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Transient dynamics and control of indium phosphide LEC furnaces

MATERIALS CHEMISTRY AND PHYSICS 2000年第2-3期66卷 236-245页

作者： Masi, M Carrà, S Polli, M Ratti, M Guadalupi, G Politecn Milan Dip Chim Fis Appl I-20131 Milan Italy Venezia Technol I-30175 Porto Marghera Italy

A transient 1D model was developed for simulating the dynamics of Liquid encapsulated Czochralski (LEC) growth processes. The model considers a melt-solid flat interface and a uniform temperature within the four phases (i.e., air, melt, solid and encapsulant) and predicts the crystal shape evolution during growth given the time histories of the heater temperature and of the pull rate. The model predictions were satisfactorily compared with experimental InP LEC dynamic growth data. Then, a feedback-feedforward control algorithm effective to achieve a cylindrical growth of single crystals in LEC systems was developed. In particular, the model to be used in the feedforward step was derived linearizing the above dynamic model. The controller keeps the crystal radius constant by acting on the heater, taking as input variables heater and air temperature, crystal weight, seed and crucible position. controller performances have been tested on a transient model of LEC process as controlled system. (C) 2000 Elsevier Science S.A. All rights reserved.

关键词： InP liquid encapsulated Czochralski dynamics control modeling

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Dynamic modeling and classical control theory for supply chain management

Dynamic modeling and classical control theory for supply cha...

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7th International symposium on process systems Engineering

作者： Perea, E Grossmann, I Ydstie, E Tahmassebi, T Carnegie Mellon Univ Dept Chem Engn Pittsburgh PA 15213 USA Unilever Res Port Sunlight Lab Wirral L63 3JW Merseyside England

This study proposes a novel dynamic approach for supply chain management based on the development of a dynamic framework to model supply chains, and on the application of ideas from process dynamics and control to manage it. This novel framework models the flow of information and material within the supply chain, and uses them to capture its dynamic behavior. Moreover, the use of ideas from dynamics and control allows the design of systematic decision-making processes for the supply chain as if they were control laws for a dynamic system. The study tests several heuristic control laws for the model and analyzes their impact on the behavior of the supply chain. The result is the reproduction of interesting trade offs found in real systems, which give valuable insights for the future direction of this research towards finding a near optimal decision-making process for a supply chain. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： supply chain management dynamics control hybrid systems

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An RT-Linux based control system of a pilot plant for reaction kinetics and process control studies

An RT-Linux based control system of a pilot plant for reacti...

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7th International symposium on process systems Engineering

作者： Romanenko, A Castro, JAAM Univ Coimbra Dept Chem Engn P-3030 Coimbra Portugal

The pilot plant under study is designed for determining the kinetics of the heterogeneous non-catalytic reaction of chemical pulping of wood and for teaching system dynamics and batch process control in an appropriate university course. The natural complexity of the system includes time varying dynamics and stepwise behavior and this makes it attractive for highlighting some important features of the real world of process control. Due to its specific design, the pilot plant is also very useful for kinetic studies of heterogeneous reactions involving wood, ensuring a high level of the repeatability of results. The pilot plant and its control system have been used in teaching of chemical kinetics of heterogeneous reactions and are also part of the experimental program in a process control course. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： process control pulping kinetics real-time operating system experimental process control education

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Partial least squares (PLS) based monitoring and control of batch digesters

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JOURNAL OF process control 2000年第2-3期10卷 229-236页

作者： Kesavan, P Lee, JH Saucedo, V Krishnagopalan, GA Auburn Univ Dept Chem Engn Auburn AL 36849 USA

In this paper, a data-based control method for reducing product quality variations in batch pulp digesters is presented. Compared to the existing techniques, the new technique uses more liquor measurements in predicting the final pulp quality. The liquor measurements obtained at different time instances during a cook are related to the final pulp quality through a partial least squares (PLS) regression model. In using the PLS regression model for control, two approaches an proposed. In the first approach, optimal control moves are computed directly using the PLS model, while the second approach employs a nonlinear H-factor model of which parameters are adapted using the prediction from the PLS model. The effectiveness of the prediction and control algorithms is examined through simulation studies. Experimental study is then performed on a lab-scale batch digester, to test the effectiveness of the prediction performance of the PLS model. The control algorithms will be tested on the experimental set-up in the future. (C) 2000 IFAC. Published by Elsevier Science Ltd. All rights reserved.

关键词： partial least squares pulp digester quality prediction and control

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A general framework for the integration of computational fluid dynamics and process simulation

A general framework for the integration of computational flu...

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7th International symposium on process systems Engineering

作者： Bezzo, F Macchietto, S Pantelides, CC Univ London Imperial Coll Sci Technol & Med Ctr Proc Syst Engn London SW7 2BY England

Computational fluid dynamics (CFD) and process simulation are widely used in the process industry. The two technologies are largely complementary, each being able to capture and analyse some of the important process characteristics. Their combined application can, therefore, lead to significant industrial benefits. This is especially true for systems, such as chemical reactors, in which steady-state performance, dynamics and control strategy depend on mixing and fluid flow behaviour. This paper presents a new approach for the integration of the capabilities of CFD technology and process simulation via a general interface that allows the automatic exchange of critical variables between the two packages, leading to a simultaneous solution of the overall problem. The approach applies to both steady-state and dynamic problems. The feasibility of the approach and its first practical implementation are demonstrated by integrating a widely used CFD package (Fluent 4.5, by Fluent Inc.) within a general-purpose advanced process simulator (gPROMS 1.7, by process systems Enterprise Ltd. (1999)). One case study involving a batch reactor is used to illustrate the ability of the combined tool to provide information on the detailed interactions between fluid mechanics, heat transfer, reaction and control strategy, and to provide insights on important design and operational decisions. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： framework integration computational fluid dynamics and process simulation

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Modeling, simulation and nonlinear control of a gas-phase polymerization process

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COMPUTERS & CHEMICAL ENGINEERING 2000年第2-7期24卷 945-951页

作者： Sato, C Ohtani, T Nishitani, H Yokogawa Elect Corp Tokyo 1808750 Japan Nara Inst Sci & Technol Nara 6300101 Japan

In an industrial gas-phase polymerization process, dynamics change globally due to grade changes and load changes, and these changes present a difficult control problem. In this paper, a nonlinear physical model was effectively used for the control system design. First, we developed a set of physical models of an industrial ethylene polymerization process with reference to McAuley's model. Parameters in the model were adjusted to simulate the actual process behavior. Second, in the control system design, the system is regarded as a two-input and two-output system. The two inputs are the feed rates of fresh hydrogen and butene, and the two outputs are cumulative melt index and density. An optimal servo controller with integral actions is designed according to the optimal regulator theory using a model linearized at a nominal operating point. Third, we examined the changes of process dynamics under typical operating points for different grade products. As a result, a nonlinear compensator was attached to the optimal servo controller to cope with remarkable changes in the process gain due to the product grade. This method resulted in good control performances during various grade changes. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： industrial polymerization reactor modeling grade transition product property control nonlinear compensation

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dynamics and control during startup of heat integrated distillation column

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COMPUTERS & CHEMICAL ENGINEERING 2000年第2-7期24卷 1091-1097页

作者： Eden, MR Koggersbol, A Hallager, L Jorgensen, SB Tech Univ Denmark Dept Chem Engn CAPEC DK-2800 Lyngby Denmark

To advocate the usage of process integration in industrial practice, it is important to be able to guarantee not only robust control during near steady state operation, but also to provide procedures for generating fast and reliable startup sequences. This contribution concentrates on describing a systematic procedure for development of plant startup sequences. The basis for the startup procedure development is available qualitative process knowledge. Application of the startup sequence generation procedure is demonstrated upon a heat integrated distillation plant. This plant illustrates some of the inherent effects of process integration upon a startup procedure. In particular, the effect of energy recycle upon the possible startup sequences and the effect of using an actuator for control purposes, i.e. the heat pump, which in itself requires significant startup time. The experimental application of two generated startup sequences illustrates that safe and reliable startups are ensured. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： process integration distillation column dynamics startup procedure generation

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Development of high performance operational strategies for polymerization reactor

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COMPUTERS & CHEMICAL ENGINEERING 2000年第2-7期24卷 481-486页

作者： de Toledo, ECV Martini, RF Maciel, R State Univ Campinas Sch Chem Engn BR-13081970 Campinas SP Brazil

This work presents the modeling and control of the temperature of a CSTR polymerization reactor connected to a semi-flooded horizontal condenser. The objectives of this work were to evaluate the cooling potential and the development of different algorithms to control the reactor temperature where bulk polymerization reactions take place via styrene free radicals. The control algorithms studied were classic PI, long-range predictive GPC and predictive-adaptive STGPC (GPC connected to the identification algorithm 'RLS'). The results obtained here show that the system provides quick, efficient and highly competitive refrigeration compared with other systems when this system is associated with a control algorithm which adapts perfectly to its dynamics characteristics. The new approach presented in this work, which associates the system 'CSTR + semi-flodded horizontal condenser' to the control algorithm (GPC and STGPC), makes the process highly competitive regarding refrigeration and performance. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： polymerization reactor autorefrigeration advanced control

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A new measure of process output controllability

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JOURNAL OF process control 2000年第2-3期10卷 185-194页

作者： Vinson, DR Georgakis, C Lehigh Univ Chem Proc Modeling & Control Res Ctr Bethlehem PA 18015 USA Lehigh Univ Dept Chem Engn Bethlehem PA 18015 USA

A steady state, multivariable, and nonlinear measure is presented for assessing the input-output, open-loop controllability of a process. This measure ascertains the inherent controllability of the process, as it is calculated in the absence of any regulatory control structure. For the process examples utilized in this paper, it is also independent of the inventory control structure that might be assumed present in or der to keep the inventory levels constant. This measure evaluates the ability of a design to reach all points of the desired output space and to reject the expected disturbances utilizing input action not exceeding the available input space. Besides being applicable to a SISO (Single Input, Signal Output) case, its multivariable character is shown to be more appropriate than existing measures such as RGA (Relative Gain Array), minimum singular value, and condition number. (C) 2000 IFAC. Published by Elsevier Science Ltd. All rights reserved.

关键词： control theory controllability inputs nonlinear gain output polygons

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dynamics and control during startup of heat integrated distillation column

Dynamics and control during startup of heat integrated disti...

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7th International symposium on process systems Engineering

作者： Eden, MR Koggersbol, A Hallager, L Jorgensen, SB Tech Univ Denmark Dept Chem Engn CAPEC DK-2800 Lyngby Denmark

关键词： process integration distillation column dynamics startup procedure generation

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