Solid-oxide fuel cell systems

Abstract

The present application provides combined cycle fuel cell systems that include a fuel cell, such as a solid-oxide fuel cell (SOFC), comprising an anode that generates a tail gas and a cathode that generates cathode exhaust. The system or plant may include adding fuel, such as processed or refined tail gas, to the inlet air stream of a reformer to heat the reformer. The system or plant may include removing water from the tail gas and recycling the removed water into an inlet fuel stream. The inlet air stream may be the cathode exhaust stream of the fuel cell, and the inlet fuel stream may be input hydrocarbon fuel that is directed to the reformer to produce hydrogen-rich reformate. The system or plant may direct some of the processed or refined tail gas to a bottoming cycle.

1 .- 15 . (canceled) 
     
     
         16 . A combined cycle fuel cell system comprising:
 a solid-oxide fuel cell comprising an a cathode configured to generate a cathode exhaust, and an anode configured to generate a tail gas;   a reforming system configured to convert at least a portion of a mixture of input hydrocarbon fuel and input steam into a hydrogen-rich reformate, and to output the hydrogen-rich reformate to the anode of the fuel cell; and a bottoming cycle,   wherein the tail gas is prevented from being input into the anode and cathode of the fuel cell,   wherein a first portion of the tail gas is directed to the bottoming cycle to drive the bottoming cycle, and   wherein the reforming system is heated to facilitate conversion of the input hydrocarbon fuel and the input steam into the hydrogen-rich reformate by directing through the reforming system at least a portion of heated cathode exhaust that is formed by combusting a second portion of the tail gas in the cathode exhaust.   
     
     
         17 . The system of  claim 16 , wherein a portion of the cathode exhaust is mixed with at least one of the input hydrocarbon fuel and the hydrogen-rich reformate upstream of the fuel cell. 
     
     
         18 . The system of  claim 16 , wherein the system includes a water separator configured to remove water from the cathode exhaust, the water removed from the cathode exhaust being directed to the reforming system as steam to form at least a portion of the input steam. 
     
     
         19 . The system of  claim 16 , wherein the solid-oxide fuel cell receives input air, and wherein the heated cathode exhaust output from the reforming system is used to heat the input air via a heat exchanger. 
     
     
         20 . The system of  claim 16 , wherein the bottoming cycle comprises a combustion engine and the first portion of the residual tail gas drives the combustion engine. 
     
     
         21 . A combined cycle fuel cell system comprising:
 a solid-oxide fuel cell comprising an a cathode configured to generate a cathode exhaust, and an anode configured to generate a tail gas;   a reforming system configured to convert at least a portion of a mixture of input hydrocarbon fuel and input steam into a hydrogen-rich reformate, and to output the hydrogen-rich reformate to the anode of the fuel cell; and a bottoming cycle,   wherein the tail gas is prevented from being input into the anode and cathode of the fuel cell,   wherein a first portion of the tail gas is directed to the bottoming cycle to drive the bottoming cycle,   wherein the reforming system is heated to facilitate conversion of the input hydrocarbon fuel and the input steam into the hydrogen-rich reformate by directing through the reforming system at least a portion of heated cathode exhaust that is formed by combusting a second portion of the tail gas in the cathode exhaust, and   wherein the system includes a boiler configured to receive water removed from the tail gas by a water separator and produce the input stream, at least a portion of a cathode exhaust stream output by the reforming system is directed to the boiler to heat the water removed from the tail gas by the water separator to produce the input steam, and at least a portion of the cathode exhaust system output by the reforming system and directed to the boiler passes through multiple heat exchangers positioned upstream of the boiler.   
     
     
         22 . The system of  claim 21 , wherein a portion of the cathode exhaust is mixed with at least one of the input hydrocarbon fuel and the hydrogen-rich reformate upstream of the fuel cell. 
     
     
         23 . The system of  claim 21 , wherein the system includes a water separator configured to remove water from the cathode exhaust, the water removed from the cathode exhaust being directed to the reforming system as steam to form at least a portion of the input steam. 
     
     
         24 . The system of  claim 21 , wherein the solid-oxide fuel cell receives input air, and wherein the heated cathode exhaust output from the reforming system is used to heat the input air via a heat exchanger. 
     
     
         25 . The system of  claim 21 , wherein the bottoming cycle comprises a combustion engine and the first portion of the residual tail gas drives the combustion engine.