Molten carbonate fuel cells (MCFCs) are operated at elevated pressure to provide increased operating voltage and/or enhanced CO.sub.2 utilization with a cathode input stream having a low CO.sub.2 content. It has been discovered that increasing the operating pressure of a molten carbonate fuel cell when using a low CO.sub.2-content cathode input stream can provide unexpectedly large increases in operating voltage while also reducing or minimizing the amount of alternative ion transport and/or enhancing CO.sub.2 utilization.

Systems and methods are provided for arranging processing units in a common volume to allow for processing of a fluid flow as part of a mass and/or heat transfer process. Fuel cells are examples of processing units that include separate flow paths for processing two input fluid flows with mass and/or heat transfer between the separate flow paths. The arrangements described herein can allow a gas phase fluid flow to be delivered to a first process flow path of processing units in a common volume. The gas phase fluid flow can be delivered in a relatively uniform manner without the use of an intervening manifold to distribute gas from the common volume into the processing units.

Embodiments of methods for capturing high-purity CO.sub.2 in a hydrocarbon facility and related systems are provided. The method comprises operating a hydrogen plant to generate a high-purity hydrogen stream and a CO.sub.2 rich stream with a CO.sub.2 concentration above 30%; introducing the high-purity hydrogen stream into an anode of a molten carbonate fuel cell; introducing the CO.sub.2 rich stream and O.sub.2 into a cathode of the molten carbonate fuel cell; reacting CO.sub.2 and O.sub.2 within the cathode to produce carbonate and a cathode exhaust stream from a cathode outlet; reacting carbonate from the cathode with H.sub.2 within the anode to produce electricity and an anode exhaust stream from an anode outlet, the anode exhaust stream comprising CO.sub.2 and H.sub.2O; separating the CO.sub.2 in the anode exhaust stream in one or more separators to form a pure CO.sub.2 stream and a H.sub.2O stream; and collecting the pure CO.sub.2 stream.

Provided is a carbon dioxide electrolysis-carbon deposition/carbon fuel cell-integrated apparatus which enable interconversion between electric energy and chemical energy (electrodeposited carbon) through the use of an integrated electrochemical reaction system with a molten salt.

An anode of a fuel cell has an anoe current collector defining an inlet configured to receive fuel gas and an outlet configured to output the fuel gas, a barrier that divides an active area of the anode current collector into a first area and a second area, and a flow passage configured to allow a flow of fuel gas from the inlet through the first area and the second area to the outlet. An obstacle is located in the flow passage in an inactive area of the anode current collector and is configured to change a flow direction of the fuel gas in the flow passage from the first area to the second area to achieve intra-cell mixing of the fuel gas.

In various aspects, systems and methods are provided for integrating molten carbonate fuel cells with a fired heater for production of electrical power while also reducing or minimizing the amount of CO.sub.2 present in the flue gas generated by the fired heater. The molten carbonate fuel cells can be integrated for use with fired heater so that at least a portion of the flue gas from fired heater flows through cathodes of the fuel cells and at least a portion of the cathode exhaust is returned to a convection section of the fired heater.

A carbon dioxide capture system includes a fuel cell assembly comprising an anode section and a cathode section; an electrochemical hydrogen separator (EHS) configured to receive an anode exhaust stream from the anode section of the fuel cell assembly, and generate a first EHS output stream comprising hydrogen, and a second EHS output stream comprising concentrated carbon dioxide; and a liquid-vapor separator (LVS) configured to receive the second EHS output stream, and separate the second EHS output stream into a first LVS output stream comprising liquid carbon dioxide, and a second LVS output stream comprising non-condensable gases in the second EHS output stream and carbon dioxide vapor.

Molten carbonate fuel cells (MCFCs) are operated to provide enhanced CO.sub.2 utilization. This can increase the effective amount of carbonate ion transport that is achieved. The enhanced CO.sub.2 utilization is enabled in part by operating an MCFC under conditions that cause transport of alternative ions across the electrolyte. The amount of alternative ion transport that occurs during enhanced CO.sub.2 utilization can be mitigated by using a more acidic electrolyte.

An elevated target amount of electrolyte is used to initially fill a molten carbonate fuel cell that is operated under carbon capture conditions. The increased target electrolyte fill level can be achieved in part by adding additional electrolyte to the cathode collector prior to start of operation. The increased target electrolyte fill level can provide improved fuel cell performance and lifetime when operating a molten carbonate fuel cell at high current density with a low-CO.sub.2 content cathode input stream and/or when operating a molten carbonate fuel cell at high CO.sub.2 utilization.

A fuel cell system includes a fuel cell stack having a plurality of fuel cells that each contain a plurality of fuel electrodes and air electrodes. The system includes a fuel receiving unit connected to the fuel cell stack, which receives a hydrocarbon fuel from a fuel supply. The system includes a fuel exhaust processing unit fluidly coupled to the fuel cell stack by a slip stream, where the fuel exhaust processing unit processes fuel exhaust from the fuel cell stack, and the slip stream is fluidly connected to an exhaust stream flowing from the fuel cell stack. The fuel processing unit removes a first portion of carbon dioxide (CO.sub.2) from fuel exhaust within the slip stream, outputs the first portion of CO.sub.2 in a first stream, and outputs a second portion of CO.sub.2 remaining from the fuel exhaust in the slip stream into a second stream, which includes hydrogen.