JP6645536B2 - Method and control device for controlling chemical injection of circulating water treatment chemical in wet coating booth - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method and an apparatus for properly controlling a chemical for treating a circulating water treatment chemical in a wet coating booth.

  2. Description of the Related Art In a coating process in the automobile industry, home appliances, metal products manufacturing industry, and the like, various paints are spray-painted. Paints used industrially are roughly classified into solvent-based paints and water-based paints, and each paint is used alone or in combination.

  Aqueous paints are broadly classified into three types: water-soluble, dispersion-type, and emulsion-type. However, since all use water as a solvent (some solvents may be used in combination), there is no flammability. In recent years, in particular, the range of application has been expanding because of its advantages such as safety and hygiene and no risk of pollution caused by solvents.

  In the coating process in various industries, the yield of the paint sprayed on the object to be coated is not necessarily 100%. For example, in the automobile industry, it is about 60 to 80%, and 40 to 20% of the paint used is in the next step. Is the surplus paint to be removed. In order to collect the excess paint sprayed excessively, water is washed in a wet coating booth, and the washing water is circulated.

In this case, the water-based paint is soluble or dispersed in water, and solid-liquid separation is difficult. Therefore, the water-based paint remains in the circulating water of the wet coating booth and accumulates, causing the following problem.
(A) The circulating water becomes highly viscous and highly viscous, increasing the load of the circulating pump.
(B) Precipitated and insolubilized paint, dust other than paint, and SS components cause blockage failure of nozzles and piping systems, and adhesion failure to water film plates and the like.
(C) Foaming disorder occurs.
(D) The circulating water has a high COD and a high BOD, so that it rots, and the working environment is deteriorated due to odor.
(E) Due to high COD and high BOD, wastewater treatment becomes difficult, and the load on the treatment equipment increases.

In order to solve such a problem, conventionally, a treatment agent is added to circulating water to coagulate and separate excess paint in the circulating water.
Patent Document 1 describes that a phenolic resin and a cationic polymer are used in combination as a treatment agent for efficiently coagulating a paint in a circulating water of a wet coating booth containing an aqueous paint and / or a solvent-based paint. Have been. By using a phenolic resin and a cationic polymer together, an effective treatment can be performed by the following mechanism.

  That is, when a phenolic resin is dissolved in an alkaline aqueous solution or the like and injected into circulating water of a wet coating booth, the phenolic resin is dispersed in a dissolved state or in a colloidal state. At this time, if a cationic polymer is present, the phenolic resin is charge-neutralized and coagulates and becomes insoluble. On the other hand, the paint dissolved or colloidally dispersed in the circulating water is also charged and neutralized by the cationic polymer to be coagulated and insolubilized, but when the phenolic resin is insolubilized by the cationic polymer, the coagulated paint is involved. It flocks in the form of an ellipse and agglomerates. The floc of phenolic resin aggregated in a form involving paint becomes particles of a certain size, so it is easy to separate and remove from circulating water, and it is easy to separate and remove by flotation, centrifugation, filtration, etc. Can be.

In the treatment of the circulating water in the wet coating booth, it is important to add the treatment chemical in an appropriate amount for the paint contained in the circulating water. Therefore, conventionally,
(1) During the painting time, dosing only while the conveyor carrying the product is moving (2) Doing the dosing according to the quantity while counting the number of production (3) Time to discard paint Therefore, a method of performing drug injection during this time zone is performed separately from (1) and (2). These are methods for injecting medicine based on information that can be predicted in advance, and can be said to be feedforward control.
In addition, information on whether the medicine is actually being ejected and whether there is a remaining amount in the tank is also important for ensuring proper medicine injection.It is important to record the ejection amount and remaining amount of the medicine with a sensor. It is said that it is desirable to carry out the operation in combination with the above-described feedforward control.

On the other hand, there are condition fluctuations that are difficult to predict in advance, such as changing the type of paint and discarding or throwing away paint or thinner, and feed forward control cannot perform appropriate chemical injection control for these changes. .
For this reason, if the quality of the circulating water in the wet coating booth is constantly measured, and if the fluctuations can be implemented together with the chemical injection control (feedback control) of the circulating water treatment chemical, more stable chemical injection control can be achieved. It is thought that stable treatment of circulating water is possible.

JP-A-2004-337671

In a wet coating booth circulating water system using a water-based paint or a water-based paint and a solvent paint mixed paint, the amount of paint in the circulating water may suddenly increase unexpectedly.In this case, in the conventional feed forward control, this sharp Unable to cope with the increase in paint volume, circulating water foams, bubbles overflow from the wet coating booth, poor water intake from the circulating water tank to the sludge collection device, poor coagulation due to the polymer flocculant, etc. I do.
In the field of water treatment, it has been customary to detect foaming and inject an antifoaming agent in accordance with the foaming.However, the defoaming agent only erases the foam. Insufficient amount of circulating water treatment chemicals when paint load increases due to the inability to perform proper treatment (non-adhesion, agglomeration (primary agglomeration), floating on pits) of paint in response to unexpected increase in paint load It is not a fundamental measure.
On the other hand, it is not preferable to constantly add a circulating water treatment chemical in anticipation of an increase in paint load, because the chemical cost increases.

  The present invention solves the above-mentioned problems of the prior art, and provides a method and an apparatus capable of appropriately coping with an unexpected increase in paint load in the circulating water of a wet-type painting booth and performing appropriate chemical injection control of a treatment chemical. The purpose is to do.

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, there is a correlation between the amount of foaming of the circulating water and the paint load of the circulating water. It has been found that the paint can be properly treated by detecting the increase in the amount of foam and controlling the injection of the circulating water treatment chemical according to the increase in the amount of foam.
That is, the present invention provides the following.

[1] A method for controlling the chemical injection into a circulating water of a treatment agent for tackifying, agglomerating or floating paint in the circulating water of a wet coating booth, wherein the circulating water is controlled based on a foaming amount of the circulating water. Controlling the addition of said treating agent to a wet coating booth circulating water treating agent.

[2] A method for controlling chemical injection of a circulating water treatment chemical in a circulating water system for receiving paint-containing water from a wet painting booth into a circulating water tank and feeding the water treated in the circulating water tank to the wet painting booth. The method according to [1], wherein the height of the foam in the circulating water tank is measured as the amount of water foaming.

[3] When the measured value of the foam height becomes equal to or greater than a predetermined value A set in advance, the addition of the treatment agent is started or the amount of the treatment agent is increased [2]. Chemical injection control method of the wet coating booth circulating water treatment chemical according to the above.

[4] When the measured value of the bubble height becomes equal to or less than a predetermined value B set in advance, the addition of the processing agent is stopped or the amount of the processing agent added is reduced [3]. Chemical injection control method of the wet coating booth circulating water treatment chemical according to the above.

[5] The wet method according to any one of [1] to [4], wherein the treatment agent is a phenolic resin and an organic coagulant, or a phenolic resin, an organic coagulant and a polymer flocculant. Chemical injection control method for paint booth circulating water treatment chemicals.

[6] Addition of an antifoaming agent is started when the measured value of the foam height becomes equal to or more than a predetermined value C set in advance, and the measured value of the foam height becomes equal to or less than the predetermined value D set in advance. The method according to any one of [3] to [5], wherein the addition of the defoaming agent is sometimes stopped.

[7] A wet coating booth is a chemical injection control device for applying a treatment agent to the circulating water for making the paint non-tacky, coagulating or floating in the circulating water, and a foaming amount measuring means for measuring the foaming amount of the circulating water. And a control means for inputting a measured value of the foaming amount measuring means and controlling the addition of the treatment agent to the circulating water based on the measured value. Drug dosing control device.

[8] A chemical injection control device for a circulating water treatment chemical in a circulating water system that receives paint-containing water from a wet coating booth into a circulating water tank and sends water treated in the circulating water tank to the wet coating booth. The chemical injection control device for a wet coating booth circulating water treatment chemical according to [7], wherein the water foaming amount measuring means is a foam sensor for measuring a foam height in the circulating water tank.

[9] When the measured value of the bubble height becomes equal to or more than a predetermined value A set in advance, the control means starts a signal for adding the processing agent or issues a signal for increasing the amount of the processing agent to be added. The chemical injection control device for a wet coating booth circulating water treatment chemical according to [8], wherein the chemical spray control device outputs the output.

[10] The control means outputs a signal for stopping the addition of the processing agent or decreasing the amount of the processing agent when the measured value of the foam height becomes equal to or less than a predetermined value B set in advance. The chemical dispensing control device for a wet coating booth circulating water treatment chemical according to [9], wherein:

[11] The wet method according to any one of [7] to [10], wherein the treatment agent is a phenolic resin and an organic coagulant, or a phenolic resin, an organic coagulant and a polymer flocculant. Injection booth circulating water treatment chemical injection control device.

[12] The control means starts the addition of the antifoaming agent when the measured value of the foam height becomes equal to or more than a predetermined value C set in advance, and the measured value of the foam height is set to a predetermined value. A signal for stopping the addition of the defoaming agent is output when the value becomes equal to or less than D, and the chemical injection control device for a wet coating booth circulating water treatment chemical according to any one of [9] to [11], .

  ADVANTAGE OF THE INVENTION According to this invention, since it can respond | correspond to the unexpected increase of the paint load of the circulating water of a wet-type coating booth appropriately, and can perform appropriate chemical | medical-agent injection | pouring control of a processing chemical | chemical, stabilization of a process can be achieved.

FIG. 3 is a system diagram showing a chemical injection control device for a wet coating booth circulating water treatment chemical used in Example 1. 4 is a graph showing a change over time of a bubble height in a circulating water tank in Example 1.

  Hereinafter, embodiments of the present invention will be described in detail.

The method for controlling chemical injection of a wet coating booth circulating water treatment chemical according to the present invention is a method for controlling chemical injection into the circulating water of a processing chemical for making a paint in the wet coating booth circulating water non-adhesive, coagulating or floating. And controlling the addition of the treatment agent to the circulating water based on the foaming amount of the circulating water.
The chemical pouring control device for a wet coating booth circulating water treatment chemical according to the present invention is a chemical pouring control device for treating a chemical in the wet coating booth circulating water to prevent the paint from sticking, coagulating or floating, into the circulating water. A foaming amount measuring means for measuring the foaming amount of the circulating water; and a control means for controlling the addition of the treatment agent to the circulating water based on the measured value of the foaming amount measuring means. And characterized in that:

  In the present invention, the foaming amount of the circulating water is defined as the foam height of the liquid level in the circulating water tank that receives and treats the paint-containing water from the wet painting booth and then feeds the water to the wet painting booth (hereinafter simply referred to as “foam height”). Is sometimes measured.), And the bubble height can be measured by, for example, an ultrasonic bubble sensor or the like.

  In addition, in the chemical injection control of the circulating water treatment chemical in the present invention, specifically, the foam height is measured, and the measured value of the foam height is set to a predetermined value A (hereinafter referred to as “upper limit A”). In some cases, the addition of the treatment agent is started or the amount of the treatment agent is increased, and the measured value of the foam height is set to a predetermined value B (hereinafter referred to as “lower limit value B”). It is preferable to stop the addition of the processing chemical or reduce the amount of the processing chemical to be added when the following occurs.

  Here, the predetermined values A and B are not particularly limited, and are appropriately determined according to the quality of the circulating water, the fluctuation range of the paint load, and the like. Although not particularly limited, for example, the predetermined value A is set in a range of 10 to 100 cm, and the predetermined value B is set in a range of 2 to 20 cm.

  As described above, there is a correlation between the amount of circulating water foaming and the proper treatment of the paint, and in the present invention, it is particularly suitable to use a treatment agent capable of preventing sticking, agglomeration, and floating with a chemical injection amount such that bubbles disappear. Therefore, as the circulating water treatment agent used in the present invention, a phenol-based agent that inactivates anionic surfactants and nonionic surfactants in paint that causes bubbles, and that makes the paint non-tacky and aggregates A combination of a resin and an organic coagulant is preferred. It is preferable to further use a polymer coagulant in combination with these, because the stability of the treatment can be further improved.

In the present invention, it is preferable to add an antifoaming agent in an emergency such as when a large amount of foam is generated in order to quickly reduce the generated foam. In this case, for example, a foam height standard is set in two stages. However, a chemical injection method in which a circulating water treatment chemical is added in the first stage and an antifoaming agent is added in the second stage is also effective.
Specifically, the addition of the antifoaming agent is started when the measured value of the foam height becomes equal to or more than the predetermined value C set in advance, and the measured value of the foam height becomes equal to or less than the predetermined value D set in advance. Chemical injection control that sometimes stops the addition of an antifoaming agent is mentioned.

  Here, the predetermined value C is preferably larger than the predetermined value A, for example, in a range of the predetermined value A + (2 to 100) cm. Further, the predetermined value D is preferably set in a range of the predetermined value A- (0 to 50) cm.

  Hereinafter, preferred embodiments of the present invention will be described in more detail.

<Phenolic resin>
The phenolic resin used in the present invention is a condensate of a phenol such as a monohydric phenol such as phenol, cresol or xylenol and an aldehyde such as formaldehyde or a modified product thereof, and the phenolic resin before crosslinking and curing. Resins. Specific examples include the following.

[1] Condensate of phenol and formaldehyde [2] Condensate of cresol and formaldehyde [3] Condensate of xylenol and formaldehyde [4] Obtained by alkylating the phenolic resin of the above [1] to [3] Alkyl-modified phenolic resin [5] polyvinyl phenol

  These phenolic resins may be of novolak type or resol type. In addition, a phenolic resin having a weight average molecular weight of about 1,000 to 10,000 can be suitably used.

  One of these phenolic resins may be used alone, or two or more of them may be used in combination.

  Since such a phenolic resin is hardly soluble in water, it is preferably used as a solution or an emulsion by dissolving or dispersing it in a water-soluble solvent. Examples of the solvent used include ketones such as acetone, esters such as methyl acetate and the like, water-soluble organic solvents such as alcohols such as methanol, alkaline aqueous solutions, amines, etc., and preferably caustic soda (NaOH) and caustic potash (KOH). Dissolved in an alkaline agent such as

  When the phenolic resin is used as an alkaline aqueous solution, the alkaline aqueous solution preferably has an alkaline agent concentration of 1 to 25% by mass and a phenolic resin concentration of 1 to 50% by mass. When the phenolic resin concentration is high, the phenolic resin may be dissolved by heating to about 70 to 80 ° C.

  In the present invention, when the phenolic resin is controlled by chemical injection according to the foam height, the measured value of the foam height of the phenolic resin is not less than the upper limit value A by ON / OFF control according to the foam height. In such a case, the addition of the phenolic resin may be started, and the addition of the phenolic resin may be stopped when the lower limit B or less is obtained. The amount of the phenolic resin added may be increased when the amount of the phenolic resin is equal to or more than the upper limit A, and the amount of the phenolic resin may be decreased when the amount of the phenolic resin is equal to or less than the lower limit B.

The amount of the phenolic resin added to the circulating water varies depending on the control method and the quality of the circulating water (the type of paint in the circulating water, the content of the paint, and the like). When the measured value is equal to or higher than the upper limit A, the addition of 1 to 100 mg / L to the circulating water as an active ingredient amount (solid content of the phenolic resin) is started. Preferably, the addition of the phenolic resin is stopped.
When the amount of the phenolic resin to be added is increased or decreased, if the measured value of the foam height is not less than the upper limit A in the range of 1 to 100 mg / L with respect to the circulating water as the amount of the active ingredient, it is added. It is preferable to increase the amount, and when the amount falls below the lower limit B, reduce the amount of addition.

<Organic coagulant>
As the organic coagulant, cationic coagulants are preferable. Examples thereof include cationic polymers such as (dimethylaminoethyl methacrylate) and DADMAC (diallyldimethylammonium chloride), but are not limited thereto.

  One of these organic coagulants may be used alone, or two or more thereof may be used in combination.

  In the present invention, when the organic coagulant is controlled by chemical injection according to the foam height, the measured value of the foam height of the organic coagulant is not less than the upper limit A by ON / OFF control according to the foam height. In this case, the addition of the organic coagulant may be started, and the addition of the organic coagulant may be stopped when the lower limit B or less is reached. The addition amount of the organic coagulant may be increased when the amount becomes equal to or more than the upper limit value A, and may be decreased when the amount becomes equal to or less than the lower limit value B.

The amount of the organic coagulant added to the circulating water varies depending on the control method and the quality of the circulating water (the type of paint in the circulating water, the content of the paint, and the like). When the measured value is equal to or higher than the upper limit A, the organic coagulant starts adding 0.2 to 20 mg / L to the circulating water as an active ingredient amount, and when the measured value is equal to or lower than the lower limit B, It is preferred to stop adding the organic coagulant.
When the amount of the organic coagulant added is increased or decreased, when the measured value of the foam height is not less than the upper limit A in the range of 0.2 to 20 mg / L with respect to the circulating water as the amount of the active ingredient. It is preferable to increase the amount of addition, and to decrease the amount of addition when the amount becomes equal to or less than the lower limit B.

<Polymer flocculant>
In the present invention, a phenolic resin and an organic coagulant are added together with a polymer coagulant comprising a water-soluble polymer having a weight average molecular weight of usually more than 1,000,000, preferably 5,000,000 or more. It is preferable to further coarsen the flocculated floc of the paint by the coagulant with the polymer flocculant.
In this case, as the polymer flocculant, one or more known anionic polymer flocculants, cationic polymer flocculants, amphoteric polymer flocculants and the like can be used.

When a polymer flocculant is used, its addition amount is appropriately determined in the range of 0.1 to 10% by mass, preferably 0.5 to 2% by mass with respect to the excess paint so as to obtain a good flocculating effect. do it.
As for the polymer flocculant, as in the case of the phenolic resin and the organic coagulant, the chemical injection may be controlled in accordance with the foam height, or may be added in a fixed amount.

  In the present invention, in the case where the polymer coagulant is controlled by chemical injection according to the foam height, the polymer coagulant is ON / OFF controlled according to the foam height, and the measured value of the foam height is not less than the upper limit A. , The addition of the polymer flocculant may be started, and the addition of the polymer flocculant may be stopped when the lower limit B or less is reached. The addition amount of the polymer flocculant may be increased when the measured value of the polymer exceeds the upper limit value A, and the addition amount of the polymer flocculant may be decreased when the measured value becomes equal to or less than the lower limit value B.

The amount of the polymer flocculant added to the circulating water varies depending on the control method and the quality of the circulating water (the type of paint in the circulating water, the content of the paint, etc.). If the measured value of is equal to or more than the upper limit A, the addition of the polymer flocculant is started at 0.2 to 20 mg / L with respect to the circulating water as the amount of the active ingredient. Preferably, the addition of the polymer flocculant is stopped.
When the amount of the added polymer flocculant was increased or decreased, the measured value of the foam height became the upper limit A or more in the range of 0.2 to 20 mg / L with respect to the circulating water as the amount of the active ingredient. In such a case, it is preferable to increase the amount of addition, and to decrease the amount of addition when the amount falls below the lower limit B.

<Defoaming agent>
The defoaming agent is not particularly limited, and any defoaming agent conventionally used for wet coating booth circulating water can be appropriately selected and used. As the antifoaming agent, for example, a hydrophobic organic solvent, a fatty acid polyvalent metal salt, a hydrophobic inorganic powder, an antifoaming nonionic surfactant, or the like can be used.

  Examples of the hydrophobic organic solvent include paraffinic hydrocarbons, naphthenic hydrocarbons, and petroleum solvents. Examples of the fatty acid polyvalent metal salt include lauric acid, palmitic acid, stearic acid, oleic acid, and erucic acid. Metal salts of fatty acids such as magnesium, aluminum, calcium, iron, zinc, nickel, barium and the like.

  Examples of the hydrophobic inorganic powder include hydrophobic silica, alumina, and magnesium oxide. Examples of the nonionic surfactant include fatty acid esters such as glycerin fatty acid ester, sorbitan fatty acid ester, and polyethylene glycol fatty acid ester, and polyethylene. Examples thereof include glycols, polyoxyethylene polyoxypropylene (pluronic type / tetronic type), and ether types such as polyoxyethylene alkyl ether.

  One of these defoamers may be used alone, or two or more thereof may be used in combination.

  In the present invention, when the antifoaming agent is controlled by chemical injection according to the foam height, the defoaming agent is ON / OFF controlled according to the foam height, and the measured value of the foam height is equal to or greater than the predetermined value C described above. It is preferable to start the addition of the defoamer when it becomes, and to stop the addition of the defoamer when the above-mentioned predetermined value D or less, in this case, the amount of the defoamer added is It depends on the control method and the quality of the circulating water (the type of paint in the circulating water, the content of the paint, etc.). For example, when the measured value of the bubble height becomes a predetermined value C or more, It is preferable to start the addition of 1 to 100 mg / L and stop the addition of the antifoaming agent when the addition becomes equal to or less than the predetermined value D.

<Drug injection point>
There are no particular restrictions on the phenolic resin and organic coagulant injection point, and it may be added to any part of the circulating water system.However, in the normal case, the return water from the circulating water tank or wet painting booth to the circulating water tank It is added to piping or both. Further, the phenolic resin and the organic coagulant may be added to the same place or may be added to separate places.

  The polymer flocculant is usually added to a sludge collecting device or a piping for supplying circulating water from a circulating water tank to the sludge collecting device. The antifoaming agent is preferably added to a circulating water tank.

  The pH of the coagulation treatment system is preferably about 6.0 to 8.5 from the viewpoint of preventing corrosion of the equipment and the effect characteristics of the cationic polymer added as an organic coagulant with respect to the pH. Therefore, when the pH falls outside this range and becomes low, it is preferable to adjust the pH by adding an alkali agent. Usually, the range does not deviate to the high pH side in the actual machine, but if it deviates extremely, the pH may need to be adjusted.

<Recovery of flocculated floc>
By the addition of the phenolic resin and the organic coagulant, and further the addition of the polymer flocculant, the paint in the circulating water quickly becomes tack-free, flocculates and floats to generate flocs. For separation and recovery of flocs generated by aggregation, a method using flotation, wedge wire, rotary screen, bar screen, cyclone, centrifugal separator, filtration device, or the like can be employed.

  The sludge separated and recovered by such a method is subjected to incineration and landfill after gravity dehydration or after dehydration by an ordinary method.

<Applicable circulating water>
The present invention is applicable to the treatment of circulating water in which the amount of foaming greatly increases due to a rapid increase in the paint load, such as wet coating booth circulating water containing water-based paint, or wet coating booth circulating water containing water-based paint and solvent-based paint. Can be applied effectively.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

  In the following, the following chemicals were used as treatment chemicals for circulating water.

Alkaline solution of phenolic resin: NaOH aqueous solution of phenol / formaldehyde polycondensate (weight average molecular weight 8,000) (phenolic resin concentration: 30% by mass, NaOH concentration: 10% by mass, pH: 12 to 13) (hereinafter referred to as " Phenolic resin solution ").
Cationic polymer: aqueous solution of alkylamine-epichlorohydrin condensate (weight average molecular weight: 100,000) (cationic polymer concentration: 50% by mass)
Polymer flocculant: W / O emulsion of acrylamide / 2 (acryloyloxy) ethyltrimethylammonium chloride copolymer (weight average molecular weight 7,000,000) (active ingredient concentration 40% by mass)
Antifoaming agent: Mineral oil based antifoaming agent mainly composed of petroleum hydrocarbon compounds

[Example 1]
In the wet coating booth circulating water treatment apparatus shown in FIG. 1, in accordance with the present invention, the chemical injection control of the treatment chemical based on the foam height was performed.
This wet coating booth circulating water treatment chemical dispensing control device uses a wet coating booth circulating water with an average circulating water paint concentration of 100 mg / L using an automobile paint (water-based paint) at a circulating water volume of 10 m ³ / min. And the paint load may rise suddenly and irregularly when the paint is thrown away or discarded.

FIG. 1 is a partial configuration diagram of the circulating water tank 1 showing an installation portion of the ultrasonic bubble sensor 2 of the circulating water tank 1 and a chemical injection control unit.
A rod 4 stands upright from above the float 3 on the liquid surface of the circulating water tank 1. The rod 4 is vertically movably inserted into the ring portions 5a, 5b on the distal ends of the support members 5A, 5B. The base ends of the support members 5A and 5B are fixed to the side wall of the circulating water tank 1.
The upper portion 4a of the rod 4 is bent downward in an L-shape, and the ultrasonic bubble sensor 2 is attached to the lower end thereof.
The measurement value of the ultrasonic bubble sensor 2 is input to the controller 6.

  The phenolic resin solution is added to the circulating water in the circulating water tank 1 by the pipe 11 and the chemical injection pump 11P, the cationic polymer is added by the pipe 12 and the chemical injection pump 12P, and defoaming is performed by the pipe 13 and the chemical injection pump 13P. The agent is added. The polymer flocculant is added to a sludge collecting device (not shown) by the pipe 14 and the chemical injection pump 14P. A chemical injection signal is output from the controller 6 to the chemical injection pumps 11P, 12P, 13P, and 14P, and the chemical injection control based on the measured value of the foam height is performed.

Before the injection control according to the present invention, the following feedforward control was performed.
Feedforward control: Number control (measures the number of vehicles passing on the belt conveyor, and after measuring a certain number, injects necessary chemicals for that number)
While performing the feedforward control described above, the chemical injection control according to the present invention was performed by the following feedback control.
Feedback control: Based on the measured value of the foam height, each medicine was controlled by the following ON / OFF criteria.
Foam height A = 10 cm: phenolic resin solution + cationic polymer + polymer flocculant ON
Bubble height B = 9 cm: phenolic resin solution + cationic polymer + polymer flocculant OFF
Foam height C = 15cm: Defoamer ON
Foam height D = 10cm: Defoamer OFF

FIG. 2 shows the change over time of the measured value of the foam at this time.
The following can be seen from FIG.
Before the start of production, a certain amount of paint entered the circulating water tank due to spraying of paint, so foaming occurred before the start of production, and after the start of production, chemicals were added by controlling the number of units, but there was a shortage of chemicals for the waste blowing. Therefore, foaming continued (no control (comparative example)).
When the phenolic resin solution, cationic polymer and polymer flocculant and defoamer are added by ON / OFF control based on the foam height, foaming is suppressed, and an appropriate amount for an irregular amount of discarded spray paint , And the treatment was stabilized (with control (Example)).

DESCRIPTION OF SYMBOLS 1 Circulating water tank 2 Ultrasonic foam sensor 3 Float 4 Rod 5A, 5B Support member 6 Controller

Claims (10)

A method for controlling the chemical injection into the circulating water of a treatment agent for preventing adhesion of the paint in the wet coating booth circulating water, coagulation or floating,
The paint comprises a water-based paint,
The treatment agent is a phenolic resin, an organic coagulant and a polymer flocculant,
A method for controlling chemical injection of a circulating water treatment chemical in a wet coating booth, wherein the addition of the treatment chemical to the circulating water is controlled based on the foaming amount of the circulating water.   A method for controlling chemical injection of a circulating water treatment chemical in a circulating water system for receiving paint-containing water from a wet coating booth into a circulating water tank and feeding the water treated in the circulating water tank to the wet coating booth, wherein the circulating water foaming is performed. The method according to claim 1, wherein the foam height in the circulating water tank is measured as the amount.   The method according to claim 2, wherein the addition of the treatment agent is started or the amount of the treatment agent is increased when the measured value of the foam height becomes equal to or more than a predetermined value A set in advance. Chemical injection control method for circulating water treatment chemical in wet coating booth.   The method according to claim 3, wherein when the measured value of the bubble height becomes equal to or less than a predetermined value B, the addition of the treatment agent is stopped or the amount of the treatment agent is reduced. Chemical injection control method for circulating water treatment chemical in wet coating booth. The addition of the antifoaming agent is started when the measured value of the foam height becomes equal to or more than a predetermined value C set in advance, and when the measured value of the foam height becomes equal to or less than the predetermined value D set in advance, dosing control method of a wet spray booth circulating water treatment agent according to claim 3 or 4, characterized in that stopping the addition of antifoam. A wet coating booth is a chemical injection control device for applying a treatment agent for preventing tackiness, agglomeration or floating of paint in circulating water to the circulating water,
The paint comprises a water-based paint,
The treatment agent is a phenolic resin, an organic coagulant and a polymer flocculant,
Foaming amount measuring means for measuring the foaming amount of the circulating water; control means for controlling the addition of the treatment agent to the circulating water based on the measured value of the foaming amount measuring means, based on the measured value; A chemical injection control device for a wet coating booth circulating water treatment chemical, comprising: A chemical injection control device for a circulating water treatment chemical in a circulating water system that receives paint-containing water from a wet coating booth into a circulating water tank and sends the water treated in the circulating water tank to the wet coating booth, 7. The apparatus according to claim 6 , wherein the amount measuring means is a foam sensor for measuring a foam height in the circulating water tank. The control means, when the measured value of the foam height becomes equal to or more than a predetermined value A set in advance, outputs a signal to start adding the processing agent or to increase the amount of the processing agent to be added. The chemical spraying control apparatus for a chemical agent for treating circulating water in a wet coating booth according to claim 7 , characterized in that: The control means may stop adding the treatment agent or output a signal for decreasing the amount of the treatment agent when the measured value of the foam height becomes equal to or less than a predetermined value B set in advance. The chemical injection control device for a wet coating booth circulating water treatment chemical according to claim 8 , characterized in that: The control means starts the addition of an antifoaming agent when the measured value of the foam height becomes equal to or more than a predetermined value C set in advance, and the measured value of the foam height becomes equal to or less than a predetermined value D set in advance. 10. The chemical pouring control device for a wet coating booth circulating water treatment chemical according to claim 8, wherein a signal for stopping the addition of the antifoaming agent is output when the anti-foaming agent is added.

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