Relationship between smelting index and grade of blast furnace

The selected grade of ore is improved, the amount of smelting slag is reduced, the coke ratio is reduced, and the output is increased. The effect is obvious.
Theoretical formula for calculating the amount of iron smelting furnace slag is:

Where G _slag --- smelting the amount of slag per ton of pig iron, kg / t;
Per ton of pig iron smelting P --- _burning sinter consumption, kg / t;
(SiO ₂ + Al ₂ O ₃ + CaO + MgO) _ore - the corresponding composition of sinter, %;
————The limestone added to each ton of pig iron blast furnace is the most (all of the self-fluxing sinter is zero when entering the furnace), kg/t;
(SiO ₂ + Al ₂ O ₃ + CaO + MgO) _melting - the corresponding composition in limestone, %;
C———the ironmaking coke ratio kg/t;
A _{coke ash} - coke ash, %;
[Si]———the amount of silicon in pig iron, %;
δ———— Consider the coefficient of FeO, MnO, etc. in the slag, generally taking 1.02.
After the grade of the ore in the furnace is increased, the ore consumption per ton of iron is reduced, the content of slag elements in the ore is reduced, and the coke consumption is the most reduced. These factors all reduce the slag amount of the blast furnace.
The results calculated using equation (1) are similar to those of actual production indicators.
In the case of an iron and steel plant in Benxi Iron and Steel, the grade of the furnace is changed by 1%, and the amount of slag is changed by 30 to 33 kg.
Many units have done a lot of work on the change in the amount of iron slag with the grade.
The change in slag amount is related to ore composition and smelting conditions. When the ore contains high silicon and the grade is low, the amount of slag changes greatly, and vice versa. Although the above calculations are somewhat different, they are relatively close. The grade of Anshan-type ore concentrate is increased by 1%, the amount of slag is reduced by 50-60kg/(t• iron); the grade of sintered ore is increased by 1%, and the amount of slag is reduced by 30~35kg/(t• iron).
The relationship between ironmaking coke ratio and blast furnace utilization coefficient with ore grade has been clearly reflected in the production practice of Angang, Benxi Steel and Shougang's various factories for many years. [next]
Figure 1 reflects the change in the coke ratio and utilization factor of Shougang Iron Works with grade. During this period, the grade of the ore in the furnace was changed significantly, especially after 1977, the grade of the blast furnace was significantly improved.

The practice of Shougang blast furnace for many years shows that the relationship between ironmaking index and the grade of the furnace is very close. The coefficient increases as the grade increases, and the coke ratio decreases as the grade increases. There are many reasons for the improvement of the indicator, but the ore grade plays an important role. In order to eliminate the interference of other factors, the No. 4 blast furnace (no major changes in equipment, single smelting variety) was compared on a quarterly basis during the period from 1976 to the first quarter of 1981, and the temperature was tempered, smelting intensity, The factors of top pressure, clinker ratio, amount of limestone, amount of broken iron, silicon content of pig iron, coke ash and other factors affecting the change of coke ratio were corrected, and the relationship between corrected coke ratio (y) and grade of ore (x) was obtained. for:
y=898.49-7.86x[next]
That is, the grade of the ore in the furnace is increased by 1%, and the coke ratio is reduced by 7.86kg. The corrected result is shown in Figure 2.

Shougang also analyzed the influence of increasing ore grade on sintering and ironmaking indexes, and selected the No. 4 furnace from January 1978 to October 1979 and the fourth quarter of 1977 (base period) to compare and influence The factors of coke ratio and yield were corrected. According to the results of the study, the iron content of the ore in the furnace is from 55.5% to 59%, and the iron content of the ore in the average increase of 1% is:
(1) The coke ratio decreased with the increase of iron content in the furnace ore, with an average decrease of 1.681%. However, the decrease of the coke ratio gradually decreased from 1.973% to 1.394%.
(2) The output of blast furnace increased with the increase of iron content in the furnace ore, with an average increase of 2.79%. However, the increase of output gradually decreased from 3.645% to 1.932%.
(3) The amount of iron slag decreased with the increase of iron content in the furnace ore, with an average decrease of 8.15%. However, the decrease gradually decreased from 9.46% to 7.07%. [next]

Figure 3 shows the production data of the second iron and steel plant of Benxi Iron and Steel Co., Ltd. from 1975 to the first half of 1980. The ore grade of the plant after 1975 has increased year by year, and the coke ratio and utilization factor have improved year by year. They found that the grade of sinter grade was increased by 1%, the coke ratio was decreased by 1.8%, and the smelting strength was increased by 2.5%. Among the factors of reducing coke ratio, the ore grade played a major role.
In the selection of the better production period of No.5 blast furnace, in the defocusing factor, the grade of ore increased by 51kg, the powder of the furnace was reduced by 10kg, the silicon content of pig iron was reduced by 8kg, and the coke ratio of wind temperature decreased by 8kg. The quality deterioration increases the coke ratio by 28kg.
The improvement of the grade of Angang Iron and Steel concentrate is not large, which is reflected in the change of ironmaking indicators over the years. The comparative analysis of the indicators of the Anshan Iron and Steel Research Institute in 1979 and the 1978 indicators of the Angang Ironmaking Plant concluded that when the concentrate grade changes between 63.5 and 66.5%, the concentrate grade increases by 1%, which can make the grade of sinter. Increase by 1.7%, iron-fuel ratio decreased by 2.18%, fuel consumption of 12.7kg per ton of iron, iron production increased by 3.94%, consumption of iron raw materials per ton decreased by 68kg, iron slag volume decreased by 63kg. 1% can reduce the coke ratio by 1.28% and the yield by 2.32%.
From the above, the changes in the actual production indicators of Angang, Benxi Steel and Shougang, and the statistical results show that the influence of ore grade on the smelting index of blast furnace is obvious. As for the quantitative relationship between them, the mine is different, because of the furnace. Different, it can't be the same level. In studying their quantitative relationships, it is necessary to distinguish between the two different concepts of ore dressing grade and entry grade, as they are not equal. In view of the complexity of blast furnace smelting indicators, it is difficult to accurately find out how much each ore has a significant impact on the blast furnace due to changes in grade. However, these indicators are indispensable for evaluating the depth of ore selection. However, according to the results of domestic and foreign research, when the concentrate is sintered into the furnace, it can be concluded that the concentrate grade is increased by 1%, the coke ratio can be reduced by about 2%, the yield is increased by about 3%, and the grade of sinter is improved. 1% can reduce the coke ratio by about 1.5% and the yield by about 2 to 2.5%.

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