Abstract We deal with the real-time production scheduling of a continuous-process multi-grade PET resin plant. The process is surcharged by sequence-dependent changeovers, sequential processing with production and space capacity, and mixed and flexible finite intermediate storage. The management called us to develop a time responsive production scheduling tool that copes with demand uncertainty, urgent orders and increased lead times. We adopt simulation as a methodology approach and create a tool based on tangible control rules and simple production engineering methods that make dynamic analysis tractable. Our goal is to maximize the aggregate fill rate, taking into consideration the number of required equipment transitions which cause undesirable variations in base resin properties. The model is tested under a real-world six-month demand instance and ten other hypothetical scenarios. The results are compared with those of the optimal solution derived from a preexisting Mixed Integer Linear Programming model that considers short-term demand as known.