JP2017100081A - Desalination processor of water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means for performing rapidly phase separation between a temperature sensitive medicine rich phase and a salt rich phase in a desalination processor of water for separating to obtain plain water from sea water.SOLUTION: A desalination processor of water includes a mixing means 9 of mixing water to be treated 101 containing salts and a solution in which a temperature sensitive agent having a lower limit critical solution temperature is dissolved in water, a first phase separation tank 3, a heating step 4, a second phase separation tank 5, a cooling means 8, a first circulation means, a membrane separator 7 for membrane separating a temperature sensitive agent dilution solution 104 separated by a second phase separation tank to obtain plain water 106 and the temperature sensitive agent recovery solution 107, a second circulation means, and a phase separation acceleration agent addition means 10 for adding a phase separation acceleration agent to a mixed solution and/or temperature sensitive agent rich solution 102.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method and an apparatus for producing fresh water from, for example, seawater using a temperature-sensitive drug and a semipermeable membrane.

  Various methods for desalinating seawater using a semipermeable membrane are known, but a reverse osmosis method for forcibly permeating water by applying a pressure higher than the osmotic pressure to seawater has been mainly developed. Since this method requires pressurization to a high pressure, there is a problem that the equipment cost and operation cost are high. On the other hand, if a salt solution having a higher concentration than seawater is present through the semipermeable membrane, water can be transferred to the salt solution by osmotic pressure without applying pressure. If a solution in which a volatile gas is dissolved is used as the salt solution (attraction solution), the salt solution can be distilled to evaporate and separate the volatile gas to obtain fresh water. As this forward osmosis method, a method using a combination of ammonia and carbon dioxide as a volatile gas has already been developed.

  On the other hand, what used the solute which has a cloud point for this attraction solution is also known (patent document 1).

  In the method of Patent Document 1, seawater is sent to a forward osmosis system, where it is brought into contact with an attracting solution through a semipermeable membrane, and water in the seawater is transferred to the attracting solution through the semipermeable membrane by osmotic pressure. Concentrated seawater left after the water has moved into the attraction solution flows out of the forward osmosis system. On the other hand, the diluted attraction solution diluted with water in seawater is sent to a precipitation system equipped with a heater, where the diluted attraction solution that causes phase separation or precipitation is pressurized by a pump and sent to a filtration system. At that time, a liquid having a temperature lower than the cloud point of the solute can be added. The filtered membrane filtrate is further purified in the post-processing section to become drinking water. Various surfactants, dispersants, foaming agents, emulsifiers such as polyethylene glycol and polypropylene glycol are used for the solute having a cloud point, and nanofiltration membranes and reverse osmosis membranes are used for the filter media of the filtration system. ing.

  Further, when salt is added to the temperature-responsive polymer (thermosensitive agent), the lower critical solution temperature (referred to as LCST or cloud point) is lowered, and aggregation may occur at a temperature that does not aggregate with the thermosensitive agent alone. Are known. Therefore, there is a process that proposes to extract drinking water and concentrated salt water by mixing the temperature sensitive agent with seawater using this principle, taking out the temperature sensitive agent rich phase and salt rich phase, and separating them from each other by membrane separation. (Patent Document 2). Poly-N-vinylcaprolactam (PVCL) is used as a temperature sensitive agent.

  An overview of this process is shown in FIG. First, seawater containing 3.4% NaCl is mixed with 5% PVCL aqueous solution in a mixer and stirred well, and then the mixture is placed in a stationary tank and phase separated. The phase-separated extraction phase E1 with NaCl of less than 3,400 ppm and PVCL of about 6,000 ppm and the extracted residual phase R1 with NaCl of 50,000 ppm and PVCL of less than 600 ppm are taken out separately and phase-separated. The extraction phase E1 is separated by membrane separation into an aqueous phase PEM1 containing a low concentration of NaCl and about 10,000 ppm of PVCL and an aqueous phase EM1 of less than 3,400 ppm of NaCl and about 0.0 ppm of PVCL. The aqueous phase PEM1 is returned to the mixer, and the aqueous phase EM1 separates NaCl with a reverse osmosis membrane as necessary to make drinking water. The extracted residual phase R1 is separated into an aqueous phase PRM1 having a low NaCl concentration and a high PVCL concentration and an aqueous phase RM1 having a high NaCl concentration and a PVCL of approximately 0.0 ppm by membrane separation. The aqueous phase PRM1 is returned to the mixer and the aqueous phase RM1 is discarded.

US 2010/0155329 A1 JP 2010-274252 A

  In principle, the method of Patent Document 2 in which phase separation is first performed is superior in cost to the method of Patent Document 1 in which seawater is separated by a semipermeable membrane. Since the mixed solution of salt water and salt water is not promptly separated into layers, a large sedimentation tank or a centrifugal separator having a long residence time is required, resulting in an increase in apparatus cost. In addition, a temperature sensitive agent such as PVCL is expensive, and there is a problem that a chemical cost per unit production water increases.

  The object of the present invention is to mix an aqueous solution of a temperature-sensitive drug (temperature-sensitive agent) having a lower critical solution temperature with water to be treated containing salts such as seawater to obtain a temperature-sensitive drug concentrated phase and a salt-rich phase. An object of the present invention is to provide means for rapidly separating a temperature-sensitive drug-rich phase and a salt-rich phase in a water desalting apparatus that separates and acquires fresh water from a temperature-sensitive drug-rich phase.

  Another object of the present invention is to reduce the drug cost by using an inexpensive drug as the temperature-sensitive drug having such an action.

  The present invention provides means for solving the above problems, and by adding a phase separation accelerator in advance to a liquid mixture to be phase-separated, a temperature-sensitive drug-rich phase in a phase separation tank and It has been made by finding that the separation into a salt-rich phase is facilitated and the gravity separation is facilitated, and that the separation is further facilitated by heating the above mixed liquid.

  That is, the present invention provides a mixing means for mixing the water to be treated containing salts and a solution in which a temperature sensitive drug having a lower critical solution temperature is dissolved in water, and the temperature sensitivity of the mixed solution flowing out from the mixing means. A first phase separation tank that separates a drug-rich phase and a salt-rich phase, and a temperature-sensitive drug-rich phase liquid that flows out of the first phase separation tank is heated to a temperature equal to or higher than the lower critical solution temperature. Means, a temperature-sensitive drug concentrated phase liquid heated by the heating means, a temperature-sensitive drug concentrated solution mainly composed of a temperature-sensitive drug, and a fresh water mainly containing a small amount of the temperature-sensitive drug. A second phase separation tank that phase-separates into a temperature-sensitive drug dilute solution; and a cooling means that cools the temperature-sensitive drug concentrated solution separated in the second phase separation tank to a temperature equal to or lower than the lower critical solution temperature. The temperature sensitive drug cooled by the cooling means A membrane separation apparatus for separating fresh water and a temperature-sensitive drug recovery liquid by membrane-separating the temperature-sensitive drug dilute solution separated in the second phase separation tank with a first circulation means for circulating a concentrated solution to the mixing means A second circulation means for circulating the temperature-sensitive drug recovery liquid to the temperature-sensitive drug concentrated phase liquid, and a phase separation in which a phase separation accelerator is added to the liquid mixture and / or the temperature-sensitive drug concentrated solution. The present invention provides a water desalting apparatus characterized by having an accelerator addition means.

  In addition, instead of poly-N-vinylcaprolactam (PVCL) used in Patent Document 2, an inexpensive polyoxyethylene / polyoxypropylene glycol-based copolymer is used as a temperature sensitive drug, and a good phase is obtained. It was also found that separation was obtained.

  Accordingly, the present invention also provides the water desalting apparatus as described above, wherein the temperature-sensitive drug having the lower critical solution temperature is a polyoxyethylene / polyoxypropylene glycol copolymer. Is.

  As a phase separation accelerator, for example, a cationic surfactant is used, and by adding this, it becomes easy to separate into a temperature-sensitive drug-rich phase and a salt-rich phase in the first phase separation tank, and gravity separation is easy. Become. Although the mechanism of the separation promotion phenomenon by the phase separation accelerator has not been completely elucidated, it is considered that the interfacial tension between the temperature sensitive drug concentrated phase and the salt concentrated phase is related.

  According to the present invention, phase separation is promoted when an aqueous solution of a temperature-sensitive drug having a lower critical solution temperature is mixed with water to be treated containing salts such as seawater to cause phase separation into a temperature-sensitive drug concentrated phase and a salt-rich phase. By adding an agent, this phase separation can be performed quickly, the phase separation tank can be made compact, and fresh water can be efficiently obtained from the temperature-sensitive drug-rich phase. If a polyoxyethylene / polyoxypropylene glycol-based copolymer is used for the active drug, the drug cost can be reduced.

It is a block diagram which shows an example of a structure of the apparatus of this invention. It is a block diagram which shows an example of a structure of the conventional apparatus.

  The water desalination apparatus of the present invention comprises a mixing means, a first phase separation tank, a heating means, a second phase separation tank, a cooling means, a circulation means, a membrane separation apparatus, a second circulation means, and a phase separation accelerator. It consists of means.

Mixing means The mixing means is means for mixing the water to be treated containing salts with a solution obtained by dissolving a temperature-sensitive drug having a lower critical solution temperature in water.

  The water to be treated may be water containing salts, but for example, seawater, lake water, river water, factory wastewater, and the like.

  Temperature-sensitive drugs are substances that are hydrophilic and well soluble in water at low temperatures, but become hydrophobic and their solubility decreases at a certain temperature or higher.The temperature at which they change from hydrophilic to hydrophobic is the lower critical temperature or cloud point. be called. When this temperature is reached, a hydrophobized temperature-sensitive drug is precipitated, resulting in white turbidity or phase separation. When gradually warming, there are those that become cloudy by the drug but do not phase-separate quickly, those that become cloudy and then further heated, phase-separate quickly, and those that phase-separate without going cloudy. The chemical used in the above is one that undergoes phase separation immediately after warming, and the lower critical temperature herein means the temperature at which phase separation occurs.

  This temperature-sensitive agent is used as various surfactants, dispersants, emulsifiers, and the like. For example, alcohols, alkyl groups, glycols, or fatty acid and ethylene glycol compounds (water-soluble polyalkylene glycol derivatives, Polyoxyethylene polyoxypropylene alkyl ether, polyoxytetramethylene polyoxyethylene glycol, polyoxyethylene polyoxypropylene trimethylolpropane, polyoxyethylene polyoxypropylene glyceryl ether, polyoxyethylene polyoxypropylene pentaerythritol ether, etc.) alkyl group Or fatty acid and propylene oxide compound, acrylamide and alkyl group compound, ethylene glycol fatty acid ester, glycerin fatty acid ester, sorbi Fatty acid ester ethylene oxide adduct, amino acids and derivatives thereof, glycols such as butyl glycol and hexyl glycol, preferably a block or random copolymer of polyethylene glycol and polypropylene / polybutylene glycol, glycerol ethoxylate butoxylate, And trimethylolpropane ethoxybutoxylate. Among these, a polyoxyethylene / polyoxypropylene glycol copolymer is preferable.

  As the temperature-sensitive drug used in the present invention, those having a lower critical solution temperature in the range of 30 ° C to 80 ° C, particularly in the range of 40 ° C to 70 ° C are preferable. Since the lower critical solution temperature decreases when salt is added, the lower critical solution temperature when seawater is added is preferably 20 to 50 ° C.

  The concentration of the temperature-sensitive drug in the temperature-sensitive drug aqueous solution suffices as long as it can be separated into a temperature-sensitive drug-rich phase and a salt-rich phase when mixed with the water to be treated. Specifically, 40 to 80% is preferable.

  The mixing means of the water to be treated and the temperature-sensitive chemical aqueous solution may be a known means for mixing the two liquids. In addition to using a stirrer equipped with a stirrer, mixing in a pipe using an inline mixer or the like. Alternatively, a stirrer or the like may be attached to the phase separation tank to also serve as a mixing means.

First Phase Separation Tank The first phase separation tank separates the mixed solution flowing out from the mixing means into a temperature sensitive drug concentrated phase and a salt concentrated phase. Usually, this may be a tank that receives the liquid mixture and is allowed to stand, but it may be one that forcibly phase-separates using a centrifuge or the like.

Heating means The heating means is means for heating the temperature-sensitive drug concentrated phase liquid flowing out from the first phase separation tank to a temperature equal to or higher than the lower critical solution temperature. In this heating means, in order to promote phase separation, it is desirable to heat the lower critical solution temperature to 5 ° C. or higher, preferably 10 ° C. or higher. The upper limit of the temperature is preferably about 90 ° C. or less in consideration of using a cheaper low-temperature heat source. Although this heating means is not ask | required, it is preferable to utilize a factory waste heat using a heat exchanger.

Second phase separation tank Concentrated solution of temperature-sensitive drug heated by heating means, concentrated solution of temperature-sensitive drug mainly composed of temperature-sensitive drug, and a small amount of temperature-sensitive drug mainly composed of fresh water This is a tank that phase separates into a dilute solution of temperature-sensitive drug, and usually a tank that accepts the temperature-sensitive drug concentrated phase liquid and is allowed to stand still, but forcibly phase-separates using a centrifuge or the like. It may be a thing.

Cooling means / first circulation means The cooling means is means for cooling the temperature-sensitive drug concentrated solution separated in the second phase separation tank to a temperature below the lower critical solution temperature, and a heat exchanger or the like can be used. it can. The circulation means is a means for circulating the cooled temperature-sensitive drug concentrated solution to the mixing means, and usually comprises a pump and piping. By these means, the temperature-sensitive drug concentrated solution is made into a phase-separable state and mixed with the water to be treated containing salts.

Membrane separator In the membrane separator, the temperature-sensitive drug dilute solution separated in the second phase separation tank is subjected to membrane separation to obtain fresh water and a temperature-sensitive drug recovery solution. As the membrane, a membrane that does not allow a temperature sensitive drug to pass through may be used, and a nanofiltration membrane, a reverse osmosis membrane, or the like can be used. Commercially available membrane separation apparatuses using these membranes may be used.

Second circulation means The second circulation means is means for circulating the temperature-sensitive drug recovery liquid separated by the membrane separator to the temperature-sensitive drug concentrated phase. This is for recovering the temperature-sensitive drug from the temperature-sensitive drug dilute solution. This second circulation means is also usually composed of a pump and piping.

Phase separation accelerator addition means A means for adding a phase separation accelerator to the mixed liquid phase-separated in the first phase separation tank.

  The phase separation accelerator promotes phase separation into a temperature-sensitive drug-rich phase and a salt-rich phase in the first phase separation tank. As the phase separation accelerator, a cationic surfactant or a nonionic surfactant can be used. Examples of the cationic surfactant include quaternary ammonium salts such as dodecyltrimethylammonium chloride. Examples of nonionic surfactants include acetylene glycol and its derivatives. The addition amount is suitably about 1 to 10%. The addition position of the phase separation accelerator may be present in the mixed liquid in the first phase separation tank. For example, it is added to the temperature-sensitive drug concentrated solution separated in the second phase separation tank. can do. In addition, for example, it may be added to a temperature sensitive chemical aqueous solution mixed with water to be treated. This adding means usually comprises a tank containing a phase separation accelerator, a metering pump or valve, a flow rate measuring device, or the like.

  The structure of an example of the desalinization apparatus of the water of this invention is shown in FIG.

  This apparatus includes a pretreatment device 1 such as sand filtration, a heater 2, a mixing tank 9 as a mixing means, a first phase separation tank 3, a heat exchanger 4 as a heating means, a second phase separation tank 5, It comprises a cooler 6, a membrane separator 7, a heat exchanger 8 as a cooling means, and a phase separation accelerator adding means 10.

  The seawater 101 that is the water to be treated is first pretreated by the pretreatment device 1, heated by the heater 2, and put into the mixing tank 9. In the mixing tank 9, it is mixed with the temperature sensitive drug concentrated solution 105 separated and sent in the second phase separation tank, and the mixed liquid is put into the first phase separation tank 3. Therefore, the temperature-sensitive drug concentrated phase liquid 102 phase-separated into the upper layer is heated to the lower critical solution temperature or higher by the heat exchanger 4 and put into the second phase separation tank 5. On the other hand, the salt-rich phase liquid 103 phase-separated in the lower layer in the first phase separation tank 3 becomes waste seawater. The temperature-sensitive drug diluted solution 104 phase-separated into the upper layer in the second phase separation tank 5 is cooled by the cooler 6 and sent to the membrane separation device 7. On the other hand, the temperature-sensitive drug concentrated solution 105 which is the lower layer in the second phase separation tank 5 is cooled by the heat exchanger 8, and the phase separation accelerator is added by the phase separation accelerator addition means 10. Will be returned. In the membrane separation device 7, the temperature sensitive drug contained in the temperature sensitive drug dilute solution 104 is separated and recovered and taken out as fresh water 106. The separated temperature-sensitive drug recovery liquid 107 is returned to and merged with the temperature-sensitive drug concentrated phase liquid 102 separated in the first phase separation tank 3.

  According to the present invention, the salt can be efficiently removed from the treated water by promoting phase separation between the treated water containing salts such as seawater and the aqueous solution of the temperature sensitive drug having the lower critical solution temperature. It can be widely used in apparatuses for producing fresh water using a temperature sensitive drug.

DESCRIPTION OF SYMBOLS 1 Pretreatment apparatus 2 Heater 3 First phase separation tank 4 Heat exchanger (heating means)
5 Second phase separation tank 6 Cooler 7 Membrane separator 8 Heat exchanger (cooling means)
9 Mixing tank (mixing means)
10 Phase separation accelerator addition means 101 Seawater (treated water)
102 Temperature Sensitive Agent Concentrated Solution 103 Salt Concentrated Phase Solution 104 Temperature Sensitive Agent Dilute Solution 105 Temperature Sensitive Agent Concentrated Solution 106 Fresh Water 107 Temperature Sensitive Agent Recovery Solution

Claims (2)

  Mixing means for mixing the water to be treated containing salts and a solution in which a temperature-sensitive drug having a lower critical solution temperature is dissolved in water, and the mixture flowing out from the mixing means is mixed with a temperature-sensitive drug-rich phase and a salt-rich liquid. A first phase separation tank for phase separation into phases, a heating means for heating a temperature-sensitive drug concentrated phase liquid flowing out of the first phase separation tank to a temperature equal to or higher than the lower critical solution temperature, and the heating The temperature-sensitive drug concentrated phase liquid heated by means of the temperature-sensitive drug concentrated solution mainly composed of temperature-sensitive drug and the temperature-sensitive drug dilute solution mainly composed of fresh water and containing a small amount of temperature-sensitive drug. A second phase separation tank that phase-separates into two, a cooling means that cools the temperature-sensitive drug concentrated solution separated in the second phase separation tank to a temperature that is equal to or lower than the lower critical solution temperature, and is cooled by the cooling means The prepared temperature-sensitive drug concentrated solution A first circulation means that circulates in stages, a membrane separator that separates the temperature-sensitive drug dilute solution separated in the second phase separation tank to obtain fresh water and a temperature-sensitive drug recovery liquid, and the temperature-sensitive A second circulation means for circulating the chemical recovery liquid to the temperature sensitive drug concentrated phase liquid, and a phase separation accelerator addition means for adding a phase separation accelerator to the mixed liquid and / or the temperature sensitive drug concentrated solution. An apparatus for desalinating water, comprising:   The water desalting apparatus according to claim 1, wherein the temperature-sensitive drug having the lower critical solution temperature is a polyoxyethylene / polyoxypropylene glycol copolymer.

Images