A new apparatus for studying deagglomeration of powders is presented. In many powder technology applications, it is important to know how strongly particles are adhered to each other and to what degree the particle agglomerates break up in different gas flows. In the new apparatus powders are fed in a controlled way, using a low, continuous feeding rate, into a deagglomeration zone in the apparatus. In the deagglomeration zone the powder agglomerates meet a dispersing main gas flow such that all the agglomerates experience a controllable level of turbulence. The degree of deagglomeration is determined by measuring the particle size distribution downstream of the deagglomeration zone. Particle deposition in the system is minimized by feeding sheath air through porous walls into the deagglomeration zone. When a powder is tested with various dispersing main gas flow rates, the particle size distribution as a function of a flow rate characteristics, e.g. flow Reynolds number, can be obtained. Deagglomeration tests were carried out with a powder blend consisting of 140 μm glass spheres as carrier particles and 2.5 μm silica spheres attached to the carrier spheres. The feeding with the blend was constant (typically less than ± 5%). The degree of deagglomeration increased with increasing dispersing main gas flow. Tests were also carried out with three pharmaceutical powder blends. The deagglomeration potential of any powder with sufficient flowability in any adequate gas can be tested with the presented apparatus.
- Powder feeder
- Turbulent flow