Multi-stage coking for increased tar yield and formed coke of high strength. 3. Multi-stage coking of single coals

Multi-stage coking of single coals (carbon content 79-88 wt%) was studied to reveal the influences of coal properties on the yield of tar and the strength of the formed coke from the heat-treated residue. The extracted tar yield was 13-25% tetrahydrofuran soluble products and 18-25% pyridine soluble products. The amount of total volatile product from a coal in the whole process was approximately correlated to the amount of volatile matter, the former exceeding the latter by 10-15%. The strength of the coke produced under standard conditions correlated closely with the rank of the starting coal, suggesting that the extracted residues inherit the coking properties of the starting coal. Different heat-treatment temperatures and higher moulding pressures were applied to increase the strength of the formed coke from Newdell coal (the lowest rank coal used in this study).