Bio-methanol with negative CO2 emissions from residual forestry biomass gasification: Modelling and techno-economic assessment of different process configurations

Abstract

The paper presents a techno-economic comparison among five alternative process configurations for bio-methanol production from the gasification of residual forestry biomass. Process design and simulations are performed in Aspen Plus for mass and energy balance calculation, followed by preliminary sizing and economic analysis. Process schemes include a gasification island (state-of-the-art low-pressure gasification compared against a high-pressure gasifier) with syngas conditioning and compression, heat recovery, syngas composition adjustment (by CO2 capture or addition of hydrogen produced by electrolysis), methanol synthesis and purification and a heat recovery cycle for power generation. CO2 capture is performed with conventional chemical absorption in the benchmark cases, while low-temperature partial condensation of CO2 is modeled in the advanced scenario. Methanol output is 14–15 kt/y in the CO2 capture cases and 36 kt/y in the H2 addition option.Configurations with a pressurized gasifier and phase-change-based CO2 separation are the most efficient ones, with a primary energy efficiency of 50 % and a Levelized Cost of Methanol (LCOM) of 700 €/tMeOH. In comparison, LCOM increases to 730 €/tMeOH in the case with conventional capture or between 792 €/tMeOH and 831 €/tMeOH (depending on the CCS technology) if the gasification pressure is conservatively reduced to 2.5 bar. In the H2 addition scenario, LCOM increases to 821 €/tMeOH due to the significant impact of the electricity consumption for H2 production, (only partly compensated by the increased methanol production). Scenarios with CO2 capture feature negative CO2 emissions, in the range −1.64 to −1.84 tCO2eq/tMeOH, as a result of the capture and storage of biogenic CO2 (BECCS approach).