(6cw) The Effects of Leg Length on the Flow Field and Separation Process of Cyclone Separator

Cyclone is a commonly used device in petrochemical industry. Although effects of operating parameters on cyclone have been studied a lot, the effects of leg length drawed little attention.  In this paper, the effects of different leg lengths on flow field and separation processes of cyclone are investigated using numerical simulation and experimental methods. A PV-type cyclone with different leg lengths are simulated with Reynolds Stress turbulence model using Fluent. The results show that with the increase of leg length, the axial velocity curve changed to single peak from Twin Peaks. With further increase, the axial velocity begins to decrease, this leads to the decrease of particle residence time at the central area. After a critical length, the increased dipleg has no effect on the flow field and that critical length should be the most reasonable leg length. Also, as shown in Fig.1, the pressure drop in the cyclone is decreased with the increase of dipleg length and after a critical length, the pressure drop reaches a constant value. Fig.2 further indicates this trend and it also illustrates that the natural vortex length decreases slightly with the increase of leg length. In summary, it’s appropriate to extend the length of leg to benefit the separation but it’s not simply the longer the better. We should calculate the best leg length of different types of cyclones under their actual operating conditions.