Kinetic analysis of coal and biomass co-gasification with carbon dioxide

Based on Thermogravimetric Analysis (TGA) experimental data, a kinetic analysis of the Boudouard reaction was studied for three different coal chars, three different biomass chars, and their mixtures. The coal chars included: North Dakota Lignite, Illinois No.6, and Powder River Basin char; the biomass chars included: Hardwood, Switchgrass, and Corn Stove char. The reaction temperature ranged from 900°C to 1100°C. Different kinetic models were used for modeling the reaction rate. For the simplified Dutta and Wen model, it was found that the reaction rate was first order with respect to both CO2 and carbon. For the modified shrinking sphere model, the reaction rate was first order with respect to CO2 but 2/3 order with respect to carbon. For simplicity, none of the models incorporated physical characteristics such as porosity or surface area. Statistical analysis showed the shrinking sphere model provided the best fit for most of gasification rates. Kinetic parameters, such as the apparent rate constant k app, and apparent activation energy Eapp, were derived from the simplified model and shrinking sphere model. The values of the apparent activation energy were comparable for the two models and to those from earlier studies.;A positive synergistic effect on the gasification reaction rate was observed between some coal char and biomass char pairs. These char pairs included: Illinois No.6 mixed with Switchgrass, Illinois No.6 mixed with Hardwood, and Powder River Basin mixed with Corn Stover. Based on Inductively Coupled Plasma -- Mass Spectrometry (ICPMS) analysis and predictive modeling of the apparent activation energy, the amount of Alkali and Alkaline Earth metals bound in the biomass chars was found to cause the positive synergistic effect and the enhanced gasification rate of the coal char