JP2001048605A - Treatment of steelmaking slag for cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment process for steelmaking slag used for cement, which enables effective utilization of free CaO, reduction in water content of dephosphorization/desulfurization slag, accordingly, enhancement of efficiency of separation/removal of granular iron, inhibition of dephosphorization/ desulfurization slag from being deposited or accumulated in a crushing stage or magnetic separation treatment stage. SOLUTION: This treatment process comprises: conveying and discharging slag 10 formed in dephosphorization/desulfurization stages of a steelmaking process, to a treatment yard 13; spraying water on the slag 10 to cool the slag; crushing large lumps of the slag 10 to remove metal; thereafter, once stacking up the crushed slag 10 to reduce the water content of the slag to <=10 wt.% by the heat of reaction of CaO in the slag 10; then further crushing the resulting slag 10; and separating and removing granular iron from this slag 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating steelmaking slag for cement used as a raw material for cement by removing metals such as iron and steel from slag generated in a dephosphorization and deflow process of steelmaking.

[0002]

2. Description of the Related Art Conventionally, in the steelmaking process, in order to remove impurities such as phosphorus and sulfur from hot metal, decarburize hot metal and scrap iron, and remove impurities, refining is performed using auxiliary materials such as quicklime and iron oxide. Must be performed, resulting in a large amount of slag. This slag is dephosphorized from hot metal,
It is divided into so-called hot metal pretreatment slag (dephosphorization, degassing slag) generated by degassing or the like, and slag (converter slag) generated from refining of a converter or the like. Among them, converter slag is similar to blast furnace slag in its main component, and is subjected to aging treatment to remove impurities such as metal (granular iron) and used as roadbed material, soil improvement material, cement clinker, etc. And recycling is being actively promoted. In addition, dephosphorization and degassing slag are remarkably weathered and expanded, and have been disposed of in landfills. In recent years, recycling of resources has been actively promoted. As a typical method, Japanese Unexamined Patent Publication (Kokai) No. 7-223857 discloses that one of coal ash, silt, and blast furnace slag is added to converter slag, dephosphorization, and outflow slag.
By mixing 1 to 30% by weight of a seed or two or more kinds and treating with steam or warm water, free CaO of slag particles is reacted in the presence of water with soluble silica contained in coal ash, silt, etc. CaO ・ SiO ₂・ H ₂ O
It describes that a gel is formed, weathering and swelling are suppressed, and the gel is used for roadbed materials and the like. However, in order to expand the use of dephosphorization and dewatering slag and to recycle resources into high value-added cement raw materials, it is necessary to use metals (granular iron) and chlorine ions contained in dephosphorization and dewatering slag. And so on.
As a countermeasure, for example, Japanese Patent Application Laid-Open No. 8-198647 discloses that slag generated in a dephosphorization and deflow process is cooled with fresh water containing little chlorine, and crushing and magnetic separation are performed a plurality of times to obtain chlorine and granular iron. Dephosphorization and degassing slag with less
It is described to be used as a cement raw material.

[0003]

However, in the method described in Japanese Patent Application Laid-Open No. 8-198647, dephosphorization,
Although the concentration of chlorine in the effluent slag can be reduced, since there are many free CaO and fine granular iron, if the moisture in the slag is high, even if the granular iron is removed by crushing and magnetic separation,
The products and the like due to the reaction of free CaO adhere to the surface of the granular iron, and the adsorption of the nonmagnetic adherence to the magnetic separator causes a decrease in the sorting (magnetic separation) efficiency and the like. The content of granular iron cannot be reduced. In addition, when the crushing step or the magnetic separation step is performed, the dephosphorization and the adhesion of the outflow slag are increased, and the adhesion to a feeding device such as a chute, a transfer device such as a belt conveyor, and the like are caused. Removal and repair are troublesome, and there are problems such as stoppage of processing and the like, which hinders stable operation.

The present invention has been made in view of the above circumstances, and effectively utilizes free CaO to reduce the water content of dephosphorization and degassed slag to increase the efficiency of sorting and removing granular iron. It is an object of the present invention to provide a method for treating steelmaking slag for cement, which suppresses the adhesion and deposition of dephosphorization and outflow slag in a magnetic separation process.

[0005]

According to the present invention, there is provided a method for treating steelmaking slag for cement according to the present invention, wherein the slag generated in the dephosphorization and deflow processes of steelmaking is conveyed, discharged to a treatment yard, and discharged. After cooling and crushing the large slag lump and removing the ingot, the slag is temporarily stacked and the water content is reduced to 10% by weight or less due to the heat of reaction of CaO contained in the slag. Then, the slag is crushed, and the granular iron contained in the slag is sorted out and removed. By this method, the heat of reaction of free CaO can be effectively utilized to reduce the water content of dephosphorization and degassed slag (hereinafter referred to as slag) to a predetermined value. Adhesion can be suppressed, the efficiency of sorting and removing granular iron can be increased, and adhesion and accumulation of slag in the crushing step and the magnetic separation processing step can be prevented.

Here, the slag can be stacked indoors. Thereby, since the slag is dried by using the heat generated by the hydration reaction of the slag having a high content of free CaO, the water content of the slag can be stably reduced to a predetermined value, and the efficiency of removing granular iron is further improved. And increase the value of utilization as a resource.

Further, it is preferable that the sorting and removal of the granular iron is performed by a magnetic separator. Thereby, it is possible to reliably remove the granular iron in the slag, and when using it as a raw material such as cement clinker, to suppress wear of the crusher due to the mixed granular iron, and to reduce the granular iron contained in the cement. The quality of the cement can be improved by preventing the expansion and the like of the cement due to corrosion.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. FIG. 1 is an explanatory diagram of processing steps of a method for processing steelmaking slag for cement according to one embodiment of the present invention,
FIG. 2 is a graph showing the relationship between the water content of raw ore slag and the content of granular iron in the product slag, and FIG. 3 is a graph showing the relationship between the number of drying days and the water content of raw ore slag. As shown in FIG.
A method for treating steelmaking slag for cement according to an embodiment of the present invention will be specifically described. First, dephosphorization or desulfurization treatment of refined steel is performed by a pretreatment furnace (not shown) to remove impurities in the hot metal, and the generated slag 10 is discharged from the pretreatment furnace to a waste pan 12 placed on a waste truck 11. I do. Slag 10 in waste pan 12 conveyed by waste trolley 11
Is almost molten (partly solidified). The waste trolley 11 is transported to the processing yard 13 and the waste trolley 11
The slag 10 is tilted, and the slag 10 is poured into the treatment yard 13 and spread in a fan shape. At the same time, the slag 10 is completely solidified by water cooling, forced cooling and air cooling, and the surface temperature is reduced to 30. ６０60 ° C. The solidified slag 10 is broken by a shovel or the like to break up a large lump, the mixed large metal is absorbed and removed by a rif mag or the like, and further, the slag 10 is crushed to 80 mm or less to become an ore. Make slag 10. The slag 10 containing 11 to 15% by weight of water is conveyed by a self-loader or a truck, and is loaded on the indoor aging treatment plant 14 at a height of 2 to 5 m.

In this state, aging treatment is performed for 7 to 10 days. The stacked slag 10 has a CaO of 4
0-60wt%, SiO ₂ is 5 to 20 wt%, Al ₂ O
₃ is 4 to 15 wt%, mainly composed of 10 to 25 wt% ferric oxide, the inner CaO contains free CaO unbound and the like SiO ₂ and Al ₂ O ₃ 5 to 10 wt% . The free CaO causes a hydration reaction with the water of the slag 10 to generate heat, conducts heat to the stacked slag 10 slowly and dries the slag 10, and can reduce the water content of the slag 10 to 10% by weight or less. . Moreover, since the free CaO is dried by self-heating, the adhesiveness of Ca (OH) _{2 and the} like generated by the hydration reaction is suppressed, and it is possible to prevent the Ca (OH) _{2 from} adhering to the granular iron. And magnetic separation can be performed efficiently, and the granular iron in the slag 10 can be reduced significantly. In particular, as the water content of the slag becomes lower, the efficiency of sorting of granular iron can be stably increased. However, when the content is less than 3% by weight, dust is generated and the working environment deteriorates. Therefore, when the content is 3 to 8% by weight, more preferable results are obtained.

FIG. 2 shows the result of investigation on the residual ratio of granular iron in product slag when the water content of raw ore slag changes.
If the moisture content of the slag after drying exceeds 10% by weight, the residual ratio of the iron granules in the product slag may exceed the upper limit of 10%, which indicates that the quality of the cement cannot be stably satisfied. . This is because slag or Ca (O
H) ₂ powder or the like adheres, and the efficiency of magnetic separation decreases. Therefore, when the water content in the slag is reduced and, for example, magnetic separation is performed once (○ in the figure), if the slag water content is 7% by weight or less, the residual ratio of granular iron in the product slag is 10% or less. be able to. In addition, when the magnetic separation is performed twice (● in the figure) and the slag moisture is 10% by weight or less, the residual ratio of the granular iron in the product slag can be 10% or less. However, if the water content of the slag is lower than 3% by weight, the efficiency of crushing and magnetic separation of granular iron can be increased, but the generation of dust becomes extremely violent, which leads to an increase in the size of the dust collector and a deterioration in the working environment. In addition, FIG. 3 shows the results of an investigation of the case where the slag is dried outdoors and indoors in order to dry the slag.
Since drying using free CaO cannot be performed due to excessive moisture in the slag, the slag moisture in the slag is reduced to the area A.
In some cases, the variation becomes large and exceeds 10% by weight. In contrast, in the indoor drying according to the present embodiment (● in the figure), the water content of the slag can be stably reduced to 10% by weight or less in a short period of time. this is,
Since the water adhering or penetrating into the slag is evaporated and dried by the heat reacted with the free CaO, it is possible to prevent disturbances such as weather and adjust the amount of the adhering water or the permeated water evaporated by the heat of reaction of the free CaO. This is because moisture can be reduced. As shown in FIG. 1, the aged slag 10 is cut out by a shovel car 15, supplied to a crusher 16 such as a crusher via a conveyor such as a belt conveyor, and crushed to a size of 25 mm or less. . The crushed slag 10 is separated from the slag 1 by a magnetic separator 17 disposed in the middle of a conveying means such as a belt conveyor.
The iron particles having a particle size of 25 mm or less contained in the particle No. 0 are selectively removed, and the content of the iron particles is reduced to 10% by weight or less. Then, the slag 10 from which the granular iron has been removed is stored in the product storage site 18 as a raw material for cement clinker, and is transported to a subsequent process by a dump truck or the like as necessary.

[0011]

Next, an embodiment of a method for treating steelmaking slag for cement according to the present invention will be described. Dephosphorization in steel making process,
Desulfurization treatment is performed, and the main composition generated at that time is CaO4
0-60wt%, SiO ₂ 5 to 20 wt%, Al ₂ O ₃
4 to 15% by weight, 10 to 25% by weight of ferric oxide,
The slag in which a part of the CaO is free CaO is flowed to a processing yard, and after cooling by watering and sloping with a shovel car, a large ingot is removed and crushed to a size of 80 mm or less. Was adjusted to a water content of 12% by weight. This slag is 32m long and 3 width wide.
The slag was piled up in a 4 m building to a height of 5 m at maximum and left for 7 days to be dried by the heat generated by the hydration reaction of free CaO to reduce the water content of the slag to 7% by weight. Further, after drying, the slag was crushed to 25 mm or less by a crusher, and granular iron was adsorbed and removed using a magnetic separator to produce a slag having a content of granular iron of 10% by weight or less. As a result, the water content of the slag was low and stable, so that there was no trouble in crushing or magnetic separation, and the efficiency of removing granular iron by the magnetic separator was good. When this slag was used as a raw material for cement clinker, the quality of cement was good.

On the other hand, as a comparative example, a slag having a water content of 13% by weight was stacked outdoors under the same conditions as the slag described above, and the slag having a water content of 13% by weight under the influence of weather or the like was obtained. Was crushed to 25 mm or less by a crusher, and iron particles were adsorbed and removed using a magnetic separator. as a result,
Adhesion or accumulation of slag etc. is seen on the crusher, magnetic separator, conveyor belt conveyor, etc., the efficiency of removal of granular iron by the magnetic separator is poor, and the content of granular iron is as poor as 15% by weight. A trouble occurred and the quality of the raw material for cement clinker deteriorated.

The embodiments of the present invention have been described above.
The present invention is not limited to the above-described embodiment, and all changes in conditions that do not depart from the gist are within the scope of the present invention. For example, it is also possible to perform aging treatment by sieving a slag solidified by sprinkling water in a processing yard with a shovel car and then sieving the slag through a crusher. Furthermore, when loaded indoors, free CaO
Slag-containing water after drying by the heat of reaction
It is also possible to adjust the water content to 11 to 12% by weight, for example, by spraying water in advance so that the amount is equal to or less than the weight%.

[0014]

According to the method for treating steelmaking slag for cement according to claims 1 to 3, the slag generated in the dephosphorization and deflow processes of steelmaking is conveyed, the slag is discharged to a treatment yard, and water is sprinkled on the slag. After cooling and crushing a large lump of slag and removing the ingot, the slag is once stacked, and the slag is crushed after the moisture is reduced to 10% by weight or less by the reaction heat of CaO contained in the slag, Since the granular iron contained in the slag is sorted and removed, the water of the slag is stably reduced to a predetermined value by using the reaction heat of free CaO, and the adhesion of the slag in the crushing process and the magnetic separation process is reduced. Suppression of sedimentation, reduction of slag adhering to granular iron, and good selection efficiency of granular iron,
Resources can be recycled as raw materials for cement clinker. In addition, productivity of a production line such as crushing and sorting can be improved, and operations such as repair and removal of attached matter can be eliminated.

In particular, in the method for treating steelmaking slag for cement according to claim 2, since the slag is loaded indoors, the slag can be dried using the heat of hydration reaction of free CaO, and the water content can be reduced stably. The efficiency of crushing and sorting can be increased. Moreover, slag having high weathering and expansion properties can be recycled to cement clinker or the like, and resources can be reused.

In the method for treating steelmaking slag for cement according to the third aspect, since the granular iron is selectively removed by the magnetic separator, the granular iron in the slag can be reliably removed, and the crusher is prevented from being worn. However, it is possible to avoid problems such as expansion of the cement and generation of cracks, and to improve the quality of the cement clinker and the like.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of processing steps of a method for processing steelmaking slag for cement according to one embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the water content of raw ore slag and the content of granular iron in product slag.

FIG. 3 is a graph showing the relationship between the number of drying days and the water content of raw ore slag.

[Explanation of symbols]

10: slag, 11: waste truck, 12: waste pan, 13:
Processing yard, 14: indoor aging treatment plant, 15: excavator, 16: crusher, 17: magnetic separator, 18: product loading site

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayoshi Yokoo 1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka New Nippon Steel Corporation Yawata Works (72) Inventor Yasuhiro Yamazawa Yawata-Higashi-ku, Kitakyushu-shi, Fukuoka 27 in Kawabuchicho 9 Yatai Branch, Taihei Kogyo Co., Ltd. (72) Inventor Masato Kajiyama Inside 27 Yatai Branch, Taihei Kogyo Co., Ltd. 9-9 Kawabuchicho, Yawatahigashi-ku, Kitakyushu-shi, Fukuoka F-term (reference) 4G012 JD01 JD02 JE04 JE06 4K012 AB02 AB08

Claims (3)

[Claims] Claims 1. A slag generated in a dephosphorization and deflow process of steelmaking is conveyed, discharged to a treatment yard, sprinkled on the slag and cooled, and then a large lump of the slag is crushed to remove the metal. After the removal, the slag is temporarily piled up, the moisture is reduced to 10% by weight or less by the reaction heat of CaO contained in the slag, and then the slag is crushed, and the granular iron contained in the slag is selectively removed. A method for treating steelmaking slag for cement, comprising: 2. The method for treating steelmaking slag for cement according to claim 1, wherein said slag is loaded indoors. 3. The method for treating steel slag for cement according to claim 1 or 2, wherein the separation of the granular iron is performed by a magnetic separator.