A. Principle of pneumatic conveyance

Pneumatic conveyance is of great importance for the transport of grained and powdered materials, especially for short distances and in connection with heat exchange and mass transfer processes.

The physical principles involved are, however, very numerous. For this reason, only a few aspects of the phenomena will be treated here. A more exhaustive treatment of this principle of conveyance may be found in certain basic books (Brauer, 1971; Weber, 1974; Boothroyd, 1971; Soo, 1967; Zenz and Othmer, 1960; Leva, 1959).

(a) Pneumatic conveyance in vertical pipes

The principle of pneumatic conveyance may best be explained by referring to Figure 1 for the case of vertically upward movement. The weight of a solid particle F_W and its inertial force M_s d υ_s /dt have to be compensated by the drag force F_D and the force due to the pressure gradient V_s dp /dl, which are both opposite to the flow direction of the particle. To bring this about, the velocity of the fluid medium υ_g has to be greater than the free-fall velocity of the solid particle w_so.