JP2001279338A - Production method for molten iron using rotary kiln - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the recovering ratio of an iron from an iron oxide- containing material to be treated and to reduce the consumption of a reducing agent by further improving a production method for molten iron using a rotary kiln. SOLUTION: In the production method for molten iron using the rotary kiln for producing the molten iron by mixing the reducing agent into the iron oxide- containing material to be treated, charging them into the rotary kiln, and reducing and melting, as the reducing agent, a coal (A) and a petroleum coke or a graphite (B) are used and the ratio of the coal (A) to the whole reducing agent (A+B) is kept to 20-60 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing molten iron using a rotary kiln.

[0002]

2. Description of the Related Art In the prior art for producing molten iron using a rotary kiln by using fine ore, blast furnace dust, steelmaking dust and the like as iron oxide-containing workpieces, a zinc component is evaporated and removed from the iron oxide-containing workpiece. At the same time, the molten iron is produced by reducing and melting, and finally recovered as pelleted iron solids. Then, the iron solids in the form of pellets are sent to a sintering process.

[0003] Conventionally, coal or coal coke has been used as a reducing agent to be mixed with an iron oxide-containing material to be processed and fed into a rotary kiln. Particularly, in view of its high reactivity, fine powder is used. The know-how was to mix a reducing agent in the form of an iron oxide-containing material to be processed into a granular material. That is, conventionally, coal or coal coke has been used as a carbon material, and in particular, its fine powder has been used as interior coal.

[0004]

An object of the present invention is to further improve the method for producing molten iron using a rotary kiln as described above to improve the iron recovery rate from the iron oxide-containing workpiece and to reduce the consumption of the reducing agent. Is the object of the present invention.

[0005]

An object of the present invention is to provide a method for producing molten iron using a rotary kiln according to the present invention, that is, mixing a reducing agent into an iron oxide-containing workpiece and charging the mixture into a rotary kiln. A method for producing molten iron using a rotary kiln, wherein the molten iron is produced by reduction and melting, wherein coal (A) and petroleum coke or graphite (B) are used as the reducing agent, and a total reducing agent (A +
This is achieved by a method for producing molten iron using a rotary kiln, wherein the proportion of coal (A) in B) is maintained at 20 to 60 wt%.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

[0007] The reduction reaction of the iron oxide-containing treatment object is a gas-solid reaction in a rotary kiln, and is as shown in Equation 1.

Formula 1 Fe ₂ O ₃ + 3CO = 2Fe + 3CO ₂ 3CO ₂ + 3C = 6CO This reaction occurs in a temperature range of 1000 ° C. or less.

FIG. 1 is a graph showing the relationship between reactivity index and temperature for coal and petroleum coke. Coal has a reactivity index of 100 at 1000 ° C and a reactivity index of 70 at 950 ° C, whereas petroleum coke as a reducing agent has a reactivity index of 10 at 1100 ° C.
At 0 and 1050 ° C., the reactivity index is 90, at 1000 ° C. the reactivity index is as low as about 50, and at 950 ° C., the reactivity index decreases to 25.

The "reactivity index" is based on JIS-K215
This was determined by the present inventors based on the coke reactivity test specified in 1.

In the temperature range of 1000 ° C. or less, it has been found that the use of coal as a reducing agent has a much higher reaction and is advantageous.

Although the above reduction reaction produces solid reduced iron, at the same time, the carburizing reaction shown in equation 2 occurs, and molten iron (Fe ₃ C) is obtained.

[Formula 2] Fe (S) + 3C = Fe ₃ C (l)

This carburizing reaction occurs in a temperature range of 1000 ° C. or higher. In this temperature range, both coal and petroleum coke have high reactivity as shown in FIG. Therefore, the selection of the type of reducing agent should be determined based on whether a sufficient amount remains in this temperature range.

[0013] Coal is highly reactive at low temperatures, is largely consumed, and a small amount of coal remains in the temperature range of 1000 ° C or higher. On the other hand, it has been found that a sufficient amount of petroleum coke remains even in a temperature range of 1000 ° C. or higher. Therefore, petroleum coke is advantageous for the carburizing reaction.

If the above findings are integrated, coal is advantageous for a reduction reaction at a relatively low temperature, while petroleum coke is active for a carburization reaction at a high temperature. Therefore, it has been conceived that if the coal (A) and the petroleum coke (B) are properly mixed, the iron recovery rate can be maximized with a minimum amount of carbon material.

FIG. 2 is a diagram showing the relationship between the iron recovery rate and the carbon material mixture ratio. Using coal (A) and petroleum coke (B) as the coal material, while keeping the total reduction equivalent of the carbon material constant at 3 equivalents, coal (A) / (coal: A + petroleum coke:
An experiment was conducted in which the ratio of B) was varied, and molten iron was produced from ironmaking dust using a rotary kiln.

When only petroleum coke is used, that is, A /
When (A + B) × 100 is 0, the iron recovery rate is 50%
It is. Petroleum coke (B) with 1.2 equivalents of coal (A)
Is 1.8 equivalents, that is, A / (A + B) × 10
When 0 is 40, the iron recovery rate reaches a maximum of about 80%. When the coal is 2.1 equivalents and the petroleum coke is 0.9 equivalents, that is, when A / (A + B) × 100 is 70, the iron recovery is about 60%. When only coal is used, that is, when A / (A + B) × 100 is 100, the iron recovery rate is about 30%. As a result of the test, it became clear that the iron recovery rate differs depending on the mixing ratio of the carbonaceous materials. In addition, the ratio of coal / (coal + petroleum coke) is 20 to
It was found that the iron recovery rate was improved in the range of 60 wt%.

Similar tests were conducted using graphite as a carbonaceous material instead of petroleum coke. As a result, it was confirmed that petroleum coke and graphite behave almost identically.

[0018]

According to the method for producing molten iron using the rotary kiln of the present invention, coal (A) and petroleum coke or graphite (B) are used as the reducing agent, and the proportion of coal in the total reducing agent is 20 to 60 wt. %, The iron recovery rate can be improved to about 80%, the consumption amount of all reducing agents can be reduced to three reduction equivalents, and the production cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between reactivity index and temperature for coal and petroleum coke.

FIG. 2 is a diagram showing a relationship between an iron recovery rate and a carbon material mixture ratio.

Claims (3)

[Claims] 1. A method for producing molten iron using a rotary kiln, comprising mixing a reducing agent into an iron oxide-containing treatment object, charging the mixture into a rotary kiln, and reducing and melting the molten iron to produce molten iron. , Coal (A) and petroleum coke or graphite (B), and the total reducing agent (A +
A method for producing molten iron using a rotary kiln, wherein the proportion of coal (A) in B) is maintained at 20 to 60 wt%. 2. The method for producing molten iron using a rotary kiln according to claim 1, wherein the particle size of the reducing agent is 0.5 to 4 mm. 3. CaO and Si together with the object to be treated.
A substance containing O ₂ is charged into a rotary kiln, and the basicity (CaO / SiO ₂ ) is 1.5 or more, preferably 2.
The method for producing molten iron using a rotary kiln according to claim 1 or 2, wherein the amount is in the range of 0 or more, and the amount of the reducing agent is 2.5 or less.