ABSTRACT
This chapter presents a basic characterization of residence time distributions (RTDs). If the reactor is a plug flow one, arbitrarily chosen cross-section will be of the same age. All volume elements would have thus reached the same age once they leave the reactor. In reactors with some degree of backmixing, and there is always a distribution of the residence times of the volume elements. The largest possible distribution of residence times is found in continuous stirred tank reactors, in which the residence times of individual volume elements are spread throughout the time frame, from zero to infinity. A plug flow reactor can serve as the initial starting point for further analysis and for study of the reasons for the deviations from the initial state in which the reactor is assumed to reside. In reactors equipped with a stirrer, it is possible to create an RTD that ranges from one close to a plug flow to almost complete backmixing.
