(337e) Comparison of Mixing in Rocking Reactors and a Laboratory Dyeing Reactors

Common laboratory dyeing reactors used in the textile industry such as the Werner Mathis AG unit consist of stainless steel cylindrical canisters mounted on a carousel with a horizontal axis. Reactors are canted to the horizontal so that the reactant mixture in a canister circulates with each revolution. Mixing is driven by end-to-end flow as the canister revolves with movement of an air void from front to back to front. The mixing in a canister nearly mimics that in a rocking reactor. Intensity of mixing was determined experimentally by rate of dissolution of benzoic acid granules at 30⁰ C as a function of fill volumes of canister, amount of solute and rotation speed of the carousel. Increasing rotational speed of the reactor system increases mixing but with increasing fill volumes the mixing in canister decreases. For example, only 35% of benzoic acid charged at 4g is dissolved in 900 ml of water with a rotational rate of 25 rpm but 50% of benzoic acid is dissolved in 250 ml of water. As the volume increases in canister, potential energy contribution to mixing decrease as the change in height of center of mass decreases for volume of liquid in canister. Optimum volume for highest mixing is found to be one third of the volume of reactor with higher rotation speed. Results obtained are compared to those found by Temkin et al. for a rocking reactor in which he determines specific mixing power. This included the rocking amplitude and frequency for different degrees of filling of vessel.