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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 1 000°C with a quartzmade 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.

Seven kinds of caking coals with carbon contents of 80−88 wt % dry and ash-free basis (daf) have been carbonized in high-purity He at 3 °C/min up to 1000 °C with a fixed-bed quartz reactor, and the fate of coal-bound nitrogen (coal N) has been investigated in detail. The nitrogen mass balances fall within 97−104%. Most coal N is retained as quaternary N in the cokes, and the rest is released as volatile N (tar N, HCN, NH 3 , and N 2 ). NH 3 is the main N species evolved below 650 °C, irrespective of the kind of coal, and the profile for the rate of NH 3 formation shows the main peak at about 450 °C, followed by a small peak at around 670 °C in every case. Significant amounts of HCN are also observed below 650 °C, and the rate profiles for HCN as well as NH 3 exhibit two peaks at around 450 and 670 °C, whereas most N 2 is formed at the temperature range of 650−1000 °C. The distribution of volatile N at 1000 °C is in the order of tar N < HCN < NH 3 ≈ N 2 for almost all coals. Each coal used gives a Gieseler maximum fluidity (MF) of 1.1−4.0 log(ddpm) at around 450 °C (440−480 °C), and it seems that the MF value tends to increase when the total amount of either HCN or NH 3 evolved up to 450 °C increases.

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