Feedstock recycling of plastic wastes/oil mixtures in cokemaking

Two lubricating oils, a plastic waste composed mainly of polyolefins (95%) and their mixtures (1:1 w/w) were assessed for possible use as minor components of coal blends for metallurgical coke production. The addition of 2 wt% plastic waste causes a decrease in the maximum fluidity of the coal developed during thermal heating between 400 and 500 °C. At the same addition rate, the two oils are good additives for mixing with coal/plastic blends in order to partially restore the caking ability of the co-carbonizing systems. Co-carbonizations of the coking blend with the different wastes were carried out in a movable wall oven of 15 kg capacity. Although the bulk density remained unchanged, the addition of the plastic waste produced an increase in coking pressure to values that were too high for it to be considered as a safe blend. At the same time the mechanical strength of the partially gasified coke was improved as reflected by the CSR index. The oils, however, had the effect of reducing bulk density and the coking pressure generated during the process. When blended with the coal and the plastics, the oils appeared to act as good solvents of the polyolefins and also proved to be effective in decreasing coking pressure without negatively affecting coke quality.