Flow Properties of Awned and De-Awned Paddy Grains Through a Horizontal Hopper Orifice

In a modern rice mill, de-awning is an important process before husking operation to eliminate awns of the paddy grains for easy conveying in the elevators, chutes, and hopper orifices. This experiment was conducted to study the effects of independent variables of de-awning percentage, orifice cross-sectional area and paddy grains moisture content on the flowing rate (FR) and variations of flowing rate (VFR) of paddy grains through a horizontal hopper orifice. A local paddy variety, namely, Hashemi, which is characterized by long awns was used as a raw material in the test. The results indicated that flow rate (FR) and variations on flow rate (VFR) significantly (p < 0.01) affected by the de-awning percentage, orifice cross-sectional area and paddy moisture content. FR increased from 45.00 to 87.57 g s(-1) and VFR decreased from 54.93 to 21.49%, as de-awning increased from 14.67 to 84.93%. FR increased as the orifice cross-sectional area increased from 12.08 to 34.81 cm(2); however, higher VFR was obtained at lower orifice cross-sectional area. For the awned (87% of the grains had originally awns) and de-awned paddy (82% of the grains were de-awned), FR decreased as the paddy moisture content increased from 8.67 to 15.06%wb; while VFR increased at higher grain moisture content.