Mixing Non-Newtonian Liquids

Mixing plays a vital role in many industries including the food, petroleum, pharmaceutical, and waste industries. Mixing generally involves a rotating impeller in a fluid-filled vessel. While Newtonian fluid behavior is well-characterized, comparatively little is known about the behavior of non-Newtonian fluids. These experimental procedures were developed in order to characterize the behavior of non-Newtonian fluids in mixing applications, using Xanthan gum as a model. The effects of shear rate, impeller type, and solution viscosity on blend time were explored. To accomplish this, Xanthan gum was mixed in a 1L bioreactor with a solution of salt, blue dye, and Xanthan gum. The conductivity of the solution was measured over time to determine the blend time, defined as the time required to first reach within 5% of the final solution conductivity. Blue dye served as a subjective method to confirm blend time.