Effects of carbon capture on the performance of an advanced coal-based integrated gasification fuel cell system

Integrated gasification fuel cell (IGFC) power plants combining gasification and solid oxide fuel cell (SOFC) technologies are very promising for highly efficient and environmentally friendly power generation from coal. IGFC plant amenability to carbon capture for sequestration makes the technology more attractive given the increasing concern over global climate change caused by greenhouse gas emissions. With the support of the US Department of Energy and the National Energy Technology Laboratory, the Advanced Power and Energy Program has conducted a study to identify promising conceptual designs for IGFC plants. The most promising IGFC concept identified so far is a system with catalytic hydro-gasification, a pressurized (operating pressure of 10 bar) SOFC followed by a turbo-expander and a steam cycle. The design requirement for recycling de-carbonized anode exhaust back to the gasifier for hydro-gasification not only produces a synergistic integration of SOFC and gasification subsystems, but also makes carbon separation a natural result. The current analyses of this system show an efficiency of 58.4 per cent (coal higher heating value basis) while capturing 94 per cent of the CO2. Using this system as a baseline case, this work investigates the sensitivity of IGFC system performance on the extent of carbon capture. It is shown that the proposed IGFC system can achieve ultra-high carbon capture (> 99 per cent) at small system efficiency expense while reducing carbon capture to below 90 per cent actually diminishes the system efficiency because less fuel is converted in the SOFC.