Evolution of char structure during cobalt‑calcium catalyzed coal hydrogasification and its impact on gas-solid hydrodynamics of gasifier

This study aims to cognize the evolution of char structure during Co-Ca catalyzed coal hydrogasification and its influence on gas-solid hydrodynamics of gasifier. Co-Ca catalyzed coal hydrogasification was carried out in a pressurized bubbling fluidized bed at 1123 K and 3 MPa. The results showed that the initial 5 min of coal hydrogasification can be considered as coal hydropyrolysis period. Particle size increased during coal hydropyrolysis, reduced when carbon conversion lied below 69% and then remained basically stable during char hydrogasification. The apparent particle density decreased progressively. Micropores were formed in abundance during coal hydropyrolysis and then decreased gradually during char hydrogasification. Whereas mesopores kept increasing and the macropores firstly increased then collapsed with carbon conversion. The simulation results of gasifier suggested that more particles aggregated at the bottom of the gasifier during coal hydropyrolysis, and the gas-solid flow state changed increasingly from bubbling to turbulent during char hydrogasification.