Investigation of Coke Quality Variation between Heat-Recovery and Byproduct Cokemaking Technology

• Published in: Energy & fuels 2017-02, Vol.31 (2), p.2087-2094
• Main Authors: Nyathi, Mhlwazi S, Kruse, Richard, Mastalerz, Maria, Bish, David L
• Format: Article
• Language: English
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/acs.energyfuels.6b02817

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.