Drying Characteristics and Kinetic Modeling of Paddy Rice in an Infrared Dryer Powered by Liquefied Petroleum Gas

Abstract

This study aim to investigate the drying characteristics and kinetic modeling of paddy rice using an infrared dryer powered by liquefied petroleum gas and to develop a mathematical model to predict moisture changes during the drying process. Paddy rice samples with initial moisture contents of 20% and 30% (wet basis) were dried at infrared temperatures of 550, 650, and 750°C for 2, 4, 6, 8, and 10 minutes. The moisture ratio (MR) was calculated as a function of drying time and fitted to thin-layer drying models Newton Model, Page Model and Logarithmic models. Model performance was evaluated using the coefficient of determination (R²), root mean square error (RMSE), and chi-square (X²). The results showed that increasing infrared temperature significantly enhanced the drying rate. Infrared temperature of 750°C resulted in rapid moisture reduction but led to elevated grain temperature, increasing the risk of structural damage. Infrared temperature of 550°C produced a lower moisture reduction rate and required a longer drying time. The infrared temperature of 650°C provided a suitable balance between drying efficiency and grain temperature control. Among the tested models, the Page model, expressed as MR = exp(−ktⁿ), provided the highest accuracy under all conditions. At Infrared temperature 650°C with an initial moisture content of 30% (wet basis), the model R² = 0.99488 and RMSE = 0.00608 with kinetic parameters k = 0.32446 and n = 0.44687. The model accurately predicted the drying behavior and demonstrated potential for application in the design and control of paddy rice drying processes.