Enhanced accessibility of carbon in pyrolysis of brown coal using carbon dioxide

Abstract

This work investigates the effect of CO2 in pyrolysis of brown coal (also referred to as lignite). CO2 changes the distribution of pyrolytic products of brown coal. More CO is generated for the pyrolysis of brown coal in CO2 than that in N-2. Differential scanning calorimeter (DSC) experiments show that the pyrolysis of brown coal in CO2 is more exothermic than that in N-2. This may indicate that the enhanced generation of CO is attributed to an enhanced thermal cracking induced by CO2. The more generation of CO for the reaction in CO2 (4.2 mol.% at 700 degrees C) than in N-2 (0.5 mol.% at 700 degrees C) is a result of shifting carbon distribution from condensable hydrocarbons (e.g., tar) to CO. In addition, more CO is generated from the pyrolysis of brown coal in CO2 than pyrolysis of sub-bituminous coal. This study signifies that low-rank coal can be effectively used as an energy source when CO2 is employed during pyrolysis process.