Performances and Net CO2 Emission of Light Olefin Production Based on Biomass-to-Methanol and DMTO-II Technologies with CO2 Capture and Sequestration

The rapid development of the coal-to-olefins industry in China provides a way to synthesize ethylene and propylene besides conventional petroleum refinery. However, its serious issues of fossil fuel and water consumption and CO2 emission threaten the sustainability of the natural environment as well as industrial society. This research extended the previous design of biomass gasification-based methanol synthesis to an efficient biomass-to-olefins (BTO) system for saving fossil fuel, reducing CO2 emission, and improving the sustainability of light olefins production. The BTO system was modeled using the ASPEN PLUS software. By incorporating the DMTO-II olefins synthesis as well as the dual-stage entrained flow biomass gasification, the ethylene/propylene yield was increased to 0.24 t/t dry biomass with an exergy efficiency of 58.4% for the system. The carbon uptake credit of biomass feedstock resulted in a negative net CO2 emission of -1.63 t/t olefins for this BTO system with a total cost of 5919 CNY/t olefins (i.e., 870 USD/t). The biomass price had great impact on the economic effectiveness of this BTO. It could only be acceptable when the unit biomass delivered cost was less than 600 CNY/t in consideration of BTO's contribution to environmental benefits. The application of CO2 capture and sequestration to this BTO would further reduce the net CO2 emission and uncover an indirect approach to capture CO2 from the atmosphere. In that, 85% CO2 capture was the most cost-effective choice which led to an additional cost of 135 CNY/t CO2 (i.e., 20 USD/t). Yet, policy-related subsidies for CO2 abatement might offset this cost. In this circumstance, BTO could show great environmental benefits as well as acceptable economic performances.