Separation and Purification Technology 49 (2006) 157–166 Study of the separation efficiency and the flow field of a dynamic cyclone Jinyu Jiao a , Ying Zheng a,∗ , Guogang Sun b , Jun Wang b a Department of Chemical Engineering, University of New Brunswick, 15 Dineen Drive, P.O. Box 4400, Fredericton, NB, Canada E3B 5A3 b Department of Chemical Engineering, University of Petroleum, Beijing 102249, China Received 28 April 2005; received in revised form 12 September 2005; accepted 16 September 2005 Abstract The separation efficiency and the flow field of a dynamic cyclone were studied experimentally and simulated using commercial CFD software (FLUENT 6.0). The experimental results show that the rotational classifier position and the ratio of the classifier opening area to the inlet area have significant impact on the separation efficiency of the dynamic cyclone. The separation efficiency can be significantly improved as the classifier rotates at a speed beyond its natural swirling frequency. The RSM model was used to simulate the 3-D gas flow field, and the simulation predictions were validated by the experimental results measured by a five-hole pressure probe. The tangential velocity distribution in the dynamic cyclone body can be divided into three zones: inlet, separation, and bottom. Each zone has its own tangential velocity distribution curve. The effects of operating conditions and geometric parameters of the classifier on the tangential velocity distribution were also studied. © 2005 Elsevier B.V. All rights reserved. Keywords: Dynamic cyclone; Simulation; Separation efficiency; Tangential velocity; Classifier 1. Introduction Many industrial processes, such as mineral processing, petroleum refining, chemical engineering, food processing, and environmental cleaning, involve the separation of particles from an air stream. Several technologies, including fabric filters, elec- trostatic precipitators, air classifiers, and cyclone separators, can be used for gas–solid separation [1]. Because fabric filters and electrostatic precipitators incur high initial and operating costs, they are not suitable for many industrial applications, although they have a high efficiency for fine particle separation. Air classifiers have numerous types, and each type has spe- cific technical requirements and is suitable for specific products [2,3]. In practice, various gravitational and centrifugal classi- fiers are employed, such as gravitational air classifiers, fluidized bed classifiers, cascade air classifiers, inertial air classifiers, and centrifugal air classifiers. Centrifugal air classifiers can yield differing cut sizes by adjusting the centrifugal acceleration [4]. The MikroCut MC classifier [5] is a typical centrifugal classifier Abbreviations: CFD, computational fluid dynamics; DC, dynamic cyclone; LES, large-eddy simulation; RNG, re-normalization group theory; RSM, Reynolds stress model ∗ Corresponding author. Fax: +1 506 453 3591. E-mail address: yzheng@unb.ca (Y. Zheng). and can separate particles below 10 m. However, its relatively complicated geometries and high initial cost limit its use in some industrial processes. The cyclone separator is widely used for its main advantages of simple structure and low cost. However, as the separation in cyclones relies on the inertia forces of the par- ticles, conventional cyclones generally have low efficiency for fine particle separation [6]. To improve cyclone performance, researchers have made large efforts during the past decades. These efforts can be divided into two methods: one method is to optimize the configurations and geometric dimensions of the cyclones, and the other method is to add additional devices to the cyclones. The Stairmand high-efficiency cyclone [7] was the result of the first method. Shi et al. [8] also developed a set of design methods by optimizing cyclone dimensions to improve separation efficiency. However, optimized cyclone separators still cannot meet the requirements of fine particle separation. Thus, some researchers began to seek an alternative approach by introducing additional devices to cyclones so as to obtain high separation efficiency. Chmielniak and Bryczkowski [9,10] built a cyclone-type separator with a swirling baffle. Ray et al. [11] presented a Post Cyclone positioned above the vortex finder that could collect a certain fraction of the particles escaping through the vortex finder. Brouwers [12] designed a rotational particle separator that could separate fine particles from gas in laminar flow. These improvements have made it possible to use cyclones 1383-5866/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.seppur.2005.09.011