Pyrolysis behavior of coal in a moving bed with baffled internals under different residence times

In view of the problems faced by the conventional moving bed coal pyrolysis process, such as the inability to deal with pulverized coal, low light tar yield, poor tar quality, etc., a moving bed pyrolysis process with baffled internals was developed to control the heat and mass transfer of the gas-solid two-phase and the pyrolysis reaction process. The multi-stage gas gathering system can collect the oil and gas products released in different pyrolysis stages of coal in time. The pyrolysis behavior and product quality of Naomaohu coal at different temperatures and residence times were investigated. The results show that the baffle internals enhance the heat and volatile matter transfer between particles, enabling it to process 0.4−6.0 mm pulverized coal. When the pyrolysis temperature is 550 ℃ and the residence time is 3 h, the pyrolysis tar yield reaches the highest 11.38%, which is 86.87% of the Gray-King assay yield, and the mass fraction of light components below 360 ℃ in the tar fraction is 85.0%. With the extension of the residence time, the H₂ volume fraction in the pyrolysis gas increases from 22.1% to 35.1%, and the CO volume fraction increases from 8.0% to 9.5%. The tar yield in the first and second layer reactors increases with the extension of the residence time, and the maximum tar yield in the third and fourth layer reactors is obtained when the residence time is 2 h. As the number of beds increases, the content of light components in the tar simulated distillation fraction increases, the content of tar aliphatic hydrocarbon compounds decreases, and the content of monocyclic aromatic hydrocarbons and bicyclic aromatic hydrocarbons gradually increases. Based on the above research, it provides technical support for large-scale industrial processing of small particle size pulverized coal, and preparation of higher yield and quality tar.