Descrição da secagem contínua e intermitente de arroz em casca usando modelos de difusão.

Abstract

The technological development of the drying process of agricultural products plays a fundamental role in minimizing the waste of food. In this sense, intermittent drying has shown good results, improving the final quality of the product and reducing energy consumption. This work aims to conduct a study of the continuous and intermittent drying of rice in the husk using empirical and diffusion models to describe the phenomena that occur during these processes. Continuous and intermittent drying experiments (with an intermittence ratio α = 2/3) of rice grains were carried out using a fixed bed drier at temperatures of 50 and 70oC. Empirical models were used to simulate drying kinetics and to evaluate which model best fits the experimental data. Through the diffusive models, we present analytical and numerical solutions of the diffusion equation for the cylindrical geometry. For the numerical model, the diffusion equation was developed by the finite volume method, with a totally implicit formulation. Effective drying time for mathematical modeling and simulation of moisture distributions were considered. The comparison between the kinetics of continuous and intermittent drying indicated a reduction of the drying time with the application of the intermittence, providing a greater energy saving. It has been found that the boundary condition of the first type is the one that best describes the drying process of the husked rice and that the effective mass diffusivity increased with intermittent drying. The results state that not only the ratio of intermittence is important for the reduction of drying time, but also tempering period.