Techno-Economic Assessment of Char Separation in a Solar-Driven Gasifier for Hydrogen Production

We reported the techno-economic performance of various biochar-related configurations of a solar hybridized dual-fluidized-bed (SDFB) gasifier for coproducing hydrogen and biochar. Our study examined the impact of a char–sand separation unit on process performance using steam segregation at high temperatures. We assessed variations in the superficial steam velocity for the segregation process, biochar separation efficiency/purity content, and char conversion on CO2 emissions and solar share. With a biochar separator installed, the solar heat demand increased by 0.62–2.70 MJ per kg of dry, ash-free agro-waste biomass input across the assessed parametric variations. At a solar multiple of 3, the case with the biochar separator reduced annual CO2 emissions by up to 13% compared to the case without a separator. The biochar selling price necessary to make the installation of the char–sand separator in the SDFB gasifier economically competitive relative to its nonsolar or no-separator counterpart has been identified. A sensitivity analysis of biochar selling price and biomass cost was also presented to understand the value proposition of using separated biochar or biomass as an SDFB combustor fuel. The hydrogen break-even costs for the proposed SDFB gasifier were projected to range between 2.9 and 4 USD/kg at a 150 MWth input scale.