Nowadays building material industry as well as other industry branches exercise bigger demand to use powders with high dispersion. Jet mills are used to produce such powders that is why development of new jet mill designs, increase of grind efficiency, reduction of specific energy consumption is an important objective. This article provides a mathematic description of the two-phase flow motion at the outlet of the vertical acceleration tube of a jet mill with a plane grinding chamber of torus shape. The part of the acceleration tube above the impact plate is essential for grinding, as the initial particle grind occurs at this very section, in the grind chamber. Moreover, the initial grind defines the size of particles, that are further reground at the mill chamber. As a result of theoretical calculations, a formula is obtained that allows to determine the height of the acceleration tube from the bump element at the specified speed parameters of the two-phase flow. The article also contains the graph, that shows how particle velocity depends on the current (specific) height point (value) of the acceleration tube. This graph demonstrates that particle size strongly affects the way they move in the grind chamber. The formula allows to calculate the effective propulsion range of particles, depending on theirs' size, by presuming they have the maximum velocity
Numerical integration of the contravariant form of the two phase flow motion equations