Description

Reverse-flow cyclone with a tangential slot inlet, for gas–solid separation. The gas describes a descending outer vortex along the cylinder and cone and leaves through the vortex finder in an ascending inner vortex; the particles migrate to the wall under centrifugal force and are discharged at the dust outlet.

Calculation methods

• Size a cyclone: body diameter, number of cyclones in parallel, principal dimensions, pressure drop and blower power required to reach a target overall collection efficiency, for a given gas flow, dust concentration and median particle size.
• Check a cyclone: overall collection efficiency, cut size, pressure drop and grade efficiency curve of a cyclone of known diameter.

Standard geometries

a, b: inlet height and width; De, S: vortex finder diameter and length; h: cylinder height; H: total height; B: dust outlet diameter. Other proportions may be entered under Custom proportions.

Model

Muschelknautz method (VDI Heat Atlas, L3.4), which accounts for wall friction, the secondary flow along the roof and mass loading. Above the critical load ratio $\mu_{lim}$, the excess solids separate at the wall immediately after the inlet; the remainder is classified in the inner vortex:

$\eta = \left(1 - \frac{Q_{sec}}{Q}\right)\left[\eta_w + \frac{\mu_{lim}}{\mu_e}\,\eta_v\right] + \frac{Q_{sec}}{Q}\,\eta_{sec} \qquad d_{50} = \sqrt{\frac{18 \mu (Q - Q_{sec})}{2 \pi h_s (\rho_p - \rho) u_i^2}}$

where $\mu_e$ is the solids load ratio (kg of dust per kg of gas), $\eta_w$ and $\eta_v$ the wall and inner-vortex separation efficiencies, $Q_{sec}$ the secondary flow, $h_s$ the height of the separation zone below the vortex finder and $u_i$ the tangential velocity at its radius. The walls are taken as hydraulically smooth. Every intermediate result is listed in the calculation steps.

Design criteria

• Inlet velocity between 15 and 25 m/s and pressure drop up to 3 kPa; both limits may be changed under Design coefficients.
• Default properties: air at 20 °C and 1 atm, quartz particles (2650 kg/m³).
• The results are model predictions; a final design should be confirmed against manufacturer data or tests.