Experimental study and application of increasing the proportion of lump ore used in Anyang Iron and steel blast furnace

　　Through the experimental research and chemical composition analysis on the high temperature performance of lump ore, in the actual production, select and use lump ore varieties with low expansion rate, less negative impact on the thermal performance of coke, higher effective grade, and lump ore composition that are conducive to the reasonable control of charge composition system and the improvement of high temperature performance, such as Newman block, Pb block or Roy Hill block, Through the optimization of the type of burden structure lump ore and the reasonable control of the proportioning proportion, the linkage reduction of structure cost and processing cost under the condition of maintaining the long-term stability of the blast furnace is realized, and the output benefit is also remarkable.

　　Key words lump ore test research application output

　　It is the easiest and most effective way to reduce the cost of iron by optimizing the structure of raw materials. The metallurgical value effect evaluation and analysis of blast furnace burden (sinter, pellet and lump ore) shows that the value effect of lump ore is the best in most periods, followed by sinter, and the value effect of pellet is the worst [1-4]. In terms of blast furnace burden structure optimization, Anyang Iron and steel has made many attempts, and the effect is not ideal. The proportion of lump ore with good value effect is at the middle and low level, while the proportion of pellet ore with poor value effect is too high, As a result, it is difficult to reduce the structural cost of the blast furnace, which restricts the exertion of the cost reduction effect before ironing. Therefore, ensuring the smooth operation of blast furnace and increasing the proportion of lump ore with good price efficiency have become an urgent problem to be solved before reducing the cost of Anyang Iron and Steel Co. By studying the reduction degree of lump ore, low-temperature reduction pulverization, high-temperature free expansion rate and the influence of different lump ore on the thermal properties of coke, combined with the chemical composition of lump ore, selecting appropriate lump ore types, promoting the optimization of furnace burden composition system, improving furnace conditions, and achieving good results.
 

　　1. Analysis on the current situation of block ore utilization

　　1.1 current situation, level and development trend at home and abroad

　　At present, both domestic and foreign blast furnaces have made great efforts to increase the proportion of lump ore into the furnace, and achieved good results. The proportion of lump ore in Baosteel No. 4 blast furnace has been increased to more than 20%, the furnace condition is smooth and stable, and the indicators are good [5], and the proportion of lump ore in Shaogang No. 6 blast furnace has been increased to 22.1% [6]. Most steel mills in Japan and other Asian countries use more than 15% of lump ore, some even more than 20%. This can give us two inspirations: first, the addition of about 20% high-quality lump ore will not have a great impact on the blast furnace index; Second, the blast furnace burden structure should pay attention to the use cost and control the use of expensive pellets. By optimizing the burden structure, properly increasing the proportion of lump ore will not have an adverse impact on the smooth operation of the blast furnace.

　　1.2 application status of Anyang Iron and steel block mine

　　The blast furnace of Anyang Iron and Steel Group mainly uses South African block in terms of block ore, especially in rainy season, which forms excessive dependence on South African block. However, from the production practice of 3# blast furnace in recent years, when the proportioning ratio of South Africa block exceeds about 15%, the smooth operation of blast furnace will be affected, especially when the proportioning ratio reaches 18% ~ 19%, the blast furnace condition is difficult to occur frequently. The analysis shows that this is inseparable from the impact of the excessive proportioning ratio of South Africa block. Although the price efficiency of South Africa block is good, it is difficult to increase its proportion, which greatly limits the space for cost reduction of blast furnace structure; In addition, due to the high SiO2 content of South Africa block, when the addition ratio is high, it is easy to cause the high alkalinity of sinter, which seriously affects the high-temperature performance of sinter, thus affecting the smooth running of blast furnace. At the same time, the alkali metal content of South Africa block is too high. When it is widely used, the alkali metal content in the blast furnace will be enriched and the operation of the blast furnace will be deteriorated.
 

　　2. Experimental study

　　2.1 physical and chemical properties and medium and low temperature metallurgical properties of different block ores

　　See Table 1 and table 2 for the chemical properties, reduction degree and low-temperature reduction properties of common lump ores of Anyang Iron and steel blast furnace.

　　It can be seen from table 1 and table 2 that Laos block, Roy Hill block and Newman block are high-speed iron and low silicon blocks with less harmful impurities and ideal composition; According to the determination of burning loss, Laos block, Mount Roy block and Newman block should belong to limonite block. Royshan block and Newman block have good reducibility, which is related to the fact that they belong to limonite. With the discharge of crystal water, the structure becomes loose and easy to be reduced. The addition time is conducive to the production of blast furnace; The South African block is characterized by dense texture and difficult reduction, which will affect the blast furnace production when the addition is high. The low-temperature reduction pulverization index of all block ores in the table basically reaches 85%, which is a good index.

　　2.2 high temperature free expansion rate of different block ores

　　This test simulates the volume expansion of lump ore under the heating state, and the heating test is carried out in the high temperature furnace. Since there is no relevant national or industrial standard, the test needs to be compared under the same conditions; In addition, the furnace temperature of the samples is 1000 ℃, and the heating rate is the same, but the equipment can not be filled with reducing gas, so the blast furnace atmosphere can not be simulated. Several representative samples were selected for the test. South Africa block belongs to hematite block with very dense structure and high alkali metal content; Pb block is hematite block, which is relatively loose in structure compared with South Africa block; Roy Hill block is a Limonite block with a high content of crystal water, which is generally decomposed at 300 ~ 500 ℃ and has a loose structure. The high temperature free expansion rate of different block ores is shown in Figure 1.

　　It can be seen from Figure 1 that when the temperature reaches more than 1400 ℃, the South African block shows rapid expansion, with a very high expansion rate of 67%, which is mainly related to its compact structure and high alkali metal content. Because the main component of the block is Fe2O3, its expansion phenomenon is not affected by the reducing atmosphere, that is, the actual expansion rate of the block in the blast furnace is high. Pb block and Roy Hill block did not expand during heating, and showed a shrinking trend with the increase of temperature. This is mainly related to its loose structure and composition. The analysis shows that based on the influence of lump ore expansion on the permeability of charge column in the smelting process of blast furnace, it is suggested to reasonably control the proportioning ratio of South African lump ore.