RU2627369C1 - Method of liquid degasation and device for its implementation - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: degasation device contains a chamber (4) for the liquid to be degassed with an aerator (1), injection pipes (2) with spraying holes (3) providing the cavitation effect and the jet formation; air pipes (6) for air supply and removal of discharged gases, made on opposite sides of the chamber (4). The air pipe (6) is equipped with a fan (5) and a hydraulic seal (7). The spraying holes can be in the form of cross-sections of diffuser nozzles. In the chamber (4) of the degassing device, the liquid aeration in the flow is carried out, during which the liquid is saturated with air and cavitation bubbles are created. Thereinafter, hydrodynamic cavitation is carried out by means of reducing the pressure in the liquid flow to a value equal to the pressure of saturated vapours of this liquid at a given temperature or pressure, at which discharging dissolved gases therefrom begins. The discharged gases are vented by air stream with simultaneous mechanical spraying of the liquid as a result of hitting the jet against the wall, which ensures separation and removal of the dissolved gases.

EFFECT: increasing the efficiency of liquid cleaning due to saturation of water with oxygen, oxidation of pollutants, separation of dissolved gases.

3 cl, 1 dwg, 1 tbl, 2 ex

Description

The method of degassing a liquid and a device for its implementation relate to the field of purification of drinking, industrial, waste water and various liquids from the gases contained in them. The inventions can be used in public water supply, water treatment and various industries for the purification of groundwater used for drinking water supply to the population, the purification of groundwater used for technological supply of water to industrial facilities, the purification of drinking water, the treatment of industrial wastewater, the blowing of dissolved gases, such like chlorine, ammonia, hydrogen sulfide, etc., deferrization of water, activation of water, adjustment of the pH level, cooling of water used as heat ositelya may be used as a reactor.

There are chemical and physical methods of degassing water. The essence of the first is to add reagents that bind the gases dissolved in water. Chemical methods of degassing require strict control over the amount of reagent added to water, since any excess of the degasser degrades the properties of water. Physical methods of degassing water are more often used: by heating, degassing by ultrasound, evacuation, and a method when gas is released from water by centrifugal force, etc. is used for degassing. Physical degassing methods have several advantages: their use does not require reagents that complicate the cleaning process ; the salt composition of the water does not change, the working conditions of the maintenance staff improve. But the problem of an effective degassing method that does not require expensive equipment and high energy costs remains very relevant.

So, the invention according to patent RU 2556937 (B01D 19/00; C02F 1/20; F15B 21/04; F15B 21/12 published July 20, 2015) is aimed at increasing the efficiency of the method of degassing liquid on a grid in an open flow tank of an open type of electro-hydromechanical systems , for example, a hydraulic hydraulic system by intensifying the degassing process due to the multi-stage processing of the liquid on the grid. A method for degassing a working fluid of an electro-hydromechanical system involves degassing a working fluid on a grid in a flow tank, while the grid is subjected to low-frequency transverse vibration, and a gas-liquid layer with a high-frequency pulsating pressure of low intensity is created at the inlet of the grid.

The group of inventions for patent SU 1664359 (B01D 19/00, publication date 07/23/1991 g) relates to a method for degassing a liquid and a device for its implementation. The aim of the invention is to increase the efficiency of liquid degassing and reduce energy consumption, as well as simplifying the design of the device. A sealed gas chamber is placed in the liquid and oscillations in the liquid are excited periodically and at a certain frequency. The device comprises a container in which a toroidal gas-filled elastic chamber is freely mounted on a vertical rod. A floating perforated disk is placed on the surface of the liquid. The causative agent of vibrations is made in the form of a pulsator.

The invention according to the patent RU 2001653 (B01D 19/00, publication date 10/30/1993) is aimed at increasing the efficiency of degassing a working fluid of a relatively low specific gravity while ensuring its filtration. The working fluid (RH) is preliminarily partially degassed and filtered in the filtration chamber, from where the RJ is supplied in the form of jets to the separation chamber of the degasser (KD) with a rotating rotor, while the filtration chamber is periodically informed through the KD with the rarefaction chamber, and the KD is sealed with a peripheral ring layer , to which a vacuum is applied, is filtered through the side wall of the rotor and removed from it. The device is made with an additional filtering chamber. The rotor is made with radial blades and a side wall with pass-through filtering elements and placed inside the housing. In the turbo separation version of the turbine blades, turbine blades are attached to the inner ends of the blades, and a screw auger along the generatrix of the rotor is attached to the outer ends of the blades.

All of these inventions are aimed at improving the degassing efficiency in various ways and devices. Meanwhile, this problem has not been solved by known solutions.

The prior art method for degassing a liquid and a device for its implementation (RU 2166349, B01D 19/00, publication date 05/10/2001) in which the liquid is supplied under pressure through a spray head into a vacuum chamber. The gas-liquid mixture flow formed at the outlet of the chamber is fed into a closed conical zone tangentially to the lateral surface of the closed zone and at an angle to the axis of the closed zone and gives the flow a rotational and translational motion. The flow forms a spiral vortex with a vertical axis and a swirl radius decreasing downward. The flow is separated by centrifugal force into the liquid and gas phases. A device that allows to implement the method includes a nozzle for supplying a degassed liquid, a spray head consisting of a nozzle and a nozzle fixed to its end, a vacuum chamber. A cyclone is installed at the outlet of the vacuum chamber. The axis of the vacuum chamber is directed tangentially to the side surface of the cyclone and at an angle to the axis of the cyclone. The invention provides for the deep release and separation of aggressive gases from a fluid stream.

The disadvantages of the method and device is the presence of a vacuum chamber, which complicates and increases the cost of the process. In addition, the method uses only three physical processes: increasing the surface area of the water-air interface (spraying), blowing, gas separation under the action of centrifugal force, which does not allow for effective water purification.

A method for degassing a liquid and a device for its implementation, known from RF patent No. 2315646 (B01D 19/00, C02F 1/36, publication date 01/27/2008), adopted as the nearest analogue for the corresponding object. The degassing of a liquid consists in the fact that a rotational motion is imparted to the liquid mass by acting on it with an acoustic field in a tangential or tangential longitudinal direction with respect to the axis of rotation of the liquid volume, by means of which the gas phase and the liquid are separated. Degassing is carried out in a device containing a chamber for a degassed liquid, nozzles for supplying a gas-liquid mixture and drainage of liquid, while the chamber is equipped with acoustic emitters, the active surface of which is installed in a tangential or tangential longitudinal direction with an offset relative to each other in the axial direction of the chamber. Also, the degassing chamber is equipped with an additional acoustic emitter, the active surface of which is installed in the longitudinal direction relative to the axis of the degassing chamber.

The disadvantage of this method and device is the technical complexity of the implementation, which increases the cost of the process. Another disadvantage is the use of only one physical effect for cleaning - cavitation, which reduces the effectiveness of water treatment.

The present invention is aimed at improving the efficiency of purification of drinking, industrial, wastewater and various liquids from the gases contained in them in a simpler way and device to reduce energy costs and increase the volume of purified liquid with a high content of dissolved gases. The solution of these problems makes it possible to obtain a combination of essential features of a technical result, which consists in increasing the efficiency of liquid purification by saturating the water being treated with oxygen in the air, oxidizing pollutants contained in the water, separating and removing dissolved gases, and activating water. When implementing the inventions, one more result is also achieved - increased heat transfer between the working fluid and the air.

The solution of the tasks and the achievement of technical results is achieved by the fact that, according to the proposed method, in the chamber of the degassing device, aeration of the liquid is carried out in a stream during which the water being treated is saturated with air and cavitation bubbles are created, then hydrodynamic cavitation is carried out by reducing the pressure in the liquid stream to a value equal to the saturated vapor pressure of this liquid at a given temperature or the pressure at which the evolution of dissolved gases from it begins (gas avitatsiya) by increasing the flow velocity in the jets, the working fluid entering the zone of lower pressure, increasing the pressure supplied working fluid to the low pressure zone, expanding the flow after its contraction, creating cavitation pockets of bubbles of undissolved air aspirated into the liquid during the pre-aeration; after which they provide a blow-off of the released gases by an air flow with simultaneous mechanical spraying of the liquid as a result of the impact of the jet against the wall, which ensures the separation and removal of dissolved gases.

The technical result is also achieved by the proposed degassing device for implementing the method, comprising a chamber (4) for a degassed liquid provided with an aerator (1); discharge nozzles (2) in which the pressure increases with choking holes (3), providing the effect of cavitation and the formation of jets; air nozzles (6) for supplying air and exhausting evolved gases made from opposite sides, while the air supply nozzle is equipped with a fan (5); at least one water seal that prevents separated gases from entering the degassed liquid and re-dissolving them (7). To increase the effect of cavitation, the cross-sectional profiles of the choking holes can correspond to the cross-sectional profile of the diffuser nozzle.

The essence of the technical solutions is illustrated by the drawing, which presents a General view of the degassing device.

To eliminate the above drawbacks, a method of liquid degassing and a device for its implementation are proposed, including four physical processes: preliminary aeration of the liquid, subsequent hydrodynamic cavitation, mechanical spraying of the liquid as a result of the impact of the jet against the wall, and blowing off of the gases released by the air stream.

The device is a degassing chamber (4), equipped with an aerator (1) in the form of a compressor or ejector, forcing air into the fluid stream, discharge pipes (2), in which the pressure increases and equipped with choking holes (3) that provide the formation of jets. It is preferable to carry out cross-sectional profiles of scented holes 3 in the form of cross-sections of diffuser nozzles. In the degassing chamber (4), cavitation occurs, an increase in the interface between the water-air media and the blowing of the evolved gases. The chamber (4) contains at least two air nozzles (6), through which air is supplied and exhaust gases are vented. The air supply pipe (6) contains a fan (5) that creates an air flow in the degassing chamber (4). A water seal (7) prevents the entry of gases into the stream of purified liquid.

The design of the degassing device provides an implementation of the method, including the following steps.

Aeration of the liquid in the stream, during which the treated water is saturated with air. In this case, the oxidation of dissolved gases and organic substances contained in the liquid, the displacement of dissolved gases by the dissolved air from the working fluid, the formation of nuclei, in which cavitation bubbles subsequently nucleate and grow, take place. Aeration of the liquid in the stream can be either pressure through a compressor or injection using a venturi unit.

Hydrodynamic cavitation is achieved by increasing the pressure in the fluid flow in the discharge pipes in front of the choking holes by reducing the cross section with a sharp decrease in pressure after them due to an increase in the flow rate and reduced pressure in the degassing chamber during blowing. It is advisable to make choking holes in the form of sections of diffuser nozzles, which enhances the effect of cavitation. At this stage, there is increased oxidation of pollutants contained in water, such as iron, hydrogen sulfide, organic compounds, etc. due to an increase in temperature inside cavitation bubbles, destruction of water clusters (activation), improved mixing of liquids and colloidal compositions. The boundary conditions of cavitation can destroy pollutants and organic molecules.

Hydrodynamic cavitation in the device is due to:

- reducing the pressure in the fluid flow to a value equal to the saturated vapor pressure of this fluid at a given temperature or pressure at which the release of dissolved gases from it (gas cavitation) begins by increasing the flow rate in the jets, the flow of the working fluid into the zone of reduced pressure;

- increasing the pressure of the incoming working fluid in front of the low pressure zone;

- expansion of the stream after its narrowing;

- creating foci of cavitation with bubbles of undissolved air entering the liquid during preliminary aeration;

- the presence of dissolved gases in the working fluid.

The following describes in detail the conditions for the occurrence of cavitation and their achievement in the proposed solution.

1. When the fluid is subjected to pressure below the threshold (tensile stress), then the integrity of its flow is violated, and vaporous cavities are formed. When the local fluid pressure at a certain point drops below the value corresponding to the saturation pressure at a given ambient temperature, then the fluid goes into a different state, forming mainly phase voids, which are called cavitation bubbles. The leading role in the formation of bubbles during cavitation is played by gases released into the resulting bubbles.

Cavitation occurs when the liquid pressure is equal to the saturated vapor pressure of this liquid at a given temperature or pressure at which the release of dissolved gases from it begins (gas cavitation).

In the claimed invention, in a liquid stream, a pressure drop occurs in the region of increased velocities. The reason for cavitation is the occurrence of large local velocities leading to a decrease in pressure. If the pressure turns out to be less than the vapor pressure, vigorous evolution of dissolved gases and evaporation of the liquid begin in the corresponding places of the flow, it begins to boil and cavitation cavities are formed in it, consisting of bubbles filled with steam.

As the flow rate increases, pressure drops. It may become lower than the saturation pressure. As a result, bubbles appear in it containing a mixture of vapor and gas dissolved in a liquid. At a flow rate of 14 m / s (at a temperature of 20 ° C and in the absence of air bubbles, as well as dissolved gases), conditions are created for the occurrence of cavitation regimes. With increasing speed, the effect of cavitation increases.

The installation of choking holes having a cross section much smaller than the cross sections of the discharge nozzles provides an increase in the flow pressure in front of them and an increase in the fluid velocity in the jets. The speed increases in direct proportion to the ratio of the cross-sectional area of the discharge pipes to the cross-sectional area of the choke holes. The cavitation effect increases in proportion to the square of the flow velocity.

2. The increase in pressure of the incoming working fluid in front of the low pressure zone (cavitation zone) above 4 m (at a temperature of 20 ° C and in the absence of air bubbles, as well as dissolved gases).

The increase in pressure in the fluid flow in the discharge pipes in the proposed method occurs due to the narrowing of the flow cross section in the choking holes. In the presence of dissolved gases and germinal nuclei in the working fluid, as well as an increase in temperature, the pressure may be lower than 4 m.

3. The occurrence of cavitation as a result of the expansion of the stream after its narrowing.

In the claimed solution, when the fluid flows through the local narrowing of the pipe, the speed increases and the pressure drops, which causes the appearance of a cavitation zone.

When the fluid passes through the choking hole, it instantly compresses with an increase in local pressure and subsequent expansion in the stream with a decrease in pressure and the formation of a cavitation zone.

The area of narrow sections of the choking holes is much smaller than the area of the discharge pipes, behind these sections the bulk of the liquid moves in the form of a free stream, accompanied by a foamy mixture consisting of gas and liquid bubbles on the sides. And, since jets of liquid from the choking holes fall directly into the blow-off zone, the cavitation zone is located in the degassing zone.

When flowing around any body, a region of low pressure is formed. In some cases, the pressure drop is sufficient for the effect of cavitation. This phenomenon is especially pronounced when the fluid flows through the diffuser nozzles. To increase the effect of cavitation, it is advisable to perform profiles of choking holes in accordance with the profile of the diffuser nozzle, because this profile assumes the presence of a cavitation zone.

4. Lowering external pressure.

Since the flow of the working fluid after the choking holes enters the air, which has a lower pressure than the pressure of the fluid in the discharge pipes, this creates additional conditions for the occurrence of cavitation. In addition, a reduced pressure in the degassing zone is created due to the flow of air blowing off the separated gases.

5. The pressure upon cavitation does not always equal the saturated vapor pressure. This is due to the presence of a kind of nuclei in which cavitation bubbles nucleate and grow. Such nuclei can be microscopic gas bubbles, solid impurities (dust), etc. Cavitation occurs earlier, the more undissolved air in the liquid, the bubbles of which serve as active centers of cavitation. The occurrence of cavitation is greatly facilitated by the presence of air bubbles in the liquid, as well as dissolved gases.

According to the conditions of the problem being solved, dissolved gases are contained in the working fluid, which ensures the formation of cavitation bubbles at a higher pressure. In addition, pre-aeration supplies the working fluid with germinal nuclei, which facilitates this process and makes it possible for the cavitation effect to occur at lower pressure drops in the flow.

6. With increasing temperature of the liquid.

The higher the temperature of the liquid, the higher the pressure begins to form cavitation bubbles.

In our case, this phenomenon is taken into account when using the claimed method and device for cooling the working fluid.

Blowing off the evolved gases - the final stage of degassing the liquid is carried out by a stream of air with simultaneous mechanical spraying of the liquid as a result of the impact of the jet against the wall, providing separation and removal of dissolved gases.

In the proposed device, the technical result is achieved by preliminary aeration and the use of choking holes (3), which increase the pressure in front of them and increase the flow rate after them by reducing the cross section. When the fluid passes through the choking hole, it instantly compresses with an increase in local pressure and subsequent expansion in the stream with a decrease in pressure and the formation of a cavitation zone. Immediately after the cut of the choking holes, wave-like oscillations of the jet appear, leading to its decay. With increasing speed, aerodynamic forces begin to act on the jet, accelerating the decay of the jet and leading to additional fragmentation of the fluid particles

The jets of liquid with high speed hit the wall of the degassing chamber (4). In this case, mechanical spraying of the liquid occurs with an increase in the surface area of the water-air interface and a sharp decrease in pressure, which causes an additional cavitation effect.

The air flow passing through the degassing chamber (4) provides a blow-off of the released gases.

This sequence of application of physical effects significantly increases the efficiency of cleaning liquids from dissolved gases, because preliminary aeration allows for the supersaturation of the liquid with air, which contributes to the displacement of dissolved gases and the formation of cavitation bubbles. The increase in the interface between the water-air media facilitates the release of gases in the liquid. Since gases are released into the air stream, they are effectively blown off, which prevents their secondary dissolution.

When using the device, the saturation of the treated water with oxygen in the air is performed in an enhanced mode, the oxidation of pollutants contained in the water, such as iron, hydrogen sulfide, etc. is significantly accelerated, the surface area of the water-air interface increases extremely, which provides intensive blowing and oxidation of pollutants, water deferrization occurs without the use of reagents. During the operation of the device, the treated water is activated, it is possible to carry out enhanced mixing of liquid and colloidal reagents, provides increased heat transfer between the flows of the working fluid and air, and high efficiency is achieved. The device has small dimensions and low cost. Its advantages are ease of installation and commissioning, maintenance does not require high qualifications, due to the absence of high pressures, the operation safety is increased.

The method of purifying water from dissolved gases using a device for its implementation was carried out according to examples 1, 2.

Example 1. Tests of the method of water purification were performed with drinking water from an underground water supply source with a high content of radon. The experiment was carried out as follows. Water from an artesian well was pumped to an aeration unit, in which aeration was carried out using a compressor. Then, aerated water flowed through the discharge pipes to the choking holes. The resulting stream of drinking water was broken on the walls of the degassing chamber. A fan created a stream of air passing through the air pipes and the working area of the degassing chamber. Since radon is heavier than air, a water seal was installed to prevent radon from entering the stream of purified water. The degree of wastewater treatment from radon was 99.67%.

Example 2. Tests were carried out with high ammonia wastewater. Water was pumped through the ejector, through which air entered the water stream, into the discharge pipes, and then to the choking holes. The resulting stream of wastewater was broken on the walls of the degassing chamber. A fan created an air flow passing through the air nozzles and the working area of the degassing chamber, in which a water seal was installed. As a result of treatment, the concentration of ammonia in wastewater decreased by 5022 mg / l (66.2%).

The table shows the results of water purification carried out according to examples 1-2

Name of ingredient Concentration before purification Concentrations after cleaning Radon 173.8 Bq / l 0.57 Bq / L Ammonia 7587 mg / l 2565 mg / l

From the analysis of the data of the table it follows that the application of the method of degassing liquids, consisting in sequential aeration, cavitation, increasing the surface area of the interface between water-air by spraying and blowing using a device for its implementation significantly increases the cleaning efficiency, allows cleaning liquids with a high content gases. The inventive method and device have low implementation costs, are easy to use, can effectively clean large volumes of liquid with a high content of dissolved gases. The device is simple and provides a reduction in labor intensity and an increase in the quality of liquid purification from gas inclusions. In addition, since the device is actively mixing the working fluid, it can be used as a chemical reactor by introducing liquid chemicals or colloidal compositions, in particular for changing the pH level.

Claims (3)

1. A method of degassing a liquid, including hydrodynamic cavitation, characterized in that the chamber aerates the liquid in a stream, during which the liquid being treated is saturated with air and cavitation nuclei are created, then hydrodynamic cavitation is carried out by reducing the pressure in the liquid stream to a value equal to the pressure saturated vapors of this liquid at a given temperature or pressure at which the release of dissolved gases from it begins (gas cavitation) by increasing the rate current in the jets, Incoming working fluid in the reduced pressure zone, the pressure increase of the working fluid flowing to the low pressure zone, expanding the flow after its contraction, creating cavitation bubbles of undissolved foci air aspirated into the liquid during the pre-aeration; after which they carry out a blow-off of the released gases by an air stream with simultaneous mechanical spraying of the liquid as a result of the impact of the jet against the wall, which ensures the separation and removal of dissolved gases. 2. A device for implementing the method according to claim 1, comprising a chamber (4), characterized in that the chamber (4) is equipped with an aerator (1) forcing air into the fluid stream; discharge nozzles (2), in which the pressure increases, and choking holes (3), ensuring the formation of jets; air nozzles (6) for supplying air and exhausting evolved gases, made from opposite sides of the chamber (4); in this case, the air supply pipe (6) is equipped with a fan (5) that creates a stream of air passing through the air pipes (6) and the working area of the degassing chamber (4), and at least one water seal (7). 3. The device according to p. 2, characterized in that the cross-sectional profiles of the choking holes correspond to the cross-sectional profile of the diffuser nozzle.

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