Towards Carbon Neutrality of Calcium Carbide-Based Acetylene Production: Carbon Footprint Assessment of Replacing Fossil Resources with Sustainable Biomass

Abstract

Acetylene is produced from the reaction between calcium carbide (CaC 2 ) and water, while the production of CaC 2 generates significant amount of carbon dioxide not only because it is an energy-intensive process but also the raw material for CaC 2 synthesis is from coal. Here, a comprehensive biomass-to-acetylene process was constructed that integrated several units including biomass pyrolysis, oxygen-thermal CaC 2 fabrication and calcium looping. For comparison, a coal-to-acetylene process was also established by using coal as feedstock. The carbon efficiency, energy efficiency and environmental impacts of the bio-based calcium carbide acetylene (BCCA) and coal-based calcium carbide acetylene (CCCA) processes were systematically analyzed. Moreover, the environmental impacts were further evaluated by applying thermal integration at system level and energy substitution in CaC 2 furnace. Even though the BCCA process showed lower carbon efficiency and energy efficiency than that of the CCCA process, life cycle assessment demonstrated the BCCA (1.873 kg CO 2 -eq/kg- prod) a lower carbon footprint process which is 0.366 kg CO 2 -eq/kg-prod lower compared to the CCCA process. With sustainable energy (biomass power) substitution in CaC 2 furnace, even lower GWP value of 1.377 kg CO 2 -eq/kg-prod can be achieved in BCCA process with energy substitution. This work performed a systematic analysis on integrating biomass into industrial acetylene production, and revealed the positive role of biomass as raw material (carbon) and energy supplier.

Keywords: Biomass pyrolysis, CO2 mitigation, Calcium carbide, Acetylene, Calcium loop