JP4403055B2 - Steelmaking slag treatment method - Google Patents

Description

  The present invention relates to a method for processing steelmaking slag, and more particularly, to a method for processing steelmaking slag to obtain a dense high-quality steelmaking slag by reducing bubbles contained in the steelmaking slag.

  Conventionally, various reforming treatments have been applied to steelmaking slag in order to improve the quality of the steelmaking slag and increase the commercial value.

  For example, Patent Document 1 discloses a slag that mixes a steel-containing slag with a silicic acid-containing modifier, a carbon-containing reducing agent, and iron scrap, and melts the mixture while supplying an oxygen-containing gas and maintaining a reducing atmosphere. A hot reforming method is disclosed. By this method, free CaO (hereinafter referred to as f. CaO), phosphorus oxide, and valuable metal oxides in the steelmaking slag are reduced, so that recycling can be achieved.

  Further, Patent Document 2 discloses that the amount of CaO as an insertion auxiliary raw material when refining steelmaking slag is 50 kg / crude steel ton or less and slag basicity is 3.5 or less and is allowed to cool and solidify, and then the slag temperature is 400. Disclosed is a method for stabilizing steelmaking slag in which sensible heat at ˜1,000 ° C. is maintained and charged into a hot water bath at 40 ° C. to 100 ° C. to promote the hydration reaction of f · CaO and stabilize. Has been. By such a method, expansion and powdering of the steelmaking slag can be reduced.

  In addition, if the molten slag is solidified in a foamed state, bubbles will be contained in the slag, resulting in quality degradation. Patent Document 3 discloses a steelmaking slag treatment method that suppresses foaming of molten slag by spraying mist-like water onto the molten slag in the waste pan.

JP-A-6-115984 JP-A-6-183792 Japanese Patent Laid-Open No. 5-195040

  However, in the method described in Patent Document 1, since iron scrap is added, the mixture must be melted by heating to a temperature of 1,550 ° C. or higher, which requires a large amount of heat and time. There's a problem. Further, since the steelmaking slag is treated in a reducing atmosphere, the metal oxide is reduced, so that the metal oxide with which f · CaO reacts is reduced, so that CaO remains in the modified slag. is there.

  In addition, the method described in Patent Document 2 has a problem that the processing capacity is inferior because it takes a long time (for example, about several days) to stabilize the steelmaking slag. Furthermore, the method described in Patent Document 2 has a problem that the steelmaking slag cannot be reformed until it can be used for the upper roadbed material, and even if it is modified, the water absorption rate is high and the strength is insufficient.

  Moreover, the method for suppressing foaming of slag described in Patent Document 3 is for safely transporting molten slag in a waste pan to a disposal spot, and does not relate to improving the quality of slag. For this reason, since water is sprinkled on the molten slag in which bubbles remain and is rapidly cooled, there is a problem that a large number of bubbles are contained in the slag.

  As described above, each of the above prior art documents describes various methods for reforming steelmaking slag, but does not describe how to improve the quality by reducing bubbles in the steelmaking slag.

  When defoaming such steelmaking slag bubbles, simply evacuating the steelmaking slag containing bubbles from the slag pan to the iron container contains bubbles regardless of whether or not the water is sprayed and quenched. It solidifies in this state and becomes low quality (high water absorption). If bubbles in such steelmaking slag are defoamed using a separate means such as a reforming material or a heating means, the cost becomes high. On the other hand, if it can be reduced without using a separate means such as a reforming material or a heating means, a high quality slag can be obtained at low cost.

  Accordingly, an object of the present invention is to provide a new and improved steelmaking slag treatment method capable of defoaming bubbles in a molten steelmaking slag by a simple and easy method to obtain a high quality steelmaking slag. There is to do.

In order to solve the above-mentioned problems, in a first aspect of the present invention, a hot metal pretreatment slag is used as a molten steelmaking slag , and the method starts to drop from a position having a height difference of 2 m or more and solidifies. A method for treating steelmaking slag is provided, wherein after defoaming due to a drop impact, the temperature is equal to or lower than the liquidus temperature of the slag.

In the invention described above, a steelmaking slag containing bubbles (for example, an apparent bulk specific gravity of less than 1) (ie, a forming slag) is impacted on the slag simply by utilizing the slag fall energy due to gravity. The bubble breakage of the slag can be promoted. As a result, the bubbles in the solidified steelmaking slag are remarkably reduced, and the water absorption rate of the steelmaking slag is, for example, 4% by mass (hereinafter referred to simply as “%”) and the true specific gravity is 2-4 g / A dense slag lump of cm ³ can be obtained. In this way, steelmaking slag can be defoamed in a simple and easy manner without using additional means such as a reforming material and heating means. For example, high-quality slag that can be applied as an upper roadbed material is reduced. Can be manufactured at cost.

  It is preferable that the steelmaking slag always falls while maintaining a drop height difference of 2 m or more. As a result, even when the remaining molten slag falls on the already solidified slag lump (when the drop height difference of the steelmaking slag becomes low), the drop energy for defoaming bubbles is reduced to the end. It can be secured sufficiently. Further, the drop height difference of the steelmaking slag is preferably 3 m or more, and more preferably 4 m or more. That is, as the drop height difference of the steelmaking slag increases, the water absorption rate of the solidified steelmaking slag decreases (for example, the water absorption rate is about 3% at 3 m and about 2% at 4 m), and a higher quality slag can be obtained. it can. However, the drop height difference of steelmaking slag is not more than 5m because of the problems of cranes and other equipment. The slag is scattered and the yield is reduced, and the steelmaking slag absorption rate is further improved. Is not preferable because it is not expected.

Further, if the basicity of the steelmaking slag is in the range of 0.6 ≦ CaO / SiO ₂ ≦ 2.0, a low basicity slag that is difficult to degas is used as the target slag. The defoaming effect is significantly improved as compared with the prior art. The reason why the lower limit of the basicity of steelmaking slag is 0.6 is that it is the lower limit in normal actual operation. The basicity of slag is the mass ratio of CaO and SiO _{2 in} the slag (CaO / SiO ₂ ).

  Moreover, if it comprises so that the content of granular iron in the said steelmaking slag is 15 mass% or less, it can suppress that a steelmaking slag falls and defoaming a bubble after degassing. That is, if steelmaking slag containing iron oxide contains a certain amount or more of granular iron (metallic iron), oxygen in the iron oxide reacts with carbon in the granular iron to generate CO bubbles. It becomes easy to do. For this reason, in order to maintain the slag quality after solidification, the content of granular iron in the steelmaking slag is preferably 15% by mass or less. The lower limit of the granular iron content is not particularly specified, but is usually about 2 to 3%.

  Moreover, if the average cooling rate until it reaches 800 degreeC from the temperature (for example, 1,200-1,400 degreeC) at the time of the fall start of the said steelmaking slag is 20 degree-C / min or more, steelmaking will be carried out. Air bubbles in the slag can be suitably removed. That is, in order to prevent re-foaming of steel slag, after defoaming due to the impact of dropping, the temperature of the steel slag should be lower than its liquidus temperature (for example, about 1,100 ° C to 1,200 ° C). Is preferred. In this respect, re-foaming of the steelmaking slag is prevented by processing the steelmaking slag under the condition that the average cooling rate from the temperature at which the steelmaking slag starts to fall to 800 ° C is 20 ° C / min or more. It has been found that

  Steelmaking slag is degassed in a simple and easy way without using additional means such as a modifier and heating means. For example, high-quality slag that can be used as an upper roadbed material is manufactured at low cost. be able to.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  First, based on FIG. 1, the processing method of the steelmaking slag concerning this embodiment is demonstrated. In addition, FIG. 1 is explanatory drawing for demonstrating the flow of the processing method of the steelmaking slag concerning this embodiment.

First, as shown in FIG. 1A, molten steelmaking slag (in this embodiment , hot metal pretreatment slag) 100 after hot metal pretreatment is discharged from a converter 200 to a ladle 300. That is, the steelmaking slag in the present embodiment is a hot metal pretreatment slag after hot metal pretreatment in a refining process in which blast furnace hot metal is charged into a converter and hot metal pretreatment is performed followed by decarburization blowing. Yes, Table 1 shows an example of the composition.

但し，Ｍ−Ｆｅ（メタリック鉄）は，外数である。また，スラグ成分は，ＭｎＯ，Ｐ，Ｓなど工程によって不可避的に含まれる成分は除外している。また，Ｍ−Ｆｅの値は，採取したスラグを粉砕し磁石に付着したものの質量（ｍａｓｓ）％である。

However, M-Fe (metallic iron) is an outside number. The slag component excludes components inevitably included in the process such as MnO, P, and S. Further, the value of M-Fe is the mass% of the slag collected and adhered to the magnet.

As shown in Table 1, the basicity of the steelmaking slag according to this embodiment is preferably in the range of 0.6 ≦ CaO / SiO ₂ ≦ 2.0. When the steelmaking slag 100 has a low basicity (for example, a range of 0.6 ≦ CaO / SiO ₂ ≦ 2.0), bubbles in the steelmaking slag are difficult to escape. It is particularly useful because it increases the effect. The reason why the lower limit of the basicity of steelmaking slag is 0.6 is that it is the lower limit in normal actual operation.

  Moreover, as shown in Table 1, the content of granular iron (M-Fe) in the steelmaking slag according to the present embodiment is preferably 15% by mass or less. When the content of the granular iron in the steelmaking slag is 15% or less, after the steelmaking slag is dropped and defoamed in the steelmaking slag treatment method described later, bubbles are suppressed from being refoamed. That is, if steelmaking slag containing iron oxide contains a certain amount or more of granular iron (metallic iron), oxygen in the iron oxide reacts with carbon in the granular iron to generate CO bubbles. It becomes easy to do. For this reason, in order to maintain the slag quality after solidification, the content of granular iron in the steelmaking slag is preferably 15% by mass or less.

  Next, as shown in FIG. 1 (b), the slag pan 300 in which the discharged steelmaking slag 100 is accommodated is placed on a transport vehicle 400 and transported to a slag treatment plant.

  Finally, as a steelmaking slag processing method according to the present embodiment, as shown in FIG. 1 (c), for example, a waste pan 300 in which a steelmaking slag 100 of 1,305 ° C. is accommodated has at least a drop height difference H. The crane is lifted up to a height of 2 m or more, and the slag pan 300 is tilted while maintaining the height, and a slag cooling container 500 (for example, an alumina-based amorphous refractory with a thickness of 10 cm is placed inside the iron skin. Pour into the construction).

  Conventionally, the purpose was only to transfer the steelmaking slag 100 from the slag ladle 300 to the slag cooling vessel 500. Therefore, the slagpan 300 in which the steelmaking slag 100 is accommodated is the minimum at which the steelmaking slag 100 can be injected. The steelmaking slag 100 was poured into the slag cooling vessel 500. For this reason, the air bubbles in the steelmaking slag 100 are not removed, and a large number of air bubbles are present in the solidified slag, which causes a reduction in the quality of the slag.

In the present embodiment, unlike the prior art, when the steelmaking slag 100 is poured into the slag cooling vessel 500, it is a method of starting the drop from a position having a height difference of 2 m or more and solidifying it. After defoaming by, a method is adopted in which the liquidus temperature is lower than the slag . According to such a method, steel slag containing bubbles (for example, apparent bulk specific gravity of less than 1) is impacted on the slag simply by using the slag fall energy due to gravity. The bubble breakage of the slag can be promoted.

  The relationship between the drop height difference of the steel slag and the water absorption rate of the solidified slag lump will be described with reference to FIG. FIG. 2 is a graph showing the relationship between the steelmaking slag injection height and the water absorption rate of the solidified slag according to this embodiment. The graph shown in FIG. 2 shows that the pouring height H of the slagging ladle 300 containing the steelmaking slag (temperature of 1,305 ° C.) 100 having the composition shown in Table 1 above is suspended by a crane. The water absorption rate of each slag solidified in the slag cooling container after being poured into the slag cooling container 500 was investigated. Here, “injection height” is the drop height difference at the start of steelmaking slag injection. The slag that has fallen into the slag cooling container stays in the container and solidifies, so the height of the bottom of the container gradually increases. However, the height of the slag that has cooled and solidified in the container is increased. The height is usually about 30 cm at the highest. For this reason, the drop height difference of the slag that has fallen later is slightly smaller than the drop height difference of the slag at the start of pouring, but the effect of the present invention can be achieved as long as it is within this range. .

  As shown in Fig. 2, it is understood that the water absorption rate of steelmaking slag decreases exponentially as the drop height difference of steelmaking slag increases. This is because the potential energy of the steelmaking slag increases as the drop height difference of the steelmaking slag increases, and the falling speed of the steelmaking slag and its impact level when injected into the slag cooling vessel increase. It is thought that the effect is enhanced.

  In addition, as a high-grade application of steelmaking slag, it is generally required that the water absorption is 4% or less. Thus, in order to make the water absorption rate of the solidified slag 4% or less, referring to FIG. 2, it is recognized that the drop height difference H of the steelmaking slag should be 2 m or more. Such low-absorption slag can be used for high-grade applications such as upper roadbed materials and concrete aggregates.

In addition, in the range of 0.6 ≦ CaO / SiO ₂ ≦ 2.0, the basicity of the steelmaking slag decreases exponentially as the drop height difference of the steelmaking slag increases, similarly to the result shown in FIG. It has been confirmed that the water absorption rate is 4% or less if the drop height difference H of steelmaking slag is 2 m or more.

  In addition, the molten steelmaking slag is always 2 m or more, for example, by setting a sufficient height in consideration of the height of the solidified slag lump or by gradually lifting the waste pan with a crane. It is preferable to drop so as to maintain the height difference. As a result, even when the remaining steelmaking slag falls on the already solidified slag lump (when the drop height difference of the steelmaking slag becomes low), the drop energy for defoaming bubbles is reduced to the end. It can be secured sufficiently. Further, the drop height difference of the steelmaking slag is preferably 3 m or more, and more preferably 4 m or more. That is, the higher the drop height difference, the lower the water absorption rate of the steelmaking slag (for example, the water absorption rate is about 3% at 3 m and about 2% at 4 m), and a higher quality slag can be obtained. However, it is not realistic to set the drop height difference of molten slag to 5 m or more because of problems with equipment such as cranes. The slag is scattered and the yield is reduced, and the steel slag absorption rate is further improved. Is not preferable because it is not expected.

  Further, the cooling rate of the steelmaking slag is 20 ° C / min or more as the average cooling rate until the temperature reaches 800 ° C from the temperature at which the steelmaking slag starts to fall (eg, 1,200 ° C to 1,400 ° C). It is known that re-foaming of steelmaking slag can be prevented by processing steelmaking slag under conditions. That is, in order to prevent re-foaming of steelmaking slag, the temperature of steelmaking slag must be below its liquidus temperature (for example, about 1,100 ° C to 1,200 ° C) after defoaming due to a drop impact. I must. By satisfy | filling such conditions, the bubble in steelmaking slag can be defoamed suitably.

  The liquidus temperature of the steelmaking slag is, for example, iron and steel Vol. 88 (2002) NO2 p51 to 58, it is possible to calculate the melting temperature (liquidus temperature) from the slag composition using commercially available calculation software such as FactStage. Similarly, for example, a platinum foil (not shown) is placed on a refractory support (not shown), and 2 to 3 g of slag (not shown) is finely pulverized, and the diameter is reduced by a press. After forming into a 1 cm cylindrical shape, the temperature is raised at a constant rate of temperature rise, and the temperature at the time when the droplet height becomes ½ can also be measured.

In this embodiment, a steelmaking slag containing bubbles (for example, an apparent bulk specific gravity of less than 1) (ie, forming slag) is impacted on the slag simply by using the falling energy of the slag due to gravity. The bubble breakage of the slag can be promoted. As a result, bubbles in the solidified steelmaking slag are remarkably reduced, and a dense slag lump having a true specific gravity of 2 to 4 g / cm ³ can be obtained. In this way, steelmaking slag can be defoamed in a simple and easy manner without using additional means such as a reforming material and heating means. For example, high-quality slag that can be applied as an upper roadbed material is reduced. Can be manufactured at cost.

  Next, steelmaking slag was processed based on the above embodiment, and the water absorption rate of the solidified steelmaking slag was evaluated, and will be specifically described below.

(Implementation method)
First, the blast furnace hot metal is charged into a 350-ton converter, oxygen blown, and hot metal pretreatment is performed. (10 tons), and discharged to a discharge slag pot 35m ³ volume.

  Next, the waste pan was transported to the slag treatment plant.

  After that, the waste pan is lifted to a height of 3m with a crane, and the waste pan is tilted with the height maintained, and the hot metal pretreatment slag (5 tons) is dropped and the slag cooling container (3m X 3 m x 1 m: Alumina-based amorphous refractory with a thickness of 10 cm was poured inside the iron skin. Further, the injected slag was allowed to stand in a slag cooling container for 10 minutes, and after the slag solidified, water was sprayed on the upper surface and cooled.

  At this time, the hot metal pretreatment slag in this example had the composition shown in Table 2, and the slag temperature was 1320 ° C.

但し，Ｍ−Ｆｅ（メタリック鉄）は，外数である。また，スラグ成分は，ＭｎＯ，Ｐ，Ｓなど工程によって不可避的に含まれる成分は除外している。また，Ｍ−Ｆｅの値は，採取したスラグを粉砕し磁石に付着したものの質量（ｍａｓｓ）％である。

However, M-Fe (metallic iron) is an outside number. The slag component excludes components inevitably included in the process such as MnO, P, and S. Further, the value of M-Fe is the mass% of the slag collected and adhered to the magnet.

(result)
The water absorption rate of the slag obtained by the above example was investigated. The water absorption rate was measured using a test method defined in JIS A1109 or A1110. As a result, the water absorption rate of the slag obtained by the above example was 1.2%, and a low water absorption quality applicable as an upper roadbed material or the like could be obtained.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

  For example, in the said Example, although the structure which dropped the steelmaking slag from the height of 3 m was mentioned as an example, it demonstrated, It is not limited to this example. If the drop height difference of the steelmaking slag is 2 m or more, it can be appropriately set according to the desired quality such as the slag composition, the molten slag temperature, the liquidus temperature of the slag, the water absorption rate, and the like.

  The present invention can be applied to a steelmaking slag treatment method, and in particular, can be applied to a steelmaking slag treatment method for reducing bubbles in the steelmaking slag.

It is explanatory drawing for demonstrating the process of the processing method of the steelmaking slag concerning 1st Embodiment. It is a graph which shows the relationship between the injection height of the steelmaking slag concerning 1st Embodiment, and the water absorption rate of the solidified slag.

Explanation of symbols

100 Steelmaking slag 200 Converter 300 Waste pan 400 Transport vehicle 500 Slag cooling vessel

Claims (4)

This is a method of using a hot metal pretreatment slag as a molten steelmaking slag and starting to solidify by dropping from a position having a height difference of 2 m or more, and after degassing due to the impact of the drop, the liquidus of the slag The processing method of the steelmaking slag characterized by setting it as temperature or less . The basicity of the steel slag, the process method of the steel slag according to claim 1, wherein the _{0.6 ≦ CaO / SiO 2 ≦ 2.0} , the range near Turkey. Granulated metallic iron content of the steel slag, the process method of the steel slag according to claim 1 or 2, characterized in the Der Turkey 15 wt% or less. The average cooling rate from the temperature at the start falling steel slag until reaching 800 ° C., the steel according to any one of claims 1 to 3, wherein the der 20 ° C. / min or more Turkey Slag processing method.

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