Third, manganese iron smelting furnace feed
The raw materials are manganese ore, coke and flux. 1. Manganese ore The manganese ore is mainly composed of manganese oxide ore, sintered ore, roasting ore and manganese-rich slag.
In addition to the main component Mn, manganese ore also contains a certain amount of impurities such as Fe, CaO, Al ₂ O ₃ , SiO ₂ , P, S, etc., which should be controlled according to the requirements of the smelting products.
The ferromanganese ratio in manganese ore is an important technical parameter determining the manganese content of the product. Different grades of high-carbon ferromanganese are used to different the m(Mn)/m(Fe) requirements of the manganese ore in the furnace. When a factory uses the flux method to smelt The manganese content, m(Mn)/m(Fe), m(P)/m(Mn) requirements for the manganese ore in the furnace are shown in Table 2.

CaO and MgO in manganese ore are alkaline oxides, which are beneficial to adjusting alkalinity and fluidity of slag, and are generally not limited. Al ₂ O ₃ in manganese ore can control the manganese content in the slag within a certain range, but if the Al ₂ O _{3 is} too high, the melting point of the slag will increase, the fluidity will be deteriorated, and the separation of slag and iron will be difficult, which will affect the technical indicators of smelting. It is generally required that the content of Al ₂ O _{3 in the} manganese ore entering the furnace does not exceed 10%. The lower the SiO ₂ content in the manganese ore produced by the flux method, the better. Due to the high content of SiO ₂ , the amount of lime is increased, the amount of slag is increased, and the power consumption is increased. Manganese sulfur typically in the form MnS, CaS or volatilization into the slag, only about 1% into the alloy, generally is not limited.
The moisture control of the manganese ore in the furnace is controlled below 8%. Because the moisture is too high, the fluctuation meeting affects the accuracy of the ingredients. In the production of the flux method, the lime is pulverized and pulverized, resulting in poor gas permeability in the furnace, causing splint and collapse, which deteriorates the furnace condition and increases the power consumption.
The grain size of the manganese ore entering the furnace depends on the capacity of the electric furnace. The particle size of the electric furnace above 6000KVA is generally 10~80mm, and the powder ore less than 10mm does not exceed 10% of the total.
2. Coke coke as reductant mainly metallurgical coke, gas, coal and coke, semi-coke. For the coke entering the furnace, it is required to have a fixed carbon content, a large electrical resistivity, a low ash content, and a low phosphorus . The amount of slag brought in by the ash is small, and the phosphorus content is correspondingly reduced, which can reduce the smelting power consumption. The resistivity is large, and it is easy to insert the electrode, which is advantageous for stable operation.
The size of the coke entering the furnace is generally 3~25mm, and the end of the coke less than 3mm is not allowed to enter the furnace. The moisture content of coke should not exceed 7%, and the fluctuation should be as small as possible.
3. Solvent (lime)
It is required that the content of CaO in lime is high, and the content of SiO ₂ and P, S impurities is low. Generally, the CaO content is greater than 80%, the SiO ₂ content is not more than 6%, and P, S should be less than 0.05% and 0.8%, respectively. The size of lime into the furnace is generally 10~60mm.[next]
Fourth, electric furnace high carbon ferromanganese smelting process operation
1. Smelting method The smelting of high-carbon ferromanganese in electric furnace is carried out continuously, that is, continuous feeding and smelting, and regular ironing. According to the difference of the grade of manganese ore in the furnace and the control of alkalinity of slag, three methods of producing high-carbon ferromanganese in the electric furnace are flux method, flux-free method and less flux method.
(1) flux method Using alkaline slag operation, in addition to manganese ore and coke in the charge, a certain amount of flux (lime) is added and a foot reducing agent is used. Using high alkalinity slag operation, the slag basicity n(CaO)/n(SiO ₂ ) is controlled at 1.3~1.4, so as to minimize the manganese content in the slag and improve the manganese recovery rate.
(2) The flux-free method is operated by acid slag, the lime is not added to the charge, and it is smelted under the condition of insufficient reducing agent. By using this method, high-carbon ferromanganese can be obtained, and silicon-manganese alloy and medium and Low-manganese iron containing 30% Mn low-phosphorus manganese-rich slag. The advantage is low power consumption and high comprehensive recovery rate of manganese. The disadvantage is that the operation of the acid slag is carried out, the corrosion of the carbonaceous furnace lining is serious, and the life of the lining is short.
(3) Low-flux method The "acid-acid slag method" between the flux method and the flux-free method is employed. The method is to add a small amount of lime or dolomite to the ingredients, control the slag's large alkalinity between 0.6 and 0.8, and smelt under weak carbon conditions. Produce qualified high-carbon ferromanganese and manganese containing 25%~40% and proper amount of CaO low-phosphorus and low-iron manganese slag. The slag is used for the production of silicon-manganese alloy, which can reduce the amount of lime added and reduce the amount of dust increased by lime deliquescence, thereby improving the gas permeability of the charge.
The method used is related to the grade of the furnace. The grade of the ore in the furnace is generally low, and the grade of the ore into the furnace is high (high-grade imported ore). The high-carbon ferromanganese is produced by the non-flux method or the less flux method.
2. Smelting process operation The production process of high-carbon ferromanganese in electric furnace mainly includes batching, feeding, furnace condition maintenance and iron casting.
(1) Ingredients and feeding materials According to the ingredients, the proportions are calculated according to the order of manganese ore, coke, lime (dolomite), and then the materials are sent to the furnace top silo through the transportation system. Feeding platform. It is added to the furnace in batches according to the needs of the furnace.
(2) Maintenance of furnace condition In the process of electric furnace smelting, due to the fluctuation of raw materials, electrical and mechanical equipment and other factors, the furnace condition is difficult to maintain a stable state for a long time, and is always fluctuating. Therefore, it is necessary to make timely judgments on the condition of the furnace, and make accurate judgments based on the changes, and take measures to adjust and deal with them in time to restore the furnace condition to a normal state.
(3) Judgment and treatment of furnace conditions The signs of normal furnace conditions are:
1 The operating current is stable, the electrode insertion depth is appropriate, and the electrode voltage is normal.
2 The height of the material surface is suitable, the fire is even, the material of the furnace is uniform, and the phenomenon of smoldering and stagnation around the electrode is less.
3 The furnace gas pressure, composition and temperature in the closed furnace are normal.
4 The slag composition is stable, the output is stable, and various technical and economic indicators are good.
5 alloy composition is stable, the output is stable, and various technical and economic indicators are good.
The deterioration of the furnace condition is not caused by too much or insufficient reductant and excessive or too low slag alkalinity.
When the reducing agent is too much, the electric resistance increases, the current increases, the electrode rises, the material speed in the furnace slows down, the spurt around the electrode is severe, the furnace gas pressure and temperature rise, and the manganese volatilization loss increases. The temperature drops, the furnace is difficult to be produced, and the silicon content of the product increases. At this time, the amount of carbon should be reduced around the electrode and the amount of coke in the batch should be adjusted.
When the reducing agent is insufficient, the electrode is inserted deeper, the electrode consumption is increased, the load is not going up, the current is unstable; the furnace mouth is turned over; the manganese content in the slag is increased, the silicon in the product is low in phosphorus, and the slag is less iron. At this point, an appropriate amount of coke can be added around the electrode, and the coke ratio can be increased in the batch.
When the alkalinity of the slag is too high, the electrode is lifted up in the furnace; the surface is spurred and the slag is turned; the slag has poor fluidity, the iron output is small, the slag is dark and rough, the cross-section hole is quickly pulverized after cooling. When the alkalinity of the slag is too low, the electrode is inserted deep, the slag is thin, the fluidity is good, the surface of the slag is less wrinkled, and the slag is run with more manganese. In view of the above situation, the lime compounding amount should be adjusted in time to adjust the slag alkalinity to the normal range.
(4) Iron tapping and casting Normally, the electric furnace should be ironed at regular intervals, and the number of tapping times depends on the size of the electric furnace. Generally, large electric furnaces produce 4 to 5 times of iron per shift, and small and medium-sized electric furnaces have 2 to 3 times per shift. According to the production experience of some factories, in the case of normal smelting conditions in the furnace, proper extension of the iron separation room has a good effect on improving product quality, reducing coke ratio and electricity consumption. [next]
5. Calculation of ingredients In the production of ferroalloys, it is impossible to accurately calculate the factors in production. Therefore, it is not easy to make accurate ingredient calculations. And it doesn't mean much in practice. Usually based on raw material composition, control parameters and empirical data in production, preliminary calculations are carried out, and after production, adjustments are made according to the conditions in the furnace. The calculation conditions are as follows:
The composition of the smelting alloy is: Mn 66%, SiO ₂ 2%, C6.8%, P0.3%, Fe 23%, and other 0.9%.
The raw material composition is:
Manganese ore: (comprehensive mine) Mn34%, Fe10%, P0.12%, SiO ₂ 9%, CaO1.5%
Coking: C80%
Lime: CaO80%
Slag basicity: n (CaO) / n (SiO ₂ ) = 1.4
The distribution of each element in the smelting product is shown in Table 3. The coke utilization rate is 90%.

Calculated based on 100kg manganese ore.
(1) Calculating the amount of coke The amount of coke used is the sum of carbon for manganese, iron, silicon reduction and carburizing amount of alloy:
1100kg manganese ore reduced to the amount of alloy
The total amount of manganese, iron and phosphorus is:
100×34%×78%+100×10%×95%+100×0.12%×75%=36.11kg
The proportion of manganese, iron and phosphorus in the alloy is:
100%-C content-Si content-other=100%-6.8%-2%-0.9%=90.3%
The total amount of alloys obtained from 100kg manganese ore is:
36.11kg÷90.3%=40.12kg
The silicon content in the alloy is:
40.12kg×2%≈0.824kg
2 alloy carburizing amount 40.12kg × 6.8% = 2.728kg
3 Manganese, iron, silicon reduction carbon amount Reduction of MnO, the amount of carbon used is: MnO+C===Mn+CO

The amount of carbon used to reduce FeO is: FeO+C===Fe+CO

The total amount of coke (dry basis) is:
(2.72+6.672+2.036+0.686)÷90%÷80%=16.83kg
(2) The amount of lime in the slag is SiO ₂ content

The amount of lime is: (6.22 × 1.4) ÷ 80% = 10.89kg
(3) The ratio of raw materials is: manganese ore 100kg; coke 16.8kg; lime 10.89kg.

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