
oxidizing the anode exhaust flow from the anode side of the fuel cell stack prior to combining the anode exhaust flow and the cathode exhaust flow;
transferring heat from the combined exhaust flow to a first air flow; and
combining a second air flow and the heated first air flow upstream from the fuel cell stack to control a temperature of the combined air flow entering the cathode side of the solid oxide fuel cell.
2. The method of claim 1 , wherein the anode exhaust flow and the cathode exhaust flow are combined in a mixing chamber in a heat exchanger configured to transfer heat from the combined exhaust flow to the first air flow.
3. The method of claim 2 , wherein the mixing chamber is adjacent to an exhaust inlet of the heat exchanger.
4. The method of claim 1 , wherein transferring the heat from the combined exhaust flow to the first air flow includes directing the combined exhaust flow and the first air flow through a heat exchanger, and further comprising directing the anode exhaust flow from the anode side of the fuel cell stack into the heat exchanger through a first inlet of the heat exchanger and directing the cathode exhaust flow from the cathode side of the fuel cell stack into the heat exchanger through a second inlet of the heat exchanger.
5. The method of claim 1 , further comprising separating the first and second air flows and bypassing a heat exchanger with the second air flow, the heat being transferred from the combined exhaust flow to the first air flow in the heat exchanger.
6. The method of claim 1 , wherein transferring the heat from the combined exhaust flow to the first air flow includes directing one of the combined exhaust flow and the first air flow through a first tube and directing an other of the combined exhaust flow and the first air flow through a second tube supported in the first tube.
7. The method of claim 1 , wherein transferring the heat from the combined exhaust flow to the first air flow includes directing the combined exhaust flow and the first air flow in counter flow directions through a heat exchanger.
8. The method of claim 1 , wherein the heat from the combined exhaust flow is transferred to the first air flow in a heat exchanger, and wherein the second air flow is combined with the first air flow downstream from the heat exchanger.