Mais conteúdo relacionado



  1. Settling chamber or gravity settler. • It is also known as gravity settling chamber, gravity collector, expansion chamber and outfall chamber. • It is generally used in removing larger size partial. • It is generally build in the form of long, horizontal, rectangular chamber with an inlet at one end and outlet at other end. • Flow through the chamber is uniform. • Hopper are used to collect the settled out materials, through drag scrapper. • The dust removal system must be sealed to prevent air leaking into the chember.
  2. Cont… • There are two types of settling chember. (a)The expansion chamber. (b)The multiple-trey chamber. • In the expansion chamber, the velocity of gas stream is reduced as the gas expand in large chamber and this reduced velocity allows larger particle to settled out of gas stream. • In multiple trey chember, a number of thin treys are closely spaced within the chember which allows the gas to flow horizontally between them. • Gas velocity increased as compared to expansion chember, so it is used for collection of smaller particle( less than 15µ)
  3. Advantages • Low capital cost • Very low energy cost • No moving part • Few maintenance requirement • Low operating cost • Excellent reliability • Low pressure drop through device • Dry collection and disposal.
  4. Disadvantages • Relatively low particulate matter collection efficiencies. • Unable to handle sticky materials. • Large physical size. • Treys in multiple trey settling chamber may warp.
  5. Electrostatic precipitator • ESP is a large, industrial emission control unit that utilized electrical energy directly to removed particulate matter. • It is designed to trap and remove dust from all kinds of gases with very high efficiency. • It is generally used in power or electric industry, cement, chemical, metal and paper. • It collects most of the dust and clean gas released to atmosphere through stack. • Precipitator collect 99.9% or more dust from gas stream.
  6. Principle: ESP removes particles from the exhaust gas stream. There are six activities that takes place: • Ionization- Charging of particles. • Migration-Transporting the charged particles to the collecting surfaces. • Collection- Precipitation of the charged particles into the collecting surfaces. • Charge dissipation- Neutralizing the charged particles on the collecting surfaces. • Particle dislodging-Removing the particles from the collecting surface to the hopper. • Particle removal-Conveying the particles from the hopper to a disposal point or return to the process.
  7. Working: • As air enter the ESP, the particle pass through an electrical field that gives charge to the particle. • The charge particles pass through a series of alternately charge collector plate. • Particles are repelled by plates with the same polarity and attracted to plate with opposite polarity. • Dual stage ESP ,includes two parts: charging and collecting sections. • In charging section, the incoming smoke, mist and particulates pass by ionizer wires which imparts positive charge on these. • It is then transfer to collector section which contains secondary electric field with negative charge aluminum plate. • It get attract and removing from air stream.
  8. Advantages • High collection efficiency. • Particle as small as 0.1μm can be removed. • Low maintenance and operating cost. • Cleaning is easy by removing different parts of unit.
  9. Disadvantages • High initial cost. • Space required is more because of large size of equipment. • The poisonous gas like ozone is produced during ionization.
  10. Bag filter • It is the most common type of fabric collector consist of tabular bags. • A bag house filter consist of numerous bags 120-140mm dai and 2-10m long. • They are suspended with open ends attached to a manifold and the hopper at bottom for collection of the dust. • The gas entering through the inlet pipe strikes a baffle plate, which causes larger particle to fall into hopper due to gravity. • The carrier gas flows upward through fabric bag leaving particulate matter as a cake inside the bags. • Initially efficiency is low but after the formation of cake it get increased about 99%.
  11. • The cake usually formed in a minute or sometimes even seconds. • The accumulation of dust increases the air resistance of the filter and therefore filter bags have to be periodically cleaned. • It can be cleaned by rapping, shaking or vibration or reverse air flow, causing the filter cake to be loosened and fall into the hopper.
  12. Advantages • High collection efficiency for all particle size specially particle smaller than 10µ. • Simple construction and operation. • Collection and disposal of particulate in dry form. • Nominal power consumption. • Low pressure drop.
  13. Disadvantages • Large size of equipment. • High temperature in between 250-3000c. • High maintenance and operation cost.
  14. Cyclone • It is defined as a structure without moving parts in which velocity of an inlet gas stream is transported into vortex from which centrifugal force drive suspended particle on the wall of cyclone body. • It consist of vertically placed cylinder with inverted cone attached to the base. • The particulate gas stream enter through inlet. The outlet pipe for purified gas is at the top and dust particulates are collected at bottom of storage hopper.
  15. Working: • The gas path generally follows a double-vortex. • At the starting the gas spirals downwards at the outer periphery of cylindrical portion continues through conical portion and reaches the bottom. • The gas stream then moves upward in narrow inner spiral and leaves through the outlet pipe. • Due to rapid spiral movement of gas, the dispersion are projected towards the wall by centrifugal force and drop by gravity to the bottom and collected in hopper. • It is used for collection of wide range of size and concentration.
  16. Application: • It is used for control of gas borne particulate in industrial operation as cement manufacture, paper industry. • Cyclone are also used to separate dust in disintegration, such as rock crushing, sand conditioning in industries. • It is also used in recovery of catalyst dust in petroleum industry and reduction in fly ash emission.
  17. Advantages • Low initial cost • Simple construction and operation • Low pressure drop • Low maintenance requirement • It has no moving parts. • They can be constructed of any material which will meet the temperature.
  18. Disadvantages • Low collection efficiency for particles below 5-10μ in diameter. • Equipment is subjected to serve abrasive deterioration. • Decreasing collection efficiencies for decreasing concentration in the gas stream.