JPH10338557A - Aging treatment of steel making slag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aging treatment method capable of rapidly and sufficiently stabling the expansion destructiveness of steel making slag and reducing an aging treatment cost. SOLUTION: At the time of subjecting the steel making slag to the steam aging treatment, the steel making slag is subjected to the steam aging treatment by predicting the amt. of the water seepage expansion of the steel making slag before the aging treatment in accordance with the charging basicity [C/S] and the fluorine concn. [F] in the slag at the time of blowing in a steel making process, determining the steam aging pattern and aging treatment time of the slag and determining the amt. of the water seepage expansion of the steel making slag after the steam aging treatment according to the aging pattern and the treatment time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aging treatment technique for effectively utilizing steelmaking slag generated in a steelmaking process of a steel mill or the like as a roadbed material, etc. The present invention relates to an aging treatment method for steelmaking slag which stabilizes and reduces the aging treatment cost.

[0002]

2. Description of the Related Art In steelmaking slag generated in a steelmaking process, a large amount of lime added during refining remains in slag as free lime, and the free lime remaining in the slag has high reactivity with water, It has expandability due to volume expansion during the summation reaction. Therefore, in order to use the steelmaking slag having such expansion and destruction properties as a roadbed material or the like, a stabilization treatment for suppressing expansion is necessary.

[0003] As a method for stabilizing steelmaking slag, natural aging in which the steelmaking slag is left in a piled state is generally used, but this method requires several months to obtain a sufficient stabilizing effect. For this reason, in recent years in which the promotion of reuse of steelmaking slag has become important due to the enforcement of the Recycling Law, various aging treatment methods for shortening the period and improving the stabilizing effect have been proposed.

For example, Japanese Patent Application Laid-Open No. 57-57815 proposes an aging method in which converter slag after crushing is wetted, subjected to natural aging treatment in piles for 15 days, and further maintained in a saturated state for 30 days. I have. However, although this method can shorten the period compared to natural aging that is left in a piled state, it still requires a period of up to 1.5 months, and it cannot sufficiently stabilize the free lime in the pores of the slag surface. Has disadvantages.

Also, Japanese Patent Application Laid-Open No. 61-101441 discloses an aging method in which crushed slag is exposed to air for 48 hours or more in the atmosphere while heating by blowing high-temperature steam containing water into a pile of slag. Proposed. However, in order to obtain a sufficient aging effect with this method,
There is a problem that a long steam aging period assuming a highly expandable slag must be employed, and a large amount of steam is required.

Further, Japanese Patent Application Laid-Open No. 4-202134 proposes a method of treating steelmaking slag by combining natural aging treatment and steam aging treatment.
No. 62346 proposes a method of controlling the slag basicity to 2.0 to 5.0 by weight in the steelmaking process and aging slag to which a melting point depressant such as fluorite is added. Both require a large amount of steam because the aging process cannot be performed according to each slag, as in the case of the above-mentioned conventional technology.In addition, in order to perform the aging process according to each slag, the rough stone generated in the steelmaking process is required. There is a problem that it is necessary to temporarily place the tentatively at the stage to check the expansion amount, and it is economically disadvantageous because the transportation cost and the slag management cost at the temporary yard increase.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems of the prior art. In reusing steelmaking slag as a roadbed material, the expansion and destruction of steelmaking slag can be reduced in a short time. It is an object of the present invention to propose a method of aging steelmaking slag which can be sufficiently stabilized and can reduce the aging treatment cost.

[0008]

The aging treatment method for steelmaking slag according to the present invention is based on aging based on the basicity of charge [C / S] and the fluorine concentration in slag [F] during blowing in the steelmaking process. Predict the amount of water immersion expansion of the steelmaking slag before treatment, determine the steam aging pattern and the aging treatment time of the slag, and determine the amount of water immersion expansion of the steelmaking slag after the steam aging treatment according to the aging pattern and the treatment time. And a steam aging treatment.

[0009] The expansion destructibility of steelmaking slag is a phenomenon that occurs when free lime is contained therein to cause the following reaction to cause volume expansion. CaO + H ₂ O → Ca (OH) ₂ (hydration reaction)… CaO + CO ₂ → CaCO ₃ (carbonation reaction)…

[0010] These free limes include calcium lime added for the purpose of removing impurities in molten steel in the steelmaking process, CaO components contained in lightly burnt dolomite, etc., which remain without reacting sufficiently, and Such a reaction is generated during the cooling process of the slag. 3CaO.SiO ₂ → 2CaO.SiO ₂ + CaO ...

[0011] The expansion and destruction of the steelmaking slag due to the volume expansion of the free lime causes problems such as cracks and undulations in the road when used as a roadbed material or the like. To suppress the expansion and destruction. In general, the steam aging treatment is performed by flowing steam from below the piled steelmaking slag. In addition, since the hydration reaction shown above is an endothermic reaction, when aging treatment is performed, the steelmaking slag piled up in the aging pit is covered with a sheet or the like to take measures against heat radiation, and the aging atmosphere is reduced to about 100 ° C. The reaction can be promoted by maintaining the temperature.

[0012] The steam aging is a heating process in which the steam is started to flow after being stacked in the pit and the temperature is raised to a predetermined temperature.
After the temperature reaches a predetermined temperature, the temperature is maintained for a certain period of time, and the temperature is lowered by stopping the steam flow and the temperature is lowered. The steam aging pattern is adjusted by the holding time of each of these processes.

The amount of expansion of the steelmaking slag after steam aging depends on the amount of expansion of the steelmaking slag before steam aging, and the amount of reduction in expansion due to steam aging can be adjusted by the steam aging pattern and the processing time. is there.

By the way, the amount of water immersion expansion when steelmaking slag is used as a roadbed material is specified in JISA-5015 to be less than 1.5%, and the expansion amount of all steelmaking slag is kept within its reference value. There is a need. For this reason, in the conventional method, the aging pattern and time had to be set on the assumption that steelmaking slag having a large expansion amount before steam aging was mixed.

According to the present invention, the expandability of the steelmaking slag depends on the amount of free lime contained in the slag, and the amount of free lime contained in the steelmaking slag depends on the use of a solvent added during the steelmaking process. It has been found that the amount can be determined by blowing conditions. This will be described in detail below.

The relationship between the blowing conditions in the steelmaking process and the amount of water immersion expansion before steam aging varies depending on the steelmaking process used, but the correlation between the blowing conditions in the steelmaking process and the amount of water immersion expansion before steam aging. It is possible to determine the aging pattern and the treatment time by determining the slag, and to adjust the amount of water immersion expansion of the steel slag after steam aging to a desired value. Here, the water immersion expansion amount of the steelmaking slag before the aging treatment is predicted by, for example, the following formula 1 based on the basicity of charge [C / S] and the fluorine concentration in the slag [F] during the blowing in the steelmaking process. So you can
From this predicted value, the steam aging pattern and the aging processing time of the slag can be determined.

[0017]

[Equation 1] [C / S] −3.6 × [F]

That is, since the amount of water immersion expansion before steam aging can be predicted in the steelmaking process, the steam aging pattern and the aging treatment time for each steelmaking slag can be determined. Therefore, the presence of a slag having a high expansion amount during steam aging is assumed. Without this, steam aging according to the amount of slag expansion becomes possible.

In the present invention, the conditions for estimating the water immersion expansion of the steelmaking slag before the aging treatment are as follows:
The basicity of charge [C / S] and the fluorine concentration in slag [F] at the time of blowing were used for the following reasons. That is, in the blowing conditions in the steelmaking process, the initial input amount of a medium solvent represented by quick lime, lightly burned dolomite, raw dolomite, limestone, etc. (calcia and silica content may be expressed as basicity. ), The blowing time, the amount of medium solvent charged during blowing, the amount of slag accelerator (fluorite, soda ash, etc.) charged, the silicon content of the hot metal used, the temperature of the molten steel during blowing, etc. This is because it was found that the basicity of charge [C / S] and the concentration of fluorine in the slag [F] most affected the water immersion expansion of the steelmaking slag before the aging treatment. The basicity of charge [C /
S] is calculated from CaO and SiO _{2 in the} raw material. The fluorine concentration [F] in the slag is calculated from the added amount of fluorite (CaF ₂ ) as a slag formation accelerator.

[0020]

FIG. 1 is a block diagram showing a basic manufacturing process of the present invention, FIG. 2 is a schematic diagram showing an example of a steam aging facility, (A) is a plan view, and (B) is a diagram (A). 1 is a concrete slag treatment tank, 2 is a steam supply pipe, 3 is a steam injection pipe, 4 is a steam flow control valve, 5 is a crushed stone layer, 6 is a steelmaking slag layer, 7 Is a heat insulating sheet.

That is, in the present invention, in the steelmaking process such as a converter, steelmaking blowing conditions are extracted from the steelmaking process computer, and the basicity of charge [C / S] and the fluorine concentration in the slag [F] during the blowing are used. The amount of water immersion expansion before the aging treatment is predicted by the above equation 1, and the steam aging pattern and the aging treatment time of the slag are determined. Next, after the generated steelmaking slag is crushed in the slag crushing step and subjected to particle size adjustment, it is loaded on an aging pit, and after the steam aging treatment according to the steam aging pattern and the aging treatment time determined by the steelmaking blowing conditions. The amount of water immersion expansion of the steelmaking slag is determined, and a steam aging treatment is performed.

In the steam aging equipment shown in FIG. 2, a steel slag layer 6 is laid on the bottom surface of a slag treatment tank 1 and a steelmaking slag layer 6 is formed on the steam injection pipe via a crushed stone layer 5 having a predetermined grain size. The flow rate of the steam supplied to the slag processing tank 1 is adjusted by a steam flow control valve 4 provided in the steam supply pipe 2. Note that the crushed stone layer 5 is provided to ensure stable air permeability of steam, and the heat retaining sheet 7 is placed on the steelmaking slag layer 6 to prevent heat radiation.

[0023]

[Embodiment] The aging equipment shown in FIG.
The results of aging the slag generated from the converter by applying the method of the present invention are shown below. In the present embodiment, the converter blowing conditions are taken out from the converter process computer, and the water immersion expansion amount of the converter slag before the aging treatment is predicted based on the blowing conditions shown in Table 1. Therefore, the steam aging pattern of the slag and the aging treatment time were determined. In addition, the predicted value of the amount of water immersion expansion in Table 1 was obtained by the above equation 1. Further, in determining the logic shown in Table 2, the relationship between the converter blowing condition shown in FIG. 3 and the amount of water immersion expansion of the converter slag before aging treatment, and the amount of water immersion expansion before steam aging shown in FIG. And the relationship between the amount of water immersion after aging. [C / S] in FIG. 3 indicates a calculated value of the basicity of charge in the converter, and [F] indicates an F concentration in slag calculated from the added amount of fluorite. From these correlations,
The logic was obtained from the relationship between the amount of water immersion expansion before steam aging, the steam aging period, and the amount of water immersion expansion after steam aging from the converter blowing conditions.

The slag generated from the converter is then crushed with a jaw crusher and a cone crusher, and then sieved with a vibrating sieve to a predetermined particle size (the maximum particle size at the time of crushing is 10 to 20% larger than the JIS standard maximum particle size). The steam aging treatment was carried out according to the steam aging pattern and the aging treatment time determined by the above-mentioned converter blowing conditions.

Table 3 compares the results of the present invention with those of the conventional method.
Shown in The conventional method is a processing method combining natural aging and steam aging. As is evident from the results in Table 3, all the converter slags subjected to the steam aging treatment according to the method of the present invention are less than the water immersion expansion amount of 1.5% (JIS standard) which is the standard as the roadbed material, and the problem due to the expansion is obtained. There are no outbreaks. On the other hand, although the converter slag according to the conventional method satisfies the standard for the roadbed material in terms of the amount of water swelling, the aging period is long and a large amount of steam is required, which is economically disadvantageous. In addition, it has been confirmed that the slag having a large initial expansion amount cannot be sufficiently reduced even if the aging period or the like is extended, and is unsuitable as a roadbed material.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

As described above, the present invention predicts the amount of water immersion expansion of steelmaking slag before steam aging in the steelmaking process, determines the steam aging pattern and aging treatment time of the slag, and determines the aging pattern and the aging treatment time. Since it is a method of performing the steam aging treatment by determining the amount of water immersion expansion of the steel slag after the steam aging treatment according to the treatment time, without assuming the presence of a slag of a high expansion amount during the steam aging of each steelmaking slag,
Steam aging according to the amount of slag expansion is possible, stabilizing the expansion and destruction of steelmaking slag sufficiently in a short period of time, and reducing the aging treatment cost, which has a great effect on promoting the recycling of steelmaking slag. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic manufacturing process of the present invention.

FIGS. 2A and 2B are schematic views showing an example of a steam aging facility according to the present invention, wherein FIG. 2A is a plan view, and FIG.

FIG. 3 is a diagram showing the relationship between converter blowing conditions and the rate of water immersion expansion of converter slag before aging treatment in an example of the present invention.

FIG. 4 is a diagram showing a relationship between a water immersion expansion coefficient before steam aging, a steam aging pattern and a water immersion expansion coefficient after aging in the same embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slag processing tank 2 Steam supply pipe 3 Steam injection pipe 4 Steam flow control valve 5 Crushed stone layer 6 Steelmaking slag layer 7 Heat insulation sheet

Claims (1)

[Claims] 1. A method for steam aging a steelmaking slag, wherein the basicity of charge at the time of blowing in the steelmaking process [C
/ S] and the fluorine concentration in the slag [F], the amount of water immersion expansion of the steelmaking slag before the aging treatment is predicted to determine the steam aging pattern and the aging treatment time of the slag, and the aging pattern and the treatment time are determined. A water immersion expansion amount of the steelmaking slag after the steam aging treatment is performed according to the following formula, and performing the steam aging treatment.