JPH11216459A - Seawater desalting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly efficient seawater desalting device by which the quality of the fresh water obtained is improved, the power consumption is reduced with respect to the amt. of the generated water, and energy is saved. SOLUTION: This device has the vacuum evaporator 2 having a seawater inlet 7 and a seawater outlet 10 and evaporating the introduced seawater under vacuum, a vacuum pump 28 for reducing ther pressure below the saturated vapor pressure of seawater, a condenser 19 for cooling and condensing the produced steam to produce fresh water, a means 3 for continuously supplying seawater to the evaporator 19 in excess of the amt. of the water evaporated, a means 4 for discharging the seawater from the evaporator 2 in less than the supply and a means 5 for adjusting the flow rate of the seawater supply means 3 and that of the seawater discharge means 4 and keeping the seawater level in the evaporator 2 constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for obtaining freshwater from seawater, and more particularly to an improvement of a seawater desalination apparatus for obtaining freshwater for use as industrial water, drinking water and domestic water by a decompression method. Things.

[0002]

2. Description of the Related Art Conventionally, for example, a reverse osmosis membrane method is known as a seawater desalination technique for obtaining freshwater from seawater. In this reverse osmosis membrane (RO membrane) method, seawater is passed under high pressure through a reverse osmosis membrane, which is a polymer membrane, leaving seawater of a concentrated salt solution on the high pressure side, and fresh water as desalinated water on the low pressure side. Separate to produce fresh water.

However, in this reverse osmosis membrane method, since seawater is pressurized by a high-pressure pump and filtered by the reverse osmosis membrane, impurities are easily clogged in the reverse osmosis membrane, and it is necessary to perform reverse washing of the reverse osmosis membrane. In addition, when the operation is stopped, bacteria are generated, and a hole is formed in the reverse osmosis membrane, so that there is a problem that operation and maintenance are difficult.

[0004] On the other hand, there is known a decompression method in which seawater is put into a reduced-pressure evaporator and depressurized by a vacuum pump to take out steam from the seawater, and the taken-out steam is cooled and condensed by a condenser to obtain fresh water. . In this decompression method, there is no trouble such as back washing and no problem such as generation of bacteria.

[0005]

However, in the conventional seawater desalination apparatus employing the above-mentioned decompression method, the evaporating action is performed while only supplying seawater into the decompression evaporator. The seawater stored therein was gradually cooled by the latent heat of evaporation, whereby the saturated steam pressure also gradually decreased, and the load on the vacuum pump tended to increase. To prevent this, measures such as installing an electric heater to heat the inside of the decompression evaporator have been taken. However, a large amount of power is consumed, resulting in poor water production efficiency. was there.

[0006] Usually, a water supply pump is installed as a means for supplying seawater to the decompression vessel, and power is also consumed for driving the pump. This also causes a reduction in fresh water production efficiency. I have.

[0007] Further, in the conventional configuration, there is also a problem that salt water flows into the condenser side due to bumping of seawater in the reduced-pressure evaporator.

The present invention has been made in order to solve such a problem. In a seawater desalination apparatus using a decompression method, power consumption is saved to save energy and improve fresh water production efficiency, and salt water is used. The purpose of the present invention is to improve the quality of fresh water by preventing the flow of water into the condenser.

[0009]

According to the first aspect of the present invention,
A closed tank type, having a seawater inlet and a seawater outlet at the bottom side, and a reduced-pressure evaporator for evaporating the introduced seawater by reducing pressure, and a vacuum for reducing the pressure inside the reduced-pressure evaporator to below the saturated vapor pressure of seawater. A pump, a condenser for cooling and condensing water vapor obtained by the reduced-pressure evaporator to obtain fresh water, and seawater supply means for continuously supplying seawater having an amount equal to or greater than the amount of evaporated water to the reduced-pressure evaporator via the seawater inlet. A seawater discharging means for continuously discharging seawater of a supply amount or less from the reduced-pressure evaporator through the seawater discharge port, and adjusting a seawater flow rate of the seawater supplying means and the seawater discharging means to reduce the reduced-pressure evaporation. Control means for controlling the level of seawater in the vessel to be constant.

According to the present invention, the seawater supply means and the seawater discharge means are provided, and the amount of the seawater is adjusted by supplying more seawater than the amount of the evaporative water. , And water vapor can be taken out at a relatively low degree of vacuum. In addition, since the degree of vacuum is low, the load on the vacuum pump is reduced, the vacuum pump can be made smaller, and power consumption can be reduced.

Further, according to the present invention, by providing a control means for detecting and controlling the level of seawater in the reduced-pressure evaporator, the volume occupied by the steam in the reduced-pressure evaporator can be kept constant. It is possible to prevent a change in the degree of vacuum and stabilize the operation.

According to a second aspect of the present invention, in the seawater desalination apparatus according to the first aspect, the seawater supply means includes a seawater supply pipe having one end inserted into the seawater and the other end connected to the bottom of the vacuum evaporator. A seawater supply control valve provided in the seawater supply pipe to control the supply amount of seawater, and the pressure in the reduced-pressure evaporator is reduced to the atmospheric pressure or less, and the pressure difference suctions seawater into the reduced-pressure evaporator. And a pressure reducing mechanism.

According to the present invention, in order to supply seawater into the reduced-pressure evaporator, a seawater supply pipe is connected in the reduced-pressure evaporator,
The other end of this seawater supply pipe is inserted below the sea surface, and the pressure inside the vacuum evaporator is reduced to the atmospheric pressure or less, so that the pressure difference between the negative pressure in the vacuum evaporator and the atmospheric pressure is used to reduce the pressure from the seawater supply pipe. It sucks seawater into the evaporator.

The invention according to claim 3 is characterized in that the pressure reducing mechanism for suctioning seawater according to claim 2 is the vacuum pump for evaporating seawater according to claim 1.

According to the present invention, by sharing a vacuum pump for sucking seawater and a decompression mechanism for depressurizing the inside of the reduced-pressure evaporator, a pump for supplying seawater into the reduced-pressure evaporator can be omitted. It is possible to save power consumption.

According to a fourth aspect of the present invention, in the seawater desalination apparatus according to any one of the first to third aspects, the seawater discharge means has one end connected to the seawater discharge port of the vacuum evaporator and the other end connected to the sea surface. Side, a seawater discharge pipe provided on the side, a seawater discharge pump provided on the seawater discharge pipe, and a seawater discharge control valve provided on the discharge side of the seawater discharge pump for controlling the discharge of seawater. Features.

According to a fifth aspect of the present invention, in the seawater desalination apparatus according to any one of the first to fourth aspects, a part of the seawater discharged from the seawater discharging means is taken in and the water is sprayed in the reduced-pressure evaporator. Characterized by having seawater sprinkling means for continuously performing water spraying.

According to the present invention, the seawater sprinkling means is provided independently of the seawater discharging means by providing the seawater sprinkling means for branching a part of the seawater discharging means to sprinkle the seawater in the reduced-pressure evaporator. Eliminates the need.

According to a sixth aspect of the present invention, in the seawater desalination apparatus according to the fifth aspect, the seawater sprinkling means has one end branched and connected to the discharge side of the seawater discharge pump of the seawater discharge pipe, and the other end connected to the seawater discharge pipe. A seawater sprinkling pipe inserted into the upper part of the reduced-pressure evaporator, a sprinkling nozzle provided at an end of the reduced-pressure evaporator, and a seawater sprinkling amount control provided in the seawater sprinkling pipe to adjust the sprinkling amount of seawater. And a valve.

According to the present invention, a part of the seawater discharging means is branched, and the water is sprayed as shower-like water droplets from the upper position of the reduced-pressure evaporator by the watering nozzle which is the seawater spraying means, thereby increasing the evaporation area of the seawater. Evaporation efficiency can be improved. Also, bumping of seawater in the reduced-pressure evaporator can be prevented to prevent the salt water from flowing into the condenser side, and the quality of fresh water obtained can be improved.

Further, according to the present invention, the degree of vacuum is reduced by increasing the evaporation efficiency, and the power consumption can be reduced by reducing the load on the vacuum pump.

According to a seventh aspect of the present invention, in the seawater desalination apparatus according to the second, fourth and sixth aspects, the control means comprises: a liquid level detector for detecting the level of seawater in the reduced-pressure evaporator; A controller controls at least one of a seawater supply amount adjustment valve, a seawater discharge amount adjustment valve, a seawater discharge pump, and a seawater sprinkling amount adjustment valve based on a detection value of the position detector.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a view showing a seawater desalination apparatus according to the present embodiment, and this seawater desalination apparatus is installed on a beach.

As shown in FIG. 1, the seawater desalination apparatus 1 is provided with a decompression evaporator 2 which is a container for decompressing seawater. The reduced-pressure evaporator 2 is a closed tank type. The reduced-pressure evaporator 2 is provided with seawater supply means 3 for supplying seawater to the reduced-pressure evaporator 2 and seawater discharging means 4 for discharging seawater from the reduced-pressure evaporator 2. I have. The seawater supply means 3 and the seawater discharge means 4 are provided with a control means 5 for adjusting the amount of seawater, and control the level of seawater in the reduced-pressure evaporator 2 to be constant.

More specifically, the reduced-pressure evaporator 2 includes a seawater supply pipe 6 serving as seawater supply means 3 for supplying seawater into the reduced-pressure evaporator 2, and a seawater introduction pipe having one end provided at the bottom of the reduced-pressure evaporator 2. The evaporator 2 is connected via the port 7, and the other end is disposed on the sea surface side. The seawater supply pipe 6 is provided with a seawater supply amount adjustment valve 8 for adjusting the amount of seawater.

The reduced-pressure evaporator 2 has a seawater discharge pipe 9 as a seawater discharge means 4 for discharging seawater in the reduced-pressure evaporator 2.
Is a seawater outlet 1 having one end provided on the side of the vacuum evaporator 2.
0, and the other end is located on the sea surface side,
The seawater in the reduced-pressure evaporator 2 can be discharged.
The seawater discharge pipe 9 is provided with a seawater discharge pump 11, and the discharge side of the seawater discharge pump 11 is connected to a seawater discharge control valve 12. On the other hand, the seawater discharge pipe 9 on the discharge side of the seawater discharge pump 10 is branched and connected to a seawater sprinkling pipe 14 as seawater sprinkling means 13. The other end of the seawater sprinkling pipe 14 is inserted into the upper part of the reduced-pressure evaporator 2. In the reduced-pressure evaporator 2, an end thereof is provided with a watering nozzle 1 for spraying seawater into the reduced-pressure evaporator 2.
5 are provided. The seawater sprinkling pipe 14 is provided with a seawater sprinkling amount control valve 16 for adjusting the amount of seawater sprinkling.

In the reduced-pressure evaporator 2, a liquid level detector 17 for detecting the liquid level of seawater, which is the control means 5, is provided. The liquid level detector 17 is connected to a controller 18, and sends a signal obtained by the liquid level detector 17 to the controller 18. The controller 18 includes a seawater supply control valve 8 as the seawater supply means 3, a seawater discharge control valve 12 as the seawater discharge means 4, and a seawater discharge pump 11 and a seawater spray control valve 16 as the seawater sprinkler 13. And the liquid level detector 17
Signal to open and close each valve and start pump
By stopping, the amount of seawater in the reduced-pressure evaporator 2 is adjusted.

The reduced-pressure evaporator 2 is connected to a steam flow path 20 for introducing the generated steam into the condenser 19. Then, the steam introduced into the condenser 19 is
The refrigerant is condensed and liquefied (desalinated) by a low-temperature refrigerant supplied from the refrigerator 22 via the refrigerant supply pipe 21. On the other hand, the refrigerant whose temperature has increased due to the heat exchange with the water vapor is supplied to the refrigerant return pipe 23.
, And returns to the refrigerator 22 to be cooled.

The condenser 19 has a fresh water supply adjusting valve 2.
The fresh water supply pipe 25 provided with the fresh water supply pipe 4 is connected thereto, and fresh water is supplied to the fresh water tank 26 via the fresh water supply pipe 25. Further, an exhaust pipe 27 is connected to the condenser 19, and a vacuum pump 28 is connected to the exhaust pipe 27,
Exhaust gas is discharged to the discharge side of the vacuum pump 28.

In the seawater desalination apparatus 1 of this embodiment, the vacuum pump 28 is operated to reduce the pressure in the decompression evaporator 2 and the controller 1
The seawater supply amount control valve 8 is opened by the signal from 8, and seawater is supplied into the reduced-pressure evaporator 2 from the seawater supply pipe 6 inserted into the seawater. At this time, since the pressure inside the reduced-pressure evaporator 2 is reduced by the vacuum pump 28, the seawater flows into the reduced-pressure evaporator 2 without using a pump due to the pressure difference between the inside of the reduced-pressure evaporator 2 and the atmosphere.

After the liquid level detector 17 detects that the level of the seawater in the reduced-pressure evaporator 2 has reached an appropriate level, the seawater discharge pump 11 is activated by a signal from the controller 18 to discharge the seawater. The amount adjusting valve 12 is opened to discharge seawater. Further, the seawater supply valve 8 is opened by a signal from the controller 18 to continuously supply seawater into the reduced-pressure evaporator 2,
The seawater level in the reduced-pressure evaporator 2 is adjusted to keep the seawater level constant.

When the pressure inside the reduced-pressure evaporator 2 becomes lower than the saturated water vapor pressure of the seawater due to the operation of the vacuum pump 28, the seawater in the reduced-pressure evaporator 2 boils to generate steam. At this time, the controller 18 detects the level of the seawater, and a signal from the controller 18 is sent to the seawater supply control valve 8, which opens the seawater supply control valve 8, and enters the inside of the reduced-pressure evaporator 2. Seawater more than the amount of evaporated water is supplied. In addition, the seawater discharge pump 11 is started, the seawater discharge control valve 8 is opened, and the seawater is discharged from the reduced-pressure evaporator 2, so that the level of the seawater in the reduced-pressure evaporator 2 is kept constant. At this time, a part of the discharged seawater is adjusted in flow rate by a seawater spraying amount adjusting valve 16 according to a signal from the controller 18, and then is sprayed from the upper part of the reduced-pressure evaporator 2 as a shower-like water droplet by the spray nozzle 15. , The seawater is evaporated.

Thus, the steam generated in the reduced-pressure evaporator 2 is guided to the condenser 19 through the steam channel 20. The condenser 19 is cooled by a cooling medium, and the cooling medium is supplied from a refrigerator 22. The steam guided to the condenser 19 is cooled and condensed by the condenser 19 to become fresh water from which salts and the like have been removed, and is sent to the fresh water tank 26 for storage.

As described above, according to the present embodiment,
A seawater supply means 3 and a seawater discharge means 4 are installed in the reduced-pressure evaporator 2, and the control means 5 detects the liquid level of the seawater in the reduced-pressure evaporator 2 and discharges while supplying more than the amount of seawater. This prevents the seawater temperature in the decompression evaporator 2 from lowering due to the latent heat of evaporation, facilitates the generation of water vapor,
8 can be reduced. Further, by adjusting the supply amount of seawater and the discharge amount of seawater and utilizing the pressure difference between the inside of the reduced-pressure evaporator 2 and the atmosphere, a pump for supplying seawater can be omitted, and energy saving can be achieved.

Further, a part of the seawater discharged from the reduced-pressure evaporator 2 is sprinkled from a sprinkling nozzle 15 provided on the upper part of the reduced-pressure evaporator 2 to form shower-like water droplets, thereby increasing the evaporation area and facilitating evaporation. In addition to improving the evaporation efficiency of seawater, bumping in the reduced-pressure evaporator 2 is prevented, and the quality of freshwater is improved by preventing salt water from reaching the condenser 19 together with water vapor.

Therefore, according to the present embodiment, the reduced pressure evaporator 2
By preventing the temperature of seawater from dropping inside and controlling the level of seawater to a constant level, it eliminates the need for power to send seawater, improving the evaporation efficiency and improving the quality of freshwater obtained. It is possible to provide the seawater desalination apparatus 1 that can reduce the power consumption with respect to the amount of fresh water, save energy, and operate and maintain easily.

[0038]

As described above, according to the present invention, the quality of fresh water obtained is improved, the power consumption relative to the amount of fresh water is saved, energy is saved, and a seawater desalination apparatus with good fresh water efficiency is obtained. Can be provided.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing a seawater desalination apparatus according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Seawater desalination apparatus 2 Decompression evaporator 3 Seawater supply means 4 Seawater discharge means 5 Control means 6 Seawater supply pipe 7 Seawater inlet 8 Seawater supply control valve 9 Seawater discharge pipe 10 Seawater outlet 11 Seawater discharge pump 12 Seawater discharge Control valve 13 Seawater sprinkling means 14 Seawater sprinkling pipe 15 Sprinkling nozzle 16 Seawater sprinkling amount adjustment valve 17 Liquid level detector 18 Controller 19 Condenser 20 Steam flow path 21 Refrigerant supply pipe 22 Refrigerator 23 Refrigerant return pipe 24 Freshwater supply control Valve 25 Fresh water supply pipe 26 Fresh water tank 27 Exhaust pipe 28 Vacuum pump

Claims (7)

[Claims] 1. A closed tank type having a seawater inlet and a seawater outlet on the bottom side thereof, and a reduced-pressure evaporator for evaporating the introduced seawater under reduced pressure. A vacuum pump for reducing the pressure below, a condenser for cooling and condensing steam obtained by the reduced-pressure evaporator to obtain fresh water, and continuously supplying seawater having an amount of evaporated water or more to the reduced-pressure evaporator through the seawater inlet. Seawater supply means for supplying, seawater discharge means for continuously discharging seawater of a supply amount or less from the reduced-pressure evaporator through the seawater discharge port, and adjusting the seawater flow rate of these seawater supply means and seawater discharge means. And control means for controlling the level of seawater in the reduced-pressure evaporator to be constant. 2. The seawater desalination apparatus according to claim 1, wherein the seawater supply means includes a seawater supply pipe having one end inserted into the seawater and the other end connected to the bottom of the vacuum evaporator; Provided, a seawater supply control valve for controlling the supply of seawater, and the pressure in the reduced-pressure evaporator is reduced to an atmospheric pressure or less,
A seawater desalination apparatus having a pressure reducing mechanism for sucking seawater into the reduced pressure evaporator by the pressure difference. 3. The seawater desalination apparatus according to claim 2, wherein the seawater suction pressure reducing mechanism is the seawater evaporation vacuum pump according to claim 1. 4. The seawater desalination apparatus according to claim 1, wherein the seawater discharge means has one end connected to a seawater discharge port of the reduced-pressure evaporator and the other end disposed on the sea surface side. A seawater desalination comprising: a discharge pipe; a seawater discharge pump provided in the seawater discharge pipe; and a seawater discharge control valve provided on a discharge side of the seawater discharge pump to control a discharge amount of seawater. apparatus. 5. The seawater desalination apparatus according to claim 1, wherein a part of the seawater discharged from the seawater discharging means is taken in and the water is continuously sprayed in the reduced-pressure evaporator. A seawater desalination apparatus comprising seawater sprinkling means. 6. The seawater desalination apparatus according to claim 5, wherein one end of the seawater sprinkling means is branched and connected to the discharge side of the seawater discharge pump of the seawater discharge pipe, and the other end is an upper part in the decompression evaporator. A seawater sprinkler pipe inserted into the seawater sprinkler, a sprinkler nozzle provided at an end thereof in the reduced-pressure evaporator, and a seawater sprinkler amount control valve provided in the seawater sprinkler pipe for adjusting the amount of seawater sprinkler. Characterized seawater desalination equipment. 7. The seawater desalination apparatus according to claim 2, wherein the control means comprises: a liquid level detector for detecting the level of seawater in the reduced-pressure evaporator; and a detection value of the liquid level detector. Seawater supply control valve, seawater discharge control valve, based on
A controller for controlling at least one of a seawater discharge pump and a seawater sprinkling amount regulating valve.