JPH03177512A - Method for restraining erosion of refractory in smelting reduction - Google Patents

Abstract

PURPOSE:To prevent the local erosion of a refractory by using a nozzle having asymmetric structure and making no intersection between dropping locus of charged raw material and jet of oxygen-containing gas at the time of top- blowing the oxygen-containing gas by using the porous nozzle. CONSTITUTION:In a furnace, which can blow gas from top and bottom, ore or pre-reduced material and carbonaceous material of coal, etc., are charged from upper part of the furnace. At this time, the nozzle having asymmetric structure for oxygen top-blowing, is used and the oxygen blowing is made so as not to intersect the dropping locus of charged raw material with the jet of oxygen-containing gas. By this method, the local erosion of refractory is prevented without damaging the merit in the smelting reduction method.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for suppressing the wear and tear of refractories when manufacturing metals or alloys, such as pig iron, by melting and reducing ores or their pre-reduced products. Regarding the method.

[Prior Art] In the production of pig iron, research is being conducted on the smelting reduction method as a method to solve the disadvantages of the conventional blast furnace method, such as raw material constraints, high equipment costs, and lack of flexibility.

Research on various smelting reduction methods has progressed to large-scale scale, and it is showing the possibility of satisfying the requirements of a mass production method that can replace the blast furnace method in terms of reaction and productivity. The furnace is capable of bottom blowing, and ore or its pre-reduced product and, in addition, carbonaceous material are charged from above the furnace, and oxygen-containing gas is blown upward using a porous nozzle.

In this method, by blocking the oxygen jet and metal bath with a large amount of slag, efficient heat generation is achieved through highly secondary combustion in an oxidizing atmosphere, and iron oxide is generated by carbon material under the slag surface or carbon in the metal. It is distinctive in that it is compatible with giving back. Since a certain degree of stirring is necessary to promote the reduction reaction and heat supply, for example, stirring is performed using bottom-blown nitrogen gas. However, if this bottom blowing is too strong, the slag will not be able to sufficiently isolate the oxidizing atmosphere from the metal, making it impossible to take advantage of the features of this method. is not preferable, and most of the raw materials must be introduced from above.

The amount of top-blown oxygen is an important factor that determines production speed, and in order to improve productivity, it is essential to blow a large amount of oxygen without hitting the metal. Therefore, the nozzle for top-blown oxygen is not one with one hole, but one with multiple holes, for example, six or more holes.

In addition, considering production efficiency, it is desirable to reduce the internal volume of the furnace as much as possible so that the inside of the furnace is in a state close to uniform mixing. It will be similar to.

Increasing the amount of oxygen gas and stirring are important factors for improving productivity, but at the same time, these conditions make the conditions harsh for refractories, so how can we suppress the wear and tear of refractories in this method of smelting reduction? The important development factor is whether or not to do so.

[Problems to be Solved by the Invention] In a typical steelmaking converter, a top-blowing oxygen nozzle having a symmetrical structure is used. However, when a symmetrically structured nozzle is used in the smelting reduction method, as shown in Figure 2, local erosion of the refractory progresses in one direction, and moreover, in a specific area. In Figure 1, 1 indicates the top-blown lance, 2 indicates the remaining refractory material, and a indicates the center position of the falling material.

As a result of various studies on the mechanism by which this phenomenon of refractory wear occurs, which is localized to specific areas, the following was discovered. In the smelting reduction method in which raw materials are mainly introduced from above, an incomparably large amount of solid raw materials moves through the furnace space compared to normal steelmaking converter operations. If the falling trajectory of this raw material intersects with the oxygen jet, the flow of the oxygen jet will be disrupted.
It was found that the high temperature and high oxygen potential area corresponding to the oxygen distribution is closer to the furnace wall than when the oxygen jet is undisturbed, and this has an effect on accelerating refractory corrosion. This phenomenon is remarkable when a carbon-containing refractory (mag carbon type or alumina carbon type) is used.

An object of the present invention is to provide a method for suppressing local melting loss of refractories while taking advantage of the characteristics of the above melting reduction method as a process.

[Means for Solving the Problems] In the present invention, in a furnace capable of blowing gas from the top and bottom, charging raw materials, that is, ore or its preliminary reduction product, and in addition to that, carbonaceous material are charged from above the furnace. When blowing oxygen-containing gas upward using a multi-hole nozzle, an asymmetrical structure as shown in Figure 1 (cross-sectional view of the nozzle) is used to prevent the falling locus of the charged raw material from intersecting the jet of the oxygen-containing gas. Nozzle 3 is used, thereby preventing local erosion of the refractory. In the figure, 4 indicates a hole.

As mentioned above, when the jet of oxygen-containing gas hits the raw materials charged from above, the jet flow is disturbed, which causes local wear of the refractory.

In the present invention, a symmetrical, for example circular, furnace cross section is used in order to maintain a uniform mixing state in the furnace without causing the oxygen-containing gas jet to easily hit the metal due to excessive bottom blowing gas. is assumed. In this case, as a method of charging ore or its pre-reduced product, and in addition to it, carbonaceous materials such as coal, if charged symmetrically from above so as to surround the top blowing lance, it is possible to charge the oxygen-containing gas jet. A solid having a lower velocity will move inside the jet, causing the jet to scatter, which is undesirable. Therefore, it is natural to feed the raw materials so that the trajectory of the solids avoids the oxygen-containing gas jet and falls as close to the periphery of the furnace as possible. Therefore, it needs to be done asymmetrically.

However, unnecessarily increasing the size of the furnace for the purpose of uniform mixing in the furnace is not a good idea from the standpoint of improving the productivity of the furnace. Furthermore, it is unavoidable that the charged raw material is scattered on the way down.

Therefore, in the present invention, the use of a top-blowing oxygen nozzle with a symmetrical structure is abandoned, and by preventing the oxygen-containing gas jet from passing through the side where the raw material falls, even if the raw material falling through the space is scattered. However, the feature is that the trajectory is prevented from intersecting with the jet. This eliminates the cause of localized wear and tear on the refractories.

Furthermore, we were concerned that blowing oxygen through a lance with an asymmetrical nozzle structure would cause another problem due to uneven flow, but it has been found that this problem does not occur when the nozzle has six or more holes. Ta.

[Example: Using a top-bottom blowing converter, ore and coal are charged from above,
Pig iron was produced by smelting reduction using top blowing of oxygen (20 QOON m3/h) and bottom blowing of nitrogen.

The composition of the raw materials used is shown in Table 1, and the refractory lining of the converter is an alkaline carbon brick. The results of measuring the wear rate of refractories are shown below when using the nozzles shown in Figures 1 (a) and (b) in the direction of the center of fall of the R material, and when using a symmetrical 9-hole nozzle for comparison. It is shown in Table 2.

Compared to the symmetrical nozzle of the comparative example, when the asymmetric nozzle of the present invention was used, the increase rate of the maximum erosion rate with respect to the average erosion rate of the refractory was smaller, and local wear of the refractory was suppressed. I understand that.

Table 1 [Effects of the Invention] The smelting reduction method to which the present invention relates has the possibility of solving the problems of the current blast furnace method, and is characterized in that it is carried out using a furnace capable of top and bottom blowing. On the other hand, when putting this smelting reduction method into practical use, there has been a problem in that it causes localized erosion of the refractory. However, by applying the method of the present invention, this problem can be solved without sacrificing the advantages of this smelting reduction method, and therefore the economic effect is large.

[Brief explanation of drawings]

FIG. 1 shows an example of the cross-sectional structure of an asymmetric top-blowing oxygen nozzle used in carrying out the present invention, in which (a) is a 6-hole nozzle and (b) is a 7-hole nozzle. FIG. 2 shows the state of refractory corrosion in a horizontal section of the secondary combustion zone of the furnace when blowing is carried out using a conventional method, that is, using a lance with a symmetrical nozzle structure. 1...Top blowing lance 2...Remaining refractory 3...Asymmetrical nozzle for oxygen top blowing a...Center position of falling raw material and 4 others Figure 1 (a) Direction of center position of falling raw material ( b) 3: Non-target nozzle for oxygen top blowing 4: Direction of the center position of the material falling through the hole Figure 1: High blowing lance 2: Remaining refractory a: Center position of the material falling

Claims (1)

[Claims] In a furnace capable of blowing gas from the top and bottom, charging materials, that is, ore or its pre-reduced product, and in addition carbonaceous material are charged from above the furnace, and the falling trajectory of the charging materials is and the jet of oxygen-containing gas so that they do not intersect.
When blowing the oxygen-containing gas upward using a multi-hole nozzle, a nozzle with an asymmetrical structure is used.
Method for suppressing refractory wear in smelting reduction smelting.