Effects of H2 and CO on Char-Gasification Reactivity at High Temperatures

Coal-char-gasification reaction in a mixture of H2O, CO2, H-2, and CO was conducted in a fixed-bed tube reactor at atmospheric pressure. The effects of H-2 and CO on CO2-gasification and steam-gasification reactions were studied from 1100-1400 degrees C. Experimental results indicated that H-2 promoted the steam-gasification reactivity of coal-char, especially at low temperatures. The inhibition effect of CO on steam gasification was apparent. H-2 promoted the CO2 gasification of coal char at 1100 degrees C but inhibited it above 1300 C. CO inhibited CO2 gasification from 1100-1400 degrees C. The random-pore model was suitable for all experimental conditions. Kinetic analysis showed that the effects of temperature on gasification reactivity differed in various raw gases. Arrhenius plots revealed that the steam gasification mechanism may be altered in steam or steam/H-2 from 1100-1400 degrees C. Within this temperature range, steam gasification (in H2O/CO and H2O/H-2/CO) and CO2 gasification (in CO2, CO2/H-2, CO2/CO, and CO2/H-2/CO) were considered to be chemical-reaction-controlling stages.