JP2003088863A - Method for producing mineral-containing liquid and equipment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a mineral-containing liquid from seawater and equipment therefor by which the operation from intake of seawater or marine deep water to preparation of a mineral-containing liquid having the objective concentration and hardness can be efficiently carried out in a series of processes at a low cost. SOLUTION: The method for producing a mineral-containing liquid has a step for separating seawater into softened seawater and hardened seawater with a nanofilter membrane.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and apparatus for producing a mineral-containing liquid containing mineral components such as calcium and magnesium from seawater.

[0002]

2. Description of the Related Art In recent years, seawater contains various mineral (inorganic) components in a well-balanced manner, and in particular, the deep seawater taken from a depth of 200 m or more is clear, so that health drinks, pharmaceuticals, cosmetics, foods, beauty products, Utilization in fields such as livestock and marine industries is under consideration. At present, the effects of inorganic ions in vivo are still largely unknown, and one of the in vivo effects of mineral balance is that the ratio of magnesium to calcium intake is closely related to the prevention of cardiovascular diseases. Research results and test results in experimental animals (mouse) are presented. However, due to the fact that the ionic composition of plasma in the living body is close to that of seawater, the progress of measurement technology for trace elements and the elucidation of the behavior of intracellular molecular species in the future, multi-faceted aspects such as biochemistry, nutrition and physiology It is expected that the development will stand out.

When used in any field, in the conventional method, the taken seawater is concentrated by evaporative concentration to remove sodium chloride by crystallization, and the water containing the remaining mineral components is purified to obtain minerals. The feature is to obtain the contained liquid.

However, in the conventional method, since the residual seawater from which sodium chloride has been removed is used as the raw material, the amount of impurities should be kept extremely small, and the content of mineral components should be adjusted to a concentration and hardness suitable for the intended use. Is not easy. Therefore, there is a problem that water having a target concentration of mineral components or a target hardness cannot be prepared.
In addition, even if it could be prepared, it was not possible to adjust the concentration and hardness with high accuracy in the purification stage of seawater.
There is a problem in that it is necessary to thirdly adjust the concentration and hardness, productivity is extremely deteriorated, and a process with a large energy consumption such as evaporative concentration and electrodialysis is used, resulting in high cost.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to efficiently prepare a mineral-containing liquid having a target concentration and hardness by using seawater in a series of processes at low cost. (EN) A method and an apparatus for producing a mineral-containing liquid from seawater, which can be performed. Furthermore, the subject of the present invention is
It is an object of the present invention to provide a method and a device capable of accurately adjusting the concentration and hardness of mineral-containing water by using deep seawater which is one of clean seawater as raw water.

[0006]

In order to solve the above problems, the method for producing a mineral-containing liquid of the present invention is characterized by comprising a step of separating seawater into softened seawater and hardened seawater by a nanofiltration membrane. To do. Here, the softened seawater is seawater in which the proportion of alkaline earth metal ions in the total inorganic salts contained is reduced as compared with the seawater which is the raw water, and the hardened seawater is compared with the seawater which is the raw water. Then, it is seawater in which the proportion of alkaline earth metal ions in the total inorganic salts contained is increased. In addition, minerals are inorganic salts containing calcium ions and magnesium ions.

Further, the apparatus for producing a mineral-containing liquid of the present invention is characterized by having a seawater intake means and a nanofiltration membrane.

In the conventional method of removing sodium chloride by crystallization by evaporation and concentration, in addition to the problem of high cost as described above, when removing sodium chloride by crystallization, important mineral components such as magnesium sulfate are removed. There was a problem that some of them would be removed together. On the other hand, in the present invention, by utilizing the difference between the blocking rate of alkaline earth metal ions and the blocking rate of sodium ions in the nanofiltration membrane, sodium chloride is reduced and mineral content is increased compared to seawater which is raw water. Since the cured hardened seawater is obtained, a high-mineral content liquid can be efficiently obtained.

The nanofiltration membrane is a nanofiltration (NF = Na) which is a membrane separation process located between ultrafiltration and reverse osmosis.
Membrane used for no Filtration). Compared with the reverse osmosis membrane, the nanofiltration membrane has a lower removal rate of monovalent ions, but has a similarly high removal rate of polyvalent ions and natural organic substances represented by humic substances. Further, it has a characteristic that the pure water permeability coefficient is higher than that of the reverse osmosis membrane under the condition of low pressure. A separation membrane is used in which the charge and the molecular weight cutoff are controlled according to the raw water to be separated.

As a material for the nanofiltration membrane, a polyamide-based material,
A polypiperazine amide type, a polyester amide type, or a cross-linked product of a water-soluble vinyl polymer can be used, and its film structure has a dense layer on at least one side of the film, and from the dense layer to the inside of the film or another Those that have fine pores with gradually increasing pore size toward one side of the membrane (asymmetric membrane), and those that have a very thin separation functional layer formed of another material on the dense layer of such asymmetric membrane ( Composite membranes) and the like can be used. A composite membrane is preferable in order to obtain a high amount of water produced at a low pressure, and a polyamide-based composite membrane is more preferable in terms of the amount of permeated water, chemical resistance and the like. Among them, the piperazine polyamide-based composite membrane is particularly preferable.

On the other hand, the reverse osmosis membrane may be any as long as it can selectively permeate the solvent (water molecule) in the solution and block the permeation of the solute (salt). As the film structure, for example, an asymmetric film having a dense layer on at least one surface of the film and formed with fine pores whose diameter gradually increases from the dense layer to the opposite surface, or a dense layer of this asymmetric film Composite membranes with a thin active layer of another material on top can be used. And as the material of the film, cellulose acetate polymer, polyamide, polyester, polyimide,
And polymeric materials such as vinyl polymers can be used. Typical reverse osmosis membranes include a cellulose acetate-based or polyamide-based asymmetric membrane, a composite membrane having a composite membrane having a polyamide-based or polyurea-based active layer, and a composite membrane having an aromatic polyamide-based active layer. Is mentioned. Among them, an aromatic polyamide-based composite membrane that exhibits stable performance with respect to changes in water quality and can preferably remove harmful substances such as environmental hormones typified by trihalomethane is particularly preferable.

The nanofiltration membrane or reverse osmosis membrane as described above is a spiral type element in which a flat membrane-like membrane is wound around a water collecting pipe, or a plate type support plate with flat membranes on both sides is a spacer. A plate-and-frame type element that is laminated at regular intervals through a module to form a module, and further, a tubular type element that uses a tubular membrane, and a hollow fiber membrane element that bundles hollow fiber membranes and stores them in a case. can do. Further, one or more of these elements are connected in series in a pressure resistant container for use. The element may have any form, but from the viewpoint of operability and compatibility, it is preferable to use the spiral type element. The number of elements can be set arbitrarily according to the membrane performance. When the spiral type element is used, the number of elements loaded in one module is preferably about 6 in series.

As the nanofiltration membrane, it is preferable to use a membrane in which the rejection rate of magnesium sulfate, which is one of the important mineral components, is higher than that of sodium chloride, which is the main component of seawater. It is more preferable that the rejection rate of magnesium sulfate is 1.3 times or more that of sodium chloride, because the separation efficiency is high. The higher the rejection ratio, the better, but the more preferred range is 1.5 times or more, and more preferably 3 times or more.

In the above method, the seawater to be taken in may be ordinary surface seawater, but seawater taken deep from a depth of 200 m or more (also referred to as deep seawater or deep seawater).
Is more preferably used. Compared with surface seawater, deep seawater has less suspended solids, and the relative illuminance (relative to the illuminance on the sea surface) is 1% or less, which reflects low temperatures and microbial contamination that causes equipment operation troubles. Hateful. Therefore, it is not necessary to sterilize the device with a disinfectant such as hypochlorite or acid, which is indispensable for normal surface seawater. Therefore, it is possible to keep the operating cost low, and it is possible to produce a safe and high-quality mineral-containing liquid without mixing these germicides when preparing a high-mineral-containing liquid. I can.

The method for separating the seawater into softened seawater and hardened seawater by the nanofiltration membrane preferably has a step of returning at least a part of the hardened seawater to the raw water side of the nanofiltration membrane. By using at least a part of the hardened seawater again as raw water, the production efficiency of the high mineral content liquid is dramatically improved. In addition, this makes it possible to select various nanofiltration membranes. In order to reuse at least a part of the hardened seawater as raw water again, there are a multistage method and a circulation method, and an optimum method can be selected according to the treatment space, the installation cost, and the production amount. From the viewpoint of making the processing space compact, the circulation method is more preferable. Specifically, for example, a valve or the like may be provided in a line through which the cured seawater in the latter stage of the nanofiltration membrane passes, and a line for returning the cured seawater from the valve to the raw water layer provided in the preceding stage of the nanofiltration membrane may be provided. .
You may return only a part of the hardened seawater and take out the rest as product water, or you may return the whole amount to the raw water layer for circulation treatment, and when the water in the raw water layer reaches the target water quality, The mineral-containing liquid may be taken out from the raw water storage tank and used as product water. In the case of returning only a part, it is possible to change the concentration of the contained mineral component more variously by changing the ratio (recovery rate) of the returned flow rate. Of course, it is also possible to separate seawater into softened seawater and hardened seawater by separation with a single-stage nanofiltration membrane.

Furthermore, it is desirable to have a step of separating the softened seawater separated by the nanofiltration membrane into fresh water and concentrated water by the reverse osmosis membrane. By effectively using softened seawater, wasteful wastewater can be reduced. In addition, concentrated water has a large content of sodium ions and is an effective raw material for the salt industry. The fresh water obtained here can be used as drinking water as it is, or can be used for adjusting the concentration of the mineral-containing liquid.

The method of the present invention preferably has a step of adding water to the raw water side of the nanofiltration membrane to adjust the mineral concentration. With this, the concentration of the contained mineral component and the resulting hardness can be freely controlled to a target value. The mineral concentration may be adjusted by adding water after obtaining the mineral-containing liquid, but adding water to the raw water side of the nanofiltration membrane to obtain the desired mineral concentration of the mineral-containing water after filtration. By adjusting so that the value becomes, it is possible to suppress the generation of scale of minerals in the filtration membrane, and to perform stable nanofiltration membrane treatment. Any water can be used as the water added to the raw water side. Examples include natural water such as rainwater and river lake water,
Examples include tap water, distilled water, reverse osmosis membrane treated water, and mineral mixed water. The sodium ion concentration of the added water is 160
It is desirable that the content is ppm or less. If water having a sodium ion concentration of more than 160 ppm is added to the raw water side, the efficiency of membrane separation becomes poor. Further, it is more efficient to use a line for returning the fresh water separated from the softened seawater by the reverse osmosis membrane to the raw water layer and using it as added water to the raw water.

The high mineral content liquid obtained by the above-mentioned method is characterized in that the content of sodium chloride is 70% or less of the total inorganic salt components. It is preferably 50% or less, more preferably 20% or less. Here,% is% by weight.

The mineral-containing liquid produced by such a method and apparatus can be used for various purposes. For example, it is used as a food additive for drinking water, foods, etc., as a mineral additive for pharmaceuticals and cosmetics, and also for use in thalassotherapy, pools, baths, etc. in the beauty and health fields, livestock and soil. It can be applied to all fields such as agricultural fields such as improvement.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a preferred embodiment of a transit type apparatus as a mineral-containing liquid producing apparatus according to the present invention. In FIG. 1, first, the deep seawater intake device 1 takes in the deep seawater, and the taken deep seawater is sent to the filtration step. In the present embodiment, in the filtration step, the deep sea water is first filtered by the sand filtration device 2 and then by the microfiltration membrane device 3 which can be filtered with higher accuracy. By this method, foreign substances, impurities, suspended substances and microorganisms in the deep sea water are filtered with high precision, and very clean deep sea water is obtained. This clean deep seawater
As such, it can also be used for live fish tank water and the use of sea bathing facilities.

Next, the clean deep seawater is sent to the nanofiltration membrane separation step and separated into the softened seawater 6 and the hardened seawater 7 by the nanofiltration membrane separation device 5. The softened seawater 6 has high purity as sodium chloride, and can be used as it is as a raw material for the salt industry.

The softened seawater 6 separated by nanofiltration is sent to the reverse osmosis membrane device 9 through the pressure control valve 8 and separated into fresh water 10 and concentrated water 11 having a high sodium ion concentration. The separated fresh water 10 itself can be used as drinking water, pool water, bath water, shower water, and water for plants.

In the process shown in FIG. 1, the hardened seawater 7 is further sent to the mixing device 13 in the concentration adjusting step, if necessary. In the mixing device 13, the above-mentioned hardening seawater 7
And the above-mentioned softened seawater and the separated fresh water 10 are mixed. The mixing ratio may be determined such that the water after mixing has the concentration of mineral components required for the application or the hardness of water. As a result, product water adjusted to the target concentration and hardness can be obtained.

FIG. 2 is a schematic configuration diagram showing a preferred embodiment of a circulation type apparatus as the apparatus for producing a mineral-containing liquid according to the present invention. In FIG. 2, first, deep seawater is taken in by the deep seawater intake device 1 in the water intake process, and the taken deep seawater is sent to the filtration process. In the present embodiment, in the filtration step, the deep sea water is first filtered by the sand filtration device 2 and then by the microfiltration membrane device 3 which can be filtered with higher accuracy. By this method, foreign substances, impurities, suspended substances and microorganisms in the deep sea water are filtered with high precision, and very clean deep sea water is obtained. This clean deep seawater can be used as it is or for the purpose of live fish tank water or sea bath facilities.

Next, the above-mentioned clean deep seawater is sent from the membrane-treated raw water storage tank 14 to the nanofiltration membrane separation step, and is separated into the softened seawater 6 and the hardened seawater 7 by the nanofiltration membrane separation device 5. The softened seawater 6 has high purity as sodium chloride, and can be used as it is as a raw material for the salt industry. The hardened seawater 7 is returned to the raw water storage tank 14 via the return line.

The softened seawater 6 separated by nanofiltration is sent to the reverse osmosis membrane device 9 through the pressure control valve 8 and separated into fresh water 10 and concentrated water 11 having a high sodium ion concentration. The separated fresh water 10 itself can be used as drinking water, pool water, bath water, shower water, and water for plants. In the process shown in FIG. 2, the fresh water 10 is further returned to the raw water storage tank 14 of the nanofiltration process.

Further, in the process shown in FIG. 2, the raw water storage tank 14 is supplied with water as needed. The amount of water supplied may be determined so that the water obtained in the subsequent filtration step has the concentration of the mineral component required according to the use or the hardness of the water. When the water in the raw water storage tank reaches the target water quality, the high mineral content liquid is taken out from the discharge valve of the raw water storage tank 14 to obtain product water adjusted to an appropriate concentration and hardness.

FIG. 3 shows a mineral-containing liquid manufacturing apparatus according to the present invention, in which a plurality of circulation type filtration steps of FIG. 2 are arranged in parallel.
It is a schematic structure figure showing one desirable mode of a parallel circulation type device. In FIG. 3, first, deep seawater is taken in by the deep seawater intake device 1 in the water intake process, and the taken deep seawater is sent to the filtration process. In the present embodiment, in the filtration step, the deep sea water is first filtered by the sand filtration device 2 and then by the microfiltration membrane device 3 which can be filtered with higher accuracy.

Next, the above-mentioned clean deep seawater is sequentially sent by the switching valve 15 to a plurality of nanofiltration separation devices similar to those shown in FIG. Since the manufacturing process of FIG. 2 is a batch process, the intake of deep seawater and the supply of seawater to the storage tank 14 can be performed only intermittently. However, by using the nanofiltration device in parallel, continuous manufacturing is possible. This makes it possible to significantly increase manufacturing efficiency.

In the method for producing a mineral-containing liquid according to the present invention as described above, the production of a high-mineral-containing liquid from the intake of seawater, and further the mineral-containing liquid adjusted to a target concentration of mineral components and a target hardness. The production of the liquid is achieved by a series of processes without requiring steps such as evaporative concentration, crystallization and centrifugation. Therefore, the production process up to the manufacture of the final product is performed extremely efficiently.

The high-mineral content liquid or the concentration-adjusted mineral-containing liquid produced as described above holds various mineral components contained in the deep seawater in a well-balanced manner. There are more than 100 kinds of mineral components contained, and typical ones are magnesium, calcium, potassium, zinc and the like.

As described above, the mineral-containing liquid according to the present invention containing various mineral components with extremely few impurities in a well-balanced manner can be used for various purposes.

For example, it can be used in the fields of cosmetics and beauty, as well as bath salts, thalassotherapy and bath water. The concentration of the mineral-containing liquid can be appropriately selected or set according to the purpose.

Further, the mineral-containing liquid according to the present invention can be applied to foods, especially additives for health foods and processed foods for supplements. The mineral-containing liquid of the present invention is particularly low in impurities, and since it is possible to accurately adjust a well-balanced mineral component to a desired concentration,
It can also be suitably used in the fields of these foods and the like. Furthermore, it can be applied to the livestock field and the agricultural field such as hydroponics and soil improvement.

[0036]

[Examples] In the following Examples and Comparative Examples, a case was described in which a piperazine polyamide composite membrane was used as a nanofiltration membrane and a spiral wound element using a polyamide composite membrane was used as a reverse osmosis membrane. The present invention is not limited to these examples. (Example 1) Water was made using the water making apparatus shown in FIG.

First, raw water (seawater having a salt concentration of 3.5% by weight)
After passing water through the filtration device (2 and 3), the booster pump 4
At 2.0 MPa, the pressure was increased to 2.0 MPa and the nanofiltration membrane module 5 was supplied to obtain softened seawater 6 and hardened seawater 7 at a recovery rate of 70%. That is, with respect to the raw water 100, the softened seawater 70,
Separation was carried out at a ratio of 30 cured seawater. The concentration of the evaporation residue of the softened seawater 6 was about 23,000 mg / l. Hardened seawater 7
No precipitation of scale was observed. In addition, as the nanofiltration membrane module unit 5, 500 mg / l of N
When the aCl solution was operated at a pressure of 0.5 MPa, the desalination rate was 85%, the amount of water produced by the membrane was 1.20 m ³ / m ² / d, and 50
When a 0 mg / l MgSO ₄ solution was operated at a pressure of 0.5 MPa, the desalination rate was 99%, and the amount of water produced by the membrane was 1.35 m ³ / m ^2.
Six spiral type elements using a nanofiltration membrane having a performance of / d were connected in series and incorporated in a pressure vessel.

The softened seawater 6 is 9.0MP by the high pressure pump 8.
After the pressure was increased to a, water was passed through the reverse osmosis membrane module unit 9. The reverse osmosis membrane module 9 has a salt concentration of 3.5% by weight.
Desalination rate of 9 when operating seawater at a pressure of 5.5 MPa
A spiral type reverse osmosis membrane element using a reverse osmosis membrane having a performance of 9.85% and a membrane water production amount of 0.75 m ³ / m ² / d is connected in series and stored in a pressure vessel. I was there. Permeate recovery rate of reverse osmosis membrane module unit is 80
%, And the total solute concentration of permeated water is 180 mg / l
(Sodium ion concentration 70 ppm).

While the sodium chloride component ratio in the inorganic salt of the raw water, seawater, is 83%, the sodium chloride component ratio in the inorganic salt of the mineral-containing liquid obtained by this treatment is reduced to 67%. did. (Example 2) Water was made using the water making apparatus shown in FIG.

First, raw water (seawater having a salt concentration of 3.5% by weight)
After passing water through the filtration devices (2 and 3), it was once stored in the storage tank 14. Next, the raw water extracted from the storage tank 14 was pressurized to 2.0 MPa by the pressurizing pump 4 and supplied to the nanofiltration membrane module 5, and the softened seawater 6 and the hardened seawater 7 were obtained at a recovery rate of 70%. Concentration of evaporation residue of softened seawater 6 is about 2
It was 3,000 mg / l. No precipitation of scale was found in the hardened seawater 7. As the nanofiltration membrane module 5, a 500 mg / l NaCl solution was added to 0.5 M.
When operated at a pressure of Pa, the desalination rate is 85%, the amount of water produced in the membrane is 1.20 m ³ / m ² / d, and the amount of MgS is 500 mg / l.
Six spiral type elements using a nanofiltration membrane having a desalination rate of 99% and a membrane water production rate of 1.35 m ³ / m ² / d when the O ₄ solution was operated at a pressure of 0.5 MPa were connected in series. The one which was connected to the above and incorporated into a pressure vessel was used. The cured seawater was returned to the storage tank 14 at 3 m ³ / h by the return line.

The softened seawater 6 is 9.0MP by the high pressure pump 8.
After the pressure was increased to a, water was passed through the reverse osmosis membrane module unit 9. The reverse osmosis membrane module unit 9 has a salt concentration of 3.
Spiral reverse osmosis using a reverse osmosis membrane having a performance of a desalination rate of 99.85% and a membrane production amount of 0.75 m ³ / m ² / d when operating 5 wt% seawater at a pressure of 5.5 MPa. Six membrane elements connected in series and housed in a pressure vessel were used. The permeated water recovery rate of the reverse osmosis membrane module unit reached 80%, and the water quality of the fresh water 10 had a total solute concentration of 180 mg / l (sodium ion concentration 70 ppm). The fresh water 10 was returned to the storage tank 14 at 5.6 m ³ / h by the return line.

While the sodium chloride component ratio in the inorganic salt of the raw water, seawater, is 83%, the treated water (mineral-containing liquid) of 10 m ³ pumped out to the storage tank 14 by this treatment is inorganic. The component ratio of sodium chloride in the salt is
It decreased to 74% (after 1 hour) and 67% (after 2 hours).

That is, by carrying out continuous operation for 2 hours under the above conditions, a mineral-containing liquid having a sodium chloride content of 70% or less of the total inorganic salt component could be obtained. (Example 3) Water was produced using the water producing apparatus shown in FIG. In FIG. 3, four columns of nanofiltration membrane module units 5 were arranged in parallel as a nanofiltration membrane device, and a pump 8 and a reverse osmosis membrane module unit 9 were respectively arranged in the subsequent stages.
Others were the same as those of the fresh water generator shown in FIG.

The same operation as in Example 2 was carried out, and the storage of seawater (1 hour), the membrane filtration operation (2 hours), and the extraction of the mineral-containing liquid (1 hour) were shifted by 1 hour for the series of 4 rows. By performing alternately, the production amount of the mineral-containing liquid per day could be stably supplied.

[0045]

As described above, according to the method and the apparatus for producing a mineral-containing liquid from deep seawater of the present invention, a desired mineral-containing liquid containing extremely few impurities and a well-balanced mineral component can be obtained. It can be efficiently manufactured by a series of processes. Also in the adjustment of mineral components, the space occupation can be omitted as compared with the multi-step method, and a highly efficient system can be constructed.

Further, the concentration of the mineral component and the hardness of the mineral-containing liquid can be adjusted easily and highly accurately according to the use, and the optimum mineral-containing liquid can be supplied according to the use.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for producing a transient mineral-containing liquid according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a circulating-type mineral-containing liquid manufacturing apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a parallel circulation type mineral-containing liquid manufacturing apparatus according to an embodiment of the present invention.

[Explanation of symbols]

1 Deep Sea Water Intake Device 2 Sand Filtration Device 3 Ultrafiltration Membrane Device 4 High Pressure Pump 5 Nanofiltration Membrane Separation Device 6 Softened Seawater 7 Hardened Seawater 8 Pressure Adjustment Valve 9 Reverse Osmosis Membrane Separation Device 10 Freshwater 11 Concentrated Water with High Sodium Ion Concentration (High Na concentration water) 12 Product (water) 13 Mixing device 14 Membrane separation raw water storage tank 15 Switching valve

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) A61K 35/02 A61K 35/02 4D006 A61P 9/00 A61P 9/00 43/00 125 43/00 125 B01D 61 / 02 500 B01D 61/02 500 61/58 61/58 F term (reference) 4B017 LC03 LK02 LP01 LT05 4B018 LB08 LE05 MD01 MF01 4C083 AA161 AA162 AB051 AB052 AB501 AB502 CC25 DD23 DD27 EE42 4C087 BA01 CA01 MA17 NA14 A71 C4 ZC21 Z4C71 BB01 BC18 DD17 EE24 GG03 4D006 GA03 GA04 HA01 HA21 HA41 HA61 KA02 KA53 KA55 KA57 KA63 KA64 KA67 KB15 KE11R KE12R MA01 MA02 MA03 MB06 MC18 MC48 MC54X MC58 PA01 PA02 PB03

Claims (13)

[Claims] 1. A method for producing a mineral-containing liquid, which comprises a step of separating seawater into softened seawater and hardened seawater with a nanofiltration membrane. 2. The method for producing a mineral-containing liquid according to claim 1, further comprising the step of returning at least a part of the separated hardened seawater to the raw water side. 3. The method for producing a mineral-containing liquid according to claim 1, further comprising a step of separating the separated softened seawater into fresh water and concentrated water by a reverse osmosis membrane. 4. The method for producing a mineral-containing liquid according to claim 3, further comprising the step of returning fresh water separated by the reverse osmosis membrane to the raw water side of the nanofiltration membrane. 5. The method for producing a mineral-containing liquid according to claim 1, further comprising the step of adding water having a sodium ion concentration of 160 ppm or less to the raw water side of the nanofiltration membrane. 6. The method for producing a mineral-containing solution according to claim 1, wherein the nanofiltration membrane is a membrane having a higher rejection rate of magnesium sulfate than that of sodium chloride. 7. The method for producing a mineral-containing liquid according to claim 1, wherein the seawater is deep seawater taken from a depth of 200 m or more. 8. A mineral-containing liquid produced by the method according to claim 1, wherein the proportion of sodium chloride is 70% or less of the total inorganic salt components. 9. An apparatus for producing a mineral-containing liquid, comprising seawater intake means and a nanofiltration membrane. 10. A means for returning the hardened seawater separated by the nanofiltration membrane to the raw water side of the nanofiltration membrane.
The apparatus for producing a mineral-containing liquid as described in 1. 11. The apparatus for producing a mineral-containing liquid according to claim 9, further comprising a reverse osmosis membrane that separates the softened seawater separated by the nanofiltration membrane into fresh water and concentrated water, at a stage subsequent to the nanofiltration membrane. 12. A means for returning the fresh water separated by the reverse osmosis membrane to the raw water side of the nanofiltration membrane.
5. The apparatus for producing a mineral-containing liquid according to any one of 1. 13. The apparatus for producing a mineral-containing liquid according to claim 9, further comprising a means for adding water in a preceding stage of the nanofiltration membrane.