JPH01270542A - Modifying agent for preventing disintegrating and weathering of steel manufacturing slag and method for preventing the same - Google Patents

Abstract

PURPOSE:To rapidly stabilize and immobilize steel manufacturing slag and prevent disintegrating and weathering by blending a metallic Al-containing Al oxide with iron oxide, oxygencontaining boron compound and silicon oxide- containing mineral. CONSTITUTION:(A) An oxide of aluminum containing metallic aluminum, such as aluminum ash (with desirably 30-35wt.% metallic aluminum content) is blended with (B) an iron oxide, e.g., steel manufacturing scale, (C) an oxygen- containing boron compound e.g., borax, (D) a silicon oxide-containing mineral, e.g., molding sand, to provide a modifying agent for preventing disintegrating and weathering of steel manufacturing slag. The amount of the modifying agent added to the steel manufacturing slag is preferably 6-8wt.%. A method for blowing a granular or powdery modifying agent, together with a carrier gas, such as nitrogen gas, into a slag ladle containing the molten slag is efficient in reacting the modifying agent with the steel manufacturing slag.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for preventing the decay and weathering of slag generated during the steelmaking process using electric furnaces, converters, etc., particularly slag during the reduction stage of electric furnaces.

[Conventional technology]

Slag that is generally generated during the steelmaking process, especially electric furnace reduction stage slag (hereinafter simply referred to as steelmaking slag), quickly disintegrates and weathers when left in the atmosphere, and the generated fine powder scatters, causing dust pollution. At the same time, it becomes difficult to transport and handle the slag, so an immediate solution is desired.

Conventionally, the cause of steelmaking slag collapsing and weathering in the atmosphere is thought to be mainly due to unreacted free quicklime (hereinafter referred to as F and CaO) contained in the slag in a relatively large amount. That is, free quicklime reacts with moisture in the air and water sprayed during slag cooling, generates slaked lime (hereinafter referred to as Ca(OH)z) while exothermic expansion, and also produces F, CaO and Ca( OH)2 absorbs carbon dioxide gas (hereinafter referred to as CO2) from the air and changes into calcium carbonate (hereinafter referred to as CaC○), so these fine powders such as slaked lime or calcium carbonate cause dust. .

In addition, dicalcium silicate (hereinafter referred to as 2Ca) contained in the slag
It is also thought that one of the causes that promotes the collapse and weathering of slag is that O.SiC2) also changes to γ-2Ca.SiO2, which has a large specific volume, depending on the cooling conditions such as rapid cooling.

Conventionally, as a method for preventing the disintegration of slag and the generation of dust, slate or shale, which melts at a temperature lower than that of the slag, has been added to the slag to remove F, CaO, and 7
2 Ca O-3i A method of adding only the amount necessary to substantially eliminate O2 and firing it from the outside (Japanese Patent Publication No. 57-
No. 2767) is known.

However, in this method, in addition to the cost of additives such as slate or shale, the heat source for firing is bulky.
It has the disadvantage of high cost.

In order to improve the drawbacks of the conventional method, the present invention has invented a method of adding a blended composition consisting of aluminum ash, iron oxide, and silica to slag and melting it to solidify it, and has filed a patent application for the method. No. 61-295263). However, even the modified slag obtained by this method was not satisfactory in preventing collapse in severe storage environments such as high temperature and high humidity.

[Problems to be Solved by the Present Invention] The present invention has been made by focusing on such drawbacks of the conventional methods, and it is possible to solve the problem of mutual interaction between the modifier that can be obtained at low cost as industrial waste and the compounds mixed in the modifier. By skillfully utilizing the reaction heat generated by chemical reactions, it is possible to quickly, at low cost,
The purpose of the present invention is to provide an improved method that reliably solidifies steelmaking slag stably and prevents it from collapsing and weathering.

[Means to solve the problem]

That is, the present invention is directed to aluminum oxides and iron oxides containing metallic aluminum such as aluminum ash.

The gist of the present invention is to provide a modifier for preventing disintegration and weathering of steelmaking slag, which is formed by blending an oxygen-containing boron compound and a silicon oxide-containing mineral, and to melt and react the steelmaking slag with the modifier described in nil, and then solidify the same. This is a method for preventing the collapse and weathering of steelmaking slag.

In the present invention, the blended composition added as a modifier for steelmaking slag is selected from four types of aluminum oxides, iron oxides, oxygen-containing boron compounds, and silicon oxide-containing minerals. However, there are no particular restrictions on the quality or purity of any of these, and for example, those generated as industrial waste can be used as they are. Of course, as an aluminum oxide containing metallic aluminum, so-called aluminum ash, which is generated on the surface of molten aluminum oxide 1, is used, for example, when refining metallic aluminum or recycling metallic aluminum from aluminum scraps. An example of its composition is shown in Table 1.

Table 1 (%) Metallic aluminum (hereinafter referred to as M-AN) contained in the composition of this aluminum ash reacts with iron oxide, which is another compound, to produce high-grade aluminum based on the so-called thermite reaction. In addition to being used to obtain reaction heat, free quicklime in steelmaking slag is used to generate alumina (hereinafter referred to as Ap) in aluminum ash.
203) to produce a stable compound. Therefore, the content of M-Aff in aluminum ash is preferably about 30 to 35% (in this specification, % represents weight % unless otherwise specified).

In addition, iron oxide is mainly used for the thermite reaction with M-AP mentioned above, and is also used to generate stable compounds by reaction with free quicklime, and its form is Fez○3. ,F e,.

04, FcO may be used. As the iron oxide, it is possible to use so-called steelmaking scale, whose main component is iron oxide, which is generated during the manufacturing of steel products, such as continuous casting, rolling with steel ingots and billets, and forging. can. Table 2 shows an example of the composition of steelmaking scale.

Further, as the oxygen-containing boron compound, boric acid or a boric acid compound such as borax can be used.

Further, as the silicon oxide, foundry sand, river sand, etc., which are waste materials such as silica sand, can be used, and an example of the composition of foundry sand is shown in Table 3.

The blending ratio of the modifier of the present invention consisting of aluminum oxide, iron oxide, oxygen-containing boron compound, and silicon oxide-containing mineral containing aluminum metal is, for example,
It is preferably within the range shown in the table.

Table 4 The addition ratio of the modifier to the steelmaking slag, consisting of the compounding ratios shown in Table 4, varies depending on the content of free quicklime in the steelmaking slag, etc., but from the viewpoint of smooth reaction with the molten slag, the addition ratio is approximately 6 It is desirable that it be 8%.

The modifier of the present invention can be applied to steelmaking slag produced in the process of producing any type of steel.
'Can be similarly applied.

In addition, when reacting the modifier of the present invention with steelmaking slag, for example, the modifier is placed in advance in the form of a shell or in an appropriate package at the bottom of a slag pan, and the molten slag is poured into this. However, a method in which a granular or powdered modifier is blown into a slag pot containing molten slag through a lance tube together with a carrier gas such as air or nitrogen gives good results. That is, when the modifier is brought into contact with the molten slag by blowing it together with a carrier gas, the modifier reacts violently, generates heat and foams, and convective stirring occurs, producing uniform modified slag in a short period of time very efficiently.

The modified slag thus obtained is extremely stable after solidification and resists disintegration and weathering.

[Example 1] The present invention will be explained in more detail below based on examples.

In the attached drawings, 1 is a slag pot, and a lid 2 is equipped with a lance pipe 3 for pressure-feeding the modifier and a chimney 4 for exhaust gas on the top thereof.
is crowned. 5 is a hooking post provided on the upper side wall of the slag pot 1, and 6 is a molten slag.

After loading 8 tons of steelmaking slag having the composition shown in Table 5 into the slag pot 1 having such a structure and putting a lid on it, 650 kg of the modifier having the composition shown in Table 6 was poured into the lance tube 3 at an air pressure of 3 to 5 kg.
/ctl was sent. The transfer took about 5 minutes.

Table 6: 50°C. The slag rapidly reacted with the injected modifier and reached a temperature of 1520°C, melting and boiling.

After the reaction was completed, the slag was allowed to cool and solidify.

It was confirmed that the slag solidified by the above method did not disintegrate at all even if it was left in an atmosphere with a humidity of 80% for 30 days or more.

The composition of the solidified slag after treatment is as shown in Table 7, and F is the main cause of slag collapse.

CaO had disappeared.

[Example 2] 650 kg of the same modifier as in Example 1 was placed in advance in a slag pot, and 8 tons of molten steelmaking slag was poured into it, and then the two were allowed to react.

Although the reaction was slower and took longer than in Example 1, the properties of the solidified slag obtained after sufficient gas stirring were almost the same as the solidified slag of Example 1.

[Example 3] 8 tons of steelmaking slag was loaded into the slag pot in the same manner as in Example 1,
650 kg of a modifier having the composition shown in Table 8 were likewise introduced with air.

Table 8 The composition of the solidified slag after treatment is as shown in Table 9.
, CaO was not detected.

The solidified slag of this example not only had better weathering resistance but also higher hardness than the solidified slags obtained in Examples 1 and 2.

[Comparative Example] As a modifier, one having the composition shown in Table 10 (Japanese Unexamined Patent Publication No.
Steelmaking slag was modified in the same manner as in Example 1, except that Modifier No. 1-295263 was used.

Table 10 The composition of the assimilated slag obtained is as shown in Table 11.
Small amounts of F and CaO remained. The surface of such modified slag is slightly more prone to weathering than the modified slag of Example 1, and this is thought to be due to the difference in the content of F and CaO.

[For production]

In this way, free quicklime, which exists in slag and is the main cause of collapsing weathering, reacts with silica, aluminum oxide, or iron oxide in the modifier to form stable β-2CaO-3i.
Oz, 3CaO・Aj2z 03.3CaO・Fe2
In addition to being modified into O, etc., γ-2CaO-3iOz, which exists in an unstable state in the slag before treatment, also
The slag is modified into stable β-2CaCISiOz by heating and melting, thereby preventing the slag from collapsing and weathering.

In addition, such a slag modification reaction is accompanied by a thermite reaction between metallic aluminum in the aluminum ash mixed in the modifier and iron oxide in the scale, as shown in the following equation. Since the reaction is accelerated by the high heat of reaction generated, the reaction is carried out quickly and uniformly.

2A/! +Fez 03 →2Fe+Anz 03+QKc a 1 The coexistence of oxygen-containing boron compounds further promotes such a reforming reaction, and some of them probably become complex oxides such as calcium borosilicate, causing the slag to disintegrate and weather. It is assumed that this contributes to

〔Effect of the invention〕

As explained in detail above, the present invention provides compounds necessary for stably solidifying free quicklime, which is the main cause of slag disintegration and weathering, and a heat source necessary for the reaction with these compounds, which are treated as industrial waste. Not only can it be carried out at an extremely low cost, but it can also be done using materials that have previously been
It also contributes to the effective use of industrial waste. In addition, the heat source required for the reaction is the heat of reaction between the compounds in the modifier, and the presence of the oxygen-containing boron compound allows the reaction between the quicklime and the modifier to proceed quickly and uniformly. However, there are advantages such as stable solidification of slag can be carried out reliably in a short period of time.

[Brief explanation of the drawing]

The drawing is a schematic vertical sectional view showing an example of an implementation device of the present invention. 1... Slag pot, 2... Lid, 3... Lance pipe, 4...
・Chimney for exhaust gas, 6... Molten slag.

Claims (5)

[Claims] (1) A modifier for preventing disintegration and weathering of steelmaking slag, which is made by blending an aluminum oxide containing metallic aluminum, an iron oxide, an oxygen-containing boron compound, and a silicon oxide-containing mineral. (2) The modifier according to claim 1, which comprises aluminum ash, iron oxide, a boric acid compound, and sand. (3) A method for preventing disintegration and weathering of steelmaking slag, which comprises subjecting the steelmaking slag and the modifier of claim 1 or 2 to a melting reaction and then solidifying the same. (4) Collapse weathering of steelmaking slag according to claim 3, wherein a modifier is added to a container containing molten steelmaking slag, or molten steelmaking slag is added to a container containing a modifier. How to prevent it. (5) The method for preventing disintegration and weathering of steelmaking slag according to claim 4, wherein the modifier is introduced under pressure together with the carrier gas.