RU2372972C1 - Device for dust and gas catching from smoke and aggressive gases - Google Patents

Abstract

FIELD: ecology.

SUBSTANCE: invention relates to field of control of atmospheric air pollution. Device contains cylindrical body with input and output branch pipes, bunkers for withdrawal of sedimentary particles and sludge, device for compressed air supply. Devices for compressed air supply placed in tangential manner to body are installed at angle 20°÷25° to the vertical in direction of purified gas flow movement and are made in form of hydrodynamic accelerators, which have axial branch pipe for supply of compressed air, tangential branch pipe for liquid supply, and output opening of accelerator made in form of Laval nozzle. Device is equipped with regulators of liquid and compressed air consumption, as well as with reservoir for chemical solutions.

EFFECT: increase of smoke and aggressive gas purification efficiency by complex carrying out of dust and gas catching in devices with large diametre, and consequently larger productivity, with simultaneous reduction of energy consumption, reduction of atmosphere pollution degree.

2 cl, 5 dwg

Description

The invention relates to the field of combating air pollution, and in particular to devices for dust and gas collection.

It is known that during the "gravitational deposition" of solid particles from a horizontal gas stream carried out in dust-collecting chambers (M.I. Birger, A.Yu. Waldberg, B.I. Myagkov and others. A guide to dust and ash collection. Under general. Edited by A.A. Rusanov. - 2nd ed. - M .: Energoatomizdat, 1983. p. 52), the pollutant particles are released from the stream mainly under the influence of gravity, as well as due to impact (collision) with special obstacles in the form of vertical liners screens. The main advantage of these devices is the simplicity of design, which determines the possibility of their manufacture at non-specialized enterprises, as well as the minimum aerodynamic drag in the gas path (less than 100-200 Pa) of the known structures.

However, the efficiency of gas purification, achievable in "gravity" apparatus, is often insufficient (up to 50%). To obtain an acceptable cleaning efficiency, it is necessary that the particles are in the chamber for the longest possible time. Therefore, dust precipitation chambers, designed for the deposition of even relatively large particles (more than 100 microns), are bulky structures and are mainly used as the first stage of gas purification before more efficient dust and ash collectors. A significant disadvantage of the device is the inability to clean at high temperature and high humidity of gases. They do not allow solving the issues of cleaning flue gases from chemical impurities.

It is known that during “dry inertial cleaning” of gases, carried out by imparting a swirling or rotational movement to the dusty flow within the boundaries of a dust precipitation apparatus (cyclone) with vertical cylindrical walls (M.I. Birger, A.Yu. Waldberg, B.I. Myagkov and Dust and Ash Collection Manual, edited by A. A. Rusanov, 2nd ed., Moscow: Energoatomizdat, 1983. p. 61), dusty gases are fed into the cyclone through a tangential nozzle and made inside cylindrical and conical parts of the apparatus complex rotational-translational The motion. Particles suspended in the flow inside the cyclone are affected by the inertia force (centrifugal force), which displaces them from curved streamlines along tangent lines directed at an angle downward to the body wall. Particles in contact with the inner surface of the wall, under the action of gravity, inertia and a falling gas stream, slide down and fall into the dust collector (hopper).

Since the inertial force is proportional to the mass, large particles are almost completely released from the stream. The degree of purification of aerosols with particle sizes above 50 microns is in the range of 80-95%.

The main disadvantage of the known designs of cyclones is the low capture efficiency of particles smaller than 5 microns. Such particles do not reach the walls of the apparatus, continue to move along curved streamlines and are carried out of the cyclone by a gas stream. Another disadvantage is the formation of a central vortex output stream, which captures a significant amount of particles settled in the cyclone hopper. An increase in the effect of particle deposition due to a decrease in the diameter of the cyclone and an increase in the flow rate is possible up to certain limits limited by technical and economic factors. These include an increase in energy costs (increase in aerodynamic drag up to 1000-2000 Pa), deterioration in cleaning due to intensive re-capture of the separated particles, abrasive wear, increase in metal consumption and others.

It is also known that with "wet dust collection" the cleaning mechanism is based on the contact of a dusty gas stream with a film or liquid droplets that trap suspended particles and carry them away from the apparatus in the form of sludge (M.I. Birger, A.Yu. Waldberg, B. I. Myagkov et al. Handbook on dust and ash collection, edited by A.A. Rusanov, 2nd ed., Moscow: Energoatomizdat, 1983. p. 109). "Wet dust collection" is carried out in scrubbers - devices with a body in the form of a vertical column, hollow or with a nozzle into which a swirling stream of purified gas and irrigation liquid are introduced. The rotation of the gas stream is set by means of guide vanes or by the tangential supply of gases to the scrubber body. The irrigation fluid is supplied counter or across the gas stream, it is sprayed most often with the help of hydraulic nozzles or centrifugal mechanical sprays installed in the central part of the apparatus or along its walls.

Most wet dust collectors can be used to capture particles less than 5 microns. The capture efficiency of such particles is 99% and is close to the efficiency of bag and electrostatic precipitators, and the design of hollow apparatuses is characterized by a minimum aerodynamic drag of 220-250 Pa. Scrubbers are also effectively used in cases where dry devices are usually not used, for example, at high temperature and high humidity of gases, in case of danger of fire and explosions of purified gases. Devices for "wet cleaning" allow you to jointly solve the issues of dust collection and chemical cleaning of flue gases, while the choice of irrigation fluid (absorbent) is determined by the conditions of the absorption process.

The main disadvantage of scrubbers is that with large volumes of cleaned gases and the dimensions of the apparatus, water droplets and dust particles do not have time to reach the walls before the gas stream leaves the apparatus. In order for the entrainment of liquid from the contact zone to be insignificant, the droplet size should be at least 500 μm, and the gas flow velocity should not exceed 0.8 ÷ 1.2 m / s.

Known vortex dust collectors that implement the method of "dry inertial deposition in the auxiliary swirling flow" (Vetoshkin AG Processes and dust cleaning apparatus. Textbook. - Penza: Publishing House of Penza State University, 2005. p. 62). In a vortex dust collector, as in a cyclone, dust separation is based on the use of centrifugal forces. Their main difference from cyclones is the presence of an auxiliary swirling gas flow.

In a nozzle-type vortex dust collector, the dusty gas enters the vertical cylindrical chamber through the lower inlet pipe with a “socket” type blade swirl and a cowl. The flow swirls with a blade swirl and moves upward, being exposed to high-velocity jets of a secondary gas stream (compressed air) emanating from the nozzles. Compressed air nozzles are placed tangentially along the upper part of the cylindrical body in descending spirals at an angle of inclination of 30 ° towards the gas being cleaned.

Under the action of centrifugal force, particles suspended in the flow are discarded to the periphery of the central upward flow, and from there to the zone of action of the oncoming jets from the nozzles. There, dust particles are captured by a spiral stream of secondary air and with it move down into the hopper. In the hopper, dust particles are emitted from the stream, and the cleaned air is again pumped by the compressor to the nozzles.

In vortex dust collectors, a very high cleaning efficiency is achieved for devices based on the use of centrifugal forces. It is 98-99% and above. The cleaning efficiency is slightly affected by the change in load (in the range from 50 to 115%) and the dust content in the gas being cleaned - from 1 to 500 g / m ³ . The device can be used for cleaning gases with temperatures up to 300 ° C, as well as if hot gas is to be cleaned, which must be cooled. In the vortex dust collector there is no wear of the internal walls of the apparatus, which is associated with the peculiarities of its air regime.

The main disadvantage of the known design is a significant aerodynamic drag, comparable to the costs in cyclone apparatuses. This is due to the fact that two counter-directed flows are created in the device’s volume, interacting with each other over a considerable depth of the boundary layer separating them. In addition, the swirling of the central flow is carried out using a swirler, on which a significant part of the pressure developed by the smoke exhauster or fan is lost. The disadvantages of the known design can be considered low productivity, the difficulty of collecting dust with high humidity gases.

The closest in technical essence and the achieved effect is a device for dust and gas collection from flue and aggressive gases according to patent RU 20034633 (class B01D 45/00, 1995), containing a housing with inlet and outlet pipes, hoppers for the removal of deposited particles and sludge, devices for supply of a high-speed stream of air.

The disadvantages of the known device are low productivity, significant resistance to the gas path and the inability to chemically clean and neutralize aggressive flue gases.

The invention is aimed at improving the efficiency of cleaning flue and aggressive gases by conducting dust and gas ash collection in large-diameter apparatuses, and therefore, high productivity, while reducing energy costs by reducing aerodynamic drag on the gas path.

This object is achieved in that in a device for dust and gas collection from flue and aggressive gases, comprising a housing with inlet and outlet pipes, silos for removing precipitated particles and sludge, a device for supplying compressed air, according to the invention, the housing is cylindrical, devices for supplying compressed air are tangentially to the body at an angle of 20-25 ° to the vertical in the direction of flow of the gas to be cleaned and made in the form of hydrodynamic accelerators having an axial nozzle for feeding compressed air, a tangential nozzle for supplying fluid, while the outlet of the accelerator is made in the form of a Laval nozzle.

The task is also achieved by the fact that the device is equipped with regulators of the flow of liquid and compressed air for hydrodynamic accelerators-mixers, as well as a capacity for chemical solutions.

The drawing schematically shows a device for dust and gas collection (figure 1, figure 2). The device includes a cylindrical housing 1 (in the form of a horizontal or vertical dust collecting chamber) (a horizontal housing is shown in Fig. 1), inlet 2 and outlet 3 nozzles for supplying to the chamber and removing flue and aggressive gases from the chamber, bins 4 for collecting dust, a separator 5, non-pressure tank 6 for chemicals, tangentially installed hydrodynamic accelerators 7, flow rate regulators 8 and compressed air 9.

The hydrodynamic accelerator (shown in figure 2) consists of a housing 10 and two nozzles: axial 11 for compressed air and tangential 12 for ejected water. The accelerator outlet is made in the form of a Laval nozzle 13 with a flange 14.

Hydrodynamic accelerators 7 are installed in a cylindrical housing tangentially at an angle of 20-25 ° to the vertical. Deviation from the vertical of 7 high-speed jets flowing from accelerators promotes the creation of a swirling (vortex) flow, inside which a rarefaction (thrust) is formed. The actual speed and stability of the vortex flow is ensured by the elevation angle of the hydrodynamic jet. Deviation of the hydrodynamic stream from the vertical by an angle of less than 20 ° does not allow forming a vacuum, and with an increase in the angle of inclination by more than 25 °, to achieve the task it is necessary to increase the length of the dust chamber.

The device operates as follows. High-temperature flue gases flow through pipe 2 into a dust-collecting cylindrical chamber of large diameter 1, while the flow sharply loses speed and large dust particles fall out of it into the bunkers 4 of the first row. The horizontal gas flow at a speed of 0.8 ÷ 2.5 m / s continues to move into the zone of action of the hydrodynamic accelerators 7 (see section II in figure 1), where cold high-speed flows of compressed air are introduced tangentially into the flue or aggressive gases at an angle of 20 ÷ 25 ° to the vertical. The total flow acquires a translational-rotational motion. In this case, intense inertial forces arise, affecting the dust particles and releasing them from the stream. To increase the efficiency of inertial deposition of fine particles and neutralize gaseous impurities, a metered amount of water or chemical solutions is ejected into a stream of compressed air. The hydrodynamic jet is fed in a satellite along the direction of the gas being cleaned, and additional thrust is created in the body of the cylindrical chamber.

The introduction of chemical reagents through ejection into the auxiliary stream allows the neutralization of organic gas impurities. An additional injection of water helps to condense and change the dew point of the stream, moisturizing and weighting small particles of dust, which significantly increases the cleaning efficiency. In addition, when condensed, water vapor traps carbon dioxide from the products of combustion, the solubility of which increases with decreasing temperature.

Thus, the implementation of dust and gas collection using a satellite auxiliary high-speed stream of compressed air, the use of a large diameter cylindrical body in the hollow apparatus, as well as the possibility of dispersing water or other liquids and chemicals, allows the combination of dry, condensation and wet dust and gas collection, increase the efficiency of cleaning, as well as reduce aerodynamic losses in the gas path.

The design of the device, which consists of a large-diameter cylinder located horizontally or vertically, with hydrodynamic accelerators installed on it (Fig. 2), makes it possible to intensify dust and gas ash collection processes to the level of multi-stage plants.

The implementation of the invention will improve the cleaning efficiency of flue and aggressive gases, will ensure complete capture of dust, ash and gas neutralization in one apparatus within a wide range of dispersion and concentration while reducing energy consumption by reducing aerodynamic drag on the gas path, significantly reduce the degree of air pollution, reduce costs for the construction and maintenance of treatment facilities.

Claims (2)

1. A device for dust and gas collection from flue and aggressive gases, comprising a housing with inlet and outlet pipes, silos for discharging deposited particles and sludge, a device for supplying compressed air, characterized in that the housing is cylindrical, devices for supplying compressed air located tangentially to case, installed at an angle of 20 ÷ 25 ° to the vertical in the direction of flow of the gas to be cleaned and made in the form of hydrodynamic accelerators having an axial nozzle for supplying compressed air, tangent the liquid supply pipe, and the accelerator outlet is made in the form of a Laval nozzle. 2. The device according to claim 1, characterized in that the device is equipped with regulators of the flow of liquid and compressed air, as well as a container for chemical solutions.

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