JPH02282410A - Smelting reduction method for ore - Google Patents

Abstract

PURPOSE:To enable smelting reduction improving secondary combustion ratio and heat transferring efficiency in a furnace by adequately controlling distance between side blow tuyere and molten metal surface. CONSTITUTION:By using a top and bottom combined blowing converter 1 (diameter in the furnace D) providing the side blow tuyeres 2 at the furnace wall, the smelting reduction of iron ore, etc., is executed. Then, by blowing the oxygen into slag 3 from the side blow tuyeres 2 so that the distance H between the side blow tuyere 2 and the molten metal surface 4 satisfies the condition of 0.3D<=H<=1.5D, the height of the molten metal surface 4 is controlled. By this method, the high secondary combustion ratio and high heat transferring efficiency in the furnace is achieved. Therefore, the productivity can be improved and the using quantity of carbonaceous material can be reduced.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention provides a method for melting and reducing ore using a top-bottom blowing converter equipped with a side-blowing tuyere on the furnace wall. The present invention relates to a method for melting and reducing ore in which the height of the bath surface is controlled so that the height of the bath surface is maintained at a predetermined distance, thereby improving the secondary combustion ratio in the furnace and the heat transfer efficiency.

(Prior Art) Conventionally, pig iron has been mostly produced by the blast furnace method. Although the blast furnace method has high productivity and extremely good thermal efficiency, it has the disadvantage of requiring expensive coke as fuel. Recently, attempts have been made to use cheap coal to melt and reduce iron ore in a top-bottom blowing converter to produce hot metal (Japanese Patent Application Laid-Open No. 62-60805), and to produce hot metal using alloys such as stainless steel. In this field, a method for melting and reducing using a converter instead of the conventional electric furnace has been proposed.
9608).

By the way, the most important thing in the ore melting reduction method is to supply sufficient heat. For this reason, in the smelting reduction method, a so-called in-furnace secondary combustion method is implemented in which CO generated during operation is combusted in a furnace. However, since this in-furnace secondary combustion method is an exothermic reaction in the gas phase as shown in equation (1) below, when the secondary combustion ratio is increased, the exhaust gas temperature rises significantly and the in-furnace refractory There is a problem that gas calories are reduced due to melting and loss of CO in the exhaust gas.

CO+1/2 0x = C(h ・ ・ ・
・(1) Therefore, in order to solve this problem, the present applicant has developed a method of (1) coating the constricted part around the converter furnace with carbon material (Japanese Patent Application Laid-Open No. 157811/1983), and (2) coating the top blowing lance with a carbon material. We proposed a method (Japanese Unexamined Patent Publication No. 62-272316) in which carbonaceous material is injected from a provided nozzle toward the mouth of the converter furnace.

According to method (2) above, CO8 in the exhaust gas and C in the carbon material cause an endothermic reaction according to the following formula (2), thereby lowering the temperature near the refractory.

C+COx -2CO--... (2) Even when the secondary combustion ratio is increased, the temperature drop caused by this endothermic reaction can suppress melting of refractories and increase the calories in the exhaust gas. .

According to the method (2) above, the carbon content in the powder causes an endothermic reaction of the above formula (2) with COI in the high-temperature exhaust gas, and the temperature near the refractory is lowered, so that melting loss is prevented.

However, the above methods (1) and (2) each have the following problems.

In method (2), when the converter is tilted to tap the metal, carbon in the coating material is eluted and rises in the metal (C). In method (2), the refractories in the areas where the carbonaceous powder is sprayed are cooled more than necessary, causing spalling.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the following problems when melting ore is reduced using a top-bottom blowing converter equipped with a side blowing tuyere for blowing oxygen into the furnace wall.
It is an object of the present invention to provide a method for melting and reducing ore, which can improve the secondary combustion ratio and heat transfer efficiency in a furnace by appropriately controlling the distance between the side blowing tuyeres and the metal bath surface.

(Means for Solving the Problem) The present inventors have proposed a method for improving the secondary combustion ratio and heat transfer efficiency when performing melt reduction using a top-bottom blowing converter equipped with side blowing tuyeres on the furnace wall. As a result of various studies, we found that there was a large amount of slag on the metal in the furnace, and a large amount of carbonaceous material and granulated iron were mixed near the metal bath surface. If only the oxygen is blown into the slab, it will be consumed by the oxidation of suspended carbonaceous materials and granulated iron in the slab, making it impossible to increase the secondary combustion ratio and heat transfer efficiency. I learned that it is necessary to control the height of the bath to maintain an appropriate distance between the two.

Therefore, as shown in Fig. 1, a top-bottom blowing converter 1 (furnace internal diameter D) equipped with a horizontal blowing tuyere 2 on the furnace wall is used. The distance from the bath surface! ! We investigated how the secondary combustion ratio and heat transfer efficiency change when H is changed. Note that the first
In the figure, 5 is a top blowing lance and 6 is a bottom blowing nozzle. .

The results are shown in Figure 2. In Figure 2, the horizontal axis is the ratio (H/
D), where the vertical axis is the secondary combustion ratio η, the heat transfer efficiency η,
It is. As is clear from this figure, the secondary combustion ratio η,
(denoted by O) is low when H/D is less than 0.3, but reaches approximately 45% when it becomes 0.3. Then, as H/D increases, it increases little by little, while the heat transfer efficiency η, (・
) is significantly high when H/D is smaller than 0.3, but becomes about 85% when H/D reaches 0.3, and remains almost unchanged until H/D reaches 1.5. However, when H/D exceeds 1.5, it rapidly decreases. Note that the secondary combustion ratio 77 is expressed by the following formula.

1, - CC0M / (Cot +C0))X100
Further, the heat transfer efficiency η is expressed by the following formula.

ηb-(1(Q-/　Q-c)　)　Xto.

Here, 0. . is the heat of combustion of CO and H8, 0. is the exhaust gas superheat and can be expressed by the following formula.

Ql- (total human heat) - (obvious increase in metal and slag) - (sensible heat of gas equivalent to metal temperature) - (heat of reduction of ore) - (heat of decomposition of coal) - (radiation from the furnace body) Heat dissipation) - (Heat of dissolution of C) - (Heat of vaporization of H and O in the raw materials) By the way, the reason why the secondary combustion ratio η and heat transfer efficiency η change as shown in Figure 2 is thought to be due to the following reasons. It will be done.

The reason why the secondary combustion ratio η is low when H/D is less than 0.3 is because the distance H between the metal bath surface and the side blowing tuyere is too short, and the oxygen blown through the tuyeres is absorbed by the carbonaceous materials and particles in the slag. This is because CO is consumed for decarburization of iron or metal and oxidation of Fe, and secondary combustion of CO cannot be performed sufficiently. Also, H/D is 1
．． The reason why the heat transfer efficiency η decreases when it exceeds 5 is because the metal bath surface and the side blowing tuyeres are too far apart, and the heat generated by secondary combustion is discharged outside the furnace without being transferred to the metal. This is because it will be put away. Therefore, in the present invention, it is necessary to control the height so that the distance H between the side blowing tuyere and the metal bath surface satisfies the following formula.

0.3D≦H≦1.5D Here, H is the distance between the side blower and the metal bath surface, and D is the inner diameter of the converter.

As described above, when ore is smelted and reduced, by controlling the bath surface height so that the distance between the side blowing surface and the metal bath surface is appropriate, the secondary combustion ratio in the furnace and the heat transfer efficiency can be significantly increased. I can do it.

(Example 1) Hot metal (by weight, C: 4.5 %, Si: 0.01%, Mn: 0.1
0%, P: 0.015%) and 5 tons of chromium ore (
In weight%, T, Cr: 31.0%, T, Fe: 20.6
%), coke, charged with quicklime and silica stone as auxiliary raw materials,
Chromium-containing hot metal was produced under the operating conditions shown in Table 1.

The number of horizontal blowing tuyeres at this time was four, and the operation was controlled so that the metal bath surface was below the tuyere by I D (1.6 m). As a comparative example, an operation was also carried out in which the metal bath surface was controlled to be 0.15 D (0.24 m) from the horizontal blowing tuyere. As a result, the secondary combustion ratio in the comparative example was 40
%, but in the case of the example of the present invention, it was 65%, which was 15% higher than that of the comparative example. In addition, the heat transfer efficiency is 8 in the comparative example.
7%, and in the example of the present invention it was 85%, and there was almost no difference.

(Hereinafter, blank spaces) Table 1 Table 2 (Example 2) Several types of hot metal containing different components (in weight %, C: 4.3 to 4.6%, Si :0.01
%, Mn: 0.15%, P: 0.012~. 018%
), lump coal (volatile content VM: 34% by weight), iron ore (τ, Fe: 66% by weight), and quicklime were charged,
Operations were carried out under the conditions shown in Table 2 with various metal bath surface heights.

The results are shown in Table 3.As is clear from this table,
Both the secondary combustion ratio and heat transfer efficiency were good when H/D was in the range of 0.30 to 1.5D.

Table 3 If so, a high in-furnace secondary combustion ratio and heat transfer efficiency can be achieved.

Therefore, it becomes possible to improve productivity and reduce the amount of carbon material used.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a top-bottom blowing converter equipped with side blowing tuyeres on the furnace wall in which the method of the present invention is carried out, and FIG.
FIG. 2 is a diagram showing the relationship between the distance MH from the side blowing tuyere to the metal bath surface and the converter inner radius), the secondary combustion ratio, and the heat transfer efficiency. 1 is a top and bottom blowing converter, 2 is a side blowing tuyere, 3 is a slag, 4 is a metal, 5 is a top blowing lance, and 6 is a bottom blowing nozzle.

Claims (1)

[Scope of Claims] When melting and reducing ore using a top-bottom blowing converter equipped with a horizontal blowing tuyere on the furnace wall, the bath is adjusted so that the distance between the horizontal blowing tuyere and the metal bath surface satisfies the following conditions. A method for melting and reducing ore, which is characterized by controlling the surface height. 0.3D≦H≦1.5D Here, H is the distance between the horizontal blowing tuyere and the metal bath surface, and D is the inner diameter of the converter.