JP6053631B2 - Desalination apparatus and desalination method, and method of co-production of fresh water, salt and valuables - Google Patents

Description

  The present invention relates to a desalination apparatus and a desalination method for producing fresh water and salt in one facility using an electrodialysis section, and a method for co-production of fresh water, salt and valuables.

  Conventionally, a drinking water and salt production apparatus including a reverse osmosis membrane device and an electrodialysis unit has been proposed (see, for example, Patent Document 1). In such a production apparatus, raw water containing salt such as seawater is supplied to the reverse osmosis membrane device to produce desalted water by desalting, while the concentrated salt water concentrated by the reverse osmosis membrane device is supplied to the electrodialysis unit. Then, further concentrate to make concentrated brine. And the salt is manufactured by carrying out the evaporative crystallization of the obtained concentrated brine with an evaporator.

Japanese Patent No. 2887105

  By the way, in the proposal of a device for producing drinking water and salt, chemicals (for example, acids and alkalis) used for adjusting pH during desalination are purchased separately from the outside. For this reason, when separately purchasing medicines from the outside, it is necessary to secure a storage place for them.

  This invention is made | formed in view of such a situation, manufacturing hydrochloric acid and sodium hydroxide in a desalination apparatus, without purchasing a chemical | medical agent from the outside, and desalinating using these. An object of the present invention is to provide a desalination apparatus and a desalination method, and a method for co-production of fresh water, salt and valuables.

A first invention that solves the above-mentioned problems includes a reverse osmosis membrane device that obtains fresh water from which salt in raw water has been removed and salt-enriched water in which salt in the raw water is concentrated, and concentrated brine and dilution from the salt-enriched water An electrodialysis section for obtaining brine, an evaporation crystallization section for evaporating and crystallization of the concentrated brine, a solid-liquid separation section for solid-liquid separation of the concentrated sodium chloride slurry from the evaporation crystallization section, and the solid-liquid The separated sodium chloride is dissolved in fresh water, the sodium chloride aqueous solution dissolved in the dissolution part is used to obtain a chlorine, hydrogen and sodium hydroxide aqueous solution, and the electrochemical treatment unit A hydrochloric acid production unit for producing hydrochloric acid from the generated hydrogen and chlorine , a hydrochloric acid supply line for supplying the hydrochloric acid to the inlet side of the reverse osmosis membrane device, and the temperature of the raw water at the inlet side of the reverse osmosis membrane device Temperature to measure With the door, as well as adjust the pH of the raw water in the hydrochloric acid, the measured temperature of the raw water at a thermometer, and characterized in that in response to the measured temperature to adjust the value of pH of the raw water in the hydrochloric acid In the desalination equipment.

According to the present invention, sodium hydroxide and hydrochloric acid can be produced using sodium chloride obtained from concentrated brine concentrated in the electrodialysis part. Moreover, pH suitable for filtration of a reverse osmosis membrane apparatus can be performed with hydrochloric acid. Conventionally, acid (for example, sulfuric acid, hydrochloric acid, etc.) was purchased separately and stored in the desalination system. However, hydrochloric acid can be supplied on-site, eliminating the need to purchase chemicals from outside. At the same time, storage facilities and the like are not necessary, and the production efficiency of fresh water production can be improved. In addition, by measuring the temperature of the raw water with a thermometer and adjusting the pH to an appropriate pH with hydrochloric acid according to the temperature, optimum fresh water treatment is always possible.

According to a second invention, in the first invention, a hydrochloric acid supply line for supplying the obtained hydrochloric acid into the desalination apparatus and a sodium hydroxide for supplying the obtained sodium hydroxide aqueous solution into the desalination apparatus It exists in the desalination apparatus provided with either one or both of aqueous solution supply line.

  According to the present invention, by collecting valuable chemicals such as hydrochloric acid and sodium hydroxide, which are chemicals, from sodium chloride and using them on-site, there is no need to purchase chemicals and storage facilities are no longer necessary. The production efficiency of the system can be improved.

  A third invention is the desalination apparatus according to the first or second invention, further comprising a hydrogen supply line for supplying the hydrogen obtained by the electrodialysis to a hydrochloric acid production unit.

  According to the present invention, hydrogen can be separately added in hydrochloric acid production, and the production of hydrochloric acid can be stably performed by the reaction in an excess hydrogen state.

According to a fourth invention, in any one of the first to third inventions, when the scale inhibitor is supplied to the raw water for desalination, the sodium hydroxide is supplied to the inlet side of the reverse osmosis membrane device. A desalination apparatus comprising a sodium aqueous solution supply line and adjusting the pH of raw water with the sodium hydroxide.

  According to the present invention, when supplying a scale inhibitor to raw water and filtering the reverse osmosis membrane device, it can be carried out with an aqueous sodium hydroxide solution as an agent for adjusting the pH to the alkali side. Previously, a separate alkali agent (sodium hydroxide) was purchased and stored in the desalination system, but this can be supplied on-site with an aqueous sodium hydroxide solution, eliminating the need to purchase chemicals from outside. In addition, storage facilities and the like are no longer necessary, and the production efficiency of fresh water production can be improved.

A fifth invention is the invention according to any one of the first to third aspects, wherein the reverse osmosis membrane device is in two stages in series, and between the first-stage reverse osmosis membrane device and the second-stage reverse osmosis membrane device. A desalination apparatus comprising a sodium hydroxide aqueous solution supply line for supplying the sodium hydroxide aqueous solution and removing boron in the fresh water desalinated in the first stage.

  ADVANTAGE OF THE INVENTION According to this invention, the boron in the fresh water desalinated with the reverse osmosis membrane apparatus can be removed.

According to a sixth aspect of the present invention, there is provided a desalination apparatus according to the first aspect, further comprising a first crystallization part for crystallizing and separating a salt from the diluted brine.

  According to the present invention, valuable substances (Mg salt, Ca salt, etc.) can be obtained from multivalent ions in concentrated water by crystallization in the first crystallization part.

A seventh aspect of the present invention is the desalination method according to the first aspect, further comprising a second crystallization part that crystallizes and separates a valuable substance from the sodium chloride removal slurry separated from the sodium chloride in the solid-liquid separation part. In the device.

  According to the present invention, valuable substances (K salt and the like) can be obtained from the sodium chloride removal slurry by crystallization in the second crystallization part.

According to an eighth invention, in any one of the first to seventh inventions, a hydrochloric acid supply line and a sodium hydroxide aqueous solution supply line for supplying the hydrochloric acid and sodium hydroxide into fresh water on the outlet side of the reverse osmosis membrane device. And the pH of fresh water is adjusted with either one or both of hydrochloric acid and sodium hydroxide.

  According to the present invention, the pH of fresh water can be adjusted using one or both of the obtained hydrochloric acid and sodium hydroxide aqueous solution, for example, to a pH suitable for beverages.

A ninth invention is characterized in that, using the desalination apparatus according to any one of the first to eighth inventions, salt is removed from raw water to obtain fresh water, and sodium chloride is obtained from the concentrated salt-concentrated water. It is in the co-production method of fresh water and salt.

  According to the present invention, valuable materials such as hydrochloric acid and sodium hydroxide are recovered using a part of sodium chloride generated in the desalination apparatus, and fresh water is recovered using the obtained hydrochloric acid and sodium hydroxide. Therefore, it is not necessary to purchase chemicals from the outside and storage facilities are not required, so that the production efficiency of production of fresh water and sodium chloride can be improved.

The tenth invention uses the desalination apparatus according to any one of the sixth to eighth inventions to remove the salt in the raw water to obtain fresh water, and to obtain a salt-enriched water (concentrated brine, diluted brine) after the desalination treatment. ) To obtain sodium chloride and valuables from the fresh water, salt and valuables.

  According to the present invention, valuable materials such as hydrochloric acid and sodium hydroxide are recovered using a part of sodium chloride generated in the desalination apparatus, and fresh water is recovered using the obtained hydrochloric acid and sodium hydroxide. Therefore, it is not necessary to purchase chemicals from the outside and storage facilities are not required, and the production efficiency of manufacturing fresh water, sodium chloride, and valuables can be improved.

Eleventh aspect of the electrical obtain a desalination step of salinity and salt in the raw water is removed fresh raw water to obtain a salinity concentrate that is enriched, and concentrated brine and diluted brine from the salt concentrated water dialysis A step of evaporating and crystallization of the concentrated brine, a step of solid-liquid separation of the concentrated sodium chloride slurry from the step of evaporating crystallization, and a step of separating the solid-liquid separated sodium chloride. A dissolution step of dissolving the sample in fresh water, an electrochemical treatment step using the aqueous sodium chloride solution dissolved in the dissolution step to obtain an aqueous solution of chlorine, hydrogen and sodium hydroxide, and hydrogen and chlorine obtained in the electrochemical treatment step , hydrochloric acid production process of producing hydrochloric acid from have a, the hydrochloric acid is fed to the inlet side of the desalination step, thereby adjusting the pH of the raw water in the hydrochloric acid, the at the entrance side of the desalination process The temperature of the water is measured, in accordance with the measured temperature, there the value of pH of the raw water to the desalination method characterized by adjusting in the hydrochloric acid.

According to the present invention, sodium hydroxide and hydrochloric acid can be produced using sodium chloride obtained from the concentrated brine concentrated in the electrodialysis step. Moreover, pH suitable for filtration of a reverse osmosis membrane process can be performed with hydrochloric acid. Conventionally, acid (sulfuric acid, hydrochloric acid) was purchased separately and stored in the desalination system, but this can be supplied with hydrochloric acid on-site, making it unnecessary to purchase chemicals from the outside. Storage facilities and the like are no longer required, and the production efficiency of fresh water production can be improved. In addition, by measuring the temperature of the raw water with a thermometer and adjusting the pH to an appropriate pH with hydrochloric acid according to the temperature, optimum fresh water treatment is always possible.

A twelfth invention is the desalination method according to the eleventh invention, wherein any one or both of the obtained hydrochloric acid and sodium hydroxide aqueous solution are used in the desalination step.

  According to the present invention, by collecting valuable chemicals such as hydrochloric acid and sodium hydroxide, which are chemicals, from sodium chloride and using them on-site, there is no need to purchase chemicals and storage facilities are no longer necessary. The production efficiency of the system can be improved.

A thirteenth invention is the desalination method according to the eleventh or twelfth invention, wherein the hydrogen obtained by the electrodialysis is supplied to a hydrochloric acid production step.

  According to the present invention, hydrogen can be separately added in hydrochloric acid production, and the production of hydrochloric acid can be stably performed by the reaction in an excess hydrogen state.

In a fourteenth aspect of the invention, in any one of the eleventh to thirteenth aspects, when the scale inhibitor is supplied to the raw water for desalination, the sodium hydroxide aqueous solution is supplied to the inlet side of the reverse osmosis membrane step, In the desalination method, the pH of the raw water is adjusted with the aqueous sodium hydroxide solution.

  According to the present invention, when a scale inhibitor is supplied to raw water and filtration in the reverse osmosis membrane mounting step is performed, sodium hydroxide can be used as a chemical for adjusting pH to the alkali side. In the past, a separate alkali agent (sodium hydroxide) was purchased and stored in the desalination system, but this can be supplied on-site with sodium hydroxide, eliminating the need to purchase chemicals from outside. At the same time, storage facilities and the like are not necessary, and the production efficiency of fresh water production can be improved.

A fifteenth aspect of the present invention is the invention according to any one of the eleventh to thirteenth aspects, wherein the desalination process is in two stages in series, and the water is disposed between the first stage desalination process and the second stage desalination process. A desalination method is characterized in that an aqueous sodium oxide solution is supplied and boron in fresh water desalinated in the first stage is removed.

  According to the present invention, boron in fresh water that has been desalinated in the reverse osmosis membrane process can be removed.

A sixteenth invention is the desalination method according to the eleventh invention, further comprising a first crystallization step of crystallizing and separating a salt from the diluted brine.

  According to the present invention, valuable substances (Mg salt, Ca salt, etc.) can be obtained from multivalent ions in the concentrated water by crystallization in the first crystallization step.

A seventeenth aspect of the present invention is the desalination according to the eleventh aspect of the present invention, further comprising a second crystallization step of crystallizing and separating valuable materials from the sodium chloride removal slurry from which sodium chloride has been separated in the solid-liquid separation step. Is in the way.

  According to the present invention, valuable substances (K salt and the like) can be obtained from the sodium chloride removal slurry by crystallization in the second crystallization part.

An eighteenth invention is characterized in that, in any one of the eleventh to seventeenth inventions, the pH of fresh water on the outlet side of the desalination step is adjusted by either one or both of hydrochloric acid and an aqueous sodium hydroxide solution. It is in the desalination method.

  According to the present invention, the pH of fresh water can be adjusted using one or both of the obtained hydrochloric acid and sodium hydroxide, for example, to a pH suitable for beverages.

  According to the present invention, an aqueous sodium hydroxide solution and hydrochloric acid can be produced using sodium chloride obtained from concentrated brine concentrated in the electrodialysis step. The obtained sodium hydroxide and hydrochloric acid can be used in the desalination step. This eliminates the need to purchase hydrochloric acid or sodium hydroxide chemicals from outside. As a result, by collecting valuable chemicals such as hydrochloric acid and sodium hydroxide, which are chemicals, from sodium chloride and using them on-site, there is no need to purchase chemicals, and no storage facilities are required. Efficiency can be improved.

FIG. 1 is a schematic view of a desalination apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic view of a desalination apparatus according to the second embodiment of the present invention. FIG. 3 is a schematic view of a desalination apparatus according to the third embodiment of the present invention. FIG. 4 is a schematic view of a desalination apparatus according to the fourth embodiment of the present invention. FIG. 5 is a schematic view of a desalination apparatus according to the fifth embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited to each following embodiment, It can implement by changing suitably. Moreover, the structure of the desalination apparatus which concerns on each embodiment can be implemented combining suitably.

(First embodiment)
FIG. 1 is a schematic diagram of a seawater desalination apparatus according to a first embodiment of the present invention.
As shown in FIG. 1, the seawater desalination apparatus 10 </ b> A includes fresh water W ₁₁ from which salt in the supplied seawater (raw water) W is removed and salt concentration in which the salinity in the supplied seawater (raw water) W is concentrated. a reverse osmosis unit 12 for obtaining the water W _12, the salt concentration water W ₁₂ to electrodialysis, the electrodialysis unit 13 to obtain a concentrated brine W ₁₃ and diluted brine W _14, to evaporation crystallization concentrated brine W ₁₃ an evaporation crystallization analyzing unit 21, dissolved and solid-liquid separation unit 22 for solid-liquid separation a concentrated sodium chloride slurry S ₁ from the evaporation crystallization analyzing unit 21, solid-liquid separated sodium chloride (NaCl) with fresh water W ₁₁ A dissolving part 29, an electrochemical treatment part 30 for obtaining a chlorine, hydrogen and sodium hydroxide (NaOH) aqueous solution using the dissolved sodium chloride aqueous solution, and hydrogen (H ₂ ) obtained in the electrochemical treatment part 30 chlorine (Cl ₂₎ from hydrochloric acid (HCl) 3 The hydrochloric acid production section 31 to produce hydrochloric acid supply line L ₂₅ using one or both of the resulting hydrochloric acid and aqueous sodium hydroxide in a desalination apparatus, as it has a sodium hydroxide aqueous solution supply line L ₂₆ is there.

In the present embodiment, a pretreatment device 11 that removes impurities and the like in the supplied seawater W is provided. The pre-processing unit 11, a suspension of such particles or colloids in sea water, and treated water W ₁₀ before microorganisms were removed, such as algae and shellfish, decrease water permeability of the reverse osmosis membrane 12a of the reverse osmosis unit 12 This is to suppress the phenomenon (fouling phenomenon). And this pre-processing apparatus 11 is a sand filter formed by adding chemical | medical agents, such as an inorganic type and an organic type coagulant | flocculant, a disinfectant, etc. in the supply seawater W, and filling the container as sand as a filter medium. Pass water to remove suspended matter and microorganisms in seawater. In addition, a backwash pump or the like for backwashing the sand filter to recover the filtration performance is provided. A biofilm may be formed on the surface of a carrier such as sand in the filter, and the pretreatment of seawater may be performed using both the filtration performance and the degradation performance of the BOD component by the biofilm. Note that, for example, when pretreated seawater is desalinated with respect to seawater used as cooling water for a plant, this pretreatment device may be omitted.

Reverse osmosis unit 12, using a reverse osmosis membrane 12a, through the pretreated water W ₁₀ pretreated, with obtaining fresh water W ₁₁ to remove the salt of the pretreated water W _10, the pretreated water W A salt-enriched water W ₁₂ in which the salt in ₁₀ is concentrated is obtained. The reverse osmosis membrane device 12 supplies the obtained fresh water W ₁₁ to the supply line L ₁₂ and discharges it as production water 14, and supplies the salt-enriched water W ₁₂ to the electrodialysis unit 13 via the supply line L _13. . Thus, by using a reverse osmosis membrane device 12, it is possible to obtain a fresh W ₁₁ as permeate reverse osmosis membrane 12a, a further energy consumption as compared with the case of obtaining fresh water by using a vaporizer Can be reduced. In the present embodiment, the electrodialysis unit 13 is installed on the downstream side of the reverse osmosis membrane device 12, but the present invention is not limited to this, and these arrangements may be reversed.

Here, as the reverse osmosis membrane device 12, for example, a plurality of reverse osmosis membrane elements (reverse osmosis membrane modules) are provided in a container, and fresh water W ₁₁ obtained by processing with each reverse osmosis membrane element is used. connect the retentate line for leading out (discharge) the salinity concentrate W ₁₂ from each container (concentrated water discharge path) and permeate pipe (freshwater discharge path) is arranged.

  As the reverse osmosis membrane 12a of the reverse osmosis membrane device 12, a general reverse osmosis (RO) membrane (hereinafter also referred to as “RO membrane”) or an NF (Nanofiltration) membrane (hereinafter also referred to as “NF membrane”). Etc. can be used.

Further, in this embodiment, to obtain a fresh W ₁₁ and salinity concentrated water W ₁₂ processes the supplied seawater W as the raw water in the reverse osmosis unit 12, other than seawater so long as it contains a salt Water may be used as raw water. As the supply seawater W, for example, pumped seawater, seawater once used in the plant as a refrigerant, or the like can be used.

The electrodialysis unit 13 includes an electrodialysis membrane (ED: Elecrodialysis membrane) 13a. Electrodialysis unit 13, salinity salinity concentrate W ₁₂ electrodialysis to salinity concentrate W ₁₂ salinity concentrate enriched brine W of ₁₃ and salt concentration water W in ₁₂ was removed by electrodialysis membrane 13a Diluted brine W ₁₄ is obtained.
As an electrodialysis method, for example, a cation exchange membrane that transmits only cations and an anion exchange membrane that transmits only anions are alternately arranged, and voltage is applied from both ends of the cation exchange membrane and the anion exchange membrane. It is configured so that a direct current can be applied by applying it. In the electrodialysis unit 13, concentrated obtained by treating the salt concentration water W ₁₂ brine W ₁₃ and diluted brine W _14, respectively, they are discharged by the discharge line L _14, L _15.

Here, the supply line L ₁₃ supplies the salinity concentrate W ₁₂ from the reverse osmosis unit 12 is partly branched into the electrodialysis unit 13 side, salinity concentrate W ₁₂ that is not branched, the feed line L ₁₃ It is discharged as waste water W ₂₀ to the outside through.

The evaporative crystallization unit 21 evaporates and crystallizes the concentrated brine W ₁₃ supplied from the electrodialysis unit 13 to obtain a salt (sodium chloride (NaCl)) and also obtains evaporated water W ₁₅ . Further, the evaporated water W ₁₅ from the evaporative crystallization unit 21 merges with the fresh water W ₁₁ via the supply line L ₁₆ and the supply line L ₁₂ and is discharged as the production water 14.

Here, the evaporative crystallization unit 21 can be exemplified by, for example, a multi-effect evaporator, a thin film evaporator or a drum dryer, and the discharge for discharging the precipitate sodium chloride slurry S ₁ obtained by the evaporation process. A line L ₁₇ is connected to the solid-liquid separator 22.

The solid-liquid separation unit 22 performs solid-liquid separation on the concentrated sodium chloride slurry S ₁ from the evaporative crystallization unit 21, and obtains sodium chloride (solid) 34 as a valuable material.
Further, the sodium chloride removal slurry S ₂ from which sodium chloride has been separated is discharged through the discharge line L ₁₈ .
Further, the separated sodium chloride is discharged through the discharge line L ₂₁ , and a part thereof is introduced into the dissolving part 29. The remaining sodium chloride (solid) 34 is discharged through the discharge line L ₂₂ as a valuable resource.

The dissolution unit 29 uses a part of the separated sodium chloride to dissolve with fresh water W ₁₁ to obtain a sodium hydroxide aqueous solution. For this dissolution, the fresh water W ₁₁ obtained by the desalination treatment and the evaporated water W ₁₅ are supplied from one or both of the supply lines L ₃₁ and L ₃₂ . Dissolved sodium chloride aqueous solution is supplied to the electrochemical processing unit 30 via a supply line L _23.

The electrochemical treatment unit 30 uses the supplied sodium chloride aqueous solution and performs, for example, an electrolytic treatment such as electrolysis or electrodialysis to provide a sodium hydroxide (NaOH) aqueous solution 33, hydrogen (H ₂ ), and chlorine (Cl ₂ ). Get.
Here, an aqueous solution of sodium 33 hydroxide is discharged by discharge line L ₂₄ from the electrochemical processing unit 30. Further, hydrogen (H ₂ ) and chlorine (Cl ₂ ) are discharged from the electrochemical processing unit 30 through the discharge lines L ₂₇ and L ₂₈ .

The hydrochloric acid production unit 31 obtains hydrochloric acid (HCl) 32 using hydrogen (H ₂ ) and chlorine (Cl ₂ ) obtained by electrochemical treatment as raw materials.
In order to adjust the concentration of the obtained hydrochloric acid 32, fresh water W ₁₁ supplied by the fresh water supply line L ₃₃ is used. It is also possible to adjust the concentration using evaporation water W _15.

In the present embodiment, the hydrochloric acid supply line L ₂₅ for supplying hydrochloric acid (HCl) 32 is connected to the seawater line L ₁₁ so as to be supplied to the inlet side of the reverse osmosis membrane device 12.

Further, a hydrochloric acid supply line L ₂₅ for supplying hydrochloric acid 32 and a sodium hydroxide aqueous solution supply line L ₂₆ for supplying sodium hydroxide aqueous solution 33 are connected to supply line L ₁₂ for discharging fresh water W ₁₁ .

In the pretreatment device 11, a hydrochloric acid supply line L ₂₅ for supplying hydrochloric acid 32 may be connected.

Further, in order to supply the hydrochloric acid 32 and the sodium hydroxide aqueous solution 33 for cleaning the reverse osmosis membrane device 12 when the desalination apparatus is shut down, the hydrochloric acid supply line L ₂₅ for supplying the hydrochloric acid 32 and the sodium hydroxide aqueous solution are supplied. The sodium hydroxide aqueous solution supply line L ₂₆ for supplying 33 may be connected to a predetermined cleaning line.

Next, the overall operation of the desalination apparatus 10A according to the present embodiment will be described.
The supplied seawater W is pretreated by the pretreatment device 11 interposed in the seawater line L ₁₁ , and the treated pretreatment water W ₁₀ is supplied to the reverse osmosis membrane device 12. The reverse osmosis unit prior supplied to 12 treated water W ₁₀ is salinity of the pretreated water W fresh W ₁₁ and pretreated water W in ₁₀ salt is removed in ₁₀ passes through the reverse osmosis membrane 12a It becomes a salinity concentrated water W ₁₂ enriched. The fresh water W ₁₁ is discharged through the supply line L ₁₂ and used as the production water 14. A part of the salt-concentrated water W ₁₂ is supplied to the electrodialysis unit 13 through the supply line L ₁₃ and a part thereof is discharged as waste water W ₂₀ .

The salt concentration water W ₁₂ supplied to the electrodialysis unit 13 is diluted by further concentrating the salt content in the salt concentration water W ₁₂ by the electrodialysis membrane 13a and removing the salt content in the concentrated brine W ₁₃ and the salt concentration water W _12. Brine W ₁₄ Here, the concentrated brine W ₁₃ is rich in monovalent salts (Na (sodium) salt, K (potassium) salt, etc.) contained in the salt-enriched water W ₁₂ . The diluted brine W ₁₄ is rich in polyvalent salts (Mg (magnesium) salt, Ca (calcium) salt, etc.) contained in the salt-enriched water W ₁₂ .

Further, by obtaining the evaporating water W ₁₅ from the concentrated brine W ₁₃ enriched with monovalent ions from the electrodialysis unit 13 by the evaporative crystallization unit 21, the production amount of the production water 14 can be further increased. . Further, as a result of evaporation, the concentrated sodium chloride slurry S ₁ is solid-liquid separated by the solid-liquid separator 22 to obtain valuable sodium chloride (NaCl) 34.

A part of the separated sodium chloride (NaCl) is subjected to electrochemical treatment in the electrochemical treatment unit 30 to obtain a sodium hydroxide (NaOH) aqueous solution 33, hydrogen (H ₂ ) and chlorine (Cl ₂ ). Get.

Using hydrogen (H ₂ ) and chlorine (Cl ₂ ) obtained by this electrochemical treatment as raw materials, hydrochloric acid (HCl) 32 is obtained in the hydrochloric acid production unit 31.
The concentration of the obtained hydrochloric acid 32 is appropriately adjusted by the fresh water W ₁₁ supplied through the fresh water supply line L ₃₃ .

  In the present embodiment, the pH suitable for the filtration of the reverse osmosis membrane device 12 can be adjusted on-site with the hydrochloric acid 32. In the past, acid (sulfuric acid, hydrochloric acid) was purchased separately, and the purchased chemicals were stored in the desalination plant. However, hydrochloric acid 32 can be supplied on-site and purchased from outside. Is not necessary, and storage facilities are not required, so that the production efficiency of fresh water production can be improved.

Further, since the hydrochloric acid supply line L ₂₅ and the sodium hydroxide supply line L ₂₆ for supplying the hydrochloric acid 32 and the aqueous sodium hydroxide solution 33 to the fresh water on the outlet side of the reverse osmosis membrane device 12 are provided, the obtained fresh water W ₁₁ The pH can be adjusted to an arbitrary pH value by either one or both of hydrochloric acid 32 and aqueous sodium hydroxide 33.

In particular, this adjustment can be easily performed when the pH of the obtained fresh water W ₁₁ is not a desired pH due to the desalination conditions.

Further, it is possible to use either one or both of the resulting hydrochloride 32 or sodium hydroxide solution 33 to adjust the pH of the fresh water W _11, adjusted to pH suitable for example beverages.

Further, in the present embodiment, the seawater supply line L ₁₁ on the entrance side of the reverse osmosis membrane device 12 is provided with a thermometer 40 that measures the temperature of the pretreated water W ₁₀ .
In particular, when the temperature of the supplied seawater W is high, it is preferable to adjust the pH by using hydrochloric acid 32.

When the water temperature of the pretreatment water W ₁₀ supplied to the inlet of the reverse osmosis membrane device 12 is set to operate at pH 7.2 when the water temperature is 30 ° C., for example, when the water temperature rises to 35 to 40 ° C. Is preferably operated to lower the pH value to about 7.0 to 6.8, for example. Therefore, it measures using the thermometer 40 by the control apparatus or worker which is not shown in figure, and controls the hydrochloric acid 32 to become desired pH. Thereby, a suitable desalination process can be continued.

In the desalination method of the present embodiment, to obtain a supply seawater (raw water) salinity concentrate W ₁₂ salinity enriched in salinity feed seawater freshwater W ₁₁ removed in W (raw water) in W a desalination process by the reverse osmosis unit 12, the salt concentration water W ₁₂ to electrodialysis, the electrodialysis step to obtain a concentrated brine W ₁₃ and diluted brine W _14, evaporation crystallization to evaporation crystallization concentrated brine W ₁₃ A solid-liquid separation step for solid-liquid separation of the concentrated sodium chloride slurry S ₁ from the evaporation crystallization step, a dissolution step for dissolving the solid-liquid separated sodium chloride in fresh water W ₁₁ , and a dissolved chloride An electrochemical treatment step for obtaining an aqueous solution of chlorine, hydrogen and sodium hydroxide using an aqueous sodium solution, and a hydrochloric acid production step for producing hydrochloric acid 32 from hydrogen and chlorine obtained in the electrochemical treatment step. Hydrochloric acid 32 and sodium hydroxide Either one or both of potassium solution 33 used in the desalination process.

Therefore, according to the desalination apparatus and method of this embodiment, the sodium hydroxide aqueous solution 33 and the hydrochloric acid 32 are produced using the sodium chloride 34 obtained from the concentrated brine W ₁₃ concentrated in the electrodialysis step. By using the obtained sodium hydroxide aqueous solution 33 and hydrochloric acid 34 in the desalination step, it is no longer necessary to separately purchase hydrochloric acid or sodium hydroxide chemicals from the outside. As a result, by collecting valuable chemicals such as hydrochloric acid and sodium hydroxide aqueous solution from sodium chloride and using them on-site, there is no purchase from the outside of the drug, and no storage facilities are required. The production efficiency of the system can be improved.

(Second Embodiment)
Next, a desalination apparatus according to the second embodiment of the present invention will be described. Below, it demonstrates centering around difference with the desalination apparatus which concerns on the said 1st Embodiment. In addition, about the component same as the desalination apparatus which concerns on the said 1st Embodiment, the same code | symbol is attached | subjected and duplication of description is avoided.

FIG. 2 is a schematic view of a desalination apparatus according to the second embodiment of the present invention.
As shown in FIG. 2, the desalination apparatus 10B according to the present embodiment uses hydrogen (H ₂ ) generated by the electrodialysis unit 13 in the desalination apparatus 10A of the first embodiment, and further generates hydrochloric acid production unit 31. A hydrogen supply line L ₂₉ for supplying to the battery is provided.

In the hydrochloric acid production section 31, hydrochloric acid (HCl) is produced from hydrogen (H ₂ ) and chlorine (Cl ₂ ), but in the decomposition in the electrochemical treatment section 30, the molar conversion production ratio is approximately 1: 1. Therefore, in order to stably produce hydrochloric acid as a hydrogen-excess reaction, hydrogen is separately supplied and reacted in a hydrogen-excess state.

At this time, since hydrogen (H ₂ ) generated in the electrodialysis unit 13 can be used to cover the desalination apparatus 10B, it is not necessary to purchase hydrogen separately.

(Third embodiment)
Next, a desalination apparatus according to the third embodiment of the present invention will be described. Below, it demonstrates centering around difference with the desalination apparatus which concerns on the said 1st Embodiment. In addition, about the component same as the desalination apparatus which concerns on the said 1st Embodiment, the same code | symbol is attached | subjected and duplication of description is avoided.

FIG. 3 is a schematic view of a desalination apparatus according to the third embodiment of the present invention.
As shown in FIG. 3, desalination apparatus 10C according to this embodiment, the desalination apparatus 10A of the first embodiment, further pre-processing water W ₁₀ supplies the scale inhibitor 41 processes desalination At the time, a sodium hydroxide aqueous solution supply line L ₂₆ for supplying the sodium hydroxide aqueous solution 33 is provided on the inlet side of the reverse osmosis membrane device 12, and the pH of the pretreatment water W ₁₀ is adjusted to the alkali side (for example, around pH 9) with the sodium hydroxide aqueous solution 33 ) To adjust. By increasing this pH, it is possible to improve the boron removal efficiency and improve the organic fouling suppressing effect.

According to the present invention, when the scale inhibitor 41 is supplied to the pretreated water W ₁₀ and the reverse osmosis membrane device 12 is filtered, the obtained sodium hydroxide aqueous solution 33 is used as a chemical for adjusting pH to the alkali side. It can be carried out.

  As a result, it is possible to solve the problem of separately purchasing an alkali agent (sodium hydroxide) and storing it in the desalination system as in the prior art. As a result, it is possible to supply sodium hydroxide on-site, which eliminates the need for purchasing chemicals from the outside and also eliminates storage facilities and the like, thereby improving the production efficiency of freshwater production.

(Fourth embodiment)
Next, a desalination apparatus according to the fourth embodiment of the present invention will be described. Below, it demonstrates centering around difference with the desalination apparatus which concerns on the said 1st Embodiment. In addition, about the component same as the desalination apparatus which concerns on the said 1st Embodiment, the same code | symbol is attached | subjected and duplication of description is avoided.

FIG. 4 is a schematic view of a desalination apparatus according to the fourth embodiment of the present invention.
As shown in FIG. 4, the desalination apparatus 10D according to the present embodiment is a first reverse osmosis membrane in which the reverse osmosis membrane apparatus 12 is arranged in two stages in the desalination apparatus 10A of the first embodiment. The device 12A and the second reverse osmosis membrane device 12B are used, and water for supplying the sodium hydroxide aqueous solution 33 between the first-stage first reverse osmosis membrane device 12A and the second-stage second reverse osmosis membrane device 12B. A sodium oxide aqueous solution supply line L ₂₆ is provided. Then, boron in the fresh water W ₁₁ subjected to the desalination treatment by the first reverse osmosis membrane device 12A is removed. Then, Na salt is removed as the salt concentration concentrated water W ₁₂ by the second reverse osmosis membrane device 12B, and the fresh water W ₁₁ from which boron is removed is obtained.

Therefore, the reverse osmosis membrane device 12 is arranged in two stages, the aqueous sodium hydroxide solution 33 is supplied between the first-stage reverse osmosis membrane device 12A and the second-stage reverse osmosis membrane device 12B, and alkaline conditions (for example, pH 9 Boron in the fresh water W ₁₁ can be efficiently removed.

(Fifth embodiment)
Next, a desalination apparatus according to the fifth embodiment of the present invention will be described. Below, it demonstrates centering around difference with the desalination apparatus which concerns on the said 1st Embodiment. In addition, about the component same as the desalination apparatus which concerns on the said 1st Embodiment, the same code | symbol is attached | subjected and duplication of description is avoided.

FIG. 5 is a schematic view of a desalination apparatus according to the fifth embodiment of the present invention.
As shown in FIG. 5, desalination apparatus 10E according to this embodiment, the desalination apparatus 10A of the first embodiment, further crystallization separates the salt from dilute brine W ₁₄ from the electrodialysis unit 13 A first crystallization unit 23 and a second crystallization unit 24 that crystallizes and separates valuable materials from the sodium chloride removal slurry S ₂ from which sodium chloride is separated by the solid-liquid separation unit 22 are provided.

Since the diluted brine W ₁₄ from the electrodialysis unit 13 contains multivalent ions (for example, Ca ions and Mg ions), the crystallization of the first crystallization unit 23 causes the dilution in the diluted brine W ₁₄ . A first valuable material (Mg salt, Ca salt, etc.) 51 can be obtained from the multivalent ions.

In the first crystallization analyzing unit 23, as an alkali agent for the reactive crystallization in alkaline conditions, a sodium hydroxide (NaOH) aqueous solution 33, is supplied via a sodium hydroxide aqueous solution supply line L _26.

Thereby, at the time of crystallization in the 1st crystallization part 23, sodium hydroxide can be added and the reaction crystallization of the alkali side can be performed, and magnesium hydroxide (Mg (OH) ₂ ) is obtained efficiently. be able to.

  As a result, it is possible to solve the problem of separately purchasing an alkali agent (sodium hydroxide) and storing it in the desalination system as in the prior art. As a result, it is possible to supply sodium hydroxide on-site, which eliminates the need for purchasing chemicals from the outside and also eliminates storage facilities and the like, thereby improving the production efficiency of freshwater production.

According to this embodiment, the reaction crystallization of the first crystallization part 23 is performed under alkaline conditions, and magnesium hydroxide (Mg (OH) ₂ ) that is a valuable material in the diluted brine W ₁₄ can be obtained efficiently. it can.

As described above, according to the desalination apparatus 10E according to the present embodiment, along with the manufacture of fresh water, valuable materials can be manufactured with high purity. At that time, the recovered sodium chloride is used to perform water treatment by the electrochemical processing unit 30. Sodium oxide is produced, and the produced sodium hydroxide is used as a first crystallization part 23 to cause reaction crystallization in an alkaline state, thereby obtaining high-purity magnesium hydroxide (Mg (OH) ₂ ). Can do.

Further, the second valuable material (K salt or the like) 52 can be obtained by crystallization in the second crystallization part 24 from the sodium chloride removal slurry S ₂ from which sodium chloride has been removed.
Incidentally, the supernatant water W ₁₇ above containing valuable materials in the evaporation crystallization analyzing unit 21 (K salt or the like) via the discharge line L _19, is introduced into the second crystallization analyzing unit 23, and is crystallized here.

Therefore, according to the desalination apparatus and method of the present embodiment, fresh water is produced and the polyvalent ions contained in the diluted brine W ₁₄ from the electrodialysis unit 13 are converted into the first valuable substances (Mg salt, Ca salt). Etc.) 51 can be recovered by the first crystallization part 23. Further, the second valuable material (K salt or the like) contained in the sodium chloride removal slurry S _{2 from} which sodium chloride has been removed can be recovered by the second crystallization unit 24. In this embodiment, the crystallization method is used for recovering valuable materials, but the present invention is not limited to this, and valuable materials may be recovered by an adsorption method.

Further, when the treated water from which this valuable material has been collected is circulated as circulating water W ₁₆ to the inlet side of the reverse osmosis membrane device 12 by the circulation line L ₃₀ , since the polyvalent ions have been removed, the reverse osmosis membrane device 12 The power of the high-pressure pump supplied to can be greatly reduced. In addition, since the multivalent ions are separated by the first crystallization part 23, there is no accumulation of multivalent ions (for example, Ca ²⁺ , SO ₄ ²⁻ ) in the recycled water W _16. Then, precipitation of scale (for example, CaSO ₄ etc.) at the reverse osmosis membrane 12a of the reverse osmosis membrane device 12 is prevented. Moreover, the purity of the valuables to collect can be improved. Thereby, the efficient co-production method of fresh water, salt, and valuables is realizable.

10A to 10E Desalination device 11 Pretreatment device 12 Reverse osmosis membrane device 12a Reverse osmosis membrane 13 Electrodialysis unit 13a Electrodialysis membrane 14 Production water 21 Evaporation crystallization unit 22 Solid-liquid separation unit 23 First crystallization unit 24 2nd Crystallization part 30 Electrochemical treatment part 31 Hydrochloric acid production part 32 Hydrochloric acid 33 Sodium hydroxide aqueous solution W Supply seawater W ₁₀ Pretreatment water W ₁₁ Fresh water W ₁₂ Concentrated salt water W ₁₃ Concentrated brine W ₁₄ Diluted brine W ₂₀ Drainage L ₁₁ Seawater Line L ₂₅ Hydrochloric acid supply line L ₂₆ Sodium hydroxide aqueous solution supply line L ₃₀ Circulation line

Claims (18)

A reverse osmosis membrane device for obtaining fresh water from which salt in raw water has been removed and salt-enriched water in which salt in raw water is concentrated;
An electrodialysis unit for obtaining concentrated brine and diluted brine from the salt-concentrated water ;
An evaporation crystallization part for evaporating and crystallization of the concentrated brine;
A solid-liquid separation unit for solid-liquid separation of the concentrated sodium chloride slurry from the evaporative crystallization unit;
A dissolution part for dissolving the solid-liquid separated sodium chloride with fresh water;
Using an aqueous sodium chloride solution dissolved in the dissolving portion, an electrochemical treatment portion for obtaining an aqueous solution of chlorine, hydrogen and sodium hydroxide,
A hydrochloric acid production unit for producing hydrochloric acid from hydrogen and chlorine obtained in the electrochemical treatment unit;
A hydrochloric acid supply line for supplying the hydrochloric acid to the inlet side of the reverse osmosis membrane device;

A thermometer for measuring the temperature of the raw water on the inlet side of the reverse osmosis membrane device,
While adjusting the pH of the raw water with the hydrochloric acid,
The desalination apparatus characterized by measuring the temperature of raw water with the thermometer and adjusting the pH value of the raw water with the hydrochloric acid according to the measured temperature . In claim 1,
One or both of a hydrochloric acid supply line for supplying the obtained hydrochloric acid into the desalination apparatus and a sodium hydroxide aqueous solution supply line for supplying the obtained sodium hydroxide aqueous solution into the desalination apparatus are provided. A desalinator characterized by. In claim 1 or 2,
A desalination apparatus comprising a hydrogen supply line for supplying hydrogen obtained by electrodialysis to a hydrochloric acid production unit. In any one of Claims 1 thru | or 3,
When desalting by supplying a scale inhibitor to the raw water, a sodium hydroxide aqueous solution supply line for supplying the sodium hydroxide is provided on the inlet side of the reverse osmosis membrane device, and the pH of the raw water is adjusted with the sodium hydroxide aqueous solution A desalination apparatus characterized by: In any one of Claims 1 thru | or 3,
The reverse osmosis membrane device has two stages in series, and a sodium hydroxide aqueous solution supply line for supplying the sodium hydroxide aqueous solution is provided between the first-stage reverse osmosis membrane device and the second-stage reverse osmosis membrane device, A desalination apparatus for removing boron from fresh water desalinated in the first stage. In claim 1,
A desalination apparatus comprising a first crystallization part that crystallizes and separates salt from the diluted brine. In claim 1,
A desalination apparatus comprising a second crystallization part for crystallizing and separating a valuable substance from a sodium chloride removal slurry separated from sodium chloride by the solid-liquid separation part. In any one of Claims 1 thru | or 7 ,
A hydrochloric acid supply line and a sodium hydroxide aqueous solution supply line for supplying the hydrochloric acid and the sodium hydroxide aqueous solution into fresh water on the outlet side of the reverse osmosis membrane device, and the pH of the fresh water is either hydrochloric acid or sodium hydroxide Or the desalination apparatus characterized by adjusting by both. A desalination apparatus according to any one of claims 1 to 8 , wherein salt water in raw water is removed to obtain fresh water, and sodium chloride is obtained from the concentrated salt concentration water. Production method. A desalination apparatus according to any one of claims 6 to 8 , wherein salt water in raw water is removed to obtain fresh water, and sodium chloride and valuable resources are obtained from the salt concentration concentrated water after desalination treatment. Co-production method of fresh water, salt and valuables. A desalination step of obtaining fresh water from which salt in the raw water has been removed and salinity concentrated water in which the salt in the raw water is concentrated;
And electrodialysis to obtain a concentrated brine and diluted brine from the salt concentration water,
An evaporation crystallization step of evaporating and crystallization of the concentrated brine;
A solid-liquid separation step for solid-liquid separation of the concentrated sodium chloride slurry from the evaporative crystallization step;
Dissolving the solid-liquid separated sodium chloride with fresh water;
Using the aqueous sodium chloride solution dissolved in the dissolving step, an electrochemical treatment step for obtaining an aqueous chlorine, hydrogen and sodium hydroxide solution;
Possess a hydrochloric acid production process of producing hydrochloric acid from the obtained hydrogen and chlorine in the electrochemical treatment process, a
Supplying the hydrochloric acid to the inlet side of the desalination step, adjusting the pH of the raw water with the hydrochloric acid,
A desalination method characterized in that the temperature of the raw water is measured at the inlet side of the desalination step, and the pH value of the raw water is adjusted with the hydrochloric acid according to the measured temperature . In claim 11 ,
One of the hydrochloric acid and sodium hydroxide aqueous solution obtained, or both are used in a desalination process, The desalination method characterized by the above-mentioned. In claim 11 or 12 ,
A desalination method characterized by supplying hydrogen obtained by the electrodialysis step to a hydrochloric acid production step. In any one of Claims 11 thru | or 13 ,
When desalinating by supplying a scale inhibitor to raw water, the sodium hydroxide aqueous solution is supplied to the inlet side of the desalination step, and the pH of the raw water is adjusted with the sodium hydroxide aqueous solution. Method. In any one of Claims 11 thru | or 13 ,
The desalination process is set in two stages in series, and the sodium hydroxide aqueous solution is supplied between the first stage desalination process and the second stage desalination process, and the fresh water desalinated in the first stage is supplied. A desalination method characterized by removing boron. In claim 11 ,
A desalination method comprising a first crystallization step of crystallizing and separating a salt from the diluted brine. In claim 11 ,
A desalination method comprising a second crystallization step of crystallizing and separating a valuable material from a sodium chloride removal slurry from which sodium chloride has been separated in the solid-liquid separation step. In any one of Claims 11 thru | or 17 ,
A desalination method, wherein the pH of fresh water on the outlet side of the desalination step is adjusted by one or both of hydrochloric acid and a sodium hydroxide aqueous solution.

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