JPH0310030A - Treating furnace for by-product in process for producing stainless steel - Google Patents

Abstract

PURPOSE:To provide the treating furnace which effectively utilizes the latent heat of the waste gases of a vertical furnace for treating dust and the like within the same furnace so as to additionally lower the cost of the treatment by providing tuyeres for blasting air or high-temp. oxygen-enriched air on the furnace body in the position upper than tuyeres for feeding powder materials into the furnace. CONSTITUTION:Of the by-products contg. various kinds of valuable metals generated in the process for producing stainless steels, the lumped materials, such as slag, are charged to the furnace 1 from a charging port 2 at the furnace top and the powder materials, such as dust, from the main tuyeres 3, respectively and are respectively and simultaneously treated. The valuable materials existing in the form of oxides are simultaneously reduced to a molten metal. The charging of scrap and alloy iron in combination as the furnace top charge and the simultaneous melting thereof are possible as well. The molten ferrometal which is reusable as the stainless steel base metal is recovered from the above-mentioned byproducts. The latent heat of the waste gases of the furnace is effectively utilized in the furnace 1 by the blasting from the upper tuyeres 12, by which the economical operation is executed with high efficiency.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to reducing the amount of carbon that accompanies in by-products such as converter slag, sludge, and dust) generated during the stainless steel manufacturing process.
The present invention relates to a vertical melting furnace that collects valuable metals such as r, Ni, and Fe in bulk.

[Background of the invention]

Converter slag, sludge 9 dust, etc. generated in the various processes of stainless steel manufacturing contain valuable metals such as Cr, Ni, and Fe in the form of oxides, but it is necessary to reduce them and recover the valuable metals. is important from the perspective of resource conservation. For this reason, a method has conventionally been generally practiced for converter slag by adding ferrosilicon to the molten slag to reduce and recover Cr, Fe, etc. in the slag.

In addition, a method of reducing valuable metals from sludge and dust using an electric furnace was proposed.

However, these methods use expensive ferrosilicon, or the energy for smelting is electricity.
There are problems such as high return and recovery costs, and
Since this method does not involve the bulk treatment of valuable metal-containing substances generated at smelters, it was necessary to treat each source separately.

JP-A-60-162718, JP-A-62-54007, JP-A-62-16780 all filed by the same applicant
Publication No. 8.

JP-A-62-167809, JP-A-63-103
No. 012, Japanese Unexamined Patent Publication No. 63-103013, etc., proposed a method for producing Cr hot metal, which is the base metal of stainless steel, in a vertical furnace having two upper and lower tuyeres below.

In addition, Japanese Patent Application No. 63-63514 and Japanese Patent Application Laid-open No. 63-121872 filed by the same applicant describe the treatment of the above-mentioned converter slag and dust in a similar vertical furnace. No. 32384 proposed equipment suitable for the same treatment method.

For example, in Japanese Patent Application No. 63-32384, the intention was to obtain valuable metals by processing dust and converter slag in a vertical furnace with two stages of tuyere, upper and lower. I experienced something like this. That is, in the case of this furnace, the latent heat of the gas discharged from the furnace is high, so the energy efficiency is not good, and the coke ratio required for processing dust etc. has to be increased. In particular, it was found that in order to raise the temperature of the ferrometal molten metal obtained by this process to over 1500'C, the coke ratio had to be considerably high, leading to an increase in the cost of processing dust and a decrease in productivity. .

On the other hand, Japanese Patent Publication No. 59-45725 discloses a vertical furnace for melting and reducing powdery ore instead of by-products produced in a smelter.

Even in this furnace, the latent heat of the waste gas is high.1 Unless the waste gas is used effectively for preliminary reduction of granular ore, the coke ratio must be high.

[Object of the Invention] Therefore, in view of the above-mentioned actual situation, an object of the present invention is to further reduce processing costs by effectively utilizing the waste gas latent heat of a vertical furnace for processing dust in the same furnace. It is in.

[Structure of the invention]

The present invention is a vertical melting furnace for collectively processing valuable metal-containing by-products such as converter slag, sludge, and dust generated in the manufacturing process of stainless steel, and among the by-products, the lumpy substances are coke and A vertical melting furnace that is charged from the top together with other raw materials (e.g. scrap and/or ferroalloy), and the powdered material is fed into the furnace through the tuyere at the bottom of the furnace together with high-temperature oxygen-enriched air. A tuyere for blowing air or high-temperature oxygen-enriched air is provided in the furnace belly at a position above the tuyere for feeding the powdery material, and a tuyere for blowing air or high-temperature oxygen-enriched air is provided at a position below the tuyere for feeding the powdery material. The present invention provides a processing furnace for by-products of stainless steel manufacturing process, characterized in that a tuyere for blowing high-temperature oxygen-enriched air is provided in the belly.

That is, 1. unlike the conventional vertical furnace described in the above-mentioned publications, the present invention has a tuyere for blowing air or high-temperature oxygen-enriched air in the furnace belly located above the tuyere for feeding powdery material. There is a basic feature in this point. The upper tuyere is preferably provided in multiple stages in the vertical direction.

[Specific disclosure of the invention]

FIG. 1 shows the entire equipment of a processing furnace according to the present invention, where l is a vertical furnace body, which has a furnace top charging inlet 2 at its top and also serves as a powder raw material inlet at its lower part. This is a shaft furnace with a main tuyere 3. A plurality of gas exhaust ports 4 are provided in the furnace belly slightly below the furnace top charging inlet 2, and these are connected to an exhaust header 5 surrounding the furnace. Main tuyere 3 is 1
In the example shown, four are arranged at equal intervals at the same height level,
These are connected to the main tuyere header 6 surrounding the furnace. High-temperature oxygen-enriched air is supplied to the main tuyere header 6 via an air pipe 7. That is, in the process of sending air to the hot air stove 9 by the blower 8, oxygen 1O is enriched, and this oxygen-enriched air is heated in the hot air stove 9 and then supplied to the air pipe 7. On the other hand, during the air supply process from the main tuyere header 6 to each main tuyere 3, the powdered raw material in the hopper 11 is continuously entrained in the high-temperature oxygen-enriched air stream.

In such a vertical furnace, the present invention provides air or high-temperature oxygen-enriched air supply layer tuyeres (
12 (hereinafter referred to as upper tuyere), and a main tuyere 3.
A tuyere (hereinafter referred to as the lower tuyere) 13 for supplying high-temperature oxygen-enriched air is installed in the lower part of the furnace belly, and the tuyeres 13 are used to remove converter slag, sludge, and dust generated during the stainless steel manufacturing process. Among the valuable metal-containing byproducts, lumpy substances are charged into the furnace through the furnace top charging port 2 together with coke and other raw materials (such as scrap and ferroalloy), and powdery substances among the byproducts are charged into the furnace through the main tuyere 3. It is designed to be fed into the furnace.

In the illustrated example, the upper tuyere 12 is vertically arranged with 12a, 12
b.

12c are provided in three stages, and in each stage, four pieces are installed at equal intervals in the circumferential direction.

Each stage is connected to a common tuyere header 14, and air is supplied to this tuyere header 14 from a blower 15. In addition, high-temperature oxygen-enriched air can also be supplied to the tuyere header 14 through a branch air pipe 16 branched from the air pipe leading from the hot air stove 9 to the Doba Rohender 6. This upper tuyere 12a.

? 2b and 12c are located at heights a and b from the main tuyere 3 in a model furnace with an inner diameter A of 3 m, which was conducted by the present inventors.

C was installed at 4 m, 3.5 m, and 3 m, respectively. Also, the height d from the main tuyere 3 to the exhaust port 4 is 6
It was set as m.

On the other hand, in the embodiment, eight lower vanes 13 are arranged at equal intervals in the two circumferential directions with a distance eζ1 m from the main tuyere 3,
These are connected to a tuyere header 17 that circulates outside the furnace, and high-temperature oxygen-enriched air is supplied to this tuyere header 17 via an air supply pipe 17 that branches from an air supply pipe 7 to the main tuyere 3. . Unlike the main tuyere 3, no powder material is injected into this lower tuyere 13, and only high-temperature oxygen-enriched air is sent into the furnace.

Note that while the furnace is in operation, the exhaust fan 20 is driven to forcibly exhaust the exhaust gas inside the furnace from the exhaust port 4, but this exhaust gas path 21 is equipped with a dust remover 22 and a hot blast furnace 9, and the exhaust gas is After the dust is removed by the dust removal device 22, the air is introduced into the hot air stove 9. In FIG. 1, reference numeral 23 indicates a tapping port for tapping the molten slag and molten metal accumulated at the bottom of the furnace, and reference numeral 24 indicates a charging packet for conveying and charging raw material to the charging port 2 at the top of the furnace.

(Function) According to the processing furnace of the present invention, among various valuable metal-containing by-products generated in the stainless steel manufacturing process.

Clumped materials such as slag are charged into the furnace through the top charging port 2, and powdered materials such as ducts, sludge (this is dried powder), and slag powder are charged into the furnace through the main tuyere 3. By doing so, the coke can be treated all at once, and the valuable substances present in the form of oxides in these by-products are reduced to molten metal all at once by the combustion heat of the coke charged from the top charging port and its reducing action. In addition, scrap and alloyed iron can also be charged as top charges, and these can also be melted at the same time. This recovers ferrometal melt from the smelter by-product that can be used again as stainless steel base metal.

At this time, the latent heat of the furnace exhaust gas is effectively utilized within the furnace by blowing air from the upper tuyere 12, allowing economical and highly efficient operation. That is, in the present invention, a part of the Co gas generated by reduction of dust and combustion of coke is combusted as shown in equation (1) using air or high-temperature oxygen-enriched air blown from the upper tuyere 12. Accelerates melting in the furnace.

2 CO1〇□-2CO,... (1) This upper tuyere 1
The effects of No. 2 will be explained below in comparison with a furnace without this.

FIG. 2 schematically shows the situation inside the furnace when processing is carried out in a vertical furnace without an upper tuyere, such as the one proposed in Japanese Patent Application No. 63-32384. Massive converter slag charged from the top of the furnace 30. Steel scrap and ferroalloy 31 are heated together with coke 32 in the upper part of the furnace by coke combustion gas 33 rising from below, and become converter slag 30.
．． The steel scraps and the ferroalloy 31 become molten during the descent and melt down. In the process, the oxides in the slag are reduced. The molten ferrometal 34 thus generated drips to the bottom.

On the other hand, when the coke 32'' reaches the level of 1 coke, the carbon in the coke burns as shown in equation (2) by the high-temperature oxygen-enriched air that is blown into the furnace together with powdery substances (dust). By C, Cr, Ni,
According to experiments by the present inventors, metal oxides such as Fe are reduced by the reactions of formulas (3) to (5).

It has been found that these reduction reactions proceed rapidly and are generally completed in the coke combustion zone. The molten ferrometal produced by reduction drips into the lower part of the furnace.

2C+0□=2CO...(2) Cr, Os+3C=2Cr+3CO・ ・ (3) Ni
O+ C= Ni+ CO'...(4) Fe
O0C=Fe0CO・・・・(5) Since ferrometal contains Cr, its melting point is higher than that of normal blast furnace hot metal, etc., and during transportation from the processing furnace to another process. In order to prevent the ferrometal from solidifying, it is necessary to keep the temperature of the ferrometal in the processing furnace at least 1450°C or higher, preferably 1500°C or higher. However, a portion of the sensible heat of the combustion gas generated in the coke combustion zone is consumed for reducing dust;
The temperature of the combustion gas becomes lower than when no dust is blown into it, and the degree of superheating of the ferrometal by the combustion gas correspondingly decreases.

For this reason, it is necessary to increase the coke ratio to raise the temperature of the ferrometal.However, as shown in equation (2), the coke is only incompletely combusted, and the Since the high-calorie CO gas is directly discharged outside the furnace, thermal efficiency is poor. Therefore, in order to raise the temperature of the ferrometal, it is necessary to considerably increase the coke ratio. Of course, if coke can be combusted in a state close to complete combustion, thermal efficiency will improve and the coke ratio can be expected to be reduced, but on the other hand, (3) to (5)
Since the reduction reaction of the formula is inhibited, the original purpose of the dust treatment furnace cannot be achieved.Therefore, in order to satisfy both the requirements of reducing dust and raising the temperature of ferrometal, it is necessary to increase the coke ratio. I have no choice.

The processing furnace of the present invention satisfies both of these requirements at the same time and can reduce the coke ratio. FIG. 3 schematically shows the reaction in the processing furnace of the present invention and the temperature distribution in the height direction. In the area at the bottom of the processing furnace where the reduction reaction (Equations (3) to (5)) is progressing, the coke is burned with high-temperature oxygen-enriched air as in the reaction of Equation (2), so that the reduction reaction is not inhibited. do it like this. Then, in the upper part of the furnace where the reduction reaction does not occur, a part of the CO gas generated by the combustion reaction of the coke is combusted (secondary combustion) with air or high-temperature oxygen-enriched air as shown in equation (1). As shown in the figure, the temperature of the gas flowing in the furnace increases significantly due to secondary combustion, which causes the charging material to Since the metal is superheated and falls to the bottom of the furnace, the temperature of the ferrometal and coke can also be raised. As a result 2, in the treatment furnace of the present invention, under the condition that the coke ratio is constant,
It is possible to obtain ferrometal at a high temperature, and conversely, when trying to obtain ferrometal at a constant temperature, the consumption of coke, which is a heat source, can be reduced.

However, the position of the upper tuyere 12 for blowing air or high-temperature oxygen-enriched air to advance the reaction shown in (1) is not limited to any position.

When the coke temperature rises, the COz gas generated by the reaction in equation (1) reacts with C again as shown in equation (6), and the reaction progresses in the same way as in equation (2). However, if the temperature of the coke falls below 900'C, the reaction shown by equation (6) will not proceed as expected.

coz+c=2co (6) Therefore, in reality, the upper tuyere 12 may be provided at a position above the main tuyere 3 and at a position where the temperature of coke is 900°C or less. However, if the position is too close to the gas discharge port 4, the amount of heat generated by the reaction of equation (1) cannot be sufficiently imparted to the charge, and thermal efficiency may deteriorate. Therefore, the upper tuyere 12.

It is necessary to provide it in an appropriate range between the main tuyere 3 and the gas discharge port 4.

A cupola for melting pig iron, steel scrap, etc. has a (
Although there are examples in which air blowing tuyeres are provided to advance the reaction of formula 1), dust i is not reduced within the cupola. Therefore, it is not possible to directly apply the conditions in the cupola to the furnace of the present invention to determine the position of the upper tuyere I2. The appropriate position of the upper tuyere 12 varies depending on the type of pod, and it is difficult to find a certain regularity in its position.

To this end, the present inventors conducted various experiments on the appropriate position of the upper tuyere I2 through experiments using a furnace having the profile shown in FIG. As a result, if the distance from the main tuyere 3 into which dust is blown is taken as a reference and the distance from the tuyere 3 to the gas discharge port 4 is d, the position of the upper tuyere 12 is '0.3 d -0.
, 7, i was found to be sufficient. moreover,
It has become clear that the thermal efficiency of secondary combustion is better when the upper tuyeres 12 are arranged in multiple stages than when arranged in one stage in the height direction.

Non-water-cooled tuyeres can also be used, but water-cooled copper tuyeres are preferred for long-term use.

〔effect〕

Due to the above-described structure and operation, the processing furnace of the present invention can treat converter slurry and dust generated in the stainless steel manufacturing process with high energy efficiency and at a low coke ratio, and as a result, Ni in the by-products is ,Cr,F
Valuable metals such as e can be recovered at low cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the overall equipment of a by-product processing furnace according to the present invention, FIG. FIG. 3 is a diagram schematically showing the reaction in the processing furnace of the present invention and the temperature distribution of gas, coke, and ferrometal in the height direction inside the furnace. 1. Processing furnace body, 2. Furnace top manufacturing population. 3. Main tuyere, 4. Gas discharge port 8.15 ・
・Blower, 9.・Hot stove. 10...Oxygen gas, 11...Powder raw material hopper 1
2. Upper tuyere, 13. Lower tuyere 20. Exhaust fan, 22. Dust removal device.

Claims (3)

[Claims] (1) Converter slag generated during the stainless steel manufacturing process,
This is a vertical melting furnace for bulk processing of valuable metal-containing by-products such as sludge and dust. Among the by-products, lumpy substances are charged from the top of the furnace together with coke and other raw materials, and powdery substances are charged into the furnace top. In a vertical melting furnace in which high-temperature oxygen-enriched air is fed into the furnace from a tuyere in the lower part of the furnace, air or high-temperature oxygen-enriched air is fed into the furnace belly above the tuyere for feeding powdery material. A by-product of the stainless steel manufacturing process, characterized in that a tuyere for blowing oxygen-enriched air is provided, and a tuyere for blowing high-temperature oxygen-enriched air is provided in the furnace belly at a position below the tuyere for feeding powdery material. Processing furnace. (2) The processing furnace according to claim 1, wherein the tuyeres provided above the tuyere for feeding powdery material are provided in multiple stages in the vertical direction of the furnace. (3) Other raw materials charged from the top of the furnace include scrap and/or
The processing furnace according to claim 1 or 2, which is a ferroalloy.