Method for manufacturing a slug-forming sedative and method for sedating with slug-forming.

Abstract

The present invention provides a method for producing a slag forming sedative that utilizes at least one of tar sludge and sludge as a slag forming sedative in converters and slag discharge areas, and a method for sedating slag forming. [Solution] A method for producing a slag forming sedative, comprising a heavy-forming step of heating and drying liquid waste containing at least one of tar sludge and sludge in a low-oxygen atmosphere to increase its weight, and a method for slag forming, comprising a sedation step of adding the produced slag forming sedative to the slag forming to sedate the forming.

Description

Technical Field

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[0004]

[0001] The present disclosure relates to a method for producing a slag-forming suppressant and a method for suppressing slag-forming.

Background Art

[0002] When refining molten iron in a refining vessel such as a converter, steelmaking slag (which may be simply referred to as "slag" in the present disclosure) is generated during the refining process. The generated slag is discharged from the converter into a slag pot (also called a "slag pot" or "slag pan") separately from the molten iron that has undergone the refining process and is recovered. During or after such a refining process of molten iron, a phenomenon (forming) occurs in which slag foams due to bubbles such as CO (carbon monoxide) gas generated by the reaction of C (carbon) in the molten iron and FeO (iron oxide) in the slag at the interface between the molten iron and the slag. If such slag forming (referred to as "slag forming" or simply "forming" in the present disclosure) is intense, slag at 1300 to 1500 °C may overflow from the refining equipment or the transport container, and it will require a great deal of time and labor to recover if the refining equipment or transport container is damaged.

[0003] In order to suppress slag forming, it is necessary to break the layer (foam layer) where CO bubbles stay and shrink the slag. Therefore, a method is generally known in which a lump (referred to as a "suppressant" or "suppressing material") that gasifies inside the slag is put into the slag, and the foam layer is broken using the volume expansion energy when the lump gasifies by thermal decomposition. As a suppressant for suppressing slag forming, solid organic substances such as waste plastics, paper sludge, garbage molded pellets, and wood are used, and it has also been proposed to use refractory waste powder, coal, limestone, iron powder, slag powder, etc. (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-310112 [Patent Document 2] Japanese Patent Application Publication No. 59-213790 [Patent Document 3] Japanese Patent Publication No. 53-60373 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the steelmaking process, various by-products are generated in addition to slag. For example, liquid waste, including tar sludge and sludge, is produced in the upstream chemical flow (see, for example, Patent Documents 2-3). Disposal costs are incurred to treat tar sludge and sludge as industrial waste. Therefore, it is desirable to recycle liquid waste, including tar sludge and sludge, and reuse it for purposes other than coke production.

[0006] In view of the above-mentioned issues, this disclosure aims to provide a method for producing a slag forming sedative using liquid waste containing at least one of tar sludge and sludge as a slag forming sedative, and a method for sedating slag forming. [Means for solving the problem]

[0007] The above problems will be solved by the following means. <1> A method for producing a slag-forming sedative, comprising a heavy-forming step in which liquid waste containing at least one of tar sludge and sludge is heated and dried in a low-oxygen atmosphere to increase its weight. <2> The heavy-conditioning process involves heating the liquid waste to a temperature above the temperature at which the liquid components contained in the liquid waste volatilize. <1> A method for producing the slag-forming sedative described above. <3> The aforementioned heavy-forming process involves heating at a temperature of 120°C or higher and 250°C or lower. <1> or <2> A method for producing the slag-forming sedative described above. <4> The aforementioned weighting process involves weighting the liquid waste to an amount of solids of 80% by mass or more. <1> ~ <3> A method for producing a slag-forming sedative as described in any one of the following. <5> The proportion of tar in the aforementioned liquid waste is 30% by mass or more. <1> ~ <4> A method for producing a slag-forming sedative as described in any one of the following. <6> The proportion of the sludge in the liquid waste is 8% by mass or more and 30% by mass or less. <1> ~ <5> A method for producing a slag-forming sedative as described in any one of the following. <7> The aforementioned heavy-conditioning process involves heating the liquid waste using waste heat from the steelworks, <1> ~ <6> A method for producing a slag-forming sedative as described in any one of the following. <8> The aforementioned <1> ~ <7> A method for calming slag forming, comprising a calming step of adding a slag forming sedative, manufactured by any one of the methods for manufacturing a slag forming sedative described in one of the above, to the slag forming to calm the forming. [Effects of the Invention]

[0008] This disclosure provides a method for producing a slag forming sedative and a method for sedating slag forming, utilizing liquid waste containing at least one of tar sludge and sludge as a slag forming sedative in converters and slag discharge sites. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing one embodiment of the method for producing the slug-forming sedative according to the present disclosure. [Figure 2] Figure 2 shows an example of the mechanism by which tar sludge and sludge become heavier in the presence of alkaline components. [Figure 3] Figure 3 shows an example of the mechanism by which tar sludge and sludge become heavier in the presence of silica and alumina components. [Figure 4] Figure 4 is a schematic diagram showing an example of the configuration of a continuous extrusion molding machine. [Figure 5] Figure 5 shows the relationship between time and slag height when the slag forming sedative manufactured in Example 1 is added to the slag forming process. [Modes for carrying out the invention]

[0010] An example of an embodiment of this disclosure will be described. In this disclosure, a numerical range represented by "~" means a range that includes the numbers before and after "~" as the lower and upper limits. However, if the numbers before and after "~" are preceded by "greater than" or "less than", the numerical range means a range that does not include those numbers as the lower or upper limit. Regarding the content of ingredients, "%" refers to mass percentage. The term "process" includes not only independent processes, but also any process that cannot be clearly distinguished from other processes, as long as its intended purpose is achieved.

[0011] <Method for manufacturing slag-forming sedatives> The method for producing a slag-forming sedative includes a heavy-forming step in which liquid waste containing at least one of tar sludge and sludge is heated and dried in a low-oxygen atmosphere to increase its weight.

[0012] Traditionally, tar sludge and sludge have been considered unsuitable for use as foaming sedatives. This is because, being in liquid or semi-solid form, tar sludge and sludge tend to burn on the surface of the foam before they can be sedated, making it difficult to achieve a sufficient sedative effect. Furthermore, they have poor handling characteristics, such as difficulty in transporting and loading into converters, and there are concerns about steam explosions.

[0013] As a result of the inventors' intensive studies of the present disclosure, by using the method for producing a slag-forming tranquilizer having the above configuration, it has been found that a solid can be obtained by densifying a liquid waste containing at least one of tar sludge and sludge, which has been difficult to heat-dry conventionally. Furthermore, it has been found that the obtained solid can be used as a slag-forming tranquilizer.

[0014] [Densification step] In the densification step, a liquid waste containing at least one of tar sludge and sludge is heated and dried in a low-oxygen atmosphere to be densified. In the present disclosure, "densification" means making the liquid waste into a solid form by reducing the liquid component contained in the liquid waste and increasing the solid content concentration.

[0015] The liquid waste used in the method for producing a slag-forming tranquilizer according to the present disclosure contains at least one of tar sludge and sludge.

[0016] (Tar sludge) In the present specification, tar sludge is a by-product by-produced in the chemical conversion process (for example, a by-product when producing coke), and refers to a mixture mainly composed of tar and containing coal powder, sludge in a purification tank, and the like.

[0017] The proportion of tar in the liquid waste is preferably, for example, 30% by mass or more. When the proportion of tar is at or above the lower limit value, solids are more efficiently and with better yield formed in the densification step.

[0018] The mass ratio of each component in the total tar sludge is not particularly limited, and the mass ratio of each component in the tar sludge by-produced during the production of coke can be applied. Examples of tar sludge include those in which the mass ratio of various components in the total tar sludge is in the range of tar: 30% to 55% by mass, sludge (coal powder): 20% to 30% by mass, moisture: 10% to 20% by mass, and other components (sludge, etc.): 0% or 1% to 15% by mass.

[0019] (Sludge) In this specification, the term "sludge" is a concept that includes both organic sludge and inorganic sludge. Sludge is a muddy, precipitated waste generated during the wastewater treatment process that contains at least one of inorganic and organic components.

[0020] The proportion of sludge in the liquid waste may be 0% by mass, 1% to 70% by mass, or 8% to 30% by mass. When the proportion of sludge is above the lower limit, solid material is more easily formed more efficiently and with a higher yield during the heavy decomposition process. When the proportion of sludge is below the upper limit, the decrease in workability during the heavy decomposition process is suppressed, and solid material is more easily formed more efficiently.

[0021] If the liquid waste contains both tar sludge and sludge, the mass ratio of tar sludge to sludge (tar sludge:sludge) is not particularly limited, but may be, for example, 1:0 (i.e., the liquid waste has no sludge), 2:1 to 10:1, 3:1 to 7:1, or 3:1 to 5:1. When the mass ratio of tar sludge to sludge is above the lower limit, the proportion of tar sludge is higher relative to the sludge, resulting in more efficient weighting and easier acquisition of solid material. When the mass ratio of tar sludge to sludge is below the upper limit, the liquid waste is more efficiently weighted and easier to obtain solid material.

[0022] (Other ingredients) The liquid waste may further contain other components. Other components include, for example, alkaline components and silica / alumina components. Among the above, it is preferable that the other components include alkaline components, and it is even more preferable that they include both alkaline components and silica / alumina components. When liquid waste contains alkaline components, tar sludge or sludge dries and hardens more efficiently. When liquid waste contains alkaline components and silica / alumina components, tar sludge or sludge is dried and heavyened more efficiently. Furthermore, when liquid waste contains alkaline components and silica / alumina components, the resulting solid material (i.e., slag forming sedative) has superior strength (for example, a crushing strength of 20 kg to 2000 kg), resulting in superior handling properties as a slag forming sedative.

[0023] • Alkaline components In this specification, the term "alkaline component" is a concept that includes not only hydroxides of alkali metals and alkaline earth metals, but also compounds that can react with moisture contained in tar sludge and sludge to form hydroxides of alkali metals or alkaline earth metals. Alkaline components have the effect of solidifying the oil contained in tar sludge through saponification reactions, as described later. From the viewpoint of effectively utilizing industrial waste, it is preferable to use dust collection materials, slag powder, etc., that contain alkaline components. Dust collection materials (alkaline dust) are alkaline components such as CaO that are stirred up from slag in converters and steelmaking processes and collected by dust collectors.

[0024] Figure 2 shows an example of the mechanism by which tar sludge and sludge become heavier in the presence of alkaline components. This heavier transformation mechanism is an application of a method in which oils and alkaline substances are stirred at high temperatures, washed with water, and the oil is dried to obtain solid soap from the liquid oil. As shown in Figure 2(A), oily components that may be present in tar sludge and sludge solidify more efficiently through a saponification reaction when mixed with alkaline components and stirred at high temperatures. Furthermore, as shown in Figures 2(B) and 2(C), it is expected that, separate from the saponification reaction, some of the organic matter that may be contained in the tar sludge and sludge (e.g., phenol, benzaldehyde, etc.) will react with the alkaline components in the system to easily generate compounds with higher melting points than the aforementioned organic matter (e.g., sodium phenoxide, sodium). As a result, it is thought that the tar sludge and sludge will become heavier in the reaction system.

[0025] • Silica and alumina components In this specification, the silica-alumina component refers to a material containing silica (SiO2) and alumina (Al2O3). From the viewpoint of effectively utilizing industrial waste, it is preferable that the silica-alumina component includes fly ash. Fly ash is ash mainly composed of silica (SiO2) and alumina (Al2O3) produced when coal is burned, and can be obtained from energy plants such as thermal power plants and steel mills.

[0026] Figure 3 shows an example of the mechanism by which tar sludge and sludge become heavier in the presence of silica and alumina components. As shown in Figure 3(A), in the system, first, the fly ash particles are dissolved in the presence of alkali by mixing dust (an example of an alkaline component; hereinafter also referred to as CaO dust) 12 with fly ash 24 (an example of a silica-alumina component). Subsequently, as shown in Figure 3(B), the calcium hydroxide contained in the dust 12 reacts with the silica and alumina in the fly ash 24, and hydrates (for example, nCaO·SiO2·mH2O (calcium silicate hydrate), 3CaO·Al2O3·6H2O (calcium aluminate hydrate), 3CaO·Al2O3·3CaSO4·32H2O (ettringite), etc.) are produced by hydration bonding, forming a porazon reaction layer 34. Then, as shown in Figure 3(C), the porazon reaction layer 34 becomes a plate-like reaction layer 36, which is firmly bonded and integrated by filling the pores. In this process, it is believed that the tar sludge and sludge become integrated and heavy, resulting in the production of solid material.

[0027] The mass ratio of the total amount of tar sludge and sludge to the alkaline component (total amount of tar sludge and sludge: alkaline component) varies depending on the composition of the raw materials used, but for example, in the case of tar sludge and dust collection, it is preferable that the saponification value relative to the total amount of oil contained in the tar sludge and sludge is between 5 mg / KOH and 500 mg / KOH. If the saponification value is above the lower limit, the liquid waste is more efficiently degraded and solid material is more easily obtained. If the saponification value is below the upper limit, the inhibition of degrading by unreacted alkaline components is suppressed, and the liquid waste is more efficiently degraded and solid material is more easily obtained. Furthermore, it is cost-effective in manufacturing.

[0028] The mass ratio of the alkaline component to the silica / alumina component (alkaline component:silica / alumina component) is not particularly limited, but is preferably 1:10 or more and 10:1 or less, more preferably 3:7 or more and 7:3 or less, and even more preferably 4:6 or more and 6:4 or less. When the mass ratio is within the above range, the inhibition of weightening by unreacted alkaline components and silica / alumina components is suppressed, and the liquid waste is weightened more efficiently, making it easier to obtain solid material. It also has excellent manufacturing cost.

[0029] The mass ratio of the total amount of alkaline components and silica-alumina components to the total amount of tar sludge and sludge (total amount of tar sludge and sludge: total amount of alkaline components and silica-alumina components) varies depending on the composition of the raw materials used, but may be, for example, 1:20 or more and 10:1 or less.

[0030] In one embodiment, when the alkaline component and the silica-alumina component are dust and fly ash, respectively, the total amount of tar sludge and sludge is preferably in the range of 1 / 20 to 5 times the weight of the mixture of dust and fly ash.

[0031] Figure 1 is a schematic diagram showing one embodiment of the method for producing the slag-forming sedative of the present disclosure. In the production method shown in Figure 1, liquid waste 12 containing at least one of tar sludge and sludge is prepared. The liquid waste 12 is immersed in a heating device 14, heated and dried by a water bath or the like to make the tar sludge or sludge heavier, and a solidified product 20 of the liquid waste containing tar sludge or sludge is obtained.

[0032] The heating time in the heavy-hardening process is not particularly limited and may be changed as appropriate depending on the heating temperature. The heating time is preferably 30 minutes to 24 hours, more preferably 1 hour to 15 hours, and even more preferably 3 hours to 10 hours. If the heating time is above the lower limit, the material is heavier more efficiently and in higher yield, making it easier to obtain solid material. Furthermore, the moisture content of the resulting solid material is reduced, resulting in superior slag forming sedation. If the heating time is below the upper limit, it is preferable from the standpoint of manufacturing cost and safety.

[0033] In this specification, heating time refers to the holding time after reaching the maximum temperature.

[0034] The decomposition process is preferably carried out by heating the liquid waste at a temperature above the temperature at which the liquid components (e.g., water) contained in the liquid waste volatilize, more preferably at 80°C to 350°C, even more preferably at 120°C to 250°C, and particularly preferably at 150°C to 220°C. When the heating temperature is above the lower limit, the material is heavier more efficiently, making it easier to obtain solid material. Furthermore, the moisture content of the resulting solid material is reduced, resulting in superior slag forming sedation. When the heating temperature is below the upper limit, it is preferable from the standpoint of manufacturing cost and safety.

[0035] The means for heating the liquid waste are not particularly limited, but known heat sources such as heaters can be used. For example, since tar sludge and sludge, which are raw materials for sedatives, are generated in steel mills, it is preferable that the heavy-conditioning process utilizes waste heat from the steel mill (e.g., waste heat from coke ovens) to heat the liquid waste. By heating and drying the liquid waste using waste heat from the steel mill to heavy-condition it, sedatives can be manufactured efficiently and at low cost.

[0036] Examples of liquid waste containing at least one of tar sludge and sludge include liquid waste containing at least one of tar sludge and sludge generated from chemical processes such as coke ovens.

[0037] The heavy-conditioning process is carried out under a low-oxygen atmosphere (for example, an oxygen concentration of 1,000 ppm or less) to prevent combustion of liquid waste. From the viewpoint of convenience, the heavy-conditioning process is preferably carried out under a nitrogen or argon atmosphere.

[0038] In the weighting process, from the viewpoint of obtaining solid material with a higher yield, it is preferable to weight the solid content of the liquid waste to 80% by mass or more, more preferably 85% by mass or more, and even more preferably 88% by mass or more. In other words, it is preferable that the solid content of the liquid waste be as close to 100% by mass as possible.

[0039] [Other processes] The method for producing a slag-forming sedative according to this disclosure may further include other steps besides the heavy-forming step. Examples of other steps include, after the heavy-forming step, 1) a purification step in which the solid obtained by heavy-forming is washed and purified with a solvent in which tar sludge and sludge do not dissolve; and 2) a processing step in which the solid is cut, shaved, crushed, or otherwise processed (for example, the solid material of liquid waste may be cut or crushed to a size of about 10 mm to 150 mm).

[0040] The order in which the other components are mixed with the tar sludge or sludge is not particularly limited; all of these components may be mixed simultaneously, or each component may be mixed in stages. When other components include alkaline components and silica-alumina components, the order in which these are mixed with the tar sludge or sludge is, from the viewpoint of effectively utilizing the cementation of the alkaline components and silica-alumina components by the pozzolanic reaction described above, to be mixed and cemented first, and then mixed with the tar sludge or sludge.

[0041] The method for producing a slag-forming sedative according to this disclosure may use a continuous extrusion molding machine. Figure 4 is a schematic diagram showing an example of the configuration of a continuous extrusion molding machine. As shown in Figure 4, the continuous extrusion molding machine 100 includes a kneading section 110 for mixing raw materials and an extrusion section 120 equipped with a screw for extruding solid material. Although not shown, the continuous extrusion molding machine 100 is equipped with a temperature control mechanism.

[0042] Liquid waste containing at least one of tar sludge and sludge is fed into the hopper 112 and mixed in the mixing section 110. Subsequently, during the process of supplying the liquid waste to the extrusion section 120, heavy formation (i.e., solidification) is promoted. Then, solid material is continuously extruded from the extrusion port 122.

[0043] Using the continuous extrusion molding machine 100, the entire process from heating and drying to forming can be carried out in one step. Furthermore, if the liquid waste also contains either an alkaline component or a silica-alumina component, the alkaline component and / or the silica-alumina component will be mixed more uniformly with the tar sludge and / or sludge. In addition, the density and crushing strength of the resulting solid can be controlled by adjusting the pressure of the extrusion section 120.

[0044] [Sedation methods for slag forming] The method for calming slag forming according to this disclosure includes a calming step of adding a slag forming sedative, manufactured by the method for manufacturing a slag forming sedative according to this disclosure, to the slag forming to calm the forming. The slag forming sedative may, for example, be added to the slag forming in the converter from a hopper, or it may be manually added to the slag forming that has been discharged from the converter or the like into a slag pot. Because slag forming sedatives are solid, they are easy to handle in terms of transportation, storage, and application, and they effectively sedate slag formation when added.

[0045] Furthermore, according to this disclosure, by not processing the tar sludge generated in coke production in a coke oven, it is possible to reduce the cost of coke by increasing the proportion of inexpensive materials, and by utilizing dust collection, alkaline slag powder, and fly ash, it is also possible to obtain the benefit of reducing industrial waste disposal costs. [Examples]

[0046] The present disclosure will be described in detail below with reference to examples, but the present invention is not limited in any way to these examples.

[0047] [Example 1] <Manufacturing of slag-forming sedatives> Liquid waste containing 60 kg of tar sludge was divided into three pails and heated in a nitrogen-purging furnace. The furnace uses kerosene to heat the bottom from the outside, so the atmosphere inside the furnace is oxygen-free during heating. First, the entire raw material was left to stand in the furnace at room temperature and then nitrogen purged. Heating was then started. The heating time was approximately 8 hours. The furnace temperature was measured using a thermocouple inside the furnace. The bottom surface heated to approximately 200°C in about 20 minutes, and the middle of the furnace near the height of the pails reached approximately 200°C in about 60 minutes. During the process, volatile components were released, so the material was cooled with a water cooling system and the liquid was condensed and recovered. After heating was complete, the furnace was opened after it had returned to room temperature. As a result, asphalt-like solid material was obtained from the viscous liquid waste containing tar sludge with a yield of 90.4%. From the mass difference before and after drying and heavyening, it was found that the liquid component contained in the liquid waste before drying was 5.5% (measured value). Furthermore, it is estimated that 4.1% of the liquid waste before drying is composed of gaseous components.

[0048] <Rating> 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, 2mm to 5mm sized pig iron pieces (1g) were added to the Tammann furnace. Forming was induced by maintaining the furnace temperature at 1350°C. The forming height was measured by inserting a SUS rod coated with alumina into the furnace. The change over time was also measured from the adhesion depth. This experiment was repeated three times. The results are shown in Figure 5.

[0049] Figure 5 shows the relationship between time and slag height when the slag forming sedative manufactured in Example 1 is added to the slag forming process. On the horizontal axis (time) of Figure 5, A represents the time when forming occurs, and B represents the time when the sedative is added. As shown in Figure 5, the forming height peaked at about 1 minute and 30 seconds, and immediately after the peak, the slag forming sedative manufactured above (0.5 g) was added, and the sedative effect was quantitatively evaluated from the change in forming height. After sedation, the height decreased to about 1 / 4 of the peak height. This is a sedative effect comparable to that of conventional slag forming sedatives. [Explanation of Symbols]

[0050] 12. Liquid waste containing at least one of tar sludge and sludge. 14 Heating device 20 Solidified material 100 Continuous Extrusion Molding Machines 110 Mixing section 112 Hopper 120 Extrusion section 122 Extrusion port

Claims

1. A method for producing a slag-forming sedative, comprising a heavy-forming step in which liquid waste containing at least one of tar sludge and sludge is heated and dried in a low-oxygen atmosphere to increase its weight.

2. The method for producing a slag-forming sedative according to claim 1, wherein the heavy-conditioning step involves heating the liquid waste to a temperature above the temperature at which the liquid components contained in the liquid waste volatilize.

3. The method for producing a slag-forming sedative according to claim 1 or claim 2, wherein the heavy-setting step is heated at a temperature of 120°C or higher and 250°C or lower.

4. The method for producing a slag-forming sedative according to claim 1 or claim 2, wherein the weighting step weights the solid content of the liquid waste to 80% by mass or more.

5. A method for producing a slag-forming sedative according to claim 1 or claim 2, wherein the proportion of tar in the liquid waste is 30% by mass or more.

6. A method for producing a slag-forming sedative according to claim 1 or claim 2, wherein the proportion of the sludge in the liquid waste is 8% by mass or more and 30% by mass or less.

7. The method for producing a slag forming sedative according to claim 1 or claim 2, wherein the heavy-conditioning step involves heating the liquid waste using waste heat from a steel mill.

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

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