When and how is dynamic simulation used in process design?

Dynamic simulation models time-dependent behavior. Applications: Control system design - tune controllers, test cascade/feedforward strategies before commissioning. Startup/shutdown - develop procedures, identify constraints and timing. Relief system verification - confirm transient loads don't exceed relief capacity. Safety system testing - verify ESD logic and timing. Training simulators - operator training on realistic model. Upset analysis - evaluate system response to disturbances. Debottlenecking - identify dynamic limitations. Tools: Aspen Dynamics, HYSYS Dynamics, gPROMS. Considerations: requires good steady-state model first, need equipment volumes and dynamics, control system details, and validated against plant where possible. More effort than steady-state but essential for complex or safety-critical applications.