In the process of pneumatic separation, the aerodynamic properties of particles such as their critical velocity, are used. A pneumatic separator was designed that allowed a wide range of control parameters to be used. The essential factors affecting the course of the separation process were identified and a theoretical correlation between these factors and the separation efficiency were determined. The main aim of the study was to analyse the separation process in an air stream of broken lupine seeds, chiefly involving theoretical considerations of movement and behaviour of mixture particles in a pneumatic canal. Investigations and observations gave ground for an attempt at deriving a movement equation of particles in an unrestrained, uniform air stream. The equations obtained can be used for calculating the parameters of particle movement in pneumatic canals. The velocities of air stream, then, can be a few times higher than the critical velocity/convection/of individual particles. While working out the above problems the following points were considered: on the one hand, possibilities of obtaining the greatest outcome from the separation process and on the other, reducing the losses of valuable material in the discarded lot to a maximum. (C) 2011 Elsevier Ltd. All rights reserved.