WO2008053700A1

WO2008053700A1 - Method of desalting, apparatus for desalting, and bubble generator

Info

Publication number: WO2008053700A1
Application number: PCT/JP2007/070126
Authority: WO
Inventors: Takashi Osugi; Yoichi Ikemoto
Original assignee: Sekisui Chemical Co., Ltd.
Priority date: 2006-10-30
Filing date: 2007-10-16
Publication date: 2008-05-08
Also published as: JP2008307522A

Abstract

A method of desalting which comprises generating fine bubbles in a raw water containing a salt and subjecting the raw water containing the fine bubbles to filter membrane separation. By the method, even when an operating pressure to be applied on the raw-water side is low, a sufficient effective pressure acts on the filter membrane to enable the water to be efficiently filtered. Even with an operating pressure on almost the same level as conventional ones, treated water can be obtained in a larger amount. Also provided is a desalting apparatus which comprises a storage means (1), a supply means (2), and a bubble generator (8) which generates fine bubbles in a raw water to be fed through a pressurizing means (3), and in which the raw water containing the fine bubbles is separated with a filter membrane by means of a separation means (4) disposed downstream from the bubble generator (8).

Description

Specification

Desalination treatment method, desalination treatment apparatus, and bubble generation apparatus

Technical field

[0001] The present invention relates to a technique for separating impurities from a liquid containing impurities using membrane separation, and in particular, a desalination treatment method and desalting suitable for desalination of seawater or brine (low-concentration brine). The present invention relates to a salt processing apparatus and a bubble generating apparatus that can be directly used for carrying out the method. Background art

Conventionally, a membrane separation method using a filtration membrane is widely known as a method for selectively separating a specific substance from a liquid containing impurities. Such filtration membranes include microfiltration membranes with a pore size of approximately 10 m to 5 nm, ultrafiltration membranes with a pore size of 200 nm to 2 nm, and reverse osmosis membranes with a pore size of 2 nm or less. is there. As materials for these filtration membranes, acetic acid cell mouths and aromatic polyamides are generally used. Of these, the reverse osmosis membrane (RO membrane) is a membrane that has the property of allowing water to pass through impurities other than water, such as S ions and salts! /. From the seawater and brine to industrial, agricultural, It is widely used for desalination to obtain fresh water for drinking. Among reverse osmosis membranes, those with pore sizes of 1 to 2 nm and an ion or salt rejection of approximately 70% or less, especially those that are called nanofilters or NF membranes, are basically the same as reverse osmosis membranes. The same.

[0003] In a desalination treatment using a reverse osmosis membrane, the pressure of raw water (for example, seawater) and water that are in osmotic equilibrium across the reverse osmosis membrane is higher than the osmotic pressure of the raw water (referred to as "operation pressure"). )) From the raw water side, the water molecules in the raw water are transferred to the water side. The difference between the operating pressure and the osmotic pressure of the raw water is the “effective pressure”.

[0004] Salts that cannot permeate the reverse osmosis membrane stay in the vicinity of the membrane surface, and the salt concentration near the membrane surface increases. If this is retained as it is, the osmotic pressure on the raw water side will rise as much as possible and filtration will not be possible, so it will be necessary to continuously discharge water enriched in salts and impurities (referred to as “concentrated water”). is there. Therefore, the total amount of raw water cannot be filtered out by reverse osmosis.

[0005] In the reverse osmosis method, the higher the salt concentration of the raw water and the more the concentrated water is reduced, It is necessary to filter the water under high operating pressure. For example, from seawater with an average salt concentration of 3.5%, fresh water with a salt concentration of 0.01% that meets Japanese drinking water standards, with a water recovery rate of 40% (the remaining 60% is discarded as concentrated water). In order to obtain this, an operating pressure of about 5.5 to 6.5 MPa is required in recent technical levels!

[0006] In order to apply a high operating pressure to raw water, a large amount of energy is required to operate the high-pressure pump, and the cost of the obtained fresh water increases. In reality, it is said that in the desalination treatment of seawater by the reverse osmosis method, about half of the treatment cost is accounted for by the electricity charges for operating the high-pressure pump.

Therefore, for example, in Patent Documents 1 to 3, module units containing reverse osmosis membranes are provided in multiple stages and connected in series, and the concentrated water obtained from the previous reverse osmosis membrane module unit is further pressurized. Technologies have been proposed to reduce the operating energy and processing costs by supplying them to the reverse osmosis membrane module unit in the subsequent stage.

Patent Document 1: JP-A-9 276663

Patent Document 2: Japanese Unexamined Patent Publication No. 2000-051663

Patent Document 3: Japanese Patent Laid-Open No. 2001-252659

Disclosure of the invention

Problems to be solved by the invention

However, when the reverse osmosis membrane module units are arranged in multiple stages as described above, the entire processing apparatus inevitably becomes large and complicated. Even if the reverse osmosis membrane module unit is arranged in multiple stages, a larger operating pressure (about 7 to 9 MPa in the embodiment described in the above document) acts on the subsequent module unit. It is pointed out that the pressure-resistant burden and problems of reverse osmosis membrane module units cannot be solved sufficiently.

[0009] Therefore, the present invention provides a method in which a sufficient effective pressure acts on a reverse osmosis membrane and other filtration membranes to efficiently permeate water even when the operation pressure applied to the raw water side is lowered, The present invention provides a desalination treatment method capable of allowing more water to permeate under pressure, and a desalination treatment apparatus that can be used for carrying out the method, thereby further reducing the desalination treatment cost.

[0010] In addition, the present invention is directly used for the implementation of power, a method of desalinating treatment and a desalting treatment apparatus. The present invention provides an air bubble generating device.

Means for solving the problem

[0011] The inventors of the present invention have found that the filtration efficiency is remarkably improved by causing bubbles to act on the raw water side during the filtration and separation operation using a reverse osmosis membrane or the like.

[0012] That is, the desalination treatment method of the present invention (Claim 1) is characterized in that fine bubbles are generated in raw water containing salts, and the raw water containing the fine bubbles is separated by filtration membrane to obtain water. And According to this desalting method, the effective effective pressure can be increased only by generating fine bubbles in the raw water immediately before the separation of the filtration membrane. As a result, it is possible to obtain a fresh water recovery rate that is equal to or higher than that of the conventional method with a lower operating pressure than that of the conventional method, or a fresh water recovery rate that is higher than that of the conventional method with an operating pressure that is equal to that of the conventional method. As a result, significant economic effects such as saving operating energy and reducing the pressure-resistant load of the filtration membrane are achieved.

[0013] Further, the desalination treatment apparatus of the present invention (Claim 4) is supplied through the storage means, pressurization means, and supply means of raw water containing salts, etc., and the storage means, pressurization means, and supply means. It is characterized by comprising bubble generating means for generating fine bubbles in the raw water and separation means provided on the downstream side of the bubble generating means for separating the raw water containing the fine bubbles by filtration membrane. With this desalting apparatus, the above-described desalting method can be suitably implemented. This desalination apparatus is a conventional general filtration membrane separation apparatus equipped with raw water storage means, pressurization means, supply means, and separation means, and bubble generation means is added to the previous stage (upstream side) of the filtration membrane separation process. It can be configured simply by doing. Therefore, it can be implemented economically by effectively utilizing existing filtration membrane separation devices.

A reverse osmosis membrane (RO membrane or NF membrane) can be particularly preferably used as the filtration membrane in the desalination treatment method and desalination treatment apparatus invention (claims 2 and 5).

[0014] The fine bubbles preferably used in the invention of the desalting treatment method and desalting treatment apparatus are microbubbles having a diameter of several tens of meters or less, or nanobubbles having a smaller diameter (1 m or less) than the microbubbles. It is. If the diameter of the bubbles is several tens or less, they will rise in a short time and remain in the raw water for a long time without defoaming. The smaller the bubbles, the greater the effect of improving the filtration efficiency.

[0015] In the specific matter (claim 4) according to the desalination apparatus of the present invention, the "storage means of raw water" "For example, when the seawater is pumped directly from the ocean, which is a reservoir or reservoir, the ocean corresponds to the storage means." The “pressure unit” of the raw water is, for example, a pump for pressurizing the raw water, and the “supply unit” of the raw water is a supply pipe for connecting the storage unit and the pressurizing unit described above. . These storage means, pressurizing means, and supply means are equipment elements that are appropriately designed according to the scale of the processing equipment, the installation environment, and the like, and the specific configuration thereof is not particularly limited in the present invention.

[0016] The bubble generating means can be provided in any of the storing means, the pressurizing means, and the supply means as long as it is upstream of the separating means. However, the raw water containing fine bubbles generated by the bubble generating means needs to be supplied to the separation means before the fine bubbles disappear. In this sense, the microbubbles are contained without interposing other processing steps (for example, precipitation, aggregation, mixing of additives, heating, cooling, etc.) between the bubble generating means and the separating means. It is desirable that the bubble generating means and the separating means are simply directly connected by a pipe or the like so that the raw water can be directly sent to the separating means. If the above treatment process is interposed between the bubble generation means and the separation means, the fine bubbles in the raw water may disappear, and the effect of improving the filtration efficiency at the filtration membrane separation stage may be reduced. is there. However, for example, a rough filtration process using a filter with large pores or a floating separation process using large-sized air bubbles that are generated simultaneously with the generation of air bubbles can be performed while the fine bubbles in the raw water remain. For example, it may be interposed between the bubble generating means and the separating means.

[0017] From the viewpoint of preventing the disappearance of the fine bubbles generated in the raw water, rather than pressurizing the raw water after generating fine bubbles in the raw water, the raw water is previously pressurized in the raw water. It is preferable that fine bubbles are generated and the raw water is separated by filtration membrane at an operating pressure equivalent to or slightly lower than the pressurization condition (Claim 3). Therefore, when a pressurizing means such as a pump is provided on the path of the supply means, the bubble generating means is provided downstream of the pressurizing means, that is, between the pressurizing means and the separating means. Is more desirable (claims 6 and 7).

As a further configuration of the desalting apparatus of the present invention (Claim 8), the pressure energy of the concentrated water discharged from the separating means may be used for driving the bubble generating means. By effectively utilizing the high pressure of concentrated water in this way, the operating energy of the entire desalination treatment equipment Gee can be further saved.

As described above, the main part of the present invention is that fine bubbles are generated in the raw water before the filtration membrane separation. The fine bubbles are desirably generated under a pressure condition equal to or higher than the operation pressure at the time of filtration membrane separation. Examples of the bubble generation method include a generation method using a bench lily effect, a generation method using a swirl flow, a generation method using pressure dissolution, and the like. A bubble generation method that can support continuous operation of filtration and separation is preferable. Masle.

[0018] Therefore, the present invention employs the following technical configuration (claim 9) as a bubble generating device capable of continuously generating a certain amount of fine bubbles in a liquid in a pressurized state. .

That is, the bubble generating device of the present invention includes an aspirator interposed in a pipe line through which a pressurized liquid flows, and a pressure equalizing container connected to the aspirator, and the aspirator has a substantially cylindrical shape. None, one end in the axial direction is connected to the upstream side of the pipe, the other end is connected to the downstream side of the pipe, and a throttle is formed between the upstream half and the downstream half in the cylinder Thus, the pressure equalizing vessel has an air supply passage for supplying pressurized gas into the pressure equalizing vessel, and a liquid passage communicating with the upstream half of the aspirator, through the air supply passage. The gas supplied into the pressure vessel and the liquid flowing into the pressure equalization vessel through the liquid passage form a gas phase portion and a liquid phase portion in the pressure equalization vessel that have substantially the same pressure as the inside of the aspirator. The gas in the gas phase part passes through the air supply path connected to the aspirator. It is injected upstream of the throttle subordinates upstream end portion by, characterized in that to generate fine bubbles in the liquid in the Asupireta of.

[0020] Here, the aspirator is a device having a constricted portion in the flow path for creating a reduced pressure state by a bench lily effect using a fluid, and is used in combination with a swirling flow or a pressure dissolution method. Sometimes it is done. The pressure equalizing container in this bubble generating device is always in communication with the upstream half of the aspirator through the liquid passage, and is maintained at the same pressure as in the upstream half. When a gas is sealed in the pressure equalizing vessel, the gas and the liquid flowing into the pressure equalizing vessel create a pressure balance, and a gas phase portion and a liquid phase portion having substantially the same pressure are formed in the pressure equalizing vessel. . When the air in the gas phase part is communicated with the vicinity of the throttle part of the aspirator through the air supply passage, the gas is continuously supplied into the liquid by the bench lily effect produced by the liquid passing through the throttle part. That is, the present invention is configured such that the gas is self-supplied in the flow path by the flow of liquid rather than supplying the gas directly into the flow path of the pressurized liquid by a compressor or the like. Is. The hydraulic pressure in the flow path may fluctuate within a certain range depending on the operating condition of the pump, etc.In the method of supplying gas directly to the flow path with a compressor, etc., the gas pressure varies depending on the fluctuation of the hydraulic pressure. If the supply amount is not controlled, the amount of generated bubbles becomes unstable. In the desalination treatment method and apparatus according to the present invention, it is not preferable that the amount of generated bubbles becomes unstable because the generation state of bubbles affects the effective pressure of the filtration membrane separation. According to the bubble generating device, the upstream half of the aspirator and the pressure equalizing vessel communicate with each other through the liquid passage, so that the gas phase portion and the liquid phase portion in the pressure equalizing vessel are connected to the upstream half of the aspirator. The gas pressure is always maintained, while gas is supplied so that the gas phase is balanced with the aspirator pressure-reducing section upstream of the downstream end of the throttle section, so the fluid pressure in the flow path fluctuates. Even then, a certain amount of gas is always supplied into the liquid.

[0022] In the bubble generating apparatus according to the above configuration, the gas supply into the pressure equalizing vessel does not need to be continuously performed at a constant pressure. After supplying an appropriate amount of gas into the pressure equalization vessel, if the air supply passage is closed, the gas in the gas phase will be supplied into the aspirator through the air supply passage until there is no more gas trapped in the pressure equalization vessel. Continue to be. When the gas in the pressure equalization vessel decreases, the interface between the gas phase portion and the liquid phase portion rises. Therefore, the gas supply path is opened again at an appropriate timing, and the gas may be added to the pressure equalization vessel. Thus, if the gas is supplied intermittently, it is possible to save the operating energy of the pump for pressurizing the gas. Furthermore, if all or part of the pressure equalization container is made of a transparent material, it will be easier to visually check the air supply status.

[0023] Note that the amount of bubbles generated in the aspirator is mainly determined by the hydraulic pressure, flow velocity, cross-sectional shape in the vicinity of the throttle portion, etc. in the aspirator. It is also affected by the inner diameter and opening position of the air passage that communicates with each other. Therefore, in order to stably obtain a desired bubble generation state, for example, a function for adjusting the gas flow rate is provided in the middle of the air supply path, or the opening position of the air supply path in the aspirator can be moved. May be.

The invention's effect [0024] According to the desalination treatment method and the desalination treatment apparatus of the present invention configured as described above, even if the operation pressure acting on the raw water side is lowered by causing bubbles to act during the filtration and separation operation, Effectively high effective pressure can be obtained compared to the conventional method, or more water can be permeated with the same operating pressure, and membrane separation can be performed efficiently. Therefore, a high recovery rate can be obtained with less operating energy than in the past, and the entire processing apparatus can be easily reduced in size and simplified. Furthermore, the reduction of the operating pressure acting on the filtration membrane can greatly improve the problem of pressure resistance in the filtration membrane.

[0025] Further, according to the bubble generating device of the present invention, a certain amount of bubbles is continuously generated in a liquid such as salt water in a pressurized state with less energy without requiring a troublesome pressure adjustment operation. That power S. As a result, the desalting treatment method and the desalting treatment apparatus can be carried out efficiently.

Brief Description of Drawings

FIG. 1 is a schematic configuration diagram of a desalting apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a bubble generating device used in the desalting apparatus.

FIG. 3 is a schematic configuration diagram of a desalting apparatus according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a desalting apparatus according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a bubble generation device according to an embodiment of the present invention.

Explanation of symbols

[0027] 1 Reservoir (storage means)

2 Supply pipe (supply means)

3 High pressure pump (Pressurizing means)

4 Reverse osmosis membrane module unit (separation means)

8 Bubble generator (bubble generator)

100 Bubble generator

101 pipeline (upstream side)

102 pipeline (downstream)

110 Aspirator 113 Aperture

120 pressure equalization vessel

121 Air supply path

122 Liquid passage

123 Gas phase

124 Liquid phase

125 Airway

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0029] FIG. 1 shows a schematic configuration of a desalting apparatus according to a first embodiment of the present invention. In the storage tank 1, as raw water, for example, seawater or the like that has been subjected to appropriate pretreatment such as removal of impurities or sterilization is stored. The raw water is pressurized by the high pressure pump 3 through the supply pipe 2 connected to the storage tank 1 and sent to the reverse osmosis membrane module unit 4. In this embodiment, the storage tank 1 constitutes a storage means, the supply pipe 2 constitutes a supply means, the high-pressure pump 3 constitutes a pressurization means, and the reverse osmosis membrane module unit 4 constitutes a separation means. ! /

[0030] The reverse osmosis membrane module unit 4 is obtained by processing a reverse osmosis membrane having a known material strength such as cellulose acetate or polyamide into a known shape such as a flat spiral membrane or a hollow fiber membrane. The structure is not particularly limited in the present invention.

A supply pipe 2 is connected to the inlet side of the reverse osmosis membrane module unit 4. The outlet side of the reverse osmosis membrane module unit 4 is connected to a water collection pipe 5 for taking out desalted purified water and a discharge nozzle 6 for discharging concentrated water. The water collecting pipe 5 is connected to the purified water tank 7, and after that, the purified water is post-treated in a post process (not shown).

In the present embodiment, bubble generating means is provided in the storage means. The bubble generating means is constituted by a so-called “fill-in” bubble generating device 8 provided in the storage tank 1. The throw-in type bubble generating device mentioned here is a device that generates bubbles by throwing it into the current water. However, for example, it also includes a device that feeds only raw water into raw water and circulates and supplies raw water containing bubbles via an external pump. A configuration example of such a bubble generating device 8 is shown in FIG. Shown in

[0032] The main body 81 of the bubble generating device 8 has a long cylindrical shape, one end (the left end in the figure) is closed, and the other end (the right end in the figure) is opened. In the through hole 82 in the main body 81, the substantially half portion on the closed end side is an inflow portion 83 having a uniform cross section, and the substantially half portion on the open end side is enlarged in a taper shape toward the tip (right end in the figure). An outflow portion 84 is formed, and a narrow diameter constriction portion 85 is formed at the boundary between the inflow portion 83 and the outflow portion 84. An inlet pipe 86 connected to the pump is connected to the middle part of the main body 81 so as to be orthogonal to the longitudinal direction of the main body 81, and raw water is injected from the inlet pipe 86 into the inflow part 83.

[0033] In addition, an air supply pipe 87 protruding into the inflow portion 83 is provided on the closed end side, and air is injected into the inflow portion 83 from a professional tube (not shown). The pressure of the raw water injected into the inflow part 83 together with the air rapidly decreases by passing through the constriction part 85, and a shock wave is generated in the outflow part 84 on the downstream side of the constriction part 85. As a result, the air mixed in the raw water is refined into bubbles.

[0034] By circulating the raw water in the storage tank 1 through such a bubble generating device 8, fine bubbles are continuously generated in the raw water. The raw water is sent to the reverse osmosis membrane module unit 4 through the high-pressure pump 3 while containing fine bubbles, and desalting is performed. As the input type bubble generating device, in addition to the device having the structure as illustrated, for example, “Nano Bubble DBON (trademark)” manufactured by Tanano Techno Works Co., Ltd., or a bubble generator manufactured by Nikuni Co., Ltd. A well-known microbubble generator such as “Bavitas (trademark)” manufactured by Kyowa Kikai Co., Ltd. can be used.

FIG. 3 shows a schematic configuration of a desalting apparatus according to the second embodiment of the present invention. Components common to the first embodiment described above are denoted by common reference numerals, and detailed description thereof is omitted. Also in this embodiment, the storage tank 1 constitutes a storage means, the supply pipe 2 constitutes a supply means, the high-pressure pump 3 constitutes a pressurization means, and the reverse osmosis membrane module unit 4 constitutes a separation means. is doing.

In the present embodiment, the bubble generating device 8 constituting the bubble generating means is connected to the supply pipe.

It is provided in the middle of the two paths, more specifically, between the high pressure pump 3 and the reverse osmosis membrane module unit 4. The bubble generating device 8 according to this embodiment is a so-called “inline type”. It is. As an in-line type bubble generating apparatus that can be used for such a configuration, for example, OHR line mixer (static type mixer) manufactured by Seika Sangyo Co., Ltd., micro bubble generating nozzle manufactured by Aura Tech Co., Ltd. and the like are known. In addition, an appropriate water tank or container (not shown) is provided between the high-pressure pump 3 and the reverse osmosis membrane module unit 4, and the above-mentioned input type bubble generating device is installed in the water tank or container. It can also be implemented.

FIG. 4 shows a schematic configuration of a desalting apparatus according to the third embodiment of the present invention. The basic configuration of this embodiment is the same as that of the second embodiment described above. The storage tank 1 constitutes a storage means, the supply pipe 2 constitutes a supply means, and the high-pressure pump 3 constitutes a pressurization means. The reverse osmosis membrane module unit 4 constitutes the separation means! The bubble generating device 8 constituting the bubble generating means is provided between the high pressure pump 3 and the reverse osmosis membrane module unit 4.

[0036] In the present embodiment, the discharge pipe 6 connected to the outlet side of the reverse osmosis membrane module unit 4 is connected to the bubble generating device 8, and further connected from the bubble generating device 8 to the pressure recovery turbine 10. Has been. A part of the pressure energy of the concentrated water taken out through the discharge pipe 6 is used as a driving force for generating fine bubbles in the bubble generating device 8. Further, the remaining pressure energy is recovered by the pressure recovery turbine 10 and used to boost the raw water supplied through the supply pipe 2. In this way, the pressure energy of the discharged concentrated water can be used effectively.

FIG. 5 shows a configuration of a novel bubble generating apparatus 100 that can be suitably used in the desalting apparatus shown in the second embodiment or the third embodiment.

[0037] In FIG. 5, reference numerals 101 and 102 denote conduits through which raw water or other liquid containing salts flows in a pressurized state. The aspirator 110 is installed in the middle of the pipe lines 101 and 102.

Yes

[0038] The aspirator 110 is formed of a substantially cylindrical pressure vessel, and one end in the axial direction thereof is connected to the upstream pipe 101 and the other end is connected to the downstream pipe 102. ing. Inside the aspirator 110, in order from the upstream side to the downstream side, an upstream steady portion 111 having a uniform cross-sectional area substantially the same as the cross-sectional area of the container, and a tapered reduced portion in which the cross-sectional area decreases at a constant inclination. 112 and the reduced cross-sectional area is continuous over a certain dimension The constricted portion 113, the tapered enlarged portion 114 whose cross-sectional area increases at a constant inclination, and the downstream steady portion 115 having a uniform cross-sectional area substantially the same as the cross-sectional area of the container are coaxially continuous. It is formed so that. In the present invention, the upstream side, that is, the upstream steady portion 111 and the contracting portion 112, which are divided from the throttle portion 113 as a boundary, are collectively referred to as the upstream half, and the downstream side, that is, the expanding portion 114 and the downstream portion. The side stationary part 115 is collectively referred to as a downstream half part. However, the axial lengths of the upstream half and the downstream half are not necessarily the same.

A pressure equalizing vessel 120 is connected to the outside of the aspirator 110. The pressure equalizing container 120 in the illustrated embodiment is substantially cylindrical, and is attached so that the bottom of the container is in contact with the top of the aspirator 110 with its axial direction being substantially parallel to the axial direction of the aspirator 110.

[0040] An air supply path 121 is connected to the pressure equalizing vessel 120. Air or other gas pressurized by a pressure pump (not shown) or the like is supplied into the pressure equalizing vessel 120 through the air supply path 121. The air supply path 121 can be arbitrarily switched between a ventilation state and a closed state by operating an on-off valve (not shown) or the like.

[0041] In addition, a liquid passage 122 that connects the pressure equalizing vessel 120 and the upstream half of the aspirator 110 is provided so as to penetrate a portion where the pressure equalizing vessel 120 and the aspirator 110 are in contact with each other. The liquid passage 122 is always open, and the liquid in the upstream half of the aspirator 110 flows into the pressure equalizing vessel 120 through the liquid passage 122.

[0042] After an appropriate amount of gas has been supplied into the pressure equalizing vessel 120 through the air supply passage 121, when the air supply passage 121 is closed, the gas sealed in the pressure equalizing vessel 120 and the pressure equalized through the liquid passage 122 The liquid flowing into the container 120 creates a pressure balance, and a gas phase part 123 and a liquid phase part 124 having substantially the same pressure are formed in the pressure equalizing container 120.

[0043] The gas in the gas phase section 123 is introduced into the aspirator 110 through the air inlet path 125. One end of the air supply path 125 opens to the upper part of the pressure equalizing vessel 120 and faces the gas phase part 123, and the other end opens to a position near the upper end of the throttle 113 in the aspirator 110. When the liquid in the aspirator 110 passes through the throttle 113, a negative pressure is generated in the throttle 113 due to the bench-lily effect. Due to the negative pressure, the gas in the gas phase section 123 is drawn into the aspirator 110 through the air inlet path 125 and passes through the throttle section 113 to generate fine bubbles. [0044] In the bubble generating device 100, it is not necessary to continuously supply the gas into the pressure equalizing vessel 120 at a constant pressure. After supplying an appropriate amount of gas into the pressure equalizing vessel 120, if the air supply passage 121 is closed, the pressure balance between the gas phase portion 123 and the liquid phase portion 124 until the gas trapped in the pressure equalizing vessel 120 disappears. State is maintained. The gas in the gas phase section 123 is gradually supplied into the aspirator 110, and the interface between the gas phase section 123 and the liquid phase section 124 gradually rises. Therefore, the air supply path 121 is opened again at an appropriate timing. A gas may be added to the pressure equalizing vessel 120. Thus, by intermittently supplying the gas to the pressure equalizing vessel 120, it is possible to save the operating energy of the pump for pressurizing the gas. Moreover, even if the liquid pressure fluctuates within a range of, for example, several percent, it is sufficient to maintain a constant supply pressure that does not require frequent adjustment of the gas supply pressure.

Note that the above-described embodiment is an example, and the present invention can be implemented by slightly changing the form within a range where the effects produced in the fluid are equivalent. For example, the pressure equalizing vessel 120 may not be directly attached to the aspirator 110, but the pressure equalizing vessel 120 may be arranged separately from the aspirator 110, and the liquid passage 122 and the air intake passage 125 may be extended and connected. . In addition, the air supply passage 125 may be connected to the aspirator 110 after being drawn out of the pressure equalizing vessel 120 without passing through the liquid phase portion 124 as in the exemplary embodiment.

[0046] The amount of bubbles generated in the aspirator 110 and the particle size of the generated bubbles are determined not only by the hydraulic pressure and flow velocity in the aspirator 110, the cross-sectional shape in the vicinity of the throttle 113, but also the inner diameter of the air inlet passage 125. It is defined by the opening position etc. in the vibrator. These plural types of design elements may be selectively determined as appropriate according to the required amount of bubbles generated and the particle size. The opening position of the air injection path 125 into the aspirator 110 may be within the range from the vicinity of the reduction part 112 to the downstream end of the throttle part 113 (the boundary between the throttle part 113 and the enlarged part 114). However, the opening position may be moved along the axial direction of the aspirator 110, or a function of adjusting the gas flow rate may be provided in the air supply passage 125.

Example

[0047] An example of the desalting apparatus of the above embodiment will be described below.

[0048] [Example 1]

As Example 1, it was carried out by the desalting apparatus which applied the power to the configuration of the first embodiment (FIG. 1). . As raw water, salt water adjusted to a salt concentration of 0.1% by adding salt to distilled water was used. A bubble generator 8 as shown in Fig. 2 is put into the storage tank 1, and about 1L of air is sent to 20L (liter) of raw water every minute for 5 minutes while continuing to circulate the raw water. Bubbles were generated.

Then, the raw water was pressurized to 0.2 MPa with the high-pressure pump 3 and supplied to the reverse osmosis membrane module unit 4. For the reverse osmosis membrane module unit 4, one low pressure spiral RO element “NTR-759HR” manufactured by Nitto Denko Corporation was used. Purified water with a salt concentration of 0.01% or less could be obtained through the operation of this desalination treatment equipment. The treatment amount per membrane area at this time was 8 L / hr'm ² .

[0050] [Comparative Example 1]

Further, as Comparative Example 1, in the same apparatus configuration as in Example 1 above, the bubble generating device 8 was not operated at all, and the raw water containing no fine bubbles was subjected to desalting treatment at the same operating pressure of 0.2 MPa. It was. As a result, it was possible to obtain purified water having a salt concentration of 0.01% or less. The treatment amount per membrane area at this time was 5 L / hr'm ² .

[Example 2]

Example 2 was carried out by a desalting apparatus that applied power to the configuration of the second embodiment (FIG. 3). The raw water used was salt water adjusted to a salt concentration of 3.5% by adding salt to distilled water. The above raw water is pressurized to 3.2 MPa with a high-pressure pump and connected to the bubble generating device 8, and approximately 1 L of air is sent to 10 L of raw water per minute under the caloric pressure condition to generate fine bubbles in the raw water. Made.

[0051] Then, the raw water was supplied to the reverse osmosis membrane module unit 4 while maintaining the pressure of 2 MPa. The reverse osmosis membrane module unit 4 uses one low pressure spiral RO element “NTR-759HR” manufactured by Nitto Denko Corporation. Purified water with a salt concentration of 0.1% or less could be obtained through the operation of this desalting apparatus. Throughput per membrane area in this case the thickness is 25L hr'm ^2.

[0052] [Comparative Example 2]

As Comparative Example 2 with respect to Example 2 above, in the same apparatus configuration as in Example 2 above, the bubble generating device 8 was not operated at all, and the same 3.2 MPa operation was performed on raw water containing no fine bubbles. Desalination treatment was performed under pressure. However, the raw water did not pass through the reverse osmosis membrane module unit 4 and purified water could not be obtained.

[Example 3]

Example 3 was carried out with a desalting apparatus that was effective in the configuration of the second embodiment (FIG. 3). As raw water, salt water adjusted to a salt concentration of 0.1% by adding salt to distilled water was used. The above raw water is pressurized to IMPa with a high-pressure pump and connected to the bubble generating device 8, and about 1L of air is sent to 10L of raw water per minute under pressurized conditions to generate fine bubbles in the raw water. It was.

[0053] Then, the raw water was supplied to the reverse osmosis membrane module unit 4 while maintaining the pressure of IMPa. The reverse osmosis membrane module unit 4 used a single low-pressure spiral RO element “NTR-759HR” manufactured by Nitto Denko Corporation. By operating the desalting apparatus, purified water having a salt concentration of 0.01% or less could be obtained. The throughput per membrane area at this time was 60 L hr'm.

[0054] [Comparative Example 3]

As Comparative Example 3 with respect to Example 3 above, in the same apparatus configuration as in Example 3 above, the bubble generating device 8 was not operated at all, and the raw water containing no fine bubbles was subjected to desalting treatment at the same operating pressure of IMPa. went. The raw water had a force S that passed through the reverse osmosis membrane module unit 4, and the treatment amount per membrane area at this time was 35 L / hr'm ² .

From the above examples and comparative examples, it was confirmed that the desalination treatment method and the desalination treatment apparatus of the present invention reliably improve the treatment efficiency in the reverse osmosis membrane treatment.

Industrial applicability

[0055] The desalination treatment method and desalination treatment apparatus of the present invention remove seawater desalination, impurities other than water from natural water such as lake water, river water, rainwater, and mixed solutions of various inorganic salts. Thus, it can be widely used in technologies for obtaining fresh water for industrial use, agricultural use, drinking and the like.

[0056] Further, the bubble generating apparatus of the present invention can be suitably used for the implementation of the desalinating treatment method and desalinating apparatus as described above, as well as general water purification, breeding of aquatic organisms, health It can also be widely used in the manufacture of health drinks and health appliances that use air bubbles.

Claims

The scope of the claims

[1] A desalting treatment method characterized in that fine bubbles are generated in raw water containing salts, and the raw water containing fine bubbles is separated by a filtration membrane to obtain water.

[2] The desalting method according to claim 1, wherein the filtration membrane is a reverse osmosis membrane.

[3] In the desalination treatment method according to claim 1 or 2, fine bubbles are generated in the raw water in a state where the raw water is pressurized, and the raw water is filtered through an operation pressure equal to or lower than the pressure condition. A desalting method characterized by separating.

[4] Raw water storage means including salt, pressurization means, and supply means;

Bubble generating means for generating fine bubbles in the raw water supplied through the storage means, pressurizing means, and supply means;

A demineralization processing apparatus, comprising: a separation unit that is provided downstream of the bubble generation unit and separates the raw water containing the fine bubbles through a filtration membrane.

[5] The desalinating apparatus according to claim 4, wherein the filtration membrane of the separating means is a reverse osmosis membrane.

6. The desalinating apparatus according to claim 4, wherein the bubble generating means is provided between the pressurizing means and the separating means.

7. The desalinating apparatus according to claim 5, wherein the bubble generating means is provided between the pressurizing means and the separating means.

[8] The desalinating apparatus according to any one of claims 4 to 7, wherein the pressure energy of the concentrated water discharged from the separating means is used for driving the bubble generating means. .

[9] An aspirator interposed in a conduit through which pressurized liquid flows, and a pressure equalizing vessel connected to the aspirator,

The aspirator has a substantially cylindrical shape, and one end in the axial direction is connected to the upstream side of the pipe, and the other end is connected to the downstream side of the pipe, and the upstream half and the downstream half of the pipe are connected to each other. A constricted part is formed between them,

The pressure equalization container includes an air supply path for supplying pressurized gas into the pressure equalization container, and the above-mentioned aspirator. A gas passage communicating with the upstream half of the gas, and the gas supplied into the pressure vessel through the air supply passage and the liquid flowing into the pressure equalization vessel through the liquid passage are stored in the pressure equalization vessel. The gas phase portion and the liquid phase portion are formed at substantially the same pressure as the inside of the vibrator, and the gas in the gas phase portion is more than the downstream end portion of the throttle portion in the aspirator through the air supply path connected to the aspirator. A bubble generating device characterized by generating fine bubbles in a liquid in an aspirator by being injected upstream.