JPH06206744A - Aging treatment of steel-making slag - Google Patents

Abstract

PURPOSE:To effectively utilize steam without loss and to shorten the aging period of slag by chemically analyzing the slag delivered from a steel-making furnace for each charge and carrying out the steam treatment of exclusively the slag having a basicity lower than a specific level. CONSTITUTION:In the aging treatment of steel-making slag under atmospheric pressure, the chemical analysis of slag delivered from a steel-making furnace is carried out for each charge to collect the slag of the charge having a basicity (CaO/SiO2) of >=4 and the collected slag is crushed, graded and aged with steam. The aging treatment time is remarkably shortened in the case of a slag having a basicity of <=4 to considerably decrease the consumption of steam. As a result, a high-quality slag sufficiently utilizable as a subbed material can be produced at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aging treatment method for preventing expansion and destruction of steelmaking slag used as a road material, and more particularly, in a method for aging treatment using steam under atmospheric pressure, The present invention relates to a method for aging treatment of steelmaking slag for stabilizing expansion and fracture resistance of steelmaking slag in a short time by effectively using steam without waste.

[0002]

2. Description of the Related Art Steelmaking slag is crystalline and hard, so that it is suitable as a roadbed material if it is crushed after cooling and adjusted to a predetermined grain size. However, in the case of steelmaking slag, some of the quicklime used during refining remains unreacted lime (free lime) that remains, and this has the property of hydrating expansion when it reacts with water, It is difficult to use steelmaking slag immediately after production as roadbed material.

As a countermeasure for this, generally called aging, the crushed slag is piled up in the atmosphere, and the free lime spontaneously undergoes a hydration reaction to stabilize the expansive fracture property before being used. Was there. However, this method requires a period of at least 6 months or more to stabilize the expansion and fracture resistance, requires a vast aging yard, is inefficient, and requires labor such as lot management. was there.

In view of such circumstances, various methods for shortening the aging period have been developed. Among them, a typical method is an aging treatment method using water vapor. This method is a method of accelerating the hydration reaction of free lime in steelmaking slag by the heat of steam and excess water. Specifically, steam is ejected as a means of reacting steam with steelmaking slag. There are a method of forming a steelmaking slag layer in the high-temperature steam pipe, a method of putting the steelmaking slag in the hopper, and ejecting steam from the bottom of the hopper.

[0005]

However, the aging treatment method of steelmaking slag using steam has a great effect of promoting the hydration reaction of free lime in the steelmaking slag, but since the manufacturing cost of the steam used is high, Considering the economical efficiency of this aging treatment, it is necessary to reduce the amount of steam used as much as possible. However, conventionally, the amount of steam used has not been controlled in consideration of the economical efficiency of the aging treatment, and the aging treatment cost of steelmaking slag is high in reality.

In view of this situation, the present invention intends to propose a method for aging treatment of steelmaking slag which can effectively reduce the aging period of steelmaking slag by effectively using the steam without waste in order to reduce the cost of aging treatment by steam. It is a thing.

[0007]

As a result of various studies as means for solving the above problems, the present invention has a clear correlation between slag free lime and slag basicity, and the lower the slag basicity is, the steam aging time is lower. We found that the aging process was short and found an aging treatment method that can reduce steam cost. That is, the gist of the present invention is that chemical analysis of the slag generated from the steelmaking furnace is performed for each charge when steam-aging the steelmaking slag under atmospheric pressure, and the basicity (CaO / SiO ₂ ) of 4 or less is used. It is characterized in that only the slag is separated and collected, the slag is crushed, the particle size is adjusted, and the steam aging treatment is performed.

[0008]

The purpose of performing steam aging of steelmaking slag is to remove free lime (f-Ca) contained in the slag as described above.
This is to promote the hydration reaction of O). The hydration reaction of CaO is higher than the dissociation temperature (K ₂ ) of the reaction intermediate in the reaction temperature range lower than 473K (200 ° C). That is, at a temperature of 200 ° C. or lower, the hydration reaction of CaO takes precedence, and the higher the temperature, the higher the reaction rate.

Therefore, it can be said that 200 ° C. is preferable for promoting aging. However, since the steam temperature does not become higher than 100 ° C. under the atmospheric pressure, the slag temperature may be controlled to 100 ° C. as the maximum value in the steam aging treatment under the atmospheric pressure.

However, steelmaking furnaces tend to have a large variety of products and small lots as the demand diversifies, and the types of steels to be refined are increasing. The refining method differs depending on the steel type, and the amount of auxiliary materials such as quick lime, which is the source of slag, also varies. Therefore, the refining of various types of steel varies with the properties of the slag generated. Therefore, as a result of examination, it was found that the difference in the expansion stabilization time of the steelmaking slag due to the aging treatment is caused by the difference in the properties of these slags.

As a matter of course, the steam aging time is longer when the amount of free lime contained in the slag is larger, and is shorter when the amount is smaller. Therefore, in order to shorten the steam aging time and reduce steam cost, grasp the free lime of slag for each charge, collect only the slag with a small amount of free lime separately at the slag treatment plant, and steam age the slag. You can use it. For that purpose, it is necessary to grasp the amount of free lime in the slag while the slag is discharged from the steelmaking furnace and transported to the slag treatment plant (about 30 minutes to 1 hour). However, the amount of free lime must be determined by a chemical analysis method using ethylene glycol extraction,
This method is not practically applicable because the analysis takes a long time.

By the way, FIG. 1 shows the relationship between slag free lime and slag basicity, and there is a clear correlation between the two. Moreover, the component analysis of CaO and SiO _{2 in} the slag can be performed in a very short time (within 10 minutes) by VXQ analysis or the like. Therefore, the slag basicity for each charge is used as a control value, the slag with a low slag basicity is collected separately at the treatment plant, and the aging treatment time is shortened by steam aging the low basicity slag, thereby reducing the steam cost. Can be reduced. The slag basicity for shortening the slag aging treatment time and reducing the steam cost is preferably 4 or less, and particularly preferably less than 3. This is because when the slag has a slag basicity of 4 or less, the aging treatment time is significantly shortened, and the amount of steam used can be significantly reduced.

[0013]

2 is a schematic plan view showing an example of an aging treatment facility for carrying out the method of the present invention, and FIG.
It is a vertical cross-sectional front view taken along the line A, and a square steelmaking slag processing tank having one side wall as a slag loading / unloading gate will be described as an example here. In the figure, 1 is a slag treatment tank whose bottom and side walls are made of concrete, 2 is a steam supply main pipe, 3 is a steam injection pipe, 4 is a steam flow rate control valve, 5 is a thermometer, 6 is a flow rate control valve control device, 7 is a crushed stone layer, 8 is a steelmaking slag layer, and 9 is a vinyl sheet.

That is, in the above equipment, the temperature of the upper layer of the steelmaking slag layer 8 is constantly measured by the thermometer 5, and the steam flow rate control valve 4 is controlled by the flow rate control valve control device 6 based on the measured value.
Is a mechanism that is controlled.

The steelmaking slag layer 8 in the slag treatment tank 1 is aged by the steam injected from the steam injection pipe 3. At this time, due to the action of the crushed stone layer 7 interposed between the steelmaking slag layer 8 and the steam injection pipe 3, stable vapor permeability can be ensured and the slag can be easily carried in and out.

Example 1 Slag sampled for each charge of a 300 ton converter was steam-aged using the aging treatment equipment shown in FIGS. 2 and 3. The change with time of the expansion amount at that time was obtained. In addition, chemical analysis of slag is performed and free lime (f
-CaO) and the value of slag basicity, the relationship between the expansion amount and the aging time was obtained. The result is shown in FIG. FIG. 4 shows the relationship between the steam aging time and the water immersion expansion ratio of each slag having a free lime (f-CaO) content of 3% or more and 3% or less.

From the results shown in FIG. 4, free lime (f-Ca
It was found that when O) is high, the amount of expansion before aging is also high, and it takes a long time for the amount of expansion to reach a certain value or less due to aging.

FIG. 5 shows the result of the relationship between the basicity and the steam aging time required for the water immersion expansion ratio to be 0.5% or less. As is clear from the results of FIG. 5, the lower the slag basicity, the shorter the aging time. Further, Table 1 shows the results of obtaining the slag basicity and the amount of steam used. From Table 1, the lower the slag basicity, the more the amount of steam used can be reduced, and when the slag has a slag basicity of less than 3,
It can be seen that the steam consumption can be reduced by about 40% as compared with the slag having a slag basicity of 3 or more.

[0019]

[Table 1]

[0020]

As described above, according to the method of the present invention, the amount of steam used can be significantly reduced by separately collecting the low basicity slag, and the steam aging treatment cost can be significantly reduced. Also, regarding the slag quality, it is possible to economically obtain a high-quality slag that can be sufficiently used as a roadbed material, and it is possible to effectively use the steelmaking slag.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between free lime of steelmaking slag and slag basicity.

FIG. 2 is a schematic plan view showing an example of an aging treatment facility for carrying out the method of the present invention.

FIG. 3 is a vertical sectional front view taken along the line AA of FIG.

FIG. 4 is a diagram showing a relationship between a steam aging time and a water immersion expansion ratio of each slag having an amount of free lime (f-CaO) of 3% or more and 3% or less in an example of the present invention.

FIG. 5 is a diagram showing the relationship between the basicity and the steam aging time for the water immersion expansion ratio to be 0.5% or less in the above-mentioned Example.

[Explanation of symbols]

 1 Slag processing tank 2 Steam supply main pipe 3 Steam injection pipe 4 Steam flow control valve 5 Thermometer 6 Flow control valve control device 7 Crushed stone layer 8 Steelmaking slag layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masamochi Wakiyama 1 Kunomi-cho, Kokurakita-ku, Kitakyushu City Sumitomo Metal Industries, Ltd. Kokura Steel Works

Claims (1)

[Claims] 1. A method for aging a steelmaking slag carried out under atmospheric pressure, wherein chemical analysis of slag generated from a steelmaking furnace is carried out for each charge to obtain a basicity (CaO / SiO ₂ ).
A method for aging treatment of steelmaking slag, characterized in that only slag having a charge of 4 or less is separately collected, and the slag is crushed and the particle size is adjusted to perform steam aging treatment.