Operating method for direct cooling water systems, oil separation accelerator, and treatment equipment for direct cooling water systems

Abstract

To provide a method for operating a direct cooling water system that efficiently separates oil and suspended solids from direct cooling water containing oil and metallic scales such as iron oxide, iron, etc., and that can easily recover oil.SOLUTION: This method includes the steps for: causing an oil separation accelerator to be present in the direct cooling water system wastewater in the turbulent flow path from a scale sluice 1 to a scale pit 2; removing the separated floating oil in a lateral flow settling tank 3 downstream of the scale pit; and collecting the wastewater from which oil has been removed in the lateral flow settling tank, cooling it, and reusing it as direct cooling water. The lateral flow settling tank is equipped with a partition weir, the partition weir is located in the lateral flow settling tank with the upper end protruding from the water surface and the lower end separated from the bottom of the lateral flow settling tank to a predetermined depth from the water surface, and the partition weir stops the flow of floating oil and allows cooling wastewater with separated oil to pass between the bottom of the partition weir and the bottom of the lateral flow settling tank.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an operation method of a so-called direct cooling water system such as spray water in continuous casting and rolling in a steel mill.

Background Art

[0002] In a steel mill, a large amount of mill scale is generated from treatment facilities such as direct cooling water used for cooling steel materials during the production of steel materials. Such scales are mainly composed of metals such as iron oxide and iron generated from steel materials, and metal scales containing no oil are useful resources that can be reused in the ironmaking and steelmaking processes. However, during the continuous casting process and the rolling process, lubricating oil and rolling oil used in manufacturing machines such as rolling oil and rolling mills are mixed into the cooling water containing scales, so the generated metal scales often contain water and several mass% of oil. Moreover, oil may be inevitably mixed during operations such as the replacement of rolling rolls. Every time such an operation is carried out, the oil concentration in the scale fluctuates greatly, specifically, it may fluctuate within the range of 1 to 10 mass%.

[0003] Such direct cooling water is treated with organic and inorganic flocculants in a scale pit or an agglomeration sedimentation facility, and after cooling, it is reused as cooling water.

[0004] As a treatment of such a direct cooling water system, a technique has been proposed to agglomerate and sediment coarse suspended substances (coarse SS) such as metal powder and oil with a particle size of 50 μm or more and fine suspended substances (fine SS) with a particle size of less than 50 μm contained in the direct cooling water in the same treatment and remove them simultaneously (see Patent Documents 1 to 4). This treatment method aims to obtain clear treated water by adding a specific polymer to agglomerate and sediment the suspended substances containing oil in the scale pit and remove them. In a treatment method that involves the coagulation and sedimentation of coarse suspended solids (SS) containing oil and other substances in the same process, the sludge accumulated in scale pits, etc., will contain oil. On the other hand, scale that does not contain oil becomes a useful resource that can be reused in steelmaking processes, etc., as described above. Therefore, if the sludge accumulated in scale pits contains oil, it is necessary to separate the oil in order to reuse the sludge.

[0005] One method for separating oil from oily sludge is to mix the oily sludge with an organic solvent as an extractant and vigorously stir it to extract the oil from the oily sludge into the organic solvent (see Patent Document 5). On the other hand, since oily sludge contains water, a stabilized emulsion is formed in such a process. To break down (demulsify) such a stabilized emulsion requires a multi-disc centrifuge, which is an expensive investment (see Patent Documents 6 and 7).

[0006] Furthermore, oil-containing sludge is temporarily stored in layers such as sedimentation tanks and concentration layers at steel mills, and needs to be transported to processing facilities when it is to be disposed of or processed as a raw material for steelmaking. At this time, since oil-containing sludge often has a high water content and is highly fluid, there is a concern that the oil-containing sludge and the oil it contains may leak out during transport. Therefore, oil-containing sludge is subject to limitations in terms of transport volume and drying, compared to sludge that does not contain oil and is used directly as a raw material for steelmaking. Thus, it is necessary to process oil-containing sludge into a material that is easy to transport (Patent Document 8). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 6068112 [Patent Document 2] Patent No. 6374157 [Patent Document 3] Patent No. 6374352 [Patent Document 4] Patent No. 6374351 [Patent Document 5] Japanese Patent Publication No. 2015-132011 [Patent Document 6] Japanese Patent Application Publication No. 3-238059 [Patent Document 7] Japanese Patent Publication No. 2005-349371 [Patent Document 8] Japanese Patent Publication No. 2019-98327 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Thus, oily sludge is subject to restrictions not only in its treatment but also in its transportation. Therefore, this disclosure provides a method for operating a direct cooling water system that efficiently separates oil from other suspended solids in direct cooling water containing oil and metal scale such as iron oxide and iron, suppresses the generation of oily sludge, and allows for easy recovery of the oil. [Means for solving the problem]

[0009] This disclosure, in one aspect, describes a method for operating a direct cooling water system containing oil and metal scale such as iron oxide or iron, In the turbulent flow path from the scale sluice to the scale pit, an oil separation accelerator is present in the direct cooling water system wastewater. The separated floating oil is removed in a transverse flow sedimentation tank downstream of the scale pit, and This includes recovering the wastewater from which oil has been removed in the aforementioned cross-flow sedimentation tank, cooling it, and using it again directly as cooling water, The present invention relates to a method for operating a direct cooling water system, wherein the cross-flow sedimentation tank is equipped with a partition weir, the partition weir is positioned in the cross-flow sedimentation tank with its upper end protruding above the water surface and its lower end spaced apart from the bottom surface of the cross-flow sedimentation tank, the partition weir dams up the flow of the floating oil, and wastewater from which the oil has been separated is allowed to pass through the spaced-away portion between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank.

[0010] This disclosure, in other aspects, relates to a treatment facility for a direct cooling water system containing oil and metal scale. The treatment facility of this disclosure is The path that forms the turbulent state from the scale sluice to the scale pit, An oil separation accelerator supply device for adding an oil separation accelerator to the aforementioned cooling water, It includes a transverse flow sedimentation tank located downstream of the scale pit to remove separated oil, The aforementioned cross-flow sedimentation tank is equipped with a partition weir, The partition weir is positioned in the cross-flow sedimentation tank such that its upper end protrudes above the water surface and its lower end is spaced apart from the bottom surface of the cross-flow sedimentation tank, thereby blocking the flow of the floating oil, and allowing wastewater separated from the oil to pass through the space between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank.

[0011] In further aspects, the Disclosure relates to an oil separation accelerator for carrying out the operation method of the direct cooling water system of the Disclosure, wherein the oil separation accelerator comprises a cationic or amphoteric organic coagulant or polymer. [Effects of the Invention]

[0012] According to the method disclosed herein, oil can be efficiently separated from direct cooling water containing oil and metal scales such as iron oxide and iron, while suppressing the generation of oily sludge, and the oil that floats to the surface of the water can be easily recovered. According to this disclosure, in one or more embodiments, the amount of oil contained in the generated sludge can be suppressed. Therefore, according to this disclosure, in one or more embodiments, the special treatment required to separate oil from oil-containing sludge, which was necessary in conventional methods of removing coarse SS and fine SS containing oil by coagulation and sedimentation in the same process, can be eliminated. [Brief explanation of the drawing]

[0013] [Figure 1]FIG. 1 is a schematic diagram showing the configuration of a direct cooling water circulation system for a continuous casting process. [Figure 2] FIGS. 2A and 2B are drawings for explaining an example of a form in which a partition weir is arranged in a cross-flow sedimentation tank. FIG. 2A is a plan view seen from above, and FIG. 2B is a cross-sectional view taken along line 2A-2A.

Mode for Carrying Out the Invention

[0014] In treating direct cooling water containing oil and metal scales such as iron oxide and iron, according to the present disclosure, in a turbulent flow path from a scale through-flow to a scale pit, by causing an oil separation promoter to be present in the cooling water, oil can be efficiently separated, the generation of oily sludge can be suppressed, and the separated and floating oil can be easily recovered in a cross-flow sedimentation tank provided with a partition weir on the downstream side of the scale pit. This is based on the finding.

[0015] According to one aspect of the present disclosure, the separated floating oil (floating oil) is blocked by a partition weir arranged in a cross-flow sedimentation tank, and the treated water can be recovered and cooled by allowing the cooling water wastewater from which the oil has been separated to pass between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank, and then used again as direct cooling water.

[0016] [Operation Method of the Present Disclosure] The present disclosure relates to an operation method of a so-called direct cooling water system such as spray water in continuous casting or rolling in a steelworks. The operation method of the present disclosure includes at least the following (1) to (3). (1) Causing an oil separation promoter to be present in the cooling water in a turbulent flow path from a scale through-flow to a scale pit (2) In a cross-flow sedimentation tank provided with a partition weir on the downstream side of the scale pit, blocking the flow of the floating oil by the partition weir to remove the oil, and allowing the cooling water from which the oil has been separated to pass between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank (3) The wastewater from which the oil has been removed in the cross-flow sedimentation tank is recovered, cooled, and reused as direct cooling water.

[0017] In this disclosure, "direct cooling water system" means a water system in which cooling water that is sprayed directly onto an object or into which an object is immersed is recooled and used in one or more embodiments. The direct cooling water in this disclosure contains oil and metal scale. Examples of direct cooling water in one or more embodiments include cooling water containing oil and metal scale that is sprayed directly onto or immersed in steel products such as steel materials and steel plates, or rolling rolls, in the forming process of a continuous casting process or rolling process in a steel mill, for cooling or descaling purposes. Examples of metal scales include iron oxide and iron in one or more embodiments.

[0018] The operating method of this disclosure includes the presence of an oil separation accelerator in a turbulent flow path. In this disclosure, "turbulent conditions" refer to, in one or more embodiments, a state in which the flow or vortex of the cooling water is irregular, or a state in which the flow velocity of the cooling water is 0.5 m / s or more. This is because if the flow velocity of the cooling water is 0.5 m / s or more, the flow or vortex of the cooling water containing metal scale will be irregular. In this disclosure, the "turbulent flow path from the scale sluice to the scale pit" is not particularly limited, but in one embodiment, it may include the scale sluice, the scale pit, and the piping between the scale sluice and the scale pit.

[0019] In one or more embodiments, a scale sluice is a location for recovering direct cooling water from a continuous casting or rolling process. In one or more embodiments, the scale sluice may have the function of discharging, circulating, and reusing the cooling water recovered from the continuous casting or rolling process, and the function of moving the cooling water, which contains oil and metal scale such as iron oxide or iron, to an outdoor scale pit.

[0020] In one or more embodiments, cationic organic coagulants or polymers or amphoteric organic coagulants or polymers are preferred as oil separation accelerators. Examples of cationic organic coagulants or polymers in one or more embodiments include alkylamine-epichlorohydrin condensates, polyethyleneimines, alkylenedichloride-polyalkylene polyamine condensates, dicyandichloride-polyalkylene polyamine condensates, polydimethylaminoethyl methacrylate, and polydiallyldimethylammonium chloride. Examples of amphoteric organic coagulants or polymers in one or more embodiments include copolymers of trialkylamine and acrylic acid, and copolymers of diallyldimethylammonium chloride and acrylic acid.

[0021] In one or more embodiments, the oil separation accelerator may be one type or more types. In one or more embodiments of the operating method of this disclosure, organic or inorganic flocculants commonly used to floccate and precipitate iron oxide or iron scale may be used in the usual manner, in addition to the oil separation accelerator. The oil separation accelerator used in the operating method of this disclosure may, in one or more embodiments, contain an inorganic flocculant or may not contain an inorganic flocculant.

[0022] In one or more embodiments, the amount of oil separation accelerator added is 0.001 mg / L to 5 mg / L, preferably 0.05 mg / L to 5 mg / L. In one embodiment, which is not particularly limited in this disclosure, the concentration of the oil separation accelerator in the turbulent flow path is 0.001 mg / L to 5 mg / L, preferably 0.05 mg / L to 5 mg / L, in one or more embodiments.

[0023] The operating method of this disclosure includes removing the separated floating oil in a transverse flow sedimentation tank equipped with a partition weir, located downstream of the scale pit. The partition weir is positioned within the transverse flow sedimentation tank with its upper end protruding above the water surface and its lower end spaced apart from the bottom of the transverse flow sedimentation tank. This allows the flow of floating oil to be blocked by the partition weir, while also allowing wastewater separated from the oil to pass through the space between the lower end of the partition weir and the bottom of the transverse flow sedimentation tank (the spaced-away portion).

[0024] In one or more embodiments, the recovery (or removal) of oil whose flow has been blocked by the partition weir can be carried out using a skimmer or an oil recovery device floating on the surface of the cross-flow sedimentation tank. Therefore, in one or more embodiments, the cross-flow sedimentation tank may be equipped with a skimmer, an oil recovery device, and a recovery tank for storing or processing the recovered oil.

[0025] In one or more embodiments, a cross-flow sedimentation tank (also called a cross-flow coagulation sedimentation tank) causes oil to suspend and other suspended solids to settle (or coagulate and settle) during the process (time) in which the water to be treated moves along the longitudinal direction of the tank. For this reason, from the viewpoint of improving separation efficiency, the larger the cross-flow sedimentation tank (especially its length), the better (the longer the better). However, from the viewpoint of costs such as capital investment, the size of the equipment from which the cooling water system is directly discharged, the amount of wastewater discharged, and the size of the location where the cross-flow sedimentation tank is installed should be determined appropriately.

[0026] In one or more embodiments, the partition weir may be positioned perpendicular to the flow direction. The shape of the partition weir may be oblique to the flow direction in one or more embodiments, or it may be a V-shape or a U-shape, with two plate-like objects extending from the side of the cross-flow sedimentation tank positioned to close along the flow direction, in order to smooth the flow of cooling water and to make the recovery and / or separation of oil easier or more efficient. Figures 2A and 2B are diagrams illustrating an example in which a partition weir 10 is positioned in a cross-flow sedimentation tank 3, where Figure 2A is an example of a view from above, and Figure 2B is a cross-sectional view along the line 2A-2A. In Figure 2A, the partition weir 10 is positioned in a V-shape such that the intersection (vertex) of the two plate-like objects extending from the side of the cross-flow sedimentation tank 3 is located on the downstream side of the cross-flow sedimentation tank 3. As shown in Figures 2A and 2B, the cross-flow sedimentation tank 3 may also include, in addition to the partition weir 10, an oil recovery device 11 for recovering oil separated by flotation, and a sludge pump 14 for recovering suspended solids that have flocculated and settled. In one or more embodiments, the oil recovery device 11 is equipped with a float and is positioned floating on the water surface upstream of the partition weir 10. In one or more embodiments, the sludge pump 14 is positioned on the bottom of the cross-flow sedimentation tank 3 upstream of the partition weir 10.

[0027] In one or more embodiments, the partition weir may be configured in a V-shape by two plate-like objects extending from the side of the transverse flow sedimentation tank, as shown in Figure 2A. The angle (θ) between the two plate-like objects may be arranged to be acute in order to enable more efficient recovery and / or separation of oil, or it may be arranged to be obtuse in order to simplify the recovery of oil dammed by the partition weir. In one or more embodiments, the angle (θ) is 30° or more, 40° or more, 50° or more, 60° or more, 70° or more, 80° or more, 90° or more, or 110° or more. In one or more embodiments, the angle (θ) is 170° or less, 160° or less, 150° or less, 140° or less, 130° or less, or 125° or less.

[0028] In one or more embodiments, the partition weir is positioned in the cross-flow sedimentation tank such that the distance between the water surface and the lower end of the partition weir (d1 in Figure 2B) is 0.5 m or more. In one or more embodiments, the distance between the water surface and the lower end of the partition weir (d1 in Figure 2B) is 1 m or more, 1.5 m or more, or 2 m or more. In one or more embodiments, the distance between the water surface and the lower end of the partition weir is 2.5 m or less, or 2 m or less. In one or more embodiments, the partition weir is positioned in the cross-flow sedimentation tank such that the distance between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank (length of the separation between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank) (d2 in Figure 2B) is 0.5 m or more. In one or more embodiments, the distance between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank (d2 in Figure 2B) is 1 m or more, or 2 m or more. In one or more embodiments, the distance between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank is 3 m or less or 2.5 m or less. In one or more embodiments, the partition weir may be positioned such that the distance (d1) between the water surface and the lower end of the partition weir is 1 / 2 or more, 2 / 3 or more, or 3 / 4 or more of the depth of the cross-flow sedimentation tank (distance between the water surface and the cross-flow sedimentation tank: D).

[0029] In one or more embodiments, the upper end of the partition weir is sufficient to block the flow of floating oil, and to protrude (expose) above the water surface to the extent that the oil does not overflow the upper end of the partition weir. In one or more embodiments, the upper end of the partition weir is sufficient to be exposed to the water surface by 10 cm or more, 30 cm or more, or 50 cm or more.

[0030] The number of partition weirs is not particularly limited; in one or more embodiments, there may be one, or two or more may be arranged in the direction of flow in the transverse sedimentation tank.

[0031] The location of the partition weir is not particularly limited, and in one or more embodiments, it can be positioned at a location less than 1 / 2, less than 1 / 3, or less than 1 / 4 of the upstream distance from the downstream end of the transverse flow sedimentation tank.

[0032] In one or more embodiments, the operating method of the present disclosure may include recovering suspended solids other than oil (sludge components including metal scale) that have settled in a cross-flow sedimentation tank. In one or more embodiments of the operating method of the present disclosure, since the oil is separated by flotation, the suspended solids (sludge components) have a low oil content and preferably are substantially oil-free. In this disclosure, "substantially oil-free" means that the amount of oil in the suspended solids (sludge components) is less than 0.5 mg / L (below the detection limit). In one or more embodiments, the cross-flow sedimentation tank in the operating method of the present disclosure may further include a pump (such as a sludge pump) for recovering the suspended solids (sludge components), and a sludge recovery tank (tank) for storing or treating the sludge recovered by the pump.

[0033] The operating method of this disclosure includes recovering the wastewater from which oil has been removed in a cross-flow sedimentation tank, cooling it, and using it again as direct cooling water. The oil-containing wastewater (direct cooling water) treated by the operating method of this disclosure may, in one or more embodiments, be used as direct cooling water in a rolling mill or the like after passing through a filter and a cooling tower. The operating method of this disclosure may also be described in one or more embodiments as a direct cooling water treatment method. Furthermore, the operating method of this disclosure may also be described in one or more embodiments as a method for operating or managing the direct cooling water treatment equipment in this disclosure.

[0034] [Processing equipment in this disclosure] This disclosure, in other aspects, relates to a treatment facility for a direct cooling water system containing oil and metal scale. The treatment facility of this disclosure is The path that forms the turbulent state from the scale sluice to the scale pit, An oil separation accelerator supply device for adding an oil separation accelerator to the aforementioned cooling water, It includes a transverse flow sedimentation tank located downstream of the scale pit to remove the separated floating oil, The aforementioned cross-flow sedimentation tank is equipped with a partition weir, The partition weir is positioned within the transverse flow sedimentation tank with its upper end protruding above the water surface and its lower end spaced apart from the bottom of the transverse flow sedimentation tank. The partition weir blocks the flow of the floating oil, and wastewater from which the oil has been separated can pass through the space between the lower end of the partition weir and the bottom of the transverse flow sedimentation tank. The treatment equipment of the present disclosure enables efficient operation of the direct cooling water system of the present disclosure.

[0035] The processing equipment in this disclosure, including the pathways that form turbulent flow conditions from the scale sluice to the scale pit, the transverse flow sedimentation tanks, and the partition weirs and other associated equipment, are the same as those in the operating method of this disclosure.

[0036] [Oil separation accelerators of this disclosure] In further aspects, the Disclosure relates to an oil separation accelerator for carrying out the operation method of the direct cooling water system of the Disclosure, wherein the oil separation accelerator comprises a cationic or amphoteric organic coagulant or polymer. The cationic or amphoteric organic coagulant or polymer in the oil separation accelerator of this disclosure is the same as in the operating method of this disclosure.

[0037] One embodiment of the present disclosure, which is not particularly limited, will be described with reference to Figure 1. One embodiment of the operating method of the present disclosure includes the following (1) to (4). (1) In scale sluice 1, an amphoteric organic coagulant or polymer is added to the direct cooling water system wastewater. (2) In scale pit 2, a cationic organic coagulant or polymer and an inorganic coagulant are added to the direct cooling water system wastewater. (3) In the cross-flow sedimentation tank 3 equipped with a partition weir, the oil in the wastewater to which the chemical agent has been added is suspended, and other suspended substances (sludge components) are coagulated and settled. (4) The wastewater from which the oil has been removed is collected, cooled, and reused as direct cooling water. The following details each of the steps (1) to (4).

[0038] (1) In the scale sluice 1, an amphoteric organic coagulant or polymer is directly added to the cooling water system wastewater by the chemical addition device 7. In one or more embodiments, the amount of amphoteric organic coagulant or polymer added is 0.001 mg / L to 5 mg / L, preferably 0.05 mg / L to 5 mg / L. In addition, in one or more embodiments, the concentration of amphoteric organic coagulant or polymer in the wastewater of the scale sluice is 0.001 mg / L to 5 mg / L, preferably 0.05 mg / L to 5 mg / L.

[0039] (2) In the scale pit 2, a cationic organic coagulant or polymer and inorganic coagulant are directly added to the cooling water system wastewater using a chemical addition device (not shown). Cationic organic flocculants or polymers and inorganic coagulants may be added separately or mixed together. The cationic organic flocculants or polymers and inorganic coagulants may be added at the same location or at different locations within the scale pit. In one or more embodiments, the amount of cationic organic flocculant or polymer added is 0.001 mg / L to 5 mg / L, preferably 0.05 mg / L to 5 mg / L. Furthermore, in one or more embodiments, the concentration of cationic organic flocculant or polymer in the wastewater of the scale sluice is 0.001 mg / L to 5 mg / L, preferably 0.05 mg / L to 5 mg / L. In one or more embodiments, the amount of inorganic coagulant added is 0.001 mg / L to 20 mg / L, preferably 0.1 mg / L to 10 mg / L. In addition, in one or more embodiments, the concentration of cationic organic coagulant or polymer in the wastewater of the scale sluice is 0.001 mg / L to 20 mg / L, preferably 0.1 mg / L to 10 mg / L.

[0040] (3) In the cross-flow sedimentation tank 3 equipped with a partition weir, the oil in the wastewater to which the chemical agent has been added is suspended, and other suspended substances (sludge components) are coagulated and settled. The oil in the wastewater to which the aforementioned chemical has been added and which has been introduced into the cross-flow sedimentation tank 3 is separated from the wastewater and floats to the surface. The flow of the floating oil is dammed by a partition weir installed in the cross-flow sedimentation tank. The dammed oil can be easily recovered, for example, by a skimmer or an oil recovery device placed on the water surface. In addition, suspended solids other than oil (sludge components) coagulate and settle in the cross-flow sedimentation tank 3 and can be recovered, for example, by a sludge pump. Therefore, wastewater from which oil and other suspended solids have been removed can pass through the gap between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank.

[0041] (4) The wastewater from which the oil has been removed is collected, cooled, and reused as direct cooling water.

[0042] In the embodiments described above, an example was given in which an amphoteric organic coagulant or polymer was added in the scale sluice 1, and a cationic organic coagulant or polymer and an inorganic coagulant were added in the scale pit 2. However, the types of agents used and the locations of addition in the operating method of this disclosure are not limited to these examples.

[0043] This disclosure further relates to one or more embodiments described below. [1] A method for operating a direct cooling water system containing oil and metal scale, In the turbulent flow path from the scale sluice to the scale pit, an oil separation accelerator is present in the direct cooling water system wastewater. The separated floating oil is removed in a transverse flow sedimentation tank downstream of the scale pit, and This includes recovering the wastewater from which oil has been removed in the aforementioned cross-flow sedimentation tank, cooling it, and using it again directly as cooling water, The cross-flow sedimentation tank is equipped with a partition weir, the partition weir being positioned within the cross-flow sedimentation tank with its upper end protruding above the water surface and its lower end spaced apart from the bottom surface of the cross-flow sedimentation tank, the partition weir damming the flow of the floating oil and allowing the wastewater from which the oil has been separated to pass through the spaced portion between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank. Operating procedure for direct cooling water systems. [2] The partition weir is positioned at an angle or in a V-shape with respect to the flow direction of the transverse sedimentation tank, as described in [1] for the operation of the direct cooling water system. [3] The method for operating a direct cooling water system according to [1] or [2], wherein the oil separation accelerator is a cationic or amphoteric organic coagulant or polymer. [4] The method for operating a direct cooling water system according to [3], wherein the cationic organic coagulant or polymer is one or more organic coagulants or polymers selected from alkylamine-epichlorohydrin condensates, polyethyleneimines, alkylenedichloride-polyalkylene polyamine condensates, dicyandichloride-polyalkylene polyamine condensates, polydimethylaminoethyl methacrylate, and polydiallyldimethylammonium chloride. [5] The method for operating a direct cooling water system according to [3], wherein the amphoteric organic coagulant or polymer is one or more organic coagulants or polymers selected from copolymers of trialkylamine and acrylic acid and copolymers of diallyldimethylammonium chloride and acrylic acid. [6] A direct cooling water treatment facility containing oil and metal scale, The path that forms the turbulent state from the scale sluice to the scale pit, An oil separation accelerator supply device for adding an oil separation accelerator to the aforementioned cooling water, It includes a transverse flow sedimentation tank located downstream of the scale pit to remove the separated floating oil, The aforementioned cross-flow sedimentation tank is equipped with a partition weir, A direct cooling water treatment facility, wherein the partition weir is positioned within the cross-flow sedimentation tank such that its upper end protrudes above the water surface and its lower end is spaced apart from the bottom surface of the cross-flow sedimentation tank, thereby damming the flow of the floating oil, and allowing wastewater from which the oil has been separated to pass through the space between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank. [7] An oil separation accelerator for carrying out the direct cooling water system operation method described in any of [1] to [5], The oil separation accelerator comprises a cationic or amphoteric organic coagulant or polymer. [8] The oil separation accelerator according to [7], wherein the cationic organic coagulant or polymer is one or more organic coagulants or polymers selected from alkylamine-epichlorohydrin condensates, polyethyleneimines, alkylenedichloride-polyalkylene polyamine condensates, dicyandichloride-polyalkylene polyamine condensates, polydimethylaminoethyl methacrylate, and polydiallyldimethylammonium chloride. [9] The oil separation accelerator according to [7] or [8], wherein the amphoteric organic coagulant or polymer is one or more organic coagulants or polymers selected from copolymers of trialkylamine and acrylic acid and copolymers of diallyldimethylammonium chloride and acrylic acid.

[0044] The present disclosure will be further described below using examples. However, the present disclosure shall not be construed as being limited to the following examples. [Examples]

[0045] As shown in Figures 1 and 2, the direct cooling water circulation system for the continuous casting process (circulation water volume: 1400 m³) 3 In the process described in / h), a treatment was carried out to remove sludge components. The direct cooling water circulation system shown in Figure 1 comprises a scale sluice 1, a scale pit 2, a cross-flow sedimentation tank 3, a filter 4, and a cooling tower 5. The cooling water used to cool the steel material in the rolling process is introduced from the scale sluice 1, which is located below the steel rolling line, through piping (trough, culvert) 6 to the scale pit 2. The scale sluice 1 is equipped with a chemical additive device 7. The cross-flow sedimentation tank 3 comprises a partition weir 10, an oil recovery device 11, an oil recovery tank (tank) 8, a sludge pump 14, and a sludge recovery tank (tank) 9. The oil recovered by the oil recovery device 11 is stored in the oil recovery tank (tank) 8, and the suspended solids (sludge components) recovered by the sludge pump 14 are recovered in the sludge recovery tank (tank) 9.

[0046] The sludge removal process was carried out for two months using the following procedure. Scale Sluice 1 • Oil separation accelerator to be added: Copolymer of diallyldimethylammonium chloride and acrylic acid (weight-average molecular weight: approximately 400,000, manufactured by Narco Company) • Dosage: 0.5 mg / L of circulating water Scale Pit 2 • Additive: PAC (polyaluminum chloride) 6 mg / L Cationic organic flocculant (manufactured by Katayama Chemical Industry Research Institute Co., Ltd., product name "Floclan (registered trademark) SC-640") 1 mg / L As described above, in Scale Sluice 1, an oil separation accelerator was added to the circulating water before oil separation, and in Scale Pit 2, the above-mentioned PAC and cationic organic flocculant were added, and in Crossflow Sedimentation Tank 3, the oil was suspended and other suspended substances (sludge components) were flocculated and precipitated. A V-shaped partition weir (d2: 1m, d2: 1m, 30cm, θ: 120°) was placed in the transverse flow sedimentation tank 3 downstream of the scale pit 2, 1m behind the sludge pump 14, and the cooling water from which the oil had been separated was passed through the gap between the lower end of the partition weir and the bottom surface of the transverse flow sedimentation tank 3. Test water samples were collected from the water surface near the upstream and downstream sides of the partition weir, and the oil content of the test water was measured using the N-hexane extraction substance analysis method in accordance with JIS K 0102. The oil content of the test water sampled from near the water surface upstream of the partition weir 10 (▽12 in Figure 2A) ranged from a maximum of 52 mg / L to a minimum of 15 mg / L and an average of 35 mg / L, while the oil content of the test water sampled from near the water surface downstream of the partition weir 10 (▽13 in Figure 2A) ranged from a maximum of 3.5 mg / L to a minimum of less than 0.5 mg / L and an average of 0.7 mg / L. Furthermore, no oil content was detected in the sludge coagulated and settled in the cross-flow sedimentation tank 3 (less than 0.5 mg / L). As is clear from these results, by implementing the operating method of this disclosure, it is possible to efficiently separate oil from direct cooling water containing oil and metal scale such as iron oxide and iron, to cool the treated water as is and use it as direct cooling water, and to suppress the amount of oil contained in the generated sludge.

Claims

1. A method for operating a direct cooling water system containing oil and metal scale, In a scale sluice, by adding an oil separation accelerator to the direct cooling water system wastewater containing oil and metal scale, the oil separation accelerator is present in the direct cooling water system wastewater in the turbulent flow path from the scale sluice to the scale pit. The separated floating oil is removed in a transverse flow sedimentation tank downstream of the scale pit, and This includes recovering the wastewater from which oil has been removed in the aforementioned cross-flow sedimentation tank, cooling it, and using it again directly as cooling water, The cross-flow sedimentation tank is equipped with a partition weir, the partition weir being positioned within the cross-flow sedimentation tank such that its upper end protrudes above the water surface and its lower end is spaced apart from the bottom surface of the cross-flow sedimentation tank, and it forms a V-shape that closes diagonally to or along the flow direction of the cross-flow sedimentation tank, thereby damming the flow of the floating oil and allowing wastewater from which the oil has been separated to pass through the space between the lower end of the partition weir and the bottom surface of the cross-flow sedimentation tank. Operating procedure for direct cooling water systems.

2. The method for operating a direct cooling water system according to claim 1, wherein the oil separation accelerator is a cationic or amphoteric organic coagulant or polymer.

3. The method for operating a direct cooling water system according to claim 2, wherein the cationic organic coagulant or polymer is one or more organic coagulants or polymers selected from alkylamine / epichlorohydrin condensates, polyethyleneimine, alkylenedichloride / polyalkylene polyamine condensates, dicyandichloride / polyalkylene polyamine condensates, polydimethylaminoethyl methacrylate, and polydiallyldimethylammonium chloride.

4. The method for operating a direct cooling water system according to claim 2, wherein the amphoteric organic coagulant or polymer is one or more organic coagulants or polymers selected from copolymers of trialkylamine and acrylic acid and copolymers of diallyldimethylammonium chloride and acrylic acid.

5. The method for operating a direct cooling water system according to claim 1, comprising adding a cationic organic coagulant or polymer to the scale pit.

6. The method for operating a direct cooling water system according to claim 5, wherein the oil separation accelerator added to the scale sluice is an amphoteric organic coagulant or polymer.

7. A treatment facility for a direct cooling water system containing oil and metal scale, The path that forms the turbulent state from the scale sluice to the scale pit, An oil separation accelerator supply device for adding an oil separation accelerator to the aforementioned cooling water, It includes a transverse flow sedimentation tank located downstream of the scale pit to remove the separated floating oil, The aforementioned cross-flow sedimentation tank is equipped with a partition weir, The aforementioned partition weir is, With the upper end protruding above the water surface and the lower end spaced apart from the bottom of the horizontal flow sedimentation tank, the flow of the floating oil is dammed by the partition weir, and wastewater from which the oil has been separated can pass through the spaced portion between the lower end of the partition weir and the bottom of the horizontal flow sedimentation tank, A direct cooling water treatment facility is arranged within the transverse flow sedimentation tank in a V-shape that is oblique to or along the flow direction of the transverse flow sedimentation tank.

8. An oil separation accelerator for carrying out the direct cooling water system operation method described in any one of claims 1 to 6, The oil separation accelerator comprises a cationic or amphoteric organic coagulant or polymer.

9. The oil separation accelerator according to claim 8, wherein the cationic organic coagulant or polymer is one or more organic coagulants or polymers selected from alkylamine / epichlorohydrin condensates, polyethyleneimine, alkylenedichloride / polyalkylene polyamine condensates, dicyandichloride / polyalkylene polyamine condensates, polydimethylaminoethyl methacrylate, and polydiallyldimethylammonium chloride.

10. The oil separation accelerator according to claim 8, wherein the amphoteric organic coagulant or polymer is one or more organic coagulants or polymers selected from copolymers of trialkylamine and acrylic acid and copolymers of diallyldimethylammonium chloride and acrylic acid.

Images