Detailed particle concentration distribution in dense solid-liquid suspension was measured by means of fiber optic probes. The effect of solid loading, impeller speed, and impeller type and clearance was investigated. Results were compared with modeling approaches to show the accuracy of sedimentation-dispersion model and its capability to describe complex phenomena taking place in dense liquid-solid mixing systems. Variation of power numbers by changing impeller clearance and solid loading were also investigated. It was shown that the impeller power number for a slurry system exhibited different trends in a moderate or dense liquid-solid system. In addition, scale-up rules to achieve the same level of homogeneity on a large scale as the laboratory scale were evaluated. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.