Currently cyclone separators are mainly used for the removal of particles from a spinning gas stream, using centrifugal force. It consists of a barrel upper section with a conical lower section and a smaller cylinder in the centre of it. The cylinder extends from the top to just below the entrance through which the air is discharged. The carrier gas stream enters tangentially at the top of the barrel portion of the cyclone and travels downwards into the cone portion of the cyclone forming an outer vortex. The result is an increased centrifugal force on the particles separating them from the air stream, because of the increasing air velocity in the outer vortex. Reaching the bottom of the cone, an inner vortex is then created,…show more content… Lapple derived the cut-off diameter as:
where: Ui = the gas velocity at the inlet; µ = the air dynamic viscosity; pp = the particle density;
C = the slip connection factor of the particle corresponding to Dp50.
The number of turns Nt can be calculated as Nt = tUi/πD and the residence time t is equal to the volume of the cyclone divided by the volumetric flow rate Q.
Stairmand and Barth:
Both Stairmand (1951) and Barth (1956) had it that when 50% of the particles spinning at the outer rim of the central core, where the tangential velocity is at its maximum (Umax), are collected, the corresponding Dp50 can be derived as:
Barth suggested that the diameter of the central core is De, while Stairmand claimed it to be De/2. Sairmand further added a fiction loss factor in the denominater of Eq. (2) to modify Dp50.
Licht’s Efficiency Model:
Licht developed another theory that is based on the assumption of turbulent flow with lateral mixing. Similarly the particle size with 50% collection efficiency needs to be determined first. For Licht’s theory, it is:
where: n = vortex exponent;