JP5680901B2 - Waste water treatment method and waste water treatment equipment - Google Patents

Description

  The present invention relates to a wastewater treatment method and wastewater treatment equipment including at least a water-based paint.

  In recent years, from the viewpoint of reducing volatile organic compounds (VOC), there is an increasing trend of switching from a solvent paint using a volatile organic solvent as a solvent to an aqueous paint using water as a solvent. Water-based paints are generally water, resin (which is the main component of the coating film and becomes the coating film), organic solvents (those that dissolve and disperse the resin), pigments (those that color), surfactants, antifoaming agents, and freezing. Consists of an inhibitor, sagging inhibitor, rust inhibitor and the like. The organic solvent is generally composed of alcohols, esters, ketones, ether alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, and the like. Of these, generally, alcohols, esters, ketones, and ether alcohols are hydrophilic, and aliphatic hydrocarbons and aromatic hydrocarbons are hydrophobic.

  In the painting process using paint, various paints are applied to the object by spray painting or the like. However, the coating efficiency of the water-based paint sprayed on the object to be coated is not always perfect. For example, since the painting efficiency on the body of an automobile is about 60%, the remaining 40% is not used effectively. Therefore, in order to collect excess paint that has not been painted in a painting booth or the like, it is usually collected and removed with washing water. The washing water is recycled.

Since water-based paints are not easily separated from water due to their properties, they are accumulated in a state of being dissolved in flush water used for circulation, resulting in the following problems.
(A) Wastewater overflow from the aquarium due to foaming, environmental deterioration (b) BOD (Biochemical Oxygen Demand) component decays and a decaying odor occurs (c) Paint component to aquarium, piping, etc. (D) High concentration COD (Chemical Oxygen Demand) and high concentration BOD make it difficult to discharge.

  In order to solve these problems, chemical treatment and treatment by evaporation to dryness are conventionally performed (see, for example, Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 11-672 JP 2009-220047 A

  By the way, the present inventors examined a method for separating each of the waste water containing water-based paint by heating the waste water to evaporate the low boiling point components of the waste water and concentrating the high boiling point components. . In this treatment method, water containing evaporated low boiling point components is recovered and used again for wastewater treatment to prevent adhesion / sedimentation, foaming, decay, and the like of paint components on pipes and the like. I found out that I can do it. However, if the wastewater treatment is continuously performed, the paint scale adheres to the indirect heating part for heating the wastewater, and the heat transfer efficiency of the indirect heating part is reduced. There is a risk that it cannot be done.

  Then, the objective of this invention is providing the waste water treatment method and waste water treatment apparatus which can suppress adhesion of the paint scale to the indirect heating part installed in an evaporation concentrator.

The present invention is a wastewater treatment method including a water-based paint containing a resin that is a coating film component to be coated on an object to be coated , and the drainage by an evaporative concentrator provided with an indirect heating unit for heating the wastewater. to evaporate water containing low boiling point components in, with evaporation concentration step of concentrating the high-boiling components, when the evaporation process, the counter ion of the non-volatile neutralizing the charge of the resin into the drainage Add the drug you have.

Further, the present invention is a wastewater treatment method including a water-based paint containing a resin that is a coating film component to be coated on an object to be coated, and an evaporation concentrator provided with an indirect heating unit for heating the wastewater. the water containing low boiling point components in the wastewater is evaporated, with an evaporative concentration step of concentrating the high-boiling components, when the evaporation process is charged of the resin in concentrated water concentrated by the evaporation concentrator Add a drug with a non-volatile counterion to neutralize

Further, the present invention is a wastewater treatment apparatus including a water-based paint containing a resin that is a coating film component to be coated on an object to be coated , wherein the wastewater is heated to remove low-boiling components in the wastewater. comprising evaporating the water comprises a evaporation unit for concentrating the high boiling component, and means for adding an agent having a non-volatile counter ion for neutralizing the charge of the resin in the drainage, the.

Further, the present invention is a wastewater treatment apparatus including a water-based paint containing a resin that is a coating film component to be coated on an object to be coated , wherein the wastewater is heated to remove low-boiling components in the wastewater. the containing water is evaporated, the evaporation unit for concentrating the high boiling component, and means for adding an agent having a counter ion of the non-volatile neutralizing the charge of the resin in concentrated water concentrated by the evaporation means, Is provided.

  ADVANTAGE OF THE INVENTION According to this invention, adhesion of the paint scale to the indirect heating part installed in an evaporation concentrator can be suppressed.

It is a schematic diagram which shows an example of a structure of the waste water treatment equipment which concerns on embodiment of this invention. It is a schematic diagram which shows an example of a structure of the waste water treatment equipment which concerns on other embodiment of this invention. It is a schematic diagram which shows an example of a structure of the waste water treatment equipment which concerns on other embodiment of this invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  Drawing 1 is a mimetic diagram showing an example of the composition of the waste water treatment equipment concerning the embodiment of the present invention. A wastewater treatment apparatus 1 shown in FIG. 1 includes an aqueous paint drainage tank 10, an evaporative concentration machine 12 (evaporation concentration means), a concentrated water tank 14, a compressor 16, an evaporative water supply line 32 (heat recovery utilization means), and a heat exchanger 18. , Drainage pump 20, concentrated water pump 22, vacuum pump 24, drainage inflow line 26, concentrated water circulation line 28, concentrated water discharge line 30, evaporative water return line 34 (return means), exhaust line 36, auxiliary steam line 37, resin A drug addition line 39 having a non-volatile counter ion for neutralizing the charge of the resin (a drug addition means having a non-volatile counter ion for neutralizing the charge of the resin).

  The evaporation concentrator 12 used in the present embodiment is particularly limited as long as it has a structure capable of concentrating the high boiling point component by evaporating water containing the low boiling point component in the waste water by indirect heating. Although not intended, indirect heat exchange is performed indirectly between the evaporation section, where the evaporation takes place, and a heat source such as a heat transfer plate or heat transfer tube, between the heat source and the object to be heated. A heating unit. The evaporation concentrator 12 shown in FIG. 1 includes an evaporator 12a (evaporating unit), an indirect heating unit 38, an auxiliary steam line 37, and an auxiliary steam supply source. The indirect heating unit 38 installed in the evaporator 12a of the evaporation concentrator 12 is composed of a large number of heat transfer tubes, as described in, for example, JP-A-2004-237136 and JP-A-2008-188514, Each of the heat transfer tubes is provided so as to be horizontally oriented. In addition, an inlet header is provided at one end of each heat transfer tube, and an outlet header is provided at the other end, and the liquid to be heated outside the heat transfer tube is heated by heating steam passing through the inside of the heat transfer tube. Further, the evaporation concentrator 12 of the present embodiment is not necessarily limited to the above. For example, as described in JP 2009-090228 A, an evaporator and heat installed outside the evaporator You may provide the indirect heating part which is an exchanger. This heat exchanger has a steam inlet, a condensed water outlet, and a large number of horizontal and horizontal heat transfer tubes. And while the to-be-heated liquid passes the inside of a heat exchanger tube, the steam introduce | transduced from the steam inlet port heats to-be-heated liquid from the exterior of a heat exchanger tube. Moreover, as described in JP-A-5-84401, the indirect heating unit may have a hollow structure constituted by a hollow plate-like heating element or the like instead of the heat transfer tube. The shape of the indirect heating portion having such a hollow structure is not particularly limited as long as heat exchange is possible between the inside and the outside of the hollow structure.

  Here, the low boiling point component in the present embodiment is a component that evaporates with water under the pressure and temperature conditions for evaporation, and the high boiling point component does not evaporate with water under the pressure and temperature conditions for evaporation. Ingredients. For example, ethylene glycol monobutyl ether (commonly called butyl cellosolve), which is an aqueous coating solvent having a boiling point of 171 to 172 ° C. at atmospheric pressure, is a low-boiling component because it evaporates with water at 90 ° C. and 0.07 MPa.

  In the water-based paint drain tank 10, waste water containing at least the water-based paint is stored. One end of a drainage inflow line 26 is connected to the water-based paint drainage tank 10, and the other end is connected to the evaporator 12 a via a drainage pump 20 and a heat exchanger 18. Further, a chemical addition line 39 having a nonvolatile counter ion that neutralizes the charge of the resin is connected to the water-based paint drain tank 10. One end of the concentrated water circulation line 28 is connected to the lower side of the evaporator 12 a, and the other end is connected to the upper side of the evaporator 12 a through the concentrated water pump 22. Further, one end of a concentrated water discharge line 30 is connected to the concentrated water circulation line 28, and the other end is connected to the concentrated water tank 14. Moreover, one end of the evaporating water supply line 32 is connected above the evaporator 12a, and the other end is connected to the indirect heating part 38 (inlet side: inlet header, for example) via the compressor 16. Further, one end of the evaporating water return line 34 is connected to an indirect heating unit 38 (exit side: for example, an outlet header), and the other end is connected to the aqueous paint drainage tank 10 via the heat exchanger 18. Further, one end of the exhaust line 36 is connected to the evaporated water return line 34 between the heat exchanger 18 and the evaporator 12 a, and the other end is opened to the atmosphere via the vacuum pump 24. One end of the auxiliary steam line 37 is connected to the evaporating water supply line 32, and the other end is connected to an auxiliary steam supply source (not shown).

  Next, the operation of the waste water treatment apparatus 1 according to this embodiment will be described.

  The waste water containing the aqueous paint is stored in the aqueous paint drain tank 10. Water-based paints are generally water, resin (which is the main component of the coating film and becomes the coating film), organic solvents (those that dissolve and disperse the resin), pigments (those that color), surfactants, antifoaming agents, and freezing. Consists of an inhibitor, sagging inhibitor, rust inhibitor and the like. Examples of the resin include an anionic emulsion resin and a cationic emulsion resin. The organic solvent is generally composed of alcohols, esters, ketones, ether alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, and the like. An organic solvent etc. are mainly mentioned as a low boiling-point component of an aqueous coating material. Of these, generally, alcohols, esters, ketones, and ether alcohols are hydrophilic, and aliphatic hydrocarbons and aromatic hydrocarbons are hydrophobic. In addition, examples of the high-boiling component of the water-based paint include mainly resins, pigments, surfactants and antifoaming agents. In addition, the waste water containing the water-based paint may contain a solvent paint, a cleaning liquid, and the like.

  A drug having a non-volatile counter ion that neutralizes the charge of the resin is added to the wastewater in the aqueous paint drainage tank 10 via a drug addition line 39 having a non-volatile counter ion that neutralizes the charge of the resin. Drainage is adjusted to alkaline area. Since the neutralization effect cannot be obtained when the drug having a counter ion evaporates, it is preferably non-volatile and has a high boiling point. As a specific example of the chemical | medical agent which has such a counter ion, alkaline agents, such as sodium hydroxide and potassium hydroxide, can be mentioned with respect to anionic resin. In addition, when the resin is a cationic resin, an acid such as sulfuric acid can be given as a specific example of the drug having a counter ion.

  Drainage containing a water-based paint adjusted to an alkaline region (hereinafter sometimes simply referred to as drainage) is introduced into the heat exchanger 18 through a drainage inflow line 26 by a drainage pump 20. Then, the heat exchanger 18 exchanges heat between the waste water and steam discharged from the evaporator 12a (evaporated water containing low-boiling components). Here, since the evaporated water has a higher temperature than the waste water, the waste water is preheated. The preheated waste water is supplied to the evaporator 12 a through the waste water inflow line 26. As in the present embodiment, the waste water introduced into the evaporator 12a of the evaporator concentrator 12 can be preheated, and the waste water before being introduced into the evaporator 12a of the evaporator concentrator 12 and the evaporated water return line. It is preferable to install a heat exchanger 18 for exchanging heat with the evaporated water before being returned to the waste water by 34.

  The wastewater supplied to the evaporator 12a of the evaporator concentrator 12 is indirectly heated by the heat from the indirect heating unit 38 installed in the evaporator 12a of the evaporator concentrator 12. In the initial stage of operation, steam generated from the auxiliary steam supply source is supplied from the auxiliary steam line 37 to the indirect heating unit 38 (for example, inside each heat transfer tube), whereby the indirect heating unit 38 is heated and heated. The waste water is indirectly heated by the heat from the section 38. Here, since the inside of the evaporator 12a is depressurized by the vacuum pump 24, the water in the waste water and the low boiling point component (hereinafter may be referred to as water containing a low boiling point component) are at a saturated vapor pressure. Evaporates at an equal and relatively low temperature. On the other hand, the high boiling point component in the waste water is concentrated and stored as concentrated water containing the high boiling point component at the bottom. Concentrated water containing a high-boiling component is discharged from the evaporator 12a by the concentrated water pump 22, passes through the concentrated water circulation line 28, and is indirectly heated from the upper part of the evaporator 12a to the indirect heating unit 38 (for example, each heat transfer tube). Sprayed on the outer surface). Thereby, since the sprayed waste water (including concentrated water) becomes high temperature by the steam inside the indirect heating unit 38, low boiling point components in the waste water can be effectively evaporated on the surface of the indirect heating unit 38.

  Usually, the waste water containing the water-based paint evaporates in the evaporator 12a, the concentration of the high boiling point component proceeds, and the resin in the water-based paint is solidified and easily adheres to the indirect heating unit 38 as a coating film scale. As described above, the water-based paint contains a resin, and an acrylic resin is often used as the resin, and the acrylic resin has a carboxyl group or the like. If the drainage containing the water-based paint lacks counter ions for the carboxyl groups and the pH is neutral or acidic (that is, pH is 7 or less), for example, the carboxyl groups are not dissociated. Molecules are deposited and easily attached (fixed) to the indirect heating unit 38. On the other hand, since the counter ion with respect to the carboxyl group is sufficiently present in the wastewater containing the water-based paint and is in the alkaline region (that is, the pH is more than 7), the acrylic resin is dissolved in water and hardly adheres to the indirect heating unit 38. Become. In the present embodiment, an alkaline agent having a counter ion that neutralizes the charge of the alkaline resin is added to the waste water containing the aqueous paint by the alkaline agent addition means having a counter ion that neutralizes the charge of the alkaline resin, and the pH is alkaline. Therefore, the resin in the aqueous paint is solidified and is prevented from adhering to the indirect heating unit 38 as a paint scale. Further, if the counter ion that neutralizes the charge is volatile, it cannot evaporate and obtain a neutralizing effect, so it must have a high boiling point and be non-volatile. Thereby, since the fall of the heat transfer efficiency of the indirect heating part 38 is suppressed, the waste_water | drain containing a water-based coating material can fully be heated. As a result, a decrease in processing efficiency for separating the low boiling point component and the high boiling point component is suppressed, and a high concentration ratio can be maintained. In addition, the resin contained in the water-based paint is not limited to an acrylic resin. If the resin has an anionic property or a cationic property, the resin having a non-volatile counter ion that neutralizes the charge of the resin may be used. Similarly to the above, the same effect as described above can be obtained. For example, it may be an anionic resin in which a carboxyl group is added to a resin obtained by polymerizing butadiene, a cationic resin in which an amine group is added to a bisphenol A type epoxy resin, or a polyester resin that is commonly used as a resin for water-based paints. Alternatively, the resin may be anionic or cationic by adding a functional group to the melamine resin.

  Here, the chemical addition means having a non-volatile counter ion that neutralizes the charge of the resin can be configured as long as it can add a non-volatile counter ion that neutralizes the charge of the resin to the waste water. Is not particularly limited. For example, when the agent having a counter ion is an alkaline agent such as sodium hydroxide or potassium hydroxide and the degree of addition of the alkaline agent can be known by pH detection, the counter ion that neutralizes the charge of the resin is added. The chemical addition means has, for example, a pH sensor that detects the pH of the wastewater containing the aqueous paint (the pH sensor is installed in the aqueous paint drainage tank 10, the drainage inflow line 26, etc.), a tank that contains an alkaline agent, an alkaline agent An addition line, a pump for adjusting the addition amount of the alkaline agent, and the like can be employed. If the amount of the water-based paint discarded as wastewater by experiment and the amount of the alkaline agent for neutralizing the resin derived from the water-based paint are obtained in advance, the pH of the wastewater can be determined by such a configuration of the chemical addition means. Is detected by a pH sensor, and based on the detected value, the amount of the alkali agent added is adjusted by a pump, and the alkali agent is added to the waste water to neutralize the charge of the resin contained in the waste water containing the aqueous paint. be able to. Moreover, although the chemical | medical agent addition line 39 which has the non-volatile counter ion which neutralizes the charge of alkaline agent resin shown in FIG. 1 is connected to the water-based paint drainage tank 10, it is not restricted to this, It may be connected to the inflow line 26.

  Next, the water (steam) containing the low boiling point component evaporated by the evaporation concentrator 12 is supplied to the compressor 16 through the evaporation water supply line 32. The compressor 16 and the evaporated water supply line 32 function as heat recovery and utilization means for supplying the thermal energy of the evaporated water to an indirect heating unit 38 (for example, inside each heat transfer tube) installed in the evaporator 12a. is there. Specifically, the water (steam) containing the evaporated low boiling point component is compressed and heated by the compressor 16, passes through the evaporated water supply line 32, and is supplied to the indirect heating unit 38 (for example, each heat transfer tube). Thus, the indirect heating unit 38 is heated, and the wastewater stored in the bottom of the evaporator 12a is indirectly heated by the heat from the heated indirect heating unit 38. The supply of auxiliary steam may be stopped if the drainage can be sufficiently heated by the evaporated water compressed and heated by the compressor 16.

  Thus, by recovering and utilizing the thermal energy of the evaporated water, the energy can be effectively used, and the energy efficiency required for the wastewater treatment can be improved. In this embodiment, if it has a function which supplies at least one part of the thermal energy of the evaporated water to the indirect heating part 38 installed in the evaporator 12a, it will not necessarily be the compressor 16 and the evaporative water supply line 32. For example, an ejector or the like may be used instead of the compressor 16. The configuration of the compressor 16 used in the present embodiment is not particularly limited as long as it has the above function.

  It should be noted that the heat recovery and utilization means is a system for heating wastewater by effectively utilizing energy, and thus is not necessarily installed. In the case where no heat recovery and utilization means is installed, the evaporated water (returned from water vapor to the liquid) may be supplied directly to the heat exchanger 18.

  Next, the water (gas to liquid) containing the low boiling point component that has passed through the indirect heating unit 38 is introduced into the heat exchanger 18 from the evaporated water return line 34. The water (liquid) containing the low boiling point component is heat-exchanged with the waste water containing the water-based paint by the heat exchanger 18. Here, since the wastewater containing the water-based paint is at a lower temperature than the water containing the low boiling point component, the water containing the low boiling point component is cooled. The cooled water containing the low boiling point component is returned to the water-based paint drainage tank 10 through the evaporated water return line 34. Among the low-boiling components returned to the water-based paint drainage tank 10, there are those that have biological treatment inhibitory properties and contain components that dissolve the water-based paint. Is returned (supplied), so that bad odor due to decay, paint adhesion to the wall surface of the water-based paint drainage tank 10, each line, and the like can be suppressed. In this embodiment, the return means for collecting the evaporated water and returning it to the waste water is exemplified by the configuration of the evaporative water return line 34 alone, but is not limited to this. It is good also as a structure etc. which were installed in the return line 34. Moreover, in this embodiment, although the evaporative water return line 34 has taken the structure connected to the water-based paint drainage tank 10 as an example, the structure etc. which were connected to the waste_water | drain inflow line 26 may be sufficient.

  A part of the concentrated water containing the high boiling point component passing through the concentrated water circulation line 28 passes through the concentrated water discharge line 30 and is stored in the concentrated water tank 14. The concentrated water (including the high boiling point component) stored in the concentrated water tank 14 is preferably evaporated to dryness by an evaporating and drying apparatus such as a drier in that the apparatus can be a non-drainage system.

  In this way, by collecting the water containing evaporated low-boiling components and using it again for wastewater treatment, it is possible to improve the energy efficiency required for the treatment, and the water tank by the adhesion, sedimentation and foaming of the paint components to the piping etc. The wastewater overflow from the water, the prevention of environmental deterioration, the increase in the salt concentration in the water due to the use of chemicals can be suppressed, and a low-cost treatment can be performed.

  In the present embodiment, the inside of the evaporator 12a is depressurized by the vacuum pump 24. However, the evaporator 12a only needs to be able to heat the waste water and evaporate the water containing the low-boiling components. It is not necessary to depressurize the interior of the interior of the interior by the vacuum pump 24. Furthermore, in this embodiment, it is preferable that the concentrated water is circulated by the concentrated water pump 22 in terms of efficiently evaporating the low boiling point component, but it is not always necessary to circulate the concentrated water.

  The heating temperature of the waste water inside the evaporator 12a is appropriately set according to the types of low boiling point components, high boiling point components, etc. in the waste water, but it is 60 to 100 ° C. in that it suppresses foaming that occurs during heating of the waste water. The range of 80-95 degreeC is more preferable.

  In the present embodiment, at the initial operation of the wastewater treatment apparatus 1 or when the capacity of the compressor 16 is low, the heat recovery and utilization by the compressor 16 is not sufficiently performed, and the wastewater is not sufficiently heated. Separation of the boiling point component and the high boiling point component may not be performed efficiently. Therefore, in the initial operation of the wastewater treatment apparatus 1 or when the capacity of the compressor 16 is low, the auxiliary steam generated by the auxiliary steam supply source is supplied from the auxiliary steam line 37 to the indirect heating unit 38 in the evaporator 12a, It is preferable to use for heating of waste water. For example, a small boiler or the like may be used as an auxiliary steam supply source, and the auxiliary steam generated in the small boiler may be used. If there is excess waste steam in the factory, the equipment that generates the waste steam is supported. As the steam supply source, steam generated in the facility may be used.

  FIG. 2 is a schematic diagram illustrating an example of a configuration of a wastewater treatment apparatus according to another embodiment of the present invention. In the waste water treatment apparatus 2 shown in FIG. 2, the same components as those in the waste water treatment apparatus 1 shown in FIG. In the waste water treatment apparatus 2 shown in FIG. 2, a chemical addition line 39 having a non-volatile counter ion that neutralizes the charge of the resin is connected to the evaporator 12a. Then, through a drug addition line 39 having a non-volatile counter ion that neutralizes the charge of the resin, a drug having a non-volatile counter ion that neutralizes the charge of the resin is added to the concentrated water concentrated in the evaporator 12a. The Moreover, the chemical | medical agent addition line 39 which has the non-volatile counter ion which neutralizes charge of resin is not restricted to the case where it connects to the evaporator 12a, For example, you may connect to the concentrated water circulation line 28.

  When the agent having a counter ion is an alkali agent such as sodium hydroxide or potassium hydroxide and the degree of addition of the alkali agent can be known by pH detection, the agent having a counter ion that neutralizes the charge of the resin The adding means includes, for example, a pH sensor that detects the pH of the wastewater containing the water-based paint (the pH sensor is installed in the water-based paint drainage tank 10, the drainage inflow line 26, etc.), a tank that contains an alkali agent, and an alkali agent addition line. Further, it is possible to adopt a configuration such as a pump for adjusting the addition amount of the alkali agent. If the amount of the water-based paint discarded as wastewater by experiment and the amount of the alkaline agent for neutralizing the resin derived from the water-based paint are obtained in advance, the pH of the wastewater can be determined by such a configuration of the chemical addition means. Is detected by a pH sensor, and based on the detected value, the amount of the alkali agent added is adjusted by a pump, and the alkali agent is added to the waste water to neutralize the charge of the resin contained in the waste water containing the aqueous paint. be able to.

  Also with the configuration shown in the present embodiment, the resin in the aqueous paint is solidified and is prevented from adhering to the indirect heating unit 38 as a paint scale. Thereby, since the fall of the heat transfer efficiency of the indirect heating part 38 is suppressed, the waste_water | drain containing a water-based coating material can fully be heated. As a result, since the fall of the processing efficiency which isolate | separates a low boiling point component and a high boiling point component is suppressed, a high concentration rate can be maintained.

  FIG. 3 is a schematic diagram illustrating an example of a configuration of a wastewater treatment apparatus according to another embodiment of the present invention. In the waste water treatment device 3 shown in FIG. 3, the same reference numerals are given to the same components as those of the waste water treatment device 1 shown in FIG. The waste water treatment apparatus 3 shown in FIG. 3 includes an evaporating water discharge line 40.

  In the waste water treatment apparatus 3 shown in FIG. 3, one end of the evaporated water discharge line 40 is connected to the evaporated water return line 34, and the other end is connected to the concentrated water discharge line 30. In this embodiment, in order to obtain a more stable non-drainage system, a part of the evaporated water is stored in the concentrated water tank 14 from the evaporated water discharge line 40 through the concentrated water discharge line 30, and then evaporated to dryness together with the concentrated water. It is preferable to make it. In the present embodiment, it is only necessary to evaporate and dry a part of the evaporating water. For example, the evaporating water discharge line 40 may be directly connected to an evaporating and drying apparatus such as a dehydrator or a dryer. Alternatively, it may be connected to the concentrated water tank 14 and evaporated to dryness with concentrated water by an evaporation / drying apparatus.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

  In Example 1, the wastewater treatment apparatus shown in FIG. 1 was used, and wastewater containing a water-based paint was concentrated 20 times. During the operation of the waste water treatment apparatus, sodium hydroxide was added to the waste water containing the aqueous paint to adjust the pH of the waste water to 10. Table 1 summarizes test conditions for 20-fold concentration of wastewater.

  In Example 2, the test was performed under the same conditions as in Example 1 except that the pH of the wastewater was adjusted to 11.

  In the comparative example, the test was performed under the same conditions as in Example 1 except that pH adjustment was not performed.

First, the overall heat transfer coefficient of the indirect heating part before adhesion of the paint scale was 3000 kcal / m ² / ° C./h. And the overall heat transfer coefficient of the indirect heating part of the comparative example which did not perform pH adjustment of waste_water | drain is 1500 kcal / m < ² > / (degreeC) / h, and the overall heat transfer coefficient of the indirect heating part fell. On the other hand, the overall heat transfer coefficient of the indirect heating unit of Example 1 in which the pH of the waste water was adjusted to 10 was 2000 kcal / m ² / ° C./h, and the decrease in the overall heat transfer coefficient of the indirect heating unit was suppressed. . Moreover, the overall heat transfer coefficient of the indirect heating part of Example 2 which adjusted pH of the waste_water | drain to 11 was 3000 kcal / m < ² > / (degreeC) / h, and the fall of the overall heat transfer coefficient of the indirect heating part was not seen. In this way, by adding sodium hydroxide, which is a non-volatile counter ion that neutralizes the charge of the resin to the waste water, and adjusting it to the alkaline region, it becomes difficult for the paint scale to adhere to the indirect heating part, and heat transfer efficiency is improved. The decrease was suppressed.

  1, 2, 3 Wastewater treatment equipment, 10 Water-based paint drainage tank, 12 Evaporation concentrator, 12a Evaporator, 14 Concentrated water tank, 16 Compressor, 18 Heat exchanger, 20 Drain pump, 22 Concentrated water pump, 24 Vacuum pump, 26 Wastewater inflow line, 28 Concentrated water circulation line, 30 Concentrated water discharge line, 32 Evaporated water supply line, 34 Evaporated water return line, 36 Exhaust water line, 37 Auxiliary steam line, 38 Indirect heating unit, 39 Neutralize resin charge Drug addition line with non-volatile counterion, 40 evaporative water discharge line.

Claims (4)

A wastewater treatment method for wastewater containing a water-based paint containing a resin that is a coating film component to be coated on an object ,
Evaporating and concentrating the high-boiling components by evaporating water containing the low-boiling components in the waste water by an evaporative concentrator equipped with an indirect heating unit for heating the waste water,
The evaporator during the concentration step, waste water treatment method characterized by adding an agent having a counter ion of the non-volatile neutralizing the charge of the resin to the wastewater. A wastewater treatment method for wastewater containing a water-based paint containing a resin that is a coating film component to be coated on an object ,
Evaporating and concentrating the high-boiling components by evaporating water containing the low-boiling components in the waste water by an evaporative concentrator equipped with an indirect heating unit for heating the waste water,
The evaporator during the concentration step, waste water treatment method characterized by adding an agent having a counter ion of the non-volatile neutralizing the charge of the resin in concentrated water concentrated by the evaporation device. A wastewater treatment apparatus for wastewater containing a water-based paint containing a resin that is a coating film component to be coated on an object ,
Evaporative concentration means for heating the waste water to evaporate water containing the low boiling point component in the waste water and condensing the high boiling point component;
Waste water treatment apparatus, characterized in that it comprises, means for adding an agent having a counter ion of the non-volatile neutralizing the charge of the resin to the wastewater. A wastewater treatment apparatus for wastewater containing a water-based paint containing a resin that is a coating film component to be coated on an object ,
Evaporative concentration means for heating the waste water to evaporate water containing the low boiling point component in the waste water and condensing the high boiling point component;
Waste water treatment apparatus, characterized in that it comprises, means for adding an agent having a non-volatile counter ion for neutralizing the charge of the resin in concentrated water concentrated by the evaporation means.

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