Comparison of reaction characteristics and kinetics between tar thermal cracking and steam reforming in a micro fluidized bed reaction analyzer

In this study, a micro fluidized bed reaction analyzer (MFBRA) was used to examine the reaction characteristics of tar steam reforming and thermal cracking in the temperature range of 750-950℃ and steam partial pressure (SP) of 10%-30%. The production of gaseous products and the conversion of total carbon in the gaseous products and the conversion of tar were completely analyzed. The reaction kinetics was also calculated. The results show that during tar thermal cracking, with the increase of reaction temperature, the yields of H2, CH4, CO and CO2 and the conversion of total carbon in the gaseous products increased, and the reaction time decreased. However, in the process of tar steam reforming, by raising the reaction temperature, the reaction time was prolonged largely, and the yields of H2, CH4, CO and the conversion of total carbon in the gaseous products increased significantly, while that of CO2 reached the maximum value at 850℃. During this process, it included not only tar thermal cracking but also the reforming reaction between tar components and the reaction intermediates. At 950℃ and SP of 30%, the conversion of total carbon in the gaseous products reached 92.34%. For the tar steam reforming, with the increase of SP, although the yields of gas components and the conversion of total carbon in the gaseous products increased, the corresponding reaction rate decreased. At the same reaction temperature, with the increase of SP, the generation rates of CO, CH4 and the rate of total carbon conversion in the gaseous products increased, the H2 reaction rate gradually decreased with a long stable zone, while the CO2 reaction rate reached its maximum value at 850℃. The activation energy (Ea) of the gaseous products (H2, CO, CO2 and CH4), the conversion of total carbon in the gaseous products and the tar conversion were 90.10, 42.01, 58.56, 64.92, 61.44 and 63.26 kJ/mol, respectively. The corresponding values were obviously less than that of tar thermal cracking. It indicated the promotion effect of steam on tar conversion. Finally, the tar thermal cracking kinetics data was compared with the literature data to verify the feasibility of the MFBRA tar steam reforming reaction test and the accuracy of the analysis results. © 2022, Editorial Board of CIESC Journal. All right reserved.