Vertical pneumatic conveying: a flow regime diagram and a review of choking versus non-choking systems

For vertical pneumatic conveying of granular solids, a flow chart describing two different types of gas—solid systems, viz. the choking system and the non-choking system, is presented. Published equations for the prediction of whether a particular gas—solid tube system is of the choking type or non-choking type are reviewed. For the choking type system, a quantitative flow regime diagram for predicting demarcation between packed bed conveying and slugging dense phase conveying, and demarcation between slugging dense phase conveying and lean phase conveying, is developed in terms of the key parameters of loading ratio, gas and solid velocities. The usefulnes of the flow regime diagram in design is discussed. The shortcomings of an earlier flow regime diagram proposed by Leung 14] are overcome in the present diagram.