Influence of Coke Deterioration Behavior in Blast Furnace on Microcrystalline Structure Characteristics

With the large-scale blast furnace and the wide application of oxygen enriched coal injection technology, the coke quality and its deterioration mechanism in the blast furnace are receiving significant attention in recent. By means of the characterization techniques such as chemical analysis, image analysis and X‑ray diffraction, the influence of oxygen enriched coal injection on coke quality and the deterioration mechanism of coke were revealed from the change trend of particle size, chemical composition, pore structure and microcrystalline structure of tuyere coke. The results showed that the feed coke would make particle size decrease significantly through the friction extrusion, at the same time through chemical erosion and high temperature reaction with different atmosphere medium in the blast furnace. The ash content of tuyere coke was significantly higher than that of feed coke, alkali metals and iron content in ash was enriched in tuyere, and calcium content was significantly increased. The proportion of slag and iron decreases first and then increases with the increasing the depths of tuyere, and reached 85% at the depths of 2.5–3 m in tuyere. The surface of tuyere coke pores was smoother; the small pores were expanded to micron scale and appeared round with large number of gasification reactions for coke in the blast furnace. The microcrystalline structure of graphitization increased obviously through high temperature reaction and the resistance of isotropic coke, silk carbon and fragments to high temperature alkali erosion is stronger than that of other anisotropic structures in coke.