WO2015136992A1

WO2015136992A1 - Method for recycling cooling water effluent and recycling apparatus

Info

Publication number: WO2015136992A1
Application number: PCT/JP2015/051685
Authority: WO
Inventors: 邦洋早川; 隆彦内田
Original assignee: 栗田工業株式会社
Priority date: 2014-03-14
Filing date: 2015-01-22
Publication date: 2015-09-17
Also published as: TW201600468A; CN106029580A; CN106029580B; SG11201607245XA; MY175667A; JP2015174030A; TWI642635B; JP5773013B1

Abstract

In recycling a cooling water effluent through RO membrane treatment, the present invention reduces the cost of water treatment, enhances the recovery ratio of water, and stabilizes the treatment of water, said cooling water effluent including blow water in a circulating cooling water system. The present invention is a water recycling method which comprises subjecting a cooling water effluent discharged from a circulating cooling water system to treatment in a water reclamation system including both a pretreatment membrane and an RO membrane and returning the treated water to the circulating cooling water system, wherein a dispersant that can permeate the pretreatment membrane is added in the circulating cooling water system as a dispersant for dispersing scale components. In other words, this method comprises using a dispersant-permeable membrane as the pretreatment membrane precedent to the RO membrane and thereby enabling a dispersant added in the circulating cooling water system to be effectively utilized also in the water reclamation system. Thus, the present invention can reduce the cost of water treatment, enhance the recovery ratio of water, and stabilize the treatment of water.

Description

Cooling discharge water recovery method and recovery device

The present invention relates to a method and an apparatus for recovering cooling effluent in a cooling facility used in industrial processes such as building air conditioning, chemical industry, paper industry, steel industry, and electric power industry.

∙ Scale failure occurs on heat transfer surfaces and piping that come into contact with water such as cooling water and boiler water. In particular, from the standpoint of resource saving and energy saving, when high concentration operation is performed by reducing the amount of cooling water discharged (blow) out of the system, salts dissolved in water are concentrated and the heat transfer surface is corroded. And scales as a sparingly soluble salt. If the scale adheres to the wall surface of the apparatus, a serious obstacle occurs in the operation of the boiler and heat exchanger, such as a decrease in thermal efficiency and blockage of piping.

In recent years, the movement to use water as effectively as possible has been prominent for the purpose of saving water and saving energy. In the case of high concentration operation, there is a limit to suppress the precipitation of scale.

取り組み Efforts are being made to collect cooling water blow water with a recovery system and return the treated water to the cooling tower. As the recovery system, a system that removes salts (ions) with a reverse osmosis membrane (RO membrane) and returns treated water to a cooling tower is generally used. For example, the following systems have been studied (Patent Documents 1 to 3).

System 1: Agglomeration-> Sand filtration-> Safety filter-> RO membrane System 2: Agglomeration-> Sand filtration-> Pretreatment membrane-> RO membrane System 3: Agglomeration-> Pressurization flotation-> Sand filtration-> Safety filter-> RO membrane System 4: Decarbonation tower → Pretreatment membrane → RO membrane System 5: RO membrane

System 5 is a simple system using only the RO membrane device, but the turbidity contained in the blow water clogs the RO membrane, so that stable treatment is difficult.

As in the systems 1 to 4, the RO membrane treatment can be stabilized by agglomeration treatment before the RO membrane or removing turbidity in the blown water with the pretreatment membrane. However, the blow water contains a dispersant added in the circulating cooling water system, and this dispersant inhibits the aggregation treatment. For this reason, in the agglomeration treatment of the systems 1 to 3, the amount of the flocculant added for the treatment is very large.

In the RO membrane device, a dispersing agent is required to disperse the scale components and stabilize the treatment with a high water recovery rate. However, since the dispersing agent in the blown water is removed by the aggregation treatment, It is necessary to add a dispersant to the RO membrane water supply in order to stabilize the scale dispersion and treatment in the membrane.

Even in the system 4 in which the turbidity in the blown water is removed by the pretreatment membrane without performing the agglomeration treatment, the dispersant in the blown water is removed by the pretreatment membrane. It is necessary to add a dispersant to the RO membrane water supply.

JP 2003-1256 A JP 2002-18437 A JP 2009-297600 A

In the conventional water recovery system, it is necessary to add a dispersant to the RO membrane water supply for the stable operation of the RO membrane device, and the cost and work for that increase the processing cost.

The present invention relates to a cooling drainage recovery method that reduces the water treatment cost and improves and stabilizes the water recovery rate when recovering the cooling drainage water such as blow water of the circulating cooling water system by performing RO membrane treatment. It is another object of the present invention to provide a recovery device.

The present inventors obtained the following knowledge as a result of intensive studies to solve the above problems. When cooling discharge water such as blow water of the circulating cooling water system is treated with the RO membrane to recover the water, the pretreatment membrane of the RO membrane is a permeating dispersant added in the circulating cooling water system, and the circulating cooling water system The dispersant added in the cooling discharge water can be effectively used as a dispersant for the RO membrane by permeating the pretreatment membrane, so that the addition of the dispersant in the water recovery system is not required or dispersed. The additive amount can be reduced. Thereby, while reducing water treatment cost, the improvement and stabilization of a water recovery rate can be aimed at.

The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] Discharge water from the circulating cooling water system to which a dispersant for dispersing scale components is added is treated with a water recovery system including a pretreatment membrane and a reverse osmosis membrane, and the treated water is returned to the circulating cooling water system. A method for recovering cooling discharge water, wherein the dispersant permeates the pretreatment membrane in the circulating cooling water system.

[2] The method for recovering cooling effluent according to [1], wherein the pretreatment film has a permeability of the dispersant calculated by the following formula of 80% or more.
Permeability = (dispersant concentration of pretreated membrane permeated water / dispersant concentration of pretreated membrane feed water) × 100

[3] The method for recovering cooling drainage water according to [1] or [2], wherein the pretreatment membrane is a microfiltration membrane or an ultrafiltration membrane.

[4] The method of recovering cooling drainage water according to any one of [1] to [3], wherein the pH of the water supplied to the pretreatment film is 5 or more.

[5] The method for recovering cooling effluent according to any one of [1] to [4], wherein the pretreatment film has a molecular weight cut-off of 30,000 or more.

[6] The method for recovering cooling effluent according to any one of [1] to [5], wherein the dispersant is a polymer having a sulfonic acid group and a carboxyl group.

[7] In [6], the dispersant is methacrylic acid and / or acrylic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid and / or 2-acrylamido-2-methylpropanesulfonic acid. A method for recovering cooling effluent, which is a copolymer obtained by copolymerization of

[8] The method for recovering cooling effluent according to any one of [1] to [7], wherein the pH of the reverse osmosis membrane feed water is adjusted to 4.0 to 7.5.

[9] In any one of [1] to [8], the concentration of the dispersant in the reverse osmosis membrane feed water is measured, and the dispersion is added to the reverse osmosis membrane feed water so that the dispersant concentration becomes a predetermined concentration. A method for recovering cooling effluent, comprising adding an agent.

[10] In any one of [1] to [9], the conductivity of one or more of the discharged water, the reverse osmosis membrane water supply and the reverse osmosis membrane concentrated water is measured, and the measured value of the conductivity is obtained. Accordingly, the method for recovering the cooling effluent is characterized by adjusting the water recovery rate of the reverse osmosis membrane.

[11] In any one of [1] to [10], the dispersant concentration of the discharged water and / or reverse osmosis membrane water supply is measured, and the water of the reverse osmosis membrane is measured according to the measured value of the dispersant concentration. A method for recovering cooling effluent, wherein the recovery rate is adjusted.

[12] A method for recovering cooling discharged water according to any one of [1] to [11], wherein a polymer compound having a phenolic hydroxyl group is added to the discharged water.

[13] In any one of [1] to [12], when the water recovery system is stopped, the reverse osmosis membrane permeated water is circulated, or pure water or deionized water is passed through the reverse osmosis membrane. A cooling drainage recovery method characterized by stopping the water recovery system after performing an operation of discharging concentrated water out of the system.

[14] A pretreatment membrane device through which drained water from the circulating cooling water system is passed, a reverse osmosis membrane device through which the permeated water of the pretreatment membrane device is passed, and a permeated water of the reverse osmosis membrane device In the cooling drain water recovery apparatus having a return means for returning to the circulating cooling water system, the circulating cooling water system has a dispersing agent adding means for adding a dispersing agent for dispersing the scale component to the aqueous system, and the dispersing agent is An apparatus for recovering cooling effluent, which passes through a pretreatment membrane.

[15] The cooling wastewater recovery device according to [14], wherein the pretreatment film has a permeability of the dispersant calculated by the following formula of 80% or more.
Permeability = (dispersant concentration of pretreated membrane permeated water / dispersant concentration of pretreated membrane feed water) × 100

[16] The cooling drainage recovery apparatus according to [14] or [15], wherein the pretreatment membrane is a microfiltration membrane or an ultrafiltration membrane.

[17] The cooling wastewater recovery device according to any one of [14] to [16], wherein the pH of the water supplied to the pretreatment film is 5 or more.

[18] The cooling wastewater recovery device according to any one of [14] to [17], wherein the pretreatment film has a molecular weight cut-off of 30,000 or more.

[19] The cooling wastewater recovery device according to any one of [14] to [18], wherein the dispersant is a polymer having a sulfonic acid group and a carboxyl group.

[20] In [19], the dispersant is methacrylic acid and / or acrylic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid and / or 2-acrylamido-2-methylpropanesulfonic acid. An apparatus for recovering cooling effluent, which is a copolymer obtained by copolymerization of

[21] In any one of [14] to [20], there is provided a cooling drainage recovery apparatus, characterized by having pH adjusting means for adjusting the pH of the reverse osmosis membrane feed water to 4.0 to 7.5 .

[22] In any one of [14] to [21], the dispersant concentration measuring means for measuring the dispersant concentration of the water supplied to the reverse osmosis membrane, and the dispersant concentration measured by the dispersant concentration measuring means And a cooling agent recovery means for adding the dispersing agent to the reverse osmosis membrane water supply so that the concentration of water becomes a predetermined concentration.

[23] In any one of [14] to [22], conductivity measuring means for measuring one or more of the discharged water, reverse osmosis membrane water supply, and reverse osmosis membrane concentrated water, and the conductivity measurement And a water recovery rate adjusting means for adjusting the water recovery rate of the reverse osmosis membrane according to the measured value of the means.

[24] In any one of [14] to [23], the dispersant concentration measuring means for measuring the dispersant concentration of the discharged water and / or the reverse osmosis membrane water supply, and the measured value of the dispersant concentration measuring means And a water recovery rate adjusting means for adjusting the water recovery rate of the reverse osmosis membrane.

[25] The apparatus for recovering cooling effluent according to any one of [14] to [24], further comprising a coagulant aid adding means for adding a phenolic hydroxyl group to the effluent.

[26] In any one of [14] to [25], the reverse osmosis membrane device is a permeated water circulating means for circulating the reverse osmosis membrane permeated water upstream of the reverse osmosis membrane device, or pure water or deionized water. Means for passing water through the reverse osmosis membrane device, and concentrated water discharge means for draining the reverse osmosis membrane concentrated water out of the system. Control to circulate water in the previous stage, or to pass pure water or deionized water, and to stop the cooling drainage recovery device after performing an operation to discharge the reverse osmosis membrane concentrated water out of the system Means for Collecting Cooled Drainage Water

According to the present invention, the cooling discharge water is treated with the pretreatment membrane before the RO membrane, so that the turbidity in the cooling drainage water can be removed and the subsequent RO membrane treatment can be stabilized.

Moreover, in the present invention, the dispersing agent added in the circulating cooling water system and contained in the cooling discharge water permeates through the pretreatment membrane, so that the dispersing agent is effectively used as a dispersing agent for the RO membrane. can do. For this reason, unlike the conventional system, it is not necessary to re-add the dispersant removed in the previous stage of the RO membrane, and the efficiency can be improved economically and in terms of processing operation, and the processing cost is greatly reduced. Can do. And the dispersion | distribution agent which permeate | transmitted the pre-processing film | membrane can be aimed at stabilization of RO membrane process and the improvement of a water recovery rate.

For this reason, according to the cooling drain water recovery method and recovery device of the present invention, it is possible to prevent the scale failure of the RO membrane device with a simpler system and perform stable water recovery over a long period of time. .

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

<Cooling discharge water>
In the present invention, cooling discharge water used for water recovery treatment typically includes blow water from a cooling tower, but is not limited to blow water, and the present invention includes all discharges discharged from a circulating cooling water system. Can be applied to water. For example, part or all of the circulating cooling water may be extracted from the circulating piping of the circulating cooling water system and treated according to the present invention, and then returned to the circulating cooling water system. In addition, it is possible to collect water from the discharged water branched and discharged from the side filter and light filter pipes.

In the present invention, such cooling discharge water is treated as water to be treated and sequentially treated by the pretreatment membrane device and the RO device, and the treated water is returned to the circulating cooling water system.

<Strainer>
The cooling discharge water can be treated as it is in the pretreatment membrane device, but since the cooling discharge water may contain coarse turbidity and foreign matter, a strainer is provided in the front stage of the pretreatment membrane device. It is preferable to perform turbidity treatment in the pretreatment membrane device after removing these in advance with a strainer. Operation is possible even if the strainer is omitted, but in this case, the pretreatment film may be damaged by coarse turbidity or foreign matter in the cooling discharge water.

As the strainer, an automatic strainer that performs a cleaning process automatically is particularly preferably used.

The shape of the strainer is not particularly limited, and any shape such as a Y shape or a bucket shape can be used.

The pore size of the strainer is preferably 100 to 500 μm. When the pore size of the strainer is smaller than 100 μm, the strainer is severely blocked. When the pore diameter of the strainer exceeds 500 μm, there is a high possibility that coarse turbidity or foreign matter that has passed through the strainer will damage the pretreatment film.

代わり A filter such as a spool filter or a pleated filter may be used instead of the strainer. A strainer is preferable in terms of replacement frequency and cleaning efficiency.

<Pretreatment membrane device>
The cooled discharged water or the cooled discharged water after the turbidity treatment by the strainer is then processed by the pretreatment membrane device.

The pretreatment membrane device is for removing turbidity and colloidal components in the cooling discharge water that cause membrane contamination of the RO membrane device. It is a microfiltration membrane (MF membrane) and ultrafiltration membrane (UF membrane). Can be used. The membrane type of the pretreatment membrane device is not particularly limited, and a hollow fiber type or spiral type membrane filtration device can be employed. There is no restriction | limiting also in the filtration system of a pretreatment membrane apparatus, Any system of internal pressure filtration, external pressure filtration, crossflow filtration, and total amount filtration is applicable.

The molecular weight cutoff of the UF membrane, which is a pretreatment membrane, is preferably 30,000 or more. If the molecular weight cut off of the UF membrane is smaller than 30,000, the dispersant in the cooling discharge water cannot be permeated, and it may be necessary to add the dispersant again before the RO membrane device. Although there is no restriction | limiting in particular in the upper limit of the molecular weight cut off of a UF membrane, If it is 1,000,000 or less, the polymeric polysaccharide etc. which may cause the obstruction | occlusion of RO membrane in cooling discharge water can be removed. The pore size of the MF membrane as the pretreatment membrane is preferably about 0.1 to 0.01 μm for the same reason as the molecular weight cut off of the UF membrane.

In the pretreatment film, the transmittance of the below-described dispersant calculated by the following formula is preferably 80% or more, particularly 85% or more. When the transmittance of the dispersant in the pretreatment film is lower than the above lower limit, the effect of the present invention cannot be obtained effectively. The upper limit of the transmittance of the dispersant in the pretreatment film is usually 100%.
Permeability = (dispersant concentration of pretreated membrane permeated water / dispersant concentration of pretreated membrane feed water) × 100

In order to obtain the above-described dispersant permeability, it is preferable to use a suitable dispersant described later as the dispersant, and in the pretreatment membrane device, the pH of the feed water of the pretreatment membrane is 5 or more. When the pH of the feed water of the pretreatment membrane is lower than 5, even if a polymer having a sulfonic acid group and a carboxyl group, which will be described later, is used as a dispersant, the transmittance of the pretreatment membrane is lowered, and the effect of the present invention is obtained. It may not be possible. The pH of the feed water for the pretreatment membrane may be 5 or more, and the upper limit is not particularly limited. Usually, cooling discharge water such as cooling tower blow water has a pH of 8 to 10, usually about 8 to 9, and it is preferably treated as it is with a pretreatment membrane device.

<Dispersant>
In the present invention, the dispersant added to the circulating cooling water system permeates the pretreatment membrane.

As this dispersant, a polymer having a sulfonic acid group and a carboxyl group is preferably used.
Dispersant dissociates and the function as a dispersant becomes higher as the pH is higher, but in the RO membrane device at the rear stage of the pretreatment membrane device, it is concentrated in the RO membrane device when the pH is high. Since calcium and the like are easily deposited as scales, the treatment is performed under low pH conditions as described later. In the RO membrane apparatus under such a low pH condition, if the dispersant has only a carboxyl group and does not have a sulfonic acid group, it becomes insoluble and cannot function as a dispersant. For this reason, it is preferable to use a polymer having a sulfonic acid group and a carboxyl group as the dispersant.

As a polymer having a sulfonic acid group and a carboxyl group suitable as a dispersant, a copolymer of a monomer having a sulfonic acid group and a monomer having a carboxyl group, or, further, these monomers And terpolymers with other monomers copolymerizable therewith.

Examples of the monomer having a sulfonic acid group include conjugated diene sulfonic acids such as 2-methyl-1,3-butadiene-1-sulfonic acid, and sulfonic acid groups such as 3- (meth) allyloxy-2-hydroxypropanesulfonic acid. Unsaturated (meth) allyl ether monomer, 2- (meth) acrylamide-2-methylpropanesulfonic acid, 2-hydroxy-3-acrylamidepropanesulfonic acid, styrenesulfonic acid, methallylsulfonic acid, vinylsulfone Acid, allyl sulfonic acid, isoamylene sulfonic acid, or salts thereof, preferably 3-allyloxy-2-hydroxy-1-propanesulfonic acid (HAPS), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) ). As the monomer having a sulfonic acid group, one type may be used alone, or two or more types may be mixed and used.

As the monomer having a carboxyl group, acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, vinyl acetic acid, atropic acid, maleic acid, fumaric acid, itaconic acid, hydroxyethylacrylic acid or a salt thereof, preferably Examples include acrylic acid and methacrylic acid. The monomer which has a carboxyl group may be used individually by 1 type, and 2 or more types may be mixed and used for it.

Examples of monomers copolymerizable with these monomers include amides such as N-tert-butylacrylamide (N-tBAA) and N-vinylformamide.

As the dispersant suitable for the present invention, acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) are particularly used in a ratio of AA: AMPS = 70 to 90:10 to 30 (molar ratio). Copolymerized copolymer, amides such as AA, AMPS, N-tert-butylacrylamide (N-tBAA), AA: AMPS: amides = 40 to 90: 5 to 30: 5 to 30 (molar ratio) ) Copolymerized at a ratio of AA and 3-allyloxy-2-hydroxypropanesulfonic acid (HAPS) at a ratio of AA: HAPS = 70 to 90:10 to 30 (molar ratio). However, the present invention is not limited to these.

The polymer having a sulfonic acid group and a carboxyl group preferably has a weight average molecular weight of 1,000 to 30,000. If the weight average molecular weight of the polymer is less than 1,000, the dispersion effect is insufficient. When the weight average molecular weight of the polymer exceeds 30,000, it is difficult to permeate the pretreatment membrane, and the polymer itself is adsorbed on the pretreatment membrane or the RO membrane, which may cause membrane clogging.

The amount of the dispersant added in the circulating cooling water system is 3 to 30 mg / concentration as the concentration of the active ingredient (that is, the above polymer) from the viewpoints of the dispersion effect and economy in the cooling tower, and further the dispersion effect in the RO membrane water supply. L, particularly 5 to 20 mg / L is preferred. There are no particular restrictions on the method of adding the dispersant and the location of addition.

As the dispersant, in addition to the above-described polymer having a sulfonic acid group and a carboxyl group, other polymer or a phosphoric acid compound such as phosphonic acid may be used as long as a sufficient dispersion effect can be obtained. it can. As for the dispersant, a scale component that can be generated from the quality of the raw water of the circulating cooling water system is identified, and a type of dispersant that can prevent the generation of the dispersant may be added so as to obtain a concentration at which an effect can be obtained.

<RO membrane device>
The treated water (pretreated membrane permeated water) after the cooling discharged water has been treated with the aforementioned pretreatment membrane device is then desalted with the RO membrane device.

The type of RO membrane of the RO membrane device is not particularly limited, and is appropriately determined depending on the quality of the cooling discharge water to be treated (the quality of raw water supplied to the circulating cooling water system or the concentration rate in the circulating cooling water system). The RO membrane has a desalination rate of 80% or more, particularly 85% or more. When the desalting rate of the RO membrane is lower than this, desalting efficiency is poor, and treated water (permeated water) with good water quality cannot be obtained. As the material of the RO membrane, any material such as a polyamide composite membrane or a cellulose acetate membrane can be used. There is no restriction | limiting in particular also about the shape of RO membrane, Any things, such as a hollow fiber type and a spiral type, can be used.

The RO membrane water supply (water that is passed through the RO membrane device as treated water) has a suitable pH as follows. In order to adjust the pH of the RO membrane water supply, it is preferable to provide a pH adjusting means for adjusting the pH by adding an acid between the pretreatment membrane device and the RO membrane device. Examples of the pH adjusting means include means for adding an acid directly to the RO membrane water supply introduction line and the line mixer provided in the line or to a pH adjusting tank provided separately by a chemical injection pump or the like. The acid used here is not particularly limited, and inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid can be suitably used.

Normally, in the circulating cooling water system, the pH of the circulating cooling water has increased to about 8-9 due to the concentration circulation operation. Such a high pH is suitable for the permeation of the dispersant in the pretreatment membrane device. In the RO membrane device, since the cooling discharge water is further concentrated, there is a concern about generation of scale. In terms of scale suppression, it is preferable that the RO membrane device is operated at a reduced pH. The pH range of the RO membrane water supply is preferably 4.0 to 7.5. When the pH of the RO membrane water supply exceeds 7.5, scales such as calcium carbonate, calcium phosphate, calcium sulfate, and barium sulfate may be deposited depending on the water quality.

When the silica concentration in the cooling discharge water exceeds 30 mg / L, it is preferable to lower the pH of the RO membrane water supply to 4.0 to 5.5 in order to suppress the precipitation. The lower the pH of the RO membrane feed water, the better in terms of preventing scale precipitation. In order to lower the pH of the RO membrane water supply to less than 4.0, the amount of acid required becomes large, which is economically undesirable.

If the humic acid or fulvic acid is contained in the cooling discharge water, the RO membrane may be blocked. In that case, the pH of the cooling discharge water is preferably 5.5 to 7.0, particularly preferably 5.5 to 6.5. Within this pH range, humic acid and fulvic acid are dissociated and the RO membrane is blocked, and Ca in the cooling water is effectively dispersed by the dispersant to form a complex with fulvic acid. It becomes difficult.

In the present invention, the dispersant added to the circulating cooling water system is one that permeates the pretreatment membrane, so that the dispersant contained in the cooling discharge water and brought into the water recovery system is treated with the treated water ( The scale dispersion treatment in the RO membrane device is performed with the dispersant that has been permeated into the permeated water and permeated through the pretreatment membrane. Therefore, the RO membrane water supply needs to contain a dispersant at a concentration effective for the scale dispersion treatment.

The concentration of the dispersant in the RO membrane water supply required for the scale dispersion treatment of the RO membrane device differs depending on the quality of the cooling discharge water, the treatment conditions (water recovery rate) of the pretreatment membrane and the RO membrane, and cannot be generally specified. . In general, the dispersant concentration of the RO membrane water supply is preferably 3 mg / L or more, particularly about 5 to 30 mg / L.

When the concentration of the dispersant in the RO membrane water supply is insufficient to obtain a sufficient scale dispersion effect in the RO membrane device, the dispersant is added on the inlet side of the RO membrane device (between the pretreatment membrane device and the RO membrane device). Additional addition is preferred. As the dispersant added here, those suitable as the dispersant used in the circulating cooling water system described above can be used, but it is not necessarily the same as the dispersant added in the circulating cooling water system, and is different. A dispersant may be used.

The dispersant concentration of the RO membrane water supply may be measured, and the amount of dispersant added may be controlled so that the dispersant concentration becomes a predetermined concentration. As a method for measuring the dispersant concentration, a method using a turbidimetric method (for example, a method described in JP-A-2006-64498) can be employed. The dispersant can be additionally added to the RO membrane water supply by, for example, a dispersant addition unit that is linked to the dispersant concentration measurement unit of the RO membrane water supply.

According to the present invention, in order to use the dispersant added to the circulating cooling water system as the dispersing agent for the RO membrane device, the dispersant dispersed in the cooling discharge water after being added to the circulating cooling water system is used as the RO membrane device. When this is reached, it is necessary to remain active enough to function as a dispersant. Since the residence time of the cooling water in the cooling tower of the circulating cooling water system affects the activity of the dispersing agent, the residence time of the cooling tower of the circulating cooling water system so that the dispersant exhibits sufficient activity in the RO membrane device. It may be preferable to adjust the value.

The water recovery rate in the RO membrane device is preferably determined in consideration of the scale precipitation tendency in the RO membrane device. Since the conductivity of the cooling effluent treated in the present invention and the concentration of Ca, Mg, etc. in the cooling effluent as a scale factor may vary, the conductivity, Ca concentration, Mg concentration, etc. The RO membrane water recovery rate may be adjusted accordingly. The water recovery rate may be set by determining the presence or absence of scale from pH, dispersant concentration, water quality, and the like.

Specifically, a conductivity meter that measures the conductivity of one or more of the cooling discharge water, RO membrane water supply, and RO membrane concentrated water is provided, and the scale deposition tendency in the RO membrane device is evaluated based on the measured values. And controlling the water recovery rate of the RO membrane device. In this case, if the measured value of the conductivity meter is high, it is determined that the tendency of scale deposition is high, and the valve opening on the permeate water extraction side of the RO membrane is made small so that the water recovery rate becomes low. Conversely, when the measured value of the conductivity meter is low, it is determined that the tendency of scale deposition is low, and the opening degree of the valve on the permeate extraction side of the RO membrane device is increased so that the water recovery rate is high.

Alternatively, the dispersion concentration of the cooling discharge water and / or the RO membrane feed water is measured, and when the measured value of the dispersion concentration is high, it is judged that the tendency of scale precipitation is low, and the RO membrane device is set so that the water recovery rate becomes high. If the measured value of the dispersant concentration is low, it is judged that the tendency of scale precipitation is high, and the RO membrane device has a low water recovery rate. Reduce the valve opening on the permeate extraction side.

In the RO membrane device, particularly when there is a concern about the generation of silica scale, when stopping the RO membrane device, the cooling exhaust water that is not concentrated inside the device, RO membrane permeated water, pure water, or deionized Flushing with water is preferred. This is because when the RO membrane device is stopped while the concentrated water remains in the RO membrane device, silica scale and other scales may be generated depending on the stop time, and the RO membrane device cannot be stably operated when the operation is resumed. Because there is. In this case, for example, when the operation of the RO membrane device is stopped, the RO membrane permeate is circulated to the inlet side of the RO membrane device, the RO membrane concentrated water is discharged out of the system, and the inside of the RO membrane device is moved to the primary side of the RO membrane ( For example, the water supply side) and the secondary side (concentrated water side) may be replaced with RO membrane permeate.

<Other processing>
In the circulating cooling water system according to the present invention, as a slime control agent, hypochlorites such as sodium hypochlorite (NaClO), chlorine agents such as chlorine gas, chloramine, chlorinated isocyanurate, monochlorosulfamic acid, etc. Chlorinated with amide sulfuric acid, compound with amide sulfate group reacted with chlorine, hypobromite such as sodium hypobromite, bromine such as dibromohydantoin, bromine with amine, ammonia, amide sulfate group A bound bromine agent reacted with the compound, an organic agent such as DBNPA (dibromonitrilopropion acid), MIT (methylisothiazolone), hydrazine, hydantoin (5,5-dimethylhydantoin) and the like may be added. These may be added alone or in combination of two or more.

In the RO membrane apparatus, the slime control treatment may be performed using these slime control agents added in the circulating cooling water system. A slime control treatment may be performed by adding an additional slime control agent before the RO membrane device. When the oxidation deterioration of the RO membrane due to a chlorine agent or the like becomes a problem, a slime control agent may be added separately after reducing and removing the chlorine agent in the cooling discharge water.

One type of these slime control agents may be added, or two or more types may be added simultaneously or alternately. Further, it may be added continuously or intermittently.

When cooling discharge water contains heavy metal ions such as copper and iron derived from heat exchangers, the RO membrane is promoted in the presence of redox agents such as thorium hypochlorite and hydrazine and heavy metal ions. May be deteriorated. In that case, by adding a substance having a chelating action of heavy metal (for example, EDTA), contact between the membrane and heavy metal can be prevented, and accelerated deterioration can be prevented.

Polyamide-based RO membranes deteriorate with contact with hypochlorite regardless of the presence or absence of heavy metals. Hypochlorite has a high possibility of causing membrane deterioration. Therefore, it is preferable to avoid application as much as possible, and to apply it, after removing residual chlorine, it is preferable to pass water through the RO membrane device. *

In order to stabilize the pretreatment membrane device and the RO membrane device, a polymer compound having a phenolic hydroxyl group (hereinafter referred to as “phenolic polymer”) as a coagulation aid in the cooling discharge water that is the treated water. ) May be added.

Examples of phenolic polymers include vinylphenol homopolymers, modified vinylphenol homopolymers, copolymers of vinylphenol and modified vinylphenol, vinylphenol and / or copolymers of modified vinylphenol and hydrophobic vinyl monomers. And polyvinylphenol polymers such as polymers; phenol resins such as polycondensates of phenol and formaldehyde, polycondensates of cresol and formaldehyde, and polycondensates of xylenol and formaldehyde. As the phenolic polymer, a resol type secondary reaction is performed on a novolac type phenol resin described in JP2010-131469A, JP2013-255922A, JP2013-255923A, and the like. It is preferable to use the obtained reaction product.

The melting point of the phenolic polymer obtained by subjecting the novolac type phenol resin to the resol type secondary reaction is preferably 130 to 220 ° C., particularly 150 to 200 ° C. The phenolic polymer has a weight average molecular weight of preferably 5,000 to 50,000, and more preferably 10,000 to 30,000.

The amount of the phenolic polymer added varies depending on the quality of the cooling effluent, and is not particularly limited, but is preferably about 0.01 to 10 mg / L as the active ingredient concentration.

When pretreatment membrane devices such as MF membrane devices and RO membrane devices are blocked by the treatment of cooling and draining water for a long time, the amount of treated water (permeated water) obtained decreases (that is, the water recovery rate decreases) In such a case, these membrane devices are washed to remove clogs and recover the amount of treated water. The chemicals used for the cleaning treatment can be appropriately selected according to the occluding substance and membrane material. For example, hydrochloric acid, sulfuric acid, nitric acid, sodium hypochlorite, sodium hydroxide, citric acid, oxalic acid, etc. are selected. be able to.

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.

[Dispersant]
The specifications of the dispersant used in the following Examples and Reference Examples are as follows.
AA / AMPS: copolymer of acrylic acid and AMPM, acrylic acid: AMPM (molar ratio) = 70: 30, weight average molecular weight 10,000
AA / HAPS: copolymer of acrylic acid and HAPS, acrylic acid: HAPS (molar ratio) = 70: 30, weight average molecular weight 8,000
AA / AMPS / N-tBAA: terpolymer of acrylic acid, AMPS, and N-tert-butylacrylamide, acrylic acid: AMPM: N-tBAA (molar ratio) = 70: 20: 10, weight average molecular weight 12, 000
AA / MA: copolymer of acrylic acid and maleic acid, acrylic acid: maleic acid (molar ratio) = 70: 30, weight average molecular weight 25,000

[Cooling discharge water]
The cooling discharge water used for water recovery treatment in the following examples and reference examples is a cooling tower blow water (hereinafter, simply referred to as a circulating cooling water system) operating at a concentration factor of 3.5 times using Chiba industrial water as raw water. "Blow water").
In this circulating cooling water system, the dispersants described in the respective examples and comparative examples are added so that the dispersant concentration in the system becomes a predetermined retention concentration, and sodium hypochlorite (NaClO) is added in the system. The slime control treatment is performed by adding the residual chlorine concentration of 0.5 mg / L.
The pH of the blow water is 8.5 to 8.9 (about 8.8).

[Example 1]
MF membrane was used as a pretreatment membrane, and water was collected by treating blow water in the order of strainer, MF membrane device, and RO membrane device.
The mesh pore diameter of the strainer is 400 μm. As the MF membrane, “Pureia GS (hydrophilic PVDF, pore size 0.02 μm, external pressure type)” manufactured by Kuraray Co., Ltd. was used. As the RO membrane, “KROA-2032-SN (polyamide ultra-low pressure RO membrane)” manufactured by Kurita Kogyo Co., Ltd. was used. The cleaning frequency of the MF membrane device was 1 time / 30 minutes.

The blow water was sequentially passed through the strainer and the MF membrane device without adjusting the pH, and then sulfuric acid was added at the inlet side of the RO membrane device to adjust to pH 5.0. Similarly, sodium bisulfite is added at the inlet side of the RO membrane device to reduce the residual chlorine concentration to 0.05 mg / L or less, and “Kuriverter (registered trademark) IK-110” (bonded chlorine) manufactured by Kurita Kogyo Co., Ltd. The system slime control agent) was added at 10 mg / L, and the slime control treatment of the RO membrane device was performed.

The water recovery rates of the MF membrane device and RO membrane device started from 90% and 80%, respectively, and the total water recovery rate was 72%. Since the blow water has a high organic substance concentration, the water recovery rate of the MF membrane device and the RO membrane device gradually decreases with time. When the water recovery rate of the MF membrane device or the RO membrane device fell below 50%, the device was once stopped and washed, and water flow was resumed under the condition that the total water recovery rate was 72%. Under this condition, the water flow and recovery process were continued for one month.

In the above water recovery process, the dispersant concentration of the pretreatment membrane (MF membrane) feed water is 10.5 mg / L, and the dispersant concentration of the RO membrane feed water is 10.3 mg / L. The recovery rate was 70%.

[Example 2]
Blow water was collected in the same manner as in Example 1 except that AA / HAPS was used instead of AA / AMPS as the dispersant. Table 1 shows the dispersant concentration of the pretreatment membrane and RO membrane and the average water recovery rate.

[Example 3]
Blow water was recovered in the same manner as in Example 1 except that AA / AMPS / N-tBAA was used in place of AA / AMPS as the dispersant. Table 1 shows the dispersant concentration of the pretreatment membrane and RO membrane and the average water recovery rate.

[Example 4]
Blow water was collected in the same manner as in Example 1 except that the pH of the MF membrane feed water was adjusted to 5.5. Table 1 shows the dispersant concentration of the pretreatment membrane and RO membrane and the average water recovery rate.

[Example 5]
Blow water was collected in the same manner as in Example 1 except that the retention concentration of the dispersant in the circulating cooling water system was 3 mg / L and that 7 mg / L of dispersant was added to the RO membrane water supply. Table 1 shows the dispersant concentration of the pretreatment membrane and RO membrane and the average water recovery rate.

[Example 6]
An alkaline solution of a phenolic polymer (active ingredient concentration 16% by weight, pH 12) having a weight average molecular weight of 12000 and a melting point of 170 ° C. produced according to the method of Example I-1 of JP2013-255923A is used as blow water. The blow water was recovered in the same manner as in Example 1 except that 1 mg / L was added as the active ingredient concentration. Table 1 shows the dispersant concentration of the pretreatment membrane and RO membrane and the average water recovery rate.

[Reference Example 1]
Blow water was collected in the same manner as in Example 1 except that the pH of the MF membrane feed water was adjusted to 4.5. Table 1 shows the dispersant concentration of the pretreatment membrane and RO membrane and the average water recovery rate.

[Reference Example 2]
Blow water was collected in the same manner as in Example 1 except that a UF membrane (“PW2540C30” manufactured by GE) having a molecular weight cut-off of 10,000 was used as the pretreatment membrane. Table 1 shows the dispersant concentration of the pretreatment membrane and RO membrane and the average water recovery rate.

[Reference Example 3]
Blow water was collected in the same manner as in Example 1 except that the pH of the RO membrane feed water was 7.0. Table 1 shows the dispersant concentration of the pretreatment membrane and RO membrane and the average water recovery rate.

[Reference Example 4]
Blow water was recovered in the same manner as in Example 1 except that AA / MA was used in place of AA / AMPS as the dispersant. Table 1 shows the dispersant concentration of the pretreatment membrane and RO membrane and the average water recovery rate.

[Reference Example 5]
Blow water was collected in the same manner as in Example 1 except that the concentration of the dispersant retained in the circulating cooling water system was 1 mg / L. Table 1 shows the dispersant concentration of the pretreatment membrane and RO membrane and the average water recovery rate.

Table 1 shows the following.
According to the present invention, by performing the treatment so that an effective amount of the dispersant remains in the RO membrane water supply, a stable treatment can be continued with a high water recovery rate.

In Reference Example 1, since the membrane feed water pH was lowered, the dispersant permeability of the pretreatment membrane was low, and the dispersant concentration of the RO membrane feed water was low, so the average water recovery rate was lowered.
In Reference Example 2, since a UF membrane having a small fractional molecular weight was used as the pretreatment membrane, the dispersant permeability of the pretreatment membrane was low, and the dispersant concentration of the RO membrane water supply was low, so the average water recovery rate was reduced. ing.
In Reference Example 3, since the pH of the RO membrane water supply is high and there are problems of calcium scale precipitation and membrane blockage in the RO membrane, the average water recovery rate is lowered.
In Reference Example 4, since a polymer containing only carboxyl groups and no sulfonic acid groups was used as the dispersant, it became insoluble when the pH of the RO membrane water supply was lowered, and it did not function as a dispersant, so the RO membrane treatment was stable. The average water recovery rate has declined.
In Reference Example 5, since the dispersant retention concentration in the circulating cooling water system is low and the dispersant concentration in the RO membrane water supply is low even if it passes through the pretreatment membrane, the RO membrane treatment is not stable and the average water recovery rate is reduced. is doing.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2014-052048 filed on March 14, 2014, which is incorporated by reference in its entirety.

Claims

Cooled discharged water which treats the discharged water from the circulating cooling water system to which the dispersant for dispersing the scale component is added with a water recovery system including a pretreatment membrane and a reverse osmosis membrane and returns the treated water to the circulating cooling water system. In the circulating cooling water system, wherein the dispersing agent permeates the pretreatment membrane.
The method of claim 1, wherein the pretreatment membrane has a permeability of the dispersant calculated by the following formula of 80% or more.
Permeability = (dispersant concentration of pretreated membrane permeated water / dispersant concentration of pretreated membrane feed water) × 100
3. The cooling drainage recovery method according to claim 1 or 2, wherein the pretreatment membrane is a microfiltration membrane or an ultrafiltration membrane.
4. The method for recovering cooling discharge water according to any one of claims 1 to 3, wherein the pH of the water supplied to the pretreatment film is 5 or more.
5. The method for recovering cooling effluent according to any one of claims 1 to 4, wherein a fractional molecular weight of the pretreatment film is 30,000 or more.
6. The method for recovering cooling discharged water according to any one of claims 1 to 5, wherein the dispersant is a polymer having a sulfonic acid group and a carboxyl group.
7. The dispersant according to claim 6, wherein the dispersant is a copolymer of methacrylic acid and / or acrylic acid and 3-allyloxy-2-hydroxy-1-propanesulfonic acid and / or 2-acrylamido-2-methylpropanesulfonic acid. A method for recovering cooling effluent, wherein the cooling effluent is a copolymer.
8. The method for recovering cooling effluent according to any one of claims 1 to 7, wherein the pH of the reverse osmosis membrane feed water is adjusted to 4.0 to 7.5.
9. The dispersant of any one of claims 1 to 8, wherein the dispersant concentration of the reverse osmosis membrane feed water is measured, and the dispersant is added to the reverse osmosis membrane feed water so that the dispersant concentration becomes a predetermined concentration. A method for recovering cooling effluent.
In any one of Claims 1 thru | or 9, the electrical conductivity of one or more of the said discharged water, reverse osmosis membrane water supply, and reverse osmosis membrane concentrated water is measured, According to the measured value of this conductivity, A method for recovering cooling discharged water, comprising adjusting a water recovery rate of the reverse osmosis membrane.
In any 1 item | term of the Claims 1 thru | or 10, the said dispersing agent density | concentration of the said discharged water and / or reverse osmosis membrane water supply is measured, The water recovery rate of this reverse osmosis membrane is set according to the measured value of this dispersing agent density | concentration. A method of recovering cooling effluent characterized by adjusting.
12. The method for recovering cooling drainage water according to any one of claims 1 to 11, wherein a polymer compound having a phenolic hydroxyl group is added to the drainage water.
13. The reverse osmosis membrane concentrated water according to any one of claims 1 to 12, wherein the reverse osmosis membrane permeated water is circulated or pure water or deionized water is passed when the water recovery system is stopped. A cooling drainage recovery method characterized by stopping the water recovery system after performing an operation of discharging to the outside of the system.
A pretreatment membrane device through which discharged water from the circulating cooling water system is passed, a reverse osmosis membrane device through which the permeated water of the pretreatment membrane device is passed, and a circulating cooling water system that passes the permeated water of the reverse osmosis membrane device The circulating cooling water system has a dispersant addition means for adding a dispersant for dispersing the scale component to the aqueous system, and the dispersant is the pretreatment film. A cooling drainage recovery device characterized by being permeated through water.
The cooling wastewater recovery device according to claim 14, wherein the pretreatment membrane has a permeability of the dispersant calculated by the following formula of 80% or more.
Permeability = (dispersant concentration of pretreated membrane permeated water / dispersant concentration of pretreated membrane feed water) × 100
16. The cooling drainage recovery apparatus according to claim 14 or 15, wherein the pretreatment membrane is a microfiltration membrane or an ultrafiltration membrane.
17. The apparatus for recovering cooling drainage according to any one of claims 14 to 16, wherein the pH of the feed water of the pretreatment film is 5 or more.
18. The apparatus for recovering cooling effluent according to any one of claims 14 to 17, wherein a fractional molecular weight of the pretreatment film is 30,000 or more.
The apparatus for recovering cooling drainage according to any one of claims 14 to 18, wherein the dispersant is a polymer having a sulfonic acid group and a carboxyl group.
20. The dispersant according to claim 19, wherein the dispersant is a copolymer of methacrylic acid and / or acrylic acid and 3-allyloxy-2-hydroxy-1-propanesulfonic acid and / or 2-acrylamido-2-methylpropanesulfonic acid. An apparatus for recovering cooling effluent, characterized by being a copolymer.
21. The cooling and draining water recovery apparatus according to claim 14, further comprising pH adjusting means for adjusting the pH of the reverse osmosis membrane feed water to 4.0 to 7.5.
22. The dispersant concentration measuring means for measuring the dispersant concentration of the reverse osmosis membrane feed water, and the dispersant concentration measured by the dispersant concentration measuring means is a predetermined value according to any one of claims 14 to 21. Dispersing agent adjusting means for adding the dispersing agent to the reverse osmosis membrane feed water so as to have a concentration.
The conductivity measuring means according to any one of claims 14 to 22, wherein the conductivity measuring means measures the conductivity of one or more of the discharged water, reverse osmosis membrane water supply and reverse osmosis membrane concentrated water, and the conductivity measuring means. And a water recovery rate adjusting means for adjusting the water recovery rate of the reverse osmosis membrane according to the measured value.
24. The dispersant concentration measuring means for measuring the dispersant concentration of the discharged water and / or the reverse osmosis membrane water supply according to any one of claims 14 to 23, and the measured value of the dispersant concentration measuring means according to the measured value of the dispersant concentration measuring means. A cooling drainage recovery apparatus comprising water recovery rate adjusting means for adjusting the water recovery rate of the reverse osmosis membrane.
25. The cooling / draining water recovery apparatus according to any one of claims 14 to 24, further comprising a coagulation assistant adding means for adding a phenolic hydroxyl group to the draining water.
26. The reverse osmosis membrane device according to any one of claims 14 to 25, wherein the reverse osmosis membrane device circulates the reverse osmosis membrane permeated water to the front stage of the reverse osmosis membrane device, or pure water or deionized water. Means for passing water through the osmosis membrane device and concentrated water discharge means for draining the reverse osmosis membrane concentrated water out of the system, and when the cooling drainage recovery device is stopped, And a control means for stopping the cooling drainage recovery device after performing an operation of circulating pure water or deionized water and discharging the reverse osmosis membrane concentrated water out of the system. A cooling drainage recovery device characterized by that.