Overcoming the energy and environmental issues of LNG plants by using solid oxide fuel cells

Abstract

A new intensification concept was proposed for the liquefied natural gas (LNG) plants. Our concept capitalizes on solid oxide fuel cells (SOFCs) and efficient pressure/heat recovery. Detailed processes were synthesized, simulated and optimized (with and without carbon capture) to demonstrate our concept. These configurations were derived from a superstructure using a new conceptual methodology. Unlike many of the published SOFC systems, our concept and processes are specific to the LNG sector. Another unique aspect of this work is our comprehensive simulation and optimization analyses. We rigorously considered the entire LNG plant to derive tangible conclusions and fill the existing gaps in the literature concerning fuel balance, LNG/helium specification, to name a few. The optimization was challenging due to the high degree of interactions between the units and the enormous numbers of variables, amongst other factors. Therefore, we developed a different optimization strategy that is of a holistic nature, capable of simplifying the analysis and is suitable for other systems. Relative to a base case, our optimum configuration was capable of boosting production by over 4%, with 25% less emissions. As for the processes that capture carbon dioxide, the LNG output could be increased by 2.5%, with over 65% reduced emissions.