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Dynamic optimization of constrained semi-batch processes using Pontryagin's minimum principle An effective quasi-Newton approach

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COMPUTERS & CHEMICAL ENGINEERING 2017年 99卷 135-144页

作者： Aydin, Erdal Bonvin, Dominique Sundmacher, Kai Max Planck Inst Dynam Complex Tech Syst Sandtorstr 1 D-39106 Magdeburg Germany Ecole Polytech Fed Lausanne Lab Automat CH-1015 Lausanne Switzerland Otto von Guericke Univ Univ Pl 2 D-39106 Magdeburg Germany

This work considers the numerical optimization of constrained batch and semi-batch processes, for which direct as well as indirect methods exist. Direct methods are often the methods of choice, but they exhibit certain limitations related to the compromise between feasibility and computational burden. Indirect methods, such as Pontryagin's Minimum Principle (PMP), reformulate the optimization problem. The main solution technique is the shooting method, which however often leads to convergence problems and instabilities caused by the integration of the co-state equations forward in time. This study presents an alternative indirect solution technique. Instead of integrating the states and co-states simultaneously forward in time, the proposed algorithm parameterizes the inputs, and integrates the state equations forward in time and the co-state equations backward in time, thereby leading to a gradient-based optimization approach. Constraints are handled by indirect adjoining to the Hamiltonian function, which allows meeting the active constraints explicitly at every iteration step. The performance of the solution strategy is compared to direct methods through three different case studies. The results show that the proposed PMP-based quasi-Newton strategy is effective in dealing with complicated constraints and is quite competitive computationally. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Constrained dynamic optimization Pontryagin's minimum principle Indirect optimization methods Quasi-Newton algorithm semi-batch processes

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Industrial experiences with product quality control in semi-batch processes

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COMPUTERS & CHEMICAL ENGINEERING 2002年第2期26卷 205-212页

作者： Yabuki, Y Nagasawa, T MacGregor, JF Mitsubishi Chem Corp Yokaichi Mie Japan McMaster Univ Dept Chem Engn Hamilton ON L8S 4L7 Canada

Two practical approaches to the control of final product quality in semi-batch reactors are illustrated with industrial experiences. The first is an orthodox approach to the control of final quality that is achieved through a high degree of automation of all the reactor charging operations, good temperature and pressure control, and the precise sequencing of steps implemented throughout the course of the batch. The second approach to the control of final quality is to use mid-course correction policies. Both approaches to the control of final quality are illustrated with an industrial example. Through our experience, the first approach, although very basic, is shown to be very important to reduce the variability in the final product quality. The second approach is useful to compensate for the new disturbances that are affecting the batch being run at the current time. Good practice is that mid-point control policies should be used after the basic automation step has been implemented as efficiently as possible. (C) 2002 Elsevier Science Ltd. All rights reserved.

关键词： batch processes semi-batch processes quality control industrial practice

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Industrial experiences with product quality control in semi-batch processes

Industrial experiences with product quality control in semi-...

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7th International Symposium on Process Systems Engineering

作者： Yabuki, Y Nagasawa, T MacGregor, JF Mitsubishi Chem Corp Yokaichi Mie Japan McMaster Univ Dept Chem Engn Hamilton ON L8S 4L7 Canada

关键词： batch processes semi-batch processes quality control industrial practice

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A Fault Detection and Diagnosis Strategy for batch/semi-batch processes

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CHEMICAL PRODUCT AND PROCESS MODELING 2010年第1期5卷

作者： Maulud, Abdulhalim Romagnoli, Jose Univ Teknol Petronas Teronoh Malaysia Louisiana State Univ Baton Rouge LA 70803 USA

This paper presents fault detection and diagnosis methodology for batch/semi-batch processes using a multi-way orthogonal nonlinear PCA approach. In this work, a sequential extracting process of linear and nonlinear correlations from process data is performed. The approach reduces the complexity of the nonlinear PCA model structure, which dramatically improves the model generalization. An orthogonal nonlinear PCA procedure is incorporated to capture the nonlinear characteristics with a minimum number of principal components. A trajectory-boundary-limit crossing point discriminant analysis is proposed to diagnose the process faults. A two-step discriminant analysis is also incorporated to improve the diagnostic performance in the case of isotropically distributed trajectories. The validity of the proposed strategy is demonstrated by the application to an emulsion copolymerization of styrene/MMA semi-batch process.

关键词： process monitoring neural networks semi-batch processes

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Realization of online optimizing control in an industrial semi-batch polymerization

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JOURNAL OF PROCESS CONTROL 2014年第2期24卷 399-414页

作者： Finkler, Tiago F. Kawohl, Michael Piechottka, Uwe Engell, Sebastian Tech Univ Dortmund Proc Dynam & Operat Grp Dortmund Germany Evonik Ind AG Essen Germany

In this work, the realization of an online optimizing control scheme for an industrial semi-batch polymerization reactor is discussed in detail. The goal of the work is the automatic minimization of the duration of the batch without violating the tight constraints for the product specification which translate into stringent temperature control requirements for a highly exothermic reaction. Crucial factors for a successful industrial implementation of the control scheme are the development and the validation of a process model that is suitable for process optimization purposes and the estimation of unmeasured process states and the online compensation of model uncertainties. Two implementations are proposed, a direct online optimizing control scheme and a simplified scheme that combines a model-predictive temperature controller and a monomer feed controller that steers the cooling power to a predefined value in a cascaded fashion. We show by simulation results with a validated process model that both schemes achieve the goals of tight temperature control and reduction of the batch time. The performance of the NMPC controller is superior, on the other hand the cascaded scheme could be directly implemented into the DCS of the plant and is in daily operation while the online optimizing scheme requires an additional computer and is currently in the test phase. (C) 2013 Elsevier Ltd. All rights reserved,

关键词： Model based control Nonlinear control Optimizing control Polymerization control semi-batch processes

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NMPC using Pontryagin's Minimum Principle-Application to a two-phase semi-batch hydroformylation reactor under uncertainty

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COMPUTERS & CHEMICAL ENGINEERING 2018年 108卷 47-56页

作者： Aydin, Erdal Bonvin, Dominique Sundmacher, Kai Max Planck Inst Dynam Complex Tech Syst Sandtorstr 1 D-39106 Magdeburg Germany Int Max Planck Res Sch IMPRS Adv Methods Proc & S Magdeburg Germany Ecole Polytech Fed Lausanne Lab Automat CH-1015 Lausanne Switzerland Otto von Guericke Univ Univ Pl 2 D-39106 Magdeburg Germany

Nonlinear model predictive control (NMPC) is an important tool for the real-time optimization of batch and semi-batch processes. Direct methods are often the methods of choice to solve the corresponding optimal control problems, in particular for large-scale problems. However, the matrix factorizations associated with large prediction horizons can be computationally demanding. In contrast, indirect methods can be competitive for smaller-scale problems. Furthermore, the interplay between states and co-states in the context of Pontryagin's Minimum Principle (PMP) might turn out to be computationally quite efficient. This work proposes to use an indirect solution technique in the context of shrinking-horizon NMPC. In particular, the technique deals with path constraints via indirect adjoining, which allows meeting active path constraints explicitly at each iteration. Uncertainties are handled by the introduction of time-varying backoff terms for the path constraints. The resulting NMPC algorithm is applied to a two-phase semi-batch reactor for the hydroformylation of 1-dodecene in the presence of uncertainty, and its performance is compared to that of NMPC that uses a direct simultaneous optimization method. The results show that the proposed algorithm (i) can enforce feasible operation for different uncertainty realizations both within batch or from batch to batch, and (ii) is significantly faster than direct simultaneous NMPC, especially at the beginning of the batch. In addition, a modification of the PMP-based NMPC scheme is proposed to enforce active constraints via tracking. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Nonlinear model predictive control Indirect optimization methods Indirect adjoining semi-batch processes Pontryagin's Minimum Principle

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An in silico evaluation of data-driven optimization of biopharmaceutical processes

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AICHE JOURNAL 2017年第7期63卷 2796-2805页

作者： Wang, Zhenyu Georgakis, Christos Tufts Univ Inst Chem & Biol Proc Dept Chem & Biol Engn & Syst Res Medford MA 02155 USA

Two methodological improvements of the design of dynamic experiments (C. Georgakis, Ind Eng Chem Res. 2013) for the modeling and optimization of (semi-) batch processes are proposed. Their effectiveness is evaluated in two representative classes of biopharmaceutical processes. First, we incorporate prior process knowledge in the design of the experiments. Many batch processes and, in particular, biopharmaceutical processes are usually not understood completely to enable the development of an accurate knowledge-driven model. However, partial process knowledge is often available and should not be ignored. We demonstrate here how to incorporate such knowledge. Second, we introduce an evolutionary modeling and optimization approach to minimize the initial number of experiments in the face of budgetary and time constraints. The proposed approach starts with the estimation of only a linear Response Surface Model, which requires the minimum number of experiments. Accounting for the model's uncertainty, the proposed approach calculates a process optimum that meets a maximum uncertainty constraint. (c) 2017 American Institute of Chemical Engineers AIChE J, 63: 2796-2805, 2017

关键词： pharmaceutical and biopharmaceutical processes optimization design of experiments semi-batch processes

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Transfer of semibatch processes to Continuous processes with Side InjectionsOpportunities and Limitations

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MACROMOLECULAR REACTION ENGINEERING 2016年第4期10卷 364-388页

作者： Goerke, Thilo Kohlmann, Daniel Engell, Sebastian Tech Univ Dortmund Proc Dynam & Operat Grp Emil Figge Str 70 D-44227 Dortmund Germany

The transfer of copolymerization processes from discontinuous plants to continuous plants has become a topic of industrial interest in the recent years. The motivations for such a transfer are better product consistency, smaller capital investment, and smaller footprint of the plants. However the experiences of the F3 project show that some copolymerization processes cannot be transferred to continuous production if the product quality must remain the same because in a continuous reactor, feeds can be added only at certain points along the reactor. This paper discusses the transferability of semibatch polymerization processes to a continuous plug-flow reactor with side injections in a generic fashion. Transferability of a semibatch recipe here means the possibility of the production of the same product in both modes of operation (semibatch and continuous). To determine the limits of the transferability from semibatch to continuous production, a model-based analysis has been performed based on a simplified kinetic model and realistic kinetic parameters. The ranges of product qualities that can be produced in both modes of operation and the minimum changes in the product qualities, if no 1:1 transfer is possible are determined by means of model-based optimization. Besides the numerical results, also an analytical treatment is presented. This provides a sound basis for an analysis of the transferability from a kinetic and an economic point of view.

关键词： copolymerization free radical polymerization semi-batch processes tubular reactors transfer batch to continuous

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A roadmap for in silico development and evaluation of industrial NMPC applications: A practical case study

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COMPUTERS & CHEMICAL ENGINEERING 2021年 150卷

作者： Morandi, Santiago Nimmegeers, Philippe Schwind, Markus Di Pretoro, Alessandro Manenti, Flavio Logist, Filip BASF Antwerpen NV Antwerp Belgium Politecn Milan Dipartimento Chim Mat & Ingn Chim Giulio Natta SuPER Sustainable Proc Engn Res Team Milan Italy

Linear Model Predictive Control (MPC) can be considered as the state of the art advanced process con-trol technology in model-based automation of continuous chemical processes. For (semi-)batch processes, that often present a strongly nonlinear (or even unstable) behavior in combination with fast dynamics, Nonlinear Model Predictive Control (NMPC) is a more suited technology. However, online applications of NMPC have a hard time to penetrate in industry despite methodological developments, tools and exam-ples in academia. In this paper, we propose a roadmap to argue against the intrinsic reasons and practical limitations that slow down the practical online applications of NMPC. This roadmap is applied to an ex -isting semi-batch plant as a practical case study. The results have shown that the NMPC algorithm can provide an improved control, namely a better tracking of the main process variables, a reduction in the reaction time, and robustness with respect to model-plant mismatch and disturbances. (c) 2021 Elsevier Ltd. All rights reserved.

关键词： Nonlinear model predictive control Potential evaluation semi-batch processes Process control

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