Studies in the synthesis of control structures for chemical processes: Part I: Formulation of the problem. Process decomposition and the classification of the control tasks. Analysis of the optimizing control structures

TLDR

The formulation is rigorous and free of engineering heuristics, providing a framework for generalizations and further analytical developments on this important problem. This paper presents a unified formulation of synthesizing control structures for chemical processes and examines optimizing control strategies, developing methods for their generation and selective screening. Decomposition underpins the approach, guiding the classification of regulation and optimization objectives, partitioning the process, and employing mathematical measures from hierarchical control and multi‑level optimization theory to define the extent and purpose of control tasks and generate alternative structures. The extent and purpose of regulatory and optimizing control objectives are clearly defined, alternative control structures are generated, and these principles are illustrated on an integrated chemical plant, yielding conclusions applicable to real‑life situations.

Abstract

Abstract Part I of this series presents a unified formulation of the problem of synthesizing control structures for chemical processes. The formulation is rigorous and free of engineering heuristics, providing the framework for generalizations and further analytical developments on this important problem. Decomposition is the underlying, guiding principle, leading to the classification of the control objectives (regulation, optimization) and the partitioning of the process for the practical implementation of the control structures. Within the framework of hierarchical control and multi‐level optimization theory, mathematical measures have been developed to guide the decomposition of the control tasks and the partitioning of the process. Consequently, the extent and the purpose of the regulatory and optimizing control objectives for a given plant are well defined, and alternative control structures can be generated for the designer's analysis and screening. In addition, in this first part we examine the features of various optimizing control strategies (feedforward, feedback; centralized, decentralized) and develop methods for their generation and selective screening. Application of all these principles is illustrated on an integrated chemical plant that offers enough variety and complexity to allow conclusions about a real‐life situation.