Mathematical modeling of the drying of orange bagasse associating the convective method and infrared radiation

Abstract

A B S T R A C TMathematical modeling enables dimensioning of dryers, optimization of drying conditions and the evaluation of process performance. The aim of this research was to describe the behavior of orange bagasse drying using Page's and Fick's second law models, and to assess activation energy (using Arrhenius equation), moisture content, water activity and bulk density of product at the end of the process. The drying experimental assays were performed in 2011 with convective air temperature between 36 and 64 ºC and infrared radiation application time in the range from 23 to 277 s in accordance with the experimental central composite rotatable design. Analysis of variance and F-test were applied to results. At the end of the drying process, moisture content was about 0.09 to 0.87 db and water activity was between 0.25 and 0.87. Bulk density did not vary under studied conditions. Empirical Page's model demonstrated better representation of experimental data than the Fick's model for spheres. Activation energy values were about 18.491; 14.975 and 11.421 kJ mol -1 for infrared application times of 60; 150 e 244 s, respectively.Modelagem matemática da secagem de bagaço de laranja associado ao método convectivo e radiação infravermelha R E S U M OA modelagem matemática permite o dimensionamento de secadores, otimização das condições de secagem e avaliação do desempenho do processo. O objetivo deste trabalho foi descrever o comportamento da secagem de bagaço de laranja utilizando-se os modelos de Page e a segunda lei de Fick, avaliar a energia de ativação (equação de Arrhenius), o teor de água, a atividade de água e a massa específica aparente do produto ao final do processo. Realizou-se a secagem de bagaço de laranja com temperatura do ar convectivo entre 36 e 64 ºC e tempo de aplicação da radiação infravermelha na faixa de 23 a 277 s de acordo com planejamento experimental central composto rotacional. IntroductionBrazil is the largest processor of orange juice, contributing with 50% of world production. It is considered that 100 kg of orange produce 55 kg of juice, and the remaining 45 kg are residues of the process, such as discarded oranges, zest, seed, and waste resulting from the extraction of essential oil and washed pulp (Cavichiolo, 2010).Because of its nutritional value, the orange bagasse can be used in the production of animal feed after undergoing drying. Thus, different methods for drying and dryers (cyclone dryer, pneumatic dryer, rotary dryer, flash dryer, among others) have been researched recently (Cavichiolo, 2010; Fiorentin et al., 2010a). Costa et al. (2015) studied sugarcane bagasse drying in a fixed bed and its desorption isotherm.The use of artificial drying in preservation of agricultural products has expanded, creating the necessity for faster methods and more energy-saving processes. Drying using infrared radiation is a method that offers lower power loss compared with convective drying, since the energy in an electromagnetic wave is directly absorbed by the product (Mongpraneet et al...

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

“…RX -Moisture ratio, dimensionless; T -Drying time, h; K, ko, k1 -Drying constants, h -1 ; a, b, c, n -Coefficients of the model Source: Rodrigues (2015) Model Name Empirical expression -chi-square; X* exp -experimental moisture ratio; and X* pre -moisture ratio predicted by the model. Table 2 shows the parameters obtained from the fit of the models Henderson & Pabis, Lewis, Page, Peleg, Silva et al (2012) and Wang & Singh to the drying of minimally processed 'Gigante' prickly pear shoots, at temperatures of 50, 60, 70 and 80 °C.…”