Solids flux measurements via alternate techniques in a gas-fluidized bed Sina Tebianian a , Kristian Dubrawski a , Naoko Ellis a , Ray A. Cocco b , Roy Hays b , S.B. Reddy Karri b , Thomas W. Leadbeater c , David J. Parker c , Jamal Chaouki d , Rouzbeh Jafari d , Pablo Garcia-Trinanes e , Jonathan P.K. Seville e , John R. Grace a,⇑ a Department of Chemical and Biological Engineering, University of British Columbia, Vancouver V6T 1Z3, Canada b Particulate Solid Research, Inc., Chicago, IL 60632, United States c Positron Imaging Centre, University of Birmingham, Birmingham B15 2TT, United Kingdom d Département de génie chimique, Ecole Polytechnique, Montréal, QC H3T 1J4, Canada e Department of Chemical and Process Engineering, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom highlights  A travelling fluidized bed ensured identical operating conditions at several sites.  Solids flux was obtained by novel analyses of invasive and non-invasive methods.  The results are directly compared by quantitative and qualitative analysis.  The reasons underlying observed discrepancies among the results are discussed. article info Article history: Received 16 December 2015 Received in revised form 8 June 2016 Accepted 14 July 2016 Available online 16 July 2016 Keywords: Fluidization Solids flux Borescopy RPT PEPT abstract A transportable fluidization column, operating under identical conditions at three different locations, was employed to compare three experimental solids flux measurement techniques for hydrodynamic charac- terization of gas-fluidized beds. This paper compares measurements of solids mass and momentum flux obtained by radioactive particle tracking at the Ecole Polytechnique, positron emission particle tracking at University of Birmingham, and borescopic high speed particle image velocimetry at PSRI, carried out with FCC particles of mean diameter 107 lm. These techniques provided broadly similar time-average solids flux profiles, but there were significant quantitative differences. Analysis of the results, focusing on the fundamentals of each measurement technique, provides valuable insights into the reasons for the discrepancies. The results also add to a unique hydrodynamic database for validation of CFD and other models. Ó 2016 Elsevier B.V. All rights reserved. 1. Introduction Major advantages of gas-fluidized bed reactors, such as efficient bed-to-surface heat transfer and temperature uniformity, derive from the motion of the particles, largely induced by interactions between voids and the dense phase [1]. Hence reactor performance depends significantly on their hydrodynamics. Among the important properties that dictate the characteristics of a gas-fluidized bed, local solids flux plays a significant role. For example:  Heat exchange between immersed surfaces and a fluidized bed, operating in any flow regime, depends on the frequency of par- ticles reaching the surfaces and their velocity [2].  The solids circulation rate is a key parameter in determining the performance of circulating fluidized beds [3].  The mass flux of solids entrained from the bed is extremely important in determining the loss of solids not captured by cyclones. These factors highlight the importance of developing measure- ment techniques that accurately determine the instantaneous solids mass and momentum fluxes, e.g. based on simultaneous measurement of local instantaneous solids velocity and concentra- tion [4–6]. Suction probes represent a very simple technique for measuring the average solids mass flux in the upper dilute region http://dx.doi.org/10.1016/j.cej.2016.07.058 1385-8947/Ó 2016 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail addresses: sinatebian@gmail.com (S. Tebianian), jgrace@chbe.ubc.ca (J.R. Grace). Chemical Engineering Journal 306 (2016) 306–321 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej