JP7212506B2 - Method for treating oil-containing sludge and method for treating wastewater - Google Patents

Description

The present invention relates to a method for treating oily sludge and a method for treating wastewater.

In steelworks, the process of producing iron (pig iron) using sintered ore and coke as raw materials in a blast furnace (pig iron process) is carried out. process) is being carried out. In the steel manufacturing process, steel (molten steel) refined in a converter is continuously poured into a mold, cooled and solidified to make billets (continuous casting process). Various steel products are manufactured through a rolling process such as a cold rolling process.

In the steel manufacturing process described above, waste water is generated by using water to cool, clean, etc. the steel material in the manufacturing process and the equipment used in the manufacturing. For example, in the continuous casting process and hot rolling process, waste water (referred to as direct cooling waste water) is generated by the use of water sprayed on the surface of the steel material to cool the steel material during the manufacturing process. . In addition, in the cold rolling process, acid such as hydrochloric acid is used to wash off the scale (iron oxide) generated on the surface of the steel material in the previous hot rolling process, and waste water is generated.

The wastewater generated in the above steel manufacturing process includes scale peeled off from the surface of the steel material, oil such as lubricating oil and rolling oil used in equipment in each process such as rolls used in continuous casting and rolling, and rolls etc. Iron powder and the like generated by friction between equipment and steel materials can be included. Such wastewater is generally subjected to solid-liquid separation by sedimentation and filtration in order to reduce the volume and reduce the amount of waste generated at the wastewater treatment plant of steelworks. The treated water from which is removed may be recycled (see Patent Documents 1 and 2, for example). During this solid-liquid separation, sludge containing water, iron, and oil (hereinafter sometimes referred to as "oil-containing sludge") is generated.

Since oil-containing sludge contains oil, it is difficult to reuse it as it is as a raw material for ironmaking, and various treatment methods are used to treat it. In order to extract the iron in the oil-containing sludge and reuse it as a raw material for ironmaking, it is necessary to remove or separate the oil from the oil-containing sludge, and various methods for its treatment have been proposed (see, for example, Patent Documents 3 and 4). On the other hand, since the oil-containing sludge contains oil, it may be more difficult to separate the oil from the oil-containing sludge, for example, when the oil content is large, when it contains various types of oil, or depending on the type of oil. . Therefore, part of the oil-containing sludge is also disposed of as industrial waste.

Japanese Patent Application Laid-Open No. 2013-202500 WO2013/077977 JP 2005-230704 A JP 2007-260484 A

In general, oil-containing sludge is temporarily stored in tanks such as sedimentation tanks and thickening tanks in ironworks. When the oil-containing sludge is processed for disposal or for reuse as a raw material for steelmaking, the oil-containing sludge is removed from the above-mentioned tank by dredging using a shovel, pump, bucket, or the like. It is unloaded and loaded onto transport means such as conveyor belts and trucks for transport to a treatment facility. At this time, the oil-containing sludge often has a relatively high water content and is easy to flow (high fluidity), and further contains oil. is concerned about the outflow of Therefore, oil-containing sludge with high fluidity is preferably air-dried before being transported, but air-drying requires a large space. Therefore, oil-containing sludge may be subject to restrictions such as transportation amount and drying compared to sludge (raw material sludge) that can be used as a raw material for ironmaking as it is, such as sludge that does not contain oil.

Therefore, in view of the actual situation and problems described above, it is an object of the present invention to provide an oil-containing sludge treatment method capable of converting oil-containing sludge into a material to be easily transported.

The present invention provides sludge containing water, iron, and oil that is recovered from wastewater generated in the steel manufacturing process by solid-liquid separation. A method for treating oily sludge, comprising the steps of adding and mixing a water-soluble polymer containing structural units derived from at least one monomer derived from

ADVANTAGE OF THE INVENTION According to this invention, the processing method of the oil-containing sludge which can be made into the process material which can carry easily can be provided.

In Test Examples A1 to A5, photographs of the state immediately after mixing the oil-containing sludge and the water-soluble polymer and the state immediately after the test for confirming the properties of the obtained treated product are shown in the state of the oil-containing sludge before treatment. It is a chart showing in comparison with the photograph which photographed. Regarding the processed material obtained in Test Example B1, a photograph of the state immediately after the test for confirming the properties of the processed material, a photograph of the state after 4 days, and a photograph of the state of the oil-containing sludge before treatment. It is a chart showing a comparison with 2 is a chart showing comparison of photographs of the oil-containing sludge before treatment used in Test Example C and the treated products obtained in Test Examples C1 to C6 taken immediately after the test for confirming the properties.

Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. In this specification, the term "~" is used to include the numerical values before and after it as lower and upper limits.

<Method for treating oil-containing sludge>
In the oil-containing sludge treatment method of one embodiment of the present invention, sludge containing water, iron, and oil (oil-containing sludge) recovered from wastewater generated in the steel manufacturing process by solid-liquid separation is treated.

In general, iron ore, coal, coke, iron, and the like may be cited as main constituents of sludge deposited in water treatment pits in steel plants. This is a yard for storing raw materials for steelmaking in the open air at a steelworks; a factory that produces sintered ore and coke; a blast furnace that uses sintered ore and coke as raw materials to produce pig iron; This is because there may be factories that manufacture various steel products by refining at Specifically, in the yard, raw materials for steelmaking (iron ore and coal) piled open may flow out due to rainfall or water spraying to prevent dust. It is believed that sludge is produced as the main component. In the process of producing sintered ore (sintering plant), iron ore and limestone are sintered at high temperature to produce sintered ore, so sludge mainly composed of iron ore is generated in the water treatment pit there. it is conceivable that. In addition, in the process of producing coke (coke plant), coal is steamed at high temperature to produce coke, so it is thought that sludge mainly composed of coal and coke is generated in the water treatment pit there. Furthermore, pig iron is already produced in the steel manufacturing process (for example, billet mills, bar mills, hot rolling mills, cold rolling mills, plate mills, etc.) where pig iron is refined in a converter to produce various steel products. It is believed that iron-based sludge is produced in the water treatment pits there, since the steel produced through the poured converter process is used.

In the method of one embodiment of the present invention, oil-containing sludge recovered from wastewater generated in the steel manufacturing process by solid-liquid separation is treated. Unlike sludge containing iron ore, coal, or coke as the main solid content, this oil-containing sludge can usually contain iron as the main solid content.

There are no particular restrictions on the steelmaking process that produces wastewater from which the oil-containing sludge to be treated is recovered, as long as the process can produce wastewater. For example, a continuous casting process (hereinafter referred to as "continuous casting process"), a hot rolling process (hereinafter referred to as "hot rolling process"; the hot rolling process includes a plate manufacturing process, a long steel manufacturing process, etc.), and A cold rolling process (hereinafter referred to as "cold rolling process") and the like can be mentioned. The oil-containing sludge is preferably recovered from wastewater generated in continuous casting, hot rolling, or cold rolling. Oil-containing sludge recovered from one type of waste water or mixed waste water of two or more types of waste water generated in these processes may be treated.

Suitable specific examples of wastewater generated in the steel manufacturing process include wastewater derived from the water used to cool, wash, etc. the steel materials in the manufacturing process and the equipment used in the manufacturing process in the steel manufacturing process. be able to. For example, in a continuous casting process, a hot rolling process, and the like, waste water (direct cooling waste water) is generated by spraying water onto the surface of the steel material in order to cool the steel material in the manufacturing process. In the cold-rolling process, the steel material that has undergone the hot-rolling process (so-called hot-rolled coil) is rolled thinner at room temperature. Wastewater (washing wastewater) is generated when an acid such as hydrochloric acid is used to wash off substances. Furthermore, wastewater may also be generated from cooling and cleaning equipment in each step. Wastewater such as these contains scale (iron oxide) that has fallen off the surface of steel materials, oil such as lubricating oil used in equipment in each process such as rolls, and friction between equipment such as rolls and steel materials. Resulting iron powder and the like may be included. Oil-containing sludge to be treated can be recovered from such wastewater.

As described above, the moisture in the oil-containing sludge recovered from the wastewater generated in the steel manufacturing process is derived from the water used for cooling or washing the steel materials in the manufacturing process of the steel manufacturing process or the equipment used for the manufacture thereof. is preferably

The method of solid-liquid separation when oil-containing sludge is recovered from wastewater is not particularly limited. For example, coagulation/sedimentation treatment, membrane separation/filtration treatment, flotation treatment, centrifugation treatment, and the like can be mentioned. Oil-containing sludge recovered from wastewater by solid-liquid separation treatment of one or more of these methods is suitable. and oil-containing sludge is more preferred.

Preferable specific examples of oil-containing sludge recovered from wastewater generated in the steel manufacturing process include the following. Wastewater generated in the steel manufacturing process described above may flow down into the scale sluice (open trough) in the steel manufacturing facility and be sent to the water treatment facility through the scale sluice. In the water treatment facility, suspended solids (SS) containing iron powder, iron oxides, and the like in waste water are removed to obtain treated water that can be recycled. In water treatment facilities, for example, wastewater is sent from scale sluice to scale pits, flocculation/sedimentation tanks, filters, and the like. It is preferable to treat the SS-containing oil-containing sludge recovered from these water treatment facilities.

In addition, oil-containing sludge collected from water treatment facilities is temporarily stored in sedimentation ponds, lagoons, and thickeners before being sent to treatment facilities for waste treatment and treatment facilities for reuse as raw materials for steelmaking. It may be stored in a tank such as a tank. It is more preferable to treat the oil-containing sludge in these tanks. Furthermore, oil-containing sludge for disposal is more suitable for disposal because it is difficult to treat for reuse as a raw material for ironmaking due to the oil content in the oil-containing sludge.

Since oil-containing sludge is recovered from wastewater generated in the steel manufacturing process, it contains water, iron, and oil. From the viewpoint of oil-containing sludge suitable for treatment, the water content in the oil-containing sludge is preferably 30 to 90% by mass, preferably 30 to 80% by mass, based on the total mass of the oil-containing sludge. and more preferably 40 to 70% by mass. The oil content in the oil-containing sludge after drying (after water removal) is preferably 2 to 20% by mass, more preferably 4 to 15% by mass, based on the total dry mass of the oil-containing sludge. , 6 to 10% by mass. In addition, the content of SS containing iron in the oil-containing sludge after drying (after removing moisture) is preferably 30 to 90% by mass, preferably 40 to 80% by mass, based on the total dry mass of the oil-containing sludge. more preferably 50 to 70% by mass.

The iron contained in the oil-containing sludge includes metallic iron (M.Fe) derived from scrap iron and iron powder, ferrous oxide (FeO) derived from scale, and ferric oxide (Fe ₂ O ₃ ) etc. can be mentioned. One or more of these may be contained in the oil-containing sludge. The content of iron in the oil-containing sludge after drying (after removing water) is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, as the total amount of iron (T.Fe). , 40 to 60% by mass.

Examples of SS other than iron that may be contained in the oil-containing sludge include calcium, calcium oxide, silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide, manganese oxide, and sulfur. One or more of these may be contained in the oil-containing sludge.

The average particle size of SS such as iron contained in the oil-containing sludge is preferably 1 to 50 μm, more preferably 5 to 40 μm, even more preferably 8 to 30 μm. In the present specification, the average particle size of SS means the particle size (D50) at which cumulative 50% of the mass-based particle size distribution is measured using a laser diffraction scattering type particle size distribution analyzer.

In one embodiment of the oil-containing sludge treatment method of the present invention, the above-mentioned oil-containing sludge is derived from at least one monomer selected from the group consisting of (meth)acrylic acid and its salts, and (meth)acrylamide. A step of adding and mixing a water-soluble polymer containing structural units is included.

As used herein, the term "(meth)acrylic" is meant to include both terms of acrylic and methacrylic. "Water-soluble" in "water-soluble polymer" means that the solubility of the water-soluble polymer in 100 g of water at 25°C is 2 g or more. The term "water-soluble polymer" includes homopolymers (homopolymers) of one type of monomer and copolymers (copolymers) of two or more types of monomers. A "structural unit" means a monomer unit that constitutes a water-soluble polymer. The "structural unit derived from a monomer" includes, for example, a structural unit in which a polymerizable double bond (C=C) in a monomer is cleaved to form a single bond (-C-C-). be Moreover, below, (meth)acrylic acid and/or its salt may be described as "(meth)acrylic acid (salt)."

Examples of (meth)acrylic acid salts that can constitute structural units in the water-soluble polymer include alkali metal salts, ammonium salts, and amine salts. Among these, alkali metal salts and ammonium salts are preferred. Preferred (meth)acrylates include sodium (meth)acrylate, lithium (meth)acrylate, potassium (meth)acrylate, and ammonium (meth)acrylate. Among these, sodium (meth)acrylate is more preferred, and sodium acrylate is even more preferred.

The water-soluble polymer is derived from one or two or more monomers substantially selected from the group consisting of (meth)acrylic acid and its salts, and (meth)acrylamide, as monomers constituting it. It may be composed only of structural units that The water-soluble polymer may also contain structural units derived from monomers other than (meth)acrylic acid and its salts and (meth)acrylamide. Other monomers include, for example, unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid and salts thereof; carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; styrene and α-methyl aromatic vinyl compounds such as styrene; vinylsulfonic acid, styrenesulfonic acid, and acrylamidoalkanesulfonic acids such as 2-acryloylamino-2-methylpropanesulfonic acid, and unsaturated sulfonic acids such as salts thereof; ) methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic esters such as 2-ethylhexyl (meth) acrylate; vinyl acetate; acrylonitrile; can.

Examples of water-soluble polymers include polyacrylic acid (salt)-based polymers, polymethacrylic acid (salt)-based polymers, polyacrylamide-based polymers, polymethacrylamide-based polymers, and (meth)acrylic acid (salt)- (Meth)acrylamide copolymers and the like can be mentioned. These may also contain structural units derived from monomers other than (meth)acrylic acid and its salts and (meth)acrylamide.

The weight average molecular weight (Mw) of the water-soluble polymer is preferably 5 million to 30 million, more preferably 10 million to 25 million. This weight average molecular weight can be measured by gel permeation chromatography (GPC).

The above-mentioned water-soluble polymer containing structural units derived from (meth)acrylic acid (salt) and/or (meth)acrylamide is added to the above-mentioned oil-containing sludge, and when mixed, suspended matter in the oil-containing sludge can adsorb to and bind suspended matter together into coarse particles. At that time, water in the oil-containing sludge is trapped in the gaps associated with the binding of suspended solids in the coarse particles, so that the fluidity of the oil-containing sludge is reduced and an easy-to-transport treated material (sludge-treated material) is obtained. can be done.

From the viewpoint of enhancing the above-described action and effect, it is preferable to use a (meth)acrylic acid (salt)-(meth)acrylamide copolymer as the water-soluble polymer. The (meth)acrylic acid (salt)-(meth)acrylamide copolymer contains a structural unit derived from at least one of (meth)acrylic acid and its salt, and a structural unit derived from (meth)acrylamide. It is a copolymer. Among these copolymers, a (meth)acrylic acid (salt)-acrylamide copolymer is more preferable, an acrylic acid (salt)-acrylamide copolymer is more preferable, and a sodium acrylate-acrylamide copolymer is particularly preferable. .

When the above-mentioned (meth)acrylic acid (salt)-acrylamide copolymer is added to the above-mentioned oil-containing sludge and mixed, the polyacrylamide portion in the copolymer becomes part of the free water contained in the oil-containing sludge. It is thought that an adhesive cross-linking action based on the adsorption of the polyacrylamide moiety occurs in the suspended matter in the oil-containing sludge. Suspended substances become coarse particles due to this adhesion cross-linking action, and most of the free water in the oil-containing sludge is captured in the gaps between them. , it is thought that the treated product has an appearance as if the moisture content has decreased.

As described above, water-soluble polymers adsorb to suspended solids in oil-containing sludge due to their actions and effects, unlike water-absorbing polymers that have the function of absorbing water. It can be made into particles and moisture can be trapped in the interstices created by the bonding. The formation of gaps in the coarse particles increases the surface area of the particles, thereby promoting drying by exposure to the sun and ventilation.

The form of the water-soluble polymer to be added to the oil-containing sludge is not particularly limited, and examples thereof include a powder form and a liquid form such as an aqueous solution and an emulsion. The water-soluble polymer can be used without increasing the water content of the oil-containing sludge, and can be dissolved in the water in the oil-containing sludge to quickly mix with the water-soluble polymer. It is preferably in the form of an emulsion dispersed in a dispersion medium as . In this case, the emulsion-like water-soluble polymer is more preferably a water-in-oil (W/O) emulsion, in which the water-soluble polymer is dispersed in hydrorefined light distillate oil (petroleum). More preferably, it is in emulsion form. Since the oil in the water-in-oil emulsion is easily mixed with the oil in the oil-containing sludge, it is thought that the water-soluble polymer can be quickly mixed with the oil-containing sludge. On the other hand, the powdery water-soluble polymer is also advantageous from the viewpoint that it can be used without increasing the oil content of the oil-containing sludge.

On the other hand, from the viewpoint that the water-soluble polymer added to the oil-containing sludge is more likely to reach the entire oil-containing sludge, the content of the water-soluble polymer is 0 as the form of the water-soluble polymer when it is added to the oil-containing sludge. .1 to 2% by weight in the form of dilute liquids is preferred. The content of the water-soluble polymer in the dilute liquid is preferably 0.2% by mass or more, preferably 1.8% by mass or less, and preferably 1.6% by mass or less. More preferably, it is 1% by mass or less. By using a dilute liquid, even if the amount of the water-soluble polymer added to the oil-containing sludge is small, the effect of making the oil-containing sludge into a material to be easily transported can be exhibited.

Suitable forms of the dilute liquid include an oil-in-water (O/W) emulsion; a dispersion such as an aqueous dispersion; and a solution such as an aqueous solution. Among these, from the viewpoint of ease of production and the viewpoint that the water-soluble polymer in the dilute liquid is more likely to reach the entire oil-containing sludge, the dilute liquid is an aqueous solution containing the water-soluble polymer as a solute, or a water-soluble More preferably, it is in the form of an oil-in-water emulsion containing a polymer as a dispersion medium.

As the diluted liquid, for example, a dispersion containing 0.1 to 2% by mass of the water-soluble polymer and a dispersion medium (diluted liquid in the form of a dispersion) can be used from the time of production of the water-soluble polymer. Further, as the dilute liquid, for example, a dispersion containing a water-soluble polymer (for example, 10 to 50% by mass) and a dispersion medium (for example, a liquid product containing a commercially available water-soluble polymer) is mixed with a water-soluble polymer. It is also possible to use a diluted solution obtained by diluting with a liquid medium in an amount such that the concentration of is 0.1 to 2% by mass. Furthermore, as the dilute liquid, for example, a solution obtained by dissolving 0.1 to 2% by mass of a commercially available powdery water-soluble polymer in a solvent (solution dilute liquid) can also be used. The dilute liquid contains at least one liquid component such as the water-soluble polymer and the above-described dispersion medium, solvent, and liquid medium that can be used for dilution, and also contains unavoidable impurities (for example, residual amount of monomer, etc.).

A more preferable diluent is a dispersion containing a water-soluble polymer (eg, 10 to 50% by mass) and a dispersion medium (eg, the above-mentioned commercially available liquid product), and a concentration of the water-soluble polymer is 0.1 to 0.1. A dilute solution obtained by diluting with water in an amount of 2% by mass and stirring can be used. Examples of the dispersion medium in the dispersion before dilution of the dilute solution include water (including aqueous solutions containing salts such as alkali metal salts and ammonium salts) and hydrorefined light distillate oil (petroleum). be able to.

A more preferred specific example of the dilute liquid as described above is a water-in-oil (W/O ) type emulsion is diluted with water in such an amount that the concentration of the water-soluble polymer is 0.1 to 2% by mass, and the diluted solution is obtained by stirring. In this diluted liquid, the continuous phase is phase-inverted from oil to water by being diluted with a large amount of water compared to the dispersion medium, the water-soluble polymer is dissolved in the continuous phase (water), and A dilute liquid in the form of an oil-in-water (O/W) emulsion in which the oil that was the continuous phase has become the dispersoid can be used.

Further, as a more preferable specific example of the dilute liquid as described above, an aqueous dispersion (aqueous Dispersion) may be diluted with water in an amount such that the concentration of the water-soluble polymer is 0.1 to 2% by mass, and stirred to obtain a diluted solution. This diluted liquid is diluted with a large amount of water compared to the dispersion medium, and the water content in the aqueous solution, which is the continuous phase, increases, so that the water-soluble polymer is dissolved in the water (aqueous solution). Dilute solutions in the form of aqueous solutions can be used. Furthermore, as a preferred specific example of the dilute liquid, an aqueous dilute liquid obtained by dissolving 0.1 to 2% by mass of a powdery water-soluble polymer in water can also be mentioned.

The liquid component in the dilute liquid may contain liquid components other than the water and hydrorefined light distillate oil (petroleum) described above. Other liquid components include, for example, water-soluble organic solvents such as alcohols, polyhydric alcohols, polyglycols, and glycol ethers, and one or more of them can be used.

The amount of the water-soluble polymer added to the oil-containing sludge is not particularly limited, and can be adjusted according to the water content and state of the oil-containing sludge when adding the water-soluble polymer. For example, it is preferable to add 0.001 to 1 part by mass, more preferably 0.01 to 1 part by mass of the water-soluble polymer per 100 parts by mass of the oil-containing sludge.

When the water-soluble polymer is used in the form of a powder or a water-in-oil emulsion as described above, the oil-containing sludge more suitable for the treatment of the present method contains 0.00 of the water-soluble polymer per 100 parts by weight of the oil-containing sludge. It is preferable to add 01 to 1 part by mass. In this case, the amount of the water-soluble polymer added is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and 0.05 parts by mass per 100 parts by mass of the oil-containing sludge. It is more preferable that it is above. In this case, the amount of the water-soluble polymer added is preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, and even more preferably 0.2 parts by mass or less. . The amount of the water-soluble polymer added in this case can be appropriately changed according to the amount of water in the oil-containing sludge.

Further, as described above, when the water-soluble polymer is used in the form of a dilute solution having a water-soluble polymer content of 0.1 to 2% by mass, the amount of the water-soluble polymer added to the oil-containing sludge is increased. It can be small. When the diluted liquid is the aforementioned aqueous solution or the aforementioned oil-in-water emulsion, it is preferable to add 0.001 to 0.5 parts by mass of the water-soluble polymer per 100 parts by mass of the oil-containing sludge. In this case, the amount of the water-soluble polymer added is preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, and more preferably 0.01 parts by mass per 100 parts by mass of the oil-containing sludge. It is more preferable that it is above. In this case, the amount of the water-soluble polymer added is preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, and preferably 0.05 parts by mass or less. More preferred. The amount of the water-soluble polymer added in this case can be appropriately changed according to the amount of water in the oil-containing sludge.

The method of mixing the water-soluble polymer with the oil-containing sludge is not particularly limited, and examples thereof include shovels, various kneaders, mixers, stirrers, etc. (hereinafter these may be referred to as "kneaders, etc."). ) can be used to mix the oil-containing sludge with the water-soluble polymer. The mixing time can be, for example, about 0.5 to 10 minutes.

The water-soluble polymer is preferably added to the oil-containing sludge stored in the above-described temporary storage tank (sedimentation tank, lagoon, thickening tank, etc.). Specifically, it is possible to employ a method in which the water-soluble polymer is directly added to the tank in which the oil-containing sludge is stored, and the oil-containing sludge and the water-soluble polymer are mixed with a shovel, bucket, or the like in the tank. . This method has the advantage that the same shovel, bucket, or the like can be used to mix the oil-containing sludge and the water-soluble polymer, and to take out the treated material from the tank in which the oil-containing sludge is stored. By this method, after obtaining the treated material in which the fluidity of the oil-containing sludge has decreased, the treated material can be taken out with a shovel and easily transported to a treatment facility or the like by means of transportation such as a belt conveyor or truck.

As another method, the oil-containing sludge is taken out from the above-mentioned tank, put into a kneader or the like installed in the tank or its vicinity, and the water-soluble polymer is put into the kneader or the like containing the oil-containing sludge and kneaded. A method of mixing the oil-containing sludge and the water-soluble polymer in a machine or the like can be adopted. This method has the advantage that the oil-containing sludge and the water-soluble polymer can be mixed more efficiently than the above-mentioned mixing using a shovel, and a treated product with reduced fluidity can be stably obtained. . By this method, after obtaining a processed material with reduced fluidity of oil-containing sludge, the processed material is transferred from the kneader to a belt conveyor, and in some cases, using a transportation means such as a truck, etc., easily transported to a processing facility. can be transported to

By using a kneader or the like, there is also the advantage that the oil-containing sludge and the water-soluble polymer can be mixed in a short time. The mixing time of the oil-containing sludge and the water-soluble polymer using a kneader or the like can be 300 seconds or less (eg, 10 to 300 seconds), more preferably 120 seconds or less (eg, 10 to 120 seconds). more preferably 90 seconds or less (10 to 90 seconds).

In the method of one embodiment of the present invention, by the step of adding the water-soluble polymer to the oil-containing sludge and mixing, it is possible to obtain an easy-to-transport material in which the fluidity of the oil-containing sludge is reduced. . It is preferable to obtain a treated product in which the oil-containing sludge is formed in the form of granules or nodules by adding the water-soluble polymer to the oil-containing sludge and mixing them. More specifically, in the step of adding the water-soluble polymer to the oil-containing sludge and mixing, the above-mentioned oil-containing sludge is obtained by the test (fluidity confirmation test) described below, and the x value is 80 to 85 mm (more preferably 80 to 83 mm) and a y value of 25 to 50 mm (more preferably 30 to 50 mm, still more preferably 40 to 50 mm). In this test, a mixture (treated material) of oil-containing sludge and water-soluble polymer is placed in a truncated conical container having an inner diameter of 80 mm at the top opening, 50 mm at the inner diameter of the bottom at the bottom, and 90 mm in height. After putting it in, put a flat plate on top of it (the upper end opening) and cover it, turn it upside down, put the flat plate side on a horizontal test table, and then pull up the above container. be. At this time, the horizontal length (radial direction of the container) of the processed material remaining on the test table (flat plate) can be measured as the x value, and the height of the processed material can be measured as the y value. The lower the fluidity of the sample (processed material) used in the test, the higher the y value at the maximum of 50 mm and the smaller the x value at the minimum of 80 mm. The above test is a test based on the concrete slump test method defined in JIS A1101.

In addition, the above test is conducted in the same manner as above, except that the mixture (processed product) of oil-containing sludge and water-soluble polymer is placed smoothly (up to a height of 90 mm) in the truncated cone-shaped container. , the above step is preferably the next step. That is, in the step of adding the water-soluble polymer to the oil-containing sludge and mixing, the above-mentioned oil-containing sludge obtained by the above test has an x value of 80 to 100 mm (more preferably 80 to 95 mm, more preferably 80 to 90 mm). ), and a y value of 50 to 90 mm (more preferably 55 to 90 mm, still more preferably 80 to 90 mm).

The method of transporting the obtained treated oil-containing sludge is not particularly limited, but it is preferable to use a transport means such as a belt conveyor or a truck. Since the treated material has lower fluidity than the oil-containing sludge before treatment, it is difficult for the oil-containing sludge (treated material) and the oil contained therein to flow out during transportation by a belt conveyor, truck, or the like. Therefore, the oil-containing sludge (processed material) can be easily transported without being subject to large restrictions on the transport amount, transport speed, and the like.

<Wastewater treatment method>
The oil-containing sludge treatment method of one embodiment of the present invention described above may be incorporated as part of a wastewater treatment method. Such a wastewater treatment method includes a step of solid-liquid separation of wastewater generated in the steel manufacturing process to recover sludge containing water, iron, and oil, and adding the above-mentioned water-soluble polymer to the recovered sludge. and mixing. In each of these steps, the same technique as described in the oil-containing sludge treatment method can be used.

In the oil-containing sludge treatment method described in detail above, the water-soluble polymer is added to the oil-containing sludge, and the water-soluble polymer is added to the particles in the oil-containing sludge that are derived from the SS in the waste water and mixed. Coarse particles can be formed by adsorbing and binding particles (SS) together. At that time, the particles (SS) in the coarse particles are bound to each other to form gaps, and water in the oil-containing sludge can be trapped in the gaps. As a result, it is possible to obtain an easy-to-transport processed material in which the fluidity of the oil-containing sludge is lowered. This processed material can be easily transported to a processing facility for waste treatment or a processing facility for reuse as a raw material for ironmaking by means of transportation such as a belt conveyor or truck. In this way, the oil-containing sludge (treated material) treated by the above-described treatment method may then be treated for disposal or reused as a raw material for iron making. The treatment method may be a method for reforming oil-containing sludge or a pretreatment method.

As described above, the method of one embodiment of the present invention can take the following configurations.
[1] Selected from the group consisting of (meth)acrylic acid and its salts, and (meth)acrylamide for sludge containing water, iron, and oil recovered from wastewater generated in the steel manufacturing process by solid-liquid separation A method for treating oil-containing sludge, comprising the steps of adding and mixing a water-soluble polymer containing structural units derived from at least one monomer.
[2] The method for treating oil-containing sludge according to [1], wherein the water-soluble polymer is added to the sludge in the form of powder.
[3] The oil-containing sludge treatment method according to [1], wherein the water-soluble polymer is added to the sludge in the form of an emulsion.
[4] The oil-containing sludge according to [1], wherein the water-soluble polymer is added to the sludge in the form of a dilute liquid in which the content of the water-soluble polymer is 0.1 to 2% by mass. Processing method.
[5] Treatment of oil-containing sludge according to [4], wherein the diluted liquid is an aqueous solution containing the water-soluble polymer as a solute, or an oil-in-water emulsion containing the water-soluble polymer as a dispersion medium. Method.
[6] The method for treating oil-containing sludge according to any one of [1] to [5], wherein 0.001 to 1 part by mass of the water-soluble polymer is added per 100 parts by mass of the sludge.
[7] The water-soluble polymer comprises a structural unit derived from at least one of (meth)acrylic acid and a salt thereof, and a structural unit derived from (meth)acrylamide, (meth)acrylic acid (salt) - The method for treating oil-containing sludge according to any one of the above [1] to [6], which is a (meth)acrylamide copolymer.
[8] Treatment of oil-containing sludge according to any one of [1] to [7], wherein the wastewater is wastewater generated in a continuous casting process, a hot rolling process, or a cold rolling process in the steel manufacturing process. Method.
[9] A step of solid-liquid separation of wastewater generated in the steel manufacturing process to recover sludge containing water, iron, and oil, and adding (meth)acrylic acid and its salts to the recovered sludge, and ( A method for treating wastewater, comprising the steps of adding and mixing a water-soluble polymer containing a structural unit derived from at least one monomer selected from the group consisting of meth)acrylamide.
[10] A step of solid-liquid separation of wastewater generated in the steel manufacturing process to recover sludge containing water, iron, and oil, and the recovered sludge is any of the above [1] to [8] A method for treating wastewater, comprising the step of treating with the treatment method according to 1.

Hereinafter, the present invention will be described in more detail with reference to test examples, but the present invention is not limited to the following test examples.

<Test example A>
In Test Example A, a water-soluble polymer containing structural units derived from (meth)acrylic acid (salt) and/or (meth)acrylamide is used in oil-containing sludge collected from a sedimentation pond as a temporary storage site in a steelworks. A test was conducted to confirm the effect of adding and mixing.

As the oil-containing sludge to be treated, oil-containing sludge recovered by solid-liquid separation such as sedimentation separation was used from the wastewater generated in the hot rolling process, which is a kind of steel manufacturing process, in steelworks. This oil-containing sludge is recovered from wastewater including direct cooling wastewater and washing wastewater derived from the water used for cooling, washing, etc. of the steel material in the manufacturing process and equipment used in manufacturing in the hot rolling process. It is.

The mass of the oil-containing sludge immediately after collection (mass before drying) and the mass of the oil-containing sludge after drying (mass after drying) are measured, and the water content (moisture content) of the oil-containing sludge is calculated as follows: Moisture content (%) = [drying Pre-drying mass]/pre-drying mass x 100. As a result, the water content (moisture content) of the oil-containing sludge was 48.2% by mass. The drying conditions for the oil-containing sludge are conditions in which water is removed by placing the oil-containing sludge in a constant temperature bath at 110±5° C. for 24 hours.

As a reference, the oil-containing sludge after drying was subjected to composition analysis using an energy dispersive X-ray analysis (EDX analysis) device (trade name “Quantax 70”, manufactured by Bruker). As a result, for the oil-containing sludge after drying, the iron content (total amount of Fe (T.Fe)) was 65% by mass, metallic iron (M.Fe) was 1.0% by mass, and ferrous oxide (FeO) was 40% by mass. %, and ferric oxide (Fe ₂ O ₃ ) was detected as a value of 42% by mass (these values include cases where these components are detected in duplicate). The oil content in the dried oil-containing sludge measured by the Soxhlet extraction method using hexane as a solvent was 8% by mass. The average particle size of SS was 22 μm as a result of measurement using a laser diffraction scattering type particle size distribution analyzer (trade name “LMS-30” manufactured by Seishin Enterprise Co., Ltd.).

(Test example A1)
The collected oil-containing sludge was placed in a plastic cup, and 0.04 parts by mass of the water-soluble polymer emulsion was added to 100 parts by mass of the oil-containing sludge, and mixed with a spatula for 30 seconds. As the water-soluble polymer emulsion, an anionic W/O type emulsion (trade name “NS Dry-322L” manufactured by Nippon Steel & Sumikin Kankyo Co., Ltd.; acrylic of sodium acid-acrylamide copolymer and hydrorefined light fractions (petroleum)) were used. Thus, a treated oil-containing sludge according to Test Example A1 was obtained.

(Test example A2)
A treated oil-containing sludge according to Test Example A2 was obtained in the same manner as in Test Example A1, except that the amount of the water-soluble polymer added was changed to 0.12 parts by mass per 100 parts by mass of the oil-containing sludge. .

(Test example A3)
A treated oil-containing sludge according to Test Example A3 was obtained in the same manner as in Test Example A1, except that the amount of the water-soluble polymer added was changed to 0.2 parts by mass per 100 parts by mass of the oil-containing sludge. .

(Test example A4)
Instead of the water-soluble polymer emulsion used in Test Example A1, a powdered water-soluble polymer was used, and the amount added as the water-soluble polymer was set to 0.05 parts by mass per 100 parts by mass of the oil-containing sludge. Except for this, a treated oil-containing sludge according to Test Example A4 was obtained in the same manner as in Test Example A1. In Test Example A4, a powdery sodium acrylate-acrylamide copolymer (trade name “NS Dry-924S”, manufactured by Nippon Steel & Sumikin Kankyo Co., Ltd.) was used as the water-soluble polymer.

(Test example A5)
A treated oil-containing sludge was obtained in the same manner as in Test Example A4, except that the amount of the water-soluble polymer added in Test Example A4 was changed to 0.1 parts by mass per 100 parts by mass of oil-containing sludge. rice field.

(Fluidity confirmation test)
A test was conducted to confirm the fluidity of the processed products obtained in Test Examples A1 to A5. Specifically, in each test example, a mixture of oil-containing sludge and a water-soluble polymer ( The material to be treated) was placed in the container up to a height of 50 mm, and a flat plate was placed thereon (the upper end opening) to cover it. The upper end opening of the plastic cup was turned upside down with the flat plate covered, and the flat plate side was placed on a horizontal test table, and the plastic cup was pulled upward. Then, the y value (mm) and the x value (mm) were measured for the processed material remaining on the test table (flat plate). The y value represents the height of the treatment remaining on the test stand after the plastic cup was pulled out (vertical height of the test stand), and the x value represents the length of the treatment (horizontal extension of the test stand). length). Since the shape can be maintained as the processed material is formed in a solid state such as a granule or nodule shape, the y value takes a high value (a value closer to 50 mm), and the x value has a smaller value ( value closer to 80 mm). In addition, in each test example, all the tests were performed under the same conditions for relative evaluation. For comparison, a similar test was also conducted on oil-containing sludge before treatment as a blank. Table 1 shows the results of the test.

(Measurement of moisture content)
The oil-containing sludge before treatment and the treated products obtained in Test Examples A1 to A5 were measured for moisture content after 24 hours and 48 hours. Table 1 shows the results.

(State of processed material)
In each test example, a photograph of the state immediately after mixing the oil-containing sludge and the water-soluble polymer (hereinafter referred to as “state 1”) and the state placed on the test table during the fluidity confirmation test Photographs taken from the upper surface side and the side surface side of the treated material (hereinafter referred to as "state 2") are shown in FIG. 1 in the form of a comparison table. FIG. 1 also shows, as a blank, photographs of oil-impregnated sludge before treatment corresponding to states 1 and 2 above.

From the results of Test Examples A1 to A5 shown in Table 1 and FIG. 1, by adding and mixing a water-soluble polymer containing structural units derived from sodium acrylate and acrylamide to the oil-containing sludge, the apparent water content increased. It was confirmed that a crumb-like or nodule-like processed material with a reduced appearance was obtained. In addition, compared to the oil-containing sludge before treatment, this treated material has a higher y value and a lower x value in the fluidity confirmation test, confirming that the fluidity has decreased, making it easy to transport. was found to be

In addition, the oil-containing sludge to be treated in Test Examples A1 to A5 was changed to oil-containing sludge collected by solid-liquid separation from the wastewater generated in each process of continuous casting process, plate process, bar steel process, and cold rolling process. Therefore, tests similar to those of Test Examples A1 to A5 were also conducted. As a result, it was confirmed that results with the same tendencies as in Test Examples A1 to A5 were obtained for each oil-containing sludge.

<Test example B>
In Test Example B, a test was conducted assuming a case where the method for treating oil-containing sludge according to one embodiment of the present invention is actually performed on site.

First, oil-containing sludge stored in a sedimentation pond as a temporary storage site in a steelworks was treated. This oil-containing sludge, like the oil-containing sludge to be treated in Test Example A, was recovered from the wastewater generated in the hot rolling process in a steel mill by solid-liquid separation such as sedimentation. The wastewater from which this oil-containing sludge is recovered includes direct cooling wastewater and washing wastewater, etc. derived from the water used for cooling and washing the steel materials in the manufacturing process and the equipment used for manufacturing in the hot rolling process. Waste water. The water content of the oil-containing sludge was determined in the same manner as the calculation method described in Test Example A. As a result, the water content (water content) of the oil-containing sludge was 35.0% by mass.

In addition, the oil content in the dried oil-containing sludge measured by the Soxhlet extraction method in the same manner as the analysis method described in Test Example A was 3.2% by mass.

(Test example B1)
The oil-containing sludge was taken out from the sedimentation tank with a shovel, and 500 kg of the oil-containing sludge was put into a kneader installed in the sedimentation tank. Further, 400 g of the water-soluble polymer emulsion used in Test Example A1 was put into the kneader. Thus, in Test Example B1, 0.08 parts by mass of the water-soluble polymer was added to 100 parts by mass of the oil-containing sludge. Then, the oil-containing sludge and the water-soluble polymer were mixed for 60 seconds using a kneader, which is a recycling plant used for the purpose of effective utilization of wastes and by-products and recovery of valuable resources. After stopping the mixing, the mixture (processed material) of oil-containing sludge and water-soluble polymer is discharged from the discharge port provided at the bottom of the kneader. The material was transferred. Compared to the oil-containing sludge before treatment, this treated material appears to be in a hardened state with a lower apparent water content, and is easy to transport without falling off the belt conveyor. rice field.

The oil-containing sludge before treatment and its treated material were collected, and using them as samples, a fluidity confirmation test and a water content measurement were performed. In the fluidity confirmation test in Test Example B, the sample was filled into a vinyl chloride pipe (height 10 cm, nominal diameter 40 A) placed on the test table by leveling, and then the vinyl chloride pipe was pulled out, and the vinyl chloride pipe was pulled out. The y-value and x-value of the sample after being drawn were measured. The moisture content was measured every 0 to 4 days after the passage of time. These results are shown in Table 2.

In addition, for each sample of the oil-containing sludge before treatment and the treated product, the state immediately after the fluidity confirmation test (hereinafter referred to as “state 3”) was taken from the side and top sides, and after 4 days A photograph taken from the top side of the state (hereinafter referred to as "state 4") is shown in FIG. 2 in the form of a comparison table.

As shown in Table 2 and FIG. 2, the treated material obtained in Test Example B1 has a higher y value and a lower x value than the oil-containing sludge before treatment, indicating that the fluidity is lowered. It was confirmed that it was a crumb-like or nodule-like treated material that was easy to transport. In addition, it was confirmed that the treated material obtained in Test Example B1 drained water faster than the oil-containing sludge before treatment, and drying was accelerated.

<Test example C>
In Test Example C, as in Test Example A, a structural unit derived from (meth)acrylic acid (salt) and/or (meth)acrylamide was added to the oil-containing sludge collected from a sedimentation tank as a temporary storage site in a steelworks. A test was performed to confirm the effect of adding and mixing a water-soluble polymer containing.

The oil-containing sludge to be treated is sludge containing water, iron, and oil, which is collected by solid-liquid separation such as sedimentation separation from the wastewater generated in the continuous casting process, which is a type of steel manufacturing process, at steelworks. was used. This oil-containing sludge is recovered from waste water, including direct cooling waste water and washing waste water, etc., derived from the water used for cooling and washing the steel materials in the manufacturing process and the equipment used in the manufacturing process in the continuous casting process. It is. The water content of this oil-containing sludge was determined in the same manner as the calculation method described in Test Example A, and the water content (water content) of the oil-containing sludge was 57.5% by mass. In addition, the oil content in the dried oil-containing sludge measured by the Soxhlet extraction method in the same manner as the analysis method described in Test Example A was 10.1% by mass. Furthermore, the oil-containing sludge after drying was analyzed by the same analysis method as described in Test Example A. As a result, the iron content in the oil-containing sludge after drying was 42.2% by mass as the total amount of iron. there were.

(Test example C1)
300 g of the collected oil-containing sludge was placed in a plastic cup. As a liquid to be added to the oil-containing sludge (addition liquid), 0.3 g of an undiluted aqueous dispersion product containing a water-soluble polymer was added thereto and mixed with a spatula for 10 seconds. The aqueous dispersion product includes an aqueous dispersion containing 20% by mass of sodium acrylate-acrylamide copolymer (trade name “NS Dry-709L” manufactured by Nippon Steel & Sumikin Kankyo Co., Ltd.; sodium acrylate-acrylamide copolymer and Ammonium sulfate aqueous solution is used as a component.) was used. In this way, 0.1 parts by mass of the additive liquid (that is, 0.02 parts by mass as a sodium acrylate-acrylamide copolymer, which is a water-soluble polymer) was added and mixed per 100 parts by mass of the oil-containing sludge. Thus, a treated oil-containing sludge was obtained.

(Test example C2)
In Test Example C2, a treated oil-containing sludge was obtained in the same procedure and method as in Test Example C1, except that the additive liquid used and its amount were changed as compared with Test Example C1. Specifically, in Test Example C2, as the additive liquid to the oil-containing sludge, a dilute solution obtained by diluting the aqueous dispersion product used in Test Example C1 20 times with water (therefore, the water-soluble polymer in the dilute solution ( The content of sodium acrylate-acrylamide copolymer) was 1% by mass) was used. This diluted liquid (additive liquid) is diluted with a large amount of water compared to the dispersion medium in the original aqueous dispersion, and the water content in the aqueous solution, which is the continuous phase, is increased. It is a dilute aqueous solution in which a water-soluble polymer is dissolved in In Test Example C2, the amount of the dilute liquid added was set to 2 parts by mass with respect to 100 parts by mass of the oil-containing sludge. In this way, 2 parts by mass of the additive liquid (that is, 0.02 parts by mass as a sodium acrylate-acrylamide copolymer, which is a water-soluble polymer) was added and mixed per 100 parts by mass of the oil-containing sludge. , to obtain a treated oil-containing sludge.

(Test example C3)
In Test Example C3, 0.15 g of the undiluted aqueous dispersion product used in Test Example C1 was added to 300 g of the oil-containing sludge as an additive to the oil-containing sludge, and mixed with a spatula for 30 seconds. obtained a treated oil-containing sludge in the same procedure and method as in Test Example C1. In this way, 0.05 parts by mass of the additive liquid (that is, 0.01 parts by mass as a sodium acrylate-acrylamide copolymer, which is a water-soluble polymer) was added and mixed per 100 parts by mass of the oil-containing sludge. Thus, a treated oil-containing sludge was obtained.

(Test example C4)
In Test Example C4, a treated oil-containing sludge was obtained in the same procedure and method as in Test Example C1, except that the additive liquid used and its amount were changed as compared with Test Example C1. Specifically, in Test Example C4, the same diluted liquid as that used in Test Example C2 was used as the additive liquid to the oil-containing sludge, and the amount of this diluted liquid added was 1 mass per 100 parts by mass of the oil-containing sludge. part. In this way, 1 part by mass of the additive liquid (that is, 0.01 part by mass as a sodium acrylate-acrylamide copolymer, which is a water-soluble polymer) was added and mixed per 100 parts by mass of the oil-containing sludge. , to obtain a treated oil-containing sludge.

(Test example C5)
In Test Example C5, a treated oil-containing sludge was obtained in the same procedure and method as in Test Example C1, except that the additive liquid used and its amount were changed as compared with Test Example C1. Specifically, in Test Example C5, an anionic W/O type emulsion (trade name “NS Dry-322L ”, manufactured by Nippon Steel & Sumikin Kankyo Co., Ltd.; sodium acrylate-acrylamide copolymer and hydrorefined light fraction (petroleum) as components). 0.15 g was added. In this way, 0.05 parts by mass of the stock solution (additive solution) (that is, 0.02 parts by mass as sodium acrylate-acrylamide copolymer, which is a water-soluble polymer) was added per 100 parts by mass of oil-containing sludge. , to obtain a treated oil-containing sludge.

(Test example C6)
In Test Example C6, a treated oil-containing sludge was obtained in the same procedure and method as in Test Example C1, except that the additive liquid used and its amount were changed as compared with Test Example C1. Specifically, in Test Example C6, as the additive liquid to the oil-containing sludge, a dilute solution obtained by diluting the W/O emulsion product used in Test Example C5 100 times with water (therefore, the water-soluble The content of the coalescence (sodium acrylate-acrylamide copolymer) is 0.4% by mass) was used. This dilute liquid (additive liquid) is diluted with a large amount of water compared to the dispersion medium in the original W/O emulsion, so that the continuous phase changes from oil to water, and the continuous phase (water) It is an oil-in-water emulsion dilute liquid in which a water-soluble polymer is dissolved in the liquid, and the oil, which was a continuous phase, has become a dispersoid. In Test Example C6, the amount of the dilute solution added was 5 parts by mass with respect to 100 parts by mass of the oil-containing sludge. In this way, 5 parts by mass of the additive liquid (that is, 0.02 parts by mass as a sodium acrylate-acrylamide copolymer, which is a water-soluble polymer) was added and mixed per 100 parts by mass of the oil-containing sludge. , to obtain a treated oil-containing sludge.

(Fluidity confirmation test)
A fluidity test was conducted on the processed materials obtained in Test Examples C1 to C6. Specifically, in each test example, a mixture of oil-containing sludge and a water-soluble polymer ( The material to be treated) was put into the bowl (up to a height of 90 mm), and a flat plate was placed on top of it (upper end opening) to cover it. The upper end opening of the plastic cup was turned upside down with the flat plate covered, and the flat plate side was placed on a horizontal test table, and the plastic cup was pulled upward. Then, the y value (mm) and the x value (mm) were measured in the same manner as described above for the processed material remaining on the test table (flat plate). Since the shape can be maintained as the processed material is formed in a solid state such as a granule or nodule shape, the y value takes a high value (a value closer to 90 mm) and the x value has a small value ( value closer to 80 mm). In addition, in each test example, all the tests were performed under the same conditions for relative evaluation. For comparison, a similar test was also conducted on oil-containing sludge before treatment as a blank. Table 3 shows the results of the test.

(Measurement of moisture content)
For the oil-containing sludge before treatment and the treated products obtained in Test Examples C1 to C6, the moisture content was measured for each elapsed day from 0 to 4 days. These results are shown in Table 3.

(State of processed material)
In the blank and Test Examples C1 to C6, photographs of the state of the processed material placed on the test table during the fluidity confirmation test were taken from the top side and the side side. 3.

From the results of Test Examples C1 to C6 shown in Table 3 and FIG. 3, by adding and mixing a water-soluble polymer containing structural units derived from sodium acrylate and acrylamide to the oil-containing sludge, the apparent water content increased. It was confirmed that a crumb-like or nodule-like processed material with a reduced appearance was obtained. In addition, compared to the oil-containing sludge before treatment, this treated material has a higher y value and a lower x value in the fluidity confirmation test, confirming that the fluidity has decreased, making it easy to transport. was found to be

Furthermore, the form of the water-soluble polymer when added to the oil-containing sludge is changed to a dilute liquid (specifically, an aqueous solution containing a water-soluble polymer as a solute or an oil-in-water type containing a water-soluble polymer as a dispersion medium). By forming an emulsion), even when the mixing time of the oil-containing sludge and the water-soluble polymer (dilute liquid) was short, a treated material with reduced fluidity could be obtained. From this, by adding a dilute solution containing 0.1 to 2% by mass of the water-soluble polymer to the oil-containing sludge, the water-soluble polymer can easily spread throughout the oil-containing sludge, and as a result, It was observed that even a smaller amount of added water-soluble polymer resulted in an oil-containing sludge into a treatable material that was easy to transport (Test Examples C2, C4, and C6). Moreover, from the measurement results of the water content, it was confirmed that the treated products obtained in Test Examples C2, C4, and C6 drained water more quickly and dried more quickly.

Claims (13)

Moisture recovered by solid- liquid separation from wastewater generated in the continuous casting process, hot rolling process, or cold rolling process in the steel manufacturing process ;
(Meth) acrylic acid and its salts, and (meth) adding a water-soluble polymer containing a structural unit derived from at least one monomer selected from the group consisting of acrylamide, including a treatment step of mixing ,
The content of the oil in the sludge is 2 to 20% by mass based on the total dry mass of the sludge,
In the treatment step, by adding and mixing the water-soluble polymer to the sludge, the water-soluble polymer adsorbs to the suspended solids in the sludge to bind the suspended solids together, and the binding A method for treating oil-containing sludge, which is a step of obtaining a treated product in which the fluidity of the sludge is reduced by trapping water in the sludge in the accompanying gaps . 2. The method for treating oil-containing sludge according to claim 1, wherein said water-soluble polymer is added to said sludge in powder form. 2. The method for treating oil-containing sludge according to claim 1, wherein said water-soluble polymer is added to said sludge in the form of an emulsion. 2. The method for treating oil-containing sludge according to claim 1, wherein the water-soluble polymer is added to the sludge in the form of a dilute liquid containing 0.1 to 2% by mass of the water-soluble polymer. 5. The method for treating oil-containing sludge according to claim 4, wherein the diluted liquid is an aqueous solution containing the water-soluble polymer as a solute or an oil-in-water emulsion containing the water-soluble polymer as a dispersion medium. 2. The method for treating oil-containing sludge according to claim 1, wherein an aqueous dispersion containing said water-soluble polymer and an aqueous sulfate solution as its dispersion medium is used as said water-soluble polymer. The method for treating oil-containing sludge according to any one of claims 1 to 6 , wherein 0.001 to 1 part by mass of said water-soluble polymer is added per 100 parts by mass of said sludge. The water-soluble polymer contains a structural unit derived from at least one of (meth)acrylic acid and a salt thereof, and a structural unit derived from (meth)acrylamide, (meth)acrylic acid (salt)-(meth ) The method for treating oil-containing sludge according to any one of claims 1 to 7 , wherein the acrylamide copolymer is used. The method for treating oil-containing sludge according to any one of claims 1 to 8, wherein the water-soluble polymer has a weight average molecular weight of 5 million to 30 million. Claims 1 to 9, wherein in the treatment step, the water-soluble polymer is added directly to a tank in which the sludge is stored, and the sludge and the water-soluble polymer are mixed in the tank with a shovel or a bucket. The method for treating oil-containing sludge according to any one of 1. 11. Any one of claims 1 to 10, wherein the water content in the sludge is derived from water used for cooling or cleaning steel materials in the process of manufacturing in the steel manufacturing process or equipment used for the manufacture thereof. A method for treating oil-containing sludge according to the above item. The method for treating oil-containing sludge according to any one of claims 1 to 11, wherein the content of said suspended matter in said sludge is 30 to 90% by mass based on the total dry mass of said sludge. A process of solid-liquid separation of wastewater generated in a continuous casting process, a hot rolling process, or a cold rolling process in the steel manufacturing process to recover water , suspended matter containing iron, and sludge containing oil. When,
A water-soluble polymer containing a structural unit derived from at least one monomer selected from the group consisting of (meth)acrylic acid and its salts and (meth)acrylamide is added to the recovered sludge, and mixed. including a processing step to
The content of the oil in the sludge is 2 to 20% by mass based on the total dry mass of the sludge,
In the treatment step, by adding and mixing the water-soluble polymer to the sludge, the water-soluble polymer adsorbs to the suspended solids in the sludge to bind the suspended solids together, and the binding A method of treating wastewater, which is a step of obtaining a treated product in which the fluidity of the sludge is reduced by trapping water in the sludge in the accompanying gaps .

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