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Coke samples obtained by carbonizing a commercial coal blend in a pilot-scale moveable wall slot-oven were studied to evaluate the influence of oven bulk density and coking rate on coke structural quality. Coke samples were investigated using the coke strength after reaction (CSR) test, gas adsorption techniques, optical microscopy, and X-ray diffraction analyses. The results show that an increase in oven bulk density and coking rate led to an increase in CSR, a phenomenon attributed to enhanced coal particle adhesion and improved plasticity during the plastic stage. Surface area, total porosity, pore area, and cell wall measurements indicate that the compact nature of coal charge under high oven bulk density and accelerated events under a rapid coking rate result in limited pore structural development, leading to a less porous coke. An increase in coke oven bulk density resulted in the growth of carbon forms and also improved the degree of crystallization. However, the proportion of less-reactive carbon forms and extent of crystallization decreased with an increase in coking rate, a limitation ascribed to a lack of sufficient time to fully develop when a faster coking rate is employed. Furthermore, as indicated by a decrease in the range of CSR and structural properties, coke quality homogeneity along the oven width improved with higher oven bulk density and coking rate. A positive relationship was found between CSR and crystallite height, as well as between CSR and carbon forms development. Contrary to literature reports, a weak relationship was found between CSR and surface area; however, the importance of all pore sizes was shown by a positive relationship between CSR and total porosity.

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Coke structural properties that lead to coke quality difference between heat recovery and byproduct cokemaking technology are investigated. Coke fingers collected from two zones (bottom center and top center) of a commercial heat recovery oven were analyzed and compared to the coke produced from the same coal blend using a moveable-wall slot oven. Coke fingers were studied at set intervals, starting from the floor of the heat recovery oven through the top of the bed, and from the slot oven wall to wall. Coke strength after reaction (CSR) test, gas adsorption techniques, optical microscopy, and X-ray diffraction analyses were used to study the coke samples. Although exhibiting lower overall CSR compared to the heat-recovery oven coke, the slot oven produced a more uniform coke quality along the coke cake width, because of the narrow width and bilateral heating of the slot oven. The top-section coke of the heat-recovery oven displayed unique structural characteristics ascribed to the availability of free space atop this coke and the use of radiant heat to drive its coking process. The heat-recovery oven bottom center and slot-oven coke displayed low surface area and total porosity, indicating restrictive coke cake expansion. Limited swelling is attributed to the coal charge weight overlying the heat-recovery oven bottom coke and the constrained nature of the slot-oven chamber. However, the shorter coking time used in the slot oven disadvantageously deprives the slot-oven coke of sufficient time to fully develop its carbon structure; therefore, the heat-recovery oven cokes demonstrated better carbon structural development. For the slot-oven coke, carbon structural development seems to have a stronger impact on CSR than surface area does, while for the heat-recovery oven top center coke, surface area appears to be the parameter that most affects CSR.

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