Abstract:
De-husking and winnowing are important post-harvest operations in a number of processes connected with the handling of raw rice paddy after harvest. Rice paddy grain after harvesting and threshing is covered by a hard and inedible surrounding husk. These husks need to be removed by de-husking and separated from the edible rice grains through winnowing before they can be
consumed. Traditional or manual de-husking and winnowing of rice paddy is usually time consuming, laborious, tedious, demands lot of patience often leading to considerable amount of loss of grain. In order to overcome this situation, it is very important to come up with cost effective/efficient machines that meets the need of rural rice farmers. Based on this, some engineering properties (physical, frictional and thermal) of two selected local rice varieties (faro 44 and faro 59) were determined at moisture content of 14% dry basis and used to design a Rice
paddy de-husking and winnowing machine at the Federal university of technology, Akure. Results obtained from the study indicated that there was no significant different between the faro 44 and 59 in terms of their physical and frictional properties. The thermal properties of the selected varieties were determined using the differential thermal Analyzer. Faro 59 variety had a specific
heat of 3.351 J/g/k and faro 44 variety had a specific heat of 2.741 J/g/k.
A simple rice paddy de-husker and winnower was developed and evaluated using locally available materials and evaluated with rice paddy; Faro 44 and Faro 59 (raw and parboiled) at a fixed moisture content of 14% dry basis, roller huller speed of 802 rpm at a speed ratio of 1.4:1 and an air velocity of 4.6m/s. The developed machine has a capacity of 10 kg and required 1.5hp motor
to operate it. The machine had the maximum mean throughput capacity of 22.52 kg/hr when hulling the Parboiled faro 44 rice paddy. Parboiled Faro 44 rice variety had the Maximum average dehulling coefficient, dehulling efficiency, percentage of head rice and the minimum average value of broken rice grain of 0.71, 60.13%, 86.92% and 13.07% respectively. It was also observed that the developed machine demonstrated a moderately high cleaning efficiency for the two selected rice varieties both raw and parboiled with very close margins. The raw faro 44 paddy showed the highest cleaning efficiency of 85.90%. The parboiled rice paddies had higher dehulling efficiencies and head rice yield compared to the un-parboiled or raw rice paddies.
