Improve concentrate grade iron smelting benefit analysis from the point of view of production and operation, mainly in the following areas:
(1) The mine consumption is reduced and the raw material cost is saved.
Consumption per ton of pig iron and sinter ore grade of sinter, pig iron content, sintering and smelting process of metal loss related to the following formula:
Where P --- tonne pig burn demand sinter amount, t / t;
Fe raw --- iron content of pig iron, %;
Fe burning - sinter grade, %;
K———Sintering, metal loss coefficient in the smelting process, %. (including recoverable and non-recyclable parts, generally 5%)
If the grade of concentrate is increased from 65% to 66% and the grade of sinter is increased from 54% to 55.7%, the change in the amount of sinter produced per ton of raw iron is (the composition of pig iron is calculated at 94.5%):
According to the cost of 70 yuan per ton of sinter, the cost of raw materials is saved at 3.92 yuan.
(2) Reduce the coke ratio and reduce the fuel cost.
According to the concentrate grade increased by 1%, the coke ratio is 2%, and the comprehensive fuel ratio is 600kg, which will save 12kg of coke . The cost per ton of coke is 120 yuan, which can save fuel costs:
0.012 × 120 = 1.44 yuan (3) The output is increased, and the smelting and processing costs are reduced.
The smelting and processing costs include wind, water, electricity, gas (steam) consumed by the production, wages and surcharges for production workers, minor repair and maintenance of fixed assets, depreciation expenses, workshop expenses, and enterprise management fees.
In the smelting and processing fee, some expenses are basically not increased or decreased with the increase or decrease of production. For a specific enterprise, the total cost is unchanged (or basically unchanged) under certain conditions, and it is called “fixed costâ€, such as wages and depreciation. , workshop expenses, business management fees, etc. For unit pig iron, the higher the output, the smaller the “fixed cost†per ton of pig iron.
Conversely, some of the smelting and processing costs increase with the increase in output, such as auxiliary materials (gun mud, river sand, refractory materials) consumed before the furnace, and consumable spare parts, which are “variable expensesâ€. The total variable cost varies with the output, but the variable cost allocated to the unit pig iron is basically unchanged. [next]
The Soviet scholar H. Ji Barnei proposed that the calculation formula for the change of processing cost per unit product cost due to the improvement of equipment capacity is:
Where u 0 ——— processing fee per unit of product under the original production capacity;
c 0 ———The original production capacity of the equipment;
c 1 ———the changed production capacity;
Æ’ change --- processing fees in the proportion of variable costs;
--- Æ’ fees solid fixed cost ratio;
u 1 ———Unit product processing fee after changing ability.
It is believed that 100% of steam, water, depreciation, wages, and whole plant expenses in ironmaking production are fixed costs; 50% of replacement equipment wear costs are fixed costs; 90% of minor repair and fixed assets maintenance costs are fixed costs; other workshops 80% of the fee is a flat fee.
In fact, fixed costs and variable expenses are relative. It is difficult to accurately find the ratio of fixed to variable expenses in each cost. When using this formula to calculate the impact of blast furnace output increase on smelting processing costs, statistics can be used. The method calculates the total proportion of the fixed costs in the smelting processing fee, and does not need to be calculated item by item, so as to avoid being too cumbersome.
Calculate the relationship between the smelting processing fee and the blast furnace utilization factor adjusted by the same price for the Shougang Ironmaking Plant from 1976 to 1979, and calculate the relative production cost when compared with the fixed cost ratio of 60%. The impact is consistent.
For factories with low labor productivity and high plant-wide costs, the proportion of fixed costs is even higher.
The smelting processing fee adjusted by Shougang Iron and Steel Plant for the same price (1979 price) for each quarter from 1976 to 1979 is shown in Figure 1.
Relationship y=23.97-4.75x
Correlation coefficient Ï…=0.94
(where y smelting processing fee, x blast furnace utilization factor)
The smelting and processing fees counted above do not include the intermediate repair fee and oxygen blowing fee. According to the statistics from 5 years from 1976 to 1980, the average annual prepayment fee is 4.64 million yuan. The fee is a fixed fee and should be apportioned according to different output [464 million yuan (4139 × 355 × coefficient)].
When the concentrate grade is increased from 65% to 66%, it is assumed that the blast furnace utilization factor is increased from 1.92 to 1.98, and the smelting processing fee before the grade is increased by 25.00 yuan/t, the smelting processing fee after the grade is improved is:
The difference between the smelting and processing costs before and after the improvement of grade is 0.45 yuan.
The above three fees total:
3.92+1.44+0.45=5.81 yuan From the perspective of iron and steel management, the savings of iron and steel operating expenses after the improvement of grades are calculated. In fact, the benefits are not limited to the above. The above calculations also did not include the increase in ironmaking profits due to increased production. The conditions of each plant are different, the impact value of the ore grade on the original and fuel is increased, and the price of each plant is different. Therefore, the economic benefit of improving the grade must be analyzed in detail according to the specific conditions of the enterprise. Shougang and Anshan Iron and Steel Institute of Economic Research Dashi beneficiation plant with the plant actually analyzed. [next]
In 1979, the Anshan Iron and Steel Economic Research Institute combined with the fine sieving and re-grinding project of the Dagushan Concentrator to analyze the benefits of the Angang Iron and Steel Plant when the concentrate grade increased by 1%:
1) Concentrate grade increased by 1%, fuel ratio decreased by 2.18%
The concentrate grade increased by 1%, which can increase the grade of sinter by 1.7%, the fuel ratio by 2.18%, and the fuel saved by 12.7kg per ton of iron. If the fuel consumption in 1978 constitutes a fuel saving of 0.79 yuan per ton of pig iron, of which coke 10.9 The kg is 0.71 yuan, the oil 1kg is 0.06 yuan, and the coal 0.8kg is 0.02 yuan.
The concentrate grade is increased by 1%, and the annual output of ironmaking is calculated by 6.4 million tons of iron. The annual fuel saving is 81,000 tons, including 70,000 tons of coke, 0.6 million tons of heavy oil, and 0.5 million tons of anthracite. The fuel cost is reduced by 5.06 million yuan.
2) Concentrate grade increased by 1%, consumption of raw iron per ton decreased by 68kg
According to the theoretical calculation, the grade of the furnace is increased by 1%, the consumption of iron raw materials per ton is reduced by 40kg. The grade of concentrate is increased by 1%, the grade of sinter can be increased by 1.7%, the consumption of raw iron raw material per ton is reduced by 68kg. The price is priced at 31.5 yuan per ton of sinter. (The company's internal planned price before the quality price is not implemented), the raw material cost per ton of raw iron decreased by 2.14 yuan. With an annual output of 6.4 million tons of pig iron, the annual raw material cost can be saved by 137.07 million yuan. Sintered ore transport can save 435,000 tons.
3) 1% increase in concentrate grade and 3.94% increase in iron production
The grade of concentrate is increased by 1%, the output of pig iron is increased by 3.94%, the annual output of ironmaking is calculated by 6.4 million tons, and the annual iron increase is 252,000 tons. The fixed cost per ton of pig iron due to increased production (including wages, depreciation, workshop expenses) ) Decreased by 0.2 yuan, and a fixed cost of 1.519 million yuan can be saved throughout the year.
4) 1% increase in concentrate grade, which can reduce the amount of pig iron slag per ton by 63%
According to the production practice and theoretical calculation, the grade of the furnace is increased by 1%, the slag volume can be reduced by 37.5kg, the grade of the concentrate is increased by 1%, and the slag volume is decreased by 63kg. With an annual output of 6.4 million tons of iron, the annual slag reduction is 40.3. 10,000 tons, saving slag tank turnover 13200 times / can. The cost is reduced by 220,000 yuan (including transportation and overturning fees).
Based on the above four factors, when the concentrate grade is increased by 1%, Angang's 6.4 million tons of iron can reduce the ironmaking cost by 20.49 million yuan.
In 1980, the Shougang Dashihe Concentrator edited the “Application of Total Quality Management in Mineral Processing†to compare the changes in ore dressing indicators in 1978 and 1977 and the impact on blast furnace production. The comparison results are:
1) In 1977, the grade of concentrate was 64.45% (mining company); in 1978, the grade of concentrate was 67.63% (the third quarter of the mining company); the grade of concentrate was increased by 3.18%, and the grade of SiO2 was decreased by 3.2%.
2) The grade of sintered ore increased from 54.29% to 58.37%, an increase of 4.08%; the sinter SiO 2 decreased from 9.9% to 6.5%.
3) The coking ratio of ironmaking into furnace is reduced from 536kg to 450kg, which is reduced by 86kg; the comprehensive coke ratio is reduced from 614kg to 555kg, which is reduced by 59kg; the defocusing is mainly caused by the increase of concentrate grade, about 50kg, saving coke 11.3 a year. Wan t.
4) The average daily output of the blast furnace increased from 5212t to 6502t, an increase of 1290t/d. The increase in concentrate grade can increase 9.4%, and the annual increase of iron is 200,000 tons.
5) The amount of limestone is less, and the amount of sinter ash per ton is less than 50kg, which can save 240,000 tons of limestone in one year.
6) The ore consumption is reduced, the blast furnace ton iron ore consumption is reduced from 1804kg to 1672kg, and the low is 132kg. The annual consumption of ore can be reduced by 300,000 tons.
7) The amount of blast furnace slag is reduced, the amount of iron slag per ton is reduced from 522kg to 369kg, and 153kg.
8) Reduce the amount of transportation. As the concentrate grade increases the SiO 2 content, the annual output of concentrate powder is 3.2 million tons, which can reduce the amount of SiO 2 by 102,000 tons. It can reduce the amount of limestone by 240,000 tons. One year saves 113,700 tons of coke and consumes 230,000 less coal. t. The above three items totaled 570,000 tons.
9) The cost of ironmaking can save 13 million yuan from raw materials, fuel and transportation in one year, and reduce the cost of pig iron per ton by 5.8 yuan.
10) Due to the decrease in raw material and flux consumption, the amount of blast furnace slag is reduced, and the annual transportation volume can be reduced by 2 million tons.
From the above analysis of Angang and Shougang, it is obvious that the benefits of improving the concentrate grade to smelting are significant. Summarizing the contribution of the country to the steel industry in the past decade or so due to the improvement of concentrate grades, it is even more impressive.
In 1986, the national key selection plant produced 3,446,800 tons of iron ore concentrate, of which the output of magnetic separation concentrate was 300,150,800 tons, accounting for 87.08%. In 1986, the national key selection of magnet concentrate grade was 66.41%. 10 years ago from 1975 to 1977 The average grade is 60.48%, an increase of 5.93%. According to the consumption of 1.450t per ton of pig iron concentrate, the key selection of magnetic separation concentrate can produce 20.7 million tons of iron. This part of the magnetic concentrate is smelted due to the grade increase of 5.93%. The benefits are:
According to the concentrate grade increased by 1%, the coke is reduced by 2%, and the iron consumption per ton of iron is 600kg. The annual savings of coke is 1.47 million tons, the original coal is 3.68 million tons, the coke price is 120 yuan/t, and the annual coke cost is 176.4 million yuan. ;
According to the concentrate grade increased by 1%, the amount of sintered limestone reduced by 25kg, the annual saving of limestone is 4.9 million tons. The cost per ton of limestone is 10 yuan, and the annual cost of saving limestone is 49 million yuan;
According to the increase of 1% in concentrate grade and 50kg of blast furnace slag, the amount of waste residue can be reduced by 6.14 million tons throughout the year;
In the whole year, the transportation volume of iron, flux, coal char and waste residue can be reduced by more than 20 million tons.
No need to calculate, only a few big accounts can be seen, how important it is to select ore. For more than a decade, the state has spent a small amount of money on ore selection, and has achieved great results. The breakthrough and promotion of selected technologies have made important contributions to the development of China's steel industry. The ore selection improves the grade of concentrate and prepares high-quality charge for the blast furnace. This technical direction is to be adhered to. Especially in China, where there is a shortage of natural rich ore, and most of the ore needs mineral processing, only the selection of ore can promote the virtuous cycle of the steel industry.
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