Study on Tar Property from Coal Mild Gasification with Calcium Oxide Catalyst

Tars in both the presence and absence of calcium oxide were analyzed and compared. The results indicated that tar yields reach the maximum at 650 degrees in the absence of calcium oxide. It is in accordance with Tyler's results. But when calcium oxide is added, the temperature of tar maximum yield is only 550 degrees C. It is also demonstrated that the ratio of H/C, BTX, PCX and other light content in tar increase while the ratio of (O+N+S)/C and oxide compound in tar decrease in the presence of calcium oxide. It is noted that the maximum composition of alkanes in tar is C14∼C20 in the presence of calcium oxide while is C8∼C15 in the absence of calcium oxide. The yield of phenolic compounds was higher in the presence of calcium oxide than the raw coal alone. The result disagrees with the reported literature. The difference may arise from differences in temperature and gas or solid residence time, or from the difference of activity of calcium oxide used.