Dust collector
Dust is the deposition of finely divided solid impurities from a gas.
Basics
As a pioneer of the Industrial Dust applies the Lübeck Wilhelm Beth.
Especially in large combustion and industrial installations considerable amounts of dust are released, which may be released only after passing through a dust in the exhaust air. A dust removal system is a technical device to clean dust-laden exhaust air or exhaust air streams. Such systems are used primarily in cement plants, power plants, foundries, steel works, lime works and the chemical industry. The industrial dusts are very diverse and usually have a particle size between 0.1 to 1000 microns.
The use of different filter types and deposition depends on the composition of the dusts, the concentration of the available space and dimensioning. A measure of the quality of a Entstaubungsverfahrens is the degree of separation. Decisive for good coverage of pollutants at the source is the aspiration and the proper placement of the detection and extraction equipment. The dust collection is more efficient the closer to the intake ports are located in close proximity to the source of dust, as the face velocity decreases with increasing distance from the dust source. In the industrial emission and particle deposition in increasingly filtering separators are used.
Entstaubungsarten
- Mechanical dust - eg by centrifugal or gravity
- Wet dust - eg by a rotary scrubber
- Filtrationsentstaubung or dry dedusting system - for example, through a bag filter battery
- Elektroentstaubung - eg by a plate ESP
Mechanical dust
The mechanical removal of dust from gases is based on the deposition of the dust particles by the gravity, inertial force or the centrifugal force.
Gravity: gravity separator such as case chambers work on the principle of gravity. They are used mainly in the dust of larger particles (0.02 mm). One can distinguish between cross-flow, counter-current, deflection and Ringspaltabscheidern. The principle of gravity indicates that the particles fall down due to gravity. Depending on the size and surface of the dust particles varies the rate of descent. The dust-laden air enters the top or side into the trap chamber. By increasing the volume in the trap chamber, the air velocity and coarse dust reduced sits down because of gravity downwards. The purified air flows back from the side or top of the case chamber. Gravity are suitable for separation of coarse dust.
Impingement separator: inertial separator based on the principle of inertia. The dust-laden air enters the side or from above in the inertial separator and collided with an obstacle. Coarse particles can not follow the deflection of the air stream and settle out. The purified air flows back from the side or top of the case chamber. Impingement separators are suitable for separation of coarse dust.
Cyclone: The most famous is the centrifugal cyclone separator. Cyclones usually have a diameter of from 0.02 to 5 meters, and can be used at temperatures up to 900 ° C. Centrifugal separators operate on the principle of centrifugal force. This means that particles are anxious to maintain their direction. The dust-laden air enters tangentially into the cylindrical cyclone. The centrifugal force urges the particles from the outer wall and can therefore be deposited by the funnel-shaped form of the bottom of the cyclone. Due to the downward displacement increases the speed of the airflow and creates an ascending upward air swirl in the center of the cyclone. The cleaned air flows up and out from the cyclone. Centrifugal separators are suitable for separation of coarse dust.
Wet dust
In the wet dust, the dust particles are brought in contact with a washing liquid, or bound to it and removed from the gas stream. In Nassentstaubern there are different variants such as jet scrubbers, vortex scrubbers, venturi scrubber or rotary atomisers. Wet scrubbers require a lot of energy, but also particles can be deposited from a size about 1 micron.
Filtering Separators
In fabric filters the dust laden gas impinges on a permeable porous layer (filter agent) which retains the dust and the gas stream passes. Filtering separators can be used as end separator, as they achieve a high separation efficiency of usually over 98%. The filters keep the dust either by depth filtration inside the computer or on the surface, where a filter cake is formed which is removed by a cleanable again.
Cleanable fabric filter: If the flow through the filter fabric by the flue gas, the dust particles stick to the upstream side. This results in a filter cake, which makes it possible to obtain a high separation efficiency. Rhythmic intervals, the filter cake is removed. Fabric filters are preferably used in the purification of fine dusts.
Cartridge Filter: Cartridge filters contain star-shaped folded filter papers for dust separation. The filter medium is usually provided by pleated paper, polyester or Polypropylenvlise. This principle can be large filter surfaces focus on small space; the result is a very compact design that makes it possible to build small filter units with large filter surfaces. Cartridge filters are therefore often used as a compact filter and preferably in the purification of fine dusts. Are cartridge filters are preferably used for the purification of small amounts of gas use. However, if large amounts of air are cleaned, cartridge filters can also be implemented in multi-chamber construction. Wherein flow through the filter fabric, the dust particles adhere to the upstream side. This results in a filter cake, which makes it possible to obtain a high separation efficiency. The regeneration takes place by means of a Abreinigungsverfahrens such as the low pressure purge or Druckstoßabreinigung.
Bag Filter The bag filter at a filtration is usually carried out in a cylindrical tube, the tissue in the flow of contaminated air to retain the dust. The tubes can have a length up to 12 m. Tubular filters are preferred, with temperatures used for the purification of air, up to 250 ° C. Wherein flow through the filter bag, the dust particles adhere to the upstream side. This results in a filter cake, which makes it possible to obtain a high separation efficiency. This filter cake is cleaned automatically by compressed air pulses or purge air. Bag filters are preferably used at a high dust loading and deposition of fine and coarse dust.
Electric separator
- The principle of Elektroentstaubung based on the fact that electrically charged dust particles are attracted to and bound in an electric field of an oppositely charged electrode.
Electrostatic precipitators use the effect of electric fields to attract electrically charged dust particles of an oppositely charged electrode and binding. The deposited particles are deposited on the collecting electrodes and can also be transported by Abklopfeinrichtungen or by a liquid film. Electrostatic precipitators have a good separation and hardly any influence of Rohgasstaubgehalten. With these particles can be deposited from a size greater than 1 micron. ESPs are used mainly for processes with high exhaust temperature and large gas volumes ( large combustion plants, cement kilns, iron ore sintering ).