Pneumatic conveying characteristics of some agricultural seeds

In this research, a positive low pressure pneumatic conveyor was designed and manufactured and conveying characteristics of the seeds of wheat (Triticum durum), barley (Hordeum vulgare), sunflower (Helianthus annuusl) and lentil (Lens culinaris) were determined. In addition, the mechanical damage, germination rate, and vigour index of the seeds were also investigated experimentally. Wheat had the highest sphericity (55.06%), while barley had the lowest sphericity (46.10%). The volumes of wheat, barley, sunflower, and lentil were 35.76 mm3, 38.37 mm3, 71.29 mm3, and 39.76 mm3, respectively. The one thousand seed mass values of wheat, barley, sunflower, and lentil were found as 47.38 g, 38.18 g, 57.80 g, and 56.54 g, respectively. The bulk and true densities for wheat, barley, sunflower, and lentil were obtained as 815–1325 kg/m3, 684–995 kg/m3, 427–711 kg/m3, and 777–1422 kg/m3, respectively. The maximum porosity was obtained as 45.36% for lentil, while the lowest (31.25%) was obtained for barley. The projection areas of wheat, barley, sunflower, and lentil were found 14.70 mm2, 25.10 mm2, 61.49 mm2, and 27.70 mm2, respectively. The terminal velocities for wheat, barley, sunflower, and lentil varied from 9.86 to 10.27 m/s, 7.44 to 8.25 m/s, 6.13 to 6.61 m/s, and 6.99 to 7.72 m/s, respectively. The drag coefficients of wheat, barley, sunflower, and lentil varied within the 0.490–0.532, 0.359–0.441, 0.345–0.401, and 0.549–0.670, respectively. When air alone was blown, the pressure drop and the power requirement increased with the air velocity. The highest pressure drop and power requirement were obtained from wheat conveying, while the lower pressure drop and power requirement were on sunflower. The pressure drop and the power required to convey all seeds through pipe line for all seeds rose with air velocity and conveying capacity. The danger of mechanical damage for all seeds increased with increasing air velocity. The lowest mechanical damage was found for wheat, while the highest was for lentil. Germination and vigour index decreased when the conveying velocity increased. The maximum loss of germination was obtained for sunflower, while the minimum loss of germination was for wheat. But a higher loss of vigour index occurred in wheat, while sunflower had the minimum vigour index loss.