Cyclone Separator Principle
• A cyclone/cyclone separator is essentially a settling chamber in which the gravitational separating force is replaced by a much stronger centrifugal separating force (to increase the settling rate).
• Cyclones/cyclone separators are used for the separation of solids from fluids. They offer one of the least expensive means of dust collection (separation of dust particles from gases). They utilize a centrifugal force to effect the separation which depends on particle size and/or on particle density. Thus, cyclones are used to effect a separation on the basis of particle size or particle density or both.
• It consists of a tappering cylindrical vessel, i.e., a cylindrical vessel consisting of a top vertical section and lower conical/tappering section terminating in an apex opening - a short vertical cylinder which is closed by a flat plate on top and by a conical bottom (Refer Fig. 4.6). It is provided with a tangential feed inlet nozzle in the cylindrical section near the top and an outlet for the gas, centrally on the top. The outlet is provided with a downward extending pipe - a pipe that extends inward into the cylindrical section - to prevent the gas short-circuiting directly from the inlet to the outlet and for cutting the vortex.
• In this separator, used for the separation of dust particles or mist from gases, the dust laden gas is introduced tangentially into a cylindrical vessel at a high velocity (30 m/s). Centrifugal force throws the solid particles out against the wall of the vessel and they drop into a conical section of the cyclone and removed from the bottom/apex opening. The clean gas is taken out through a central outlet at the top.
• Cyclones are widely used for collecting heavy and coarse dusts. These units may also be used for separating coarse materials from fine dust.
Liquid Cyclone (Hydroclone) :
• Liquid Cyclone separators may also be used to effect the classification of solid particles suspended in a liquid. In such cases, the commonly used liquid is water.
• Liquid cyclone has a top cylindrical section and a lower conical section terminating in an apex opening. The top vertical section is covered by a flat plate and is provided with a tangential inlet at the top. The cover has a downward-extending pipe to cut the vortex and remove the overflow product since the viscosity of water is much higher than that of a gas, the fluid resistance encountered in this liquid cyclone is greater than that in the cyclone used for dust collection. Therefore, the diameter of this liquid cyclone must be smaller in order to get a corresponding greater/larger centrifugal force. The pressure of a feed (induced by means of a pump) to the cyclone lie between 5 to 120 psi.
• The slurry feed is pumped into the cylindrical section tangentially. Coarse or heavy solids thrown out against the walls, travel down the sides of the cone section and are discharged in a partially dewatered form from the apex, while the smaller or lighter solids along with the remaining portion of water are removed from the downward extending pipe at the top. Liquid cyclones are used in degritting operations in alumina production, classifying pigments and ore-dressing practice.
- Also Read : Types of Industrial Valves