Through optimizing the batching process, innovating the charge structure, exploring the charging system, successfully applying multi-ring fabrics, studying the properties of high-aluminum slag, mastering the high-alumina smelting technology, and successfully implementing high wind temperature, high top pressure, high coal ratio, and low silicon. Smelting and other technologies have achieved good economic benefits in the case of reduced charge grades and reduced coke quality dogs.
In the selection of economic ore smelting, it must face some unfavorable factors brought about by the economic and mining industry. The high Al2O3 content in the ore is an outstanding problem.
It is generally believed that Al2O3 in the slag is within 14%, which belongs to low-alumina slag, suitable for smelting; 14% to 16% belong to Chinalco slag, smelting has certain difficulty; Al2O3 is more than 16%, it can be called high-alumina slag, smelting is very difficult . Many companies even believe that after more than 17%, they basically cannot be smelted.
Through in-depth research on the performance of high-alumina slag, basically mastered the smelting technology of high aluminum slag. The content of Al2O3 in the slag of Rigang is also the lowest at 15.5%, and the highest average is more than 18%, which belongs to the smelting of high-alumina slag.
When Al2O3 exceeds 16%, the melting temperature of the slag will rise sharply above 1500oC, and the viscosity of the slag will increase. The slag viscosity is too large and the slag is sticky, which will cause a great deal of damage in the dripping zone of the blast furnace, resulting in a drop in charge and difficulty in rising the gas. In the hearth, it is difficult to separate the slag, the retention of the slag is increased, and the hearth builds up. The appearance of the slag is crusted outside the furnace, the flowability is poor, and the organization in front of the furnace is difficult. Finally, the ability of the blast furnace to receive wind is getting worse. That caused the blast furnace to malfunction.
In view of the high viscosity and high melting temperature of high-alumina slag, the slagging system and thermal system during high-alumina slag smelting are readjusted. The slagging system is determined by the binary alkalinity as the main adjustment method, and the tribasic alkalinity is used as With reference to the general principle of the four-element alkalinity, the concept of magnesium-aluminum ratio (MgO/Al2O3,) is proposed. By adjusting the alkalinity of the acid-alkali material, with reference to the content of Al2O3 in the slag, the content of MgO in the slag is controlled by adjusting the MgO in the slag, the content of MgO is controlled with the content of Al2O3, the ratio of magnesium to aluminum is controlled, and finally the slag four alkali-free degree is controlled About 0.95 to 1.0.
The heat system is based on controlling the sensible heat of molten iron. Daily adjustments are made to control the silicon content in iron as a means to ensure that the physical temperature of molten iron is ≥l480oC, and finally the slag enthalpy is increased, the viscosity of slag is reduced, and the fluidity of slag is improved. The working status of the hearth was improved and the blast furnace was anterograde, achieving good results.
Low silicon smelting is a comprehensive technology. Due to the gradual deterioration of the original and fuel conditions of Nisshin Steel, low-silicon smelting cannot be achieved by means of improving the quality of coke and improving the grade of the furnace. For the difficulties faced, the iron and steel technicians conducted a thorough analysis and research, and were led by the iron front department. The three systems of sintering, pellets, and ironmaking were regularly held at each ten-day meeting to emphasize the importance of low-silicon smelting for ironmaking. The importance of steelmaking and the importance of lowering silicon must be addressed within the system. The level of operation should be fully ensured to ensure the realization of low silicon smelting.
The main work of the sintering plant is to stabilize the composition, increase the strength, improve the grain size, and reduce the ferrous iron.
The main measures for the ironworks are: stabilizing operation, invigorating the hearth, increasing the basicity of slag, and reducing silicon deviations. Through improved operations, the average silicon content of Nisshin Blast furnace was reduced to 0.37%, achieving low silicon smelting.
Low silicon smelting is a concrete embodiment of multi-ring fabric technology, rational slag phase selection, high top pressure, high air temperature and other technologies successfully applied, and it is inevitable after the ironmaking system is advanced.
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