Char characteristics of municipal solid waste prepared under N2 and CO2 atmospheres

The texture characteristics of municipal solid waste (MSW) during pyrolysis under N2 and CO2 atmospheres were investigated by N2 adsorption isotherms at −196 °C. With the increment of the pyrolysis temperature, the specific surface area (SBET), micropore area (Smicro) and micropore volume (Vmicro) first increased and then decreased. Thus, moderate temperature favored the MSW porosity development under both atmospheres. The SBET of CO2 char reached the maximum earlier with a greater value (117.3 m2/g at 550 °C), while SBET of N2 char was lower with the maximum of 101.0 m2/g at 600 °C. The influence of atmosphere on char characteristics varied with the pyrolysis temperature. Replacement of N2 by CO2 improved MSW char characteristics in the temperature range of 500–700 °C but hindered porosity at 800 °C. The diversity in hysteresis loops, pore surface area, pore volume and pore size distribution curve between MSW chars under two atmospheres at 800 °C was rather large, because the porosity of CO2 chars degraded by gasification. This work contributes to the understanding of MSW pyrolysis and development of MSW oxy-fuel combustion.