Microstructure of a Variety of Cokes After Alkali Enrichment

It is difficult to distinguish tamping coke and top charging coke by conventional testing methods, such as cold strength, abrasion resistance, reactivity and strength after reaction. Some of tamping coke's properties were even better than those of top charging coke, but from practical using effects of blast furnace, tamping coke was not as good as top charging coke. The reaction conditions were featured as high temperature, high alkali condition, intense reaction atmosphere and short time. Distribution of porosity in profile, microstructure and slag forming property of ash were analyzed and following conclusions were obtained. After alkali-rich reaction, there were obvious differences between top charging coke and tamping coke in microstructure. The porosity's unevenness of tamping coke was greater than those of top charging coke, and tamping coke was with less and big pores in out space and inner part was dense with more throughout pores. After phase diagram and microstructure analysis, it could be obtained that ash forming characteristics of top charging coke were better than those of tamping coke, and top charging coke's pores were blocked more seriously than those of tamping coke. From analysis of tuyere samples, it could be found that calcium content of ash in coke's pores was small and it should belong to coke's inherent ash; kalium (wK = 28%) was unusually high in coke, so the situation of high alkali was close to real blast furnace reaction condition.