Co-gasification of Waste Biomass and Plastic for Syngas Production with CO2 Capture and Utilization: Thermodynamic Investigation

Abstract

Abstract This work presents an integrated plant-wide process for co-gasification of waste biomass and plastics using steam and CO2 to produce an industrially important feed stock i.e., syngas with molar ratio of H2/CO ~ 2. The proposed plant wide process is designed with key feature of carbon capture and utilization (CCU) and made self-sustainable by utilizing a fraction of syngas for meeting the heat, steam and CO2 demands with additional heat recovery and steam generation and power generation sections. Further, steady state plant wide models are developed using ASPEN Plus, and simulations are performed for the co-gasification of high-density polyethylene (HDPE) and rice husk (RH) at varying feed compositions (0-100% HDPE). Further, rigorous sequential parametric sensitivity analysis is performed to determine the optimal process parameters and investigate the impact of feed composition on the product yield. Results revealed that steam to carbon ratio (S/C) should be maintained above 1.2 to attain complete carbon conversion within the gasifier which tends to enhance the overall performance of the integrated scheme. The comparative investigation on co-gasification of HDPE and RH revealed that an increase in weight percentage of HDPE in the feed mixture resulted in increased syngas production and plant efficiency due to the high carbon and low ash content of HDPE. Gasification of pure HDPE waste resulted in the maximum output of 2.2 kg of syngas/kg of feed with a net plant efficiency of 68%, while in the case of pure RH the syngas production and efficiency dropped to 0.60 kg/kg of feed and 35%, respectively.