Design, Construction and Performance Evaluation of a Motorized Rice De-stoning Machine

Abstract

A motorized rice de-stoning machine was locally developed for separating stone pebbles from milled rice. Major component being the reciprocating screen coupled with the blower and the hopper. The stone separation is achieved by vertical oscillation of the reciprocating screen coupled with a suction – like air produced by the blower directly beneath the screen causing rice – mixture to float just above the screen and the stones are sucked up the reciprocating screen then discharged through the stone chute and the clean rice collected in opposite order. The de-stoning machine was designed to be powered by a high speed (2980 rpm) 1 hp electric motor. It was evaluated for its efficiencies in terms of rice separation and de-stoning, the tray loss and impurity level after separation were also evaluated. The highest de-stoning efficiency was recorded between 5 to 7 mm feed gatesas 99.75 % and the lowest was recorded at a feed gate of 20 mm as 82.5 %. The highest rice separation efficiency was recorded at 5 mm feed gate to be 98.89 % and the lowest of 93.33 % was at 20 mm. The highest values of impurity level and tray loss were recorded at 20 mm as 2.041 % and 6.67 % respectively, while it lowest values were recorded at 5 mm as 0.028 % and 1.11 % respectively. The capacity also increased as the feed gate increase.