INFLUENCE OF DESIGN AND OPERATING PARAMETERS ON SEPARATING THE COARSE WHEAT BRAN BY CYCLONE

Abstract

Experimental study and predicted models were used to investigate the effect of cyclone geometry and operating parameters such as cone height (30, 50 and 70 cm), vortex finder length (0, 10, 20, 30 and 40 cm), dipleg length (25, 40 and 55 cm) and inlet air velocity (14, 16, 18 and 20 m/s) on separating the coarse wheat bran from air stream. The performance parameters via cut-off diameter (d50), overall collection efficiency (ηo) and pressure drop (ΔP) were evaluated to determine the appropriate design of the cyclone under local operating conditions. The results showed that, ΔP increased with the increase of inlet air velocity and cone height. The optimum operating and design parameters at cone height of 70 cm were inlet air velocity 14 m/s and vortex finder length 40 cm, which lead to high ηo 99.93 % and low ΔP 80.63 Pa. While at cone height of 50 cm, the optimum operating and design parameters were: inlet air velocity 18 m/s under vortex finder length 40 cm which lead to high ηo 99.97 % and low ΔP 121.52 Pa. whereas the cone height 30 cm and vortex finder length zero cm were undesirable because they have low ηo. The d50 decreased with increase inlet air velocity and lead to increase ηo; for instance at cone height of 30 cm the d50 of Lapple model were 31.95, 29.88, 28.17 and 26.73 µm for coarse wheat bran at inlet air velocity 14, 16, 18 and 20 m/s, respectively. Moreover the statistical indicators presented that the Hoffmann & Stein model was the best model and more validation to predict coarse wheat bran ηo at cone height 30 and 50 cm. The Lapple model was the best model and more validation to predict coarse wheat bran ηo at cone height 70 cm. There is a wide range of the optimum ηo depend on the design, operating parameters and the price of the separated material and this is subject to the operator's decision; in other words balancing operating economics cost and the price of the separated material.