Application of MCFC in Coal Gasification Plants for High Efficiency CO2 Capture

Abstract

Integrated gasification combined cycles (IGCCs) are considered the reference technology for high efficiency and low emission power generation from coal. In recent years, several theoretical and experimental studies in this field have been oriented toward capturing CO2 from IGCCs through the integration of solid oxide fuel cells (SOFCs) for coal-syngas oxidation, investigating the so-called integrated gasification fuel cell cycles (IGFC). However, molten carbonate fuel cells (MCFCs) can also be a promising technology in IGFCs. After rather comprehensive research carried out by the authors on modeling and simulation of SOFC-based IGFC plants, an interesting IGFC cycle based on MCFC is assessed in this work, where plant layout is designed to exploit the capability of MCFCs of transferring CO2 and O2 from the oxidant side to the fuel side. Syngas produced in a high efficiency Shell gasifier is cleaned and mainly burned in a combustion turbine as in conventional IGCCs. Turbine flue gas, rich with oxygen and carbon dioxide, are then used as oxidant stream for the fuel cell at the cathode side, while the remaining clean syngas is oxidized at the anode side. In this way, the MCFC, while efficiently producing electricity, separates CO2 from the gas turbine flue gas as in a post-combustion configuration; oxygen is also transported toward the anode side, oxidizing the remaining syngas as in an oxy-combustion mode. A CO2-rich stream is hence obtained at anode outlet, which can be cooled and compressed for long term storage. This configuration allows production of power from coal with high efficiency and low emission. In addition, as already highlighted in a previous study where a similar concept has been applied to natural gas-fired combined cycles, a limited fraction of the power output is generated by the fuel cell (the most expensive component), highlighting its potential also from an economic point of view. Detailed results are presented in terms of energy and material balances of the proposed cycle.