Amorphous particle deposition and product quality under different conditions in a spray dryer--颗粒学报PARTICUOLOGY

Woo, M. W., Daud, W. R. W., Tasirin, S. M., & Talib, M. Z. M. (2008). Amorphous particle deposition and product quality under different conditions in a spray dryer. Particuology, 6(4), 265–270. https://doi.org/10.1016/j.partic.2008.03.008

Amorphous particle deposition and product quality under different conditions in a spray dryer

Meng Wai Woo^*, Wan Ramli Wan Daud, Siti Masrinda Tasirin, Meor Zainal Meor Talib

Department of Chemical & Processing Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor DE, Malaysia

10.1016/j.partic.2008.03.008

Volume 6, Issue 4, August 2008, Pages 265-270

Received 31 October 2007, Accepted 17 March 2008, Available online 30 June 2008.

E-mail: woomengwai@gmail.com

Highlights

Abstract

Deposition of amorphous particles, as a prevalent problem particularly in the spray drying of fruit and vegetable juices, is due to low-molecular-weight sugars and is strongly dependent on the condition of the particles upon collision with the dryer wall. This paper investigates the condition of the amorphous particles impacting the wall at different drying conditions with the aim of elucidating the deposition mechanism and physical phenomena in the drying chamber. A model sucrose-maltodextrin solution was used to represent the low-molecular-weight sugar. Particle deposits were collected on sampling plates placed inside the dryer for analyses of moisture content, particle rigidity (using SEM) and size distribution. Moisture content was adopted as a general indicator of stickiness. Product particles collected at the bottom of the experimental dryer were found to have higher moisture than particle deposits on samplers inside the dryer. Moisture content profile in the dryer shows that apart from the atomizer region, where particles are relatively wet, particle deposits at other regions exhibit similar lower moisture content. At the highest temperature adopted in the experiments, particles became rubbery suggesting liquid-bridge formation as the dominant deposition mechanism. Further analysis on particles size distribution reveals a particle segregation mechanism whereby smaller particles follow preferentially to the central air stream while larger particles tend to re-circulate in the chamber, as predicted in past CFD simulation. The findings from this work will form the basis and provide validating data for further modeling of wall deposition of amorphous particles in spray drying using CFD.

Graphical abstract

Keywords

Powder handling; Amorphous particles; Deposition; Particle condition; Spray drying

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