Measures for improving manganese recovery rate by smelting ferromanganese in blast furnace

Although manganese blast furnace iron smelting iron and have much in common. But it has its own characteristics. The biggest difference is that manganese is harder to reduce than iron. The recovery rate of manganese can fluctuate in the range of 60 to 90%, unlike the iron smelting, almost all of the iron is reduced to the product. According to this feature, it is decided that increasing the recovery rate of manganese when smelting ferromanganese is important for production, quality, consumption and cost. Therefore, increasing manganese recovery is an important technical policy for ferromanganese production.

First, the importance of improving manganese recovery rate

(1) Reduce manganese ore consumption

Increasing the recovery rate of manganese can greatly reduce the consumption of manganese ore and save valuable manganese ore resources, which is a major feature of smelting ferromanganese in blast furnace. Without the use of metal appendages, blast furnace smelting iron ore ratio depends on the average grade of ore furnace, and ferromanganese ore recovery ratio depends on the average manganese content into the furnace and manganese. Calculated as follows:

(1)

Q mine-mine ratio, kg/t

Mn of 650-standard ferromanganese, kg/t

M _n - average manganese content of furnace ore, %

η _Mn - manganese recovery, %

In 1990, Xinyu Iron and Steel Plant received an average of 26.92% of ancient manganese. The recovery rate of manganese is 85.53% on average. The average recovery rate in the early 1960s was 65%. According to the formula (1), due to the increase of manganese recovery rate, the unit product can reduce the manganese ore consumption by 892kg/t, which is equivalent to 1% of the manganese recovery rate. It can reduce the consumption of manganese ore by 44.6kg/t; according to the annual output of 170,000 tons, it can save 150,600 tons of manganese ore.

(two) reduce the focus ratio

Increasing the recovery rate of manganese can greatly reduce the coke ratio of the furnace, which is another feature distinguishing the ferromanganese blast furnace from the pig iron blast furnace. When metal additions are not used, the pig iron coke ratio depends only on coke load and ore grade; while the ferromanganese coke ratio depends on coke loading, ore grade and manganese recovery. Its calculation formula is as follows:

(2)

K-into coke ratio, kg/t

Q-coke load, t/t

In 1990, the average load of the blast furnace of Xinyu Steel Plant was 1.607t/t, and other conditions were the same as before, calculated according to formula (2). In 1990, the coke ratio was 1758kg/t; if the average manganese recovery rate was 65% at the beginning of the 1960s, the coke ratio was 2312kg/t. Only a higher recovery rate reduced the coke ratio by 554kg/t. Under the existing raw material conditions, the recovery rate is increased by 1%. Reduce the coke ratio by 27.7kg/t.

(3) Increase production

The calculation formula for blast furnace output is as follows:

(3)

Substituting (2) into the available ferromanganese blast furnace production formula:

(4)

Qy-year production, t/y

365-calendar days, d/y

V-blast furnace effective volume, m ³

I-smelting strength, t/m ³ ·d

Η-wind rate, %

In 1990, the blast furnace wind rate was 1.72%. The smelting strength is 1.085t/m ³ ·d other conditions are the same as before. According to (3), the recovery rate is 41.51% higher than the increase in the early 1960s by 41294t/d. Equivalent to 1% increase in recovery rate, 575.5% increase in blast furnace production.

(4) Improve the quality of ferromanganese

Increasing the recovery rate of manganese, that is, increasing the amount of manganese and manganese in the same raw materials, reducing the amount of sound phosphorus , thereby improving the quality of ferromanganese. In 1990, the average ferromanganese content of the plant contained [Mn]=67.28%, [P]=0.454%. If calculated at the 65% recovery rate in the early 1960s, the ferromanganese composition will become [Mn]=62.35%, [P] =0.570%.

(5) Increase efficiency

Calculated as described above, as the recovery rate increases,

Compared with the early 1960s, with an annual output of 170,000 tons of ferromanganese, the current average price of manganese ore is 421 yuan / t (including imported manganese ore), and the focal spot is 244 yuan / t. The benefits are:

a year, the total cost of coke reduction: 17 × 0.654 × 244 = 22.98 million

b Annual saving of manganese ore to reduce the cost of the total vehicle: 15.16 × 421 = 63.82 million yuan

In total, the total cost of reduction is reduced by 86.82 million yuan/a, which is equivalent to a recovery rate of 1% per increase, and the cost is reduced by 25.53 yuan/t. Due to the increase of recovery rate, the impact of raw material price increase factors on business operation efficiency is overcome. To make the company stand firm.

Among the manganese ore resources in China, there are many poor manganese ore and less rich ore. With the development of the iron and steel industry, the contradiction between supply and demand of manganese ore is prominent, and the ore used in blast furnaces is depleted year by year. Increasing the recovery rate of manganese can greatly reduce the consumption of manganese ore, which can be contradicted to the supply and demand of manganese ore to a certain extent.

Second, the main measures to improve manganese recovery rate

In order to improve the recovery rate of manganese, it is necessary to clarify the distribution of manganese in iron, slag and furnace dust when smelting ferromanganese in blast furnace, and to find out the whereabouts of manganese loss in the blast furnace production process, so as to take technical countermeasures (Table 1).

Table 1 August 21-31, 1964 1 ^#炉锰的平衡

Table 1 shows that the chemical loss lost to the slag in the form of Mn accounts for 16.80% of the total manganese in the furnace, accounting for 60.27% of the total loss, followed by the furnace top loss. This points the way for the development of measures to increase manganese recovery.

(1) Reducing MnO in slag

The chemical loss of manganese in the slag can be calculated by the following formula:

(5)

Chemical loss of Mn in the slag in the formula, kg/t

O slag - slag amount, kg / t

55 and 71- are the molecular weights of Mn and MnO, respectively

It can be seen from the above formula that the chemical loss of manganese in the slag is proportional to the amount of slag and MnO in the slag. The poorer the ore and the larger the slag, the lower the MnO in the slag. Main measures:

1. Improve the slag selection system. At present, the MnO in the slag of the factory has dropped to the level of 4 to 5%, which is a leading position at home and abroad. The changes of slag CaO/SiO2, MgO and MnO in each period are shown in Table 2.

Table 2 Variations of slag CaO/SiO ₂ , MgO, MnO

2. Improve the structure of the charge. The use of quicklime as a solvent (since 1973) produces high CaO/SiO ₂ and high MgO manganese sinter (since 1980).

The main function of the above measures is to improve the sloping condition of the furnace and improve the slag forming conditions in the furnace to promote the reduction of manganese.

3. Increase the temperature of the hearth. Manganese is directly reduced in the blast furnace, which consumes a large amount of heat and needs to maintain sufficient furnace temperature and sufficient heat.

Increasing the slag CaO/SiO ₂ and MgO can increase the melting temperature of the slag and help to increase the temperature of the hearth.

Increase the air temperature. In the early 1960s, the wind temperature of the plant was 745-931 °C. Since 1965, the wind temperature has increased to an average of 1000 °C per year.

Oxygen-enriched blast is used. Oxygen-enriched blast can effectively increase the temperature of the hearth. Reduce the temperature of the top of the furnace. In 1982, use the residual gas of the converter to supplement a small amount of oxygen.

From the perspective of the whole measure, to increase CaO/SiO ₂ and MgO, it is necessary to increase the amount of slag, but reduce the MnO in the slag and reduce the amount of slag. At the same time, the slag-iron ratio can be reduced due to the increase of manganese recovery. For example, in the fourth quarter of 1979, low MnO operation was started, and the Mn content in the furnace was roughly equivalent to that in 1979 and 1982. The slag amount is shown in Table 3.

It can be seen that reducing MnO in the slag plays a dual role of reducing the amount of slag and reducing the amount of manganese in the slag. At present, by reducing MnO, the chemical loss of manganese in the slag is reduced to about 10%.

Table 3 Comparison of slag amount when manganese oxide is not treated

(2) reducing the top loss

The loss of manganese at the top of the furnace is mainly caused by mechanical blow damage. The main measures to reduce the loss of the roof are:

1. Manganese ore is washed and sieved to reduce the powder entering the furnace;

2. Screening under the manganese sintered ore tank reduces the powder content of the incoming charge.

Through these measures, 1984. The dust ash output is reduced to 150kg/t, which reduces the roof loss to less than 4%.

(3) Reducing mechanical losses in slag

The mechanical loss in the slag is the loss of the mixed manganese and iron mixed in the slag. The main measures to reduce this loss are as follows:

1. Set up a recovery pit in the iron slag ditch to create the sedimentation conditions of ferromanganese in the slag;

2. Set up a recovery pit in the slag yard to recover the ferromanganese in the slag tank;

3. Manually inspect the ferromanganese of the dry residue before the furnace.

Through these measures, the mechanical loss in the slag is reduced to a level of 0.4%.

Third, the conclusion

(1) Increasing the recovery rate of manganese is the core problem of smelting ferromanganese in blast furnace. For every 1% increase in recovery rate, the coke ratio can be reduced by 27.7kg/t, the mine ratio is reduced by 44.6kg/t, the yield is increased by 1.57%, and the cost is reduced by 25.53 yuan/t. And can improve product quality.

(2) The loss of manganese is mainly the chemical loss entering the slag in the form of MnO, followed by the loss of the top and the mechanical loss in the slag.

(3) Reducing Mn0 in the slag is the main direction of improving the recovery rate. The operation of high CaO/SiO ₂ and MgO slag is an effective measure to reduce Mn0 in the slag. The Mn0 in the slag of Xinyu Steel Plant has dropped to the level of 4 to 5%, and it is a leading position at home and abroad.

(4) In the case of depletion of manganese ore and large amount of slag, the recovery rate of Xinyu Steel Plant reached 85%, leading in China. The larger the amount of slag, the lower the Mn0 in the slag. The next step is to control MnO at 3.5 to 4.5%, and keep the average value at around 4%, so that the loss is controlled within 10%.

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