This paper introduces a systematic method based on periodic dynamic optimization for an integrated conceptual design of the major equipment and operational parameters of stirred tank reactors. To identify the preferred mode of operation for a given reaction system, equipment and operational parameters are optimized simultaneously. The approach presented is motivated by the observation, that stirred tank reactors operated in batch, semi-batch, continuous, or even periodically forced mode can be subsumed by a single optimization model with periodicity constraints and suitably chosen model equations and decision variables. The advantages of the suggested design method are twofold. It overcomes on the one hand the intrinsic disadvantages of rules of thumb which are usually based only on simple reaction mechanisms to select a particular reactor type. On the other hand the approach results in optimal operational strategies for the preferred mode of operation minimizing an economical objective function.