Innovative design and experimental validation of a mechanized rice destoner

The prevalence of foreign materials particularly stones in locally processed rice continues to pose significant health risks and reduces the commercial value of the product. Manual destoning methods are widely used in small-scale operations but are time-consuming, inefficient, and often ineffective. Imported mechanized destoners, while more effective, are typically too costly and complex for rural processors. This study presents the design, development, and performance evaluation of a low-cost, efficient rice destoner suitable for small and medium-scale rice processing enterprises. The machine employs the principles of density-based separation, combining vibratory motion and airflow to effectively isolate stones from rice grains. Constructed from locally available materials, the destoner consists of a vibrating sieve tray, a blower unit, and a dual outlet system, powered by a 1 hp electric motor. Design calculations were carried out to determine optimal airflow velocity, vibration frequency, and sieve aperture size. Performance evaluation was conducted using rice samples with known quantities of impurities. The prototype achieved a destoning efficiency of 93.5%, with a throughput capacity of 250 kg/h and a grain loss rate of 2.4%. These results demonstrate the potential of the machine to significantly improve rice quality while remaining accessible to small-scale processors. The proposed design contributes to the development of affordable post-harvest technologies aimed at enhancing food safety and value chain efficiency in developing regions.