Drying Steps under Superheated Steam: A Review and Modeling

Abstract

Superheated steam drying has been a subject of research for many decades. Many researchers have claimed that superheated steam drying is saving energy and produces better product quality compared to air drying. Superheated steam can be distinguished from air drying by the diffusion step in the drying process. Steam drying does not include moisture diffusion from the interior of the particle to its surface. However, in air drying, diffusion is the main and the limiting step. This paper is presenting a review to the models have been used to describe drying under superheated steam. Also, modelling was carried out to all the steps that take place in the drying process. These steps are: initial condensation on the surface of the particle, diffusion of the initially condensed vapour to the interior of the particle, evaporation of the initially condensed vapour and finally drying of the whole particle due to receding core model. Understanding these steps is very important for controlling the quality of the dried products and preventing difficulties such as sticking. These steps were modelled using MATLAB software. Numerical solutions with finite difference Euler’s method were used to solve the equations describe the drying steps. The theoretical results were then formulated in figures to show the behaviour of the whole drying process. Comparison of the theoretical results from this study with experimental data was left for the upcoming article.