KR101149221B1 - A method for stabilizing slag - Google Patents

Abstract

The present invention relates to a method for stabilizing steelmaking slag subjected to reforming reaction by injecting silicon dioxide and oxygen into a ladle containing molten slag.

During the steelmaking process, silicon dioxide and oxygen are injected into the ladle containing slag separated from the converter to maintain the molten state in order to stabilize the free-CaO, a hydrated expansion material, into the crystal phase.

Accordingly, the present invention has a useful effect to induce crystallization of the glass lime, which is a hydrated expansion material in slag, to suppress the expandability when used as aggregate to improve product reliability.

Slag, glass lime, aggregate, crystallization

Description

Stabilization method of steelmaking slag {A METHOD FOR STABILIZING SLAG}

The present invention relates to a method for stabilizing steelmaking slag, in particular, by injecting silica sand and oxygen into a ladle containing slag in a molten state separated from a converter to stabilize expansion of steelmaking slag by stabilizing glass lime. It relates to a stabilization method.

In general, in order to utilize steel slag as road aggregates, asphalt concrete aggregates, or bricks or ready-mixed concrete aggregates, stability against volume expansion of the aggregates should be ensured.

In order to evaluate the stability of the volume expansion, the immersion expansion ratio test (KS F 2535 immersion expansion test method of steel slag for road) is conducted.

The steel slag referred to herein includes molten iron preliminary slag generated in converter steel, converter slag, oxide slag generated in electric furnace process, reduced slag, ferroalloy slag generated in ferroalloy manufacturing process, and molten slag generated in molten incinerator. Can be.

However, in the case of the existing steel slag, the oxidation slag of electricity contains a small amount of free lime (Free CaO), which is expanded by the hydration reaction, and thus, when recycled to road aggregates or ready-mixed concrete aggregates, cracks may occur due to expansion. There was.

Here, it is to provide an aging treatment method for reducing the expandability of the oxidized slag by electricity and to ensure the stability according to the expansion.

The present invention has been proposed in view of the above-mentioned problems, and an object thereof is to inject silica sand and oxygen into a ladle containing molten slag to stabilize glass lime to reduce expandability. It is to provide a stabilization method.

The present invention for achieving the above object is characterized by inducing crystallization of free lime (Free-CaO) by injecting silicon dioxide (SiO ₂ ) and oxygen (O ₂ ) in the ladle containing the slag in the molten state.

The silicon dioxide adopts silica sand having a carbon content of more than 0 and 5% by weight or less.

It is preferable to inject 0.15 to 0.2 ton of silicon dioxide and 0.025 to 0.04 Nm ³ / min of oxygen per ton of slag.

In addition, the silicon dioxide is preferably injected into the ladle through the lance using nitrogen gas.

According to the present invention, the modified reaction is performed by injecting silicon dioxide and oxygen into a ladle containing molten slag, and according to the present invention, the present invention induces crystallization of glass lime, which is a hydrated expansion material in slag, and expands when used as aggregate. It has a useful effect to improve the product reliability by suppressing.

Hereinafter, preferred embodiments of the present invention will be described in detail.

Stabilization method of the steelmaking slag according to the present invention, in order to stabilize the free-CaO (hydrate-expanding material) free lime (CaO) in the crystal phase in the ladle containing the slag separated from the converter during the steelmaking process to maintain the molten state Inject silicon dioxide and oxygen.

Silicon dioxide adopts silica sand such as steel sand and acid sand, but preferably, carbon content of more than 0 and 5% by weight or less is adopted.

This is because when it exceeds 5% by weight acts as a factor that decreases the strength of the slag aggregate is produced, there is a fear that the strength and durability of the asphalt concrete and concrete structures in which such slag aggregate is utilized.

Silicon dioxide is injected into the ladle through a lance using nitrogen gas, and oxygen is injected into the ladle through the lance.

At this time, the silicon dioxide material is preferably added after sufficiently drying.

When the amount of silicon dioxide injected is less than 0.15 ton of slag per ton of slag, when the silicon dioxide is injected, the stabilization reactivity through crystallization of quicklime (CaO, calcium oxide) in slag decreases, and the silicon dioxide exceeds 0.2 ton In the case of being injected into the molten slag, the molten slag is cooled due to the low temperature of the silicon dioxide into the molten slag, thereby reducing the crystallization reactivity between quicklime and silicon dioxide in the slag, and additionally adding oxygen to prevent cooling of the molten slag. A separate process is required and production costs are increased.
Therefore, in the present invention, it is preferable to inject 0.15 to 0.2 tons of silicon dioxide and to inject oxygen of 0.025 to 0.04 Nm ³ / min per ton of slag.

When the amount of silicon dioxide is too small, the reactivity decreases. On the contrary, if the amount of silicon dioxide is excessively added, the temperature of the molten slag is lowered and the melting point of the slag is increased.

Wherein the amount of oxygen is not the minimum value of the sign language preferred 0.025Nm ³ / min or more for the reaction of the intumescent substance and glass lime, 0.025Nm ³ / min, the reaction of free lime in the slag is less than in the slag can be made sufficient, If it exceeds 0.04Nm ³ / min, it is preferable to inject oxygen within the above range because it is a factor of the cost increase due to the increase in the amount of oxygen used.

That is, when the slag contained in the ladle is 25 to 40 tons, it is preferable to inject 4 to 8 tons of silicon dioxide and 0.5 to 1.0 Nm ³ / min of oxygen.

According to the present invention, silicon dioxide is directly injected into a ladle containing slag that is kept molten during the steelmaking process to stabilize the hydrated expansion material in the steelmaking slag which is a raw material, and the glass is not crystallized in the slag as oxygen is injected. Induced crystallization of lime.

In other words, by injecting dried steel sand or acid sand, such as silicon dioxide, into the molten slag and injecting oxygen, the temperature is increased as the silicon, manganese, and the like in the slag are oxidized, thereby increasing the temperature. Induce crystallization of other compounds and free lime.

At this time, the reacted slag is reformed into a CaO phase and a Ca ₃ SiO ₄ phase to suppress expansion.

Various reactions can be induced depending on the type of the slag.

The slag treated through the above treatment method is crushed and classified by the required particle size through the treatment method such as steelmaking slag dumping, crushing, screening process and reused as aggregate.

Conventional converter slag consists of the components of Table 1.

ingredient T-Fe SiO ₂ MnO ₂ Al ₂ O ₃ MgO CaO TiO ₂ Content (wt%) 16 18.2 3.2 1.3 9.7 44.7 0.9

The converter slag with this component contains free-CaO, which is 8-15 wt% of a hydrated expandable material.

As a result of injecting silicon dioxide and oxygen through the stabilization treatment method using the converter slag described above, the free lime content of the slag aggregate after treatment is shown in Table 2 below.

sample Sample 1 Sample 2 Sample 3 Sample 4 Glass Lime Content (wt%) 0.8 0.7 0.08 0.5

The test method for measuring the glass lime content is measured after heating the amount of Ca (OH) ₂ eluted from the slag aggregate for 60 minutes at a temperature of 550 ℃ using the method of heating loss of the Japan Cement Association Standard Test Method It is.

As the glass lime content is treated to 2wt% or less as described above, it is possible to reuse the aggregates due to lack of expandability due to moisture in the air.

In addition, 80 ° C immersion expansion ratio test results of the slag aggregate for evaluating the hydration expansion effect of the slag aggregate treated by the stabilization method of the present invention are shown in Table 3 below.

sample Sample 1 Sample 2 Sample 3 Sample 4 Immersion expansion ratio (%) 0.41 0.18 0.27 0.35

The test method applied to Table 3 was measured by the test method of KS standard standard KS F 2535 road steel slag 6.3, and it satisfies the product quality because it shows lower immersion expansion ratio than the standard value of immersion expansion ratio.

Therefore, the slag aggregate treated by the stabilization method of the present invention assures stability as fill aggregates, road foundations and auxiliary base aggregates through the stabilization of glass lime in the slag, as well as advanced aggregates such as asphalt aggregates. Also available.

Claims (4)

Injecting silica sand and oxygen (O ₂ ) having a carbon content of more than 0 and 5 wt% or less in a ladle containing molten slag induces crystallization of free-CaO, 0.15 to 0.2 ton of silicon dioxide and 0.025 to 0.04 Nm ³ / min of oxygen is injected per ton slag stabilization method of the steelmaking slag. delete delete delete