RU2767611C1 - Method for cleaning the gas stream from mist droplets - Google Patents

Abstract

FIELD: gas purification.

SUBSTANCE: invention relates to the field of technology designed to purify a gas stream from mist droplets contained therein, and can be used to disperse mist in a controlled area. The method consists in advancing the purified gas stream by overpressure through a porous structure with open pores. In the process of advancing the gas flow through a porous structure with open pores, its movement is carried out in a plane intersecting the flow lines of the advanced gas stream.

EFFECT: increase in the efficiency of cleaning the gas stream from the liquid droplets contained in it and, accordingly, an increase in the efficiency of mist dispersion.

1 cl, 1 dwg

Description

The invention relates to the field of technology designed to clean the gas flow from the fog drops contained in it, and can be used to disperse fog in a controlled area (airfields, express roads, open areas for various sports and entertainment events, etc.), where it is necessary to meet the requirements for atmospheric transparency and ensuring the visibility range, as well as in devices for filtering droplet dispersions from gas streams. In addition, the proposed method can also be used to clean gas flows from liquid drops in various technological processes.

A device for separating steam from gases is known, containing a vertical cylindrical body with nozzles for the inlet and outlet of the cooling agent and two gratings on which the tubes are fixed. To enter the gas-vapor mixture, the upper chamber is mounted in the housing, and the lower chamber is mounted to exit the separated condensate and purified gas (A.G. Amelin. Theoretical foundations of fog formation. M .: Chemistry, 1966, p. 164).

In the known device, the gas-vapor mixture passes through the upper chamber through pipes cooled by a refrigerant moving in the annulus. When in contact with the cold surface of the pipes, the gas is cooled and the vapor contained in the gas condenses on this surface. The liquid condensed in the pipes is collected in the lower chamber and flows out of it through the condensate outlet pipe. The gas cleared of condensate exits through the branch pipe of the lower chamber. In the known device, condensation and separation of only that part of the vapors of the gas mixture, which manages to come into contact with the surface of the pipes during the time the mixture is in the pipe, is carried out. The rest of the vapor remains in the composition of the mixture leaving the device. Thus, to increase the degree of purification of the mixture from vapors, an increase in the overall dimensions of the known device is required. In addition, the known device does not provide for cleaning the mixture from aerosols.

Known methods for cleaning a gas stream from the liquid droplets contained in it are used to disperse fogs. Purification is carried out by forming processes of artificial condensation of water vapor in the fog by adding special substances (reagents) to the fog area. The use of mist dispersal agents is extensively presented in the patent literature. (See, for example, patents No. 2357404 RU, No. 2061358 RU, No. 2175185 RU, US No. 2815928). The use of these methods is limited to supercooled fogs (fogs formed in conditions of negative ambient temperatures). Warm fogs are thermodynamically stable, and with the help of reagents it is not possible to initiate artificial condensation processes, the fog does not dissipate.

There are known methods of gas purification from the liquid droplets contained in it by electrical action on it, based on the use of a corona discharge generated by special wires connected to a high-voltage power source, mounted in the area of the alleged fog dispersion, (see, for example, USSR author's certificate No. 71260 , IPC A01G 15/00, published 07/31/1948, US patent No. 3456880, IPC A01G 15/00, published 07/22/1969). The main disadvantage of the described method is the need to deliver corona wires to the area of the proposed air purification from the liquid drops contained in it and the dispersion of fog, which predetermines high resource costs and is not always feasible due to weather conditions. A simpler way to deliver electric charges to the atmosphere is presented in the description of the USSR author's certificate No. 29675, IPC A01P 15/00, published in 1948. The described method contributes to the spread of ionized air, i.e. electrically charged particles into the area of intended impact, thereby accelerating the process of precipitation. The air is purified from the water droplets contained in it. Cloud or fog dissipates.

The closest technical solution to the proposed method is the method described in the RF patent for the invention No. 2376056 RU. This method consists in advancing the formed gas flow to be cleaned through a porous structure with open pores. The known method provides high efficiency air purification from water droplets from the formed gas stream. With the help of air purified from droplets, fog is displaced from the controlled area by the pressure of moving gas. At the same time, in a known way, only those drops are cleaned from the gas flow, which, in the process of flow movement, touch the surfaces of the structural elements of the filter material. Taking into account the low speeds of air mass movement through the pores of the filter material and the small size of the droplets, only an insignificant part of the finely dispersed droplets due to turbulent eddies can fall on the back of the streamlined surface. The theory of inertial settling, see, for example, Vetoshkin A.G. Fundamentals of engineering environmental protection. - M .: Infra-Engineering, 2019. - 452 s, shows that small particles follow to a greater extent along the air flow current lines and do not come into contact with the frontal (front) part of the streamlined body. Natural fog droplets are small, the radius of fog droplets usually ranges from 1 to 30 µm. Most of the droplets have a radius of 5-15 µm at a positive air temperature and 2-5 µm at a negative temperature (https://ru.wikipedia.org/wiki/Tyman). Thus, in the known method, a significant part of the mist drops flow around the structural elements of the porous filter material and go outside into the controlled space. Which reduces the efficiency of the known method. Increasing the separation efficiency of mist droplets by reducing the pore size of the filter material greatly increases the aerodynamic drag of the device. The natural airflow simply flows around it. And the use of forced air flow through the filter material, in which the pore size is reduced, increases energy consumption, which also reduces the efficiency of the known device.

The purpose of the proposed invention is to increase the efficiency of cleaning the gas stream from the liquid droplets contained in it and, accordingly, to increase the efficiency of mist dispersion.

To achieve the stated goal in the known method of cleaning a gas flow from the liquid droplets contained in it, which consists in advancing it with excess pressure through a porous structure with open pores, in the process of advancing the gas flow, the porous structure with open pores is moved in a plane crossing the flow lines of the promoted gas flow

The technical result in the proposed invention is achieved due to the fact that without reducing the area free for the passage of air flow per unit area of the cross-section of the filter material, without reducing the pore size of the filter material, the probability of collision of the structural elements of the filter material with liquid drops contained in the filter material advanced through the filter increases. material gas stream.

The collection efficiency of water droplets can be determined using a known relationship, defined in the literature as the Stokes criterion. See, for example, Vetoshkin A.G. Fundamentals of engineering environmental protection. - M.: Infra-Engineering, 2019. - 452 p.

where λ is the inertial path of a drop in air;

R is the radius of the structural element of the porous material;

ρ is the density of water;

ω ₀ - the speed of movement of the cleaned air flow relative to the structural elements of the porous material;

d is the droplet diameter;

μ - dynamic viscosity of air.

The theory of inertial settling [Vetoshkin A.G. Fundamentals of engineering environmental protection. - M.: Infra-Engineering, 2019. - 452 p.] determines that for small values of the numbers S _tk (for particles of small size and low mass), the particles exactly follow the lines of the current of air movement without touching the frontal (front) part streamlined body. Only an insignificant part of finely dispersed drops due to turbulent eddies can fall on the rear part of the streamlined surface. Thus, to increase the probability of collision of fog droplets with the surface of the structural elements of the grid, and, consequently, to increase the efficiency of droplet separation, it is necessary to increase the Stokes number. In the proposed technical solution, an increase in the Stokes number is ensured by increasing the speed of movement of the structural elements of the porous material relative to the air flow being cleaned, since in the cleaning process, in addition to the speed of movement of the air flow, the speed of movement of the porous structure with open pores is also added.

The proposed method can be implemented as follows.

When protecting an object from fog, in the flow of fog flowing onto the protected object, which must be cleaned of water droplets contained in it, a device is installed containing a porous open-pore structure, which is mounted with the possibility of moving it in a plane, for example, by mounting it in grooves device frame. The porous, open-cell structure can be made using a wide range of filter media available on the market, including metals (from a bundle of randomly laid thin steel wires), polymers (for example, polyurethane foam http://www.rnasvent.ru/tovari/filtromatt/polipropilenrectikulirovanni/ ppi-polinazell-10.html.), ceramic materials, fiberglass, carbon fiber and other materials fixed in the frame. The porosity of the filter material is determined at the design stage of the device, depending on its purpose and requirements for the degree of filtration. The porosity of the material is determined from the conditions for ensuring the free passage of fog through the device due to the dynamic head of the natural wind flow.

The device is installed in such a way that the plane, in which the open-pore porous structure is movably mounted, crosses the jet of the incoming fog stream to be cleaned. To clean the flow of fog from water drops, a mechanism is included that ensures the movement of a porous structure with open pores in the plane of its installation. Any mechanism, such as a vibrator, can be used as such a mechanism for moving the porous open-pore structure. The oncoming fog stream W (see Fig. 1), containing water droplets suspended in the air, under the action of excess pressure formed by the velocity pressure of the jet of the oncoming fog stream to be cleaned, passes through the pores of the filter material of a porous open-pore structure, which is moved in a plane, crossing the moving air stream to be cleaned. To enhance the dynamic pressure of the wind flow, if it is necessary to overcome the increased aerodynamic resistance of the porous open-pore structure, the frame of the device can be made in the form of dynamic reflectors that direct the natural wind flow from the surrounding space to the porous open-pore structure. The size of dynamic reflectors is selected at the design stage and can be no more than 30% of the linear size of the device. Reflectors are installed at an acute angle β to the direction of the wind flow. An increase in the dynamic pressure of the wind flow can also be achieved by using a fan.

Water drops contained in the air stream to be cleaned, passing through the porous structure with open pores, come into contact with the fibers of the filter material crossing its flow lines and are deposited on their surface. As the drops become larger, they are removed from the device under the action of gravitational forces and inertial forces from the movements of the filter material. The stream cleared of drops displaces the fog from the controlled area and ensures the fulfillment of the task of dispersing the fog in the vicinity of the protected object.

When using the proposed method in devices for filtering droplet dispersions from gas streams and for cleaning gas streams from liquid droplets in various technological processes, the implementation of the proposed method is similar. In these purification devices, for the formation of excess pressure, it is sufficient to provide a special technical means for advancing the gas flow (for example, a fan) and connect it to the gas pipeline of the gas to be purified.

The cleaning efficiency of the proposed method is ensured due to the fact that the relative speed between the fog drops and the elements of the moving porous structure with open pores increases, which increases the likelihood of collision of the fog drops with the structural elements of the pores.

On fig. Figure 1 shows an exemplary diagram of a device that allows implementing the proposed method to perform the task of cleaning the air flow from drops and protecting the controlled area from fog flowing onto it. The device includes a porous structure with open pores, made in the form of racks 1 standing opposite each other, between which partitions 2 are installed with bands of filter material 3 fixed in the gap between them δ. Partitions 2 are installed one above the other at an angle α to the horizon.

If necessary, in case of insufficient rigidity, the filter material belts can be framed with a mesh (not shown in Fig. 1). Filter material belts can be made from any filter media available on the market, including metals (from a bundle of randomly laid thin steel wires), polymers (for example, polyurethane foam http://www.masvent.ru/tovari/filtromatt/polipropilenrectikulirovanni/ppi-polinazell -10.html.), ceramic materials, glass fiber, carbon fiber, etc. The porosity of the filter material is determined at the design stage of the device, depending on its purpose and requirements for the degree of filtration. The porosity of the material is determined from the conditions for ensuring the free passage of fog through the device due to the dynamic head of the natural wind flow.

Partitions 2 can be made of any material. The main requirement for partitions is impermeability to the separated liquid. The step of the partitions is selected by experimental selection depending on the porosity of the filter material, its thickness and its permissible waterlogging. With a thickness of the above-mentioned filter material of 25 mm, it is impractical to make a baffle spacing of more than 500 mm. The pores of the lower layers at a flow rate of more than 3 m/s, with a baffle spacing of 500 mm, are clogged with water, drops are carried out by the flow, which indicates a decrease in the efficiency of the device. The angle of inclination of the partitions α to ensure stable runoff of accumulated moisture is at least 3°. To increase the reliability of the separated liquid output from the device, partitions 2 can be installed at an acute angle γ towards one of the racks. The angle of inclination γ must also be at least 3°. At the same time, a groove 4 is made along the edge of the partition to drain the separated liquid.

The open-pore porous structure is mounted in the frame 5 with the possibility of its vertical movement, for example, in the grooves 6 and fixed on the vibrating table 7. The vibrating table 7 can be made similarly to the known schemes of the vibrating tables, see, for example, https://market.strojdom55.ru /oborudovanie/vibrostol-1400h700, including 7 vibrators 9 fixed on a table mounted on elastic supports 8.

If it is necessary to increase the dynamic pressure of the wind flow, the frame 5 can be made in the form of dynamic reflectors that direct the natural wind flow from the space surrounding the porous structure with open pores to pass through its cross section. The size of dynamic reflectors is selected at the design stage and can be no more than 30% of the linear size of the device. Reflectors are installed at an acute angle β to the direction of the wind flow.

The proposed device works as follows.

The proposed device is installed between the oncoming fog stream and the protected object. The vibrators 9 of the vibrating table 7 are switched on. The open-pore porous structure fixed on the vibrating table 7 performs vertical oscillatory movements and moves the filter material belts 3 in a plane crossing the fog flow W advancing on the protected object. by the action of excess pressure formed by the velocity pressure, it passes through the pores of the filter material 3, the fibers of which reciprocate in a plane crossing the moving air flow being cleaned. The water droplets contained in the air stream to be cleaned come into contact with the fibers of the filtering material crossing its flow lines and are deposited on their surface. As the drops grow larger, they, under the action of gravitational forces and inertial forces from the vibrational movements of the filter material, flow down to the partition 2 and are further removed from the device along the groove 4. The stream cleared of drops displaces the fog from the controlled area and ensures the fulfillment of the task of dispersing the fog in the vicinity of the protected object.

The proposed technical solution, thanks to new, previously unknown features, provides an increase in the likelihood of mist droplets colliding with the structural elements of the filter material, which increases the likelihood of their separation from the passing air flow without increasing aerodynamic resistance, which increases the efficiency of the device and allows achieving the goal of the proposed invention.

Claims (1)

A method for cleaning a gas flow from the mist drops contained in it, which consists in advancing it with excess pressure through a porous structure with open pores, characterized in that in the process of advancing the gas flow, the porous structure with open pores is moved in a plane crossing the streamlines of the promoted gas flow.

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