On the conditions of ironmaking production in the

2022-09-21
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On the conditions of blast furnace ironmaking production

every ironmaking worker and leader hopes that the technical and economic indicators of blast furnace production in their unit are advanced, and some leaders even require that some items in the technical and economic indicators of blast furnace production should reach the top of the country. Blast furnace ironmaking technology is a major with relatively high technical content, which covers a wide range of contents, including the preparation of raw fuel for blast furnace ironmaking, production process, technology, equipment conditions, the level of blast furnace operation technology, changes in external factors (water, electricity, transportation), the level of management and the influence of pre and post production processes. Significant changes in each of the above factors will have a negative impact on blast furnace production. It should be admitted that blast furnace ironmaking production has its inherent scientific production rules, and the influence of some conditions cannot be transferred by people's consciousness. Therefore, I believe that blast furnace ironmaking is a conditional production law. Different production conditions will produce different production results. We are materialists. We should fully realize that blast furnace ironmaking production is conditional, but not only conditional, but also enterprise management. As long as we carefully study the blast furnace ironmaking that adapts to the production conditions of our enterprise, we will be able to achieve the expected goal

the proportion of the influence of various factors on technical and economic indicators in blast furnace ironmaking

the operation policy of blast furnace ironmaking is based on refined materials. The influence rate of concentrate technology level on blast furnace ironmaking production is about 70%, the influence rate of equipment is about 10%, the influence rate of blast furnace operation technology is about 10%, the influence rate of comprehensive management level is about 5%, and the influence rate of external factors is about 5%

1 connotation of blast furnace concentrate technology

blast furnace concentrate technology includes eight words: "high, ripe, clean, small, average, stable, less, good"

"high" means that the iron grade of the ore into the furnace should be high; The drum strength of sintering, pellet and coke should be high; The basicity of sinter is high (generally 1.8 ~ 2.0). High ore grade is the core of concentrate technology. For every 1% increase in ore grade, the fuel ratio of blast furnace will decrease by 1.5%, the output of blast furnace will increase by 2.5%, the amount of iron slag per ton will be reduced by 30kg, and the blast furnace is allowed to increase the injection of pulverized coal by 15kg/T

"ripe" means that the clinker ratio of blast furnace raw materials is higher. Clinker refers to sinter and pellet. With the continuous progress of blast furnace ironmaking technology, it is no longer emphasized that the clinker ratio is very high. Some enterprises have about 20% of high-grade natural lump ore into the furnace

"net" means that the particle size of < 5mm in the raw fuel into the furnace should be less than 5% of the total

"small" means that the particle size of the charged material should be small. The production practice of blast furnace ironmaking shows that the particle size of the best strength is: sintering 25 ~ 40 mm, coke 20 ~ 40 mm, and the particle size of hematite and limonite that are easy to be reduced is 8 ~ 20 mm. For small and medium-sized blast furnaces, the particle size of raw fuel is allowed to be smaller

"uniform" means that the particle size of blast furnace charging should be uniform. Graded charging with different particle sizes can reduce the filling property of the charge and improve the permeability of the charge, which will have the effect of saving coke and increasing output

"stable" means that the chemical composition and physical properties of the raw fuel entering the furnace should be stable and the fluctuation range should be small. At present, the instability of raw materials for blast furnace ironmaking in China is the main factor affecting the normal production of blast furnace. Ensuring the reasonable storage capacity of the raw material yard (ensuring that the ore proportioning ratio does not change) and establishing a neutralization mixing and homogenization yard are effective means to improve the stability of furnace charge composition

"less" refers to iron ore and less harmful impurities in coke. In particular, the contents of S and P should be strictly controlled, and the contents of en, Pb, Cu, as, K, Na, F, Ti (TiO2) and other elements should also be well controlled

"good" refers to the better metallurgical performance of iron ore. Metallurgical property refers to that the reduction degree of iron ore should be greater than 60%; The reduction pulverization rate of iron ore should be low; The load softening point of ore should be high, and the range of softening temperature should be narrow; The drop fusibility of ore should be high in temperature and narrow in range

2 attach great importance to the impact of coke quality on blast furnace ironmaking

the impact rate of coke quality changes on blast furnace ironmaking production indicators is 35%, that is, accounting for half of the impact rate of concentrate technology level. Coke plays the role of burden framework in blast furnace, and is also the reductant in smelting process. It is the main source of heat income from blast furnace ironmaking (accounting for about 60% - 80%), and the supplier of carbon in pig iron. Especially under the condition of high coal injection ratio, the significant reduction of coke ratio makes the skeleton effect of coke on the charge more obvious. At this time, the good quality of coke plays a key role in improving the permeability of charge and slag iron. For large blast furnaces, the large ore batch charging system is adopted to thicken the coke layer in the furnace (up to 300 ~ 500 mm thick), forming good coke window permeability, which plays a good role in the smooth operation of blast furnace production. Due to the high charge column and high charge compression rate of large blast furnace, the evaluation of coke quality can not only meet the requirements of M40, M10, ash, sulfur and other indicators, but also increase the requirements of coke thermal reaction performance indicators, such as post reaction strength (CSR), reactivity index (CRI) and other indicators. The quality of coke used in large blast furnaces in industrialized countries is generally better than that in China, which is one of the important reasons for the progress of blast furnace indicators abroad. M40 of coke used in foreign large blast furnaces is generally greater than 85%, M10 is less than 6.5%, ash content is less than 11.5%, and S is less than 0.55%. Baosteel has attached great importance to the high requirements for coke quality since it was put into production, so that the thermal properties of coke CSR ≥ 66%, CRI ≤ 26%. Some domestic enterprises, such as the electronic UTM experimental machine often used by Jinan experimental machine factory, with a capacity of 100 ~ 135000 lb, WISCO, Shougang, Angang and other enterprises have also strengthened the research on the quality and performance of coke. Some enterprises realize that it is obvious and worthwhile to spend more money on buying good coal and increasing the research and development of coking technology to improve the production index of blast furnace ironmaking

3 the product level adopts advanced technology, technology and equipment to achieve high efficiency of blast furnace

high efficiency of blast furnace refers to high utilization coefficient and low energy consumption. Improving the ore grade is an effective means to achieve high utilization factor. Realizing a reasonable charge structure can improve the ore grade. At present, the proportion of pellets in the burden structure of blast furnace ironmaking in China is low (the average of national key iron and steel enterprises is 11%). The iron grade of pellet can reach 60% - 66%, while the sinter grade is above 58%, which is a high level. Therefore, China should strive to improve the pellet production capacity and increase the pellet ratio to more than 20%. It is suggested to actively adopt belt calciner and grate rotary kiln production equipment to produce pellets. The above is that when we install the fixture of the universal experimental machine, the pellet quality produced by the equipment is better than that of the shaft furnace

we should vigorously promote the use of bell less furnace top equipment, achieve reasonable distribution, and improve the utilization rate of CO2 in gas (the CO2 content in gas is increased by 0.5%, which can reduce fuel consumption by 10kg/t), so as to reduce fuel consumption; It can also effectively control the edge development of gas flow, and then improve the service life of blast furnace. China has successfully developed various forms of bell less top equipment, which has been applied to large blast furnaces, and the cost is more than 50% lower than that of the introduction. We should vigorously promote domestic equipment and support the development of China's manufacturing industry

actively promote the blast furnace top gas differential pressure power generation technology (TRT), which can recover 30% of the blast furnace blower energy and reduce the energy consumption of ironmaking process by 11 ~ 18kgce/T. The blast furnace with the top gas pressure greater than 120kPa should be equipped with TRT device, and its power generation varies with the top gas pressure. Generally, 20 ~ 40 kwh can be generated per ton of pig iron. Using dry dedusting can increase power generation by about 30%. As the gas temperature increases by 10 ℃, the output of the power turbine can be increased by 3%

pulverized coal injection into blast furnace is the central link of structural adjustment of ironmaking system, and it is also the general trend of ironmaking technology development at home and abroad. Pulverized coal injection into blast furnace can not only save coke and alleviate the contradiction of coke shortage in China, but also reduce environmental pollution caused by coke production process. At the same time, it can also save energy (the energy consumption of coking process is 144.4kgce/t, and the energy consumption of pulverized coal process is 20 ~ 35kgce/t) and reduce iron making cost (the price of 1 ton of pulverized coal is about 500 yuan lower than that of 1 ton of coke)

the quality requirements of raw materials and fuels for large blast furnaces are higher than those for small and medium blast furnaces

the practice of blast furnace ironmaking at home and abroad shows that the charging column of large blast furnaces is high, the compression rate of charging is high, the stacking ratio is large, and the permeability of charging is poor, which will cause instability of gas flow movement. In order to make up for this deficiency, the charge quality of large blast furnaces is required to be higher than that of medium and small blast furnaces. In previous years, some enterprises have expanded blast furnace capacity or built new blast furnaces, but the quality of raw materials and fuels for ironmaking has not been improved, resulting in the backward phenomenon of technical and economic indicators of blast furnace ironmaking

1 the raw fuel quality of small and medium-sized blast furnaces is higher than that of large blast furnaces

according to statistics, in the first half of 2005, the raw fuel quality of a batch of small and medium-sized blast furnaces in China was higher than that of large blast furnaces. The relevant situations are as follows:

the enterprises with coke ash less than 12.5% include Changzhi (11.07), xinlingang (12.09), Hangang (83.36), Tiantie (83.27), Shaoguan (82.50), Sanming (82.14); Enterprises with M10 less than 7% include Xing steel (5.40), Kunming Steel (5.98), Xinlin steel (6.11), Pingxiang (6.14), Chuanwei (6.41), Suzhou steel (6.66), Lianyuan Steel (6.76), Changzhi (6.78), Xuzhou (6.80), Tiantie (6.80), Xinxing cast pipe (6.98)

enterprises with iron grade of sinter greater than 57% include Xuzhou (58.81), Xinxing cast pipe (58.46), Sanming (57.57), Chenggang (57.38), Anyang (57.19), Laiwu (57.25), xinlingang (57.01); Enterprises with a Jinggu index greater than 80% include Chuanwei (86.26), Tangshan Baoye (88.53), Guanggang (83.25), Suzhou iron and steel (81.87), Tangshan Iron and steel (81.43), Nanjing (80.83) and Chenggang (80.04)

after a batch of small and medium-sized blast furnaces in this enterprise used high-quality iron making raw fuels, the technical and economic indicators of blast furnaces have been comprehensively improved. According to statistics, there were not many waste plastic recycling plants in China in 2004, and more than 80 small and medium-sized blast furnaces had a utilization coefficient of 3.0t/m3 Above D, the coke ratio of 13 blast furnaces is lower than 400kg/t, and that of 51 blast furnaces is lower than 450kg/T

2 large blast furnaces with different volumes have different requirements for the quality of raw fuel.

the larger the blast furnace volume, the higher the requirements for the quality of raw fuel. Now, when TISCO, Benxi Steel, Shougang and other units plan to build new blast furnaces with a volume of more than 4000m3, they should formulate scientific, reasonable and practical quality standards for raw materials and fuels for blast furnace ironmaking in combination with the actual situation of the enterprise. According to the production practice of large-scale blast furnaces abroad, I put forward the quality requirements of raw materials and fuels for blast furnaces with different volumes. See table 1-4 for details. Table 1 high basicity sinter quality

Table 2 pellet quality

Table 3 lump ore quality into the furnace

Table 4 coke quality requirements

according to the actual situation of each enterprise, a detailed technical and economic feasibility analysis should be carried out for different raw material and fuel quality, and the raw material preparation and technical and economic indicators of blast furnace production should also be put together for comprehensive consideration. High quality coke is widely used in large blast furnaces abroad, but the cost of considering this quality coke will be high, which is certainly beneficial in the overall economy. Enterprises that own and plan to build large blast furnaces should seriously deal with the quality of raw materials and fuels used for ironmaking, in order to achieve ideal technical and economic indicators for blast furnace production. (end)

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