Nature and origin of coke quality variation in heat-recovery coke making technology

摘要

The use of non-recovery/heat-recovery cokemaking technology offers new possibilities for coke makers. The literature shows that most of the knowledge about the development of coke properties is based on work done on the traditional by-product cokemaking technology. This study investigates the nature and origin of the variation in coke strength after reaction (CSR) obtained in different regions of the heat-recovery oven chamber. Coke fingers collected from three different zones (bottom center, top center, and top right) of a commercial heat-recovery oven were studied. Coke fingers were collected intact and studied incrementally, starting from tar line to cauliflower end. Coke samples were investigated using the CSR test, gas adsorption techniques, optical microscopy, and X-ray diffraction analyses. The results show that the CSR trend in the bottom center region of the oven is unidirectional, increasing from tarline to cauliflower end, whilst a curving CSR trend is observed in coke collected from top center and top right regions of the oven. The highest CSR value was found in the bottom center region, a characteristic attributed to limited swelling, which inhibits porosity development in this region. It was found that, while the CSR trend along the coke finger is influenced by both the porous structure and carbon matrix, variations in CSR are better explained by porosity-related properties, particularly pores in the mesopore range (2-50 nm pore diameter). Swelling patterns in different zones of the oven appear to have a significant role in the determination of mesopore volume. For cokes with high surface area available for solution-loss, contrary to expectations, a weak relationship was found between CSR and carbon matrix development, as expressed by crystallite height and percentage of less-reactive carbon forms. (C) 2016 Elsevier Ltd. All rights reserved.