Two‐phase Modeling and the Quality of Soybean Seeds Dried in a Counter‐current Moving Bed Drier

Abstract

The purpose of the present work is to study the simultaneous heat and mass transfer between air and soybean seeds in a countercurrent moving bed dryer, based on the application of a two‐phase model to the drying process. The numerical solution of the model is obtained by using a computational code based on backwards differential formulae. The experimental data of air humidity and temperature and of seed moisture content and temperature at the dryer outlet are compared to the simulated values, showing a good agreement. This work also analyzes the effect of the main process variables (drying air temperature, air relative humidity, air velocity and solids flow rate) on the soybean seeds quality during drying. Empirical equations fitted to the experimental data are proposed for predicting the soybean seed quality (germination, vigor and fissures) as a function of the investigated variables.

Analysis of Seed Quality and Drying Performance of a Multistage Countercurrent Sliding‐Bed Dryer

“…Lacerda et al [5] studied the influence of drying variables on the quality of soybean seeds. These authors worked with a countercurrent sliding-bed dryer and proposed some correlations to represent the indices of germination (G) and nonfissured seeds (F) as a function of the drying variables.…”

“…The grain drying process exerts a strong influence in maintaining the quality of the product during its conservation period, because it reduces the moisture content and the occurrence of biochemical reactions that degrade the product. In the literature many reports about changes in soybean seed quality during drying are available [5][6][7][8][9][10]. These studies have shown that care must be taken in any system that involves the movement of seeds, i.e., correct handling of the initial and final moisture content of the product, relative humidity, air mass flux, drying rates, and exposure time to hot air [11].…”

“…The parameters used in the comparison of these dryers were the seed quality indices and the moisture removal capacity. The soybean seed quality was evaluated based on germination and nonfissured seed indices, which were obtained by empirical functions described in our previous work [5]. The mathematical model has been solved numerically by an algorithm implemented with Matlab ® software.…”

“…The two-phase model, which comprises mass and energy balance equations applied to both fluid and solid phases and which requires con-stitutive equations for the heat transfer coefficient between these two phases, namely the drying kinetics and the equilibrium moisture content of the solid material, has been broadly used to describe drying in moving-bed dryers [5,[12][13][14][15][16][17][18].…”