JPH0834643A - Steelmaking slag pulverization inhibitor and method for producing the same - Google Patents

Abstract

PURPOSE:To improve the solubility of the agent in molten slag and the production cost by using a flaky borosilicate alkali glass as the effective component. CONSTITUTION:The borate compd. as the boron material such as boric acid, sodium borate, colemanite and ulexite, the limestone, slaked lime, quick lime, etc., as the calcium material, the magnesia, dolomite, etc., as the magnesium material, quartzite, quartz sand, etc., as the silicon material and the soda ash as the sodium material are mixed, the formulation is introduced into a melting furnace, heated and melted, and the melt is dripped on a flaker, solidified, crushed and controlled in grain size to obtain the flaky agent for preventing powdering having 1.5 aspect ratio and 5-25mm average major axes and contg. 20-50wt.% B2O3 10-40% CaO (and/or MgO), 10-35% SiO2 and 5-20% Na2O. The agent approximates the molten slag in viscosity and sp.gr., and the sandy powder of glass can be jointly used, as required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slag dusting preventive agent for preventing the phenomenon of self-disintegration and pulverization in the cooling process of steelmaking slag, and a method for producing the same.

[0002]

2. Description of the Related Art Steelmaking slag, especially stainless steelmaking slag
Regarding lag, basicity (CaO / SiO ₂Weight ratio) About 1.
Slag of 5 or more is 2CaO · S during the cooling process.
iO₂Phase transition from α-type to α′-type, γ-type or
Has the property of transferring to β type, and in many cases
In order to accompany the volume expansion of about 14% when transferring to γ type
It is known that the slag itself self-disintegrates and powders.

This pulverization phenomenon deteriorates the working environment, and further, a large amount of dehydrated cake as a residue after recovery when recovering metal in slag is a major cause of increasing the burden on steelmakers for slag treatment. It has become.

[0004] Preventing the slag from pulverizing and solidifying it has been a long-standing problem for steel manufacturers because the discharged slag can be effectively used as a secondary aggregate for civil engineering such as roads.

The following methods may be mentioned as methods for suppressing slag pulverization.

(1) A method in which granulated glass is formed when slag is discharged.

[0007] ₍₂₎ SiO 2 in 2CaO · SiO ₂ slag
A method in which a source is added and the slag is composed mainly of CaO.SiO _{2 and} has a basicity of 1.5 or less (substantially varies slightly depending on the slag composition).

(3) A method of suppressing the α′-type to γ-type phase transition having a large density change and promoting the α′-type to β-type phase transition having a small density change.

Of these, the method (1) may cause a steam explosion during water granulation due to the molten metal that accompanies the slag slag, and the granulated material is soft enough for use as an aggregate for civil engineering. Although it cannot have strength, it has been put to practical use in some areas.

In the method (2), there is a commercially available SiO ₂ type modifier at present, but for the molten slag,
Since a large amount of SiO ₂ of about 20% is required, it is necessary to install charging equipment and stirring equipment, and further increase the viscosity of the slag due to the temperature decrease of the molten slag accompanying addition, and in terms of workability and cost. Inappropriate.

The method (3), that is, the phase transition from α'type to β type has been studied for a long time and various methods have been proposed. Among these methods, B ^{+3 having an} ion radius smaller than that of Si ⁺⁴ ion in slag
The method of substituting Si ⁺⁴ by means of the method has been proposed as an effective method (Japanese Patent Laid-Open No. 53-43690, Kawatetsu Technical Report Vo.
l. 18, No. 1 (1986) 20-24).

However, since the conventional boron-based slag dusting preventive agent is in the form of fine powder and is itself a water-containing substance, it is combined with a dehydration vaporization reaction when it comes into contact with molten slag to prevent slag dusting. The agent is blown up, the working environment is significantly deteriorated, and sometimes dangerous, so that its operation is very difficult. Furthermore, since the melting temperature of the slag dusting inhibitor itself is low, but its viscosity is high, there is a problem that the slag dusting prevention effect is difficult to be manifested because the diffusion and mixing into the slag are insufficient only by the slag sensible heat.

Further, since the conventional boron-based slag dusting agent has a chemical composition greatly different from that of slag, a difference in viscosity and density is likely to occur with respect to the molten slag, so-called slag and slag dusting inhibitor. It has a disadvantage that it has a poor affinity with and has a small diffusive mixing ability.

In order to solve the conventional drawbacks of the boron-based slag dusting preventive agent, the following matters should be taken into consideration.

The work environment is not deteriorated due to dust generation, harmful gas generation, etc. accompanying addition to the molten slag, and it is safe in operation.

The addition amount to the slag should be small so that the slag temperature is not significantly lowered and the viscosity is not increased.

The viscosity and density difference from the molten slag are small,
It must have a so-called high affinity chemical composition.

The present applicant has proposed an anti-dusting agent containing a sandy powder of alkali borosilicate glass as an active ingredient, as an anti-dusting agent for steelmaking slag which can solve the above-mentioned drawbacks (Japanese Patent Publication No. 50456 publication). Unlike the conventional fine powder of a crystalline borate compound, this powdering inhibitor is an anhydrous sandy powder, so it has excellent workability and can perform powdering prevention with good safety, and is widely used. It is put to practical use.

[0019]

The object of the present invention is to pulverize the steelmaking slag, which is based on the above-mentioned slag dusting preventive agent of the present applicant, has good meltability with respect to molten slag, and can be produced at a lower cost. An object is to provide an inhibitor and a method for producing the same.

[0020]

Means and Actions for Solving the Problems The present inventor, while taking advantage of the advantages of alkali borosilicate glass, further researched for further improvement, and found that the glass flakes had a very high affinity with molten slag, The present invention has been completed by finding that it is excellent as a dusting inhibitor and can be industrially advantageously produced.

That is, the present invention relates to a powdering inhibitor for steelmaking slag containing flake-shaped alkali borosilicate glass as an active ingredient.

In the present invention, the glass composition is B
₂ O ₃ : 20 to 50% by weight, MO: 10 to 40% by weight (however, M represents Ca and Mg), SiO ₂ : 10 to 35.
% By weight and Na ₂ O: 5 to 20% by weight, a raw material containing one or more of boron, calcium (and / or magnesium), silicon and sodium is prepared, and then the obtained composition is heated. After melting, the melt is cast down into a flaker, then solidified and particle size adjusted,
The present invention relates to a method for producing an anti-dusting agent for steelmaking slag containing flake-shaped alkali borosilicate glass as an active ingredient.

The present invention will be described below.

The boron-based steelmaking slag dusting preventive agent (hereinafter referred to as "slag dusting inhibitor") according to the present invention is different from the conventional fine powder of crystalline borate compound in the alkali borosilicate glass. It is characterized in that it is a flake powder.

This glass is superior in affinity to the melt of steelmaking slag (hereinafter simply referred to as "slag") to the crystalline borate compound, but in order to further improve the affinity, It is desirable to have a chemical composition that is similar in viscosity, specific gravity, etc. to the molten slag.

Therefore, the glass often has a chemical composition of B ₂ O _{3 of} 20 to 50% by weight, CaO (and / or MgO) of 10 to 40% by weight, and SiO _{2 of} 10 to 35%.
Wt% and Na ₂ O: in the range of 5 to 20 wt%.

If it is out of this range, the viscosity becomes high,
Alternatively, vitrification tends to be difficult, and the performance of the powdering inhibitor tends to deteriorate. Needless to say, the presence of impurities that are inevitably mixed is naturally acceptable.

Next, the pulverization preventing agent according to the present invention is in the form of flakes.

The reason for this is that the contact dissolution with the molten slag is rapid and can be diffused uniformly in the slag melt, and no dust is generated during the contact dissolution.

Here, the "flakes" in the present invention
Has an aspect ratio of 1: 5 or more and an average major axis diameter of 5 to 5 from the viewpoints of meltability to slag, safety, and manufacturing.
Those in the range of 25 mm are preferable.

The anti-dusting agent according to the present invention contains the glass flakes as described above as an active ingredient, but a sandy powder of the glass may be used together if necessary.

Next, the pulverization preventing agent has a glass composition of B ₂ O ₃ : 20 to 50% by weight, CaO (and / or Mg).
O): 10 to 40% by weight, SiO ₂ : 10 to 35% by weight
And Na ₂ O: boron so as to be 5 to 20% by weight,
A raw material containing one or more of calcium (and / or magnesium), silicon and sodium is blended,
The resulting formulation can then be heated to a solution before being made to flow by flowing the melt through a flaker, followed by solidification and particle size adjustment.

As the boron raw material, for example, as described above,
Boric acid, such as chemicals or colemanite boric acid soda _{(colemanite) (Ca 2 B 6} O 11 · 5H
₂ O), urexite (NaCaB ₅
O ₉ / 8H ₂ O), tincal (Na ₂ B ₄
O ₇ · 10H ₂ O), carnite (kernite) (N
such as _{a 2 B 4 O 7 · 4H} 2 O) such as borate minerals and the like.

As the calcium raw material, limestone, slaked lime,
Quick lime, calcium silicate, etc. may be mentioned. Magnesia, dolomite, calcite, etc. may be mentioned as the magnesium raw material which may be inevitably mixed from a calcium source. The silicon raw material is silica stone, silica sand, silica, aluminum silicate, calcium silicate, etc., and the sodium raw material is soda ash, sodium silicate glass and the like.

These raw materials are appropriately selected and compounded so that the glass composition falls within the above range, and the mixture is put into a desired melting furnace and heated and melted. As a melting furnace, oil furnace, gas furnace,
Although there are coke ovens, electric ovens, etc., an oil or coke oven is preferable in terms of cost.

Next, the melt is filled with, for example, 10 to 30 mmφ.
From the exit of the flaker (double roll internally cooled with water)
Then, the candy-shaped glass in the form of a thin plate is flowed down on a belt conveyor to be cooled and solidified.

Next, the solidified glass is dropped from the belt conveyor into a container and crushed to obtain a flake-shaped glass having the above-mentioned size, whereby the present invention can be obtained.

In the manufacturing process of the present invention, water is not used for granulation or cooling, so that a drying process is not required, which is very advantageous in terms of cost.

The slag to be used in the present invention is a steelmaking slag, but it is one which causes a phenomenon such that the slag collapses or powders upon cooling or with the passage of time, and is generally CaO / SiO. ₂ (weight ratio) is 1.5 or more.

Further, the mode of adding the dusting inhibitor according to the present invention is not particularly limited as long as a method of mixing and diffusing into the molten slag immediately after addition can be adopted. For example, a method of spraying on the surface of the molten slag, a method of charging the bag containing a desired amount, a method of transferring with pressurized air so as to be sprayed onto the molten slag, or an inert gas (N ₂ , after addition to the molten slag, There is a method of stirring with Ar gas).

The amount of the dusting inhibitor according to the present invention added to slag is at least 0.1% by weight as B ₂ O ₃ , and preferably in the range of 0.2 to 0.6% by weight. If it is less than about 0.1% by weight, it is insufficient to prevent slag powdering, and the upper limit is naturally limited mainly for economic reasons.

The present invention will be specifically described below with reference to examples.

[0043]

Example 1 25 m ^{3 of} a raw material mixture having a mixing ratio (parts by weight) shown in Table 1 was used.
It was melted under a temperature of 1200 to 1250 ° C. using a petroleum furnace of a capacity.

[0044]

[Table 1]

The obtained melt was made to flow from an outlet of 20 mmφ into a breaker of an internal water-cooled twin roll to form a plate, which was flowed out on a movable belt conveyor and solidified. Then, a vitrified product having the composition and shape shown in Table 2 was obtained.

[0046]

[Table 2]

Each of these vitrified products was sealed in a paper bag of 10 kg and used as a test sample for an anti-dusting agent.

Further, the slag basicity (Ca) at the first tapping produced from an electric furnace for stainless steel (50 t capacity)
When removing the O / SiO ₂ = 1.92) from the ladle to the slag pot, a predetermined amount of the test sample was simultaneously put in a paper bag of about 10 kg, and the slag was left to cool and solidify until it reached room temperature. I observed the situation.

The conditions at the time of the test are as follows.

[0050]

[Table 3]

When adding the sample, no dusting or gas generation was observed in any of the experiments, the adding operation was safe, and good diffusion mixing was obtained when pouring the slag into the slag pot.

Further, when the condition was observed after the slag used in the test was allowed to cool to room temperature, no disintegration powdering phenomenon was observed at all.

The slag composition (% by weight) after the test was as follows.

[0054]

[Table 4]

The slag itself self-disintegrates and powders when cooled.

Further, the slag disintegration rate was measured by autoclaving the slags (after reforming) and the slags without addition (before reforming) of samples A, B, and C under the following treatment conditions.

Treatment conditions: Particle size 10 to 2 after crushing sample slag
The particle size is adjusted to 5 mm, and this is 200 ° C, 20 kg / cm
^It was kept in the autoclave for a few hours and then dried, and then sieved to obtain a disintegrated material having a particle size of less than 10 mm.

The proportion (%) of the disintegrated product after the autoclave treatment is shown.

[0059]

[Table 5]

Comparative Example 1 In Example 1, borax (Na ₂ B ₄ O ₇ · 10H ₂ O) (B ₂ O ₃ : 37.0) was added to the molten slag as an anti-dusting agent.
0 wt%, Na ₂ O: 16.5 wt%) (0.2-0.
When 12 kg / t slag and vinyl bag were charged together with 55 mm of 4 mm), vigorous scattering and blowing up occurred and undissolved lumps were generated, so the injection had to be stopped.

[0061]

【The invention's effect】

1) Since the product of the present invention is a vitrification inhibitor for slag powder, it has a small heat absorption amount due to melting such as thermal decomposition vaporization heat of carbon dioxide gas and water vapor, and transition heat, and is particularly flaky. The melting rate is much faster than the conventional one.

2) Since the chemical composition is designed to have a high affinity with a small difference in viscosity, density, etc. with respect to the molten slag,
Compared with the conventional product, the product of the present invention has an extremely large effect of diffusion mixing.

3) Since it is a vitrified anhydrous slag dusting inhibitor, it does not cause a degassing reaction and has a flake-like size. Therefore, when added to the molten slag, it is blown up and works by dust. It does not make the environment worse.

4) Since water is not used in the production process of the present invention, a drying process is not required and the production can be carried out easily and at low cost.

Claims (5)

[Claims] 1. An anti-dusting agent for steelmaking slag, which comprises a flake-shaped alkali borosilicate glass as an active ingredient. 2. Alkali borosilicate glass contains boron as B
The powdering inhibitor for steelmaking slag according to claim 1, which contains 20 to 50% by weight as ₂ O ₃ . 3. The alkali borosilicate glass has a chemical composition of B ₂ O ₃ : 20 to 50% by weight, MO: 10 to 40% by weight (wherein M represents Ca and Mg), and SiO ₂ : 10.
The pulverization inhibitor for steelmaking slag according to claim 1 or 2, which comprises ˜35 wt% and Na ₂ O: 5 to 20 wt%. 4. The pulverization inhibitor for steelmaking slag according to claim 1, wherein the alkali borosilicate glass has a flake shape with an aspect ratio of 1: 5 or more and an average major axis diameter of 5 to 20 mm. . 5. B ₂ O ₃ as a glass composition: 20 to 50% by weight, MO: 10 to 40% by weight (where M is Ca, Mg)
Represents ), SiO ₂ : 10-35 wt% and Na
₂ O: a raw material containing one or more of boron, calcium (and / or magnesium), silicon and sodium in an amount of 5 to 20% by weight is prepared, and then the obtained composition is melted by heating, A method for producing an anti-dusting agent for steelmaking slag containing flake-shaped alkali borosilicate glass as an active ingredient by allowing the melt to flow down to a flaker, followed by solidification and particle size adjustment.