KR920007933B1 - Making process for fe-cr by smelting reduction process - Google Patents

Abstract

This ferrochrome (Fe-Cr) is prepared by (1) charging the raw materials comprising 49-56 wt.% chromium ore or chromium ore pallet, 29-35 wt.% limestone, 1.5-6.0 wt.% silica sand and 9-14.5 wt.% serpentinite, (2) charging the lowest amount of cokes, 90-110 % to the theoritical equivalent amount, (3) controlling the basicity (CaO/SiO2 of the above charging material to be 1.2-1.4 to obtain the optimized zero order reaction rate constant. Then melt reducing the above.

Description

Method for producing ferrochrome by melt reduction method

1 is a graph showing the change rate of the reduction reaction according to the change in the amount of coal ash (coke (charge) / coke (equivalent) × 100%).

2 is a graph showing a change in reduction reaction rate according to the slag basicity change.

The present invention relates to a method for producing ferrochrome (Fe-Cr) by chromium oxide in the chromium ore in a low-lowering converter reactor.

Conventional stainless steel is produced by chromium ore, etc. in the electric furnace to produce a ferrochrome by carbon reduction, and then to the solvent as a main raw material.

However, this method requires the use of expensive electric power, and because ferrochrome has to be solidified once and then remelted during steelmaking, ferrochrome has a high manufacturing cost. In order to solve this problem, chromium ore or pre-reduced chromium ore in a molten reduction furnace, such as a low-low converter, carbon reduction using carbonaceous material without using electric power to produce ferro chromium to produce stainless steel, that is, chrome ore Melt reduction methods (Japanese Patent Laid-Open No. 59-140319, 62-17111, 62-164848) have been tried.

However, these methods are mainly ineffective in lowering the final concentration of chromium oxides in slag to less than 1%, and the coke is charged in excess of theoretical equivalents in molten slag, which is inefficient in terms of reducing ferrochrome manufacturing cost by melt reduction method. .

On the other hand, the coke amount management which is advantageous for the reduction reaction is the residual coke amount in the molten slag. The residual coke amount is derived from the analysis of the combustion reaction such as an analysis secondary combustion rate. The calculation error is large, and the calculation process is cumbersome, and there is a method problem in using this as an operational indicator.

In addition, there is a problem in that the case of increasing the reduction rate of the chromium oxides in the molten slag due to factors other than the coke amount because the amount of coke charged as a reducing agent is much higher.

In order to maintain the chromium oxide concentration in the slag below 1%, it is necessary to increase the amount of carbon ash in the slag to maintain a strong reducing atmosphere, so that phosphorus in the coke is reduced to a molten amount, so dephosphorization treatment of the ferrochrome molten metal is required or less phosphorus is required. Expensive coke should be used, and if the chromium oxide concentration in the slag is maintained at 1% or less, the solubility of magnesium oxide in the slag increases, so that the amount of melting of the basic refractory mainly used in this method increases.

According to Japanese Patent Laid-Open No. 62-17111, in order to solve some of these problems, the amount of coke is reduced to maintain the concentration of the final chromium oxide in the slag as high as 1-4%, and inexpensive coke is used as a molten metal for phosphorus. Although there is a method of reducing the amount of reduction and the amount of refractory loss, refractory amount of coke has not been suggested.

In addition, according to Japanese Patent Laid-Open No. 62-164848, the sum of the amounts of aluminum oxide and magnesium oxide in the molten slag component is

Al ₂ O ₃ + MgO <0.16T-208T: Molten metal temperature (℃)

Such conditions are advantageous for the reduction of chromium oxide, but there is a problem that the specific slag basicity (= CaO / SiO ₂ ) which can be used as an operation indicator, such as in blast furnace or converter operation, is not clearly presented.

Accordingly, the present invention provides the lowest amount of coke that does not lower the reduction rate of chromium oxide in the melt reduction process, and provides the optimum base degree by using additives when using the lowest amount of coke to economically produce ferrochrome. There is this.

The present invention is based on the reduction of chromium, iron oxides in the chromium ore, such as the following (1), (2) based on the amount of oxygen blown from the top by using an oxygen uptake and nitrogen-lowering melt reduction reactor to achieve this object. The minimum amount of coke that does not cause a reduction in the reduction rate is suggested by changing the amount of carbon ash required for the combustion reaction, assuming that the amount of carbon ash required and the combustion reaction generates the entire CO gas as shown in Equation (3).

7Cr ₂ O ₃ + 27C = 2Cr ₇ C ₃ + 21CO... … … … … … … … … … … … (One)

3FeO + 4C = Fe ₃ C + 3CO... … … … … … … … … … … … … … … (2)

c + 1 / 2O ₂ = CO... … … … … … … … … … … … … … … … … … … (3)

In addition, the optimum conditions of slag basicity (CaO / SiO ₂ ) were suggested using subsidiary materials such as limestone, silica, and serpentine when using the lowest amount of coke.

That is, the present invention is to charge the coke raw material and coke in the melt reduction reactor in the method for producing ferrochrome by melt reduction, the amount of coke charged to 90-110% of the amount of coke required for the theoretical equivalent value, It relates to a method for producing ferrochrome by adjusting the basicity of the raw material to 1.2-1.4 to melt reduction.

In the production of ferrochrome by melting reduction by charging charged raw material and coke into the molten reduction reactor, the charged raw material is usually 49-56 wt% chromium ore or chrome ore pellets, 29-35 wt% limestone, 1.5-6.0 wt% It is composed of silica sand and 9-14.5% of serpentine.

When the charged coke amount is increased, the zero-order reaction rate constant representing the melt reduction reaction rate of the chromium ore is increased. When the amount of coke required is less than 90% of the amount of coke required by the theoretical equivalent value, a sufficient melt reduction reaction, that is, a sufficient zero-order reaction The rate cannot be obtained, and if it is 110% or more, the zero-order reaction rate constant increases, but the increase rate is not so large, and in particular, the production cost is increased due to the increased amount of coke, so that the amount of coke charged Silver is preferably 90-110% of the theoretical equivalent value.

In addition, the reason for limiting the range of basicity to 1.2-1.4 is that the optimum zero-order reaction rate constant cannot be obtained outside this range.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

Example 1

After forming a molten iron by induction heating of 400kg cold wire in a 500kg / ch melt reduction furnace (at this time, the melt temperature was maintained at 1600-1650 ℃) chromium ore pellets made of chromium ore of the composition shown in Table 1, Subsidiary materials, the coke amount of the coke in Table 2 was semi-continuously charged, and at this time also the oxygen of the following Table 2 was continuously blown to secure the furnace.

After the charging was completed, a finishing refiner was performed while blowing the coke and oxygen for combustion shown in Table 2 below. In this period, slag was collected every 8 minutes, and the concentration of chromium oxide in the slag was analyzed. The zero-order reaction rate constant in the finishing refiner was obtained and the results are shown in FIG.

TABLE 1

TABLE 2

As shown in FIG. 1, when the loaded coke is loaded at 90-110% of the coke required for the theoretical equivalent value, the zero-order reaction rate constant is almost constant, and the increase is small even if it is increased. Can be.

Example 2

The amount of coke charged to the coke required for the theoretical equivalent value was 109%, and the basicity was changed as shown in Table 3 below. The experiment was carried out according to the same method as in Example 1 to obtain a zero-order reaction rate constant. Shown in

TABLE 3

As shown in Figure 2, it can be seen that the experiment number 11 (base: 1.3) having a basicity according to the present invention has the largest zero-order reaction rate constant.

In summarizing the above Examples 1 and 2, the present invention provides an optimum zero-order reaction rate constant by adjusting the amount of charged coke to 90-110% and the basicity to 1.2-1.4 based on the amount of coke required for the theoretical equivalent value. It can be seen that.

As described above, in the present invention, if the lower limit of coke loading and basicity suggested in the present invention are operating indicators, it is possible to reduce fuel costs by using an appropriate amount of coke required for reduction of chromium oxide in the melt reduction process, and to easily manage the amount of coke. In addition, it is possible to obtain economically effective ferrochrome production by securing an optimal molten slag composition for dissolving and reducing hard-reducing chromium oxide.

Claims (1)

In the wt%, the molten reduction method was carried out by charging the charging raw material and coke formed by containing 49-56% chromium ore, 29-35% limestone, 1.5-6.0% silica sand and 9-14.5% serpentine in the melt reduction reactor. In the method for producing ferrochrome by charging, the coke is charged to 90-110% of the coke amount required for the theoretical equivalent value, and the basicity of the charged raw material is adjusted to 1.2-.1.4 to reduce the melt. Method for producing ferrochrome by melt reduction method.

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