A near-in-situ sampling analytical technology on coal char structural evolution research

The characterization of coal char's structure during CO2 gasification, which significantly influences reaction reactivity, has garnered increasing research attention. Most of this research focuses on the characterization and analysis of samples collected after gasification and cooling which could be defined as batch sampling (BS). In this research, coal gasification conducted in a CO2 atmosphere was studied for the first time using a micro fluidized bed equipped with an on-line particle sampling device. Samples were instantaneously extracted and rapidly cooled during the reaction to near-in-situ effects which could be defined as on-line sampling and (OS). The results show that the content of amorphous carbon initially rises and then declines with the gasification. The specific surface area and pore diameter increase with the reaction time and reaches the maximum value at 7hours. After 9hours, the specific surface area is noted to diminish, a consequence of the collapse of certain pores. There is the same law of variation in both OS and BS results in the above analysis. However, from the functional groups of the coal char, the OS results exhibit a higher retention of these groups such as oxygen-containing functions compared to the BS counterparts. Based on the results presented, the near-in-situ sampling analytical technique employed in this study shows promise as an optimal method for evaluating structural changes during chemical reactions. Additionally, this particle sampling method used during the reaction process can be applied to analyze particle changes in other gas-solid two-phase reaction processes, enabling near-in-situ analysis. •A micro-fluidized bed with an on-line particle sampling system was employed to investigate the CO2 gasification of coal.•Sampled coal char retains more oxygen-containing functional groups, offering deeper insights into gasification.•This near-in-situ sampling technique offers valuable insights into the dynamic changes in the carbon structure of coal char CO2 gasification.