JPS62162657A - Reformation of steel slag - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is directed to free lime, free lime (hereinafter referred to as F-CaO, F・M
This invention relates to a method of modifying steelmaking slag containing CaO-SiOz and causing expansion collapse or elution of heavy metal ions by adding a small amount of modifying material and using only sensible heat.

<Conventional technology> When steelmaking slag is cooled in its generated state, it may expand and collapse or elute heavy metal ions.In the case of only the former, some of it is used for fertilizers, cement raw materials, etc., but most of it is disposed of in landfills. This is a problem because it scatters as dust and worsens the working environment.

As a treatment method for such steelmaking slag, Japanese Patent Application Laid-Open No. 53-4
As shown in Japanese Patent Publication No. 3690, Japanese Patent Publication No. 59-19897, etc., a method in which a modifying material such as slate, which is a silicate rock, is added, dissolved and diffused, and then cooled, and a boric acid compound is added, 2CaO- The transition of 3iOz was stopped at β, r-
There is a method to prevent the disintegration by preventing the formation of 2CaO.SiO□, but it has not been possible to prevent the elution of heavy metal ions.

<Problems to be solved by the invention> In the conventional method, F-Cab, F-Mg0.7-2C
By adding silicate rocks etc. to prevent the formation of aO-SiOz, stable minerals 2CaO-A1203・SiO□,
2CaO-Mg0・2SiO□, 2CaO0Fe20
．． However, since the amount added is large, the slag method has a large amount of undissolved matter, there is a lot of loss, and often the property is not modified. Also, if you use the simultaneous charging method, the ratio will be better, but the slag removal speed will often be faster, and the timing will not match and you will have to charge a lance vibe-like object and use 0□, Nz or Air.
It is not practical because it requires bubbling or the application of supplementary energy such as electricity or gas.

Also, if boric acid compound is added to 8203 in an amount of 0.3z or more, 2
It is possible to prevent disintegration by stopping the transition of CaO/SiO□ to β-2CaO/SiO□, but F-CaO
, F-MgO, it has no effect and has expansion and collapse properties, and slag containing heavy metals such as Cr produces Cr'+
There was a problem that ions were eluted and modification could not be carried out.

<Means for Solving the Problems> In order to achieve the object of the present invention, the present invention includes: ■ Melting and diffusing only with sensible heat ■ Preventing the elution and decay of heavy metal ions that can be added in small amounts ■ Modifications We will mainly consider the slag method, which does not require investment in quality work input equipment, bubbling equipment, auxiliary energy equipment, etc.

Since it has a low melting point and contains gas and crystal water, it has a bubbling effect, and by foaming at about 950 to 1050°C, the slag enters the voids, and the molten slag enters the pores and forms ordinary silicate rocks and minerals. The melt-diffusion reaction also progresses in comparison.

Among silicate rocks and minerals, especially obsidian and nacre.

The above object was achieved by using quartz trachyte, pinestone, expansive shale, or a combination of these and a boric acid compound.

The gist is that B20 in slag is added to molten steelmaking slag:
Boric acid or a boric acid compound so that the I content is 0.1 to 0.3% by weight, and 3 to 5% by weight of silicate rocks/minerals and their forms, karami, coal ash based on the amount of slag. This is a method for modifying steelmaking slag, which is characterized by adding a modifying material consisting of one or more of glass scraps, foundry waste sand, and causing a melting reaction to modify the steelmaking slag.

EXPERIMENTAL RESULTS AND EXAMPLES> The present invention will be described in detail below with reference to experimental results and examples.

Table 1 shows the chemical analysis values of each raw material used in the following experiments and examples, and Table 2 shows the results of measuring the melting temperature after making a Seegel pile using the JIS method.

In addition, each raw material was ground to 5 mm or less, slag was magnetically separated and only non-magnetized material was used, and sodium acetate and boric anhydride were reagent grade.

In the experiment, slag was placed in an electro-fused magnesia crucible, remelted (softened) at 1400°C in a siliconite electric furnace, and
After adding the additives in the proportions shown in the table and holding for 5 minutes (completely melted), take them out of the furnace for chemical analysis,
Table 5 shows the results of the treatment.

<Example 1> Raw materials are melted in a 40T electric furnace, the molten metal and slag are placed in a ladle, and about 4000 kg of slag alone is discharged before being sent to the next smelting furnace.

When a mixture of 120 kg of pearl rock crushed to 5 mm or less and 8 kg of boric anhydride was placed in the bottom of a ladle as a substitute for slag, and the slag was received, the reaction and diffusion took place very well. .

After air cooling for about 4 to 5 hours, it fell over and was crushed.

Samples were taken after magnetic separation treatment.

<Example 2> Raw materials are melted in a 40T electric furnace, the molten metal and slag are received in a ladle, and about 4000 kg of slag alone is discharged before being sent to the next smelting furnace.

If you put 460 kg (about 14%) of a 50:50% mixture of sandstone and slate (50:50%) into the bottom of a ladle as a substitute for slag, and receive the slag, the appearance will be relatively good. It seemed to react well, but when it was turned over after being air-cooled for about 4 to 5 hours, a large amount of unreacted substances remained (about 60%), causing dusting and disintegration as it cooled.

<Example 3> Raw materials are melted in a 40T electric furnace, the molten metal and slag are placed in a ladle, and approximately 4000 kg of slag alone is discharged before being sent to the next smelting furnace.

At the bottom of the ladle, as a substitute for slag, 120 kg of a mixture of obsidian crushed into pieces of 5 mm or less: 20:80 wt.
．． 15% by weight) of the mixture, loOKg was placed in a ladle as a substitute for slag, 41.5 kg was placed on top of the slag in the ladle, and the slag reacted very well. . Approximately 4~
After being air-cooled for 5 hours, it fell over, but almost no unreacted substances were detected. Samples were taken after crushing and magnetic separation processing.

In addition, Table 4 shows the roadbed material tests for the light-spreading slag and the slag after the modification test.
For a particle size of 5 mm, 20 Kg/cm" was maintained at 200°C for 3 hours, and particles with a particle size of 10 mm or less were considered to be disintegrated.
Shown in the table.

In both Examples and 1.2.3, the original slag and the slag after the modification test were subjected to elution tests according to the method notified by the Environment Agency, and the results showed that Cu, Cd, Pd, Zn, Mn, Fe, As, T,
No Hg was detected. In Example 2, the reaction was insufficient due to the use of ordinary silicate rocks, and the Cr'' ions were eluted, but there was no problem in Examples 1 and 3, which were modified. .

In addition, the effect will be even better if 0.3% or more of 8203 is added by adding 3 to 5% by weight of silicate rocks, etc. and a boric acid compound, but the reforming cost will increase due to the increased amount of input. However, the simple modification method using the slag method results in a large amount of undissolved matter, resulting in large losses and not being able to be modified in an efficient manner.As such, auxiliary equipment such as bubbling is required, so the amount of boric acid compound added was limited.

Addition of silicate rocks and minerals such as black soil, especially obsidian, nacre, etc., which have low melting points and contain gas, etc., lowers the melting temperature, and stabilizes the stable mineral 3CaO-AIgo3.
．． CaO-Mg04i0z+ 2CaO・AIgo, J
It can be seen that -5iOz to 2CaO, MgO, 2SiOz, etc. are generated and disintegration is prevented, and the elution of Cr" ions, which are heavy metal ions, is also prevented and modification is achieved.

Furthermore, even if only a boric acid compound is added, if it contains 2CaO-SiO□, the transition will stop at β-2CaO・SiO□ and collapse will be prevented, but if it contains F and MgO (bericrene), it will remain as it is. remains and collapse is not prevented.

However, these problems can be solved and modified by adding a small amount of boric acid compound and a small amount of silicate rocks/minerals, etc., and the effect is particularly great when used in combination with volcanic rocks such as obsidian and nacre.

<Effects of the Invention> As described above, according to the method of the present invention, obsidian, nacre, and pine rock that contain a small amount of boric acid compound and gas or crystal water, foam and melt at low temperatures, and have a diffusion effect. 1 By using it in combination with quartz trachyte, etc. or other silicate rocks/minerals, etc., it is approximately 173% lower than conventional modification materials of silicate rocks/minerals, etc. alone, or mixtures thereof. Therefore, even with steelmaking slag, which has relatively little sensible heat, the investment in reforming equipment is small, and the slag and molten diffusion reaction can be effectively carried out by using the slag method or a combination of the slag method and the addition of slag during removal. .

Furthermore, when a thin surface-hardened slag is formed during agglomeration work, adding a modifying material on top of it will preheat it, and the temperature of the molten metal during agglomeration will not drop and there will be no return S-P. It is convenient to shake and discharge ~3 times (reforms).

In addition, when only boric acid compound is added, 2CaO1SiOz
β-2CaO9SiO□ can stop the transition and prevent collapse, but if F, CaO, and F-MgO are contained, most of them remain as they are, and there is no effect of preventing collapse, and the elution of heavy metal ions such as Cr ions cannot be prevented. However, as mentioned above, when a boric acid compound is used in combination with silicate rocks, minerals, etc., even a small amount of addition can prevent disintegration and the elution of heavy metal ions, and the effect is great.

Claims (1)

[Claims] 1. Boric acid or a boric acid compound is added to molten steelmaking slag so that the content of B_2O_3 in the slag is 0.1 to 0.3% by weight, and 3 to 5% by weight based on the amount of slag. A modifying material consisting of one or more of silicate rocks and minerals and their weathered products, karami, coal ash, glass waste, and foundry waste sand is added to cause a melting reaction to modify steelmaking slag. A method for modifying steelmaking slag. 2. The method according to claim 1, characterized in that one or more of obsidian, pearlite, pine rock, quartz trachyte, and expansive shale is added as the silicate rock/mineral. Method for reforming steelmaking slag. 3. When the steelmaking slag in the ladle forms a thin hardened film on the surface of the steelmaking slag in the ladle during the agglomeration process, add boric acid or a boric acid compound and the modifying material by scattering it over the hardened film. A method for modifying steelmaking slag according to claim 1. 4. The method for modifying steelmaking slag according to claim 1, characterized in that boric acid or a boric acid compound and the modifying material are added in the form of slag in a slag pot. 5. The method for modifying steelmaking slag according to claim 1, characterized in that boric acid or a boric acid compound and a modifying material are added into a ladle after the ingot-forming operation has been completed.