JPH06277655A - Concentration of solution and seawater desalting system - Google Patents

Abstract

PURPOSE:To facilitate solid-liquid separation and continuous treatment in desalting seawater by utilizing freeze concn. CONSTITUTION:Seawater (raw water) is cooled to low temp. by first and second heat exchangers 2, 4 to be introduced into a supercooler 7. The supercooled seawater emitted from the supercooler 7 impinges against a belt conveyor 24 to precipitate ice and conc. seawater falls in a water tank as it is. Precipitated ice is melted by sprinkling water heated by the first heat exchanger 2 to ice by a sprinkling device 27 to obtain fresh water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for concentrating various solutions such as seawater by utilizing freeze concentration, and a desalination system for seawater utilizing such freeze concentration.

[0002]

2. Description of the Related Art There have been many proposals for a so-called freeze concentration method in which a part of a solution is frozen and only a pure ice part is separated to concentrate the solution. The reality is that the development and spread of the device is delayed compared to the law. The cause is that there is a problem in the enlargement of the equipment and the enormous amount of energy required for the treatment, which are seen in the conventional freeze concentration technology.

The conventional freeze concentration method is roughly classified into three methods, that is, a centrifugation method, a washing tower method, and a pressure method. First, in the centrifugal separation method, a sherbet-like slurry composed of ice crystals and a concentrated liquid obtained by partially freezing the solution is subjected to a solid-liquid separation by applying a centrifugal separator.
The washing tower method is a method in which aged large-sized ice particles are washed in a tower-like moving bed while being slowly exchanged with a washing liquid to reduce the solute concentration in ice crystals. The last pressure method is
The ice slurry is pressurized, and the melted concentrated liquid portion is discharged to the outside of the system through a mesh or the like to perform a solid: liquid separation operation.

[0004]

However, in the above method, the size of the entire apparatus, especially the separation apparatus for carrying out solid: liquid separation, becomes large, and there is a practical problem. Moreover, all of the above-mentioned conventional methods require a large amount of energy and are costly, and from this point also, the freeze-concentrating method of the above-mentioned conventional methods has not been popular.

The present invention has been made in view of such a point, and basically uses the principle of freeze concentration, and further, a solid-liquid separation process is easy, and a continuous process is possible, and It is intended to provide a seawater desalination system to solve the above problems.

[0006]

In order to achieve the above object, first, in claim 1, the solution to be concentrated is supplied to the supercooling means, and the solution in the supercooled state discharged from the supercooling means is supplied. A method for concentrating a solution, characterized by colliding with an appropriate supercooling releasing means to release the supercooled state, separating ice from the ice / water slurry generated thereby, and concentrating the solution. To do.

Examples of the supercooling means here include, for example, JP-A-63-217171, JP-A-63-231157, and JP-A-1-11 disclosed by the present applicant.
The supercooler etc. which generate | occur | produce a supercooled water continuously described in 4682 gazette etc. are mentioned.

Further, in claim 2, supercooling means for supercooling the seawater, supercooling releasing means for releasing the supercooled state of the supercooled seawater discharged from the supercooling means, and supercooling releasing means Seawater, characterized by comprising a separating means for separating ice from the ice / water slurry carried, a carrying means for carrying the ice separated by the separating means to another place, and a melting means for melting the carried ice. To provide a desalination system.

Furthermore, in the seawater desalination system according to claim 2, there is provided a seawater desalination system further comprising an RO reverse osmosis seawater desalination apparatus for treating water when the ice is melted by the melting means as treated water. Provided as claim 3.

Further, in claim 4, supercooling means for supercooling the seawater, a belt conveyor arranged in a drop path of the supercooled seawater discharged from the supercooling means, and a belt conveyor are located below the conveyor path. Water tank, consisting of water sprinkling means for sprinkling water taken from the water tank toward the belt conveyor, the belt conveyor with a large number of water permeation holes, the water taken from the water tank before water sprinkling from the water sprinkling means Provided is a desalination system for seawater, comprising a heat exchange means for exchanging heat with seawater. The water-permeable hole mentioned here is an appropriate through-hole that traps ice and allows only water to pass through in the ice / water slurry produced when the supercooled state is released.

In the above desalination system of seawater, for example, as described in claim 5, the cooling heat source of the subcooler is:
It may be configured as cold heat by vaporization of LNG (Liquid Natural Gas).

Further, in the above case, as described in claim 6, it may be configured as a seawater desalination system to which an RO reverse osmosis seawater desalination apparatus for treating the water in the water tank as treated water is added. .

[0013]

According to the present invention, since the supercooling means produces a slurry of ice and concentrated water, solid-liquid separation is easy, and the process is an open system. The target solution to be concentrated can be efficiently and continuously concentrated under the principle of freeze concentration.

According to claim 2, since it is basically a desalination system of seawater utilizing freeze concentration found in the above-mentioned concentration method, solid-liquid separation between ice and concentrated water can be performed similarly to the above. It is easy and can continuously and efficiently desalize seawater. Further, as the separation means used in this case, a simple means such as a wire net or a punching metal for trapping or capturing only ice can be used.

According to the third aspect, since the RO reverse osmosis seawater desalination apparatus is further provided, the grade of the fresh water produced by that amount becomes very high. In addition, as mentioned above
O Since the fresh water introduced into the reverse osmosis seawater desalination plant is efficiently and continuously produced, the treatment capacity of the entire desalination system is also improved.

According to the present invention, the belt conveyor serves both as the supercooling releasing means and the conveying device, so that the system can be simplified and the melting process can be carried out during the conveying.
Further, melting of the deposited ice is performed by sprinkling water from the sprinkling means, but the water in the water tank used for this melting is fresh water produced by melting the ice and is heated by heat exchange with seawater. Therefore, it is not necessary to separately secure the heat energy used for melting. Moreover, by supplying the seawater, whose temperature has been lowered by the heat exchange, as raw water to the subcooler, the burden on the subcooler is reduced,
It is possible to build an extremely efficient system that matches energy conservation.

In the present invention, the cold heat source of the supercooling means is LN.
Since the cold heat is generated by G vaporization, for example, LNG vaporization latent heat discarded from an LNG base that produces city gas from LNG can be effectively used.

According to the sixth aspect, since the RO reverse osmosis seawater desalination apparatus for treating the water in the water tank as the treated water is provided, the grade of fresh water stored in the water tank after the desalination treatment is further increased. Can be increased. Further, as described above, since the fresh water introduced into the RO reverse osmosis seawater desalination apparatus is efficiently and continuously produced, the desalination system as a whole has a high treatment capacity.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a system flow of this embodiment. Seawater (raw water) taken by a pump 1 is first subjected to a first heat exchange. The second heat exchanger 4 through the flow path 3 via the vessel 2
Configured to be transferred to. The seawater (raw water) that has passed through the second heat exchanger 4 is directly supplied to the subcooler 7 through the flow path 6.

The subcooler 7 has a so-called shell-and-tube type heat exchanger in which a plurality of tubes (heat transfer tubes) 8 are axially arranged in a cylindrical shell, and one end of each of the tubes 8 is It is opened in the inlet header portion 9 of the subcooler 7, and the other end is opened in the atmosphere. Frozen brine flows through the shell, and the liquid (seawater in this embodiment) that flows through the tube 8 is supercooled by heat exchange with the frozen brine.

In this embodiment, the frozen brine is
LNG that produces city gas and combustion gas for power generation from LNG
The refrigeration source is the latent heat of vaporization of LNG, which is discarded in large quantities at the base. That is, LNG supplied from the LNG storage tank 11 installed underground is generally -150.
Although the temperature is low at about ° C, it is once heat-exchanged with the primary brine such as Freon 22 by the LNG / CFC heat exchanger 12 to raise the temperature to, for example, -25 ° C.
After that, the heater 13 further raises the temperature to a desired temperature, for example, 0 ° C., and then the odor processing is performed.

In this embodiment, the primary brine (for example, -6) that has been heat-exchanged by the LNG / CFC heat exchanger 12 is used.
0 ° C.) is further heat-exchanged with the secondary brine by the Freon / brine heat exchanger 14, and the secondary brine is heated to a temperature suitable for the frozen brine of the subcooler 7, for example, −
The temperature is raised to 15 ° C. and the secondary brine is supplied into the shell of the subcooler 7. The temperature of the frozen brine at that time is adjusted by a thermo controller 16 attached to a valve 15 that controls the flow rate of the secondary brine.

The subcooler 7 is connected to the A
The independent two-tank type water tank 22 having the tank and the B tank adjacent to each other is installed in the vicinity of the upper side of the A tank side, and the atmosphere side opening end of the tube 8 serving as a discharge port is horizontally located above the A tank. The supercooled liquid (seawater) that is directed and drops from the discharge port is designed to drop into the A tank.

In the space above the water tank 22, a belt conveyor 24 is installed so as to extend over the A tank and the B tank and pass through the transfer port 23 provided in the partition wall 21, as described above. The liquid in the supercooled state discharged from the subcooler 7 and falling into the tank A is in the tank A in the belt conveyor 24.
Are arranged to collide with. Therefore, the liquid in the supercooled state is released from the supercooled state by the impact when it collides with the belt conveyor 24, and as a result, fine ice is deposited on the belt conveyor 24. The belt conveyor 24 is provided with a large number of water permeation holes for trapping only the ice thus deposited and dropping the remaining water (concentrated seawater) as it is into the tank A.

The concentrated seawater that has fallen off from the belt conveyor 24 or passed through the water permeation holes and accumulated in the tank A is transferred to the second heat exchanger 4 described above by the water intake pump 25, and then part of it. Is sent from the flow path 6 to the subcooler 7 through the flow path 5, and the remaining part is drained through the flow path 26. The second heat exchanger 4 also serves to recover cold heat from the concentrated seawater and to heat the ice nuclei that cause freezing in the subcooler 7 to heat.

Above the water tank 22, there is provided a water sprinkler 27 which extends to the vicinity of the transfer port 23 in the tank B and the tank A and is located above the belt conveyor 24. The water sprinkler 27 has a water intake pump 28. B taken by
Part of the water in the tank is supplied through the first heat exchanger 2 described above. Further, the remaining water in the tank B taken by the water intake pump 28 passes through the flow path 2 as it is and is used for the subsequent use.

The seawater desalination system according to this embodiment is constructed as described above. Next, the desalination process will be described.
The seawater (raw water) at 0 ° C passes through the first heat exchanger 2 by the pump 1 and is, for example, 5 ° C when the ice described later is melted.
The temperature is lowered to 8 ° C by heat exchange with fresh water in
After that, it is transferred to the second heat exchanger 4.

In the second heat exchanger 4, heat exchange is performed with the 0 ° C concentrated seawater of the ice / water slurry produced when the later-described supercooled state is released, and the water temperature is further increased. Can be lowered to 2 ° C. A part of the seawater (raw water) whose temperature has been lowered in this way is discharged as it is through the flow path 5, but the remaining part is supplied to the inlet header section 9 of the subcooler 7 through the flow path 6. It

The subcooler 7 is supplied with frozen brine using the cold waste heat from the LNG base described above, and the seawater (raw water) supplied to the inlet header section 9 by heat exchange with this frozen brine is In a supercooled state of −7 ° C. to −10 ° C., the liquid is discharged from the discharge port and directly drops into the tank A of the water tank 22.

However, during the fall, the belt conveyor 2
4 is located, the seawater in the supercooled state collides with this belt conveyor 24, the supercooled state of the seawater is released by the impact, and fine ice particles are transferred to the belt conveyor 24.
Deposit on top. At this time, the remaining 0 ° C. seawater, which is concentrated as a result of the ice precipitation, drops into the tank A of the water tank 22 through the permeation hole in the belt conveyor 24 as it is, and is then taken by the water intake pump 25. Second statement
It is sent to the heat exchanger 4 and subjected to heat exchange with the 20 ° C. seawater (raw water) transferred by the pump 1, and then discharged through the flow path 26.

On the other hand, the ice deposited on the belt conveyor 24 passes through the carrying port 23 and is carried as it is to the B tank side of the water tank 22. At this time, the water that had been in the tank B in advance was taken by the intake pump 28, and the water was further removed by the second heat exchanger 2.
Heat is exchanged with seawater (raw water) at 0 ° C, the temperature is raised to, for example, 17 ° C, and water is sprinkled on the ice on the belt conveyor 24 by the water sprinkling device 27 installed at the upper part of the tank, so the ice melts. Then, it becomes fresh water at about 5 ° C and falls into the B tank. Further, since the water is always sprayed on the belt conveyor 24, the deposited ice does not freeze and adhere to the belt conveyor 24. Then, the ice remaining on the belt conveyor 24 without being melted also falls into the tank B when the belt conveyor 24 is turned upside down and is completely melted by the fresh water accumulated in the tank.

The fresh water produced by melting the ice as described above is taken by the intake pump 28, and a part of it is subjected to heat exchange with seawater (raw water) in the first heat exchanger 2 as described above. Then, the temperature is raised to 17 ° C. and then supplied to the water sprinkler 27, and the remaining part is used as it is after passing through the flow path 29.

As can be seen from the above process, although the desalination system is a desalination system utilizing the freezing phenomenon, it is an open process by a transient flow and continuously desalinates seawater. Is possible. Therefore, it is possible to perform a large amount of processing extremely efficiently.

For example, when operating at the above temperature setting, the intake of seawater (raw water) is 51 m ³ / min, the subcooler 7 has a subcooling degree of -2 ° C and an ice production rate of 0.025. In the above embodiment, 7 m ³ , 1
It is possible to produce about 10,000 m ³ of fresh water per day.

Moreover, the solid: liquid separation can be realized by a simple belt conveyor system as in the above embodiment. In the above embodiment, one device, that is, the belt conveyor 24, serves as both the supercooling releasing means and the conveying means, so that the apparatus is made compact and the system is greatly simplified.
Alternatively, of course, each function may be assigned to another independent device.

Even in that case, for example, the supercooling releasing means is constructed as an appropriate impact plate or a vertical pipe, and the ice / water slurry generated by them is once dropped into the water tank A as it is, and thereafter it is raised above the water surface by buoyancy. It is possible to perform solid-liquid separation easily by scraping off only the ice with a scraping device using a material such as a wire mesh or punching metal. Then, after that, the ice thus separated may be transferred to another place to be melted. In any case, conventional freeze concentration /
Solid-liquid separation, which was a process in which many problems were involved in the purification method and the device configuration was difficult, can be performed very easily.

In the above embodiment, seawater (raw water) having a relatively high temperature (20 ° C.) is sent to the first heat exchanger 2,
Because it exchanges heat with the water in tank B used for melting the ice,
The ice can be melted without waste and by effectively utilizing the sensible heat of seawater.

Further, the seawater (raw water) whose temperature has dropped to some extent by the heat exchange in the first heat exchanger 2 described above is heated by the second heat exchanger 4 and the seawater in tank A, which is now 0 ° C. Since it will be replaced, at the time of introduction into the subcooler 7,
Since the temperature is considerably low (2 ° C. in the above embodiment), the load on the subcooler 7 is reduced.

Moreover, the water thus taken from the tank A is once heat-exchanged with the seawater (raw water) by the second heat exchanger 4 to be heated, so that, for example, the ice dropped in the tank A remains unchanged. Even if it flows into the intake water, the ice is melted by the heat exchange in the second heat exchanger 4. Therefore, when water in the tank A is taken in, adverse effects such as blockage of the pipeline due to ice nuclei are prevented. That is, the 21st heat exchanger 4 also functions as an ice nucleus erasing device. As described above, the thermal energy required in each treatment process is used extremely efficiently, and the energy required for the entire system can be considerably smaller than the energy required for the conventional freeze concentration system.

In the above embodiment, the sprinkler device 27 is used.
Since the water sprinkling is also performed in the vicinity of the transfer port 23 of the partition wall 21 in the tank A, the concentrated seawater that remains on the belt conveyor 24 can be washed away, and the seawater is mixed with the fresh water generated by melting the ice. Is prevented.

In addition, in the above embodiment, the subcooler 7
The frozen brine, which serves as the cold heat source, is produced by the cold heat that was conventionally discarded in the sea from the LNG base, so that the cold waste heat can be effectively used and the system is extremely energy-saving.

In the above embodiment, for example, if the water in the B tank is supplied to the RO reverse osmosis desalination apparatus as it is, it is possible to produce highly purified fresh water extremely efficiently.

Further, in order to raise the grade of fresh water itself (decrease the salinity concentration) without using any other type of desalination apparatus, for example, the water tank is further increased, and the water in tank B is used as raw water. The same process as above may be repeated.

When the system is constructed as described above, and the seawater (attenuation) in the above embodiment is regarded as a solution to be concentrated and is configured as a system for concentrating the solution, the sprinkler 27 is used for the A tank side. In addition to stopping the water sprinkling in step A, if a suitable ice nucleus trapping fence or the like is provided so that the precipitated ice does not fall from the belt conveyor 24 into the tank A, the solution can be efficiently concentrated in the tank A. The water can be stored by the water intake pump 25 and can be taken in by the water intake pump 25. In this case, in order to increase the concentration grade, the water in tank A may be further used as raw water and the same treatment as in the above flow may be repeated.

[0045]

According to the first aspect of the present invention, since the subcooler means produces a slurry of ice and concentrated water, solid-liquid separation is easy, and the process is an open system process. Therefore, the target solution can be efficiently and continuously concentrated.

According to claim 2, like the above-mentioned claim 1,
Solidification of ice and concentrated water: easy liquid separation and efficient continuous desalination of seawater. Further, a simple separating means can be used, and as a result, the entire system can be simplified and made compact.

According to the third aspect, the grade of fresh water produced is very high, and the desalination process can be performed with high efficiency as the whole system.

In the fourth aspect, it is not necessary to separately provide the supercooling releasing means and the conveying device, and the system can be simplified, and accordingly, the whole can be made compact. Further, since the melting treatment can be carried out during transportation, efficient melting treatment is possible. Moreover, the water used for this melting is fresh water produced by melting ice,
Moreover, since the one whose temperature is raised by heat exchange with seawater (raw water) is used, no separate heat energy is required for melting.

In claim 5, the LNG vaporization latent heat discarded from the LNG base that produces city gas from LNG can be effectively used, and the above-mentioned claim 3,
It is possible to implement the invention of No. 4.

According to the sixth aspect, desalination having a higher grade than that of the fourth and fifth aspects can be realized, and the treatment capacity as a whole is high.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a system flow of a seawater desalination system according to an embodiment of the present invention.

[Explanation of symbols]

 2 First heat exchanger 4 Second heat exchanger 7 Supercooler 11 LNG storage tank 12 LNG / CFC heat exchanger 14 CFC / brine heat exchanger 22 Water tank 24 Belt conveyor 25 Water intake pump 27 Water sprinkler 28 Water intake pump A A A Tank BB Tank

Claims (6)

[Claims] 1. A solution is supplied to a subcooler, and the supercooled solution discharged from the subcooler is caused to collide with an appropriate supercooling releasing means to cancel the supercooled state. A method for concentrating a solution, which comprises isolating ice from an ice / water slurry and concentrating the solution. 2. Supercooling means for bringing the seawater into a supercooled state, supercooling release means for releasing the supercooled state of the supercooled seawater discharged from the supercooling means, and ice generated by the supercooling releasing means. A separation means for separating ice from the water slurry,
A desalination system for seawater, comprising a transporting means for transporting the ice separated by the separating means to another place, and a melting means for melting the transported ice. 3. The seawater desalination system according to claim 2, further comprising an RO reverse osmosis seawater desalination apparatus that treats water when ice is melted by the melting means as treated water. 4. A supercooling means for supercooling seawater, a belt conveyor arranged in a drop path of supercooled seawater discharged from the supercooling means, a water tank located below a conveying path of the belt conveyor, and the water tank. Consisting of water sprinkling means for sprinkling water taken from the belt conveyor, the belt conveyor with a large number of water permeation holes, the water taken from the water tank before water sprinkling from the water sprinkling means,
A desalination system for seawater, comprising a heat exchange means for exchanging heat with seawater. 5. The cold heat source of the supercooling means is cold heat by LNG vaporization, as claimed in claim 2, 3 or 4.
The seawater desalination system described in. 6. An RO for treating water in a water tank as treated water
Characterized by having a reverse osmosis seawater desalination device,
The desalination system of seawater according to claim 4 or 5.