If special measures are not taken to remove mechanical waste and dusty air from the working area of ​​the woodworking machine, the surrounding space soon after the start of work becomes unsuitable for a person who is not equipped with by individual means protection, and extremely flammable. Dust collecting (aspiration) installations are intended to clean the atmosphere of the production premises, to make the work of personnel comfortable and safe.

APPLICATION AREA

Autonomous dust-collecting (aspiration) devices are used in industrial premises, equip which centralized system air purification and waste disposal seems impossible or impractical. Such installations are mainly used in areas for the processing of wood and similar materials of small enterprises in the furniture, construction and other industries.

DESIGN FEATURES

Structurally, the scheme for cleaning the mixture of air with chips and sawdust removed from the machining zone creating a vacuum exhaust fan, represents its filtration by passing it through a layer of fabric from which the receiving container is made. The solid component of the mixture separated by the filter is deposited in the lower part of the device, which acts as a waste collector.

A high degree of air purification, reaching 99.9%, frees workers from the need to use individual protective devices(respirators, etc.) and reduce the level of fire danger to the regulatory level.

The design of most modern woodworking machines provides for the possibility of connecting them to a shop aspiration system or to a dust collection unit.

Dust collecting devices are equipped with both one and several filtering units, consisting of fabric bags located one above the other: a filter and an accumulator. Depending on the volume of waste emitted by the equipment, it is possible to select an installation of the appropriate capacity. As a rule, several emission sources can be connected to one unit.

Many models of dust collectors can be used in vacuum cleaner mode when cleaning the production area.

MAIN ADVANTAGES

Dust collecting installations have become an indispensable element in the organization of woodworking production. Without such devices, it is impossible to perform the installed sanitary standards requirements for working conditions and ensure compliance with fire safety standards.

Aspiration is a process of rooms with high dust content. Such areas are equipped with special filtration equipment. In particular, are used. The premises of various enterprises are equipped with such equipment: from factories for the industrial production of bricks to grain processing plants. Let us further consider what are dust collecting installations (UVP).

Classification features

Dust collecting (UVP) is a device designed for air filtration. The separation of impurities is carried out in special filters.

Depending on the mechanism of action, these elements are divided into:

1. Gravitational.
2. Wet.
3. Electrical.
4. Oil.
5. Inertial.
6. Porous.
7. Combined.
8. Acoustic.
9. Cloth, etc.

Main types of equipment

Depending on the degree of filtration, installations can be:

1. Rough cleaning. The efficiency of particle retention in such equipment is 40-70%. Such units include large-sized cyclones, sedimentation chambers.
2. Medium cleaning. They provide 70-90% particle retention. This category includes louvre, rotary units, cyclones, etc.
3. Fine cleaning. In them, the particle retention rate can reach 90-99.9%. This group includes hose, electric, roll, cell, foam units, etc.

Depending on the areas of application, the devices are divided into 2 categories. The first includes units used to filter ventilation and industrial emissions into the atmosphere, the second - devices designed to clean the flowing streams, as well as air masses returned to the workshop during recycling. Enterprises can use different dust collection plants at the same time. The price of equipment ranges from 36 to 400 thousand rubles.

Technical and economic indicators

According to them, it is determined how effective it is at a particular enterprise. The key technical and economic indicators include:

1. Dust capacity.
2. hydraulic resistance.
3. Performance.
4. Dust collection efficiency (fractional and total).
5. Filtration cost.
6. Maintenance costs.

Comparative characteristics

The simplest is considered, the mechanism of action of which is based on gravity. As a rule, coarse filtering is carried out in it. Particle collection efficiency is no more than 50%. In this case, elements larger than 50 microns are absorbed. Cyclone is more efficient. In it, filtration is based on the application of centrifugal force. In the process of rotation, particles of substances are thrown to the walls of the unit, and then fall into a special hopper. Purified air, rotating, exits the unit through a pipe. The filtration efficiency of cyclones today is 80-90%.

Currently, such units have a very different design. If it is necessary to clean a large amount of air flow, several devices are combined into groups or battery cyclones are used. They are presented in the form a large number small units installed in one housing and placed on one bunker. The most popular today, however, are wet dust collectors. Due to contact with the liquid medium, the particles are wetted and enlarged, and then removed from the apparatus in the form of sludge. Such units can have a variety of designs. For example, it can be rotocyclones, disintegrators, and so on.

Foam units also belong to the class of wet installations. They supply water to a perforated grate. Filtered air passes through it. A threshold (drain partition) is provided on the grate. It allows you to maintain a certain thickness of the foam layer. This is highly efficient - up to 99%. The unit is able to filter particles larger than 15 microns. The industry produces devices PGP-LTI and PGS-LTI with a capacity of 3-50 thousand m/h.

Scheme

Foam includes:

1. receiving box.
2. Frame.
3. Lattice.
4. Threshold.
5. Drain box.

It has the following structure:

1. Inlet pipe.
2. Sleeve.
3. Suspension.
4. Shaking mechanism.
5. Outlet pipe.
6. Bunker.

The electrofilter consists of:

1. inlet pipe.
2. corona electrode.
3. Filter housings (precipitating electrode).
4. outlet pipe.
5. Bunker.
6. Rectifier.

Mechanism of action

sleeve mouth ventilating dust collector filters air through fabric. It is sewn together in a special way and placed in a sealed case of the device. The air being cleaned is sucked off by the fan from the filter and released into the atmosphere. The bags are periodically cleaned using a backflush shaking mechanism. Filters can be pressure and suction type. For their manufacture, a dense synthetic or natural fabric is used. Efficiency of sleeves - 95-99%. In practice, the most common filters are FTNS, FRM, FVK.

Electric devices are widely used in the purification of industrial and ventilation emissions. The mechanism of their work is based on the following: when gas is passed between two differently charged plates, the air environment is ionized. Ions and dust particles collide, the latter receive electric charges. Under their action, they begin to move to the electrodes of the opposite sign and settle there. The filtration efficiency in such devices is 99.9%. Electrical installations are considered economical in operation. They can filter flows at temperatures up to 450 degrees. However, electrical installations cannot be used to trap explosive particles.

Specificity of aspiration

This process involves not only the removal of dust from the air, but also its additional purification. The system functions in such a way that prevents the accumulation of particles and the creation of "traffic jams". This ensures the uninterrupted operation of personnel and equipment in the room. Taking into account the huge volume of waste at industrial enterprises, it can be concluded that aspiration is becoming even more in demand due to the established health and safety standards for personnel working in hazardous conditions.

This method differs from other methods of cleaning indoor air in that the systems are located at a certain angle. This prevents the formation of stagnant zones and localizes areas of maximum emission of contaminants. As a result, filtering is implemented. The concentration of harmful compounds does not go beyond the permissible limits.

Chip blowers

They are used not only at enterprises of the chemical and metallurgical industries, but also in woodworking, grinding and crushing shops. In such premises, the installation of filtering equipment requires special knowledge, so professionals are invited to install it. The design of an aspiration system begins with an examination of the premises. Based on it, a preliminary calculation of the power and dimensions of the equipment is made. AT furniture production there is a huge amount of fine waste. They must be removed from the workspace without fail. For this, a chip removal system is used. The equipment is considered a type of aspiration apparatus.

The chip blower can remove particles up to 5 microns in diameter. In the equipment cyclone there is a special fan and filtered bags. A separate machine is connected to the chip blower using a flexible duct system made of reinforced or corrugated pipe. The principle of operation is quite simple. The fan sucks in polluted air, which is filtered. Dust particles are collected in a bag. From there they are sent to a special filter for final cleaning. At maximum filling, the bag is removed and cleaned or replaced with a new one. Chip blowers are easy to connect and easy to transport.

Requirements

The devices must function smoothly, reliably, with indicators corresponding to the design or obtained during the adjustment activities and agreed with the developer. Gas treatment plants must be equipped with auxiliary devices and inventory. When using such units, responsible persons maintain documentation. It reflects the main indicators by which the mode of operation of the equipment is characterized. In particular, we are talking about deviation from optimal scheme work, identified malfunctions, failure of individual devices or the entire complex as a whole, etc. All units must be registered with the State Inspectorate for Gas Cleaning. At least once every six months, the units should be inspected to assess the technical condition. This procedure is carried out by a commission appointed by the head of the enterprise.

General Rules for the Operation of Gas Cleaning and Dust Collecting Plants

Not allowed to use technological equipment with the filters turned off. In each case of turning off the cleaning device while the machine is operating, the management of the organization is obliged to notify the State Inspectorate. In this case, it is necessary to obtain an approved emission permit from the supervisory authorities.

When operating dust-collecting installations for gas filtration with a high content of explosive (combustible) elements, it is necessary to carefully ensure that the specified pressure indicators and tightness of structures are maintained, and that devices and communications are properly purged to prevent ignition and explosion.

Dust collecting equipment is widely used in all sectors of the national economy, including food industry enterprises, for dust removal from ventilation and technological emissions into the atmosphere. It is characterized by a wide variety of operating principles and design features. Depending on the method of separating dust from the air stream, dry and wet dust collection equipment is distinguished. Equipment that captures dust in a dry way is divided into four groups: gravity, inertial, filtration and electrical. Wet dust collection equipment is classified into three groups: inertial, filtration and electric. Each of these groups includes different kinds equipment.

The main characteristics of dust collecting equipment include the following: the degree of air purification from dust (cleaning efficiency), productivity, hydraulic resistance, power consumption, cleaning cost, etc.

Cleaning efficiency characterized by the ratio of the mass of dust captured in the apparatus to the mass of dust entering the apparatus, and is expressed as a percentage or in fractions of a unit.

However, the calculation of the cleaning efficiency (η) is carried out not by the mass of dust, but by the dust concentrations in the air before and after cleaning (C in and C out, mg/m 3), respectively:

With multi-stage cleaning used for more complete dedusting of air, the total efficiency is determined by the formula:

where η 1 , η 2 …η n is the cleaning efficiency of each of the devices (in fractions of a unit).

Cleaning efficiency is the most important characteristic of a dust separator. It is guided by when choosing dust-collecting equipment in accordance with the permissible residual dust content in the purified air.

The performance of the equipment is characterized by the amount of air that is cleaned in one hour. The hydraulic resistance is also important, since the required fan pressure and, consequently, the power consumption depend on its value, which, with a single-stage cleaning, ranges from 0.035 to 1 kWh per 1000 m 3 of air.

Rice. 20 Cyclone

When choosing a dust separator, in addition to cleaning efficiency, dust dispersion, physical and chemical properties, explosion hazard, hygroscopicity, tendency to coagulate, etc., as well as the value of dust, the need to preserve and use it, are also taken into account.

Of the variety of designs of dust collectors, the most widely used in the food industry are cyclones and bag filters.

Cyclone devices are included in the group of inertial equipment, in which the deposition of dust from the air flow is carried out under the action of centrifugal force.

Cyclones are widely used for cleaning dust from ventilation and technological emissions, which is explained by the simplicity of the device, reliability in operation, and relatively low capital and operating costs.

Cyclone(Fig. 20) consists of cylindrical and conical parts. Dusty air enters the body of the cyclone 1 through the nozzle 2 tangentially to the inner surface of the body usually at a speed of at least 20 m/s and then moves in a spiral in the annular space between the body and the exhaust pipe 3. Under the action of centrifugal force arising from the rotational movement of the flow , dust particles are thrown to the walls of the cyclone and descend into the lower part of the apparatus, falling into the hopper 4. The air flow, continuing its movement, enters the exhaust pipe and exits the cyclone.

The value of the centrifugal force R c acting on a dust particle in a cyclone is described by the following equation:

where V is the speed of the dust-air flow in the cyclone, m/s;

R is the distance from the axis of the cyclone to the particle, m;

m is the mass of the particle, kg.

It follows from this formula that the cleaning efficiency depends on the diameter of the cyclone, increasing with its decrease. Therefore, with significant volumes of air to be cleaned, it is more expedient, instead of installing one large-diameter cyclone, to use a group installation of cyclones of smaller diameter, structurally combined into one housing and having a common supply and removal of the dust-air mixture.

In cyclones, dust particles larger than 10 microns in size are quite effectively captured. Fine fractions are carried away by the air flow, therefore, two- or three-stage cleaning is used to trap fine dust particles, installing bag filters or wet dust collectors after cyclones.

In industry, a large number of different types of cyclones are used, which differ in shape, method of supplying air to the cyclone, productivity, cleaning efficiency, etc.

In the food industry, cyclones NIIOGAZ, BTs, UTs, OTI, SIOT, TsOL, VTsNIIOT, RISI, etc. are used.

NIIOGAZ cyclones (TsN-11 and TsN-15) are approved as unified cyclone type dust collectors. The numbers 11 and 15 correspond to the angle at which the air supply pipe is connected to the cyclone body. Cyclones TsN-11 and TsN-15 are used in the starch and tea industries, grain processing plants, sunflower seed processing plants, etc. In addition, cyclones of this type are used to capture dry dust from aspiration systems, ash from flue gases boiler houses operating on solid fuels, dust from dryers, etc. Depending on the required performance, they are installed singly or arranged in groups of two, four, six or eight cyclones. Such cyclones are called battery cyclones and are designated as BTs, and when a sluice gate is installed - BTsSh (4BTs, 8BTsSh, etc.). The cleaning efficiency of battery cyclones reaches 97-98% for dust with a particle size of more than 10 microns.

Cyclones UC with a body diameter of up to 850 mm are used at the enterprises of the starch and oil and fat industry for single and battery installations. They differ from cyclones TsN in their developed conical part. Cyclone UC is equipped with a spiral flat inlet volute, which increases the cleaning efficiency, which reaches 99%.

Cyclones TsOL used to purify the air mainly from grain dust. The device is characterized by an elongated cylindrical part and a significant depth of the exhaust pipe. In the conical part of the apparatus, a device is installed to reduce air leakage. The entry speed of the dusty air flow into the cyclone is at least 15-18 m/s. The productivity of cyclones is from 1000 to 18000 m 3 /h, the efficiency of cleaning when capturing coarse dust, typical for elevators, is 90-95%.

Cyclones SIOT completely devoid of a cylindrical part, while the inlet pipe has a triangular section. Cyclones are designed to clean ventilation emissions from dry, non-coalescing and non-fibrous dust. It is possible to use them for trapping lime dust at sugar and starch factories and a number of other enterprises. The cleaning efficiency of SIOT cyclones is 97-98%.

RISS cyclones are designed to capture dust from food production, which have specific properties - fibrous, sticky, hygroscopic, etc. Among these cyclones should be called cyclones with cone-coagulator, adjustable cyclones RTs and RTsP, cyclone with internal recirculation TsVR and etc.

Cyclone with coagulating cone solves the problem of cleaning emissions from fibrous dust. It is used at oil and fat enterprises to trap dust generated during the processing of sunflower and cotton seeds, to trap dust from meal, etc. The cyclone differs from other cyclones with a reverse cone by the presence of an additional element - a cone-coagulator. Thus, the conical part of the cyclone consists of two cones connected by bases. In the cone-coagulator, as a result of increasing the flow rate, fibrous dust particles coagulate, forming stable aggregates, while fine dust is captured by large particles, as a result of which the cleaning efficiency is increased. From the cone-coagulator, the dusty flow passes into the reverse cone. The dust separated from the flow enters the bunker through the sluice gate.

Cyclone efficiency is over 99%. 11 numbers of cyclones have been developed for productivity from 200 to 9000 m 3 /h.

Adjustable cyclone RC has an inverted cone, equipped with a spiral screw apparatus, in which a regulating device is placed. The cyclone is recommended for dust collection with high humidity and oiliness, prone to sticking. In the cyclone of this design, dust coagulation occurs, which prevents the removal of large particles with windage. The inner surface of the cyclone is periodically cleaned of adhering dust using a guide vane.

10 numbers of RC cyclone with capacity from 250 to 4900 m 3 /h have been developed.

Cyclones with internal recirculation (CVR) designed to capture soybean dust and other types of dry non-coalescing fine dust. The TsVR cyclone (Fig. 21) differs from the TsN-15 cyclone, on the basis of which it was developed, in that the exhaust pipe 1 has a slotted hole 2 and a helical guide tape 3. Through the slotted hole, part of the flow passing through the exhaust pipe is directed to cyclone body 4 for re-cleaning. A helical guide tape located on the inner surface of the exhaust pipe is designed to intensify the process of movement of dust particles to the slotted hole. Thanks to the internal recirculation of the air flow, the cleaning efficiency is increased, which is 98-99%. 9 numbers of cyclone TsVR have been developed for productivity from 900 to 4500 m 3 /h.

Rice. 21 Cyclone TsVR

For fine purification of ventilation emissions from dust and gaseous impurities, filtration dust collectors.

Dust collection in filtration cleaning devices is due to the action of inertial, gravitational and electrostatic forces. By appropriate selection of filter material and air purification mode, it is possible to achieve the required degree of purification in filter dust collectors in almost all necessary cases. Depending on the material of the filter layer, filtration dust collectors are divided into fabric and granular.

To clean emissions from dust, fabric filters are most widely used in the food industry, in which fabrics made from natural fibers - cotton and wool - are used as filter materials; fabrics made of synthetic fibers - nitron, lavsan, polypropylene, etc., as well as fiberglass. When dusty air passes through the fabric, dust particles are trapped between the threads and the pile, while the pile must be turned towards the dusty air flow.

Filter fabrics have the following requirements: high cleaning efficiency, sufficient air load (filtration rate), good dust holding capacity, regeneration ability, mechanical strength and abrasion resistance, low hygroscopicity, etc. In addition, additional requirements may be imposed, such as resistance to certain chemicals, high temperatures, etc.

Of the fabric filters, the most common bag filters type FV(Fig. 22), which are used to clean large volumes of air with a significant concentration of dust. They provide fine cleaning of particles with a size of 1 micron or less. Along with cyclones, bag fabric filters are the main dust-collecting equipment in the food industry. They are used in baking, sugar, starch, grain processing, oil and fat and other enterprises. The operation of bag filters is characterized by cyclicity - every 3.5 minutes. regeneration of the sleeve section is provided for 30 seconds. Regeneration is carried out by shaking and back blowing of the sleeves and is carried out section by section. As a result of this treatment, the dust deposited on the inner surface of the fabric falls into the hopper, from which it is removed by an auger.

Rice. 22 Bag filter FV:

1 - sleeves; 2 - filter housing; 3 - inlet pipe; 4 - device for regeneration of sleeves; 5 - branch pipe for removing purified air

Four standard sizes of bag filters are produced: FV-30; FV-40; FV-60; FV-90, where the numbers indicate the surface area of ​​the filter cloth in m 2 . The filter consists of 2-6 sections, each of which has from 36 to 108 sleeves with a diameter of 120 to 300 mm and a length of 2.5 to 5 m.

A significant disadvantage of bag filters is the oiling of the fabric, the formation of a crust during the condensation of water vapor, resulting in a sharp increase in hydraulic resistance. Therefore, when cleaning heated air, it is necessary to provide for thermal insulation of the filter.

Effective air purification from grain and other types of dust is provided by RCI filters, in which the sleeves are made of needle-punched cloth IFPZ-1. RCI filters are characterized by a high degree of purification: with an initial dust content of air up to 15 g/m3, the dust content in the air after purification is 2 mg/m3. Regeneration of the fabric of the sleeves is carried out by automatic pulse blowing of the sleeves with compressed air. The optimal interval between pulses is 10 s. Consumption compressed air for blowing one sleeve is 0.7 m 3. RCI filters can be used in explosive rooms of category B.

To clean the air from fine dust with a particle size of 5 microns or less, wet dust collectors, in which the cleaning efficiency is enhanced by the fact that the dust is absorbed by a water film or a finely atomized liquid. Wet dust collectors can also be used to collect explosive and toxic dusts.

Wet dust collector RISI(Fig. 23), designed for fine cleaning of dusty air, can be installed at the second stage after the cyclone. Detains fine mineral dust left after the first stage of cleaning, for example, after a cyclone in the preparatory department of oil and fat enterprises. The dust collector consists of a cylindrical chamber 1, in the lower part of which there is a conical hopper 2 for sedimentation of sludge. Inside the chamber there is a cone-divider 3 and a cylindrical reflector 4, which is connected to a diffuser 5. The smooth outline of the surface of the cone-divider at its edge ensures that the dusty flow contacts the water surface at a slight angle. Dust particles in the flow are wetted with water and settle to the bottom of the hopper. The dust-free air, having passed the droplet eliminator 6, is removed outside through the branch pipes 7. The sludge formed during the cleaning process is discharged through the branch pipe 8.

Rice. 23 Wet dust collector

The degree of air purification in the RISI dust collector is 99.9%.

Several standard sizes of the RISI wet dust collector have been developed for productivity from 600 to 10,000 m 3 /h.

Velocity Venturi Dust Collector It is applied in a number of branches of the food industry, including at sugar factories. The main part of the installation is the Venturi pipe, where the dust-air flow contacts with finely atomized water. At the subsequent stages of cleaning, scrubbers, cyclones and other devices are used, in which dust particles previously coagulated in the first stage are retained.

The dusty air flow enters the Venturi at a significant speed, which in the neck of the pipe is usually 60-120 m/s. Water supply is carried out with the help of sprayers located around the circumference of the confuser. In the neck of the Venturi pipe, intense turbulence is created, which ensures good mixing of the dusty air flow with finely dispersed water, wetting of dust particles and their coagulation. The air flow containing dust particles coagulated in the Venturi enters the second stage, where the dust is collected. Water consumption is from 10 to 80 liters per 100 m 3 of cleaned air and depends on the type of dust, its concentration, as well as on the design of the cyclone. The efficiency of capturing dust particles with a size of up to 5 microns can reach 99.6%.

Cyclone washer SIOT(Fig. 24) can be used in sugar refineries to collect sugar and lime dust, and as a second stage in a Venturi installation. Dusty air enters through the inlet pipe into the lower part of the apparatus at a speed of 5-20 m/s. Water is supplied to the inlet pipe, distributed by means of a perforated pipe and, under the action of centrifugal force, is thrown onto the walls of the apparatus, forming a water film. Along with the centrifugal force great importance to clean the dust-air mixture, the air is washed with water. Good contact of the cleaned air with water is created due to turbulence and spraying of water in the lower part of the apparatus.

Rice. 24 Cyclone washer SIOT:

1 - body; 2 - branch pipe for air outlet; 3 - perforated water supply pipe; 4 - branch pipe for air inlet; 5 - inspection hatches; 6 - branch pipe for sludge removal

Cyclone with water film CVP It is used to clean the air from any kind of non-cementing dust, including limestone dust in sugar factories, as well as from dust containing fibrous inclusions. In addition, CVP cyclones can be used as dust collectors in Venturi installations. The CVP cyclone consists of a cylindrical body with a conical bottom and an air outlet pipe, in which there is an air volute. Dusty air is supplied through the inlet pipe located in the lower part of the cyclone at a speed of at least 20 m/s. The surface of the walls of the cyclone is irrigated with water using nozzles evenly spaced in the upper part of the apparatus. Nozzles are also located in the inlet pipe and are designed to flush out dust deposits. The water pressure in front of the nozzles is recommended to be maintained at a level of 2.0 - 2.5 kPa. Specific water consumption is 0.1 - 0.3 l/m 3 depending on the capacity of the cyclone and the air velocity at the outlet.

The degree of air purification in the CVP cyclone is 90%, the fractional efficiency of capturing dust particles with a size of 5-10 microns is 95%.

The scope of wet dust collectors is limited by their shortcomings, which include the following: the formation of sludge during the cleaning process, which requires special devices for its processing; removal of moisture into the atmosphere and the formation of deposits in the exhaust air ducts when the air mixture is cooled to the dew point; the need to create circulating systems for supplying water to the dust collector.

Dust collecting plants are a class of equipment for workshops, industrial enterprises or home use. Depending on the power and modification of the installation, they are able to solve various problems, however, their main purpose is to clean the air from solid particles formed during processing. various materials, as well as cleaning small industrial waste (chips, chips, sawdust, dust).

By design and principle of operation, the chip blower resembles a conventional vacuum cleaner. Inside the apparatus, microparticles of dust and dirt, metal and wood shavings are separated and deposited on the filter walls, and the purified air is returned to the working room. At the same time, special filters make it possible to capture even the smallest particles of bulk materials (up to 2 microns), which is impossible to achieve with a conventional vacuum cleaner.

Compared to traditional ventilation systems, the chip blower has a number of advantages.

• The cost of equipment and its installation is much lower.
• Saving thermal energy, as the air circulates indoors.
• The same installation can be used in several places.
• Installation is easy to connect and unpretentious in operation.
• Filters the air and helps keep the workplace clean.

Applications

Devices of this type have a wide range of applications:

• removal of bulk waste at enterprises, in carpentry and locksmith shops, home workshops;
• cleaning of machine tools from dust, sawdust, shavings and other dusting;
• collection of bulk waste in containers;
• air purification in factories and workshops.

They can be used in almost all enterprises, except for those where there is a danger of spraying toxic substances. It is also forbidden to use the machine while sanding wood, as explosive chips are formed.

Equipment types, main differences

The store catalog contains several types of equipment.

Dust collecting units are standard. Equipment for industrial cleaning air from solid particles and dust, not prone to gluing. Also suitable for the collection and disposal of industrial waste. Ventilation dust collectors UVP 1200/7000 are available. The digital designation corresponds to the performance of the device. For example, it can draw in 1,200 m3 of air per hour. The number of duct sleeves and accumulators (from 1 to 4) depends on the capacity of the installation.

JET products are collected in a separate catalog and include the following.

• Air filtration system (). It is used in all industrial premises where air pollution by solid particles occurs.
• Exhaust installation (). This compact model is suitable for installation in the workshop or for field work. The unit is equipped with a 55 liter filter bag, so you don't have to change it too often.
• Exhaust installation cyclone (). Works on the principle of action "cyclone". It was developed as an addition to woodworking machines. Cyclone dust collectors got their name due to the internal air cleaner "cyclone". It uses gravity and centrifugal force to purify the air.
• Chip blower JET (). Suitable for home use and carpentry workshops where there is no large accumulation of waste.
• Hood for woodworking machines (). The unit is equipped with two waste collection bags and two filters, which allows it to be used in conjunction with powerful woodworking machines, including several at the same time.
• Cyclone dust collectors ( , ). Powerful machines designed for industrial use. The design allows filtering out the smallest solid particles up to 2 microns in size. Also, during filtration, the installation allows you to separate dust and chips. The rigid case with the increased level of a noise isolation provides comfort during work in the room. The three-phase motor is quieter than many smaller counterparts. The large waste container is large enough and can be changed in just a few seconds. Large chips can be reused, which is very convenient, since fine dust is collected in a separate bag.

Types of dust collecting installations

Depending on the physical principle of operation, industrial separators are classified into dry mechanical, wet scrubbers, electroprecipitators and bag filters. Figure 3 shows the classification of separators.

Table 3. Classification of separators

Dry mechanical separators

Dry mechanical separators are one of the most widely used dust collectors in industry. This type of apparatus is characterized by simplicity of design and ease of maintenance and repair. However, in the case of a single application, dry mechanical separators have a low final efficiency. Therefore, the combination of a number of separator types or as multi-stage separators is most common.

Dry mechanical separators are classified according to the type of aeromechanical forces involved. There are gravitational, inertial and centrifugal dust settling chambers.

In gravitational dust settling chambers, particles are deposited due to gravitational forces (Fig. 1). The advantages of this type of apparatus are ease of manufacture and operation. But the efficiency values ​​​​of such installations are small, and the space occupied by them is significant. Therefore, this type of dust collectors is rarely used, except for cases in which they are pre-collectors for other separators, i.e. perform the pre-cleaning function.

Rice. 3. Dust settling chamber: a - the simplest chamber; b - chamber with partitions; c - multi-shelf chamber; 1 - body; 2 - bunkers; 3 - partition; 4 - shelf

The dust settling rate of dry mechanical dust collectors is calculated as follows:

where X h- particle settling velocity, m/s; d h - particle diameter, m; mid- particle density, kg/m 3 ; sg- gas density, kg/m 3 ; g- free fall acceleration, m/s 2 ; about h is the drag coefficient of the particle.

The minimum size of dust particles that will be completely deposited under the influence of gravity is found using Stokes' law using the following relationship:

where V G- volumetric flow rate of gases, m 3 /m; m G - dynamic coefficient of viscosity, Pa s; B, L- width and length of the chamber, m.

The next type of dry dust collectors are inertial dust collectors. In these types of devices, dust particles under the influence of inertial force will move in the same direction and, after a sharp turn, fall into the hopper. Unfortunately, the effectiveness of such devices is small. In chambers with a smooth turn, the smallest hydraulic resistance. With particle sizes of 25-30 µm, the degree of particle trapping reaches 65-80%. Figure 2 shows various types of dust collectors.

Rice. 4. Inertial dust collectors: a - with a partition; b - with a smooth turn of the gas flow; in - with an expanding cone; g - with lateral gas supply

One of the commonly used dust collectors are cyclone dust collectors. Cyclone dust collectors are rarely used separately due to low efficiency. Cases of single use of this type of filters are possible with unsatisfactory functionality or reliability of other types of separators. The following requirements are imposed on cyclone dust collectors: optimal separation efficiency with variable production parameters, taking into account the low requirements for maintenance and repair of permanent installations, resistance to abrasive wear, high temperatures, accumulation of adhering dust, ensuring preventive measures regarding flammable dust explosion, small space, etc.

Basic geometric characteristic of this type of apparatus is their diameter. With larger diameters, their throughput decreases. Therefore, cyclones of small diameters (150 - 630 mm) are usually used.

If it is necessary to purify a gas flow with a large throughput, a number of parallel-mounted cyclones with a diameter of 475-2500 mm are used.

To determine the separation efficiency in cyclone separators, the total separation efficiency obtained on the basis of experimental data is calculated. This calculation gives the most accurate result. For more high efficiency, separators with a small diameter are grouped into blocks consisting of 2 to 12 separate cyclones.

The main advantages of cyclone devices are: 1) the absence of moving parts in the device; 2) reliable operation at gas temperatures up to 500 °C; 3) the possibility of capturing abrasive materials while protecting the internal surfaces of cyclones with special coatings; 4) dry dust collection; 5) almost constant hydraulic resistance of the apparatus; 6) successful work at high pressures gases; 7) ease of manufacture; 8) maintaining a high fractional cleaning efficiency with an increase in the dust content of gases. The disadvantages are: 1) high hydraulic resistance: 1250 - 1500 Pa; 2) poor capture of particle size< 5 мкм ; 3) невозможность использования для очистки газов от липких загрязнений.

The main types of cyclones are shown in fig. 3:

Rice. 5. The main types of cyclones (for gas supply): a - spiral; b - tangential; in - helical; g, d - axial (socket)

The efficiency of trapping dust particles in a cyclone separator is directly proportional to the gas velocity to the power of S and inversely proportional to the diameter of the device, also to the power of S.

In practice, cylindrical and conical cyclones are most often used. At the same time, cylindrical cyclones are highly productive, and conical ones are highly efficient. The diameter of cylindrical cyclones is not more than 2000 mm, and the diameter of conical cyclones does not exceed 3000 mm.

The hydraulic resistance of single cyclones is determined by the formula:

where X G- gas velocity in an arbitrary section of the apparatus, relative to which the value is calculated about c, m/s; about c is the drag coefficient, which is determined as follows:

where K 1 - coefficient, respectively, equal to 16 for cyclones with a tangential gas inlet and 7.5 - for cyclones with a rosette inlet; h 1 ,b- dimensions of the inlet pipe, m; D TR- diameter of the exhaust pipe, m.

The drag coefficient for group cyclones is calculated from the relationship below:

where about c- coefficient of hydraulic resistance of a single cyclone; D TR- coefficient taking into account additional pressure losses associated with the arrangement of cyclones in a group (table value).

Another type of dry dust collectors are vortex dust collectors. Their main difference from the previous type is the presence of an auxiliary swirling gas flow. Fresh atmospheric air can be used as a secondary gas flow in vortex dust collectors. When using dusty gases as a secondary gas, the productivity of the device increases by 40 - 65% without a noticeable decrease in the cleaning efficiency. The critical diameter of particles completely captured in the dust collector is determined by the formula 15:

where X G- speed of gases in the free section of the apparatus, m/s; H- height of the dust collecting chamber, m; D up- apparatus diameter, m; D tr- diameter of the supply pipe, m; sch- rotation speed, m/s.

Advantages of vortex dust collectors in comparison with cyclone ones:

• 1) higher efficiency of capturing fine dust;
• 2) absence of abrasive wear of internal heating surfaces;
• 3) the possibility of gas purification at more than high temperatures through the use of cold gas;
• 4) the ability to control the separation process by changing the amount of secondary gas. The disadvantages of this type of dust collectors:
• 1) the need to use an additional blowing device;
• 2) increasing the total volume of gases passing through the separator due to secondary air;
• 3) the great complexity of the apparatus in operation.

Below are the characteristic parameters of dry mechanical dust collectors.

Table 4. Characteristic parameters of dry mechanical dust collectors