Unconventional configuration studies to improve mixing times in stirred tanks

Dynamic perturbations and off-centered single and dual mixing impeller configurations have been investigated to reduce mixing time with viscous fluids. Mixing times, measured with a color-discoloration technique based on a fast acid-base reaction, reveal the presence of both segregated and dead zones A statistical design approach has been used to evaluate the effect of the impeller position as well as the dynamic conditions. Homogenization, is significantly enhanced when a radial flow impeller is used under both off-centered and dynamic perturbation conditions. In the case of an axial flow impeller, a combination of long clockwise times and short counter-clockwise times give better mixing, times. An enhanced homogenization is also observed-when a dual impeller configuration is used.