Study on the influence of particle size and heating rate on pyrolysis characteristics and kinetics of Xinjiang high-chlorine coal

Xinjiang high‑chlorine coal has abundant reserves, but its high chlorine content causes slagging, ash deposition and equipment corrosion during pyrolysis, limiting its large-scale utilization. This study investigated the effects of particle size (54–200 μm) and heating rate (10–30 °C/min) on the pyrolysis characteristics and kinetics of Shaerhu coal (SEH) using TG-DTG analysis, the Coats-Redfern method and model-free methods. SEH pyrolysis involved three stages, with weight loss peaks near 100 °C, 450 °C and 715 °C. SHE's peak mass loss rate temperature was 10–30 °C lower than other low-rank coals. Larger particles significantly increased the weight loss rate, peaking at 0.1164 %/°C for 150–200 μm. Higher heating rates shifted DTG curves upper right, reduced mass loss rates and increased thermal hysteresis. C-R method indicated that in Stage I, higher heating rates raised activation energy ( E ). In Stage II, particle size influenced E more than heating rate. In Stage III, larger particles had lower E (19.51–34.09 kJ·mol −1 reduction from 54–76 to 150–200 μm). Model-free methods showed consistent E trends, but generally Friedman > FWO > KAS. A notable E decrease occurred at 0.8 conversion for 54–76 μm particles, while 150–200 μm particles declined gradually from 220 kJ·mol -‍1 after 0.4 conversion. • The pyrolysis kinetic of Xinjiang high- Chlorine coal was first calculated. • SEH's peak mass loss rate temperature is 10–30 °C lower than other low-rank coals. • The peak weight loss rate increases with raising particle size by 24.5–26 %. • The degree of thermal hysteresis increases with the decrease of particle size. • The effects of particle size and heating rate on E are various at different stages.