Patent ID: 8101307

Claim:
A method of operating a fuel cell system, comprising: providing a fuel inlet stream into a fuel cell stack, wherein the fuel cell stack is a solid oxide fuel cell stack; operating the fuel cell stack to generate electricity and a hydrogen containing fuel exhaust stream; lowering a temperature of a fuel exhaust stream to between 120° C. and 200° C. by exchanging heat with the fuel inlet stream and then with an air inlet stream; passing the lower temperature fuel exhaust stream to a splitter; passing a first portion of the lower temperature fuel exhaust stream to a high temperature, low hydration ion exchange membrane cell stack and a second portion of the lower temperature fuel exhaust stream into the fuel inlet stream; separating at least a portion of hydrogen contained in the fuel exhaust stream using the high temperature, low hydration ion exchange membrane cell stack; providing the hydrogen separated from the fuel exhaust stream into the fuel inlet stream; and heating the air inlet stream, which is preheated by the fuel exhaust stream, using heat from an air exhaust stream; wherein an AC electrical efficiency of the system is at least 50% and an effective fuel utilization is at least 94%.