DEVELOPMENT OF SOLID-LIQUID MIXING MODELS USING TOMOGRAPHIC TECHNIQUES

The need for tomographic technology to assist in the development of re liable correlations for scale-up of slurry mixing processes is describ ed. In situ measurements of the axial and radial solid concentration p rofiles and vector velocities of particulates are required which indic ate the effect of mixing impeller geometry, mixing speed, solid concen tration and size distribution of solids on mixing performance. The cur rent status of tomographic techniques that could be suited for these a pplications is assessed. Recent results obtained using the two methods of electrical resistance tomography (ERT) and positron emission tomog raphy (PET) are described together with complementary measurements per formed using an invasive single point conductivity probe. The effect o f particle size on the ''just suspension speed'' N-js, as determined f rom conductivity measurements, was compared with the Zweitering correl ation (Th. N. Zweitering, Chem. Eng. Sci., 8 (1958) 244-253). Good agr eement was obtained. The principle of using data derived from conventi onal probes and three-dimensional tomograms to yield mixing indices fo r control decision making is described.