Abstract
The present study focuses on examining the fate of coal-S and coal-N during carbonization in detail and making clear the effects of these elements on coal fluidity and coke strength. When eight kinds of caking coals with 80–88 mass%-daf C are carbonized in high-purity He at 3°C/min up to 1000°C with a quartz-made fixed bed reactor, 50–75% of coal-S remains as FeS and organic-S in the coke, and the rest is released as tar-S and H2S. Most of coal-N is also retained in the coke, and the remainder is converted to tar-N, HCN, NH3 and N2. The eight coals give Gieseler maximum fluidity values between 435 and 480°C, and the value tends to be larger at a smaller sulfur content in coal or in the carbonaceous material recovered after carbonization at 450°C. It also seems that the value increases with increasing nitrogen content in coal or total amount of either HCN or NH3 formed up to 450°C. Furthermore, the addition of S-containing compounds to an Australian bituminous coal lowers coal fluidity and coke strength considerably, whereas indole gives the reverse effect on them. On the basis of these results, it is suggested that coal-S or some coal-N has a negative or positive effect on the two properties, respectively.
