JPH0826378B2 - Method for producing molten iron containing chromium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a smelting reduction furnace such as an up-down blow converter to melt-reduce chromium ore and a pretreated product of chromium ore with a carbon source such as coal or coke to produce stainless steel. The present invention relates to a method for producing molten iron containing chromium having a chromium content of 39% or less during production.

Conventional technology and its problems Conventionally, stainless steel has been produced by melting chromium ore and the like in an electric furnace using ferrochrome produced by carbon reduction. However, in this method, the cost of ferrochrome is high due to the use of expensive electric power and the large energy loss because the ferrochrome is once solidified and remelted in the steelmaking process, resulting in a cost increase of stainless steel. It was rude.

In order to solve such a problem, for example, chromium ore or a pretreated product thereof is carbon-reduced with coke or the like in a smelting reduction furnace such as a vertical blowing converter without using electric power to melt ferrochrome to produce stainless steel. A method for producing steel, that is, a smelting reduction method for chromium ores (Japanese Patent Laid-Open No. 54-158320, etc.) has been attempted.

The smelting reduction method of chrome ore is to dissolve chrome ore in molten slag to form slag containing Cr oxide and Fe oxide, and reduce with [C] in the molten metal or carbonaceous material such as coal or coke. According to the above, the basic principle is to produce molten iron containing chromium.

 That is, the following reaction proceeds.

(Cr ₂ O ₃ ) + 3C = 2 Cr + 3CO (FeO) + C = Fe + CO The above reaction is a large endothermic reaction. Therefore, in order to smelt and reduce chromium ore, it is necessary to twist the means of heat supply, and therefore various methods of burning fuel such as coal and coke with oxygen and air have been tried.

In the case of smelting reduction of chromium ore, a large amount of slag is generated, and the interface between the slag and the metal or carbonaceous material is the reduction reaction interface. Need to be burned. As the method, a carbonaceous solid such as coal powder and coke powder and an oxidizing gas such as oxygen and air are blown into a metal bath and burned (JP-A-58-100656), as well as coke on a slag bath. Method of floating burning carbonaceous material
59-140349) is known.

In the method disclosed in JP-A-58-100656, most of the injected carbonaceous material burns up to CO. Even in the blowing tuyeres near was completely burned to CO _2, CO ₂ immediately in hot metal [C]
It reacts with and becomes CO gas.

On the other hand, according to the method disclosed in JP-A-59-140349, the carbonaceous material such as coke floating in the reactor immediately reacts with CO ₂ gas to form CO gas, so that most of it burns up to CO gas.

In other words, in each of the methods, the heat is supplied by partially oxidizing the fuel (incomplete combustion), but the amount of heat generated is small by itself, and therefore it is inevitable to consume a large amount of fuel and oxygen.

By the way, in the case of the C fuel as an example, the combustion amount is greatly different between the partial oxidation and the complete combustion.

In the smelting reduction method of chromium ore, if a method of completely burning the fuel without hindering the reduction reaction and effectively transferring heat to the slag / metal bath in order to greatly reduce the fuel and oxygen unit consumption is to be developed. , Its productivity and economic efficiency can be dramatically improved, and the development of the method has been awaited.

OBJECT OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the related art, and in a slag bath which is present in a large amount during the smelting reduction of chromium ore, a fuel containing carbon and hydrogen as the main components and oxygen are almost used as fuel. By blowing in a ratio that will burn completely,
Burns fuel almost completely, efficiently heats the slag bath,
Moreover, in order to rapidly reduce chromium oxide and iron oxide derived from chromium ore at the slag-metal interface, a method for producing chromium-containing molten iron, characterized in that a reducing agent such as coal or coke is blown into the metal bath. It is a proposal.

Configuration of the Invention A method for producing molten iron containing chromium according to the present invention is a method for producing a chromium ore, an unreduced chromium pellet produced by pretreating a chromium ore, a semi-reduced chromium pellet, a chromium sintered ore, etc. as a carbon source such as coal or coke. When producing molten iron containing chromium with a chromium content of 39% or less by smelting and reducing with, blow a fuel containing carbon and hydrogen as the main components and oxygen in a ratio so that the fuel burns almost completely in the slag bath. Due to
It is characterized in that the fuel is burned to heat the slag bath, and a reducing agent such as coal or coke is blown into the metal bath to keep the [C] concentration at 3% or more.

That is, the present invention is a method for injecting fuel and oxygen into the slag bath to enable complete combustion of the fuel and to easily transfer the heat of combustion to the slag bath.

In the present invention, the chromium content is limited to 39% or less, the purpose of this process is to produce a chromium-containing mother molten metal for melting stainless steel,
This is because it is not necessary to raise the Cr concentration to 40% or more.

 Hereinafter, the method of the present invention will be described in detail.

As a result of various studies on the thermal efficiency improvement measures (combustion and oxygen consumption reduction measures) in the method of producing chromium-containing molten iron by smelting reduction of chromium ore or its pretreatment product, the present inventors It has been found that the fuel such as coal and coke and oxygen can be blown into the slag at a ratio such that the fuel is almost completely burned, so that the fuel can be almost completely burned and the heat can be effectively transferred to the slag bath.

Next, when the smelting reduction reaction rate of chromium ore was investigated under the condition of complete combustion of fuel by blowing into the slag, it was found that it basically does not affect the reduction reaction rate between the slag and the metal. . This is because the combustion zone of the injected fuel is in the slag bath well above the slag-metal interface, so the CO ₂ gas generated by combustion rises in the slag bath but does not reach the slag-metal interface. This is because there is no action of interfering with the reduction reaction such as reoxidation of the produced metal. However, [C] in the metal is consumed by the reduction reaction between the slag and the metal, and the [C] concentration in the metal decreases as the reduction progresses.
It was found from an experiment that the reduction reaction rate was significantly reduced when the [C] concentration was 3% or less. Therefore, it is necessary to add C to the metal bath by some means to keep the [C] concentration at 3% or more. If a reducing agent such as coal or coke is added from the upper part of the reactor, it cannot be carburized in the metal because it is hindered by the slag bath, and the CO ₂ gas generated by complete combustion in the slag reacts with the reducing agent to generate CO. Will return to.

Therefore, as a result of various studies, by blowing a reducing agent such as coal or coke into the metal bath, it is possible to easily carburize the metal bath even under the condition that the fuel is completely burned in the slag bath, and [C] It was found that the smelting reduction reaction of chromium ore can be completed rapidly by keeping the concentration at 3% or more.

The present invention was made based on the above findings, and when producing molten iron containing chromium by smelting and reducing chromium ore, a fuel containing carbon and hydrogen as the main components and oxygen as the fuel are almost always contained in the slag bath. Blows at a rate that completely burns to completely burn the fuel and efficiently heat the slag bath, and blow a reducing agent such as coal or coke into the metal bath to keep the [C] concentration at 3% or more. This is characterized in that the smelting reduction reaction proceeds rapidly.

Examples of the fuel blown into the slag include solid fuels such as coal and coke, liquid fuels such as petroleum and tar, and gas fuels such as methane and natural gas.

 Next, the method of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing an apparatus for carrying out the method of the present invention. In the figure, (1) is a converter-type reaction vessel for storing a metal bath, and the metal bath (2) (for example, molten pig iron or molten steel) is housed inside. (3) is a slag layer.
Reference numeral (4) is a lateral tuyeres for blowing in fuel and oxygen, and the amount of heat required for reduction is supplied by the combustion heat at the tuyeres. , (5) are bottom blowers for blowing carbonaceous material, to which a carbon source necessary for the reduction reaction at the slag-metal interface is supplied.

In the present invention, basically, the amount of heat required for the reduction is supplied by the complete combustion of the fuel in the slag layer. However, in order to ensure the complete combustion of fuel in the furnace, CO ₂ combustion assisting O ₂ was installed above the slag layer for CO combustion top blow lance (6) and CO combustion side blower tuyere (7). It is also possible to supply more.

The side blower mouth (4) for injecting fuel and oxygen has, for example, N ₂ + coke powder (coal powder) from the central tube, O ₂ from between the central tube and the outer tube, and cooling gas (from the outer tube ( N ₂ , C ₃ H ₈ etc.)
It is possible to use a triple tube tuyere having a structure of blowing air. Chromium ore, slag forming agents (coal stone, silica stone, etc.) and raw materials are charged into the furnace from the upper part of the reaction vessel.

 Hereinafter, examples of the present invention will be described.

Example 1 The results of smelting reduction of chromium ore under the conditions shown in Table 1 using a 10-ton top-bottom blowing converter having the same structure as the reaction vessel shown in FIG. 1 were obtained by suspending lump coke in slag. Table 2 shows the comparison with the conventional method in which the reduction is advanced while burning the carbonaceous material.

As is clear from Table 2, the carbonaceous material can be completely burned by the method of the present invention, and the combustion site and the reduction site of the carbonaceous material can be separated. It became possible to shorten.

Example 2 Using a 10 ton bottom blowing converter, the semi-reduced chromium pellets ((% T.Cr) 32.2, (% T.Fe) under the raw material mixing conditions shown in Table 3 and the blowing conditions shown in Table 4 were used. = 21.6, Cr reduction rate 62%,
As a result of melt reduction of Fe reduction rate of 87%), [% Cr] = 1 as shown in Table 5 for treatment time, hot metal after treatment, and slag composition.
It was possible to melt 5.8% chromium-containing hot metal in 70 minutes.

EFFECTS OF THE INVENTION As described above, according to the method of the present invention, in the smelting reduction treatment of chromium ore or the like, while maintaining the rapid reduction progress of chromium oxides and iron oxides, fuel (pulverized coal, powder coke, etc.) Since it can burn almost completely with oxygen and efficiently heat the slag bath / metal bath,
It is possible to significantly reduce the fuel and oxygen consumption rate and shorten the refining time, and it is possible to reduce refining costs and improve productivity.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for carrying out the method of the present invention. 1 ... Converter-type reaction vessel, 2 ... Metal bath, 3 ... Slag layer, 4 ... Side blower for fuel and oxygen injection, 5 ... Bottom blower for carbon material injection, 6 ... CO combustion Ugebuki Lance, 7 ... CO
Side blowing tuyeres for combustion.

Claims (1)

[Claims] 1. A chromium ore, unreduced chromium pellets produced by pre-treating chromium ore, semi-reduced chromium pellets, chromium sintered ore, etc., are melt-reduced with a carbon source such as coal or coke to obtain a chromium content of 39. In the method for producing molten iron containing less than 50% chromium, the fuel containing carbon and hydrogen as main components and oxygen are blown into the slag bath at a rate at which the fuel is almost completely burned to burn the fuel and heat the slag bath. At the same time, a method for producing molten iron containing chromium, which comprises blowing a reducing agent such as coal or coke into a metal bath.