PARTICULATE MATTER CONTROL EQUIPMENTS

VATSALYA REDDI.K

CE13M066

Objectives of control equipment Prevention of nuisance Prevention of physical damage to

property Elimination of health hazards to plant

and personnel Recovery of valuable waste product Minimization of economic losses Improvement of product quality

Mechanisms are: Gravitational settling Centrifugal impaction Inertial impaction Direct interception Diffusion and The electrostatic attraction

Types of particulate controlequipments Gravity Setting chamber

Cyclone separators

Fabric filters

Electrostatic precipitators and

Scrubbers

Gravity Settling chamber Remove large and abrasive particles

greater than 50 μ Uses the principle of gravity to settle

the particulate matter Gas velocity is reduced so as to allow

the particulate matter to settle Gas velocity of less than 0.3 m/s will

produce good results

Advantages Low initial cost Simple construction Low maintenance cost Dry and continuous disposal of

collected solids Can be constructed of any material Temperature and pressure limitations

are imposed by type of material used

Disadvantages

• Large space requirement• Only comparatively large particles can be

collected

Applications• Used as pre-cleaners.• Used in food and metallurgical industries • Used widely for removal of large solid

particulates from draft furnace, kilns.

Cyclone separators Use centrifugal forces for removing

the fine particles Also known as centrifugal or

inertial separators Remove 10 to 50 μm particle size

Advantages Low initial cost and maintenance

requirements Simple in construction and operation Requires less area Continuous disposal of solid particulate

matter, Use of any material in their construction

that can withstand the temperature and pressure requirements

Disadvantages

Low collection efficiency for particles below 5 – 10 μ in diameter

Severe abrasion problems can occur during the striking of particles on

the walls of the cyclone, and Decrease in efficiency at low

particulate concentration.

Applications Cement manufacture, food and

beverage, mineral processing and textile industries.

Rock crushing, ore handling and sand conditioning in industries.

To recover catalyst dusts in the petroleum industry.

To reduce the fly ash emissions

Electrostatic precipitators Use electrostatic force Remove the particles less than 5

micron in diameter Designed to trap and remove dust

particles from the exhaust gas stream

Advantages High collection efficiency. Particles as small as 0.1 micron can be

removed. Low maintenance and operating cost. Low pressure drop (0.25-1.25 cm of water). Treatment time is negligible (0.1-10s). Cleaning is easy by removing the units of

precipitator from operation. No limit to solid, liquid or corrosive chemical

usage.

Disadvantages

High initial cost. Space requirement is more because of the

large size of the equipment. Possible explosion hazards during collection

of combustible gases or particulate. Precautions are necessary to maintain

safety during operation. The negatively charged electrodes during

gas ionization produce the ozone

Applications Cement factories Pulp and paper mills Steel Plants Non-ferrous metals industry Chemical Industry Petroleum Industry Carbon Black industry Electric Power Industry

Scrubbers Remove particulate matter by contacting

the dirty gas stream with liquid drops Water is used as the scrubbing fluid Flue gas made to push up against a

down falling water current Dust is agglomerated with water and

then separated from the gas together with the water.

Advantages Low initial cost High collection efficiency of small

particles Applicable at high temperature

installations Remove both particulate and gases No particle reentrainment

Disadvantages High power consumption for higher

efficiency Moderate to high maintenance

costs owing to abrasion and corrosion

Wet disposal of collected material

Applications Useful in the case of a hot gas that must be

cooled for some reason. If the particulate matter is combustible or if

any flammable gas is present, even in trace amounts, in the bulk gas phase, a scrubber is preferred to an electrostatic precipitator

Used when there are waste water treatment systems available on the site, with adequate reserve capacity to handle the liquid effluent.

Fabric Filters Well known and accepted method for

separating dry particles from a gas stream Most of the particles are captured by inertial

impaction, interception, Brownian diffusion, and sieving on already collected particles that have formed a dust layer on the bags.

Consists of numerous vertical bags 120-400 mm dia and 2-10 m long.

Remove particles up to 1 μm. Its efficiency up to 99%.

Advantages

Higher collection efficiency for smaller than 10 μm particle size.

Performance decrease becomes visible, giving prewarning.

Normal power consumption.

Disadvantages Not used when the gas stream

generated by the process equipment includes corrosive materials that could chemically attack the filter media

Not used when there are sticky or wet particles in the gas stream

High temp. gases need to be cooled. High maintenance and fabric

replacement cost. Large size equipment.

Application Metallurgical industry Foundries Cement industry Chalk and lime Brick works Ceramic industry Flour mills