Theoretical description of the motion of a particle in rotary dryer

Abstract

This paper presents a theoretical description of a particle motion in a rotary dryer equipped with straight lifters distributed on its periphery. In this configuration, the transport of granular materials occurs with cyclic cascades that can be decomposed into three phases: lifting, discharging, and falling into the air stream. In order to describe each of these phases, we have focused on the motion of a single particle in a rotating drum. In this condition, the analytical solution of the motion equation of each phase is found. With these solutions, the position and the velocity of the particle at any time are thus expressed as a function of physical parameters of the particle, physical parameters of the drum, and physical parameters of air in the drum, called operating parameters in practice. With these equations, we are able to calculate the behaviour of the particle as a function of the operating parameters. The transposition to the industrial context is made with an application. We show how these equations particularly permit the estimation of the Mean Residence Time (MRT) of material during the drying process as a function of operating parameters. Such estimations have been validated by comparison with experimental data of MRT found in the literature. The work presented in this paper gives some useful mathematical relations for whose who are interested in drum design optimization (lifter length, drum radius, drum length, etc.). More specifically, they can be used to help with the choice of operational parameters values that would achieve a given value of MRT for particular product.

An analysis of optimal segmented flight design in a rotary dryer

“…The corresponding flight position will be noted θ max . Contrary to δ 0 , it is not possible to determine analytically values of δ max for all flight configurations, since it depends on the dynamic repose angle γ p given by equation (5), which in turn depends on δ (and so on δ max ). Maximum discharging angle δ max is given by:…”

“…According to the technological configuration of the system, the flights can also be used through a positive or negative slope to modify the transverse movement of the material. On the whole, the movement of solid particles inside the dryer can be decomposed into successive cascading steps [4,5].…”

“…Improving rotary dryer design to reduce power consumption and provide a better quality control of the final product, is of major interest to industries dealing with such equipments. For this reason, rotary dryers have been and are still widely studied theoretically [4][5][6][7][8], experimentally [8][9][10][11] and numerically [12][13][14]. Design of dryers is very important to control the drying performance.…”

“…The last are concerned with dryer optimisation based on geometrical considerations and basic material properties such as repose angle. Among this last group of studies, some are more focused on mean residence time (MRT) prediction inside a rotary drum [5,22], while others are more interested in how flight shape influences cascading patterns through falling height and volume of material carried and released by the flights. Our paper belongs to this last category of studies.…”

Investigasi awal karakteristik perpindahan panas rotary dryer dengan sistem ruang vakum bersirip

“…Sirip-sirip pada ruang pengering vakum sangat berpotensi meningkatkan kelayakan sistem pengeringan vakum (Calín-Sánchez, et al, 2020). Untuk meratakan proses perpindahan panas konduksi yang terjadi, ruang pengeringan mengadopsi sistem berputar (rotary) (Hellou, et al, 2018, Djamila, et al, 2021.…”