A fuel cell exhaust processing unit for consuming fuel in the exhaust flow of a main fuel cell module comprising a fuel cell assembly configured to receive the exhaust flow from an anode flow path of the main fuel cell module, the fuel cell assembly electrically connected and configured to consume fuel remaining in the exhaust flow from the main fuel cell module to a predetermined level before the exhaust flow exits the unit.

Systems and methods are provided for integrating a chemical looping combustion system with molten carbonate fuel cells to provide improved operation of the molten carbonate fuel cells when using the exhaust from a gas turbine or other electrical power generation device as the CO.sub.2 source for the MCFC cathodes. This integration can be accomplished by using metal oxide in the chemical looping combustion system to oxidize the anode output flow from the MCFCs. This can reduce or minimize the number of separations that need to be performed in order to process the concentrated CO.sub.2 present within the anode exhaust. By reducing, minimizing, or eliminating the CO and H.sub.2 in the anode exhaust, the need to perform more costly separations (such as cryogenic separation or amine washing) to obtain a high purity CO.sub.2 product stream can be reduced or minimized. Optionally, the cathode exhaust from the molten carbonate fuel cells can be used as an oxygen-containing stream for regeneration of the metal oxide.

A method and system includes operating an air blower at an inlet of the fuel cell stack such that a portion of hydrogen in a combined exhaust of a fuel cell system, in all operating conditions of the fuel cell stack, is less than a predefined threshold.

Systems and methods are provided for capturing CO.sub.2 from a combustion source using molten carbonate fuel cells (MCFCs). At least a portion of the anode exhaust can be recycled for use as a fuel for the combustion source. Optionally, a second portion of the anode exhaust can be recycled for use as part of an anode input stream. This can allow for a reduction in the amount of fuel cell area required for separating CO.sub.2 from the combustion source exhaust and/or modifications in how the fuel cells can be operated.

In various aspects, systems and methods are provided for operating a molten carbonate fuel cell assembly at increased power density. This can be accomplished in part by performing an effective amount of an endothermic reaction within the fuel cell stack in an integrated manner. This can allow for increased power density while still maintaining a desired temperature differential within the fuel cell assembly.

A fuel cell system sets the larger one of a stack request compressor supply flow rate calculated based on a request of a fuel cell stack and a system request compressor supply flow rate calculated based on a request by the fuel cell system as a target compressor supply flow rate and controls a compressor according to the target compressor supply flow rate. The fuel cell system also controls a bypass valve based on a stack supply flow rate and a target stack supply flow rate to be supplied to the fuel cell stack. The fuel cell system fixes the bypass valve or limits the drive of the bypass valve when the system request compressor supply flow rate is set as the target compressor supply flow rate and the stack supply flow rate becomes smaller than the target stack supply flow rate.

A fuel cell system includes a fuel cell, an anode region which is to be fed with hydrogen at an anode inlet of the fuel cell, a cathode region which is to be fed with oxygen via a cathode inlet conduit at a cathode inlet of the fuel cell, a cathode gas conveyor for conveying cathode gas into the cathode inlet conduit, an anode outlet conduit which accepts anode offgas at an anode outlet of the fuel cell, a catalytic converter through which the anode offgas can flow in the anode outlet conduit, a cathode outlet conduit which accepts cathode offgas at a cathode outlet of the fuel cell, and a cathode branch conduit that connects the cathode inlet conduit to the anode outlet conduit upstream of the catalytic converter.

In various aspects, systems and methods are provided for operating a molten carbonate fuel cell assembly at increased power density. This can be accomplished in part by performing an effective amount of an endothermic reaction within the fuel cell stack in an integrated manner. This can allow for increased power density while still maintaining a desired temperature differential within the fuel cell assembly.

In various aspects, systems and methods are provided for integration of molten carbonate fuel cells with a Fischer-Tropsch synthesis process. The molten carbonate fuel cells can be integrated with a Fischer-Tropsch synthesis process in various manners, including providing synthesis gas for use in producing hydrocarbonaceous carbons. Additionally, integration of molten carbonate fuel cells with a Fischer-Tropsch synthesis process can facilitate further processing of vent streams or secondary product streams generated during the synthesis process.

In various aspects, systems and methods are provided for operating molten carbonate fuel cells with processes for iron and/or steel production. The systems and methods can provide process improvements such as increased efficiency, reduction of carbon emissions per ton of product produced, or simplified capture of the carbon emissions as an integrated part of the system. The number of separate processes and the complexity of the overall production system can be reduced while providing flexibility in fuel feed stock and the various chemical, heat, and electrical outputs needed to power the processes.