RU2309125C2 - Seawater desalting device - Google Patents

Abstract

FIELD: agriculture; different branches of industry; municipal economy; production of the seawater desalting devices.

SUBSTANCE: the invention is pertaining to the devices of desalting of the seawater and may be used at planning and construction of the water-desalinating devices for production of the sweet water for agriculture, the different branches of industry and the municipal economies. The device for desalting of the seawater contains two sealed tanks, connected by the vapor pipe line. The tanks are connected to the device for heating of the seawater and for condensation of its vapors. The device includes the refrigerator, which pipe duct with the heated coolant is located below the level of the water in the first seawater tank, and the pipe duct with the cooled coolant is located in the second seawater tank. The tanks are at the height of no less than the maximal height of the liquid column of the water barometer over level of the being desalted water, approximately at the altitude of 10.5 meters. In the first tank above the water plane there is the mounted evaporation system consisting of the row of the plates; in the second tank there is the system of condensation consisting of the sprinkling system with the spray jets. Each tank has a back-pressure valve and the sensor of the tank filling up, which are located in its upper part, and on the steam pipe duct the cap is installed. In the desalting device at the expense of the created decreased pressure above the water surface the water boiling and intensive steam formation takes place with the subsequent condensation of water steam in the special cooler. At that there is no need to consume power for creation of the vacuum in the tank at the expense of usage of the principle of the inverted U - shaped tube, the filled with the water, which ends are submerged in the water.

EFFECT: the invention ensures the water boiling and intensive steam formation in the tank with the subsequent condensation of the steam in the special cooler without the need to consume the power for creation of the vacuum in the tank.

4 cl, 2 dwg

Description

The invention relates to devices for desalination of sea water and can find application in the design and manufacture of desalination plants for fresh water for agriculture, industry and utilities.

There are several ways to obtain fresh water: evaporation, electrodialysis, and reverse osmosis [1, 2]. All these methods are quite complex and energy intensive.

The removal of salts from water to a limit close to their content in distilled water (several mg / l) is called desalination, and the removal of salts to concentrations acceptable for drinking water (up to 1 g / l) is called desalination.

Desalination of water by electrodialysis or reverse osmosis is characterized by significantly lower energy costs compared to traditional distillation. During electrodialysis, selective ion-exchange membranes are used.

In reverse osmosis, semipermeable membranes that allow water molecules to pass through but retain dissolved mineral and organic substances.

Electricity consumption per 1 m ^{3 of} water desalted by electrodialysis is at least 30 kWh, and reverse osmosis is at least 15 kWh.

By electrodialysis, water can be desalted by 90%, reverse osmosis - by 98%.

In reverse osmosis plants, the operating pressure reaches 5-10 MPa (50-100 atmospheres).

As you can see, the desalination of water by electrodialysis or reverse osmosis is associated with significant energy costs, the manufacture of quite complex and expensive desalination plants, constant monitoring of their performance, repair, replacement of membranes with a limited service life, etc.

There is also a method for distillation of sea water, based on the law of decreasing the boiling point of water with decreasing pressure above its surface [3].

If you lower the pressure above the surface of the water, intensive evaporation will begin even at a temperature close to the freezing temperature. The evaporation rate depends on the temperature of the water and the pressure difference between the pressure above its surface and the pressure of saturated vapors at a given temperature. When the pressure above the surface of the water is equal to the pressure of saturated water vapor at a given temperature, boiling will stop. If continuously formed water vapor is formed, the boiling process will continue. This can be achieved in two ways: by pumping out the vapors with a vacuum pump followed by their condensation outside the zone of reduced pressure or by condensation of the vapor and removal of condensate from the zone of reduced pressure. As a third option, a combination of these methods is used [4, 5].

The disadvantage of this method is the complexity and high cost of desalination plant equipment. It is used mainly on marine vessels, with relatively small volumes of fresh water production. The cost of fresh water obtained by this method is quite large and commensurate with simple evaporation.

The invention [6] is the closest prototype of the claimed method.

The disadvantage of this solution is the low productivity of the desalination plant.

The elimination of this drawback is as follows.

In order not to waste energy on creating a vacuum in the tank, the principle of an inverted U-shaped tube filled with water, the ends of which are lowered into water, is used. In this case, a reduced pressure is created in the upper part of the tube. When the length of the ends of each tube is more than 10 meters, water breaks in its upper part, and a pressure equal to the pressure of saturated water vapor at a given temperature is established above the surface.

The sealed tank is raised to a height of approximately 10.5 meters. It has three pipelines: discharge, drain and for distilled water, the lower ends of which are below the level of desalinated water. Water, under its own weight, tends to go down, but atmospheric pressure counteracts it, so the water level will drop to about 10 meters above the level of desalinated water. Over water, a reduced pressure forms in the tank. A pump is installed on the discharge pipe, which constantly supplies fresh water to the tank, and from it the water flows by gravity back to the sea via a drain pipe. Thus, water enters the zone of reduced pressure, where it intensively evaporates.

Near the tank there is a refrigerator with two pipelines with cold and heated refrigerants, which are located inside the tank. The refrigerator is designed to condense water vapor. A pipeline with a heated refrigerant is below the water level in the tank and gives it its heat, and a pipe with a cooled refrigerant is above the water level in the tank and takes heat from the steam. The steam condenses in a cold pipeline and flows through it into a pipeline for distilled water, and from it into a container for distilled water.

The first disadvantage of this device is the low specific productivity of the desalination plant, since the rate of water evaporation is directly proportional to the area of the water mirror in the desalination tank. To obtain high performance desalination plant requires the manufacture of a sealed tank of large diameter.

The second disadvantage of this device is the low rate of condensation of water vapor in the pipeline with cold refrigerant, because due to the large surface tension of the water, droplets cannot begin to slide off the pipeline until they reach a certain size. As a result, the pipeline is covered with a significant layer of water, which prevents the transfer of heat from steam to the cold pipeline.

The aim of the present invention is to remedy these disadvantages.

This goal is achieved by the fact that to increase the open area of water on which evaporation occurs, plates with a slight slope relative to the horizontal position are installed inside the tank above the water mirror, the slope of the subsequent plate having the opposite direction to the previous one. Desalinated water continuously flows from the tank onto the top plate. Water flows from the upper plate to a lower installed plate, reverses the flow direction, again flows to a lower installed plate, changes the flow direction and so on to the water level in the tank. Thus, the evaporated area of water increases tenfold. With a small tank diameter, a large evaporation area can be obtained.

Condensation of water vapor occurs on the surface of cold water or pipelines with cold refrigerant. The condensation rate is directly proportional to the contact area of the vapor with a cold surface. Since the area of pipelines with refrigerant is limited by the internal volume of the upper part of the desalination plant, an increase in the rate of condensation of water vapor is possible only on the surface of cold water, which is sprayed inside the upper part of the desalination plant. A drop of water, falling, captures the vapor and condenses it on itself. By increasing the amount of irrigation, you can repeatedly increase the amount of condensed water.

Since the volume of the upper part of the desalination plant is used for an irrigation plant that condenses water vapor, it is cooled in a special tank to cool the water supplied for irrigation and fed to the irrigation nozzles with a pump. This tank contains a refrigerant piping that cools the water used for irrigation.

The invention is illustrated by two drawings.

Figure 1 shows the desalination plant, the internal device, figure 2 shows an embodiment of the desalination plant.

The desalination plant device for the implementation of the proposed method consists of two sealed tanks 1 and 2, mounted on a stand 3, interconnected by a steam line 4. The upper parts of the tanks are above the maximum level of the water column 5 (the level of the water column in the tube, the sealed end of which is located above, and the open end is lowered into the water) relative to the level of desalinated water 6 (sea level).

Tank 1 has two pipelines: injection 7 for sea water and drain 8 for brine. Tank 2 also has two pipelines: for draining distilled water 9 and forcing for fresh water 10. The lower ends of all pipelines are located below the level of desalinated water. The injection pipeline for sea water 7 is equipped with an intake with a filter 11 and a pump 12. The injection pipeline for fresh water 10 is equipped with a shut-off device (valve) 13 and a pump 14.

The lower end of the drain pipe 8 is equipped with a locking device (valve) 15, opening or closing it.

The pipeline for distilled water 9 contains a locking device (valve) 16.

For heating desalinated water and condensation of steam, a refrigerator 17 is located next to tanks 1 and 2.

From the refrigerator 17 to the tank 1 there is a pipeline with heated refrigerant 18, which is below the water level in the tank and heats it, and to the tank 2 there is a pipeline with cooled refrigerant 19. The pipeline with cooled refrigerant 19 serves to cool distilled water, which is pumped 20 enters the nozzles 21 of the irrigation system of the tank 2.

From above, tanks 1 and 2 have non-return valves 22, which open when the pressure in them increases and close when the pressure drops below atmospheric pressure, and tank fullness sensors 23. These sensors indicate that the tanks are full with water. Inside the tank 1 there is a sensor for the lower limit level of water 24. The height of the lower limit level of water 25 is selected so that the pipeline with the heated refrigerant 18 is always below the water level in the tank, that is, it is completely closed by water.

A number of plates 26 are mounted above the water mirror, one above the other, with a slight slope relative to the horizontal position, with the slope of the subsequent one having the opposite direction to the previous one. Desalinated water is continuously supplied to the upper plate through a pipe 27, which is taken from the same tank 1 and is pumped into it. Water flows from the upper plate to a lower installed plate, reverses the flow direction, again flows to a lower installed plate, changes the flow direction and so on to the water level in the tank.

A cover 29 is installed on the steam line 4 from the side of the tank 1. Water vapor flows through the steam line 4 into the tank 2 and enters the zone of the irrigation system with drops of cold distilled water. Cold drops fall down and capture water vapor, condensing them on yourself. Condensed distilled water flows through a conduit 9 down to a distilled water inlet basin 30. Since the outlet of the conduit 9 from the tank 2 is located above the conduit with cold refrigerant 19, the water always closes this conduit.

The principle of operation of the desalination plant is to create a reduced pressure above the surface of the water, which leads to its boiling, intense vaporization and subsequent condensation of water vapor in a special receiver. Water vapor condenses and discharges into a distilled water pool 30.

In order not to waste energy on creating a vacuum in the tank, the principle of an inverted U-shaped tube filled with water, the ends of which are lowered into water, is used. Water tends to flow out of the tube, but atmospheric pressure counteracts it. In this case, a reduced pressure is created in the upper part of the tube. With a tube longer than 10 meters in the upper part, the water breaks, and a pressure equal to the pressure of saturated water vapor at a given temperature is set above the surface. Desalinated water is pumped into the tank 1 with the tap of the drain line 15. The valve 29 on the steam line 4 is closed. At the same time, fresh water is pumped into tank 2. Air from the tanks exits through the check valves 22 located in the upper parts of the tanks 1 and 2. When the tanks 1 and 2 are filled and water begins to pour out of them through the check valves, the taps 15 of the drain pipe and the pipeline open for simultaneous signals from the tank full sensors 23 distilled water 16.

The refrigerator 17 is turned on, designed to cool distilled water and simultaneously heat desalinated water. The pipeline with the heated refrigerant 18 is below the level of desalinated water in the tank 1 and gives it its heat, and the pipeline with the cooled refrigerant 19 enters the tank 2 with distilled water and cools it. With the help of pump 20, the cooled distilled water enters the nozzles 21 of the irrigation system of the tank 2, leaving them, it splits into drops, which, falling down, capture water vapor, condense them on itself and, through pipeline 9, flow down into the receiving pool for distilled water 30.

If you do not provide a continuous supply of fresh water to tank 1, then the salt concentration in it will increase until the salt completely precipitates. This can lead to loss of operation of the desalination plant. To prevent an increase in salt concentration above a predetermined limit, fresh desalinated water is continuously supplied to the tank 1 through the pipe 7 by the pump 12. The brine with a high concentration of salt by gravity through the drain pipe 8 is continuously removed from the tank 1.

Since dissolved air is always present in water, it will come out of the water and accumulate above the surface of the water. This is especially intense under reduced pressure. As the air escapes, the water level in the tanks will drop. When the water level drops to the pipeline with heated refrigerant 18, the capacity of the installation will begin to decrease, since the heat transfer of desalinated water will begin to decrease, and part of the heat will be transferred to the steam, reducing the efficiency of the refrigerator.

To prevent stopping the distillation, periodically remove accumulated air.

This is achieved by the fact that when lowering the water level in the tank to the maximum set level 25, the lower limit water level sensor 24 generates a signal by which the taps in the drain pipe 8 and the distilled water pipe 9 are closed, and the valve 13 on the fresh water discharge pipe 10 opens. Water through the discharge pipe 7 continues to fill the tank 1 with water and air accumulated above the surface of the water is squeezed out through the check valve 22 into the atmosphere. At the same time, the pump for fresh water 14. The water fills the tank 2 and the air accumulated above the surface of the water is squeezed out through the check valve 22 into the atmosphere.

To prevent the mixing of fresh and salt water when filling the tanks through the steam line 4, a valve 29 is used, which closes when the air is extruded.

When water begins to pour out of the tanks through the non-return valves 22, the tank fullness sensors 23 generate a signal that opens the valve 15 on the drain pipe 8 and the valve 16 on the distilled water pipe 9, the fresh water pump 14 is turned off and the discharge pipe tap 13 is closed. The check valves of the tanks 22 are closed, the water level drops, a lower pressure is again created above the water surface, and the distillation process resumes.

The second embodiment of the desalination plant is that the plates 26, designed to increase the area of the water mirror, are installed in the form of a helical surface and water flows down them.

The third embodiment of the desalination plant is that the nozzles of the irrigation system are rotated relative to the axis of the tank so that the axis of the nozzles form a single-cavity rotation hyperboloid.

Information sources

1. Chemical encyclopedia. In 5 volumes - M .: Soviet Encyclopedia, 1988.

2. Physical encyclopedia. In 5 volumes - M .: Soviet Encyclopedia, 1988.

3. Matveev A.N. Molecular Physics: Textbook. manual for universities. - M .: Higher school, 1981. - 400 p., Ill.

4. Russian patent No. 2142912, class C02F 1/04.

5. Patent of Russia No. 2206510, class C02F 1/04.

6. Patent of Russia No. 2087421, class C02F 1/14.

Claims (4)

1. A device for desalination of sea water, containing two sealed tanks connected by a steam line, the first tank has a discharge and drain pipelines, the discharge pipe is equipped with a pump for continuously supplying desalinated water to the first tank, the second tank has a pipeline for distilled water, the tanks are connected to the device for heating water and condensing its vapors, which is a refrigerator, the pipeline with a heated refrigerant which is below the water level in the first tank, and the pipeline with a cooled refrigerant is It takes place in the second tank, while in the first tank there is a sensor of the lower limit water level, characterized in that the tanks are installed at a height not less than the maximum height of the liquid column of the water barometer above the level of desalinated water, in the first tank above the water mirror an evaporation system is installed, consisting of a number of plates located one above the other with a slight slope relative to the horizontal position, and a pump for supplying desalinated water from the tank to the upper plate, a condensation system is installed in the second tank, consisting of irrigation systems with nozzles and a pump for supplying distilled water colder than steam to the nozzles, while the pipeline with the cooled refrigerant refrigerant is located below the levels of distilled water in the second tank, each tank has a non-return valve and a tank fullness sensor located in its upper part , and a cover is installed on the steam line. 2. The device according to claim 1, characterized in that the plates are staggered, and the slope of the subsequent plate has the opposite direction to the previous one. 3. The device according to claim 1, characterized in that the plates are installed in the form of a helical surface. 4. The device according to claim 1, characterized in that the nozzles of the irrigation system are installed at an angle to the axis of the tank so that the water jets emerging from them form a single-cavity rotation hyperboloid.

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