John R. Richards

Measurement and Control of Polymerization Reactors

The measurement and control of polymerization reactors is very challenging due to the complexity of the physical mechanisms and polymerization kinetics. In these reactors many important variables, which are related to end-use polymer properties, cannot be measured on-line or can only be measured at low sampling frequencies. Furthermore, end-use polymer properties are related to the entire molecular weight, copolymer composition, sequence length, and branching distributions. This paper surveys the instrumentation technologies, which are of particular interest in polymerization reactors with emphasis on, for example, measurement of viscosity, composition, molecular weight, and particle size. This paper presents a hierarchical approach to the control system design and reviews traditional regulatory techniques as well as advanced control strategies for batch, semibatch, and continuous reactors. These approaches are illustrated by focusing on the control of a commercial multiproduct continuous emulsion polymerization reactor. Finally, the paper captures some of the trends in the polymer industry, which may impact future development in measurement and reactor control.

Process Control of Polymerization Reactors: An Industrial Perspective

ABSTRACTPolymerization reactors usually exhibit complex nonlinear dynamic behavior because of the complexity of the physicochemical interactions and the kinetics of the polymerization reactions. In these reactors many important variables, often related to end-use polymer properties, cannot be measured on-line or can only be measured at very low sampling frequencies. Furthermore, end-use polymer properties are usually related to the molecular weight and composition distributions in the polymerization reactor. Finally, the typical industrial polymer reactor is used to manufacture a variety of grades of the same basic product necessitating frequent startups, on-line transitions, and shutdowns.The approaches used by the authors to meet these challenges are illustrated, within the constraints of protecting proprietary information, by focusing on the modeling and control of a commercial multiproduct continuous emulsion copolymerization reactor. The development of fundamental process understanding captured in a ...

Feedforward and Feedback Control of a Copolymerization Reactor

This paper uses the detailed mathematical model for the solution copolymerization of vinyl acetate and methylmethacrylate in a continuous stirred tank reactor presented previously by Congalidis, Richards, and Ray (2). Kinetic parameters and reactor operating conditions are obtained from the open literature. The model is extended to include equipment to recycle unreacted monomers and solvent. This recycle stream introduces disturbances to the reactor feed, which perturb the polymer properties. A feedforward control strategy is proposed to counter these disturbances and its effectiveness is demonstrated using the model. In addition, the feedback strategy proposed previously by the authors is added to compensate for any unmeasured reactor disturbances.

Perspectives on industrial reactor control 2: An update from CPC 3

Abstract This paper will discuss the evolution of reactor control over the last 25 years within the DuPont Company and its subsidiaries. It will focus on high level trends in control philosophy, systems and approaches. These changes have been necessary in order to achieve higher rates, better yields, improved uptime and a more sustainable footprint. This paper is an update to an article that was presented twenty-five years ago at Chemical Process Control (CPC) 3. The main focus will be on the use of Model Predictive Control (MPC) for reactor processes.