The optimization of paddy drying in the rotary dryer: energy efficiency and product quality aspects analysis

Currently, paddy drying has been widely developed and applied. This research goal was to find the optimal condition of paddy dried in a rotary dryer. The process was conducted at various paddy capacities (10–40 kg) and temperatures (40–60°C). For main indicators, the drying time, physical quality of the product and energy efficiency were evaluated. In doing so, the optimization process with the response surface method (RSM) was conducted. Results showed that under higher temperatures, the moisture level in the paddy reduced quickly, resulting in a shorter drying time and higher efficiency. However, faster moisture reduction can break the texture of paddy, which increases the percentage of broken rice. Meanwhile, with the increasing paddy capacity, heat transfer becomes more effective, as seen in the increase in energy efficiency. Nevertheless, the excessive capacity requires a longer drying time. After optimizing by response surface method (RSM), the most favorable condition can be reached at paddy capacity of 45.8 kg with drying temperature of 56.4°C. For this condition, energy efficiency achieved 15.6% with percentage of broken rice 8.18%.