JP7707680B2 - Apparatus and method for treating circulating water in a wet paint booth - Google Patents

Description

The present invention relates to an apparatus and method for treating circulating water in a wet paint booth. More specifically, the present invention relates to an apparatus and method for treating circulating water in a wet paint booth, which efficiently obtains paint sludge by subjecting excess paint captured by the circulating water to treatments such as detackification, coagulation, and aggregation, and then floats the resulting paint sludge for efficient removal.

In the wet paint booth, excess paint that has not been applied is captured by circulating water. The excess paint captured in the circulating water is then removed, and the circulating water from which the excess paint has been removed is reused in the wet paint booth. For this reason, various methods have been proposed for removing excess paint captured in the circulating water in the wet paint booth.

For example, Patent Document 1 discloses a method for treating circulating water in a wet paint booth, which includes retaining circulating water containing excess paint and water discharged from a wet paint booth in a pit for a predetermined period of time, adding a phenolic resin solution or dispersion, a low molecular weight cationic polymer solution or dispersion, a tannin alkaline solution, a high molecular weight cationic polymer solution or dispersion containing a benzyl group, and a high molecular weight anionic polymer solution or dispersion to the circulating water in the upstream area of the pit, adding micro-nano bubbles to the circulating water to form a paint floating sludge, and then removing all or a part of the paint floating sludge from the circulating water.

Patent Document 2 discloses a method for treating circulating water in a wet paint booth, which includes adding micro-nano bubbles to at least one of the following: circulating water flowing from a wet paint booth toward one end of a pit or its vicinity; and circulating water flowing into one end of the pit or its vicinity and mixing with the circulating water accumulated in the pit, forming paint floating sludge, then removing all or part of the paint floating sludge from the circulating water, and then returning the circulating water from the other end of the pit or its vicinity to the wet paint booth.

Patent Document 3 discloses a method for treating circulating water in a wet painting booth, which includes adding an alkaline solution of a phenolic resin to the circulating water containing paint to treat the paint in the circulating water, and adjusts the pH of the circulating water to 6.5 to 8.0, and is characterized in that when the pH of the circulating water reaches a predetermined value of 8.0 or less, the amount of the alkaline solution of the phenolic resin added is increased.

Patent document 4 describes a method for controlling the injection of a treatment agent into circulating water in a wet painting booth to make the paint in the circulating water non-sticky, coagulate or float, and is characterized in that the addition of the treatment agent to the circulating water is controlled based on the amount of foaming in the circulating water (e.g., the height of bubbles in a circulating water tank).

Patent Document 5 discloses a method for controlling the injection of a treatment agent into circulating water in a wet painting booth to make the paint in the circulating water non-sticky, coagulate or float, and is characterized in that the addition of the treatment agent to the circulating water is controlled based on the turbidity or suspended solids concentration of the circulating water.

JP 2020-93228 A JP 2020-142177 A WO 2016/013586 A1 JP 2019-202281 A JP 2019-202280 A

Generally, sludge made of excess paint floating in the circulating water stored in the circulating water pit is removed by floating it up. However, sludge made of floating excess paint is highly sticky and easily adheres to the inner walls of pipes, tanks, etc., and once attached, it is difficult to remove. Even after it is removed by floating it up, the efficiency of solid-liquid separation is low, and only sludge waste with a high moisture content may be obtained. On the other hand, sludge made of excess paint that has accumulated in the circulating water stored in the circulating water pit is not easy to lift up using conventional methods, especially if it is in a compacted state, and is often difficult to remove. The accumulated sludge can be removed by temporarily stopping the use of the circulating water pit, dredging the bottom, and taking out the accumulated sludge, but this requires time and money, such as temporarily stopping the use of the circulating water pit.

The object of the present invention is to provide an apparatus and method for treating circulating water in a wet paint booth, which can efficiently obtain paint sludge by subjecting the excess paint captured by the circulating water to treatments such as detackification, coagulation, and aggregation, and can float the resulting paint sludge for efficient removal.

As a result of our investigations to achieve the above objective, we have completed the present invention, which includes the following aspects:

[1] Excess paint generated in a wet painting booth is captured by circulating water,
The circulating water containing the captured excess paint is sent to a circulating water pit,
The circulating water is temporarily stored in a circulating water pit;
Water containing micro-nano bubbles is sprayed into the circulating water stored in the circulating water pit to encourage the sludge made from excess paint to float up,
removing all or a part of the floating sludge from the circulating water, and then returning the circulating water from which the sludge has been removed from the circulating water pit to the wet paint booth;
and adding water treatment agents to the circulating water.
measuring the amount of foaming of the circulating water, the turbidity or concentration of suspended solids in the circulating water, and/or the pH of the circulating water; and adjusting the amount of water treatment agent added and/or the amount of water containing micro-nano bubbles injected based on the measured values so that the amount of foaming of the circulating water, the turbidity or concentration of suspended solids in the circulating water, and/or the pH of the circulating water are within a predetermined range.
How to treat circulating water in a wet paint booth.

[2] Capture excess paint generated in wet painting booths with circulating water,
The circulating water containing the captured excess paint is sent to a circulating water pit,
The circulating water is temporarily stored in a circulating water pit;
Water containing micro-nano bubbles is sprayed into the circulating water stored in the circulating water pit to encourage the sludge made from excess paint to float up,
removing all or a portion of the floating sludge from the circulating water, and then returning the circulating water from which the sludge has been removed from the circulating water pit to the wet paint booth;
and adding a water treatment agent to the circulating water; and adjusting the amount of water treatment agent added or the amount of water containing micro-nano bubbles sprayed in response to an event in the wet paint booth.
How to treat circulating water in a wet paint booth.

[3] The treatment method according to [2], wherein the event in the wet paint booth is start or stop of the wet paint booth, start or stop of painting, disposal of paint or paint washing liquid into circulating water, dumping or undercoating, intermediate coating, or top coating.
[4] The treatment method according to any one of [1] to [3], wherein water containing micro-nano bubbles is sprayed toward the bottom of the circulating water pit.

[5] Search for sludge consisting of excess paint accumulated at the bottom of the circulating water pit;
The treatment method according to any one of [1] to [4], further comprising adjusting a position or a direction for spraying water containing micro-nano bubbles based on the search results.

[6] Circulating water pit,
A drain for circulating water from the wet paint booth to the circulating water pit;
Micro-nano bubble generator,
A supply line for flowing circulating water from the circulating water pit to the wet paint booth;
A mechanism for adding a water treatment agent to the circulating water;
The present invention is provided with a measuring device for measuring the amount of foaming of the circulating water, the turbidity or the concentration of suspended solids in the circulating water, and/or the pH of the circulating water, and an adjusting device having a control algorithm for adjusting the amount of water treatment agent added or the amount of water containing micro-nano bubbles injected based on the measurement values obtained by the measuring device so that the amount of foaming of the circulating water, the turbidity or the concentration of suspended solids in the circulating water, and/or the pH of the circulating water are within a predetermined value range,
The micro-nano bubble generator is installed so that the nozzle for water containing micro-nano bubbles can inject water containing micro-nano bubbles from the circulating water stored in the circulating water pit.
Equipment for treating circulating water in wet paint booths.

[7] Circulating water pit,
A drain for circulating water from the wet paint booth to the circulating water pit;
Micro-nano bubble generator,
A supply line for flowing circulating water from the circulating water pit to the wet paint booth;
A mechanism for adding a water treatment agent to the circulating water;
The present invention provides an adjustment device having a control algorithm for adjusting the amount of water treatment agent added or the amount of water containing micro-nano bubbles sprayed in response to an event in the wet paint booth,
The micro-nano bubble generator is installed so that the nozzle for water containing micro-nano bubbles can inject water containing micro-nano bubbles from the circulating water stored in the circulating water pit.
Equipment for treating circulating water in wet paint booths.

[8] A treatment device according to [6] or [7], in which the water injection port containing micro-nano bubbles is installed so as to inject water containing micro-nano bubbles toward the bottom of the circulating water pit.

[9] The treatment device according to any one of [6] to [8], further comprising a sensor for detecting sludge consisting of excess paint accumulated at the bottom of the circulating water pit.
[10] The micro-nano bubble generator has a mechanism for adjusting the position or direction of the nozzle of the water containing micro-nano bubbles,
The treatment device according to any one of [6] to [9], wherein the adjustment device further has a control algorithm for adjusting the position or direction of the nozzle of the water containing micro-nano bubbles.

According to the wet painting booth circulating water treatment device and treatment method of the present invention, the excess paint captured by the circulating water can be detackified, coagulated, aggregated, etc. to efficiently obtain paint sludge, and the paint sludge can be floated and efficiently removed. In addition, the wet painting booth circulating water treatment device and treatment method of the present invention can be expected to promote the decomposition of harmful substances and organic matter in the sludge by aerobic microorganisms. According to the present invention, the unnecessary addition and injection of water containing water treatment agents and micro-nano bubbles in the treatment of wet painting booth circulating water is reduced, operation costs can be reduced, and sludge with a low moisture content can be obtained, thereby reducing waste disposal costs. In the present invention, automatic control is adopted to increase the peace of mind, stability, or safety of the work, and reduce labor costs.

FIG. 1 is a diagram showing an example of the configuration of a processing device according to the present invention;

The method for treating circulating water in a wet paint booth of the present invention includes capturing excess paint generated in the wet paint booth 1 with circulating water A, sending the circulating water containing the captured excess paint to the circulating water pit 25, temporarily storing the circulating water in the circulating water pit, removing all or part of the floating sludge from the circulating water, and then returning the circulating water from which the sludge has been removed from the circulating water pit to the wet paint booth.

The wet paint booth circulating water treatment device of the present invention also includes a circulating water pit 25, a discharge passage for flowing circulating water from the wet paint booth toward the circulating water pit, and a supply passage for flowing circulating water from the circulating water pit toward the wet paint booth.

Wet paint booths to which the wet paint booth circulating water treatment device and treatment method of the present invention can be applied include, for example, water flow plate type (water film type) paint booths that capture excess paint with a water film of circulating water, shower type paint booths that capture excess paint with shower-like circulating water, water film/shower type paint booths that combine the water film type and shower type, and Venturi type paint booths that capture excess paint separated by centrifugal force in a swirl chamber in a water film of circulating water.

Various events are held in the wet paint booth. For example, when a car 24 enters the wet paint booth 1 on the conveyor, spraying (painting) of paint starts, and when painting is completed, spraying (painting) of paint stops, and the painted car leaves the wet paint booth. In such events, surplus paint may be generated intermittently in the wet paint booth. In addition, the main event of painting is spraying or undercoating, undercoating or topcoating, and the properties of the paint, the amount used, and the amount of surplus paint generated may differ for each of these modes. In addition, as an event, the disposal of paint or paint cleaning fluid into the circulating water may be performed. When the paint booth is operated only during the daytime, or when work is performed for maintenance or inspection of the paint booth, non-steady operation is performed to start or stop the wet paint booth. In non-steady operation, the properties and amount of paint used may be different from those in steady operation, and different substances such as thinners and cleaning fluids may be used. The method of one embodiment of the present invention further includes adjusting the amount of water treatment agent added or the amount of water containing micro-nano bubbles sprayed in response to the occurrence of such an event in the wet paint booth using empirical rules, an expert system, trained AI, or the like. The apparatus of one embodiment of the present invention further includes an adjustment device having a control algorithm for adjusting the amount of water treatment agent added or the amount of water containing micro-nano bubbles sprayed in response to an event in the wet paint booth. It may include transmitting execution information of such an event in the wet paint booth to the adjustment device and using it for automatic control, which will be described later.

The circulating water (untreated circulating water Au) containing excess paint and water obtained by capturing excess paint in the wet painting booth flows in the discharge path from the wet painting booth toward the circulating water pit, and if there is a distance (drop) between the outlet of the discharge path and the water level of the circulating water accumulated in the circulating water pit, it moves from the outlet of the discharge path toward the water level of the circulating water accumulated in the circulating water pit, and the circulating water flowing out from the outlet of the discharge path in the circulating water pit and in the circulating water pit mixes with the circulating water previously stored in the circulating water pit, and is then temporarily stored in the circulating water pit. While the circulating water is stored in the circulating water pit, sludge consisting of excess paint is removed from the circulating water, and the circulating water is clarified. The treated circulating water At then flows in the supply path from the circulating water pit toward the wet painting booth, is returned to the wet painting booth, and is reused to capture excess paint in the wet painting booth. The residence time of the circulating water in the circulating water pit is not particularly limited, but is preferably 1 to 20 minutes, more preferably 2 to 5 minutes, for example.

The circulating water pit 25 is not particularly limited by its shape as long as it can store the circulating water. For example, a rectangular pit with a storage space of a rectangular parallelepiped shape (rectangular pit), a cylindrical or annular cylindrical storage space (circular pit), etc. are used. In order to prevent the untreated circulating water from mixing with the treated circulating water, it is preferable to install the supply port of the untreated circulating water to the circulating water pit, i.e., the outlet of the discharge path, as far away as possible from the outlet of the treated circulating water from the circulating water pit, i.e., the inlet of the supply path. For example, the supply port of the untreated circulating water to the circulating water pit and the outlet of the treated circulating water from the circulating water pit can be provided at diagonal positions of the storage space. More specifically, for example, the outlet of the discharge path can be provided at one end of the circulating water pit or nearby, and the inlet of the supply path can be provided at the other end of the circulating water pit or nearby. In addition, the edge of the pit means at least one of the two opposing sides of the rectangle in the case of a rectangular pit, and at least one of the edges of the center well (inner circumference) and at least one of the edges of the outer circumference in the case of a circular pit. The vicinity of the edge refers to a location that a person skilled in the art would recognize as the edge of the pit, taking into consideration the size of the equipment required for actual operation, etc.

All or part of the floated sludge is removed from the circulating water. The removal of all or part of the floated sludge is preferably carried out by taking in surface water containing the floated sludge and water using a water intake device. Examples of the water intake device include surface liquid discharge devices such as float weirs and float pumps.

It is preferable to subject the intake liquid taken in by the intake device to a flotation process, preferably a pressurized flotation process. By subjecting the intake liquid to a flotation process, the flocculated floating sludge can be made to float. The pressurized flotation process is a processing method for generating air bubbles and floating the floating matter by injecting a supersaturated air solution (pressurized) into a liquid (normal pressure) containing the floating matter. The average diameter of the bubbles generated in the pressurized flotation process is preferably 120 μm or less, more preferably 30 μm or more and 120 μm or less. It is preferable that the average diameter of the bubbles generated in the pressurized flotation process is larger than the average diameter of the micro-nano bubbles described below.

The intake water that has been subjected to the pressure flotation treatment can be subjected to a filtration treatment and/or a dehydration treatment. In the filtration treatment, a wedge wire screen, a rotary screen, a bar screen, a flexible container bag, etc. can be used.
In the dewatering process, a cyclone, a centrifuge, a pressure filter, etc. can be used. The extracted sludge can be incinerated, buried, or composted.
Furthermore, the water obtained by filtering and/or dehydrating the intake water can be reused as circulating water.

Meanwhile, the circulating water from which all or part of the floating sludge has been removed (treated circulating water At) is supplied to the wet painting booth via a supply line and reused to capture excess paint. In order to prevent slag, sludge, flocs, etc. from being entrained in the circulating water and being drawn off, it is preferable to provide a weir, filter, net, etc. at or near the outlet for the treated circulating water from the circulating water pit.

A method for treating circulating water in a wet paint booth according to one embodiment of the present invention further comprises adding a water treatment agent to the circulating water, injecting water containing micro-nano bubbles into the circulating water stored in a circulating water pit to promote the floating of sludge consisting of excess paint, measuring the amount of foaming of the circulating water, the turbidity or suspended solids concentration of the circulating water, and/or the pH of the circulating water, and adjusting the amount of water treatment agent added and/or the amount of water containing micro-nano bubbles injected based on the measured values so that the amount of foaming of the circulating water, the turbidity or suspended solids concentration of the circulating water, and/or the pH of the circulating water are within a predetermined value range.
In addition, the treatment device for circulating water in a wet paint booth according to one embodiment of the present invention further comprises a mechanism for adding a water treatment agent to the circulating water, a micro/nano bubble generator, a measuring device for measuring the amount of foaming in the circulating water, the turbidity or the concentration of suspended solids in the circulating water, or the pH of the circulating water, and an adjusting device having a control algorithm for adjusting the amount of water treatment agent to be added or the amount of water containing micro/nano bubbles to be sprayed based on the measurement values obtained by the measuring device so that the amount of foam in the circulating water, the turbidity or the concentration of suspended solids in the circulating water, or the pH of the circulating water falls within a predetermined value range.

Water treatment agents include detackifiers, coagulants, flocculants, pH adjusters, and defoamers.

There are no particular limitations on the detackifying agent, so long as it can reduce the adhesive strength of the surface of excess paint. Examples include alumina sol, sepiolite, phenolic resin, melamine formaldehyde resin, phenol formaldehyde resin, melamine dicyandiamide condensate, bentonite, hectorite, linear cationic polyamine, sodium zincate, carboxylic acid polymer, tannin, tannin compound, tannin base polymer, cellulose acetate, and the like. Of these, phenolic resin is preferred. Phenolic resin is suitable for water treatment in circulating water with a lot of surface bubbles that has captured water-based paint, or in circulating water that has captured organic solvent paint with a surface potential of almost zero, so phenolic resin can be selected as a detackifying agent in response to such events in a wet painting booth.

The phenol resin is preferably added in the form of a phenol resin solution or dispersion (hereinafter referred to as a phenol resin-containing liquid) obtained by dissolving or dispersing the phenol resin in a solvent or dispersion medium having high affinity for water.
The phenolic resin is a condensate of phenols and aldehydes or a modified product thereof, either before or after crosslinking and curing. Specific examples of the phenolic resin include a condensate of phenol and formaldehyde, a condensate of cresol and formaldehyde, and a condensate of xylenol and formaldehyde. Modified products include alkyl-modified phenolic resins and polyvinylphenol. These phenolic resins may be of the novolac type or resol type. The phenolic resin is not particularly limited by its molecular weight or other physical properties, and may be appropriately selected from those generally used for treating circulating water in wet paint booths. The phenolic resin may be used alone or in combination of two or more types. The weight-average molecular weight of the phenolic resin used in the present invention is preferably 10,000 or less, more preferably 7,000 or less.

Examples of solvents or dispersion media that can be used in the phenolic resin-containing liquid include ketones such as acetone, esters such as methyl acetate, alcohols such as methanol, aqueous alkali solutions, and amines. Of these solvents, aqueous alkali solutions are preferred. Examples of aqueous alkali solutions include aqueous sodium hydroxide solutions and aqueous potassium hydroxide solutions. The product obtained by dissolving or dispersing phenolic resin in an aqueous alkali solution preferably has an alkaline component concentration of 1 to 25% by mass, and a phenolic resin concentration of 1 to 50% by mass.

The detackifying agent can be added to the circulating water in the wet painting booth, the circulating water flowing from the wet painting booth toward the circulating water pit, the circulating water that has flowed into the circulating water pit and mixed with the circulating water that has accumulated there, the circulating water that has accumulated in the circulating water pit, or the circulating water flowing from the circulating water pit toward the wet painting booth, and is preferably added to the circulating water flowing from the wet painting booth toward the circulating water pit, the circulating water that has flowed into the circulating water pit and mixed with the circulating water that has accumulated in the circulating water pit, the circulating water that has accumulated in the circulating water pit, or the circulating water flowing from the circulating water pit toward the wet painting booth.

Coagulants have the effect of neutralizing the electric charge of fine particles in water to cause them to coagulate. Coagulants are broadly classified into organic coagulants and inorganic coagulants.
Examples of organic coagulants include sodium alginate, chitin/chitosan-based coagulants, biocoagulants such as TKF04 and BF04, cationic polymer coagulants, etc. Examples of cationic polymer coagulants include those made of cationic polymers (hereinafter referred to as low molecular weight cationic polymers) having a weight average molecular weight of preferably 1,000 to 1,000,000, more preferably 5,000 to 300,000.

Inorganic coagulants include aluminum-based coagulants such as aluminum sulfate (aluminum sulfate), polyaluminum chloride (PAC), polyaluminum hydroxychloride, pseudoboehmite alumina sol (AlO(OH)), aluminum chloride, and basic aluminum chloride; iron salt-based coagulants such as ferrous hydroxide, ferrous sulfate, ferric chloride, polyferric sulfate, and iron-silica inorganic polymer coagulants; zinc-based coagulants such as zinc chloride; activated silicic acid, and polysilica iron coagulants.

As the coagulant used in the present invention, a low molecular weight cationic polymer is preferred. The low molecular weight cationic polymer is preferably added in the form of a low molecular weight cationic polymer solution or dispersion (hereinafter referred to as a low molecular weight cationic polymer-containing liquid) that is dissolved or dispersed in a solvent or dispersion medium that has high affinity with water.

Examples of low molecular weight cationic polymers include polyethyleneimine, cationic modified polyacrylamide, polyamine, polyamine sulfone, polyamide, polyalkylene polyamine, amine cross-linked polycondensates, polydimethylaminoethyl acrylate, dimethyldiallyl ammonium chloride (DADMAC) polymer, polycondensates of alkylamine and epichlorohydrin, polycondensates of alkylene dichloride and polyalkylene polyamine, polycondensates of dicyandiamide and formalin, homopolymers or copolymers of acid salts or quaternary ammonium salts of DAM (dimethylaminoethyl methacrylate), homopolymers or copolymers of acid salts or quaternary ammonium salts of DAA (dimethylaminoethyl acrylate), polyvinyl amidine, copolymers of diallyl dimethyl ammonium chloride and acrylamide, polycondensates of melamine and aldehyde, polycondensates of dicyandiamide and aldehyde, and polycondensates of dicyandiamide and diethylene triamine. Examples of the alkylamine in the polycondensation product of alkylamine and epichlorohydrin include monomethylamine, monoethylamine, dimethylamine, and diethylamine. Examples of the aldehyde in the melamine-aldehyde condensation product and the dicyandiamide-aldehyde polycondensation product include formaldehyde, acetaldehyde, propionaldehyde, and paraformaldehyde, which is a trimer of formaldehyde. The low molecular weight cationic polymer may be used alone or in combination of two or more.

Solvents or dispersion media that can be used in the low molecular weight cationic polymer-containing liquid include water, acetone, and methanol.

The coagulant can be added to the circulating water in the wet painting booth, the circulating water flowing from the wet painting booth toward the circulating water pit, the circulating water that has flowed into the circulating water pit and mixed with the circulating water that has accumulated there, the circulating water that has accumulated in the circulating water pit, or the circulating water flowing from the circulating water pit toward the wet painting booth, and is preferably added to the circulating water flowing from the wet painting booth toward the circulating water pit, the circulating water that has flowed into the circulating water pit and mixed with the circulating water that has accumulated there, the circulating water that has accumulated in the circulating water pit, or the circulating water flowing from the circulating water pit toward the wet painting booth. The addition of the coagulant can neutralize the charge of the excess paint in the circulating water, making it easier to form fine flocs.

The detackifier and the coagulant can be added to the circulating water either separately or in combination. Adding the detackifier and the coagulant together or in a mixed state can facilitate the formation of fine flocs with low adhesion.

A flocculant can be added to form coarse flocs. The addition of a flocculant causes the solidified flocs of excess paint obtained by the action of the coagulant to aggregate and form coarse flocs, which promotes sedimentation and centrifugation and allows sludge waste with a low moisture content to be obtained.

The flocculant may be a polymer flocculant made of an anionic polymer, a cationic polymer, an amphoteric polymer, etc. Such a polymer usually has a weight average molecular weight of more than 1 million, preferably 5 million or more.
Examples of polymer flocculants made of anionic polymers include sodium polyacrylate, polyacrylic acid soda amide derivatives, partial hydrolyzates of polyacrylamide, partially sulfomethylated polyacrylamide, poly(2-acrylamide)-2-methylpropane sulfate, and the like.
Examples of polymer flocculants made of cationic polymers include polyaminoalkyl acrylate, polyaminoalkyl methacrylate, polyethyleneimine, halogenated polydiallyl ammonium, chitosan, and urea-formalin resin.
Examples of polymer flocculants made of amphoteric polymers include copolymers of acrylamide, aminoalkyl methacrylate, and sodium acrylate.

As a polymer flocculant consisting of a cationic polymer, it is preferable to use a high molecular weight cationic polymer solution or dispersion (hereinafter, these may be collectively referred to as "high molecular weight cationic polymer-containing liquid").

The high molecular weight cationic polymer-containing liquid is prepared by dissolving a high molecular weight cationic polymer in a solvent having a high affinity for water, or dispersing the high concentration solution in a hydrophobic liquid (W/O type emulsion). For example, the high molecular weight cationic polymer preferably has a weight average molecular weight of more than 1 million, more preferably 5 million or more, and even more preferably 6 million to 11 million.

Examples of the high molecular weight cationic polymer include polymers having cationic structural units derived from quaternary ammonium salts of (meth)acrylic acid esters (e.g., copolymers of acrylamide/[2-(acryloyloxy)ethyl]benzyldimethylammonium chloride/[2-(acryloyloxy)ethyl]trimethylammonium chloride, copolymers of acrylamide/[3-(acryloyloxy)propyl]benzyldimethylammonium chloride/[2-(acryloyloxy)ethyl]trimethylammonium chloride, copolymers of acrylamide/[2-(acryloyloxy)ethyl]benzyldimethylammonium chloride/[3-(acryloyloxy)propyl]trimethylammonium chloride, copolymers of acrylamide/[3-(acryloyloxy)propyl]benzyldimethylammonium chloride/[3-(acryloyloxy)propyl]trimethylammonium chloride, etc.), polyaminoalkyl acrylates, polyaminoalkyl methacrylates, polyethyleneimines, halogenated polydiallyl ammonium, chitosan, urea-formaldehyde resins, and the like. The high molecular weight cationic polymers can be used alone or in combination of two or more.
The addition of a high molecular weight cationic polymer can prevent redispersion of flocs (floated sludge) and can increase the efficiency of the filtration and/or dewatering treatment (sedimentation, centrifugation, etc.) that may be performed after the pressure flotation treatment, thereby producing sludge waste with a lower moisture content.

As the polymer flocculant made of an anionic polymer, it is preferable to use an anionic polymer solution or dispersion (hereinafter, these may be collectively referred to as "anionic polymer-containing liquid").
The anionic polymer-containing liquid is prepared by dissolving an anionic polymer in a solvent having a high affinity for water, or dispersing the high-concentration solution in a hydrophobic solvent (W/O type emulsion), or the like.
Examples of the anionic polymer include sodium polyacrylate, polyacrylate soda amide derivatives, polyacrylamide partial hydrolysates, partially sulfomethylated polyacrylamides, poly(2-acrylamide)-2-methylpropane sulfate, etc. The anionic polymer may be used alone or in combination of two or more. The anionic polymer is preferably one having a degree of anionization of 10 to 30 mol%. The weight average molecular weight of the anionic polymer is preferably more than 1 million, more preferably 5 million or more, and even more preferably 8 million to 15 million.

As the polymer flocculant made of an amphoteric polymer, it is preferable to use an amphoteric polymer solution or dispersion (hereinafter, these may be collectively referred to as "amphoteric polymer-containing liquid").
The amphoteric polymer-containing liquid is prepared by dissolving an amphoteric polymer in a solvent having a high affinity for water or dispersing a high-concentration solution of the amphoteric polymer in a hydrophobic solvent (W/O type emulsion), or the like.
Examples of the amphoteric polymer include a copolymer of (meth)acrylamide, a quaternary ammonium alkyl (meth)acrylate, and sodium (meth)acrylate. The anion/cation molar ratio of the amphoteric polymer is preferably 0.2 to 2.0. The weight average molecular weight of the amphoteric polymer is preferably more than 1 million, more preferably 5 million or more, and even more preferably 8 million to 10 million.

The coagulant can be added to the circulating water in the wet paint booth, the circulating water flowing from the wet paint booth toward the circulating water pit, the circulating water that has flowed into the circulating water pit and is mixed with the circulating water accumulated in the circulating water pit, the circulating water that has accumulated in the circulating water pit, the circulating water flowing from the circulating water pit toward the wet paint booth, the surface water, or the intake liquid, but it is preferable to add the coagulant to the surface water or the intake liquid.
The high molecular weight cationic polymer is preferably added to the surface water (the circulating water containing the floating sludge).
The anionic polymer solution or dispersion is preferably added to the intake water (circulating water taken from surface water).
The amphoteric polymer solution or dispersion is preferably added to the intake water (circulating water taken from surface water).

Examples of pH adjusters include water-soluble alkali metal compounds such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc.; mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc. The pH of the circulating water may also vary due to other water treatment agents such as detackifiers, coagulants, flocculants, etc., and these may also function as pH adjusters.
The pH adjuster can be added to the circulating water flowing from the wet paint booth toward the circulating water pit, the circulating water that flows into the circulating water pit and mixes with the circulating water accumulated in the circulating water pit, the circulating water that has accumulated in the circulating water pit, the circulating water flowing from the circulating water pit toward the wet paint booth, the circulating water, surface water, or intake water in the wet paint booth.

The water treatment agents can be prepared in advance and stored in tanks 13, etc. The amount of water treatment agent stored can be measured using a liquid level gauge 14 attached to the tank, and the measured value can be incorporated into the control system to issue a warning in the event of a shortage or deficiency of the water treatment agent.

Examples of micro-nano bubble generators 16 include generators that use a sudden pressure change caused by ultrasound, shock waves, etc. (crushing type), generators that use a turbulent flow generated by a Venturi tube or high-speed rotating rotor in a state where gas and liquid are mixed together to shred the gas into bubbles (shear type), generators that combine the crushing type and shearing type, generators that mix and compress gas and liquid supplied to a cylinder to obtain a liquid containing bubbles, and then release this through bubble diffusion holes to the outside, generators that forcibly dissolve gas into liquid by applying pressure with a compressor, etc., and generators that mix liquid and gas using a turbo pump to dissolve the gas into the liquid.

The water containing micro-nano bubbles used in the present invention (hereinafter sometimes referred to as micro-nano bubble water) has a volume ratio of air to water of preferably 0.01 or more, more preferably 0.05 or more, at 20°C and 1 atmospheric pressure. The upper limit of this volume ratio is determined according to the micro-nano bubble generator.

The water used to produce the micro-nano bubble water may be water supplied from outside the system, or it may be treated circulating water. For example, a portion of the treated circulating water (circulating water from which sludge has been removed) At may be supplied to the micro-nano bubble generator via a branch channel or the like, rather than being returned to the wet paint booth.

The micro-nano bubble generator has an injection port for micro-nano bubble water. The injection port is provided so that the micro-nano bubble water can be injected into the circulating water stored in the circulating water pit. The injection port for micro-nano bubble water is preferably provided so that the micro-nano bubble water can be injected toward the bottom of the circulating water pit. By injecting the micro-nano bubble water toward the bottom of the circulating water pit, the sludge that has accumulated at the bottom of the circulating water pit can be lifted up and suspended in the circulating water, and the adhesion of the micro-nano bubbles gives the sludge buoyancy, allowing it to float up.

The number-average diameter of the micro-nano bubbles when sprayed into the circulating water is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less. There is no particular lower limit to the number-average diameter of the micro-nano bubbles when sprayed into the circulating water, but it is preferably 0.1 μm, more preferably 0.5 μm, and even more preferably 1 μm.

The spray speed of the micro-nano bubble water is preferably 0.1 m/sec or more, more preferably 0.2 m/sec or more. The higher the spray speed, the easier it is to stir up the sludge accumulated at the bottom of the circulating water pit. The spray speed increases as the size of the spray nozzle becomes smaller and the amount of spray increases. The amount of sprayed micro-nano bubble water can be changed by adjusting the discharge volume or discharge pressure of the pump. The spray nozzle is preferably provided in a nozzle. The spray of micro-nano bubble water may be performed continuously or intermittently at regular or irregular intervals.

In the present invention, it is preferable to include a search for sludge consisting of excess paint accumulated at the bottom of the circulating water pit. Through this search, the location and amount of sludge accumulated are grasped. The search can be performed with the naked eye, a sensor, etc. An interface meter can be used as the sensor 21 for the search. The interface meter is not particularly limited in terms of the detection method, and can be, for example, an optical interface meter, an ultrasonic interface meter, an impedance interface meter, a capacitance interface meter, etc. In general, ultrasonic interface meters are widely used in sludge management. However, ultrasonic interface meters are susceptible to the influence of air bubbles in the detection value. When using an interface meter whose detection value is susceptible to the influence of air bubbles, it is preferable to search in a way that reduces the influence of air bubbles by removing the influence of air bubbles from the detection value using a noise filter, etc., using an interface meter with another detection method in combination, or making sure that the injection of micro-nano bubble water does not overlap with the measurement by the interface meter.

In the present invention, it is preferable that the method further includes adjusting the position or direction for spraying the water containing micro-nano bubbles. The spray position or direction may be changed along a predetermined path, or may be changed based on the search results. It is preferable that the spray position or direction includes a location where the amount of sludge accumulation is likely to exceed the upper limit. There are no particular limitations on the mechanism for changing the spray position or direction, and examples include a mechanism consisting of a movable arm, or a mechanism consisting of a combination of a pulley and a rail.

The amount of foaming in the circulating water, the turbidity or concentration of suspended solids in the circulating water, and/or the pH of the circulating water can be measured using known methods.

The amount of foaming of the circulating water can be measured, for example, by a scale or a bubble level meter provided on the side of the circulating water pit. The bubble level meter is not particularly limited in terms of the detection method, and examples include an optical level meter, an ultrasonic level meter, an impedance level meter, and a capacitance level meter. Of these, a capacitance level meter is preferred. In a small-sized circulating water pit, bubbles often occur on the entire surface of the liquid in the circulating water pit, so it is preferable to provide at least one bubble level meter. In a large-sized circulating water pit, bubbles may occur on a portion of the surface of the liquid in the circulating water pit, so it is preferable to install at least one bubble level meter in a location where bubbles are likely to occur. In a large-sized circulating water pit, a camera or the like is installed to monitor the entire surface of the liquid in the circulating water pit, and the distribution of bubble generation can be grasped, and the bubble level meter may be installed in an appropriate location accordingly. By using the liquid level meter 11 and the bubble level meter 10 in combination, the level of the interface between the foam and the liquid and the level of the surface of the foam can be grasped.
It can be assumed that the stronger the foam film that is generated, the greater the amount of foaming. Foam is generated by a combination of conditions such as the temperature, surface tension, and viscosity of the circulating water. Surface tension varies depending on the anionic and nonionic surfactants in the paint. Therefore, it is thought that the amount of water treatment agent in the circulating water and the amount of excess paint affect the amount of foaming.

The turbidity of the circulating water can be measured, for example, by visual comparison with a standard solution of known turbidity or by a turbidimeter. The concentration of suspended solids can be measured, for example, by an SS meter. SS is an abbreviation for suspended solids. Turbidity is classified into visual turbidity, transmitted light turbidity, scattered light turbidity, and integrating sphere turbidity in JIS K 0101 "Industrial Water Testing Methods". The turbidimeter or SS meter 13 is not particularly limited in terms of the detection method, and examples include (1) scattered light/transmitted light method, (2) surface scattered light method, (3) transmitted light method, (4) scattered light method, (5) integrating sphere method, and (6) fine particle counting method. Some SS meters display the SS concentration in a pseudo manner using a correlation equation between turbidity and SS.
In the present invention, the chromaticity of the circulating water may be measured as necessary. The chromaticity of the circulating water can be measured, for example, by a colorimeter. The chromaticity includes, for example, chromaticity based on platinum-cobalt and chromaticity based on a stimulus value Y and chromaticity coordinates x, y. Chromaticity based on platinum-cobalt is applied when the color is light yellow to yellowish brown due to a substance dissolved or present in a colloidal state in the sample. Chromaticity based on a stimulus value Y and chromaticity coordinates x, y is used when measuring samples of various other colors. Note that, by using a turbidity meter, values of turbidity and chromaticity can be obtained with the effects of mutual interference corrected.
Turbidity is affected by the amount, size, and color of suspended solids. Materials suspended in circulating water include flocs or sludge from excess paint, as well as water treatment agents made of poorly soluble components, so it is believed that the amount of these substances affects fluctuations in turbidity.

The pH of the circulating water can be measured, for example, with litmus paper or a pH meter 12. The pH affects corrosion of equipment, the life of aquatic animals and plants, and the growth of agricultural and marine products. The pH also affects the effectiveness of the water treatment agent mentioned above, specifically the amount of floc or sludge produced from excess paint, the settling rate, settling amount, floating rate, and floating amount. It is believed that various substances dissolved in the circulating water affect the fluctuations in pH.

The amount of foaming of the circulating water, the turbidity or concentration of suspended solids in the circulating water, and/or the pH of the circulating water can be measured at various positions.
The foaming amount of the circulating water can usually be measured for the circulating water in the circulating water pit. The turbidity or suspended solids concentration of the circulating water can be measured for the circulating water in the wet paint booth, the circulating water flowing from the wet paint booth toward the circulating water pit, the circulating water that has flowed into the circulating water pit and is mixed with the circulating water accumulated in the circulating water pit, the circulating water that has accumulated in the circulating water pit, the circulating water flowing from the circulating water pit toward the wet paint booth, the surface water, or the intake water.
The pH of the circulating water can be measured for the circulating water in the wet paint booth, the circulating water flowing from the wet paint booth toward the circulating water pit, the circulating water that has flowed into the circulating water pit and mixed with the circulating water accumulated in the circulating water pit, the circulating water that has accumulated in the circulating water pit, the circulating water flowing from the circulating water pit toward the wet paint booth, surface water, or the intake water.

In the present invention, the amount of water treatment agent added and/or the amount of micro-nano bubble water sprayed is adjusted based on the measured values of the foaming amount of the circulating water, the turbidity or suspended solids concentration of the circulating water, and/or the pH of the circulating water, so that the foaming amount of the circulating water, the turbidity or suspended solids concentration of the circulating water, and/or the pH of the circulating water are within a predetermined value range.
This adjustment can be performed by an ON-OFF control method, a P control method, a PI control method, a PID control method, a PD control method, a fuzzy control method, etc. In the ON-OFF control method, for example, when the measured value reaches or exceeds a predetermined value A, adjustment is made to start or increase the addition of a water treatment agent known to lower the value, or to stop or decrease the addition of a water treatment agent known to raise the value, and when the measured value falls below a predetermined value B, adjustment is made to start or increase the addition of a water treatment agent known to raise the value, or to stop or decrease the addition of a water treatment agent known to lower the value.
In the P control method, PI control method, PID control method, PD control method, and fuzzy control method, the addition of water treatment agent is started or increased, or stopped or decreased, based on the difference (ΔX) between the measured value _Xm and the target value _XT . P is a control algorithm that increases or decreases the amount of addition F by an amount ΔF _P proportional to ΔX, I increases or decreases the amount of addition F by an amount ΔF _I proportional to the integral value of ΔX, and D increases or decreases the amount of addition F by an amount ΔF _D proportional to the differential value of ΔX. For example, the PID control method is a combination of P, I, and D.
The fuzzy control method involves collecting rules such as "when condition A1, output B1,""when condition A2, output B2," and "when condition A3, output B3," calculating the degree of conformance of the state quantity X to each condition (A1, A2, and A3) using a membership function, cutting out output portions that exceed the degree of conformance from among the functions of the outputs (B1, B2, and B3) for the conditions, superimposing the functions of each output that have been cut, determining the maximum area, and determining the output corresponding to the center of gravity as the manipulated variable.

The present invention includes adjusting the amount of water treatment agent added and/or the amount of micro-nano bubble water sprayed (operation amount) in response to an event in a wet paint booth, instead of or in combination with the adjustment based on the above-mentioned measured value. The adjustment in response to an event can be performed so that the amount of foaming of the circulating water, the turbidity or suspended solids concentration of the circulating water, and/or the pH of the circulating water are within a predetermined value range. For example, since the amount of excess paint generated by painting one car in a certain wet paint booth is almost fixed, information on the number of cars painted per unit time can be transmitted to the control system to determine the extent to which the operation amount should be adjusted. In addition, since the amount of excess paint generated during non-steady operation associated with the start or stop of the wet paint booth can be empirically grasped, the event control system 3 can transmit a control signal 26 in response to an event such as the start or stop of the wet paint booth, and determine the extent to which the operation amount should be adjusted.

The water treatment device of the present invention is a multivariable process in which the input and output are the amount of water treatment agent added and/or the amount of micro-nano bubble water sprayed (multiple operation quantities), the amount of foaming of the circulating water, the turbidity or suspended solids concentration of the circulating water, and/or the pH of the circulating water, and events (multiple state quantities) as necessary. The adjustment in the present invention may determine the operation quantities using a distributed multivariable control method based on classical control theory (e.g., multiple loop control, cascade control, mutual interference compensation, etc.), or may determine the operation quantities using a centralized multivariable control method based on modern control theory. A distributed multivariable control method can be used from the viewpoint that it is easy to grasp the malfunction of the control system, and even if some of the control systems stop working due to a breakdown or failure, the remaining control systems can compensate, allowing relatively stable control. Specifically, the central control device processes the control signal 26 corresponding to the event, the control signal 17 for the amount of micro-nano bubble water sprayed, the control signal 18 based on the pH measurement, the control signal 19 based on the amount of foam generated, and the control signal 20 based on the turbidity measurement, and sends a command for the amount of supply to the supply pump or valve of the tank storing each water treatment agent. The amount of water treatment agent supplied may be monitored by a discharge sensor 15 or the like so that an abnormality such as a malfunction can be detected and a warning issued. If it is predicted that the amount of foaming will exceed the capacity of the circulating water pit due to a disturbance, a specified defoamer can be added manually or automatically.

The control system used in the present invention may be a method of control based on the values of state quantities measured or observed in the early stages of a multivariable process (feedforward control method), or a method of control based on the values of state quantities measured or observed in the later stages of a multivariable process (feedback control method). A control system that combines both may have both stable control and rapid control.

In the present invention, a priority order may be set for each control system in the distributed multivariate control method. For example, it is preferable from the viewpoints of process stability, low cost, etc. to perform the first priority control by a feedforward control method in response to an event, the second priority control by a feedback control method for keeping the pH within a predetermined range, and the third priority control by a feedback control method for keeping the foaming amount within a predetermined range.
Furthermore, the state of the control system can be monitored on-site by display on a control panel or the like, and can also be monitored remotely by transmitting information via a communication means.

The amount of water treatment agent added and/or the amount of micro-nano bubble water sprayed (operation amount) is adjusted by the control system described above, and the operation amount realized by the adjustment is, for example, as follows.
The amount of micro-nano bubbles supplied (amount of air supplied) is preferably 0.005 to 0.30 g, more preferably 0.05 to 0.15 g, per 1 g of excess paint (solid content).
The amount of the abhesor is, for example, 1 mg or more, more preferably 5 mg or more, per 1 L of circulating water, in the case of phenolic resin (solid content). From the viewpoint of suppressing excessive foaming and an increase in operating costs, the upper limit of the amount of the phenolic resin (solid content) added is preferably 1000 mg, more preferably 200 mg, per 1 L of circulating water. The amount of the phenolic resin (solid content) added is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, per surplus paint (solid content). The upper limit of the amount of the phenolic resin (solid content) added is preferably 100% by mass, more preferably 10% by mass, per surplus paint (solid content).

For example, in the case of a low molecular weight cationic polymer, the amount of coagulant (solid content) added is preferably 0.1 to 100 mg, preferably 0.3 to 30 mg, per 1 L of circulating water. The amount of low molecular weight cationic polymer (solid content) added is preferably 10 mass % or less, more preferably 2 mass % or less, relative to the excess paint (solid content). The lower limit of the amount of low molecular weight cationic polymer (solid content) added is preferably 1 mass %, more preferably 5 mass %, relative to the excess paint (solid content).

The amount of flocculant (solid content) added is, for example, in the case of a high molecular weight cationic polymer, preferably 0.1 to 10% by mass, more preferably 0.2 to 3% by mass, based on the excess paint (solid content). The amount of high molecular weight cationic polymer added is, for example, preferably 0.001 to 1 meq/L, more preferably 0.002 to 0.5 meq/L, as a colloid equivalent value for the circulating water. The addition of high molecular weight cationic polymer can prevent redispersion of flocs (floated sludge), and can also increase the efficiency of filtration and/or dewatering (sedimentation, centrifugation, etc.) that may be performed after the pressurized flotation treatment. The amount of anionic polymer (solid content), which is a type of flocculant, added is preferably 0.1 to 10% by mass, more preferably 0.2 to 3% by mass, based on the excess paint (solid content). The amount of amphoteric polymer (solid content), which is a type of flocculant, added is preferably 0.1 to 10% by mass, more preferably 0.2 to 3% by mass, relative to the excess paint (solid content).

1: Wet paint booth
2: Car counter or clock
3: Event control system
4. Central control unit
5: Communication network
6: Remote control
7:pH control system
8: Foam generation control system
9: Turbidity control system
10: Foam level gauge
11: Liquid level gauge
12:pH meter
13: Water treatment agent preparation tank
14: Liquid level gauge
15: Discharge sensor
16: Micro-nano bubble generator
17: Micro-nano bubble water injection volume control signal
18: Control signal based on pH measurement value
19: Control signal based on foam generation amount measurement value
20: Control signal based on turbidity measurement value
21: Sediment detection sensor
22: Water treatment agent supply amount adjustment mechanism
23:SS meter
24: Car
25: Circulating water pit
26: Control signal corresponding to an event
A: Circulating water
Au: Untreated circulating water
At: Treated circulating water

Claims (10)

Excess paint generated in wet painting booths is captured by circulating water,
The circulating water containing the captured excess paint is sent to a circulating water pit,
The circulating water is temporarily stored in a circulating water pit;
Water containing micro-nano bubbles is sprayed into the circulating water stored in the circulating water pit to encourage the sludge made from excess paint to float up,
removing all or a portion of the floating sludge from the circulating water, and then returning the circulating water from which the sludge has been removed from the circulating water pit to the wet paint booth;
and adding water treatment agents to the circulating water.
Adjusting the amount of water treatment agent added and/or the amount of water containing micro-nano bubbles sprayed in response to an event in the wet paint booth;
Measuring the amount of foaming of the circulating water and the pH of the circulating water; and
The method includes adjusting the amount of water treatment agent added and/or the amount of water containing micro-nano bubbles injected based on the measured values of the amount of foaming of the circulating water and the pH of the circulating water so that the amount of foaming of the circulating water and the pH of the circulating water are within a predetermined range,
The number average diameter of the micro-nano bubbles when sprayed into the circulating water is 0.1 μm to 100 μm,
Regarding the adjustment of the amount of the water treatment agent added and/or the amount of water containing micro-nano bubbles sprayed, the adjustment in response to an event in the wet paint booth takes precedence over the adjustment so that the pH of the circulating water falls within a predetermined range, and the adjustment so that the pH of the circulating water falls within a predetermined range takes precedence over the adjustment so that the foaming amount of the circulating water falls within a predetermined range.
How to treat circulating water in a wet paint booth. Measuring the turbidity or suspended solids concentration of the circulating water; and
2. The treatment method according to claim 1, further comprising adjusting an amount of a water treatment agent added and/or an amount of water containing micro-nano bubbles injected based on a measured value of the turbidity or the concentration of suspended solids of the circulating water so that the turbidity or the concentration of suspended solids of the circulating water falls within a predetermined value range . 3. The treatment method according to claim 1 or 2, wherein the event in the wet paint booth is start or stop of the wet paint booth, start or stop of painting, disposal of paint or paint washing liquid into circulating water, dump spray or undercoat, intermediate coat, or top coat. The treatment method according to any one of claims 1 to 3, in which water containing micro-nano bubbles is sprayed toward the bottom of the circulating water pit. Search for sludge made of excess paint that has accumulated at the bottom of the circulating water pit,
The treatment method according to any one of claims 1 to 4, further comprising adjusting a position or a direction for spraying water containing micro-nano bubbles based on the search result. Circulating water pit,
A drain for circulating water from the wet paint booth to the circulating water pit;
Micro-nano bubble generator,
A supply line for flowing circulating water from the circulating water pit to the wet paint booth;
A mechanism for adding a water treatment agent to the circulating water;
A measuring device for measuring the foaming amount of the circulating water and the pH of the circulating water; and
The present invention provides a wet paint booth having an adjustment device for adjusting the amount of water treatment agent added and/or the amount of water containing micro-nano bubbles sprayed, the adjustment device having a control algorithm for adjusting the amount of water treatment agent added and/or the amount of water containing micro-nano bubbles sprayed in response to an event in the wet paint booth, and a control algorithm for adjusting the amount of water treatment agent added and/or the amount of water containing micro-nano bubbles sprayed, based on the measurement values of the amount of foaming of the circulating water and the pH of the circulating water obtained by the measurement device, so that the amount of foaming of the circulating water and the pH of the circulating water are within a predetermined value range ,
The adjustment of the amount of the water treatment agent added and/or the amount of water containing micro-nano bubbles sprayed is configured so that the adjustment made in response to an event in the wet paint booth takes precedence over the adjustment made so that the pH of the circulating water falls within a predetermined range, and the adjustment made so that the pH of the circulating water falls within a predetermined range takes precedence over the adjustment made so that the foaming amount of the circulating water falls within a predetermined range,
The micro-nano bubble generator is installed so that a nozzle for spraying water containing micro-nano bubbles can spray water containing micro-nano bubbles from the circulating water stored in the circulating water pit.
The number average diameter of the micro-nano bubbles when sprayed into the circulating water is 0.1 μm to 100 μm.
Equipment for treating circulating water in wet paint booths. Further comprising a measuring device for measuring the turbidity or suspended solids concentration of the circulating water; and
7. The treatment device according to claim 6, wherein the adjustment device further has a control algorithm for adjusting the amount of water treatment agent added and/or the amount of water containing micro-nano bubbles injected, based on a measurement value of the turbidity or the concentration of suspended solids of the circulating water obtained by the measurement device, so that the turbidity or the concentration of suspended solids of the circulating water falls within a predetermined value range . The treatment device according to claim 6 or 7, wherein the water injection port containing micro-nano bubbles is installed so as to inject water containing micro-nano bubbles toward the bottom of the circulating water pit. The treatment device according to any one of claims 6 to 8, further comprising a sensor for detecting sludge consisting of excess paint accumulated at the bottom of the circulating water pit. The micro-nano bubble generator has a mechanism for adjusting the position or direction of a nozzle for spraying water containing micro-nano bubbles,
The treatment device according to any one of claims 6 to 9, wherein the adjustment device further comprises a control algorithm for adjusting a position or a direction of the nozzle of the water containing micro-nano bubbles.