Non-isothermal gasification of biomass char and coal char mixture in CO2 condition

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ABSTRACT Non-isothermal thermogravimetry method was used in the paper to investigate the gasification properties of biomass char (BC), coal char (CC), and their blended char at different mass ratios of 1:3, 1:1,3:1 under CO2. The results showed that with the increase of heating rate, the gasification curve moved to high-temperature zone and the peak rate of gasification increased, the gasification reactivity improved, and the gasification time reduced from 26.8 min to 6.78 min. Increasing BC share, the gasification rate also increased and the gasification time was shortened as the high specific surface area of BC had a great influence on gasification reactivity. The volumetric model (VM), the shrinking core model (SCM), and the random pore model (RPM) were applied to describe the reaction behavior of the chars and the results showed that all three models could describe the gasification process of char, while among them, RPM model achieved the best-fitting result. By RPM model, the activation energy of BC/CC at mass ratios of 0:4,1:3,1:1,3:1,4:0 was obtained, which were 240.74 kJ/mol, 129.16 kJ/mol, 108.54 kJ/mol,102.53 kJ/mol, and 97.01 kJ/mol, respectively. The decrease in activation energy with the increase of biomass char content could be ascribed to the higher specific surface area of BC and the lower carbon structure uniformity of BC.