Design improvement and performance evaluation of an air-screen rice cleaning and de-stoning machine

Abstract

This work designed, developed, and evaluated a modified rice cleaning and de-stoning machine based on differential densities and sizes. Unlike traditional horizontal sieves used in most de-stoners, this design adopted the Pedal Operated Seed Cleaner (PoS-Cleaner) which uses rotary sieves with enhancements like a vacuum blower, fractionating unit, and rotary screen with three apertures. Testing focused on Impurity Level (IML), Rice Separation Efficiency (RSE), Stone Separation Efficiency (SSE), Tray Losses (TL), and Chaff Separation Efficiency (CSE). Powered by a 3.5hp motor at 940 rpm, it was tested with rice-to-impurity ratios of 25:3, 20:3, and 15:3, and feed gate openings of 5mm, 10mm, and 15mm. Results showed RSE, SSE, and CSE decrease with larger feed gate openings and less rice mass, while IML and TL increase. While the PoS-Cleaner achieved high cleaning efficiencies for maize (95.09%), beans (87.61%), and groundnuts (81.67%), the modified rice cleaner achieved an RSE of 88.35%, SSE of 79.67%, and CSE of 89.55% at a 25:3 ratio and 5mm opening. Future improvements could include variable speed devices for blowers and sieves.