- 1 - Powder Technology 125 (2002) 298-305 – doi: 10.1016/S0032-5910(01)00518-6 © 2002. This manuscript version is made available under the CC-BY-NC-ND 4.0 license Modeling Of The Gas-Particle Flow In Industrial Classification Chambers For Design Optimization Dionysios I. Kolaitis and Maria A. Founti* National Technical University of Athens, Mechanical Engineering Department, Thermal Engineering Section, Laboratory of Combustion and Two-Phase Flows, Heroon Polytechniou 9, Polytechnioupoli - Zografou, Athens 15780, Greece Tel.: +30-10-772 3605 , Fax : +30-10-772 3663 * Corresponding author : e-mail: mfou@central.ntua.gr Abstract A computational approach has been developed for the prediction of the gas-particle flow and the simulation of the classification-settling characteristics of a particulate material flow in a gravitational classification chamber. By taking into account the classification chamber geometry and operating parameters, as well as the particulate material physical properties, the developed computational code allows the simulation, improvement and control of the operational characteristics of industrial settling, classification and/or separation chambers commonly used in process industries. The work assesses the performance of the computational code and demonstrates the capability of dedicated computational tools to model with accuracy, complex industrial multi-phase flows in order to support design criteria. 1. Introduction In pneumatic conveying systems transporting dry bulk particulate materials, there is a need to separate the solid particles from the flowing stream of the carrier gas, in order to recover the particles and to prevent air pollution. The selection of an appropriate separation device, such as gravitational or centrifugal classification chambers, cyclones, bag filters or electrostatic precipitators, depends mainly on the particle’s geometrical and physical properties. There are many references in the literature regarding the computational modeling of cyclone separators [1,2,3] since the are used quite extensively. On the contrary, gravitational classification chambers (GCC) have never been considered as state-of-the-art devices and they have not attracted such attention. GCCs are mainly referred in design handbooks relating to the classical empirical design procedure [4,5]. The only bibliographical references regarding the computational modeling of GCCs deal with liquid-solid flows in sedimentation tanks used in water treatment plants [6,7]. This work stemmed from an industrial problem where there was a need to separate the larger particles from a gas-particle suspension. Expanded perlite particles were pneumatically transported at an industrial plant via an inclined 20m long pipeline to a cyclone. During their transportation, the particles were also cooled by natural convection. The industry requested the installation of a device prior to the cyclone that could retain all particles with diameters larger than 2.5 mm and at the same time allow particles with diameter less than 0.5 mm to reach the cyclone. An optional, secondary requirement of the industry was that the device should be also able to allow particles with diameters greater than 0.5 mm and less than 1mm to reach the downstream cyclone. Mechanical separation of particles from a gas stream can be primarily achieved with the use of cyclone collectors, which can efficiently retain particles with diameters greater than 10 μm, employing centrifugal forces created by vortex flow to separate the particles. However, in the present case the particles to be retained were brittle and rather large, properties that imposed