Abstract：In order to avoid large area slugging of solids particles and conveying efficiency decreasing when the solid level arrived at critical level value, a open type pneumatic conveying system was designed and built up according to the theory of similarity and the large scale cement steel silo structure of a cement plant which lied in Juxian, Shandong province. In this system, pneumatic conveying experiments were carried out which compressed gas taking along cement powder. The results show that in process of pneumatic conveying, with the decrease of solid level the mass flow ratio and pressure drop increase first and then decrease. The solid level of inflection point on the trend curve is defined as critical solid level. Meanwhile, with increase of gas velocity and the solids loading ratio, the critical solid level decreases。

Keywords: positive pressure open type; pneumatic conveying; critical solid level; flow parameter