Model-based supervisory control structure for plantwide control of a reactor-separator-recycle plant

Abstract

This work presents a methodology for designing a supervisory control structure in plantwide control (PWC). First, available PWC structures are discussed focusing on their drawbacks originating from the scarce flexibility and simplicity when implementing them in industrial environments. To overcome this, a hierarchical approach to PWC is proposed that introduces a two-layer control structure, where the regulatory layer dynamics are classified by hierarchical association and their set points are optimized on the supervisory layer to achieve collaboration among proportional-integral-derivative (PID) controllers. Here, the dynamics hierarchy is established by means of the process Hankel matrix that quantifies the effect of all input variables over each state variable of the plant. Finally, the proposed methodology is applied to a reactor-separator-recycle system for propylene glycol production, where a better process performance is reached using the hierarchical approach in comparison with a decentralized control structure.