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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Environmental monitoring and assessment 13 (1989), S. 271-282 
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The use of an extended Kalman filter for state estimation in biological wastewater treatment processes is discussed. The application of the technique requires an adequate mechanistic dynamic model and the identification and modelling of the major sources of stochastic disturbances in the process. The filter allows the on-line tracking of process variables which are not directly measurable. The use of an extended Kalman filter is illustrated through a simulated application to a high rate anaerobic wastewater treatment process.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A state space model is developed for an existing nonadiabatic packed-bed reactor which experiences axial and radial concentration and temperature gradients resulting from highly exothermic reactions involving several chemical species. The set of partial differential equations is reduced from three to two dimensions using orthogonal collocation. Further use of orthogonal collocation on the quasi steady state version of the differential equations results in a set of coupled algebraic and differential equations from which a linearized low-order state space model is obtained. The model parameters are estimated from reactor data, and the fitted model is used for design and implementation of a multivariable stochastic control schemes on the reactor. These applications are described in parts II and III of this paper.
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 26 (1980), S. 910-916 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A number of approaches to the optimal selection of sensor locations are presented, and some of these are applied to determine optimal thermocouple positions in a packed bed tubular reactor. As expected, the optimal locations were found to be those surrounding the hot spot location. The theory also revealed that for good state estimation and for goodlinear quadratic control of the reactor, only one or two well located temperature measurements are necessary rather than the entire temperature profile.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1496-1506 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A practical application of advanced, model-based, multivariable control to a pilot plant packed-bed reactor carrying out highly exothermic butane hydrogenolysis reactions is presented. The system is first stabilized by using butane flow rate to control the reactor hot-spot temperature. Propane production and butane conversion are then controlled using multivariable controllers that manipulate the hot-spot temperature set point and hydrogen flow rate. The controller designs are based on multivariable transfer function models developed using multivariable time series and process identification methods.Two types of multivariable controllers are applied. The first is an internal model controller (IMC) utilizing a stabilized approximation of the model inverse and a tunable exponential filter. The second is a linear-quadratic (LQ) controller design using pulse transfer function models to characterize the process dynamics and autoregressive-moving average models to characterize the disturbances. The optimal control solution was arrived at via a spectral factorization solution to the Wiener-Hopf equations. The results indicate that both designs, if well tuned, provide good performance and robustness over a wide range of operation.
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 837-850 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic kinetic model describing gas-phase olefin copolymerization using a multiple active site Ziegler-Natta catalyst is presented. This model is capable of predicting production rate, molecular weight, and copolymer composition changes observed in an industrial reactor. The model also explains how broad molecular weight distributions and bimodal copolymer compositions can occur as has been observed for commercial linear polyethylenes.
    Additional Material: 17 Ill.
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  • 6
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A linear low-order state space dynamic model for a catalytic butane hydrogenolysis reactor which has been fitted to reactor dynamic data is used to develop a multivariable linear quadratic feedback control algorithm for regulatory control of the reactor exit concentrations using temperature measurements only. Kalman filter theory is used to obtain state estimates for the system. The control algorithm developed is implemented on the pilot plant reactor in a series of DDC control studies. The controller is shown to perform very well and considerably better than a single loop PI controller with a feedback on the hot spot temperature. Performance is evaluated both under the normal stochastic disturbances in the system and under a severe deterministic load disturbance. Exit concentrations predicted by the model and used in the performance index are shown to compare very favorably with actual concentrations obtained from a process gas chromatograph.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1481-1495 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Optimal linear-quadratic (LQ) controller design is usually associated with state space techniques. However, when one has measurements of the outputs to be controlled, there are many advantages to designing these LQ controllers using input-output transfer function models. The design procedure leads to a discrete equivalent of the Wiener-Hopf equation, which can be solved using a spectral factorization approach.In this paper the design procedure is presented and various interpretations of the resulting controllers are discussed. In particular, the controllers are shown to be of the internal model controller (IMC) form, and the Wiener-Hopf procedure is shown to be a powerful way of selecting approximate model inverses and filters that yield good performance and robustness characteristics. The approach treats the problem of simultaneous disturbance rejection and set-point tracking, and it easily handles nonsquare systems.The design approach, its performance/robustness trade-offs, and the structure of the resulting controllers are demonstrated using models for several processes, including a two-input/one-output sheet forming process, a (3 × 3) multivariable level control problem, and a (2 × 2) multivariable catalytic reactor.
    Additional Material: 10 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 825-835 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A major difficulty affecting the control of product quality in industrial polymerization reactors is the lack of suitable on-line polymer property measurements. In this article a scheme is developed to predict melt index and density in a fluidized-bed ethylene copolymerization reactor. Theoretically-based models are derived to predict quality variables from the available on-line temperature and gas composition measurements. Adjustable parameters in these models are updated on-line using infrequent laboratory measurements and a recursive parameter estimation technique. The application of this methodology is illustrated using operating data from an industrial reactor. It is shown that both melt index and density can be successfully predicted. Knowledge of product property deviations from desired targets is required so that manufacturers can take corrective actions to reduce the quantity of off-grade material made and produce a consistent product.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1564-1576 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using gas-phase technology many grades of polyethylene can be produced in a single reactor. For a series of three polyethylene products, model-based dynamic optimization is used to determine optimal grade changeover policies. Optimal manipulated variable profiles are determined for hydrogen and butene feed rates, reactor temperature setpoint, gas bleed flow, catalyst feed rate, and bed level setpoint. It is shown that large transitions in melt index are hampered by slow hydrogen dynamics, and that the time required for such a transition can be reduced by manipulating the temperature setpoint and the bleed stream flow. Reduction of the bed level and catalyst feed rates during changeovers can significantly reduce the quantity of off-specification polymer produced. It is demonstrated that melt index and density are not sufficient to characterize the properties of polymer produced during grade transitions, and that the shape of the cumulative copolymer composition distribution is very sensitive to the grade changeover policy used. Optimal transition policies should not be implemented without feedback control. Disturbances and model mismatch can result in product property trajectories which deviate significantly from the nominal optimal trajectory.
    Additional Material: 9 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 855-866 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A nonlinear model-based scheme is developed for product property control in industrial gas-phase polyethylene reactors. The controller regulates instantaneous melt index and density, and provides servocontrol during grade changeovers. Hydrogen and butene feed rates are manipulated to force the product properties onto desired trajectories. During grade changeovers, these trajectories are determined from off-line dynamic optimization studies. Optimal open-loop policies for reactor temperature, bleed stream flow, catalyst feed rate, and bed level are implemented as part of the changeover strategy.The nonlinear feedback controller design is based on global input/output linearization methods. Disturbances are estimated, and plant/model mismatch is removed using an extended Kalman filter. Simulations on a complex mechanistic model of the process reveal that the nonlinear controller performs well for both regulatory and servocontrol. An analogous linear IMC controller is inadequate for disturbance rejection at different operating conditions and for control during grade changeovers. The simplicity of the nonlinear control algorithm makes it an interesting candidate for industrial application. This single controller can be used to control the properties of many grades of polyethylene made in the reactor and to accomplish near optimal changeovers between these grades.
    Additional Material: 8 Ill.
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