Molten carbonate fuel cells for simultaneous CO2 capture, power generation, and H2 generation

Abstract

This article presents a new technology for the generation of power and steam, or other process heat, with very low CO2 emissions. It is well known that cogeneration of electricity and steam is highly efficient and that amine units can be used to remove CO2 from combustion flue gas, but that the amine unit consumes a significant amount of steam and power, reducing the overall system efficiency. In this report, the use of molten carbonate fuel cells (MCFCs) to capture CO2 from cogen units is investigated and shown to be highly efficient due to the additional power that they produce while capturing the CO2. Furthermore, the MCFCs are capable of reforming methane to hydrogen simultaneous to the power production and CO2 capture. This hydrogen can either be recycled as fuel for consumption by the cogen or MCFCs, or exported to an independent combustion unit as low carbon fuel, thereby decarbonizing that unit as well. The efficiency of MCFCs for CO2 capture is higher than use of amines in all cases studied, often by a substantial margin, while at the same time the MCFCs avoid more CO2 than the amine technology. As one example, the use of amines on a cogeneration unit can avoid 87.6% of CO2 but requires 4.91 MJ/kg of additional primary energy to do so. In contrast, the MCFCs avoid 89.4% of CO2 but require only 1.37 MJ/kg of additional primary energy. The high thermal efficiency and hydrogen export option demonstrate the potential of this technology for widespread deployment in a low carbon energy economy.