Modeling the drying kinetics, performance evaluation, and economic analysis of rice drying using a rice husk-fueled mixed-flow dryer

In this study, performance evaluation, drying kinetics modelling and economic analysis of locally manufactured rice husk-fueled mixed-flow rice dryer were investigated. The dryer had a size of 0.4 × 0.4 × 0.64 m (width, length, and height) with a holding capacity of 30 kg in a batch. The drying air used had a volume flow rate of 0.06 m³/s, with an average drying air velocity of 0.62 m/s within the drying section. The average temperature recorded during the experiment was 49.5 ± 3.1℃ at the dryer inlet, while the ambient air temperature was 26.4 ± 0.2℃. The dryer was able to reduce the moisture content of the sample rice from 20.9 % (wet bases) to 12 % (wet bases) in 3 h and 10 min, achieving an average drying rate of 0.076 kg water per minute or 0.016 kg water per kg dry matter per minute. In order to achieve this drying rate, the average energy consumption was 37.9 MJ with an average of 54.29 % dryer efficiency. The Modified Henderson & Pabis was the best drying model to predict the drying kinetics in this study among the different thin-layer drying models. The milling quality of the dry product was assessed using the Head Rice Yield (HRY). The HRY was found to be 57.4 ± 0.62 % for long and slender Nerica-4 rice cultivars, the result was above the required customer requirement which is 55 % and more. Furthermore, the economic analysis indicated that the payback period for the developed rice husk-fueled mixed-flow dryer for drying rice was 1.4 years. The dryer, which costs 64,213ETB (approximately USD 1,230) has the potential to significantly reduce postharvest loss and enhance food security and income of smallholder farmers in rural off-grid areas.