焦炭在白云鄂博矿高炉冶炼中的热态性能变化

 冶金焦炭已经成为现代高炉炼铁技术所需的必备原料之一,被喻为钢铁工业的“基本食粮”,具有重要的战略价值和经济意义。随着低碳时代的来临和大喷煤技术的运用,焦炭的功能逐渐被替代。为了保证炉内的透气性以及透液性,作为高炉软熔带的“百叶窗”,焦炭作为料柱骨架和通道的作用更为突出,因此深入理解焦炭在白云鄂博矿高炉冶炼过程中的热态性能变化对指导白云鄂博矿的高效冶炼至关重要。以从包钢4号高炉中取出的入炉焦与风口焦为研究对象,使用X射线衍射仪、热重立式炉、扫描电镜、能谱仪等分析手段,对比研究了它们的基础特性、灰分的主要物相、反应性(CRI)与反应后强度(CSR)、微观孔隙结构及碱金属的含量及分布,从而得到焦炭在白云鄂博矿冶炼中的热态性能变化。结果表明,高炉中的焦炭在下降过程中发生气化反应,灰分含量提高,挥发分含量降低,SiO₂含量显著降低,但是CaO、K₂O、Na₂O、MgO等碱性氧化物含量有所增加。二次加热前期焦炭发生氮气吸附,质量没有减少反而增加;后期焦炭发生碳气化反应,质量快速下降,风口焦的反应性提高,反应后强度降低。风口焦表面出现了类似蜂窝状的孔隙,且孔隙分布不均匀,特别是被渣铁侵蚀的焦炭基质,其气孔壁变得粗糙,孔隙出现合并。碱金属在风口焦中富集,碱性氧化物含量增加。风口焦石墨碳所对应的(002)衍射峰半峰宽急剧减小,扁平峰消失,峰形尖锐。晶体结构趋向有序,石墨化程度提高。

Changes in thermal performance of coke in blast furnace smelting process of Bayan Obo mine

Metallurgical coke has become one of the necessary raw materials for modern blast furnace ironmaking technology. It is known as the "basic food" of the iron and steel industry, and has important strategic value and economic significance. With the advent of low-carbon era and the application of large-scale coal injection technology, the functions of coke have been gradually replaced. In order to ensure the air permeability and liquid permeability in the furnace, as the "louver" of blast furnace reflow belt, its role as the material column skeleton and channel is more prominent. Therefore, a deep understanding of thermal performance changes of coke in the smelting process of Bayan Obo mine is significantly important to guide its efficient smelting. The feed coke and tuyere coke were taken from No.4 blast furnace in Baotou Steel as the research object. X-ray diffractometer, thermogravimetric vertical furnace, scanning electron microscope, energy spectrometer and other analysis methods were used. The differences in the basic characteristics, main phases of ash, coke reaction index(CRI), coke strength after reaction (CSR), microscopic pore structure, and the content and distribution of alkali metals were compared and analyzed. Finally, the thermal performance of coke in the smelting process of Bayan Obo mine were obtained. The results show that the coke in the blast furnace undergoes a gasification reaction during descending process, ash content increases, volatile matter content decreases, and SiO₂ content decreases significantly, but the content of basic oxides such as CaO, K₂O, Na₂O, and MgO increases. In the early stage of secondary heating, nitrogen adsorption occurs in the coke, and the quality does not decrease but increases. In the later stage, the coke undergoes carbon gasification reaction, and the quality decreases rapidly, reactivity of tuyere coke is improved, and strength after the reaction is reduced. There are honeycomb-like pores on the surface of tuyere coke, and distribution of pore is uneven. In particular, the coke matrix eroded by slag and iron has rough pore walls, and the pores appear to merge. Alkali metals are enriched in tuyere coke, the content of alkaline oxides is increased. The half-width of (002) diffraction peak corresponding to the tuyere coke graphite carbon is sharply reduced, flat peak disappears, and the peak shape is sharp. The crystal structure tends to be ordered, and the degree of graphitization increases.