CO₂ Gasification Kinetics of Algal and Woody Char Procured under Different Pyrolysis Conditions and Heating Rates

This paper presents the results on gasification kinetic data, influence of the different models on predicted gasification rates, reaction order and comparison of gasification reactivity of the chars prepared in different conditions as well as that among the feedstock (algal and woody chars). A fresh water alga, Chlorococcum humicola and three types of woody biomass were pyrolyzed separately in a thermogravimetric analyzer (TGA) and in an entrained flow reactor (EFR), and the resultant chars were then gasified in the temperature range 700–1000 °C under CO₂ to compare their intrinsic kinetics and to determine the transition temperatures between kinetic control and intraparticle diffusion control. The transition temperature was dependent on both sample and pyrolysis condition. Activation energy and frequency factor were determined using three kinetic models (volumetric, grain and random pore). The activation energy of different chars was determined to be in the range of 180–307 kJ/mol. Among the models, the random pore model was found to be predicting the weight loss profile most accurately except for the algal and a woody char from EFR. The reaction order and reactivity were found to be varying significantly with the pyrolysis condition of the chars