RU2789939C1 - Method for desalination of salt and mineralized water and device for its implementation - Google Patents

Abstract

FIELD: fresh water production.

SUBSTANCE: inventions group relates to technology for producing fresh water extracted from sea water and other types of salty and excessively mineralized water by distillation. The method consists in that salt water after pre-treatment is sprayed using ultrasonic vibrations to form a monodispersed dispersed medium, which is subjected to evaporation to form water vapor and fine salt particles. Spraying of sea water is carried out in a layer of water or by spouting in a spray tank by means of ultrasonic transducers installed in it. The obtained monodisperse dispersed medium is sent by means of a constant air flow to an evaporation chamber with a thermal heater for the continuous formation of water vapor and fine salt particles. The steam-salt mixture flow enters the chamber for the forced separation of salt particles from water vapor. As a result of separation, salt particles accumulate in the salt collectors of the forced separation chamber, and water vapor after separation enters the heat exchanger - refrigerator for condensation and further accumulation of flowing fresh water into the storage tank. The air cavity of the storage tank communicates with the air cavity of the spray tank through a ventilation duct, while providing a through air flow of the vapor-air medium closed along the contour.

EFFECT: in-line production of fresh water in a volume of at least 80% of the initial volume of non-desalinated water and a mixture of dry salts without brine formation at minimal energy costs.

2 cl, 1 dwg

Description

The invention relates to a technology for obtaining fresh water extracted from sea water and other types of saline and excessively mineralized water by distillation, and can be used to provide water supply in areas with insufficient fresh water supplies, for desalination of industrial wastewater, as well as in water regeneration plants from wash water and urine in spacecraft life support systems.

A known method of desalination of sea water, including the supply of desalinated water under pressure to the evaporation zone, evaporation at reduced pressure with the removal of the resulting gas-vapor mixture into the condensation zone, condensation of steam by contact with cooled circulating fresh water, the removal of released gases and desalinated water and draining the brine, and evaporation and condensation processes are carried out in the respective zones located at a height exceeding the barometric height of the column of desalinated water above the free surface of sea water, the resulting vapor-gas mixture is removed to the condensation zone through a narrowing channel with an increase in the mixture velocity to a velocity equal to 0.6-1, 0 from the speed of sound, the pressure of circulating fresh water at the inlet to the condensation zone is maintained at a level sufficient to implement the mode of supersonic flow of the vapor-gas-liquid mixture in the condensation zone, while the release of released gases is carried out continuously (patent RU 2393995 C1, published 10.0 7.2010).

A known method for obtaining pure water from an aqueous salt solution, for example, sea and mineralized waters and industrial effluents, including heating, evaporation, steam removal from the steam space for condensation, evaporation-condensation processes are carried out in a thermostat with an ambient temperature and above, the supply of saline for the evaporation and removal of condensate of pure water and salt solution with a high concentration of salts is carried out by means of a countercurrent heat exchanger, and between the processes of evaporation of pure water from an aqueous salt solution and its condensation, the process of adiabatic vapor compression is included, which makes it possible to return to the cycle (regenerate) the heat of condensation (patent RU 2565187 C1, published 10/20/2015).

A known method of desalination of sea water, which consists in the supply of desalinated water to the evaporation zone, in heating and subsequent evaporation of desalinated water while lowering the pressure in the evaporation zone, in the removal of the resulting steam into the condensation zone with the possibility of steam condensation through its contact with the surface of a refrigerator cooled by circulating water , as well as in the outlet of desalinated water and the drain of brine, the desalinated water in the evaporation zone is placed in open single vessels or in a group of mechanically connected open vessels, ensures its circulation in the evaporation zone, circulates the vapor-gas mixture through the desalinated water, and also carries out a vibrational effect on vessels with desalinated water (patent RU 2598087 C1, published on September 20, 2016).

Known installation for desalination of sea water containing a tank of sea water, an evaporation system, a system for supplying thermal energy, a separation system, including a heat exchanger-refrigerator, a separator, a storage tank for fresh water, pipes for heating are installed inside the tank with sea water in its lower part. of water, connected with the thermal energy supply system, in the upper part of the tank above the water mirror there are nozzles for supplying hot air, connected with the thermal energy supply system, a vertical pipe is installed on the top cover of the tank, in the lower and upper parts of which there are fittings for supply and discharge, respectively sea water, communicated with the tank by a pipeline in which the pump is installed, the outlet of the vertical pipe is connected to the separation system (patent RU 125185, published on February 27, 2013).

Known desalter of sea water, containing a working chamber made of heat-insulating material, in which thermoelectric batteries (thermoelectric batteries) are placed, the working chamber of the installation is divided into the following zones: an evaporation zone and a condensation zone, the working chamber includes channels for supplying sea water, draining fresh water and of concentrated brine, the heat-releasing junctions of one thermopile are brought into thermal contact with the needle radiator located in the sea water supply channel, and the heat-absorbing junctions are brought into the condensation zone and brought into thermal contact with the heat-absorbing junctions of another thermopile, through the needle radiator, the thermopile is powered by a programmable source of electrical energy, the working chamber contains a wave-like metal mesh located at an angle in the condensation zone, a heater, the surface of which is brought into thermal contact with the heat-generating junctions of the thermopile through a needle radiator, a heat exchanger consisting of three sections: th water, sections of sea water and sections of concentrated brine, as well as a channel for supplying air to the condensation zone, which accelerates the condensation process by blowing steam and mixing with it in the condensation zone (patent RU 2448909, published 04/27/2012).

The disadvantage of the known methods and devices for desalination of salty mineralized water is the complexity of their industrial implementation. Also, the known technical solutions are characterized by significant energy costs for the production of a unit volume of fresh water, which is associated with the need to heat the volume of water to the boiling point of the source water or to create a reduced pressure (vacuum) in the water evaporation zone. In addition, the output of fresh water does not exceed half of the volume (no more than 50%) of the original salt or sea water. The resulting secondary concentrated salt or sea water brine must be disposed of without violating environmental standards, which also requires additional energy and material costs.

Closest to the claimed method is the method of desalination of sea water, which consists in the fact that sea water after pre-treatment is fed into an ultrasonic resonator nozzle, from which dispersed sea water enters the evaporation chamber, the water vapor formed in which enters the heat exchange chamber for condensation, and the resulting during the evaporation process, dry salt particles due to gravitational forces settle in the lower part of the evaporation chamber, after condensation in the heat exchange chamber, fresh water is collected in a fresh water tank (CN patent 101838079, published 06/27/2012).

In addition, the closest to the claimed is a device for seawater desalination, containing a plant for preliminary filtration of salt water, the output of which is connected to a flow-through ultrasonic resonator nozzle that provides continuous spraying of seawater into the evaporation chamber, made in the form of a high-frequency cylindrical electric inductor with metal plates inside, which provide, due to the induction of a high-frequency electromagnetic field, heating to the boiling point of atomized sea water, the evaporation chamber in the lower part is equipped with a salt collection container with a pipe for draining water, and in the upper part it is equipped with a pipe for removing the resulting steam into the chamber for condensation made in the form of a coiled pipe placed in a container with a cooling medium and at the outlet of which there is a tank with a vent for the accumulation of fresh water (CN patent 101838079, published 06/27/2012).

A common disadvantage of the known method and device for desalination of sea water is the impossibility of their implementation for the full desalination of sea or salt water, regardless of the concentration of salts in the water. This is due to the fact that the continuous in-line spraying of sea water by ultrasonic nozzles directly into the evaporation chamber creates excess pressure and, accordingly, a flow of water vapor together with fine dry salt particles that form as a result of instantaneous boiling of dispersed sea water. Moreover, finely dispersed salt particles entrained by the flow of water vapor due to aerodynamic pressure forces, which exceed the force of gravity for a particular salt particle, move into the condensation zone. In this case, the salt particles are returned by dissolution to the resulting condensate, and also partially by the steam flow they are transferred to the reservoir for the accumulation of fresh water, in which they continue to dissolve. As a result, instead of fresh water, a partially desalinated solution of sea or salt water is obtained, in addition, non-condensed water vapor (approximately 20% of the total volume of steam formed) is carried away through the vent in the fresh water storage tank together with fine salt particles in a proportion corresponding to the salt concentration in the original sea water. It should also be noted that when sea water is sprayed by ultrasonic nozzles directly into the evaporation chamber, the effect of coalescence of small drops of dispersed sea water into large drops is observed, which partially evaporate, moreover, a large part of them is not subject to entrainment with the formed water vapor and it settles in the initial salt form on the walls of the evaporation chamber in the form of large drops, which subsequently flow into the lower part of the evaporation chamber, additionally mixing with a small proportion of salt particles that are not carried away with water vapor. In this case, a brine of a higher concentration is formed than in the original sea water.

The physical phenomena described in the previous paragraph and the results of the manifestation of these phenomena were observed in a laboratory experimental setup with transparent walls made of plexiglass, made by the author to test the performance of the known method and device for seawater desalination according to patent CN 101838079.

Thus, the practical implementation of the invention according to the patent CN 101838079 showed the impossibility of its effective implementation in the form in which it is given in the claims and description of the invention, including graphic materials.

The technical objective of the present invention is to create an environmentally friendly and energy-efficient technology for desalination of salt (sea) and mineralized water.

The technical result of the present invention is the creation of a method and device for the desalination of salt (sea) and mineralized water, which provide, at minimum energy costs, the in-line production of fresh water in a volume of at least 80% of the initial volume of non-desalinated water and a mixture of dry salts for their subsequent use in various industries.

The technical result is achieved by the fact that in the method of desalination of salt and mineralized water, which consists in the fact that salt water after pre-treatment is sprayed using ultrasonic vibrations with the formation of a monodisperse dispersed medium, which is subjected to evaporation with the formation of water vapor and fine particles of salts, the released water vapor subjected to condensation by means of a heat exchanger - refrigerator, the resulting water flows by gravity into the storage tank, according to the invention, sea water is sprayed in a layer of water or by spouting in the spray tank using ultrasonic transducers installed in it, the resulting monodispersed dispersed medium is sent to the evaporation chamber by means of a constant air flow with a thermal heater for the continuous formation of water vapor and fine salt particles, the flow of which in the form of a steam-salt mixture enters the forced separation chamber separation of salt particles from water vapor, as a result of separation, salt particles accumulate in the salt collectors of the forced separation chamber, and water vapor after separation enters the heat exchanger - refrigerator for condensation and further accumulation of flowing fresh water into a storage tank, the air cavity of which communicates with the air cavity of the spray tank by means of a ventilation duct, while providing a through air flow of the steam-air medium closed along the contour.

In addition, a device for implementing the proposed method, containing a plant for preliminary filtration of salt water, the output of which is connected to a device for ultrasonic atomization of salt water supplied in dispersed form to the evaporation chamber, the output of which is connected to the inlet of a heat exchanger - refrigerator for condensing water vapor, on the outlet of which is a storage tank for fresh water, according to the invention, the device for ultrasonic spraying of salt water is made in the form of a spray tank, the inlet of which is connected to the outlet of the salt water pre-filtration unit, ultrasonic transducers are installed in the spray tank, providing spraying in a layer or spouting salt water , the outlet of the spray tank is connected to the inlet of the evaporation chamber with a thermal heater for supplying the resulting monodisperse dispersed medium into it, the outlet of the evaporation chamber is connected to the inlet of the separation chamber for giving it the resulting steam-salt mixture, the separation chamber is equipped with salt collectors for the accumulation of salts separated from the water vapor, and the outlet of the separation chamber is connected to the inlet of the heat exchanger - refrigerator for supplying water vapor purified from salt particles for its subsequent condensation and obtaining fresh water, which flows from the outlet of the heat exchanger-refrigerator into a tank for accumulating fresh water, and the air cavity of this tank is connected to the spray tank by means of a ventilation channel, thus forming a through air flow of a vapor-air medium closed along the contour, for which at least one air fan.

The proposed method for desalination of salt water and a device for its implementation are based on the physical principles of acoustic atomization of liquids using vibrations in the ultrasonic range (Ultrasound. Little Encyclopedia. Head. Ed. I.P. Golyamin. - M: "Soviet Encyclopedia", 1979, p. 297-298). In this case, two types of ultrasonic liquid atomization can be used: layer atomization or fountain atomization. Spraying in the layer, in practice, is carried out on the surface of the layer (0.5-1.5 mm) of the liquid covering the surface of the ultrasonic transducer (emitter). In such spraying, oscillations with a frequency in the range of 27-50 kHz are used, the liquid droplets formed during spraying are tens of microns in diameter. The performance of ultrasonic spraying in the layer reaches several tens of liters per hour per ultrasonic frequency converter 27 kHz with a power consumption of less than 100 W. Spraying in the fountain, as a rule, is carried out using waves of an ultrasonic transducer (emitter) with a frequency of 1-3 MHz, emitted from the depth of the liquid (2.5-8.5 cm). When spraying in a fountain, drops with a diameter of 2-4 microns are formed, the maximum productivity of such spraying is approximately 400-500 ml per hour for one 1 MHz ultrasonic frequency converter with a power consumption of 20-25 W. The monodisperse medium (aerosol) formed as a result of spraying is sufficiently stable for a sufficient time necessary for the transformation of this medium into fresh water and a dried mixture of salts. After ultrasonic atomization of salt water (regardless of the type of such atomization), the resulting monodisperse medium is fed to evaporation to obtain a mixture of water vapor and fine salt particles. Evaporation can be carried out using various physical principles: electrical heating, microwave heating, gas burners, etc. It should be noted that at this stage of desalination, the phase state of water droplets is transformed into another phase state - steam, and the salts dissolved in water drops are converted into solid fine particles. The next stage of desalination is the separation of the steam-salt mixture into two components: steam and fine salt particles. This process is carried out by a separation chamber, in which various physical principles for separating solid particles from gases can also be used: centrifugal forces; electrostatic fields, aerodynamic forces, etc. In the separation chamber, coarse salt particles are also collected (accumulated) in dry form using removable salt collectors. From the separation chamber, the steam enters the heat exchanger-refrigerator, in which the steam condenses and the final production of fresh water takes place. Cooling to the required dew point in the heat exchanger - refrigerator is also possible using various physical principles: cooling with the help of a coolant (water, freon, etc.); thermoelectric Peltier effect: Ranque vortex effect, etc. Fresh water from the heat exchanger-cooler flows into the storage tank, the air cavity of which communicates with the air cavity of the spray tank using a ventilation channel, which forms a through air flow of the steam-air medium closed along the contour with the help of a fan installed in it. Due to this, a forced supply of a monodisperse dispersed medium for evaporation, subsequent separation and condensation of the vapor is ensured. At the same time, approximately 60% of the volume of steam produced at the outlet of the separation chamber is condensed in the heat exchanger - refrigerator. The medium remaining in a vapor state with a temperature of 50-60°C enters the air cavity of the storage tank, mixes with air, enters the ventilation duct and returns to the spray tank with the air flow. In the spray tank, the vapor-air mixture is mixed with the monodisperse medium, while providing its heating, and further reducing the energy costs for evaporation. As a result of the closed steam-air circuit of the desalination device and the continuous supply of salt water to the spray tank, a continuous desalination process is ensured without heat loss and steam emission. As a result, almost the entire volume of water contained in the initial volume of salt water is subjected to desalination with minimal energy costs.

The essence of the invention is illustrated by the drawing, which shows a diagram of a plant for the desalination of salt and mineralized water.

The device for desalination of salty (mineralized) water contains a plant 1 for preliminary filtration of salty water, the output of which is connected to the inlet of the spray tank 2. In the spray tank 2, filled to a constantly maintained level with filtered salt water, ultrasonic transducers (emitters) 3 are placed in the water column. connected to an ultrasonic generator (conditionally not shown) and fixed on a common radiating plate 4 installed in a floating cassette 5. Floating cassette 5 provides a constant thickness of the surface layer of the liquid above the plate 4, which contributes to efficient and stable performance of ultrasonic atomization of salt water. The number of ultrasonic transducers 3 is selected from the required salt water atomization capacity. For example, for a salt water spraying capacity of 500 liters per hour, 6-8 ultrasonic transducers with a frequency of 27 MHz and a total power consumption of 300-400 W are sufficient. As a radiating plate 4, you can use a metal sheet 3 mm thick made of stainless steel grade 12X18H10T. The outlet 6 from the spray tank 2 is aligned with the entrance to the evaporation chamber 7, in which an electric thermal heater 8 is installed, connected to an adjustable power supply 9 to select the optimal operating voltage. The thermal heater 8 is of an air-flow type with a system of plate channels that provide instantaneous evaporation of fine droplets of a monodispersed medium obtained at the outlet of the spray tank 2. The temperature inside the plate channels of the heater 8 is maintained by a power supply 9 and a built-in temperature control system at a level of at least 150°C. The outlet 10 of the evaporation chamber is aligned with the inlet of the separation chamber 11 for supplying the steam-salt mixture formed as a result of evaporation into it. In the separation chamber 11 for the forced separation of water vapor from solid salt particles, a shaft 12 is installed, on which the blades 13 and blades 14 are fixed to create a forced aerodynamic flow inside the chamber 11. The shaft 12 is connected to the shaft of the electric motor 15, which ensures its rotation at a speed of at least 5000 rpm. In the zone of rotation of the blades 13 on the axial periphery of the separation chamber 11 there are salt collectors 16 for the accumulation of salts separated from the water vapor due to centrifugal forces of rotation. Salt collectors 16 can be made removable for its replacement after filling with salts; for this, the separation chamber 11 can be equipped with side hatches or a cover, depending on the specific design of the salt collectors. The outlet 17 of the separation chamber 11 is combined with the inlet of the heat exchanger-refrigerator 18 for supplying water vapor freed from salts for condensation. Heat exchanger-refrigerator 18 can be made with channels for condensation slotted or tubular type, around which there is a constant selection of heat, for example, due to cold (at a temperature of 14-16°C) running water. These channels can be installed obliquely with respect to the horizon, as shown in the drawing, in which case the fresh water resulting from the condensation of steam flows independently into the container 19 for the accumulation of fresh water. The air cavity 20 of the fresh water storage tank 19 communicates with the spray tank 2 via a vent 21 to return uncondensed water vapor to the salt water spray zone, thereby heating the monodispersed salt water mixture. This further reduces the heat energy consumption for the evaporation of a monodispersed mixture of water and salts. At least one air fan 22 is installed in the ventilation duct 21, which provides a through air flow of the vapor-air medium closed along the contour of the desalination plant, which makes it possible to additionally provide forced supply of atomized salt water to the evaporation chamber 7 and further, as described above. The fan 22 can also be connected to an adjustable power supply (not shown conditionally) in order to be able to control the performance of the device according to the air flow of the steam-air circuit. After collecting a certain volume of fresh water in storage tank 19, it is drained for further use, and the newly obtained fresh water continues to accumulate in tank 19 again.

To ensure the correct and efficient operation of the proposed device for desalination of salty (mineralized) water, the following procedure must be followed to start the operation of the desalination device:

- first of all, it is necessary to turn on the fan 22 to create an air flow in the through circuit of the device, which includes all the enlarged elements (spray tank 2, evaporation chamber 7, etc.) and the ventilation channel 21;

- secondly, turn on the electric motor 15, which will eliminate air pockets in the evaporation chamber 7 of the thermal heater 8;

- third turn on the thermal heater 8;

- ultrasonic transducers 3 are turned on last. The operation of the desalination device according to the above technology can be carried out continuously with a constant supply of salt water to the spray tank 2.

To carry out preventive and routine maintenance, including emptying salt collectors 16, the operation of the desalination device is stopped in the following sequence:

- turn off ultrasonic transducers 3;

- after 3-5 minutes turn off the thermal heater 8;

- after 5 minutes turn off the motor 15;

- after another 5 minutes turn off the fan 22.

After the completion of preventive and routine maintenance, the desalination device is switched on in the manner described above.

The author developed and manufactured an experimental setup based on the present invention, the tests of which confirmed the effectiveness of the proposed technical solution. In the experimental installation, the volume of fresh water obtained was 80.36% of the initial volume of salt water, which is due to the fact that, due to the simplification of the design and technical difficulties, the complete tightness of the steam-air path of the installation was not ensured.

To compare the result obtained, we can cite the known data on the degree of desalination of salt water in different ways:

- when using reverse osmosis, the yield of fresh water is from 15% to 25% of the initial volume of salt water, the resulting brine is either drained or disposed of at additional costs;

- with classical distillation, the yield of fresh water is from 30% to 50% of the initial volume of salt water, the resulting brine is either drained or disposed of at additional costs.

Thus, the proposed technology for desalination of salty (mineralized) water significantly increases the efficiency of the technical characteristics of both the technology as a whole and specific designs of desalination plants based on this desalination technology.

Claims (2)

1. The method of desalination of salt and mineralized water, which consists in the fact that salt water after pre-treatment is sprayed using ultrasonic vibrations to form a monodisperse dispersed medium, which is subjected to evaporation with the formation of water vapor and fine salt particles, the released water vapor is condensed by means of a heat exchanger - refrigerator, the resulting water flows by gravity into the storage tank, characterized in that the spraying of sea water is carried out in a layer of water or by spouting in the spray tank by means of ultrasonic transducers installed in it, the resulting monodisperse dispersed medium is sent to the evaporation chamber with a thermal heater by means of a constant air flow. continuous formation of water vapor and fine salt particles, the flow of which in the form of a vapor-salt mixture enters the chamber for the forced separation of salt particles from water vapor, as a result During separation, salt particles accumulate in the salt collectors of the forced separation chamber, and water vapor after separation enters the heat exchanger - refrigerator for condensation and further accumulation of flowing fresh water into the storage tank, the air cavity of which communicates with the air cavity of the spray tank through a ventilation channel, while providing a closed along the contour of the through air flow of the steam-air medium. 2. A device for implementing the method according to claim 1, containing a salt water pre-filtration unit, the output of which is connected to a device for ultrasonic atomization of salt water supplied in dispersed form to the evaporation chamber, the output of which is connected to the inlet of a heat exchanger - refrigerator for condensing water vapor , at the outlet of which there is a storage tank for fresh water, characterized in that the device for ultrasonic atomization of salt water is made in the form of a spray tank, the inlet of which is connected to the outlet of the salt water pre-filtration unit, ultrasonic transducers are installed in the spray tank, providing atomization in the layer or by spouting salt water, the outlet of the spray tank is connected to the inlet of the evaporation chamber with a thermal heater to supply the resulting monodisperse dispersed medium into it, the outlet of the evaporation chamber is connected to the inlet of the separation chamber to supply it with of the steam-salt mixture, the separation chamber is equipped with salt collectors for the accumulation of salts separated from the water vapor, and the outlet of the separation chamber is connected to the inlet of the heat exchanger-refrigerator for supplying water vapor purified from salt particles for its subsequent condensation and obtaining fresh water, which flows from the outlet of the heat exchanger - refrigerator into a tank for accumulating fresh water, and the air cavity of this tank is connected to the spray tank by means of a ventilation duct, thus forming a through air flow of the steam-air medium closed along the contour, for which at least one air fan is installed in the ventilation duct .

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