Investigation of an external loop airlift slurry separator for precise grading of solid particles

Powder with a narrow or extremely narrow particle size distribution is highly desired in many industries, while precise grading of solid particles remains a technical challenge. A theory for precise grading was proposed, and a piece of grading equipment was designed and verified for simultaneous and continuous separation of two kinds of target particles by combining the superb particle pre-dispersion in an external loop airlift slurry separator with the precise sieving process. The grading accuracy of small particles in fine products with irregular shapes was close to 90%, and that of large particles in coarse products reached up to 94.5%. The effects of superficial gas velocity and siphon flow rate on the hydrodynamic characteristics, solid concentration distribution, grading accuracy, particle yield, and grading efficiency were systematically investigated, and new thoughts for the appropriate design, optimization, and scale-up of such precise grading equipment were provided.