<scp>PI</scp> averaging level control in plantwide systems

Abstract This work evaluates P‐only and PI averaging level control (ALC) for a tanks‐in‐series recycle process, a basic model for the material balance dynamics in non‐reactive recycle systems. While P‐only ALC tuning for an isolated tank is directly applicable to the recycle system, PI ALC requires a systematic detuning procedure due to complex dynamics and flow amplification down the tank cascade. The developed procedure ensures small flow amplification and full surge capacity utilization under worst‐case disturbances. The tuned PI ALC system achieves noticeably lower stop‐band frequency for recycle flow compared to P‐only ALC. A refined surrogate model is used to apply PI ALC to a three‐column azeotropic separation process, showing significant high‐frequency variability attenuation, though with mild flow amplification around a low‐frequency resonance peak. The work suggests that despite literature recommendations to the contrary, PI LC that removes level offset, benefiting operators, can be applied in plantwide systems, if tuned systematically.