Effects of the mass and volume shrinkage of ground chip and pellet particles on drying rates--颗粒学报PARTICUOLOGY

Rezaei, H., Sokhansanj, S., Lim, C. J., Lau, A., & Bi, X. (2018). Effects of the mass and volume shrinkage of ground chip and pellet particles on drying rates. Particuology, 38, 1-9. https://doi.org/10.1016/j.partic.2017.09.001

Effects of the mass and volume shrinkage of ground chip and pellet particles on drying rates

Hamid Rezaei ^a *, Shahab Sokhansanj ^{a b}, C. Jim Lim ^a, Anthony Lau ^a, Xiaotao Bi^a

a Chemical and Biological Engineering Department, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
b Environmental Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37381, USA

10.1016/j.partic.2017.09.001

Volume 38, June 2018, Pages 1-9

Received 9 November 2016, Revised 24 July 2017, Accepted 26 September 2017, Available online 9 December 2017, Version of Record 2 April 2018.

E-mail: hamidrezaei@chbe.ubc.ca

Highlights

• Ground pellet particles were denser and dried more slowly than ground chip particles.

• Bulk of pellet particles shrank more than chip particles, despite their similar particle shrinkage.

• The variable radius drying model fitted better with experimental data than fixed radius model.

• The higher relative humidity of atmospheric air prolonged the drying process at 50 °C.

Abstract

The effects of varying the mass and volume of ground chip and pellet particles on the particle drying rate were analyzed. Samples of whole pellets and chips were hammer milled using a 3.2 mm screen and the ground chip and pellet particles were found to have similar size distributions, although the pellet particles were denser and more spherical than the chip particles. Prior to drying, water was added to the particles to obtain 0.10, 0.30, 0.50, 0.70, and 0.90 moisture contents (on a dry mass basis). The moistened particles were subsequently dried in a constant temperature thin layer dryer set at 50, 100, 150, or 200 °C under dry pure nitrogen, dry compressed air, or atmospheric air. The chip and pellet particles exhibited similar degrees of shrinkage, but the pellet particles underwent a greater reduction in their bulk volume during drying. It appears that the more spherical pellet particles are prone to shrinkage in more than one direction, whereas the needle-like chip particle shrink only in one direction. A variable radius first order drying model was found to fit the experimental data better than a fixed radius model.

Graphical abstract

Keywords

Moisture loss; Particle density; Ground chip; Ground pellet; Particle shrinkage; Bulk shrinkage

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