Determination of required mixing time in an agitated batch mixer using tracer technique

Abstract

The required mixing time in a standard configuration tank was measured using tracer technique both theradioactive and conductivity methods. The mixer was a flatbottom cylindrical vessel with 24 cm inside diameter and wasfilled with water up to a height of 24 cm. The majorparameters were : types of impeller (a 6 bladed openturbine, a 6 bladed disc turbine, and a 6 bladed 45 degreepitch turbine), rotation speeds of impeller (200 to 400rpm), positions of impeller (at 1/2 and 1/3 tank's diameterabove tank's bottom), and baffles. The results obtained from both methods showed the sametrend of required mixing time, but the conductivity methodshowed a little shorter required mixing time. There werethree combinations in which the shortest required mixingtime was obtained. They were mixers with 6 bladed openturbine located at 1/2 and 1/3 tank's diameter above tank'sbottom, at speed of 400 rpm, and with baffles installed. Theother was mixer with 6 bladed disc turbine located at 1/2tank's diameter above tank's bottom. Some additional works using radioactive tracertechnique in determining residence time of steady statecontinuous flow were conducted. Two systems were used forthe study, the continuous stirred tank and tubular vessel.