In this work, a complex process with recycles, Tennessee Eastman Challenge Process, is studied to explore the operability for plants with recycles. A simplified process model is constructed to provide physical insight into the Eastman plantwide process. The results show that the composition distribution in the reactor (or the recycle flow rate) plays an important role in determining the optimal operating condition, i.e., achieving maximum one-pass conversion. The trajectory of these optimal operating points at different production rates is employed to construct the optimal operating policy (OOP). From the OOP, input multiplicity is observed for the plant with recycles. Therefore, care has to be taken in operating plants with recycles. The optimal operating policy also indicates an inherent constraint on the production rate imposed by the process, e.g., process constraint. However, the design of the control system may lead to an even more limited operability. Moreover, the OOP can be used to evaluate the appropriateness of the designed equipment. The results show that the recycle compressor is not adequately designed and, subsequently, leads to an even smaller operating range. A design procedure is summarized to analyze the process, control, and equipment design aspects of recycle processes. The results indicate that complex recycle processes can be analyzed in a systematic way and, more importantly, all these analyses are based on a rather simple process model in a transparent manner.