(20e) Effect of a Recirculation System in an Industrial Cyclone Separator

Dedusting or separating a dispersed phase from a continuous phase is important in all process engineering industries. Gas cyclones are the most preferred separators for exhaust dedusting in industrial plants. They are simple in design and can operate at high temperatures. These gas cyclones are characterized by their separation efficiency and pressure loss. For higher separation efficiencies, pressure losses should have to be compromised. Even with higher pressure loss, gas cyclones have relatively low separation efficiency for dedusting PM2.5 gases. Gas cyclones are commonly used as pre-separators with additional downstream exhaust cleaning systems, increasing the overall installation, operational and maintenance costs.

An operational cyclone from an industrial partner has been taken for an initial study, and numerical simulations were conducted to identify the separation efficiency and the pressure drop. Simulation results revealed that few particles escape with the secondary flow via the lip leakage and more particles with smaller aerodynamic diameters leave the inner vortex region without getting separated.

A recirculation system containing a nozzle, a diffuser and an agglomeration chamber has been introduced to redirect the unseparated dust particles leaving the cyclone back into the inlet of the cyclone. This recirculation system creates a static pressure difference between the wall of the vortex finder and the inlet pipe, which helps the particles closest to the vortex wall re-enter the cyclone.

Numerical simulations have been performed with PM2.5 gas flow using the Reynolds Stress Model with the Eulerian-Lagrangian approach for various dimensions of the recirculation system’s components and its effect on the separation efficiency was analysed. Simulation results reveal that the particles re-entering together with the gas stream produces different separation efficiencies for different dimensions of the recirculation system’s components, which will be presented at the congress.