CO2 based synergistic reaction effects with energy and exergy (2E) analysis of high density polyethylene with high ash bituminous coal for syngas production

Abstract

A larger accumulation of medical waste is one of the major environmental issues due to the COVID-19 pandemic situation. The segregation and use of waste plastics from medical waste as a source of fuel for syngas production are highly beneficial. In packaging plastics, high density polyethylene (HDPE) occupies 20% of the total waste plastics. Hence, the conversion of HDPE into syngas is essential for waste reduction and energy production. Further, Indian coals possess high ash content (20–40%) and hence they produce a low calorific value gas on gasification. Hence, the co-gasification of these coals with suitable fuels such as HDPE can raise the heating value of syngas. In this context, HDPE is co-gasified with a high ash Indian coal using CO2 as the gasification agent for syngas production. Co-pyrolysis and co-gasification behavior of HDPE with high ash coal (HAC) under CO2 atmosphere are analyzed by using a fixed bed reactor and a thermogravimetric analyzer. Unlike reported in the recent literature, the present study showed that a high quality syngas can be obtained from the co-gasification process (1000 °C) with the heating value of 22 MJ/m3 using CO2 as the gasification agent. The chemical reactivity between CO2 gas, coal volatiles, and ethylene molecules significantly altered the surface morphology of char, which becomes highly porous making suitable for Boudouard reaction. On the surface of char, ester, and acid functional groups are formed. The co-feeding conditions raised the cold gas efficiency by 51% and the specific exergy of syngas by seven times that of HAC.