A Comparison of the Gas‐Product‐Release Characteristics from Coal Pyrolysis and Hydrogasification

Abstract

Abstract Coal pyrolysis and hydrogasification were investigated in a laboratory‐scale pressurized fixed‐bed reactor to examine the effects of temperature, pressure, and catalyst on the gas productivity and yields under different gas atmospheres. The experimental results show that the methane yield is significantly higher under a hydrogen atmosphere. The release rate curve of methane during hydrogasification has three obvious peaks which are the results of coal devolatilization and rapid hydrogenation, the secondary reaction of volatile products, and the slow hydrogenation of residual char, respectively, whereas that of pyrolysis only exhibits the first peak. Changes in temperature and pressure have more remarkable effects on coal hydrogasification than on pyrolysis. Nickel and calcium‐based catalysts influence the rate of CO and CO 2 formation but little effect was observed on low‐carbon hydrocarbon production. Potassium‐ and sodium‐based catalysts have a significant effect on the formation of methane under a hydrogen atmosphere. The FTIR spectra show that hydrogen is easily bound to carbon if of potassium‐ and sodium‐based catalysts are used, and CC bond formation is inhibited, which reduces the aggregation of graphite which has very poor activity. Therefore, potassium‐ and sodium‐catalyzed samples could maintain high activities during hydrogasification.