Development of a Centrifugal Rice Grain Sorting Machine

Abstract

This research focuses on the development of a rice grain sorting machine intended to remove contamination from rice after the milling process in small rice mills in rural areas. The machine operates on the concepts of centrifugal force and size sorting and utilises a series of nested sieves inside a circular tank. The sorting mechanism contains Sieve A, which separates impurities larger than rice grains; Sieve B, which sorts whole rice grains; Sieve C, which differentiates broken rice grains; and Sieve D, which collects broken rice and weed seeds that are smaller than broken rice grains. The study examined three factors: 1) pouring angle of the separation tank at 2°, 3°, and 4°; 2) tank rotational speeds at 15, 20, and 25 rpm; and 3) rice types, including jasmine and glutinous rice. Each experimental condition was replicated three times. Results showed that at a 2° angle, rice flows slowly, allowing more sorting time; at 15 rpm, low impact force reduces grain breakage, and jasmine rice sorts better than glutinous rice due to shape and size differences. Optimal conditions are a 2° pouring angle and 15 rpm rotational speed, providing separation efficiency of 95.5% for jasmine rice and 94.0% for glutinous rice, respectively.