Colloids with good thermal stability can be formed when heated. Coke with large size, few cracks, high crushing strength and good wear resistance can be obtained when coking alone.
However, the generated expansion pressure makes it difficult to push coke, so it is necessary to add gas coal and lean coal to improve the operating conditions and coke quality. In coking coal blending, coking coal can play the role of coke skeleton, reduce shrinkage stress, thus improving the mechanical strength of coke, and is a high-quality coking raw material.
The dry ash-free volatile matter vdaf of the first type coking coal =10% ~ 28%, and the caking index g >；; 65, maximum thickness of colloidal layer, y≤25mm. The coking performance of this part of coal is particularly good, and qualified blast furnace coke can be produced independently.
Another kind of coking coal has a dry ash-free volatile matter VDAF = 20% ~ 28% and a caking index G = 50 ~ 65, and its coking property is worse than the former. Coking coal is a typical coking coal with medium volatile matter and good caking property.