Allam Cycle Fired with Biomass: Process Design, Performance Simulation, and Cost Assessment

Abstract

As the global temperature continues to rise and environmental concerns worsen, cleaner and more sustainable energy is a pressing need worldwide. Power generated from oxy-fuel combustion processes like the Allam Cycle can reduce harmful greenhouse gas emissions and make carbon dioxide (CO2) sequestration more feasible. The Allam Cycle, a novel power generation system developed by NET Power and currently being tested at a demonstration plant in Texas, burns natural gas and uses supercritical CO2 as the working fluid within a Brayton thermodynamic cycle. The technology enables sequestering of all of the CO2 generated, meaning it has zero atmospheric emissions. Using biomass, a renewable energy source, in place of natural gas to fuel the Allam Cycle would make the power generation plant even more environmentally-friendly and potentially carbon-negative, qualifying it as a bio-energy with carbon capture and storage (BECCS) technology. Such technologies will be necessary in coming years to counteract climate change caused by greenhouse gas emissions. In this work, gasification of corn stover for syngas production integrated with an Allam Cycle power plant is designed and simulated in Aspen Plus. The simulated gasification using a bubbling fluidized-bed pressurized gasifier had a cold gas efficiency of 78%. The performance of the overall plant on a 65.5 MWth (biomass feed, LHV basis) scale was evaluated and found to have a net efficiency of 31%. The economics of a biomass-fired Allam Cycle plant were considered, and an LCOE of $233/MWh was found. The LCOE of the biomass-fired Allam Cycle was compared to that of a natural gas fired Allam Cycle plant; in the presence of an economy-wide CO2 price of $103/tonne CO2, the LCOEs of the two technologies would be the same.