CN113557216A

CN113557216A - Treatment device and treatment method for circulating water of wet coating chamber

Info

Publication number: CN113557216A
Application number: CN202080018747.3A
Authority: CN
Inventors: 池松道雄; 吉田恒行; 饭村晶; 寺嵨光春
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2019-03-05
Filing date: 2020-03-04
Publication date: 2021-10-26
Also published as: WO2020179842A1; JP2020142177A; JP6891908B2

Abstract

A method for treating circulating water of a wet coating room comprises the following steps: the coating material floating mud is formed by adding micro-nano bubbles to at least one circulating water selected from the group consisting of circulating water flowing from the wet coating chamber to one end of the trough or the vicinity thereof and circulating water flowing into one end of the trough or the vicinity thereof and mixed with the circulating water accumulated in the trough, and all or a part of the coating material floating mud is removed from the circulating water, and then the circulating water is returned to the wet coating chamber from the other end of the trough or the vicinity thereof.

Description

Treatment device and treatment method for circulating water of wet coating chamber

Technical Field

The invention relates to a treatment device and a treatment method for circulating water in a wet coating chamber. More particularly, the present invention relates to an apparatus and a method for treating circulating water in a wet coating booth, which can efficiently convert excess paint collected in the wet coating booth into paint sludge that is not sticky and is easily removed, and reduce the amount of paint sludge (sludge) deposited in a pit (pit) or the like.

Background

The remaining coating that was not applied in the wet coating booth was captured with circulating water. Then, the excess paint trapped in the circulating water is removed, and the circulating water from which the excess paint has been removed is reused in the wet coating booth. For this reason, various methods have been proposed for removing the excess paint trapped in the circulating water in the wet coating booth.

For example, patent document 1 discloses a sewage purification system for a paint booth, wherein a paint target to be coated with paint is located above the paint target and a collection tank filled with a collection liquid is provided below the paint target, the collection tank is provided with an aerator therein, and a discharge port of the aerator is provided in a substantially horizontal direction.

Patent document 2 discloses a method of separating and purifying paint residues, which are formed by mixing paint mist into circulating water in a wet coating booth, by separating the paint residues into solvent and non-sticky paint chips by means of air bubbles, which are obtained by micronizing ultrafine air bubbles inherent to an alkaline ionic aqueous detergent by venturi action in the wet coating booth, and floating the paint residues to the liquid surface.

Patent document 3 discloses a method for removing paint mist in a paint booth using microbubbles, which is characterized in that microbubbles generated by a microbubble generation mechanism are discharged into paint booth circulating water in a paint sludge treatment tank of the paint booth, and the paint booth circulating water mixed with microbubbles introduced from the paint sludge treatment tank is sprayed into an exhaust duct of the paint booth to be brought into contact with the paint mist in the exhaust air of the paint booth.

Patent document 4 discloses a volatile organic compound/coating mist removing device in which a rotating fan 4 is disposed at an upper portion in a lens barrel 1, a coating mist flow is sucked into the lens barrel from below, a nozzle 2 for generating microbubbles is disposed downward, a rotating region is formed by a mixed flow of a water particle group diffused in a film shape from the nozzle and an upward flow of coating mist, and a volatile organic compound or coating mist is adsorbed to the water particle group containing microbubbles floating in the region to perform an oxidation treatment.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2004-074084;

patent document 2: japanese patent laid-open publication No. 2009-269024;

patent document 3: japanese patent laid-open publication Nos. 2017 and 100049;

patent document 4: japanese utility model registration No. 3158129.

Disclosure of Invention

Problems to be solved by the invention

The aqueous coating sludge or coating sludge treated with the hydrophilic non-sticking agent has a strong hydrophilicity. Microbubbles, on the other hand, are hydrophobic. Therefore, microbubbles are less likely to adhere to the sludge, the effect of improving the buoyancy cannot be sufficiently exerted, and the clarification of the circulating water may be unstable.

The invention aims to provide a treatment device and a treatment method for circulating water in a wet coating room by utilizing micro-nano bubbles.

Means for solving the problems

As a result of studies to achieve the above object, the present invention including the following embodiments has been completed.

[ 1 ] an apparatus for treating circulating water in a wet coating booth,

comprising: a discharge channel for circulating water to flow from the wet coating chamber to the groove, a micro-nano bubble generating device, and a supply channel for circulating water to flow from the groove to the wet coating chamber,

the outlet of the discharge channel is arranged at or near one end of the groove,

the inlet of the feed channel is arranged at or near the other end of the groove,

the micro-nano bubble discharge port of the micro-nano bubble generating device is provided at least one position selected from the group consisting of a position where circulating water flows through the discharge passage, a position where circulating water flows between the outlet of the discharge passage and circulating water stored in the recess, and a position where circulating water in the recess and discharged from the outlet of the discharge passage is mixed with circulating water stored in the recess.

The device according to [ 1 ], wherein,

the micro-nano bubble discharge port of the micro-nano bubble generating device is arranged at a position where the shearing speed generated by the flowing of circulating water is 0.5-50 s^-1The position of (a).

[3 ] the treatment apparatus for circulating water in a wet coating booth according to [ 1 ] or [2 ], wherein,

the micro-nano bubble generating device is in a pressurizing and dissolving type.

[ 4 ] the processing apparatus according to any one of [ 1 ] to [3 ], wherein,

a water intake device is also provided in the recess and on a side adjacent to the inlet of the feed channel.

[ 5 ] A method for treating circulating water in a wet coating booth,

the method comprises the following steps:

adding micro-nano bubbles to at least one circulating water selected from the group consisting of circulating water flowing from the wet coating chamber to one end of the groove or the vicinity thereof and circulating water flowing into one end of the groove or the vicinity thereof and mixed with the circulating water accumulated in the groove, to form coating float;

subsequently, removing all or a portion of the coating sludge from the circulating water;

then, the circulating water is returned to the wet coating booth from the other end of the groove or the vicinity thereof.

[ 6 ] the processing method according to [ 5 ], wherein,

circulating water to be added with micro-nano bubbles for 0.5-50 s^-1The shear rate of (2).

[ 7 ] the processing method according to [ 5 ] or [ 6 ], wherein,

the average diameter of the micro-nano bubbles when added into the circulating water is less than 100 mu m.

Effects of the invention

According to the apparatus and method for treating circulating water in a wet coating booth of the present invention, regardless of whether the residual paint recovered in the wet coating booth is hydrophilic or hydrophobic, the residual paint can be efficiently converted into paint sludge (flocs, sludge) that is not sticky and is easily removed, so that the amount of paint sludge (sludge) deposited on the grooves and the like can be reduced. In addition, the clarification of the circulating water to be returned to the wet coating booth can be stabilized.

Drawings

FIG. 1 is a perspective view showing a groove used in the method of example 1.

Fig. 2 is a schematic view of the groove shown in fig. 1 when viewed from the side.

FIG. 3 is a perspective view showing a groove used in the method of example 2.

Fig. 4 is a schematic view of the groove shown in fig. 3 when viewed from the side.

Fig. 5 is a schematic view when the groove used for the method of comparative example 1 is viewed from the side.

Detailed Description

The treatment device for the circulating water of the wet coating chamber comprises: a drain channel (hereinafter, also referred to as a drain pipe) for flowing circulating water from the wet coating booth to the recess, the micro-nano bubble generating means, and a supply channel (hereinafter, also referred to as a supply pipe) for flowing circulating water from the recess to the wet coating booth. The outlet of the discharge passage is provided at or near one end of the groove, and the inlet of the supply passage is provided at or near the other end of the groove. It should be noted that, the end of the groove refers to: in the rectangular groove, at least one side of two opposite sides of the rectangle is arranged; at least one of the edges of a central groove (inner circumference) and at least one of the outer circumferential edges of the circular groove. The vicinity of the end means: the area of the range of the end of the groove is considered by those skilled in the art in consideration of the size of the equipment and the like required in actual use. Rectangular grooves are preferred for use in the present invention.

Examples of wet coating booths to which the apparatus and method for treating the circulating water in the wet coating booth of the present invention can be applied include a water flow plate type (water film type) coating booth in which excess paint is collected by water film-like circulating water, a spray type coating booth in which excess paint is collected by water spray-like circulating water, a water film-spray type coating booth in which a water film type and a spray type are combined, and a venturi type coating booth in which excess paint separated by centrifugal force in a vortex booth is collected in water film-like circulating water.

Circulating water (untreated circulating water) containing excess paint and water, which is obtained by collecting the excess paint in the wet coating chamber, flows from the wet coating chamber to the recessed groove in the discharge passage, and when there is a distance between the outlet of the discharge passage and the circulating water stored in the recessed groove, the circulating water moves from the outlet of the discharge passage to the circulating water stored in the recessed groove, mixes with the circulating water stored in the recessed groove, and then temporarily stays in the recessed groove. And removing residual coating from the circulating water during the period that the circulating water is retained in the groove, and clarifying the circulating water. The treated circulating water then flows from the trough to the wet coating booth within the supply channel and is again used to trap the excess paint in the wet coating booth. The residence time of the circulating water in the grooves is not particularly limited, and is, for example, 2 to 5 minutes.

The shape of the groove is not particularly limited, and a groove having a rectangular parallelepiped storage space is preferably used. In order to make it difficult for untreated circulating water to mix with treated circulating water, it is preferable that the supply port for supplying untreated circulating water into the recess, i.e., the outlet of the discharge passage, be disposed as far as possible from the extraction port for extracting treated circulating water from the recess, i.e., the inlet of the supply passage. For example, as shown in fig. 1, a supply port for supplying untreated circulating water into the recess and an extraction port for extracting treated circulating water from the recess can be provided at almost both ends of a diagonal line of the rectangular parallelepiped-shaped retention space.

Examples of the micro-nano bubble generating device include a generating device of a system (crushing system) utilizing a drastic pressure change by ultrasonic waves, shock waves, or the like, a generating device of a system (shearing system) in which a gas is cut into pieces and bubbled by a turbulent flow generated by a venturi tube, a high-speed rotating rotor, or the like in a state in which the gas is mixed with a liquid, a generating device of a system in which the crushing system and the shearing system are combined, a generating device of a system (see japanese patent application laid-open No. 2001-104764 or the like) in which a liquid containing bubbles is obtained by mixing and compressing the gas and the liquid supplied to a cylinder and discharging the liquid through a bubble diffusion hole to the outside, a generating device of a system (pressurized dissolving system) in which a gas is forcibly dissolved in a liquid by pressurization by a compressor or the like and the liquid is depressurized to discharge the gas. Among them, a pressurized dissolution type generating apparatus is preferable.

In the treatment apparatus of the present invention, the micro-nano bubble discharge port of the micro-nano bubble generation means is provided at least one position selected from the group consisting of a position where circulating water flows through the discharge passage, a position where circulating water flows through a space between the outlet of the discharge passage and the circulating water accumulated in the recess, and a position where circulating water in the recess and discharged from the outlet of the discharge passage is mixed with the circulating water accumulated in the recess. The micro-nano bubble discharge port of the micro-nano bubble generating device is preferably arranged at a position where the shearing speed generated by the flowing of circulating water is 0.5-50 s^-1More preferably, the shear rate is 2 to 50s^-1The position of (a). Micro-nano bubble discharge ports are provided at such positions, and micro-nano bubbles are added to at least one circulation water selected from the group consisting of circulation water flowing from the wet coating chamber to the grooves and circulation water flowing into the grooves and mixed with the circulation water accumulated in the grooves, preferably at a shear rate of 0.5 to 50 seconds^-1The circulating water is preferably added at a shear rate of 2-50 s^-1Circulating water of flowTo form a coating float. The amount of the micro-nano bubbles added to the circulating water is preferably 50% or more, more preferably 60% or more, and further preferably 70% or more, with respect to 100% of the total amount of the micro-nano bubbles added. Compared with the method for adding the micro-nano bubbles into the circulating water accumulated in the groove, the method for adding the micro-nano bubbles into the circulating water has the advantages that the contact chance of the micro-nano bubbles and the residual coating is increased, and the attachment efficiency of the micro-nano bubbles to the residual coating is increased.

The circulation water accumulated in the recess can be circulated in the recess for preferably less than 2s^-1More preferably less than 0.5s^-1Adding a part of micro-nano bubbles into the circulating water flowing at the shearing speed. The amount of micro-nano bubbles added to such circulating water accumulated in the grooves or flowing at a low shear rate is preferably 50% or less, more preferably 40% or less, and still more preferably 30% or less, with respect to 100% of the total amount of micro-nano bubbles added.

The average diameter of the micro-nano bubbles when added to the circulating water is preferably 100 μm or less, more preferably 70 μm or less, and still more preferably 50 μm or less. The lower limit of the average diameter of the micro-nano bubbles when added to the circulating water is not particularly limited, and is preferably 0.1 μm, more preferably 0.5 μm, and still more preferably 1 μm. In the pressurized dissolution type generating apparatus, water (micro-nano bubble water) in which gas is forcibly dissolved by pressurization is prepared. The micro-nano bubble water generates micro-nano bubbles in the circulating water by sharp pressure reduction when added to the circulating water.

The total amount of micro-nano bubbles added (air supply amount) is preferably 0.005 to 0.30g, and more preferably 0.05 to 0.15g, based on 1g of the remaining coating material (solid content). By adding micro-nano bubbles, the residual coating flocs can float upwards.

In the present invention, in addition to the micro-nano bubbles, a water treatment agent such as a phenol resin solution or dispersion (hereinafter, also collectively referred to as "a liquid containing a phenol resin"), a low-molecular cationic polymer solution or dispersion (hereinafter, also collectively referred to as "a liquid containing a low-molecular cationic polymer"), a non-sticking agent, an organic coagulant, an inorganic coagulant, and a pH adjuster may be added to the circulating water within a range not to impair the effects of the present invention. The water treatment agent can be added to at least one circulation water selected from the group consisting of circulation water flowing from the wet coating chamber to the pit, circulation water flowing into the pit and mixed with the circulation water accumulated in the pit, and circulation water flowing from the pit to the wet coating chamber.

The phenolic resin solution or dispersion is a solution obtained by dissolving or dispersing a phenolic resin in a solvent or dispersant having a high affinity for water.

The phenol resin is a condensate of a phenol and an aldehyde or a modified product thereof, and is a material before crosslinking and curing. Specific examples of the phenol resin include a condensate of phenol and formaldehyde, a condensate of cresol and formaldehyde, and a condensate of xylenol and formaldehyde. Examples of the modified product include alkyl-modified phenol resins and polyvinyl phenols. These phenolic resins may be of the novolak type, and may be of the resole type. The molecular weight and other physical properties of the phenolic resin are not particularly limited, and the phenolic resin can be appropriately selected from phenolic resins generally used for the treatment of circulating water in a wet coating booth. The phenolic resins may be used singly or in combination of two or more. The weight average molecular weight of the phenol resin used in the present invention is preferably 10000 or less, more preferably 7000 or less.

Examples of the solvent or dispersant that can be used for the phenol resin-containing liquid include ketones such as acetone, esters such as methyl acetate, alcohols such as methanol, alkaline aqueous solutions, and amines. Among these solvents, an aqueous alkaline solution is preferred. Examples of the alkaline aqueous solution include an aqueous sodium hydroxide solution and an aqueous potassium hydroxide solution. The concentration of the alkaline component is preferably 1 to 25% by mass, and the concentration of the phenol resin is preferably 1 to 50% by mass, in the case of a substance obtained by dissolving or dispersing the phenol resin in an alkaline aqueous solution.

Preferably, the liquid containing the phenolic resin is added to the circulating water flowing from the wet coating booth to the pit, the circulating water flowing into the pit and mixed with the circulating water stored in the pit, or the circulating water flowing from the pit to the wet coating booth.

From the viewpoint of non-stick of the residual paint, the amount of the phenol resin (solid content) added is preferably 1mg or more, and more preferably 5mg or more, relative to the circulating water 1L. From the viewpoint of suppressing excessive foaming and an increase in running cost, the upper limit of the amount of the phenol resin (solid content) added to the circulating water 1L is preferably 1000mg, and more preferably 200 mg. The amount of the phenol resin (solid content) added to the remaining coating material (solid content) is preferably 0.1 mass% or more, and more preferably 0.5 mass% or more. The upper limit of the amount of the phenol resin (solid content) added to the residual paint (solid content) is preferably 100 mass%, and more preferably 10 mass%. The phenol resin is suitable for water treatment in circulating water in which a large amount of surface foam of a water-based paint is trapped or circulating water in which an organic solvent paint having a surface potential of almost zero is trapped. By adding the liquid containing the phenol-aldehyde resin, the tackiness (non-stick) of the residual paint in the circulating water can also be reduced.

The low-molecular cationic polymer solution or dispersion is a solution obtained by dissolving or dispersing a low-molecular cationic polymer in a solvent or dispersant having a high affinity for water. The low-molecular cationic polymer used in the present invention has a weight average molecular weight of preferably 1 to 100 ten thousand, more preferably 5 to 30 ten thousand, for example.

Examples of the low-molecular cationic polymer include polyethyleneimine, cationically modified polyacrylamide, polyamine sulfone, polyamide, polyalkylene polyamine, amine crosslinked polycondensate, polydimethylaminoethyl acrylate, dimethyldiallylammonium chloride (DADMAC) polymer, polycondensate of alkylamine and epichlorohydrin, polycondensate of alkylene dichloride and polyalkylene polyamine, polycondensate of dicyandiamide and formalin, homopolymer or copolymer of acid salt or quaternary ammonium salt of DAM (dimethylaminoethyl methacrylate), homopolymer or copolymer of acid salt or quaternary ammonium salt of DAA (dimethylaminoethyl acrylate), polyvinyl amidine, copolymer of diallyldimethylammonium chloride and acrylamide, polycondensate of melamine and aldehyde, polycondensate of dicyandiamide and aldehyde, and polycondensate of dicyandiamide and diethylenetriamine. The alkylamine in the polycondensate of the alkylamine and epichlorohydrin may include monomethylamine, monoethylamine, dimethylamine, diethylamine, and the like. Examples of the aldehyde in the melamine-aldehyde condensate and the dicyandiamide-aldehyde condensate include formaldehyde, acetaldehyde, propionaldehyde, and paraformaldehyde which is a trimer of formaldehyde. The low-molecular cationic polymer may be used singly or in combination of two or more.

Examples of the solvent or dispersant that can be used for the liquid containing the low-molecular cationic polymer include water, acetone, methanol, and the like.

Preferably, a liquid containing a low-molecular cationic polymer is added to the circulating water flowing from the wet coating booth to the pit, the circulating water flowing into the pit and mixed with the circulating water stored in the pit, or the circulating water flowing from the pit to the wet coating booth.

The amount of the low-molecular cationic polymer (solid content) added to the circulating water 1L is preferably 0.1 to 100mg, more preferably 0.3 to 30 mg. The amount of the low-molecular cationic polymer (solid content) added is preferably 10% by mass or less, more preferably 2% by mass or less, relative to the remaining coating material (solid content). The lower limit of the amount of the low-molecular cationic polymer (solid content) added to the remaining coating material (solid content) is preferably 1% by mass, and more preferably 5% by mass.

By adding the liquid containing the low-molecular cationic polymer, the charge of the residual dope in the circulating water can be neutralized, and fine flocs are easily formed.

Examples of the non-sticking agent include carboxylic acid polymers, tannin compounds, tannin base polymers, melamine formaldehyde condensates, melamine dicyandiamide condensates, straight-chain cationic polyamines, sodium zincate, and alumina sols.

As the organic coagulant, sodium alginate; a chitin/chitosan-based coagulant; and biological coagulants such as TKF04 strain and BF 04.

Examples of the inorganic coagulant include aluminum coagulants such as aluminum sulfate (aluminum sulfate), polyaluminum chloride (PAC), aluminum chloride, basic aluminum chloride, and pseudoboehmite alumina sol (alo (oh)); iron salt coagulants such as ferrous hydroxide, ferrous sulfate, ferric chloride, ferric polysulfate, and iron-silicon inorganic polymer coagulants; zinc coagulants such as zinc chloride; active silicic acid, polysilicate iron coagulating agent, etc.

Examples of the pH adjuster include water-soluble alkali metal compounds such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate; mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

All or a portion of the coating float formed as described above is removed from the circulating water.

Preferably, all or a part of the coating material float is removed by taking surface water containing the coating material float and water by using a water taking device. Examples of the water intake device include a surface liquid discharge device such as a float weir and a float pump.

On the other hand, the circulating water (treated circulating water) from which all or a part of the paint float has been removed is supplied to the wet coating booth via the supply passage and is used again for collecting the excess paint. In order to make it difficult for the sludge, silt, floc, etc. to be drawn out with the circulating water, it is preferable to provide a weir, a filter, a mesh, etc. at or near the extraction port of the treated circulating water from the trough. Preferably 50% or more, more preferably 80% or more, further preferably 90% or more, further preferably 95% or more, and particularly preferably 99% or more of the total micro-nano bubbles added between the micro-nano bubble discharge port and the inlet of the supply channel are consumed to form sludge, or dissolved into the circulating water or broken and disappeared on the water surface. The amount of micro-nano bubbles contained in the treated circulating water in the inlet of the supply channel is preferably 50% or less, more preferably 20% or less, still more preferably 9% or less, still more preferably 5% or less, and particularly preferably 1% or less, with respect to 100% of all the micro-nano bubbles added.

In the present invention, it is preferable to add a high molecular cationic polymer solution or dispersion (hereinafter, also collectively referred to as "high molecular cationic polymer-containing liquid") to surface water containing the paint float and water. The liquid containing the high-molecular cationic polymer can aggregate the paint sludge to facilitate solid-liquid separation.

The liquid containing the high molecular cationic polymer is a liquid (W/O emulsion) obtained by dissolving the high molecular cationic polymer in a solvent having a high affinity with water or dispersing a high concentration of the dissolved liquid in a hydrophobic liquid. For example, the weight average molecular weight of the high-molecular cationic polymer is preferably more than 100 ten thousand, more preferably 500 ten thousand or more, and further preferably 600 to 1100 ten thousand.

Examples of the high-molecular cationic polymer include polymers having a cationic structural unit derived from a quaternary ammonium salt of a (meth) acrylate (for example, a copolymer of acrylamide/[ 2- (acryloyloxy) ethyl ] benzyldimethylammonium chloride/[ 2- (acryloyloxy) ethyl ] trimethylammonium chloride, a copolymer of acrylamide/[ 3- (acryloyloxy) propyl ] benzyldimethylammonium chloride/[ 2- (acryloyloxy) ethyl ] trimethylammonium chloride, a copolymer of acrylamide/[ 2- (acryloyloxy) ethyl ] benzyldimethylammonium chloride/[ 3- (acryloyloxy) propyl ] trimethylammonium chloride, a copolymer of acrylamide/[ 3- (acryloyloxy) propyl ] benzyldimethylammonium chloride/[ 3- (acryloyloxy) propyl ] trimethylammonium chloride, and the like), Polyaminoalkyl acrylates, polyaminoalkyl methacrylates, polyethyleneimines, polydiallylammonium halides, chitosan, urea-formaldehyde resins, and the like. The high-molecular cationic polymer may be used alone or in combination of two or more. The amount of the high-molecular cationic polymer (solid content) added is preferably 0.1 to 10% by mass, more preferably 0.2 to 3% by mass, based on the remaining coating material (solid content). For example, the amount of the high-molecular cationic polymer added is preferably 0.001 to 1meq/L, more preferably 0.002 to 0.5meq/L, as the colloid equivalent value with respect to the circulating water. By adding the high-molecular cationic polymer, redispersion of flocs (coating material sludge) can be prevented, and the efficiency of filtration treatment and/or dehydration treatment (sedimentation, centrifugal separation, or the like) which may be performed after the pressure floatation treatment can be improved.

Preferably, the water intake device takes in surface water containing the coating material-containing float sludge and water to which the liquid containing the high-molecular cationic polymer is added, and the water intake liquid taken out by the water intake device is floated, preferably by pressurization.

By performing the floating treatment, the coating material floating mud coagulated from the liquid containing the high-molecular cationic polymer can be floated up to the liquid surface. The pressure floating treatment is a treatment method in which a supersaturated solution of air is injected (pressurized) into a liquid containing a float (at normal pressure) to generate air bubbles, thereby floating the float. The average diameter of the bubbles generated in the pressure floatation treatment is preferably 120 μm or less, and more preferably 30 μm or more and 120 μm or less. The average diameter of the bubbles generated in the pressure floatation process is preferably larger than the average diameter of the micro-nano bubbles.

When the floating treatment is performed, it is further preferable to add an anionic polymer solution or dispersion (hereinafter, also referred to as "anionic polymer-containing liquid") to the liquid extract. The anionic polymer-containing liquid is a liquid (W/O emulsion) obtained by dissolving an anionic polymer in a solvent having a high affinity for water or dispersing a high-concentration dissolved solution in a hydrophobic solvent.

Examples of the anionic polymer include sodium polyacrylate, sodium polyacrylate/amide derivatives, partial hydrolysates of polyacrylamide, partially sulfomethylated polyacrylamide, poly (2-acrylamide) -2-methylpropane sulfate, and the like. The anionic polymer may be used alone or in combination of two or more. The anionic polymer preferably has an anionization degree of 10 to 30 mol%. The weight average molecular weight of the anionic polymer is preferably more than 100 ten thousand, more preferably 500 ten thousand or more, and further preferably 800 to 1500 ten thousand. The amount of the anionic polymer (solid content) added to the remaining coating material (solid content) is preferably 0.1 to 10% by mass, more preferably 0.2 to 3% by mass.

In the present invention, an amphoteric polymer solution or dispersion (hereinafter, also collectively referred to as "amphoteric polymer-containing liquid") can be added to the liquid extract within a range not to impair the effects of the present invention. The amphoteric polymer-containing liquid is a liquid (W/O type emulsion) obtained by dissolving an amphoteric polymer in a solvent having a high affinity with water or dispersing a solution having a high concentration in a hydrophobic solvent.

Examples of the amphoteric polymer include a copolymer of (meth) acrylamide, alkyl (meth) acrylate having a quaternary ammonium group, and sodium (meth) acrylate. The amphoteric polymer preferably has an anion/cation molar ratio of 0.2 to 2.0. The weight average molecular weight of the amphoteric polymer is preferably more than 100 ten thousand, more preferably 500 ten thousand or more, and further preferably 800 to 1000 ten thousand. The amount of the amphoteric polymer (solid content) added is preferably 0.1 to 10% by mass, more preferably 0.2 to 3% by mass, based on the remaining coating material (solid content).

The filtration treatment and/or dehydration treatment can be performed on the water-sampling solution subjected to the pressurization floating treatment. In the filtration process, a wedge wire screen, a rotary screen, a grate screen, a flexible container bag, or the like can be used.

In the dehydration treatment, a cyclone, a centrifugal separator, a pressure filtration device, or the like can be used. The taken sludge can be incinerated, or buried, or composted.

Next, the present invention will be described in more detail with reference to examples. However, the following examples merely show one embodiment of the present invention, and the present invention is not limited to the following examples.

Comparative example 1

In a wet coating booth, automotive parts are spray coated with an organic solvent coating. During this period, circulating water (total amount about 200 m) was used³Circulation velocity of about 30m³Per minute) 77 kg-dry/day of remaining coating was captured. The circulating water trapping the residual coating is retained in the groove. In the range from the central portion of the groove to the position where the float pump is disposed (at a shear rate of 0.1 s)^-1Flow), four shear-type micro-nano bubble generating devices are arranged at the bottom of the groove, and micro-nano bubbles are supplied to circulating water retained in the groove at an air volume of 7 l/min. At the same time, 28% alkaline aqueous solution of phenolic resin was added to the circulating water retained in the groove at a ratio of 5 wt% (solid content) relative to the remaining dope (solid content), and at the same time, the circulating water was stirred and stirredA50% solution of cationic quaternary polyamine having a weight average molecular weight of 10 ten thousand was added to the coating composition (solid content) in an amount of 0.45% by weight (solid content) of the remaining coating composition.

And pumping surface water containing the coating floating mud out of the groove by using a floater pump. To the surface water thus extracted, a 40% solution of an acrylic cationic polymer having a weight average molecular weight of 700 ten thousand was added at a ratio of 0.1% by weight (solid content) to the remaining paint (solid content), and the mixture was transferred to a floatation separator. The liquid containing the coating sludge (slag) separated by the upward floating separation device is transferred to a flexible bulk bag and gravity filtered. The sludge recovery rate was 65% (the sludge moisture content was 74%, the specific gravity was 0.87). The turbidity of the treated circulating water was 52.

Example 1

The installation position of the four shearing micro-nano bubble generating devices is changed to be near the position (with the shearing speed of 20 s) where the circulating water flowing out from the outlet of the discharge pipe in the groove is mixed with the circulating water stored in the groove^-1Flow), the circulating water was treated in the same manner as in comparative example 1 except that. The sludge recovery rate is 100% (the sludge water content is 68%, and the specific gravity is 0.83). The turbidity of the treated circulating water was 10.

Example 2

The micro-nano bubble discharge port is arranged at the position where circulating water flows in the discharge pipe (at the shearing speed of 15 s) instead of four micro-nano bubble generating devices^-1Flow), and micro-nano bubble water was prepared using a pressure dissolution type micro-nano bubble generating apparatus, and the micro-nano bubble water was supplied into the circulating water from the micro-nano bubble discharge port at 42 l/min, except that the circulating water was treated using the same method as in comparative example 1. The sludge recovery rate was 100% (the sludge moisture content was 67%, the specific gravity was 0.83). The turbidity of the treated circulating water was 8.

Comparative example 2

The circulating water was treated in the same manner as in comparative example 1 except that, instead of adding the 28% alkaline aqueous solution of the phenol resin and the 50% solution of the cationic quaternary polyamine, an alkaline aluminum chloride solution (containing 12.2% of Al) was added at a ratio of 3 wt% (solid content) to the remaining coating material (solid content), and a pH adjuster aqueous solution (containing 22.8% of potassium carbonate and potassium hydroxide) was added at a ratio of 6 wt% (solid content) to the remaining coating material (solid content). The sludge recovery rate was 59% (the sludge moisture content was 79%, the specific gravity was 0.87). The turbidity of the treated circulating water was 48.

Example 3

Circulating water was treated in the same manner as in comparative example 2 except that the four shearing micro-nano bubble producing devices were installed at positions near the positions where the circulating water flowed down from the outlet of the discharge pipe and was mixed with the circulating water stored in the pit. The sludge recovery rate is 85% (the water content of the sludge is 77%, and the specific gravity is 0.87). The turbidity of the treated circulating water was 40.

Example 4

The circulating water was treated in the same manner as in comparative example 2 except that four shearing micro-nano bubble generating devices were replaced, the micro-nano bubble discharge port was provided at a position where the circulating water in the discharge pipe flowed, micro-nano bubble water was prepared using a pressure dissolving micro-nano bubble generating device, and the micro-nano bubble water was supplied to the circulating water from the micro-nano bubble discharge port at 42 l/min. The sludge recovery rate is 88% (the water content of the sludge is 76%, and the specific gravity is 0.85). The turbidity of the treated circulating water was 18.

As shown in the above results, according to the treatment method (example) of the present invention, the excess paint recovered in the wet coating booth can be efficiently converted into non-sticky and easily removed paint sludge (flocs, sludge), and the amount of paint sludge (sludge) deposited in the pit or the like can be reduced. In addition, the clarification of the circulating water that flows back to the wet coating booth can be stabilized.

Description of reference numerals

2: untreated circulating water from a paint booth

3: liquid containing phenolic resin or alkaline aluminium chloride solution

4: liquid or aqueous pH-adjusting agent solution containing low-molecular cationic polymer

5: treated circulating water to a coating booth

6: getting the water solution

7: micro-nano bubble

8: micro-nano bubble generating device

9: water intake device (flow pump)

10: weir type

11: coating floating mud

12: coating sludge (silt)

13: liquid containing high-molecular cationic polymer

14: air (a)

15: micro-nano bubble water.

Claims

1. A treatment device for circulating water in a wet coating room,

2. The processing apparatus of claim 1,

3. The processing apparatus of claim 1 or 2,

4. The processing apparatus according to any one of claims 1 to 3,

5. A method for treating circulating water in a wet coating chamber,

the method comprises the following steps:

6. The processing method of claim 5,

7. The processing method according to claim 5 or 6,