Evaluation of Biomass Char Combustion Kinetics Using a Micro-Fluidized Bed with Thermogravimetry–Mass Spectrometry

Abstract

Assessing the kinetics of biomass char combustion in the fluidized state is crucial for facilitating the thermochemical utilization of biomass energy. In this study, a micro-fluidized bed integrated with thermogravimetry−mass spectrometry (denoted as MFB-TG-MS) was developed to evaluate the combustion kinetics of biomass char in the fluidized state. The constructed device enabled intense heat and mass transfer owing to the fluidization of the bed materials and biomass char samples. On-line sample weight signals and the concentration of tail gas (including O 2 , CO 2 , and CO) were obtained simultaneously in the fluidized state during the experiments. Experimental results indicated that the combustion kinetics of biomass char measured using the MFB-TG-MS system was significantly faster than that determined using a regular TG analyzer. Effects of sample sizes and bed temperatures on char combustion were analyzed. A single-film char combustion model and the Kunii−Levenspiel model were applied to describe the char combustion characteristics in the fluidized reactor. A genetic algorithm was employed to optimize certain combustion kinetic parameters: pre-exponential factor (8.51 m/s), activation energy (35.02 × 10 3 J/mol), and reaction order (0.78). The MFB-TG-MS system reported herein permits effective measurements of the rapid combustion kinetics closer to the intrinsic kinetics inside a fluidized bed reactor.