Characteristics of Tar Catalytic Reforming by Char in a Micro Fluidized Bed Reaction Analyzer and the Kinetics of Gas Component Generation

Abstract

In this research, the non-isothermal and isothermal reaction behavior of tar catalytic conversion by char was tested by a thermogravimetric analyzer (TGA) and a micro fluidized bed reactor analyzer (MFBRA), respectively. The TGA analysis shows that the obvious catalytic action can be found at the temperature above 873 K. In the MFBRA measurement, the roles of heat and catalysis during tar catalytic conversion from char were examined by comparing tar thermal cracking and catalytic reforming. The results show that, regardless of tar thermal cracking and catalytic reforming, the isothermal reaction behavior can be divided into the primary reaction stage (S1) and the secondary reaction stage (S2). In S1, the reaction behaviors in terms of reaction time, tar conversion, and gas yields, were very similar, indicating the dominant role of heat effect. In S2, the process of tar catalytic conversion needed longer reaction time with higher tar conversion and more gas products emission, manifesting the significant role of catalytic action played. In the examined temperature range of 1023 -1223 K, the temperature effect on gas component during tar catalytic reforming by char included promotion (CO, CH 4 , H 2 , and CO 2 ), suppression (C 2 H 6 , C 3 H 6 , and C 3 H 8 ), and synergy (C 2 H 4 ). For the reaction kinetics, the activation energy of each gas component generation and the total gas product in S2 was much higher than that in S1, indicating the presence of chemical reaction control during this phase. The findings were beneficial to understand tar catalytic reaction by char deeply and provide data support for the design and optimization of tar removal unit in a gasification process.

Keywords: Tar, char, Catalytic reforming, thermal cracking, Kinetic, Micro fluidized bed