JPH0499809A - Smelting reduction operating method - Google Patents

Abstract

PURPOSE:To control erosion of a refractory and to reduce the development of carbonaceous material series dust and CO2 by adding iron oxide-contacting raw material and the carbonaceous material while top-blowing oxygen and constituting the upper space of a reaction vessel for producing a smelting reduction iron alloy of a noncarbon monolithic refractory wall. CONSTITUTION:At the time of producing iron alloy by using a metal-lurgical furnace being possible to top- and bottom-blow gas and adding the iron- containing raw material and the carbonaceous material while top-blowing oxygen and executing the smelting reduction, the upper state from the molten material in the reaction vessel is constituted at the refractory wall made by combining the non-carbon monolithic refractory, e.g. almina quality, and metal pipes for cooling, in which mist of gas and water, etc., can be allowed to flow in.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a process for manufacturing a molten reduced iron alloy such as hot metal by melting and reducing iron oxide-containing raw materials such as iron ore or its pre-reduced product. The present invention relates to a method of reducing the amount of 002 generated by reducing the amount of material wastage and converting exhaust gas.

(Prior art) Various methods have been studied for smelting reduction, but one of the methods that has been tested to the level closest to practical use is a method that uses slag existing in the furnace to There is a method which is characterized by a blown oxygen shed and blocking of a metal bath in an agitated state (Japanese Patent Publication No. 50545/1982). According to this method, metal reoxidation can be suppressed, so the reduction rate can be maintained at a high level, and at the same time, the secondary combustion rate in the furnace can be increased to increase the calorific value per amount of blown acid, and the amount of dust generated can be reduced. Since the production efficiency is reduced and the yield is improved, it is possible to perform highly efficient operations as a whole.

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 adjust the lance height to an appropriate value during acid blowing. It is necessary to combine the following three settings: to make the oxygen gas blow as soft as possible, and to minimize the bottom blow gas (Japanese Patent Laid-Open No. 61-213310).
issue).

In the production of molten reduced iron alloys such as hot metal, it is essential to be able to produce them in large quantities and efficiently to reduce production costs as much as possible. Characteristic values related to r efficient 1 here include the production rate per light volume of the furnace, the unit consumption of coal, the unit consumption of refractories, and the like.

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, what method should be used to supply a large amount of oxygen gas under the appropriate amount of slag and under appropriate bottom-blowing stirring conditions? It is important to prevent the oxygen jet from hitting the metal directly.

To address these issues, 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.

Regarding the coal consumption rate, it is important to increase the secondary combustion rate in the furnace from a thermal standpoint, and the key is to suppress the oxygen jet from coming into contact with the metal and reacting. However, when the secondary combustion rate is high, the atmospheric temperature inside the furnace tends to rise, which becomes a severe condition for wear and tear of the refractory.

Several types of refractories have been considered in the past, but among these, maguro bricks and graphite-containing bricks such as magcarbon or alumina carbon are considered to have a high possibility of practical use. There is.

However, although maguro bricks have relatively high slag erosion resistance, they have problems in that chromium is eluted and contaminates metal and slag, and they also have strong spalling properties. In contrast, graphite-containing bricks are less likely to spall and have relatively high thermal conductivity. By utilizing this property, it is possible to cool the bricks using various methods to lower the surface temperature, form slag deposits on the refractory surface, and suppress its wear (Japanese Patent Laid-Open No. 81-67708).
issue). However, using water, which is the cheapest and most effective means of cooling, accelerates oxidation loss of graphite, a key component of bricks. The problem is therefore that the use of water has to be avoided, resulting in relatively high costs for cooling. If the graphite in the bricks is oxidized and lost by using water for cooling, the thermal conductivity of the bricks decreases and the slag adhesion layer cannot be maintained stably.

Note that alumina-based unstructured refractories are available as refractories that do not contain graphite, but if they are used to construct a furnace using the normal method, they are highly erodible by slag, and the surface is cooled to form a slag adhesion layer. If you try to promote this, there is a problem in that it is easy to cause spalls.

As described above, until now, no refractory has been established that is fully satisfactory in terms of both suppression of wear rate based on spall resistance and cost reduction.

On the other hand, in the smelting reduction method using coal as a raw material, more than half of the dust is derived from carbonaceous materials. Since this carbonaceous dust is expensive to separate and reuse, it is desired to reduce the amount generated. However, the current situation is that there is no efficient method for reducing particles, especially those with fine particle size.

Furthermore, recently, there has been a strong call for reducing the amount of 002 generated due to the issue of global environmental conservation. In the steel manufacturing industry, attempts are being made to reduce coal consumption as much as possible by, for example, increasing the secondary combustion rate mentioned above.
There is a limit to the reduction in the amount of CO□ generated.

In order to drastically reduce the amount of 602 generated, it is considered to fix 002 in the exhaust gas generated from the iron manufacturing process and convert it into something that is effective and easy to store. As a method for achieving this purpose, it is considered to be a promising method to react CO2 and H2 to synthesize methanol (CH301()).

However, the economic efficiency in this case depends on how cheaply to obtain H2 and reduce the cost of the methanol synthesis process, and as long as the system relies on H2 obtained from outside the system, it is difficult to put it into practical use. It is in.

(Problems to be Solved by the Invention) In view of the above-mentioned current circumstances, the present invention aims to suppress the wear and tear of refractories during melt reduction, reduce carbonaceous dust, and reduce carbonaceous material.
This provides a method for systematically and economically reducing the amount of O□ generated.

(Means for solving the problem) Using a metallurgical furnace capable of blowing gas from the top and bottom as a reaction vessel, a raw material containing iron oxide and a carbon material are added while blowing oxygen from the top, and the raw material is melted and reduced. In the process of producing a molten reduced iron alloy, the space above the molten material in the reaction vessel is filled with a monolithic refractory that does not contain carbon and a metal tube that allows gas to flow into the furnace. The space is constructed with refractory walls, and water or mist is supplied into the space during operation. On the other hand, the generated exhaust gas from the reaction vessel is pressurized, and GO, C (hL) contained in the gas are reacted using the sensible heat of this exhaust gas as a heat source to generate methanol. Methanol is separated from the exhaust gas and the remaining gas is blown into the reaction vessel.By implementing the above steps, it is possible to simultaneously reduce the amount of refractory wear, effectively utilize sensible heat, and reduce the amount of 002 generated. can do.

(Operation) The entire process flow of the present invention is shown in FIG. Based on this, the present invention will be explained according to a specific operating method.

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 nitrogen or a process product gas after methanol removal, which will be described later, into the melt from the bottom. Stirring maintains the temperature of the molten material uniformly, promotes heat transfer, and promotes the reduction reaction of iron oxide in the molten slag, which is an essential requirement in implementing the present invention. . However, if the amount of bottom blowing gas is too large, the amount of metal particles mixed into the slag layer will increase, and undesirable phenomena such as secondary combustion rate will occur due to direct contact between the oxygen jet and the metal. The appropriate range of the amount of gas blown is 5 to 458 m3/h per 1 amount 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. The carbonaceous material and generated gases such as GO are combusted by oxygen and generate heat, and the carbon dissolved in the carbonaceous material and metal causes a reduction reaction in the slag to proceed, resulting in the production of metal, into which carbon is dissolved. A molten iron alloy is obtained by
This settles into the metal bath.

The molten slag in the furnace is important in the present invention as it blocks direct contact between the oxygen jet and the metal bath. The larger the amount of slag, the more advantageous it will be to operate this process. In other words, by increasing the oxygen gas supply rate,
Even if the production speed is increased, it is possible to maintain good operational performance, such as secondary combustion rate, amount of dust generation, and coal consumption rate. For this purpose, it is necessary that the slab weigh at least 360 kg or more for every 1 ton of metal present in the furnace. However, the fact that more slag is present in the furnace during operation does not mean that more slag will be generated upon hitting metal. This is because by performing the next heat operation after leaving the necessary amount of slag in the furnace when discharging the generated metal out of the furnace,
This is because the amount of slag in the furnace can be adjusted arbitrarily without increasing the amount of slag produced.

In order to contain a large amount of slag in a metallurgical furnace of a predetermined volume and prevent it from flowing out of the furnace, it is necessary to coexist with carbonaceous material to coalesce the fine bubbles in the slag and promote the dissipation of the bubbles.

The amount of carbon material required for this purpose is 5 to 50 wt% of the slag weight.
It is.

The amount of lime added is adjusted so that the slag composition satisfies the condition of the following equation (1).

(0cao) / (%1Si02) -0.9~1.4
- (1) When XCaO is higher than this condition,
Since the melting point of the slag is too high, stable operation cannot be achieved unless the temperature of the molten material is raised, and raising the operating temperature lowers the thermal efficiency and increases the rate of wear of the refractory, which is undesirable. The appropriate temperature of the melt when the slag composition is appropriate is 135
The range is 0-1450'e.

On the other hand, if 1lkcaO is lower than this condition, the slag will foam violently, making it impossible to sufficiently increase the oxygen gas supply rate. Furthermore, the rate of wear and tear of the refractory increases, which is not preferable.

In addition, as for the addition method of lime, at least 2 of the total addition amount is
It is desirable to add 0% or more of powdered limestone by spraying it onto the winter-resistant material in the space above the melt. This operation lowers the temperature of the refractory wall where the lime is scattered and adhered.
The melting point increases, thus promoting the formation of a slag coating.

The space above the melt, that is, the part in contact with the secondary combustion atmosphere, requires special measures because the refractories of metallurgical furnaces are under particularly severe conditions. In the present invention, the refractory of this part is constructed of a combination of a carbon-free monolithic refractory and a metal tube through which gas can flow, as shown in FIG.

Alumina is a material for monolithic refractories. Refractories containing graphite are resistant to spalling, but when directly cooled with water, the oxidation of graphite is accelerated by steam. . The spalling problem caused by not containing graphite is overcome by using irregularly shaped bricks instead of fired bricks and combining this with a cooling metal pipe.

That is, as shown in Figure 3, the metal tube embedded in the refractory cools the metal tube and the refractory by passing gas or water mist, and the In the case of cracked parts, for example, structural spall parts caused by slag erosion, the metal tube, which has been prevented from decreasing in strength by this cooling, suppresses its peeling.

As the gas passed through the metal tube, a process gas after methanol removal or nitrogen, which will be described later, is used. Water or mist is added to the space above the melt in the furnace. Addition can be done by installing a water addition port above the oxygen gas spout of the top-blown lance, by providing a lance exclusively for water addition, or by passing a water mist through the aforementioned metal pipe penetrated into the refractory. The addition may be carried out by one method or by a combination of two or more methods. The amount of water added is determined by the following formula (2) depending on the volatile content of the carbonaceous material, the secondary combustion rate in the furnace, and the blowing acid rate at the time of addition to the metallurgical furnace, that is, the smelting reduction furnace. The range satisfies the following conditions.

(Amount added as H2O) [kg/h] = (0,3
〜7.8)・10−′・(Blowing acid rate [Nn+′/hl)
(Carbonaceous material (7) VM content [1]-13)・(Secondary combustion rate [961-20)... (2) The effect of water addition is first determined by the equilibrium constant. Advancing the gas reaction in the following equation (3) to the right by increasing the partial pressure by 8.0, H2O+ GO= H2+
CO2... (3) Second, the reaction H2O+C=82+GO... (4) between water vapor and scattered carbonaceous dust is promoted to generate hydrogen and reduce carbonaceous dust, and the above heat absorption is achieved. The sensible heat of the exhaust gas is used in the reaction to lower the gas temperature.
The aim is to suppress wear and tear on refractories.

In this manner, the high-temperature exhaust gas discharged from the smelting reduction furnace is treated by being led to a reaction tube of an apparatus as shown in FIG. 4, for example, to cause a methanol production reaction as shown in the following equation (5).

At this time, iron oxide dust contained in the gas acts as a catalyst for these reactions.

Although the methanol production reaction of formula (5) is an endothermic reaction, the sensible heat of the exhaust gas from the melting reduction furnace can be used as the reaction heat.

The gas after the methanol synthesis treatment that has gone through the above process is depressurized and cooled to separate methanol and water.

In addition, the remaining process gas is mainly used as fuel gas outside the system, but some of it is passed through the cooling metal pipes embedded in the refractories mentioned above or from the bottom of the furnace as gas for stirring the melt in the smelting reduction furnace. It can be blown inside. By using this process gas, the following effects can be obtained compared to a method using ordinary nitrogen.

■ It has the effect of lowering the coal consumption rate in the smelting reduction process.

■ The nitrogen content of the product molten reduction metal can be lowered.

■ Since the nitrogen content in the fuel gas is low, calories can be increased.

■ Increases the cooling effect of refractories and the effect of suppressing refractory wear.

As described above, the present invention first aims to reform the gas by injecting water into the melting reduction furnace, and creates a refractory structure that can withstand water injection and can significantly extend its life by injecting water. What we did was to synthesize methanol inexpensively from reformed gas using dust as a catalyst and the sensible heat of exhaust gas as reaction heat.After methanol was separated from the gas after methanol synthesis, the remaining gas was transferred to a smelting reduction furnace. By injecting 002 into 002 and systematically combining them, it is possible to manufacture iron alloys by smelting reduction smelting at low cost, significantly reducing the amount of 002 released outside the system, and reducing by-product energy and gas. It is distinctive in that it is preserved and converted into something that is easy to use.

(Example) A hot metal production test was conducted using iron ore, coke, and coal using a top-bottom blowing converter type reaction vessel shown in FIG.

First, as a feature of the furnace body structure, the upper third of the height direction is lined with alumina castable with 4 mm diameter stainless steel vibrator embedded in each 78 cm2 of the furnace inner wall. 600 yen of water per bottle
g/h, CO262% as carrier gas, Go 32
% process gas was flowed. Also, the lower 2/2 in the height direction
3, alumina carbon bricks were placed in the inner arch.

The iron ore used was hematite-based iron ore containing 67% T and Fe, and 96 wt% of the iron ore had a particle size of 0.5 mm or less, and was continuously added through a side hole in the furnace layer.

As the carbon material, coal char (86% fixed carbon) with a volatile matter (VM) of 3% was continuously added from the side hole of the furnace layer.

In addition, the flux has a slag CaO/5i02 of 1.
Similarly, quicklime was added from the side bowl of the furnace layer so that the amount was 2.

The top-blowing lance consisted of a 12-hole lance with a diameter of 8 mm, and a total of 2000 ONm3/h of oxygen was soft-blown toward the slag surface from the top-blowing lance. In addition, separate from this oxygen system, water misted with process gas was sprayed onto the refractory surface.

On the other hand, a process gas of 35 Nm3/h was blown into the metal from the bottom blowing tuyere.

The operating conditions of the smelting reduction furnace are such that the amount of residual slag in the furnace is 420
kg/l-metal or more, and the amount of carbonaceous material remaining in the furnace was 10 to 25 wt% of the slag weight.

When the smelting reduction furnace was operated under the above conditions,
The composition of the gas discharged from the smelting reduction furnace is GOIn, c
o, 26% F, 1 (22496, I202H), and also contained N2, etc. Also, the refractory wear rate of this smelting reduction furnace was 0.9 am in the upper third of the height direction.
/h, and the lower two-thirds in the height direction was 0.7 mm/h.

Next, methanol synthesis was carried out by introducing the gas discharged from the above-mentioned melting reduction furnace into the apparatus shown in FIG. The gas composition at the time it is supplied to this device is CO26! , co, 3
H1) I234.

First, the pressure of this gas is increased to 10 atmospheres, and the temperature is 400±
The temperature was raised to 50° C. to cause a methanol production reaction, and the methanol-containing gas thus synthesized was then cooled under reduced pressure to separate methanol and water. Here, in order to ensure temperature conditions during methanol synthesis, the sensible heat of the exhaust gas from the smelting reduction furnace was used to control the temperature to an appropriate level by adjusting the amount of water and process gas blown into the reactor. Note that the gas composition after separating methanol and water at the outlet of the apparatus was CO262LCO321.

A part of the gas after methanol separation is
As described above, the process gas was used as a carrier gas for bottom blowing or water blowing into the melting reduction furnace, and the remainder was led out of the system as fuel gas.

As described above, according to the present invention, the wear rate of refractories in the upper part in the height direction of the smelting reduction furnace can be made close to the wear rate in the lower part, and as a result of fixing CO2 in the form of methanol, the CO2 itself It can be seen that the amount of generation can be reduced.

(Effects of the Invention) By implementing the present invention, it is possible to reduce manufacturing costs, save energy, and reduce the amount of CO2 generated when producing molten iron alloys such as hot metal by the smelting reduction method. , has a large environmental effect.

[Brief explanation of drawings]

FIG. 1 is a process flow diagram of the entire present invention, FIG. 2 is a diagram showing an example of the smelting reduction furnace used in the present invention, and FIG. 3 is a diagram showing the refractory structure of the inner wall of the upper space of the smelting reduction furnace according to the present invention.
Further, FIG. 4 is a diagram showing an apparatus for producing methanol by reacting the smelting reduction furnace exhaust gas containing CO2 and H2. 4 others

Claims (1)

[Claims] 1. Using a metallurgical furnace capable of blowing gas from the top and bottom as a reaction vessel, a raw material containing iron oxide and a carbonaceous material are added while blowing oxygen from the top, and the raw materials are melted and reduced. In the process of producing iron alloys, the space above the molten material in the reaction vessel is filled with a refractory made of a combination of a monolithic refractory that does not contain carbon and a metal tube that allows gas to flow into the furnace. A melting reduction operation method characterized by forming a wall and supplying water or mist into the space during operation. 2. The smelting reduction operation method according to claim 1 includes the step of pressurizing the generated exhaust gas from the reaction vessel and reacting the gas components in the exhaust gas using the sensible heat of the exhaust gas as a heat source to generate methanol. A melting reduction operation method characterized by adding. 3. The smelting reduction operation method according to claim 2, characterized in that methanol and water are separated from the exhaust gas after methanol production, and the remaining gas is blown into the reaction vessel.