Dimensionamento e experimentação de um secador de leito fixo para a secagem de produtos agrícolas

Abstract

Drying is an essential step in maintaining the quality of agricultural products in postharvest. Knowledge of drying curves thin layer and the variation of the physical properties of agricultural products during drying, provide key information for the development, optimization and operation of equipment for this post-harvest stage. Among the variables that generate influence on the drying process, the temperature and air velocity are among the most important, directly impacting drying curves. In general, the research developed about the drying of agricultural products are carried in the laboratory, studying the effect of temperature, normally developed in forced air-ventilated oven. The present study aimed to design, build and evaluate an experimental dryer with temperature control and drying air velocity, aiming drying studies of agricultural products thin layer. The design of the experimental dryer was divided into three stages: heating supply dimensioning, geometric dimensioning of the dryer structure and fan selection to meet the operational demands of the dryer. The geometric dimensioning of expansions, homogenizers air and plenum of the experimental dryer were made based on recommendations in the literature. The execution of the project was developed in two phases, the first being the construction the dryer structure and the second automation temperature control and air velocity. For evaluation of the projected variables, measurements of temperature and velocity of the drying air were made and temperature of the dryer structure. Furthermore, there was a drying kinetics experiment thin layer to evaluate the efficacy of the dryer. Safflower grains were subjected to drying, a thin layer with different temperature levels (40, 50, 60, 70 and 80 °C) and air velocity (0.4, 1.0 and 1.6 m s-1). The physical properties of safflower for different grain moisture contents during drying at a temperature of 40 °C was also determined. The obtained results allow concluding that the experimental dryer presented satisfactory results of the temperature control and air velocity when tested in drying experiments. The designed dryer was efficient in getting the drying curves thin layer of safflower grain for all drying air conditions evaluated in this study, the traditional model of Page, among the models satisfactorily fitted the experimental results, the chosen to represent their drying curves. In all evaluated for physical properties safflower culture, was no effect of reducing the moisture content during drying.