1 Treatment of dust and sludge with high harmful impurities generated in iron and steel enterprises
Most enterprises use dust and sludge with high harmful impurities in the sintering plant, which leads to the enrichment of harmful impurities, which is not conducive to blast furnace production. The construction of rotary hearth furnace can remove harmful impurities in the charge. However, the reduction degree of iron (direct reduced iron) is less than 90% and the FeO content is high. Therefore, it can only be used for blast furnace ironmaking and cannot be used as raw material for electric furnace. The cost of constructing a rotary hearth furnace is relatively high. The 7 rotary hearth furnace production lines that have been constructed have not reached the ideal state, and no new rotary hearth furnaces have been built abroad.
For dust and sludge with high harmful impurities, such as blast furnace bag dust and sintering machine head dust, it is recommended to add lime to them, mix, pelletize, dry, and then use in converter; this can cut off the enrichment cycle chain of harmful impurities.

2 Technical analysis of blast furnace injection of coke oven gas
Blast furnace injection of coke oven gas can reduce the coke ratio, but the effect is not ideal. Coke oven gas contains high methane content (for direct reduction of iron ore, gas reforming is required to achieve CO+H2 content greater than 90%), and it is a good gas source for indirect reduction of iron ore; however, coke oven gas injected from blast furnace tuyere Coal gas can only play a role in combustion, and cannot perform indirect reduction of iron ore (indirect reduction of iron ore is an exothermic reaction). If the gas is injected from the furnace body, the gas cannot be burned with oxygen, and the indirect reduction of iron ore can be carried out. In doing so, the economic benefits are high.

3 High Al2O3 content iron ore smelting technology
When the Al2O3 content of iron ore used in blast furnace ironmaking is high, MgO needs to be added to improve the fluidity and desulfurization efficiency of the slag. Generally, it is scientific to mix iron ore with high Al2O3 content with MgO to achieve a slag with a magnesium-aluminum ratio of 0.5. However, after using low MgO, the smelting interval of the slag phase diagram is very narrow. If the quality of the charge is very stable, the smelting can still be carried forward; however, if the quality of the charge fluctuates greatly, short slag is likely to occur, resulting in increased slag viscosity and poor fluidity. , the hearth freezes. It is recommended that enterprises with large fluctuations in charge quality adopt a slag operation system with a magnesium-aluminum ratio greater than 0.5.
Most companies add MgO to sinter, and the phenomenon that the content of MgO in sinter exceeds 2.0%. This will reduce the quality of sinter and increase the pulverization rate. To solve this problem, it is recommended not to add MgO to the sinter, but to add it to the pellet, or directly to the blast furnace.
The low MgO content of the slag is conducive to reducing the amount of slag, improving the gas permeability of the charge and reducing the fuel ratio, and also reducing the production cost. The MgO content in the sinter is increased by 1%, the iron grade is decreased by 1%, and the amount of blast furnace slag is increased by 10%. Therefore, MgO should be scientifically used according to specific production conditions.

4 Change the operation concept and operate the blast furnace scientifically
At present, a batch of small and medium blast furnaces operate with large air volume and high smelting intensity, sacrificing fuel ratio to achieve high output. Typically, the utilization factor is equal to the smelting intensity divided by the fuel ratio. The scientific blast furnace operation policy is to obtain a high utilization factor by reducing the fuel ratio. The good smelting strength of blast furnace is about 1.2t/(m3·d). Above this value, the blast furnace output will increase, but the fuel ratio will increase and the cost will increase. Some medium and small blast furnaces use large air volume and high smelting intensity to achieve high utilization factor, which is an incorrect operation method. The high air consumption per ton of iron leads to a high fuel ratio (0.93m3 of oxygen and about 4.42m3 of air are required to burn 1kg of carbon), which also causes high energy consumption in the ironmaking process (blasting energy accounts for about 4.5% of the total energy consumption of ironmaking) . Therefore, moderate smelting intensity can obtain good indicators of iron making. Blast furnaces in industrially developed countries are operated with medium smelting intensity and medium utilization factor, so as to obtain low fuel ratio and achieve long life of blast furnace.

5 Scientific evaluation of tamping coke
The stomata of the tamping coke are oblate, and there are many cecal pores, and the density is high, but the coke index obtained by the test is worse than the coke of the top-loading coke, which is an illusion (compared with the top-loading coke, multiplied by a factor of 0.85%); The combustibility of stamped coke is not as good as that of top-loaded coke, resulting in a decrease in CO content in blast furnace gas, a decrease in indirect reduction of ore, an increase in fuel ratio, and a decrease in output. Tamping coke is not resistant to alkali metal corrosion and is easy to powder. Blast furnace operation is greatly negatively affected by the use of charges with high levels of harmful impurities. The blast furnace below 1000m3 uses tamping coke, which has no great influence on the operation of the blast furnace. However, using tamping coke in blast furnaces above 3000m3, there will be some problems in operation, and the technical and economic indicators are not good.
The tamping coke is produced by reducing the ratio of main coking coal to reduce the cost. The tamping coke has high density, many cecum pores and poor flammability.
Large-scale blast furnaces abroad basically do not use tamping coke. Lianyuan 3200m3 blast furnace uses tamping coke, which is produced by the company's internal coking plant. The main coking coal for coking and blending is the same as top-loading coke, so the quality of tamping coke has been improved. In addition, it is recommended not to use tamping coke when the blast furnace starts or stops, so as to quickly resume production.

6 Improving the ratio of pellets in blast furnace charge is the development direction of ironmaking technology
Improving the ratio of pellets in blast furnace charge has the following advantages, which is the development direction of ironmaking technology.
1) Increasing the ratio of pellets in the iron-making furnace charge can effectively promote the improvement of the iron-containing grade of the iron-making furnace ore.
In general, the iron grade of pellets is 7-8% higher than that of sintered ore, so the blast furnace mostly uses pellets, which can effectively improve the iron content of the ore into the furnace.
2) The iron grade of the charging charge for ironmaking is increased, which can reduce the fuel ratio and increase the output.
Usually, the iron content of the ore entering the furnace is increased by 1%, the fuel ratio of the blast furnace is decreased by 1.5%, the output of pig iron is increased by 2.5%, and the amount of slag is decreased by 1.5%. If 100% of the iron is made of pellets, compared with the use of sinter, the fuel ratio will drop by 11.52%, and the output of pig iron will increase by 19.2%, which is a considerable benefit.
3) Increasing the ratio of iron-making furnace charge pellets can reduce the energy of the iron-making system.
According to statistics, in 2018, the energy consumption of the pelletizing process of key iron and steel enterprises was 25.36 kgce/t, and the energy consumption of the sintering process was 48.60 kgce/t; the energy consumption of the pelletizing process was 23.24 kgce/t lower than that of the sintering process. If one ton of pellets is used instead of one ton of sintered ore to make iron, the energy consumption of the iron-making system will be reduced by 23.24kgce.
4) Increasing the ratio of iron-making furnace charge pellets can reduce pollutant emissions.
Sintering production produces a large amount of harmful substances such as SO2, NOX, dioxin, and dust. In 2012, the state promulgated the standard for comprehensive treatment of sintering flue gas (GB28662-2012 "Steel Sintering and Pellet Industry Air Pollutant Emission Standard"), and the indicators are basically in line with international standards. This increases the cost of environmental protection management of iron and steel enterprises, and increases the environmental protection investment and operating costs of enterprises. At present, the cost of environmental protection treatment per ton of sintered ore is about 50 yuan. If pellets are used instead of sintering, the cost of pollutant treatment can be greatly reduced. The production of pellets uses natural gas instead of coal. The exhaust gas emissions of pellets are half lower than that of sintering. The content of dioxin, SO2, NOX, etc. in the exhaust gas of pellets is less than that of sintering. The environmental protection treatment is simple and easy, and the factory is clean.