| At present, China is in the process of industrialization of high-speed development stage and demand for steel of construction of our country is always strong. At the same time, demands for iron ore of iron and steel enterprise are strongly increasing. Lean iron ore accounts for about 98% of total available reserves and iron ore price are going abominable, which cause iron and steel enterprises reduce or stop their production. After the failure of 2010 iron ore pricing talks, the growth of iron ore average price in the first three quarters of this year was 56.31%. Chinese imports of iron ore in the first nine months has decreased to 457.6 Mt,11.53 Mt less than that of the same period last year, but more RMB13.03bn (＄1.92bn) was paid for the iron ore imports, according to statistics from the China Iron & Steel Association (CISA). China, the largest iron ore importer, forfeited its bidding right just for its strong demand for ore in the steel market and weak iron ore resources.Huimin iron ore in Yunnan Province reserves about 2 Bt, preliminary proven, and has the characteristics of shallow burial and easy mining, but has not been exploited up to present because of iron ore's low grade, fine size, complicated component and high-phosphorus content.Chinese vanadium-titanium magnetite reserve ranks the third in the world and distributes mainly over Chengde area of Hebei Province and Panzhihua area of Sichuan Province. The ore reserve in Panzhihua area with low content of harmful elements, such as sulfur and phosphorus, is more than 8 Gt, known as the biggest V-Ti ore base in China. Yunnan Province is rich in ilmenite with low content of impurities, such as silicon, aluminum, sulfur and phosphorus, which mainly exist in placers easy to be exploited. Proved reserve of ilmenite distributed over Yunnan Province is more than 20 Mt. However, traditional blast furnace (BF) has many difficulties in smelting these ores. Under decades of scientific researches by experts around the world, although fruitful achievements of smelting V-Ti magnetite by blast furnace were obtained, many problems still exist in the BF technology. For example, the generation of Ti(C,N) induces the formation of foaming slag seriously. Furthermore, jam of chargings and bubble flooding will be triggered, which results in the deterioration of BF state, the increase of iron loss and the decline of desulfurization rate. Therefore, it has an important significance to introduce new smelting technologies to exploit China's existing large "trash ore". Nowadays, the rapid development of non-blast furnace ironmaking technology is on their ways. At present, COREX has been industrialized in many countries, and HIsmelt is widely promoted throughout the world. Although the HIsmelt is not yet industrialized, its potential strongpoint, such as flexibility in raw materials, lower environmental impact and lower capital and operating costs, etc, has also attracted the attention of metallurgical industry.Ilmenite and Huimin high-phosphorus iron ore from Yunnan was smelted by oxygen enriched top-blown smelting reduction ironmaking technology, simulating HIsmelt, in the present experimental research. Much more details on smelting were discussed. Specifically, the influence of reduction temperature, slag basicity and carbon to oxygen molar ratio on the reduction quality level including iron recovery and titanium and sulfur contents in the pig iron produced in the experiment was investigated. Mixing smelting of Ilmenite and high-phosphorus iron ore are processing in the experiments.Conclusion could be drawn through first part experimental investigation. (1) Temperature, basicity and molar ratio of carbon to oxygen play dual roles in smelting. In order to maintain the fluidity of slag so as to obtain good metallurgical targets and keep high-basicity and moderate temperature slag of highly effective dephosphorization, take all these factors into consideration, iron recovery ratio could reach 85% with phosphorus content below 0.18%, sulfur content ca.0.06% and carbon content lower than 0.8% in pig iron under the conditions of holding time of 30 min at 1723K-1773K, aerating oxygen time of 10 min, basicity of 1.3-1.5, carbon to oxygen molar ratio of 0.9-1.0 and oxygen-enriched flow rate of 250L/h. (2) Although the strong oxidization atmosphere of technology does not conduce to desulfurization, sulfur content of pig iron, produced in the process, still reach the standard of pig iron for steelmaking with comparatively higher desulfurization ratio because sulfur burden of chargings is lower relatively and sulfur in liquid iron could combine with basic oxides to form compounds, existing in slag stably. (3) There are gasification dephosphorization and desulfurization in smelting process, because compounds containing phosphorus and sulfur exist in the smoke of exhaust gas. However, iron loss increases. (4) With all analysis, it is feasible to smelt Huimin high-phosphorus iron ore with phosphorus content of 0.90% by the technology. Besides, using non-coking coal as reductant with phosphorus and sulfur content as lower as possible conduces to depress burden of these harmful elements directly and improve pig iron quality.Conclusion could be got through second part experimental investigation. (1) Smelting ilmenite by oxygen enriched top-blown smelting reduction ironmaking technology is feasible, and the strong oxidation atmosphere could avoid generation of Ti(C,N), which induces formation of foaming slag seriously. Furthermore, jam of chargings and bubble flooding will be triggered, which results in deterioration of BF state and increase of iron loss and decline of desulfurization rate. (2) Temperature and basicity play dual roles in smelting reduction. To maintain the fluidity of slag so as to obtain good metallurgical targets and avoid the restriction of melting point of high-titania slag, all factors should be considered. Under the conditions of holding time at 1550℃of 30 min, basicity of 1.1, carbon to oxygen molar ratio of 1.0 and oxygen enriched flow rate of 250 L/h, the best smelting circumstance can be obtained and the iron recovery can reach 95% with Ti content below 0.05% in pig iron produced. (3) The sulfur content in pig iron is as high as 0.3%, which does not meet the requirements of steelmaking and is a defect of the technology that could not be eliminated. Thus, it is necessary to carry out external desulfurization for hot metal.Conclusion could be got through third part experimental investigation, mixing smelting of ilmenite and Huimin high-phosphorus iron ore. (1) iron recovery rate reach 95.1% when Huimin high-phosphorus iron ore mixed in the chargings. Phosphorus content in pig iron presents increase gradually, from 0.0026% to 0.61%. (2) Lpdecreases gradually from 10.8 to 1 but Ls increases gradually from 0.3 to 0.9 with Huimin high-phosphorus iron ore mixed in the chargings increases, which showed the advantages of dephosphorization and disadvantages of desulfurization of the technology. (3) Take all these factors into consideration, the result shows better when proportion of ilmenite and Huimin high-phosphorus iron ore is 1 to 1. Iron recovery rate reach 95.1% and phosphorus content in pig iron is 0.36%, sulfur content 0.054%, titanium content 0.031%. |
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