CO2 utilization for gasification of carbonaceous feedstocks: A thermodynamic analysis

A thermodynamic analysis of gasification of carbonaceous feedstocks using carbon dioxide and a mixture of carbon dioxide with steam or oxygen is carried out using Gibbs minimization approach. Simulations are carried out to study the effect of different operating conditions on the gasifier performance using Aspen Plus. Gasification using CO2 at ambient conditions is not favorable under adiabatic condition. Complete carbon conversion can be obtained by increasing the operating temperature or flowrate of carbon dioxide. A cold gas efficiency greater than 1 is obtained under certain operating conditions. Maximum carbon dioxide conversion is obtained at the carbon boundary point. Based on the minimum energy requirement for complete carbon conversion, a universal optimal operating temperature of 850 °C has been identified for gasification of any feedstock. Biomass requires less heat input compared to coal. Use of steam or oxygen as a cogasifying agent reduces the carbon dioxide and energy requirement but reduces carbon dioxide conversion. Syngas with a wide ranging ratio of hydrogen/carbon monoxide can be obtained using carbon dioxide gasification. Trends of simulation predictions are qualitatively consistent with experimental observations.

► CO2 can be reused by gasifying carbonaceous feedstocks.
► Optimal operating temperature for CO2 gasification is 850 °C.
► Biomass is best feedstock for CO2 reuse with least energy requirement.
► Use of steam or oxygen with CO2 reduces energy requirement.
► Syngas of wide ranging H2/CO ratio can be obtained.