화학공학소재연구정보센터
Chemical Engineering Research & Design, Vol.110, 20-31, 2016
Measurement of particle concentration in a Wurster coater draft tube using light attenuation
Particle concentration in a coating zone of fluid bed coater is important to ensure appropriate coating uniformity and process yield. A transmissive optical setup at the top of the Wurster draft tube was used in a lab scale coater. Measured transmittances were converted to particle chord average volume fraction distributions using results of Monte Carlo calculations. The ranges of measured transmittances were from 0.002 to 0.285 and the range of particle chord average volume fraction was from 1.36% to 5.44%. The effect of gap between the draft tube and distribution plate, fluidizing air flow rate, particle size and load was studied. Comparisons of particle chord average volume fraction results with results of global particle volumetric fraction in the draft tube and particle cordal fraction obtained from CFD simulations are shown. In order to study the dynamics of the system as a function of different process parameters frequency analysis of transmittance signals was performed. Four distinct frequency responses were identified. Findings indicate presented local light attenuation method as suitable for assessing particle chord average volume fraction at the top of Wurster draft tube and with a potential for in-line method development. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.