JP2002249811A - Method for treating waste brick containing magnesium and chromium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating waste bricks containing magnesium and chromium capable of recovering chromium in a chemically stable manner by treating a large volume of a waste bricks containing granular magnesium and chromium of grain size of several mm. SOLUTION: When raw material containing metal is melted and reduced to recover molten metal by blowing the granular raw material containing metal and slag-forming agent from at least an upper stage tuyere into a vertical smelting and reducing furnace forming a filling layer inside by charging carbon solid reducing agent from a furnace top, and having at least two-staged upper and lower tuyeres from which high-temperature oxygen-enriched air is blown, waste bricks containing granular magnesium and chromium are blown together with the raw material containing metal, and the slag-forming agent of predetermined composition is separately charged from the furnace top.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for treating brick waste containing magnesium and chromium.
The present invention relates to a technique for reducing magnesium and chromium-containing bricks in the form of powder to completely recover chromium as molten metal, thereby rendering magnesium and chromium-containing brick waste harmless.

[0002]

2. Description of the Related Art Brick containing magnesium oxide and chromium oxide, such as magcro-brick and chrome-mag-len, has excellent fire resistance and high-temperature corrosion resistance. Has been used effectively. However, waste materials after use have undergone a phase transformation, and cannot be easily decomposed into magnesia and chromia or reprocessed into bricks, and are difficult to treat.
If waste materials such as magcro and bricks are simply left as they are, hexavalent chromium may be eluted into the soil.

[0003] JP-A-6-240484, JP-A-6-240484
Japanese Patent Application Laid-Open Nos. 2626964 and 10-174955 disclose techniques for performing wet treatment, heat treatment, and the like on waste containing chromium. That is, hexavalent chromium contained is reduced to low-valent chromium, which is then reclaimed or reused as a cement raw material.

However, it is not yet clear whether low-valent chromium is truly stable over a long period of time, even if it is treated with these techniques and then reclaimed or reused as cement. In addition, it is recently difficult to secure landfill sites for landfill disposal, and chromium is also an unnecessary component in cement raw materials, which causes a problem of lowering product value. In addition, if a separate facility is constructed for the reduction treatment, the treatment cost increases, and there is an economical problem in treating a large amount of waste magnesium and chromium-containing bricks generated by the above-described technology.

On the other hand, Japanese Patent Application Laid-Open No. 9-157765 discloses that
We propose a technology to use magcro and brick waste as part of the slag-making agent when refining in a converter. The reason is that magnesia in the magcro brick and brick makes a slag-making action, and is expected to have an effect of increasing the Cr concentration in the formed slag and promoting the smelting reduction of the Cr ore charged into the converter.

However, in the technology used as a slag-making agent for steelmaking, since the steelmaking material is put into the furnace together with other steelmaking raw materials from the upper part of the converter, a fine powder portion rises above the converter. There is a problem that it is discharged out of the system as converter dust accompanying the furnace gas. In addition, the waste material of magcro and bricks generated during the dismantling of cement kilns is pulverized in the brick dismantling process, and most of them are collected in the form of powder having a particle size of several mm or less. However, when they are put into a converter, a considerable amount is discharged as converter dust. For this reason, it is conceivable to agglomerate the powdery part and then put it into the converter. However, equipment costs and processing costs for the agglomeration are enormous, and it is difficult to employ agglomeration.

[0007]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention is capable of treating a large amount of powdered and granular magnesium and chromium-containing brick waste having a particle size of several mm or less to chemically stably recover chromium. An object of the present invention is to provide a method for treating brick waste containing magnesium and chromium.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above-mentioned object, and have noticed that a technique for reducing Cr ore and chromium-containing dust to obtain a chromium-containing metal already exists. . The technology, as shown in Figure 1,
A vertical smelting reduction furnace (commonly referred to as a carbon material packed bed type) having a packed layer 1 of a carbon-based solid reducing agent formed thereon and having at least two upper and lower tuyeres 3 and 4 for blowing high-temperature oxygen-enriched air 2. (A smelting reduction furnace) 5. According to this technique, irreducible Cr ore or chromium-containing dust is blown into the furnace from at least the upper tuyere 3 together with ironmaking dust and the like. It can be melted and reduced in a high-temperature atmosphere generated by the combustion of a system solid reducing agent to obtain a molten metal based on chromium-iron.

[0009] In view of the above, the experimental operation of treating magcro-bricks and black-mag-brick wastes in the same manner as in the above-mentioned Cr ore injection technique was unsuccessful. It was embodied in the invention.

That is, the present invention has a tuyere provided in at least two upper and lower stages into which a carbon-based solid reducing agent is charged from the top of the furnace to form a packed layer therein and into which high-temperature oxygen-enriched air is blown. In a vertical smelting reduction furnace, a powdered metal-containing raw material and a slag-making agent are blown from at least the upper tuyere, and the metal-containing raw material is melt-reduced to recover the molten metal. This is a method for treating waste magnesium and chromium-containing bricks, which comprises blowing granular magnesium and chromium-containing bricks and separately charging a slag-making agent having a constant composition from the furnace top.

In this case, the slag-making agent separately charged from the furnace top may have a basicity (CaO / SiO ₂ ) of 1.0 or less, or may have a maximum particle size of the powdered magnesium and chromium-containing brick waste material. The diameter is preferably 5 mm or less.

[0012] According to the present invention, even if the hard-melting magnesium and chromium-containing brick waste material is blown from the tuyere, there is already a sufficient amount of melt before the tuyere to absorb it. Therefore, the slag of the granular material does not occur, and the smelting reduction is facilitated. As a result, the operation is stabilized, Cr is completely recovered as molten metal, and magnesia is absorbed by the slag. That is, detoxification treatment of magnesium and chromium-containing brick waste can be achieved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the circumstances that led to the invention.

First, the experimental operation which failed will be described. The vertical smelting reduction furnace having a molten metal production of 200 t / day was used for the experiment operation. For the carbon-based solid reducing agent charged from the furnace top and forming a packed bed inside, only the lump of so-called "metallurgical coke" used in the blast furnace is used. As shown
Iron-making dust which is a metal-containing raw material, magcro / brick waste material to be treated in the present invention, silica sand and limestone as slag-making agents were used. The main operating condition is a blowing volume of 230 m ³
(Standard condition) / min, oxygen enrichment amount 68 m ³ (Standard condition) / min, blast temperature 850 ° C. The magcro and brick waste materials have a particle size of less than 7 mm, and are produced from steel converters (steel making) shown in Table 1
Mix into dust. Steelmaking dust contains metal oxides such as iron oxide and chromium oxide.

[0015]

[Table 1]

Table 2 shows other operation conditions and operation results.
Shown as Experiment 1. The above-mentioned slag-making agent was also mixed with steelmaking dust and magcro / brick waste material and blown in, but the chromium concentration in the molten metal (hereinafter referred to as metal) increased only to 12.0% by mass. The chromium concentration in the metal was estimated to be 13.7% by mass when estimated from the composition and mixing ratio of the blowing raw material, but the chromium yield was about 88%.
%Met.

[0017]

[Table 2]

In this method, the slag is not slag and the
Brick remains, and the treatment method is not perfect. In addition, the amount of dust discharged from the furnace top increased significantly, and the MgO and Cr concentrations in the dust increased.
It was also presumed that the injected magcro and brick waste powder was not completely melted and blown through.

Therefore, the inventor decided to pursue the cause of the failure of this attempt to inject magcro / brick waste material instead of Cr ore or chromium-containing dust.

In the conventional operation of injecting Cr ore or the like, metal and slag generated in the furnace are dropped through a carbon material packed bed in the furnace, and the metal and slag are discharged from a taphole provided in the furnace floor. I have. At that time, in order for the slag to drop in the carbon material packed bed, it is necessary to lower the viscosity of the slag. For this purpose, oxidation of SiO ₂ and Al ₂ O ₃ contained in carbon-based solid reducing agents such as coke and coal charged from the furnace top, and Cr ore blown from tuyeres and SiO ₂ contained in chromium-containing dusts are performed. Ca that is blown from the tuyere
A slag composition such as O or MgO is added to adjust the composition of the slag to lower the viscosity. That is, the basicity (CaO) of the slag formed by the solid carbon-based reducing agent charged from the furnace top, the various raw materials blown from the tuyere, and the slag forming agent as a whole.
/ A expressed also as SiO ₂ or B2) is set to about 0.7 to 1.3, so that to facilitate metal, the discharge of slag.

However, in the experimental operation of blowing the above-mentioned magcro bricks, a phenomenon was observed in which the discharge of slag outside the furnace deteriorated. This is presumably because slag adjustment in the furnace alone is not sufficient for dropping slag in the furnace.
Then, the inventor considered the cause of the deterioration of the slag dripping and made the following conclusions.

Magcro bricks are more difficult to melt than chromium ore, so that slag is not sufficiently formed even in a high-temperature atmosphere in front of the blown upper tuyere.

For this reason, a part of the blown magcro bricks is conveyed to the furnace gas and discharged as dust from the furnace top, or shifts to slag without slag.

As a result, the composition of the slag generated in the furnace deviates from the target slag composition, and the discharge of the slag deteriorates.

Conventionally, only the Al ₂ O ₃ and SiO ₂ derived from coke and the like fall down to the upper tuyere into which the slag-making agent is blown. Until it comes into contact with a slag-making agent such as CaO blown from the upper stage, it is considered that the melt is extremely small in front of the upper tuyere. In this case, the magcro bricks blown in front of the upper tuyere are absorbed by the melt at least inside the raceway (the space area in front of the tuyere), and are insufficient to start slagging and melting. The inventor of the present invention completed the present invention with the idea of not only blowing the slag forming agent from the tuyere but also charging the slag forming agent from the furnace top in order to solve the problem of the slag formation delay. When the slag forming agent is charged from the furnace top, the slag forming agent that has fallen around the raceway in front of the tuyere has been heated sufficiently, so the heat generated by the combustion of the carbon-based solid reducing agent has caused the heat around the raceway. In particular, it is almost molten at the upper part of the raceway, where magcro bricks, metal-containing raw materials (such as iron-making dust), and slag-making agents are collected from the tuyere and melted. Can be promoted. As a result, it is possible to suppress the above-mentioned blow-by phenomenon and the transfer of the slag to the unslagged state.

Further, the inventor has conducted intensive studies on the composition of the slag-making agent charged from the furnace top, and found that it is preferable to adjust the basicity to 1.0 or less. . When the basicity is 1.0 or less, the basicity of the slag forming agent that starts melting around the raceway becomes low,
This is because even if high-basic substances such as magcro and brick waste materials are blown from the tuyeres, the slag is sufficiently formed there.

In addition to the above, in the present invention, it is more preferable that the particle size of the magcro / brick waste material blown from the tuyere is 5 mm or less at the maximum. This makes it possible to substantially eliminate unslagged magcro bricks in the slag, thereby further increasing the yield of chromium.
As a result, the chromium concentration in the slag discharged from the furnace can be reduced to 1% by mass or less, and wide use of the discharged slag can be expected.

If the amount of the slag-forming agent charged from the furnace top is 10% or more of the total amount of the slag-forming agent supplied into the furnace, there is no hindrance to the generation of the melt before the tuyere. It is possible to prevent the blown magcro and brick waste material from scattering into dust.

[0029]

EXAMPLE The same molten metal production as in Experiment 1 described above was 2
Using a 00t / day scale vertical smelting reduction furnace, the method for treating magcro and brick waste according to the present invention was performed, and the results were compared with and evaluated for the usual treatment of ironmaking dust. The operating conditions and the operating results are collectively shown in Table 2 described above.

The components of limestone and silica stone charged from the furnace top are almost the same as those of blowing limestone and silica stone shown in Table 1, but a lump of 5 to 15 mm was used. First, the basicity (CaO / SiO ₂ ) of the slag generated from only the furnace top charge including coke is around 1.0, and the basicity of the slag generated from the raw material and the slag forming agent blown from the tuyere. The basicity of the furnace top charge and the tuyere blown product was adjusted so that was 1.0 (Example 1). As a result, as is apparent from Table 2, the amount of dust discharged from the furnace top was greatly reduced, and the Cr concentration of the dust was also reduced to the same level as in the normal operation, but the chromium concentration in the discharged slag was 1%. .2
% By mass. The chrome yield was about 91%, and achieved a yield of 90% or more.

The reason why the chromium in the slag is slightly high was considered as follows. The ash content in the limestone, silica stone and coke (Ash)
Was adjusted so that the combined basicity was around 1.0. However, since the carbon-based solid reducing agent (coke) was consumed in both the upper and lower tuyeres, the slag-making charged from the furnace top was used. The ash in the coke was not mixed with the slag-making agent while the agent descended to the upper tuyere, and slag having a very high basicity of 1.9 was produced only with the slag-making agent excluding coke. It is presumed that. Considering that magcro and brick waste material itself is a basic refractory and has extremely good erosion resistance to highly basic slag, if magcro and brick waste material is trapped in highly basic slag, it cannot be completely melted. It is presumed that the waste was discharged without leaving slag.

Therefore, the basicity is adjusted to 1.0 by mixing the slag-making agent charged from the furnace top without considering the ash content of coke.
As described below, the basicity of the slag discharged from the furnace bottom was adjusted by mixing various raw materials blown from the tuyere and a slag-making agent (Example 2). As a result, as shown in Table 2, the chromium yield could be increased to 95% or more. The chromium concentration in the discharged slag was 0.6% by mass, which was almost the same as in the normal operation. However, the [Cr] concentration in the metal was slightly lower than expected. Inspection of the fracture surface of the discharged slag revealed a small amount of unslagged magcro / brick particles. In addition, as a result of an investigation inside the furnace when the furnace was shut down, it was found that a large amount of 5 to 7 mm magcro brick particles remained in the furnace. Than this,
Since it is considered that the magcro / brick waste having a large particle size has not been completely melted and reduced in the furnace, the particle size distribution of the magcro / brick waste to be blown was changed, and a material having a particle size of less than 5 mm was used (Example 3). ). As a result, as shown in Table 2, the chromium concentration in the slag was almost as expected from the calculation, and the chromium yield increased to 98%.
Further, the chromium concentration in the slag was also reduced to 0.3% by mass, and no unslagged magcro / brick particles were present.

The main components of the recovered molten metal and the discharged slag are shown in Tables 3 and 4, respectively. The molten metal is a raw material for producing ferro-chromium of high quality, and the slag is of such an extent that it does not cause any problem. Chromium content.

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

As described above, according to the present invention, even if the powdery particles of magnesium and chromium-containing brick waste such as hard-to-melt magcro brick and black mag brick are blown from the tuyere, Since there is already a sufficient amount of the melt to absorb it, there is no loss due to blow-through of the granular material or loss due to unslagged slag, and smelting reduction is facilitated. As a result, the operation is stabilized, Cr is completely recovered as molten metal, and magnesia is absorbed by the slag. That is, detoxification treatment of magnesium and chromium-containing brick waste can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a vertical smelting reduction furnace filled with a carbon-based solid reducing agent.

[Explanation of symbols]

 Reference Signs List 1 packed bed 2 oxygen-enriched air 3 tuyere (upper) 4 tuyere (lower) 5 vertical smelting reduction furnace 6 reducing agent hopper 7 solid matter blowing device 8 discharge hole for molten metal and slag 9 hot stove

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Etsuro Udagawa 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term in the Technical Research Institute of Kawasaki Steel Co., Ltd. 4D004 AA16 AB03 BA02 BA05 CA29 CA37 CB02 CB34 CC02 CC11 CC15 DA03 DA20 4K012 CB02 CB06 CB07 DC01 DC07 DC08

Claims (3)

[Claims] 1. A vertical smelting reduction having tuyeres provided in at least two upper and lower stages into which a carbon-based solid reducing agent is charged from the top of the furnace to form a packed layer therein and into which high-temperature oxygen-enriched air is blown. Into the furnace, powder-granular metal-containing raw material and slag-making agent are blown from at least the upper tuyere, and the metal-containing raw material is melt-reduced to recover molten metal. A method for treating waste magnesium and chromium-containing bricks, comprising blowing chromium-containing brick waste and separately charging a slag-making agent having a constant composition from the furnace top. 2. The magnesium and chromium-containing brick waste material according to claim 1, wherein the slag-making agent separately charged from the furnace top has a basicity (CaO / SiO ₂ ) of 1.0 or less. Processing method. 3. The method for treating waste magnesium and chromium-containing bricks according to claim 1, wherein the maximum particle size of the powdered granular waste magnesium and chromium-containing bricks is 5 mm or less.