Abstract:
Rice is generally considered as semi aquatic annual plant that survives as perennial in the tropics
or subtropics. The high running cost in terms of electricity and fuel of the available rice milling
machine impacts the production of rice in large quantity. Additionally, the inability of these
available machines to de-stone and grade rice affects the quality of milled rice. Therefore, the main
objective of this study was to design, fabricate, and carryout performance evaluation of a solar-powered multi-stage rice processing machine. The machine was segmented into three units; de-stoning, milling, and grading unit.
The machine is powered by a 4kW 1400rpm motor via a V-belt which delivers power to the milling
unit on which the milling cylinder is mounted, and then the unit transfers power to other machine
units through belts. The milling cylinder presses the paddy rice against the sieve to remove husks
and bran and polish it. The machine has been designed to process 60kg/hr of rice for small scale
production.
Performance evaluation of the machine shows that its efficiency is within the range of 65-68% and
the maximum efficiency is at 3kg paddy rice hopper loading. The machine was tested in terms of
rice grading efficiency and the best efficiency of 72% was obtained at 6kg loading in the grading
cylinder, and the husk removal efficiency, stone separation efficiency, tray loss and impurity level
after separation were also analyzed. The result showed an average of 9.8%, 7.33%, 18.25% and
27.27% for husk removal, stone separation efficiency, tray loss and impurity after separation
respectively.
Keywords: De-stoning, Milling, Grading, Solar, Design.
