FACTORS AFFECTING THE REACTIVITY OF CHARS AND COKES DURING LOW-TEMPERATURE (640-DEGREES-C) STEAM GASIFICATION

Coal chars and petroleum cokes were prepared by low-temperature pyrolysis, both in the absence and presence of NaOH. The solids obtained were gasified with steam at 640-degrees-C, either as-prepared or after impregnation with a K-Ca oxide catalyst. The uncatalyzed steam gasification rate increases with NaOH loading, and slows with increasing time on stream due to the slow vaporization of sodium, the decrease in contact time as the char/coke is consumed, and the lower reactivity of the residue that remains. The K-Ca oxide catalyst accelerates gasification, especially for NaOH-containing solids. Pyrolysis temperature and gasification pressure had minor effects. Gasification reactivity depends on the source of carbon, which is related to the structure of the fixed carbon, and quality of catalyst dispersion.