Name different methods of size separation. Explain any one with labelled diagram.
1 Answer
Answer :
Different methods of size separation are:
1 Sieving 2 Cyclone separator 3 Air separator 4 Elutriation
SIEVING:
Diagram:
Construction:
In this method fine powder is separated from coarse by using sieve of desired number.
In sieve separator sieves are arranged in descending order of size.
The bottom sieve is attached to receiving pan.
Working :Different methods used: 1 Agitation 2 Brushing 3 Centrifugation
CYCLONE SEPARATOR:
Construction-
Cyclone separator is size separation device
It consists of a cylindrical vessel with a conical base.
The upper part of the vessel is fitted with a tangential inlet and a fluid outlet.
At the base it is fitted with solid outlet
Working of cyclone separator
The suspension of a solid gas (Usually air) is introduced tangentially at a very high velocity so that rotary movement takes place within the vessel.
The fluid is removed from a central outlet at the top. The rotator flow within the cyclone separator causes the practices to be acted on by centrifugal force.
The solid are thrown out to the walls. There after it falls to the conical base and discharge through the solid outlet.
AIR SEPARATOR:
Construction:
It consist of a cylindrical vessel with conical base
The upper part of the vessel is fitted with a feed inlet and at base there are two outlets. One for fine and other for heavy particles.
Rotating disc and blades are attached to the central shaft to produce air movement.
Working:
The sample of powder is passed through the feed inlet, which falls on the rotating disc.
The rotating blades are attached to same shaft. The fine particles are picked up and are carried to the space, where air velocity is sufficiently reduced. The fine particles were dropped and collected at outlet. The heavy particles are removed at outlet for heavy particles.
Diagram:
ELUTRIATION:
Construction
The size separation of powder is based on the low density of fine particles and high density of coarse particles.
. The dry powder or paste is kept in an elutriating tank and mixed with large quantity of water.
The solid particles are uniformly distributed in the liquid by stirring and then it is allowed to settle down.
Depending on the density of the solid particles, it will either settle down or remain suspended in water.
The sample is withdrawn at different heights through the outlets. These are dried and thus the powder with various size fractions is collected.
Working:
The particles are suspended in a moving fluid, generally water or air.
The apparatus consists of a vertical column with an inlet near the bottom for suspension, an outlet at the base for coarse particles and an overflow near the top for fluid and fine particles.
One column will give a single separation into two fractions.
If more than one fraction is required, a number of tubes of increasing area of cross-section can be connected in series.
The velocity of fluid decreases in succeeding tubes as the area of cross-section increases, thus giving a number of fractions. These fractions are separated and dried.
Application:
Elutriating tank is used to separate the coarse and fine particles of powder after levigation
Diagram: