Dust-purification-techniques

Cyclones
Synonyms for cyclone separator are also substance cyclone, multi cyclone, vortex separation and wet cyclone. A cyclone is centrifugal separator where the particles are swung as a result of their mass by the centrifugal force to the outside. Entering air is automatically forced a rapidly spinning double vortex movement, so-called "double-vortex". This double vortex movement exists from the outside stream, that flows spirally down and the inside stream that flows spirally up. On the border area of both flows the air flows from one to the other. The particles present in the air flow is swung to the outside wall and leaves the separator by means of a reception space situated to the base.
Figure: Cyclone separator (source: http://www.meridianeng.com/cyclone.gif) The air entrance speed of a cyclone lies between 10 and 20 m/s, the most usual speed is approx. 16 m/s. At fluctuations with these speeds (with lower speeds) the separation efficiency decreases very rapidly. To give an indication to the separation efficiency the formula of Lappleis used that is: d₅₀ = √(9μb / 2πN Γ_iv_i) In which: d50 = particle sizes that with 50% outputs are broken away from (m) b = inlet width of the cyclone supply (m) N = number of turn cycles in the cyclone (≈ N=5, stipulated empirically) vi = inlet speed (m/s) Γi = specific mass of the dust particle (kg/m³) µp = viscosity of the gas (kg/m). Cyclones are most efficient at high air entrance speed, small cyclone diameter and large cylinder length (pencil cyclones). The advantages of a cyclone as separator for substance are: Simple construction No moving components Little maintenance Low investment and functioning costs Constant pressure drop Saves room Dry relief during wet cyclone The disadvantages are: High pressure drop (0.5 - 2.5 kPa), depending on of the construction version Low output for low particle diameter Bad performances at charge Emission of effluent at wet cyclone Erosion sensitive and constipation danger to the entrance Possibly noise nuisance Usually a cyclone is used for its relatively high remaining emission because of its relatively small efficiency and used as a pre-separator to remove the largest dust load for second dust removal installation like for example a scrubber or cloth filter. The pre-separator happen generally on particles > 5µm and are employed its in: The wood - and piece of furniture industry The construction sector The glass industry The transport sector with storage - and shipment The foods industry Detritus combustion installations The chemical industry Melting processes in metallurgy Coffee heathers Click here for more information for dust removal technology For more books and reading information see our website: Air treatment books overview

Dust-purification-techniques

Cyclones