An updated approach to refining the core indicators of pulverized coal used for blast furnace injection based on principal component analysis is proposed in view of the disadvantages of the existing performance indicator system of pulverized coal used in blast furnaces. This presented method takes into account all the performance indicators of pulverized coal injection, including calorific value, igniting point, combustibility, reactivity, flowability, grindability, etc. Four core indicators of pulverized coal injection are selected and studied by using principal component analysis, namely, comprehensive combustibility, comprehensive reactivity, comprehensive flowability, and comprehensive grindability. The newly established core index system is not only beneficial to narrowing down current evaluation indices but also effective to avoid previous overlapping problems among indicators by mutually independent index design. Furthermore, a comprehensive property indicator is introduced on the basis of the four core indicators, and the injection properties of pulverized coal can be overall evaluated.
Through the mass balance and thermal balance calculation for a typical OxyCup （or OxiCup） furnace process featuring a capacity of 380 kt/a of steel plant residuMs, the material flow and thermal flow diagrams were firstly obtained. Then, the performance of the main fuel in the OxyCup process, i.e. coke and carbon dust, was ana lyzed, and the results indicated that coke was mainly used as the stock column skeleton for the furnace and exothermal agent with a weak reduction ability; whereas carbon dust was mixed in the C-brick to reduce the iron oxide. In addition, the comparison between OxyCup process and traditional blast furnace process indicated that the reduction and melting processes in the OxyCup process were relatively isolated, while in the traditional blast furnace process, they were mixed with each other in the high temperature zone. Moreover, oxidizing atmosphere is necessary in part of the OxyCup furnaces to ensure the complete combustion of part of the coke, while only reducing atmosphere is al lowed in traditional blast furnaces. Finally, it was confirmed that oxygen enrichment can make a remarkable increase of the energy income and high temperature blast makes oMy a small contribution to energy income as the energy from the combustion of carbon takes up nearly 90% of the total income.
Ke-jiang LIJian-liang ZHANGZheng-jian LIURui MAOTian-jun YANG
Under the pressures of both the de＇crease of high-grade high quality iron ore resources and the increase of raw material costs, the iron and steel enter＇prises in China turn to adopt iron ores which contain special elements such as nickel, manganese, etc. in the sintering blend. Anaiytica｜ reagents were used for sintering experiments, and the sinters were analyzed with X-ray diffraction, s6ailning electron microscopy and mineralogical microscopy to study the effect of nickel on the silico ferrite of calcium and aluminum （SF（＇A） bonding phase formation during sinte- ring. The results indicated that SFCA was divided into nickel containing and nickel-free areas due to the presence of nickel. The increasing content of nickel would greatly reduce the content of SFCA and promote the formation of calcium aluminum silicate. A great deal of Fe2 Oa participated in the crystal transition to Fe3 O3 , reducing the a mount of Fe2O2 involved in the formation of calcium ferrite. When the blending ratio of NiO, which is used to provide the nickel in the sintering process, is less than 3 % , the calcium ferrite is in substantially interleaving cot rosion with hematite and magnetite. Both the porosity and silicate glass phase content are low, which contributes to the sintering production.
Assimilation behaviors of 7 kinds of iron ores from Australia, Brazil, India, South Africa and China were evalua-ted and analyzed. On the basis of that, four ore blending principles were proposed, and seven groups of iron ore pow-der blending schemes were designed. The ores of different types or from different places are shown apparently differ-ent in assimilation. The assimilation of hematite in Australia, Brazil and India is relatively high, but the assimilation o{ magnetite in South Africa and China and specularite in China is relatively low. The assimilation of the ores has negative correlation with MgO content and binary basicity, while the assimilation of the ores has positive correlation with porosity, SiO2 and Al2O3 contents, and crystal water. The iron ores with smaller crystal size and microstruc- ture looseness have relatively higher assimilation. Assimilation of mixed ores has relationship of linear, arch and ＂S＂ types to the ratio of single iron ore powder. When the charge ratio of ore is less than 25%, it possesses additivity, providing theoretical basis for optimization of ore matching.
SU Bu-xinZHANG Jian-liangWANG DaSHAO Jiu-gangREN ShanWANG Guang-wei
