Selecting the type and rotation speed of a mixer for efficient mixing of flocculants in water

Abstract

Introduction. The paper addresses the physico-chemical process of dissolving the particles of solid high molecular weight powder flocculant in water under the action of a centrifugal field generated as a result of mixer operation. Methods. The authors describe equipment and methods to conduct experimental research in laboratory conditions and present an experimental setup used to prepare a concentrated flocculant solution, consisting of a mixer and a cylindrical glass container. Results. It is shown that the selection of the optimal mixer rotation speed is associated with the magnitude of turbulent friction stresses generated by the mixer impeller. A method to calculate the permissible rotation speed of a mixer based on a semi-empirical Prandtl turbulence model has been developed and tested. The paper presents the results of experimental studies on the preparation of concentrated solutions of high molecular weight cationic flocculant GreenLife K40 using various types of mixer impellers. Conclusion. The authors have experimentally demonstrated the efficiency of a new conical impeller compared to standard blade and turbine impellers due to smaller turbulent eddies breaking polymer bonds in a concentrated flocculant solution. A mixer with a conical impeller makes it possible to prepare a flocculant solution 30% faster due to the possibility of mixing at a higher speed with lower energy consumption.