Experimental study on collision characteristics of large coal particles (7–15 mm) in 90° elbows of pneumatic conveying systems

Pneumatic conveying of coal particles widely used for environmental friendliness and automation. In this study, orthogonal experiments were carried out in 90° elbows of large coal particles (7–15 mm) to study the effect of the elbow shape, particle size, airflow velocity, and gas supply pressure on elbow erosion. Elbows with double-layer wall structures were designed to present the erosion characteristics, particle breakage ratio, and pressure drop. Results indicate that the angle between the erosion center and the tangential direction of the elbow inlet is approximately 25°–30°. The elbow shape and airflow velocity have significant effects on all three evaluation indices, whereas the particle size and gas supply pressure have significant effects on the pressure drop. The optimal parameters of each factor were confirmed: the blind elbow with a plug, particle size of 9–11 mm, airflow velocity of 20 m/s, and gas supply pressure of 0.4 MPa.