Effect of KOH loading on different coals hydrogasification

The effects of KOH loading on the hydrogasification of Hohhot(HH) coal and Pingzhuang(PZ) coal from Inner Mongolia were studied in a pressurized fixed-bed reactor, and the analysis methods of slag washing, atomic absorption and XRD were adopted to investigate the intrinsic characteristics of coal structure that affect the hydrogasification reactivity. The experimental results show that the total gas productivity of HH coal hydrogasification can be enhanced obviously by increasing the catalyst loading, and the catalyst loading saturation level is about 15%. On the other hand, KOH shows an inconspicuous effect on PZ coal hydrogasification unless the catalyst loading is higher than 30%, and the total gas productivity does not exceed 64% within 60 min reaction time when the catalyst loading is 50%. The XRD results indicate that as the hydrogasification proceeds, the catalyst is deactivated by reacting with the ash in coal, and the unreacted carbon in PZ coal is gradually transformed into less active graphite, resulting in a lower gasification rate at later reaction time. The ratio of water-soluble potassium to water-insoluble but acid-soluble potassium in the hydrogasification residue is closely related to the catalytic activity. When the catalyst loading is less than 20%, the high content ash in PZ coal will deactivate most of the loaded KOH, leading to a slow hydrogasification rate.