JPH0499111A - Method for supplying oxygen gas for improving productivity of smelting reduction - Google Patents

Abstract

PURPOSE:To drastically increase an oxygen gas flow rate possible to supply and to improve productivity by converting a part of oxygen jet force injected from a nozzle in a top-blowing lance into rotating force to molten material in a furnace. CONSTITUTION:In the metallurgical furnace, in which gas can be top-blown, while top-blowing the oxygen, iron raw material containing iron oxide and carbonaceous material are added. Then, reduction reaction of the iron oxide in slag 3 is progressed, and the produced molten iron alloy is settled in the molten metal 5. Further, nozzle structure of the oxygen top blowing lance 1 is regulated with two angles alpha and beta so that center axis of the nozzle does not intersect with the center axis of the lance 1. By blowing with such nozzle, rotating torque is developed to the lance 1. As this lance is mechanically restricted with a lance fixed device 7, horizontal rotating force is applied in the molten material as reaction and the rotating movement is developed. In this result, while maintaining efficient operational condition to smelting reduction, by making oxygen supplying velocity high, the productivity can be improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is a method for producing molten iron alloys such as hot metal by melting and reducing iron raw materials containing iron oxide, such as iron ore and its pre-reduced products. Regarding the method.

(Prior art) Various methods have been studied for smelting reduction, but one method that has been tested to the level closest to practical use is a method that uses top-blown oxygen shed by using slag existing in the furnace. There is a method which is characterized by blocking a metal bath in an agitated state (Japanese Patent Publication No. 50545/1983).

According to this method, re-oxidation of metal can be suppressed, so
At the same time, the reduction rate can be maintained at a high level, the secondary combustion rate in the furnace is increased, the calorific value per amount of blown acid is increased, and the amount of dust generated is reduced and the yield is improved, resulting in highly efficient operation as a whole. It can be performed.

In order to satisfy these basic conditions, it is necessary to increase the amount of slag in the furnace as much as the reaction vessel allows, to devise the nozzle shape of the top blowing lance, and to set the lance height to an appropriate value during acid blowing. A combination of blowing oxygen gas as softly as possible and reducing the amount of bottom-blowing gas to the minimum required for heat transfer and reaction progression is required (Japanese Patent Application Laid-Open No. 61-213310). .

In the production of molten iron alloys such as hot metal, it is essential that they can be produced in large quantities and efficiently. Characteristic values related to r-efficient J here include production rate per furnace volume light, yield, and refractory unit consumption.

The production rate is controlled by the oxygen gas supply rate. In order to supply a large amount of oxygen gas and maintain a high production rate per furnace volume, the only thing left to do is to determine the appropriate amount of slag and the appropriate bottom-blowing stirring conditions. It depends on the supply.

It is possible to supply a large amount of oxygen gas and prevent the oxygen jet from hitting the metal by raising the top blowing lance and dispersing the force of the oxygen jet hitting the slag surface, but in this case, There is a problem in that refractories are exposed to high temperature atmospheres and are subject to significant wear and tear. therefore,
The practical application of this method depends on the development of technology that allows the slag to block the oxygen jet from the metal even when a large amount of oxygen is supplied without raising the lance position excessively.

In order to solve these problems, the conventional approach has been to increase the number of lance nozzles and increase the nozzle angle to disperse the force of the oxygen jet hitting the slag (Japanese Patent Laid-Open No. 61-213310). This conventional top blowing lance is a type that does not generate rotational torque by gas jetting, and the top blowing lance is a hanging type.
There was no need to install any device to prevent the lance from rotating. Such a lance is defined by the intersection of the nozzle centerline with the lance centerline.

(Problems to be Solved by the Invention) However, when this type of lance is used, the force of the oxygen jet hitting the molten slag is divided into two forces: vertically downward and radially outward of the container. In this case, as the oxygen supply rate increases (that is, the force of the oxygen jet increases), the oxygen jet displaces the slag and hits the metal bath or granulated iron in the slag more easily (the secondary combustion rate increases). (observed in the form of a decrease in the amount of dust generated) or accelerated wear of the refractory, and if either of these constraints is met,
The upper limit value of the oxygen supply rate will be determined. In other words, there is an upper limit to the production rate under conditions that allow for efficient operation, and it has been difficult to obtain productivity comparable to that of a large blast furnace using this smelting reduction method.

The present invention provides a means for solving such problems and significantly increasing the amount of oxygen gas that can be supplied while satisfying the basic conditions in the present method of smelting reduction described above.

(Means for solving the problem) The nozzle is shaped so that part of the force of the ejected oxygen jet applies horizontal rotational force to the slag.

As a reaction when horizontal rotational force is generated in the slug, rotational torque is generated in the top blowing lance, so rotation of the lance is restrained mechanically.

That is, the present invention uses a metallurgical furnace capable of blowing gas from the top and bottom, adds iron raw materials containing iron oxide and carbonaceous material while blowing oxygen from the top, and melts and reduces the iron oxide to produce a molten iron alloy. In the manufacturing process, a nozzle is installed on the top blowing lance in a direction that produces rotational torque, and oxygen gas is injected in such a way that part of the force of the jet of oxygen is converted into the rotational force of the melt in the furnace. This is a method of supplying.

(Function) By the above means, as a result, out of the force of the oxygen jet,
The upper limit of the amount of oxygen gas that can be supplied can be increased by reducing the proportion of the component force in the downward direction, that is, in the vertical direction, and the component force in the direction of the refractory wall, that is, the component force directed outward in the radial direction inside the container.

Note that the horizontal rotational force generated within the slag has several side effects on the melting reduction operation.

The specific operating method will be explained below.

The metallurgical furnace used to carry out the present invention is a furnace capable of blowing gas from the top and bottom, as shown in FIG. In this furnace,
Stirring is performed by blowing a gas such as nitrogen into the melt from the bottom. This stirring maintains the temperature of the molten material uniformly, promotes heat transfer, and promotes the reduction reaction of iron oxide in the molten slag 3, which is an essential requirement in implementing this process. be.

However, if the amount of bottom-blown gas is too large, the amount of metal particles mixed into the slag 3 layer will increase, resulting in undesirable phenomena due to direct contact between the oxygen jet and the metal, i.e., a decrease in the secondary combustion rate (defined as the secondary combustion rate), and dust. An increase in generation occurs. Therefore, the appropriate range of gas injection amount is 5 to 45 Nm3/h per ton of molten metal in the furnace.

Melting reduction is carried out by adding iron raw materials containing iron oxide (iron ore, preliminary reduction thereof, etc.) and carbonaceous material while blowing oxygen upward. At this time, the generated gas such as GO is combusted by oxygen and generates heat, and the reduction reaction of iron oxide in the slag proceeds with the carbon dissolved in the carbonaceous material and metal. As a result, a molten iron alloy in which carbon is dissolved into the generated metal is obtained, and this is precipitated in the metal bath 5.

If the temperature of the molten material becomes too high, it will adversely affect the wear and tear of the refractory 2, so by appropriately adjusting the relationship between the blowing acid rate and the raw material supply rate, the temperature of the molten material can be kept at 20 to 150 degrees higher than the melting point of the metal. Try to keep the temperature within a range of ℃ higher.

The molten slag 3 in the furnace is important in the present invention as it blocks direct contact between the oxygen jet and the metal bath 5. Therefore, the larger the amount of slag 3, the more advantageous it becomes to the operation of this process, and the oxygen gas supply rate can be increased. At least, the amount of slag 3 needs to be 360 kg or more per 1 ton of metal present in the furnace.

It should be noted here that the large amount of slag 3 present in the furnace during operation means that the amount of metal 1 ton
This does not mean that more slag will be generated per hit.

This is because the necessary amount of slag remains in the furnace when the generated metal is discharged outside the furnace, and by performing the next heat operation after discharging the remaining slag, the furnace can be heated without increasing the amount of slag produced. This is because the amount of slag 3 inside can be adjusted arbitrarily.

In order to contain a large amount of slag in a reaction vessel with a predetermined volume and prevent it from flowing out of the furnace, it is necessary to coexist with carbon material 6 to coalesce the fine bubbles in the slag and promote the dissipation of bubbles 4. . The amount of carbon material required for this is 5 to 50w of the weight of the slag.
t%.

Depending on the conditions, if a large amount of carbonaceous material 3 is not allowed to coexist, slag bubbling may occur, especially in large furnaces, where the carbonaceous material inside the furnace is blown into the surrounding area of the furnace. This is because the ratio of the carbonaceous material 3, which helps promote the coalescence of the fine bubbles 4, decreases. On the other hand, if too much carbonaceous material is present in the furnace, the effective internal volume of the furnace becomes small, which is not preferable in terms of burning carbon in an oxidizing atmosphere.

Therefore, it is desirable to reduce the amount of carbonaceous material in the furnace to suppress slag foaming as much as possible, but this requirement can be achieved as a side effect by implementing the oxygen gas supply method of the present invention, as described later.

FIG. 1 shows the nozzle structure of an oxygen top-blower lance used to practice the present invention. The feature is that the center axis of each nozzle does not intersect with the center axis of the lance 1.

The structure of this nozzle consists of two angles α and β as shown in the figure.
defined by.

When blowing with such a nozzle, a rotational torque approximately proportional to Qv stnβ is generated in the lance 1. However, Q is the acid blowing rate and V is the nozzle tip gas flow rate. However, since the nozzle is mechanically restrained by the lance fixing device 7 so as not to rotate, a horizontal rotational force is applied to the melt as a reaction, causing rotational movement.

At this time, the rotational movement of the melt means that the force directed downward and toward the refractory wall, which is a problem when implementing this smelting-reduction method, is reduced among the energy of the oxygen jet. means. From this point on, it becomes possible to control the oxygen supply rate.

In order to increase the energy used for horizontal rotation, it is advantageous to have angles α and β as large as they are close to 90°, but from the perspective of reducing the local wear rate of the refractory 2, As can be seen from 1, it is desirable that α be in the range of 15 to 25° and β be in the range of 30 to 70''.

A feature of the present invention is that β is 30° or more when compared with a normal nozzle structure.

By using a nozzle with such a structure and generating horizontal rotational force in the melt (slag 3), the following effects are produced as a secondary effect.

■ Disperse the carbonaceous material that had accumulated around the furnace to create slag 3.
By involving the slag in the furnace, foaming of the slag can be suppressed with a smaller amount of carbon material in the furnace than in conventional methods, and heat transfer by the carbon material can be promoted.

(2) By reducing the required amount of carbon material in the furnace (for example, 15 wt% or less of slag), direct combustion and scattering of carbon material can be suppressed, and the carbon material consumption rate can be reduced.

By combining the above effects, it becomes possible to increase the oxygen supply rate and increase productivity while maintaining effective operating conditions for melt reduction.

(Example) Using a top-bottom blowing converter as shown in Figure 2, a test was conducted to produce hot metal using iron ore, carbonaceous material (coke), and quicklime as raw materials. Common conditions for various tests are shown below.

(1) Iron ore-m-hematite series, T, Fe-67k.

Particle size: 0.5+++m or less is continuously added from the side hole 8 of the 98wtX furnace shoulder (2) Carbon material---Coke, T, C-87 particle size;
Continuous addition of 90 slags from above zero for 5 mm or more (3) Slag condition Adjustment of temperature to CaO/5i02-1.2 by adding quicklime Temperature: 1420 to 1450°C Amount of slag present in the furnace: 420 kg/metal root (4) Metal condition Ingredients: C-4,596, Temperature: 1420-1450°C (5) Bottom blowing conditions N2: 35Nm3/h4-metal (6) Top blowing conditions Number of nozzle holes: m-8 Nozzle diameter: 12mm In addition, other The test was conducted under various conditions as shown in Table 1. Table 1 also shows the operational results at that time.

Therefore, by comparing the conventional method, the present invention A-E, and the comparison A-C, it was found that the present invention A-E has lower secondary combustion rate, dust generation amount, carbon material consumption rate, refractory wear amount, and productivity. It can be seen that it is also excellent.

(Q) (Effect of the invention) By carrying out the method of the present invention, it becomes possible to efficiently produce molten iron alloys such as hot metal on a mass production scale by the smelting reduction method, resulting in an industrial and economical The effect is great.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the nozzle structure of a top-blown oxygen lance used in carrying out the present invention, in which (a) is a sectional view, (b) is a plan view, and FIG. It is a diagram showing an outline of the metallurgical furnace used. 1... Lance 2... Refractory 3... Slag 4... Air bubbles 5... Metal bath 6
...Charcoal material 7...Lance fixing device 8...Site hole for adding fine ore

Claims (1)

[Claims] 1. In the process of manufacturing molten iron alloy by adding iron raw materials containing iron oxide and carbonaceous materials, melting and reducing the iron oxide, using a metallurgical furnace capable of top-bottom blowing gas, while blowing oxygen from top to bottom. , an improvement in productivity in smelting reduction characterized by installing a nozzle in a direction that produces rotational torque on the top blow lance and converting a part of the force of the ejected oxygen jet into the rotational force of the molten material in the furnace. Oxygen gas supply method for