Dust Collector: Classification, Principle and Application

With the development of society, environmental protection has been paid more and more attention.

For industries with serious pollution, it is even more important. There are countless factories that have closed down because of environmental protection in recent years.

Today, we will bring you some working principles of dust collectors.

In the future, we will bring you some practical cases of using PLC to control various dust collectors in factories. Don’t miss them if necessary.

Classification and dedusting process of dust collector

1. Classification of dust collector

According to the action mechanism, it can be divided into four categories: mechanical dust collector, electric dust collector, filter dust collector and washing dust collector.

Mechanical dust remover also includes gravity dust remover, inertial force dust remover and centrifugal force dust remover.

According to different installation forms, it can be divided into vertical and horizontal dust collectors.

According to whether there is liquid participation in the dust removal process, it can be divided into dry dust remover without liquid participation and wet dust remover with liquid participation.

2. Main components of dust collector

Inlet of dust collector for introducing dusty gas;

Dust removal space for solid gas separation, or dust removal room;

The dust outlet for removing the separated dust and the relatively clean gas outlet after dust removal.

3. Dust removal process

(1) Capture separation process

① Capture and transition stage: in essence, it is the concentration stage of dust.

The dust evenly mixed or suspended in the carrier medium enters the dust removal space of the dust collector.

Due to the action of external force, the dust is moved to the separation interface. With the dust moving to the separation interface, the concentration increases, making further preparations for solid-gas separation.

② Separation phase:

When the high concentration dust flows to the separation interface, there are two action mechanisms:

First, the ability of the carrier medium to carry dust has gradually reached the limit state.

In the trend of dust suspension and sedimentation, it is mainly sedimentation, and it is separated from the carrier medium through dust sedimentation;

Second, in the high concentration dust flow, the diffusion and agglomeration trend of dust particles is mainly agglomeration, and the particles can agglomerate with each other or agglomerate and adsorb on the medium interface.

(2) Dust removal process

After passing through the separation interface, the separated dust is discharged through the dust outlet.

(3) Exhaust process

The relatively purified air flow after dust removal is discharged from the exhaust port.

Common dust collectors and their principles

1. Bag filter

Bag filter is a filter type dust removal equipment based on filtration principle. It uses organic fiber or inorganic fiber filter cloth to filter out the dust in the gas.

The structure of pulse jet dust cleaning bag filter is composed of upper box, middle box, lower box and control valve.

The bag type dust collector enters the dust containing gas into the middle box from the air inlet and into the cloth bag from outside the bag.

The dust is blocked on the surface outside the filter bag, and the purified air enters the bag, then enters the upper box from the upper part of the cloth bag, and finally is discharged by the exhaust pipe.

Bag filter

In order to prevent the filter bag from being sucked and deflated during filtration, a support frame is set in the filter bag, and the pulse valve controls the pulse to eject high-speed and high-pressure air flow into the filter bag, causing the filter bag to expand and contract sharply, causing shock and vibration.

Part of the dust attached outside the bag falls into the lower ash bag by gravity, and part of it is blown down by the instantaneous air flow from inside to outside and enters the ash hopper.

Finally, it is discharged through the dust discharge valve.

This type of dust collector can clean the ash without stopping the air.

Application Industry: it is mainly used to separate particulate dust and fine dust from industrial waste gas. It is widely used in metallurgy, mining, cement, thermal power plant, building materials, casting, chemical industry, tobacco, asphalt mixer, grain, machining and boiler dust removal.

2. Electrostatic precipitator

Working principle of electrostatic precipitator electrostatic precipitator air purifier uses high-voltage DC electric field to ionize gas molecules in the air, produce a large number of electrons and ions, and move to the two poles under the action of electric field force.

In the process of moving, it encounters dust particles and bacteria in the air flow to charge them. The charged particles move to the polar plate with opposite charges under the action of electric field force. Under the action of electric field, free ions in the air will move to the two poles.

The higher the voltage and electric field intensity, the faster the movement speed of ions.

Dust Collector: Classification, Principle and Application 1

Advantages of electrostatic precipitator:

① High separation efficiency, which can effectively remove particles;

② Large amount of treated gas and low resistance;

③ Suitable for high temperature and corrosive gases;

④ Low operation cost.

Disadvantages:

① High investment cost, huge equipment and large floor area;

② High requirements for equipment manufacturing, installation and maintenance;

③ It is sensitive to the characteristics of dust.

1) Basic types of electrostatic precipitators

Electrostatic precipitator is composed of precipitator body and power supply device.

The dust collector body includes discharge electrode, dust collection electrode, air flow distribution device, ash cleaning mechanism, insulation device, shell and other parts.

① Single zone (stage) electrostatic precipitator

Single zone (stage) electrostatic precipitator

In the single zone dust collector, the charging and dust collection processes of particles are carried out in the same area, that is, the corona electrode and dust collector are in the same area.

② Double zone (stage) electrostatic precipitator

Dust Collector: Classification, Principle and Application 2

In the double zone electrostatic precipitator, particle charging and settling dust collection are carried out in two areas respectively.

A group of electrodes are installed in the first area to charge the dust particles, and another group of electrodes are installed in the second area to settle and collect the dust particles.

It is mostly used in air conditioning system.

3. Mechanical dust collector

Mechanical precipitator is a device that uses mechanical force (gravity, inertia force and centrifugal force) to separate dust particles from gas.

This kind of dust collector mainly includes gravity dust collector, inertial dust collector and cyclone dust collector.

Mechanical precipitator is a device that uses mechanical force (gravity, inertia force and centrifugal force) to separate dust particles from gas.

This kind of dust collector mainly includes gravity dust collector, inertial dust collector and cyclone dust collector.

The mechanical dust removal device is characterized by:

Simple structure, low cost and convenient use and maintenance;

It can handle gas with high particle concentration and large gas volume;

It can adapt to the treatment of high-temperature flue gas;

It is generally used for multi-stage dust removal or not high dust removal efficiency.

1. Gravity dedusting chamber

It is also called gravity sedimentation chamber.

It is a dust removal equipment that uses the different density of dust particles and gas to make the dust particles settle and separate naturally from the air flow through the action of gravity.

It is the simplest dust removal equipment.

Gravity dedusting chamber

2. Inertial precipitator

Inertial precipitator

Main features:

Simple structure and low resistance;

The dust removal efficiency is higher than that of gravity sedimentation chamber, but it still belongs to low efficiency dust collector, which is generally used for primary dust removal or as the front stage dust removal of high-efficiency dust collector;

It is suitable for catching metal or mineral dust with particle size of more than 10 ~ 20µm. It is not suitable for cohesive and fibrous dust because it is easy to be blocked.

4. Wet dust collector

With the explosion of dust, more and more attention has been paid to its explosiveness.

The application of wet dust collector is also more and more.

Dust Collector: Classification, Principle and Application 3

The basic principle of all wet dust collectors is to make droplets contact / combine with relatively small dust particles to produce larger particles that are easy to catch.

In this process, dust particles grow into large particles in several ways.

These methods include the combination of larger droplets of dust particles, which absorb water to increase the mass (or density), or the formation and increase of condensable particles at lower temperatures in the dust collector.

According to its structure, it can be divided into the following types:

1. Gravity spray wet dust remover

Gravity spray scrubber has the characteristics of simple structure, small resistance and easy operation, but with large water consumption, large equipment, large area and low efficiency of dust removal.

Gravity spray wet dust collector, such as spray scrubber.

Spray type washing dust collector

Spray type washing dust collector

2. Cyclone wet dust collector

The cyclone scrubber is suitable for purifying more than 5 μ M dust. When purifying submicron dust, it is often connected in series behind the venturi scrubber as a dehydrator for condensed water droplets. The cyclone is also used to absorb some gaseous pollutants.

Vertical cyclone water film dust collector

Vertical cyclone water film dust collector

3. Self excited wet dust collector

The self-excited dust collector has the advantages of compact structure, small floor area, convenient construction and installation, good load adaptability and low water consumption.

The disadvantage is that the price is expensive and the pressure loss is large.

Self excited wet dust collector

Self excited wet dust collector

4. Packing type wet dust collector

Packed wet dust collector, such as packed tower and turbulent ball tower.

Packed tower

Packed tower

Turbulent ball tower

Turbulent ball tower

5. Foam wet dust remover

Foam wet dust remover, such as foam precipitator and cyclone dust trap.

Dust Collector: Classification, Principle and Application 4

Foam washing dust remover

6. Venturi wet dust collector

Because the venturi scrubber has high dust removal efficiency for fine dust and good cooling effect for high-temperature gas.

Therefore, it is often used for cooling and dust removal of high-temperature flue gas, such as the flue gas of iron making blast furnace and steel-making electric furnace, as well as the purification of various furnace flue gas in nonferrous smelting and chemical production.

Venturi scrubber has the advantages of simple structure, small volume, flexible layout, low investment cost and large pressure loss.

Dust Collector: Classification, Principle and Application 5

Venturi scrubber

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