Assessment of bio-methanol and electricity co-production via the integration of biomass-to-methanol process, solid oxide electrolyzer, and power generator

Abstract

The performance assessment of an integrated biomass to methanol and solid oxide electrolyzer with and without a power generation unit (BtM-SOEC-PG and BtM-SOEC), utilizing purge gas from BtM for production of bio-methanol and electricity, is performed. For BtM-SOEC-PG, two utilization routes of low pressure (LP) steam leaving the power generation system (case 1: LP steam is exported to external users (BtM-SOEC-PG-LPEX) and case 2: LP steam is utilized in the process (BtM-SOEC-PG-LPUT)) are examined to determine the impact on process performance of recycling purge gas from BtM to either the methanol reactor or the power generation unit. In all cases, the bio-methanol production increases with increased purge gas recycling, whereas the power generation decreases. The direct CO2 emissions are also improved with increased recycling. Two BtM-SOEC-PG cases are an exothermic process, and the degree of exothermicity increased with purge gas recycling. However, the BtM-SOEC-PG-LPUT with 90 % purge gas recycling offers a maximum methanol production rate of 15.99 kg/h, and under these conditions, 3.17 kW of electricity is generated and 56.18 % energy efficiency is obtained. The energy efficiency of the BtM-SOEC-PG-LPUT, with 90 % purge gas recycling, could potentially be enhanced by 10.42 % due to pinch analysis and heat exchanger network (HEN) design. Exergy analysis indicates that the gasifier is the primary unit of exergy destruction, followed by the combustion unit and the autothermal reformer (ATR) in the second and third positions, respectively. Furthermore, the BtM-SOEC-PG-LPUT with 90 % purge gas recycling offers a competitive cost of bio-methanol (824.37 USD/ton) compared to BtM-SOEC.