Production method of slag foaming sedative, slag foaming sedative, and sedation method of slag foaming

Abstract

To provide a production method of a slag foaming sedative using tar sludge as the slag foaming sedative in a converter or a slag discharging place, to provide a slag foaming sedative, and to provide a sedation method of slag foaming.SOLUTION: A production method of a slag forming sedative includes: a mixing step of mixing tar sludge 10 and an alkaline component 12 to form a mixture 16; and a solidifying step of solidifying the mixture to form a solid 20. In the mixing step, the tar sludge, the alkali component, and a silica-alumina component may be mixed to form the mixture.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a slag foaming suppressant, a slag foaming suppressant, and a method for suppressing slag foaming. [Background technology]

[0002] When molten iron is refined in a refining vessel such as a converter, steelmaking slag (sometimes simply referred to as "slag" in this disclosure) is generated during the refining process. The generated slag is discharged from the converter into a slag ladle (also called a "slag pot" or "slag pan") and collected separately from the refined molten iron. During or after such molten iron refining, a phenomenon known as foaming occurs in the slag due to bubbles of CO (carbon monoxide) gas and other gases that are generated when carbon (C) in the molten iron reacts with iron oxide (FeO) in the slag at the interface between the molten iron and the slag. If this slag foaming (referred to as "slag foaming" or simply "foaming" in this disclosure) is severe, slag at 1300 to 1500°C may overflow from the refining equipment or transport vessel, damaging the refining equipment or transport vessel and requiring significant time and effort for recovery.

[0003] To calm slag foaming, it is necessary to destroy the layer where CO bubbles remain (the foam layer) and shrink the slag. A commonly known method for this purpose is to add a mass of material that gasifies inside the slag (called a "calming agent" or "calming material") to the slag, and use the volume expansion energy generated when the mass gasifies through thermal decomposition to destroy the foam layer. Solid organic materials such as waste plastics, paper sludge, molded food waste pellets, and wood are used as calming agents for calming slag foaming. It has also been proposed to use refractory waste powder, coal, limestone, iron powder, slag powder, etc. (see Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-302951 [Patent Document 2] Patent No. 6760248 [Patent Document 3] Japanese Patent Application Publication No. 9-310112 [Patent Document 4] Japanese Patent Publication No. 2022-109468 Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, the steelmaking process produces various by-products other than slag, and there is a desire to recycle the tar sludge generated in the upstream chemical process. Tar sludge is a mixture of tar as its main component and impurities such as coal powder and sludge. Tar is sometimes recycled into coke ovens as a binder, but the impurities in tar sludge deteriorate the quality of the coke. To reduce production costs, it is desirable to use inexpensive materials in coke production, but the proportion of inexpensive raw materials used decreases depending on the amount of tar sludge added, which increases the unit price of coke.

[0006] On the other hand, treating tar sludge as industrial waste requires disposal costs, and some steel mills have thousands of drums of untreated tar sludge on their premises due to a lack of processing capacity. Therefore, it is desirable to recycle tar sludge and use it for purposes other than the production of coke.

[0007] In view of the above-described problems, the present disclosure aims to provide a method for manufacturing a slag foaming suppressant that uses tar sludge as a slag foaming suppressant in a converter or a slag discharge site, a slag foaming suppressant, and a method for suppressing slag foaming. [Means for solving the problem]

[0008] The above problems can be solved by the following means. <1> a mixing step of mixing the tar sludge with an alkaline component to form a mixture; solidifying the mixture to form a solid; A method for producing a slag foaming calming agent, comprising: <2> In the mixing step, the tar sludge, the alkali component, and the silica-alumina component are mixed to form the mixture. <1> A method for producing the slag foaming sedative described in <3> Fly ash is used as the silica-alumina component. <2> A method for producing the slag foaming sedative described in <4> The alkaline component is made of collected dust. <1> ~ <3> A method for producing a slag foaming sedative according to any one of the above. <5> The mixing step and the solidification step are carried out using a continuous extrusion molding machine. <1> ~ <4> A method for producing a slag foaming sedative according to any one of the above. <6> the continuous extrusion molding machine is equipped with a temperature control mechanism and controls the temperatures of the mixing step and the solidification step; <5> A method for producing the slag foaming sedative described in <7> A slag foaming calming agent, which is a solid made by mixing and solidifying tar sludge, alkaline components, and silica-alumina components. <8> <1> ~ <6> A slag foaming sedative produced by the method for producing a slag foaming sedative according to any one of the above items, or <7> A method for calming slag foaming, comprising a step of adding the slag foaming calming agent according to claim 1 to slag foaming. [Effects of the Invention]

[0009] According to the present disclosure, there are provided a method for manufacturing a slag foaming suppressant that uses tar sludge as a slag foaming suppressant in a converter or a slag removal site, a slag foaming suppressant, and a method for suppressing slag foaming. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 2 is a diagram illustrating an example of a method for producing a slag foaming sedative according to the first embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating the mechanism by which tar sludge solidifies in the first embodiment. [Figure 3] FIG. 10 is a diagram illustrating an example of a method for producing a slag foaming sedative according to a second embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram illustrating the mechanism by which tar sludge solidifies in the second embodiment. [Figure 5] FIG. 1 is a schematic diagram showing an example of the configuration of a continuous extrusion molding machine used in a method for producing a slag foaming sedative according to the present disclosure. [Figure 6] FIG. 1 is a diagram showing the relationship between time and slag height when the slag foaming sedant produced in Example 1 is added to slag foaming. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment that is an example of the present disclosure will be described. In this disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. However, when the numerical values ​​written before and after "to" are followed by "greater than" or "less than," the numerical range does not include these numerical values ​​as the lower or upper limit. The content of a component may be expressed by adding "amount" to the element symbol (for example, C amount, Si amount, etc.). With respect to the content of a component, "%" means mass %. The term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0012] The inventors of the present disclosure have investigated the use of tar sludge as a foaming calming agent in converters and slag removal sites as a method for recycling and utilizing tar sludge as a resource. Tar sludge is generally a highly viscous liquid or a semi-solid that is fluid at room temperature, making it difficult to use as a foaming suppressant as it is. The reasons for this include the inability to physically destroy the foaming, the difficulty in reaching the interior of the foaming, which prevents the foam-breaking effect caused by gas generation from within, and poor handling, such as transport and loading into a converter.

[0013] Furthermore, the mechanism by which the sedative is effective is thought to be the physical destruction of the foam or the breakdown of bubbles due to gasification inside the foam, but if it is liquid or semi-solid, it will burn on the surface of the foam, which will not be effective enough, and there is also the risk of a steam explosion. Therefore, solidifying tar sludge is an important issue for using it as a sedative.

[0014] To address this issue, it is important to solidify liquid or semi-solid tar sludge. For example, the viscosity of tar sludge can be increased by drying it at high temperatures, but solidifying or briquetting it is difficult. Therefore, the inventors of the present disclosure conducted repeated experiments and studies and found that a solid substance can be obtained even at room temperature by mixing tar sludge with an alkaline component such as CaO and solidifying the mixture.

[0015] Furthermore, the inventors of the present disclosure have discovered that cement can be formed through a chemical reaction between collected dust containing alkaline components such as CaO and fly ash, which is primarily composed of silica and alumina, and that an even harder solid can be obtained by infiltrating tar sludge into the cement.

[0016] [Manufacturing method of slag foaming agent] Hereinafter, a first embodiment and a second embodiment of the method for producing a slag foaming suppressant according to the present disclosure will be described.

[0017] First Embodiment A method for producing a slag foaming quencher according to the first embodiment of the present disclosure includes: a mixing step of mixing the tar sludge with an alkaline component to form a mixture; and solidifying the mixture to form a solid. The method for producing a slag foaming agent according to the present disclosure may include other steps in addition to the mixing step and the solidification step. For example, a heating and drying step may be included as part of the solidification step or after the solidification step. The method may also include a step of cutting or pulverizing the resulting solid.

[0018] (tar sludge) Tar sludge is a by-product of chemical conversion flow during coke production, and is a mixture containing tar as the main component, coal powder, sludge from a water purification plant, etc. The component ratios of tar sludge are not universally determined, but examples include tar: 30-55%, sludge (coal powder): 20-30%, moisture: 10-18%, and others (sludge, etc.): 8-15%. The component ratios of the tar sludge used in the present disclosure are not particularly limited, and a by-product of chemical conversion flow during coke production can be used.

[0019] (Alkaline component) The alkaline component in the present disclosure refers to an oxide that reacts with water contained in tar sludge to produce an alkali metal or alkaline earth metal hydroxide, as well as an alkali metal or alkaline earth metal hydroxide. The alkaline component has the effect of solidifying the oil contained in tar sludge through a saponification reaction, etc., as described below. From the viewpoint of effective utilization of industrial waste, it is preferable to use collected dust, slag powder, etc., containing an alkaline component. Collected dust (alkali dust) is alkaline components such as CaO that are blown up from slag in a converter or steelmaking process and collected by a dust collector.

[0020] 1 shows an example of a method for producing a slag foaming quencher according to the first embodiment of the present disclosure. Tar sludge 10 and CaO dust 12 are mixed, and the container containing the mixture 16 is heated, if necessary, in a water bath 14 at about 80°C for 30 minutes to solidify the mixture.

[0021] FIG. 2 shows the mechanism by which tar sludge solidifies in the first embodiment. The manufacturing method for the slag foaming inhibitor according to the first embodiment applies a method in which oils and fats are stirred at high temperatures with an alkaline substance, washed with water, and the oil is dried to obtain solid soap from the liquid oil. When the oil contained in tar sludge is mixed with an alkaline component and stirred at high temperatures, it solidifies through a saponification reaction (FIG. 2(A)). In addition to the saponification reaction, some of the organic matter contained in tar sludge reacts with the alkaline component, replacing hydrogen with alkali, forming compounds with elevated melting points (FIGS. 2(B) and (C)), which facilitate solidification. It is believed that this mechanism is responsible for the solidification of tar sludge when mixed with an alkaline component and heated.

[0022] The mixing ratio (mass ratio) of tar sludge and alkaline component varies depending on the composition of the raw materials used, but for example, in the case of tar sludge and collected dust, the saponification value is 5 to 500.

[0023] Mixture 16 is heated in a hot water bath and solidified to form mixture 18. Although the mixture can be left to dry, it is preferable to accelerate the solidification by heating and drying. For example, as shown in Figure 1, solidification is accelerated by drying at 100°C for one day. This results in a solid product 20 from which volatile components such as water have been removed. The obtained solid material 20 may be packed in a bag for transportation and storage, may be easily added by hand or from a hopper as a slag foaming calming agent, and may be cut or crushed into a size of, for example, about 10 to 150 mm, taking into consideration physical destruction of the foaming and foam breaking due to gasification inside the foaming.

[0024] Second Embodiment The method for producing a slag foaming suppressant according to a second embodiment of the present disclosure further includes adding a silica-alumina component as a raw material. That is, the method for producing a slag foaming suppressant according to the second embodiment includes a mixing step of mixing tar sludge, an alkali component, and a silica-alumina component to form a mixture; and solidifying the mixture to form a solid. The method for producing a slag foaming sedative according to the second embodiment is an application of the pozzolanic reaction, and can produce a solid product with higher hardness than the method according to the first embodiment.

[0025] The tar sludge and the alkaline component used in the second embodiment are the same as those in the first embodiment, and therefore, description thereof will be omitted here.

[0026] (Silica and alumina components) The silica-alumina component in this disclosure is a material containing silica (SiO2) and alumina (Al2O3). Fly ash is a preferred silica-alumina component from the perspective of effectively utilizing industrial waste. Fly ash is ash primarily composed of silica (SiO2) and alumina (Al2O3) produced during coal combustion and can be obtained from energy plants such as thermal power plants and steel mills.

[0027] FIG. 3 shows an example of a method for producing a slag foaming quencher according to a second embodiment of the present disclosure. As shown in FIG. 3, for example, cement 22 is formed by mixing CaO dust and fly ash in a 1:1 (mass ratio). The formation of cement 22 provides a water absorption effect and reduces voids in the resulting solid. Then, a mixture 50 obtained by mixing tar sludge 10 and cement 22 at room temperature is left to solidify for, for example, six hours. Water may be added during mixing.

[0028] FIG. 4 illustrates the mechanism by which tar sludge solidifies in the second embodiment. When collected dust (CaO dust) 12 and fly ash 24 are mixed, fly ash particles are eluted in an alkaline atmosphere (FIG. 4(A)). The calcium hydroxide contained in the collected dust 12 reacts with the silica and alumina in the fly ash 24 to form hydrates such as nCaO·SiO2·mH2O (calcium silicate hydrate), 3CaO·Al2O3·6H2O (calcium aluminate hydrate), and 3CaO·Al2O3·3CaSO4·32H2O (ettringite), forming a polazon reaction layer 34 (FIG. 4(B)). The polazon reaction layer 34 then becomes a plate-like reaction layer 36, which tightly bonds and integrates with the pores (FIG. 4(C)).

[0029] In this way, tar sludge, alkali dust, and fly ash are mixed together as raw materials to solidify the mixture. While proper temperature control to promote chemical reactions and evaporation of volatile components increases production efficiency, solidification can also occur at room temperature. The mechanisms of solidification are as follows: (1) As shown in Figure 2, solidification occurs due to an increase in the melting point of organic substances with specific functional groups in the oil components contained in the tar sludge, as a result of a saponification reaction; (2) As shown in Figure 4, the silica and alumina in the alkali dust and fly ash are converted into cement through a pozzolanic reaction.

[0030] According to the method of the second embodiment, a solid (slag foaming quencher) containing a carbon component, silica, alumina, and quicklime is obtained. Furthermore, according to the method of the second embodiment, it is possible to produce a solid product with high strength, for example, a crushing strength of 20 kg to 2000 kg, without carrying out heat drying after the solidification step.

[0031] In the second embodiment, the order in which the tar sludge, alkali component, and silica-alumina component are mixed is not particularly limited, and these three components may be mixed simultaneously, or two components may be mixed and then the remaining component may be mixed. From the perspective of effectively utilizing the cementification of the alkali component and silica-alumina component through the pozzolanic reaction, it is preferable to mix the alkali component and silica-alumina component to produce cement and then mix the tar sludge, as shown in Figure 3.

[0032] The mixing ratio (mass ratio) of tar sludge, alkali component, and silica-alumina component varies depending on the composition of the raw materials used, but for example, in the case of tar sludge, collected dust, and fly ash, it is 1:10:10 to 10:1:1. The tar sludge is preferably in the range of 1 / 20 to 5 times the weight of the mixture of collected dust and fly ash.

[0033] The means for mixing and solidifying the raw materials is not limited in the first and second embodiments. Temperatures may be adjusted in the mixing step and the solidification step to promote the reaction and phase change of the raw material components.

[0034] Figure 5 shows a schematic diagram of an example of the configuration of a continuous extruder used in the manufacturing method of the slag foaming agent according to the present disclosure. The continuous extruder 100 includes a kneading section 110 for mixing the raw materials, an extrusion section 120 equipped with a screw for extruding the solid material, and a temperature control mechanism. The continuous extruder 100 with this configuration accelerates the chemical reaction by using high temperatures during kneading, and controls the pressure during molding, making it possible to control the density and crushing strength of the resulting solid material.

[0035] Raw materials such as tar sludge fed into a hopper 112 are kneaded in a kneading section 110. Then, the raw materials are fed into an extrusion section 120 to promote solidification, and the solid material is continuously extruded from an extrusion port 122. By continuously carrying out the mixing process and the solidification process using a continuous extrusion molding machine 100 equipped with a temperature control mechanism, it is possible to uniformly knead the raw materials, and the temperature control mechanism can control the chemical reaction and drying. In addition, the strength of the product (solid material) can be increased by reducing voids during extrusion molding. The reaction rate and drying rate may be controlled by appropriately applying heat to the mixture before extrusion and the product (solid) after extrusion.

[0036] [How to calm slag foaming] The slag foaming stabilization method according to the present disclosure includes a step of introducing a slag foaming stabilization agent manufactured by the above-described method for manufacturing a slag foaming stabilization agent according to the present disclosure into slag foaming. The slag foaming quencher according to the present disclosure may be added, for example, from a hopper to the foamed slag in a converter, or may be added manually to the foamed slag discharged from the converter or the like into a slag pot. Since the slag foaming suppressant according to the present disclosure is a solid, it is easy to handle in any case, such as transportation, storage, and addition, and can effectively suppress foaming by adding it to the slag.

[0037] Furthermore, according to the present disclosure, the tar sludge produced in the production of coke can be treated in a coke oven without the need to use it, thereby reducing the unit price of coke by increasing the proportion of inexpensive materials, and by also utilizing collected dust, alkaline slag powder, and fly ash, it is possible to obtain the benefit of reducing industrial waste disposal costs. [Example]

[0038] Examples of the steel sheet according to the present disclosure will be described below. Note that the following examples do not limit the manufacturing method of the slag foaming suppressant and the slag foaming suppression method according to the present disclosure.

[0039] [Example 1] <Production of slag foaming sedative A> Equal weights of collected dust and fly ash (5g each) were prepared and kneaded in powder form. At this time, 10wt% of the powder mixture was added with water and kneaded. After mixing for a few minutes, the powder changed to a viscous state. After that, the entire amount of tar sludge (10g) was added and kneaded. The mixture was then formed into a block and stored. It was left to stand at 25°C and solidified within 24 hours.

[0040] <Evaluation> Slag (200 g) was heated in a tammann furnace with an inner diameter of 47 mm and a height of 200 mm and melted at 1350°C. After melting, pig iron pieces (1 g) measuring 2–5 mm in size were added to the tammann furnace. Foaming was induced by maintaining the furnace temperature at 1350°C. The foaming height was measured by inserting an alumina-coated stainless steel rod and measuring its adhesion depth. The foaming height peaked after approximately 1 minute and 30 seconds. Immediately after the peak, the slag foaming suppressant A (0.5 g) prepared above was added, and the suppression effect was quantitatively evaluated based on the change in foaming height. After suppression, the height decreased to approximately 1 / 5 of its peak height. Figure 6 shows the relationship between time and slag height when the slag foaming suppressant prepared in Example 1 was added to the slag foaming furnace. On the horizontal axis (time) in Figure 6, A indicates the time when foaming occurred, and B indicates the time when the suppressant was added.

[0041] [Example 2] <Production of slag foaming sedative B> Equal weights of collected dust and tar sludge (10g each) were prepared and mixed. They were heated to 80°C in a hot water bath. After mixing for a few minutes, the mixture changed from powder to clay. It was then left to stand in a drying oven at 110°C or higher for 12 hours or more to evaporate the volatiles. It was then formed into a block and stored. It was left to stand at 25°C and solidified within 24 hours.

[0042] <Evaluation> Slag (200g) was heated in a tammann furnace with an inner diameter of 47mm and a height of 200mm and melted at 1350°C. After melting, 2-5mm pig iron pieces (1g) were added to the tammann furnace. Foaming was induced by maintaining the furnace temperature at 1350°C. The foaming height was measured by inserting an alumina-coated stainless steel rod or similar and measuring the adhesion depth. The foaming height peaked after about 1 minute 30 seconds, and immediately after the peak, slag foaming stabiliser B (0.5g) manufactured above was added, and the stabilising effect was quantitatively evaluated from the change in foaming height. After settling, the height dropped to about 1 / 5 of its peak height. [Explanation of symbols]

[0043] 10. Tar sludge 12 Collected dust (CaO dust) 16 mixture 18 mixture 20 solids 22 Dust collection 24 Fly ash 34 Poroshenko reaction layer 36 Plate-shaped reaction layer 100 Continuous Extrusion Molding Machine 110 Mixing section 112 Hopper 120 Extrusion section 122 Extrusion port

Claims

1. a mixing step of mixing the tar sludge with an alkaline component to form a mixture; solidifying the mixture to form a solid; A method for producing a slag foaming calming agent, comprising:

2. 2. The method for producing a slag foaming suppressant according to claim 1, wherein in the mixing step, the tar sludge, the alkali component, and the silica-alumina component are mixed to form the mixture.

3. 3. The method for producing a slag foaming inhibitor according to claim 2, wherein fly ash is used as the silica-alumina component.

4. The method for producing a slag foaming calming agent according to any one of claims 1 to 3, wherein collected dust is used as the alkaline component.

5. The method for producing a slag foaming calming agent according to claim 1 or 2, wherein the mixing step and the solidifying step are performed using a continuous extrusion molding machine.

6. The method for producing a slag foaming agent according to claim 5, wherein the continuous extrusion molding machine is provided with a temperature control mechanism and controls the temperatures of the mixing step and the solidification step.

7. A slag foaming calming agent, which is a solid made by mixing and solidifying tar sludge, alkaline components, and silica-alumina components.

8. A method for slag foaming comprising a step of adding a slag foaming sedative manufactured by the method for manufacturing a slag foaming sedative according to claim 1 or claim 2, or the slag foaming sedative according to claim 7, to slag foaming.

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