Various types of Equipment Used to control Particulate Matter (Air pollutant)

Various types of Equipment Used to control Particulate Matter (Air pollutant)

1. Settling chamber

2. Cyclone

3. Scrubber

4. Electrostatic precipitator

5. Bag filter

6. Inertial separator

1. Settling Chamber

The settling chamber is the simplest type of equipment used for collection of solid particulates. It consists of a chamber in which the carrier gas velocity is reduced so as to allow the particulates to settle out of the moving stream under the action of gravity.

The most common form is a long box like structure, with an inlet at one end and an outlet at the other, set horizontally, often on the ground. It can be constructed from brick and concrete.

2. cyclones

A cyclone removes particulates by causing the dirty airstream to flow in a spiral path inside a cylindrical chamber. Dirty air enters the chamber from a tangential direction at the outer wall of the device, forming a vortex as it swirls within the chamber. The larger particulates, because of their greater inertia, move outward and are forced against the chamber wall. Slowed by friction with the wall surface, they then slide down the wall into a conical dust hopper at the bottom of the cyclone. The cleaned air swirls upward in a narrower spiral through an inner cylinder and emerges from an outlet at the top. Accumulated particulate dust is periodically removed from the hopper for disposal.

3. Scrubbers

Devices called wet scrubbers trap suspended particles by direct contact with a spray of water or other liquid. In effect, a scrubber washes the particulates out of the dirty air stream as they collide with and are entrained by the countless tiny droplets in the spray.

Several configurations of wet scrubbers are in use. In a spray-tower scrubber, an upward-flowing airstream is washed by water sprayed downward from a series of nozzles. The water is re-circulated after it is sufficiently cleaned to prevent clogging of the nozzles. Spray-tower scrubbers can remove 90 percent of particulates larger than about 8 μm.

4. Electrostatic precipitators

Electrostatic precipitator is devices that used electrical energy directly for the removal of particulate matters from the carrier gas stream.

The principle on which this equipment operates is that, when a gas containing aerosol is passed between two electrodes that are electrically insulated from each other and between which there is considerable difference in electric potential, aerosol, particles precipitate on the low potential electrode.

5. Bag filters

The most common type of fabric is the tubular type, consisting of tubular bags. It consists of numbers of vertical bags of size 120 – 400mm diameter and 2 – 10m long. They are suspended with open ends attached to manifold. The hopper bottom is serving as collector for the dust.