Adjustment of mathematical models and quality of soybean grains in the drying with high temperatures

Abstract

A B S T R A C TThe aim of this study was to evaluate the influence of the initial moisture content of soybeans and the drying air temperatures on drying kinetics and grain quality, and find the best mathematical model that fit the experimental data of drying, effective diffusivity and isosteric heat of desorption. The experimental design was completely randomized (CRD), with a factorial scheme (4 x 2), four drying temperatures (75, 90, 105 and 120 ); however, not affect the final yield of the oil extracted from soybean grains (15.69%).Ajustes de modelos matemáticos e qualidade de grãos de soja na secagem com altas temperaturas R E S U M O O objetivo deste estudo foi avaliar a influência do teor de água inicial da soja e as temperaturas do ar de secagem sobre a cinética de secagem, qualidade do grão e encontrar o melhor modelo matemático que se ajustar aos dados de secagem experimental, a difusividade efetiva e o calor isostérico de dessorção. Foi adotado o delineamento experimental inteiramente casualisado (DIC) com esquema fatorial (4 x 2), quatro temperaturas de secagem (75, 90, 105 e 120 0 C) e dois teores de água inicial (25 e 19% b.s.) com três repetições. O teor de água inicial do produto interferiu no tempo de secagem. O modelo de Wang e Singh mostrou-se mais adequado para descrever o processo de secagem dos grãos de soja para as faixas de temperaturas do ar de secagem de 75, 90, 105 e 120 ºC e teores de água iniciais de 19 e 25% (b.u.). A difusividade efetiva obtida da secagem dos grãos de soja foi maior (2,5 x 10 -11 m 2 s -1) para a temperatura de 120 ºC e teores de água de 25% (b.s.). A secagem dos grãos de soja com temperaturas mais elevadas (acima de 105 ºC) e com maior teor de água inicial (25% b.u.) aumentou também a quantidade de energia (3894,57 kJ kg -1 ), ou seja, o calor isostérico de dessorção necessário para realizar o processo. A temperatura do ar de secagem e dos diferentes teores de água inicial afetou a qualidade dos grãos de soja ao longo do tempo de secagem (condutividade elétrica de 540,35 µS cm -1 g -1 ), no entanto, não interferiu no rendimento de óleo final extraído dos grãos de soja (15,69%).

Empirical models in the description of prickly pear shoot (Nopal) drying kinetics

“…For the models Peleg ( Figure 2E) and Wang & Singh ( Figure 2F), the statistical indicators used in the selection of the best model to represent the phenomenon were considered as good; however, based on the graphic representation of the fit to the data, they do not exhibit a physical behavior coherent with the study and even crossed the area of negative moisture ratio before reaching the equilibrium point of the dehydration process, indicating that these models can not be used to simulate the drying process of 'Miúda' prickly pear shoots within the studied range of temperatures. Such behavior is different from that found by Coradi et al (2016) for the Wang & Singh model, which was more adequate to describe the drying of soybean grains. However, one must consider the product to be dried, as well as its geometry, which influences not only the model, but also the drying speed.…”

Development of the method of exposure control of grain drying in high­temperature dryers

“…The kinetics of soybean seed drying has been given in [8]. The obtained Wang and Singh mathematical model confirms the dependence of the soybean heating temperature on changes in moisture during drying.…”

<b>Validation of an experimental prototype of thick-layer fixed bed dryer and determination of the quality of the dried soybean grains

“…As the drying air temperature increased, the rate of water removal from the grains also decreased, indicating a greater resistance to heat transfer and mass from the interior of the product to its surface. These results suggest that diffusion is the main mechanism that determines the movement of water (Coradi, Fernandes, & Helmich, 2016b;Jangam et al, 2010;Rafiee et al, 2009;Siqueira, Resende, & Chaves, 2012).The results of the specific mass analysis are shown in Tables 6 and 7. The temperature of the drying air changes the specific mass of the grains.…”