On the possibility of using coking plant waste materials as additives for coke production

Cocarbonizations of a coking coal and different additives have been studied to evaluate the utilization of hazardous wastes from the byproducts coking plants in the production of metallurgical cokes. Five waste materials, three from the tar decanter and two from the benzol distillation column, have been considered together with a series of selected plasticizing additives as reference materials. The latter series includes a crude,ar, one impregnating coal-tar pitch, and three binder coal-tar pitches. The ability of an additive to modify the Gieseler fluidity of the cocarbonizing systems (coal and additive) is associated with the amount of volatile matter released between 400 and 500 degrees C by the additive. It was found that the higher the volatile matter released in this temperature range by the additive, the higher the fluidity of the system. This fact causes an enhancement in anisotropy development toward granular flow component in cokes produced from blends of a coking coal and the additives and also a better bonding at the interface between carbon anisotropic components and coal-inerts. The changes in coke structure which are controlled by the fluidity of the cocarbonizing systems lead to an improvement in coke quality parameters such as a reduction in coke fines production and more resistance to carbon dioxide attack. From the comparative study between waste materials and reference caking additives, it can be concluded that although wastes are not so effective as binder coal-tar pitches, these hazardous waste materials can be used as additives in cokemaking, improving coke quality, and can then be recycled thereby helping to solve an environmental problem.