Abstract
Particle dispersion in a shear-thinning fluid in a stirred vessel with a turbine blade impeller has been investigated experimentally. An aqueous solution of carboxymethylcellulose (CMC) is used as a non-Newtonian fluid having a weak shear-thinning rheological property. Initially, polymethylmethacrylate (PMMA) fine particles of 8–20 µm are inserted just below the surface of stationary fluid. Complete dispersion time is defined as the time when no large-scale lumps can be found. At the same time, PMMA particles adsorb on the surface of micron-sized air bubbles accompanied with the initial input of the particles. With proceeding of particle dispersion, particles desorb from the bubble surface, and the average size of bubbles with PMMA particles decreases. To find an optimized operational condition for mixing, the dispersion process is divided into macroscopic and microscopic. For macroscopic dispersion, high rotation speed is required, but it should be kept low enough so that it does not create a cylindrically rotating zone. Low rotation speed is favored to purge air bubbles with accumulated particles for microscopic dispersion.
