CHEMICAL ENGINEERING TRANSACTIONS VOL. 43, 2015 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Chief Editors: Sauro Pierucci, Jiří J. Klemeš Copyright © 2015, AIDIC Servizi S.r.l., I SBN 978-88-95608-34-1; I SSN 2283-9216 Dust Generation in Vibrated Cohesive Powders Hamid Salehi Kahrizsangi, Daniele Sofia, Diego Barletta, Massimo Poletto* Dipartimento di Ingegneria Industriale - Università di Salerno, Via Giovanni Paolo II, 132 – 84084 Fisciano (SA) –Italy mpoletto@unisa.it The process of dust release from aggregative cohesive powders under the action of mechanical vibration is studied. Beds of cohesive Potato Starch and Silica powders at fixed heights were vertically vibrated in a column in which vibration, frequency and acceleration levels can be independently set. Acceleration was changed with acceleration gravity ratio (a/g) values ranging between 5 and 9, while frequencies were set at 70 and 120 Hz. Vertical air flow rates through the bed were used to simulate air entrainment. Air in the head space above the bed was extracted and filtered in order to quantify the released dust rates. Results of these experiments are discussed and analyzed with reference to both the aggregative behavior of these powders and the inter-particle forces estimated from the bulk flow properties measured with conventional and standardized powder flow testers. A good relationship is found between the natural tendency of these powders to generate aggregates, the inter-particle forces and applied acceleration levels. Better insight of the physics is required to understand the effect of frequency on the dustiness of these powders. 1. Introduction Production, trade and processing of fine powders require handling and transport of these materials that are prone to releases of airborne dust. The use of powders, fine to the nanometric scale, makes the control of the dust emission (Saleh et al., 2014) of primary importance to carry out safe operations (Grima-Olmedo, 2014). Control and prevention of dust emission require the understanding of the tendency of these powders to release dust (Faschingleitner and Höflinger, 2011) as well as the ability of modelling the process in order to quantify the amounts of the emitted dust (Wypich et al. 2005). Appropriate measuring sytems should be applied depending on the operation generating dust (Hamelmann and Schmidt, 2004). Application of vibrations is often used to simulate the effects of transport on the dusts release (Saleh et al., 2014). However, a correct scale up of results requires a certain understanding on the fundamental physics involved in dust releases. In particular, it is necessary to relate the tendency of dust generation to the agglomeration behavior of fine and cohesive powders. In fact, on the one hand agglomeration determine the active surface generating dust emission, on the other hand it contain dust emission by means of cohesion. In this paper, the role of vibration on dust emission is studied in a fluidized bed assisted by mechanical vibrations. The aggregative analysis developed by Barletta et al. (2007) and applied by Barletta and Poletto (2012) to gas fluidized beds assisted by mechanical vibration is used to discuss the results. 2. Apparatus A sketch of the apparatus, a vibrated fluidization column and a dust metering system, is reported in Figure 1. 2.1 Vibrated fluidization column The fluidization column was made of perspex with an 85 mm ID and a height of 400 mm (1). At the bottom, the air was distributed by a 10 mm thick porous plate of sintered brass particles, 10 µm in diameter. The porous plate was clamped in the flange connecting the wind box and the fluidization column. In the column flange, a pressure port was connected to a u-tube manometer (6) filled with water. Desiccated air from the laboratory line was fed to the wind box by a thermal mass flow controller (Tylan FC2900V) with a maximum flow rate of DOI: 10.3303/CET1543129 Please cite this article as: Salehi Kahrizsangi H., Sofia D., Barletta D., Poletto M., 2015, Dust generation in vibrated cohesive powders, Chemical Engineering Transactions, 43, 769-774 DOI: 10.3303/CET1543129 769