Mixing effects in a continuous flow stirred tank reactor

Abstract

Nonideal behaviour of a continuous flow stirred tank reactor was investigated by observed the transient response of the reactor to negative step changes in feed concentration. It was shown that turbulence by inlet only is sufficient for perfect mixing provided that the tank Reynolds number exceeds 17. For the tank Reynolds number below 17, mechanical stirring was necessary and the Reynolds number as follows $$Re_m =540 \ln \Bigg(\frac{17}{Re_t}\Bigg)$$ It was also found that more bypassing effects exist when the feedline and effluent line were placed at closer liquid levels. For the nonideal flows, several mixed models described the flow patterns, namely bypassing and dead space model, CSTR and PER in series model and dead space model. Segregation effects in a second order reaction were also experimentally determined. It was confirmed that segregation yields higher conversion in the second order reaction. In the ideally mixed region, the performance of the reactor decreased with an increase in rpm.