Characterization of Char Gasification in a Micro Fluidized Bed Reaction Analyzer

Abstract

This study is devoted to characterizing the isothermal reaction kinetics of char gasification with CO2 in a micro fluidized bed reaction analyzer (MFBRA) in comparison to the measurement in a thermogravimetric analyzer (TGA). Under minimized inhibition of heat and mass transfer, the reaction rate was found to be much higher in the MFBRA than in the TGA. The maximal rate appeared at a conversion of about 0.15 in the MFBRA but at 0.45 in the TGA. The shrinking core model described well the char-CO2 gasification reaction in both the MFBRA and TGA. In the temperature range of 760-1000 degrees C, the char-CO2 gasification reaction can be divided into two stages. At lower temperatures, the activation energy from the MFBRA and TGA is very close, validating the reliability of the MFBRA for analyzing gas-solid reaction kinetics. At higher temperatures, the estimated activation energy was obviously higher for the MFBRA than for the TGA, showing the lower diffusion limitation prevailing in the MFBRA. The frequency factor for the Arrhenius equation was found to be much higher for the MFBRA than for the TGA, complying with the higher reaction rate observed in the MFBRA. The variation in the reaction atmosphere composition during gas switching in the TGA was also investigated.