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20
Simultaneous Cyclic Scheduling and Control of a Multiproduct CSTR
 Ind. Eng. Chem. Res
"... In this work we propose a scheduling and control formulation for simultaneously addressing scheduling and control problems by explicitly incorporating process dynamics in the form of system constraints that ought to be met. The formulation takes into account the interactions between such problems an ..."
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Cited by 9 (6 self)
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In this work we propose a scheduling and control formulation for simultaneously addressing scheduling and control problems by explicitly incorporating process dynamics in the form of system constraints that ought to be met. The formulation takes into account the interactions between such problems and is able to cope with nonlinearities embedded into the processing system. The simultaneous scheduling and control problems is cast as a MixedInteger Dynamic Optimization (MIDO) problem where the simultaneous approach, based on orthogonal collocation on finite elements, is used to transform it into a MixedInteger Nonlinear Programming (MINLP) problem. The proposed simultaneous scheduling and control formulation is tested using three multiproduct continuous stirred tank reactors featuring hard nonlinearities. 2 1
A Boundary Value Problem Approach to the Optimization of Chemical Processes Described by DAE Models
, 1997
"... An efficient and robust technique for the optimization of dynamic chemical processes is presented. In particular, we address the solution of large, multistage optimal control and design optimization problems for processes described by DAE models of index one. Our boundary value problem approach (a ..."
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Cited by 4 (0 self)
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An efficient and robust technique for the optimization of dynamic chemical processes is presented. In particular, we address the solution of large, multistage optimal control and design optimization problems for processes described by DAE models of index one. Our boundary value problem approach (a simultaneous solution strategy) is based on a piecewise parametrization of the control functions and a multiple shooting discretization of the DAEs, combined with a specifically tailored SQP technique. The inherent problem structure is exploited on various levels in order to obtain an efficient overall method. In addition, the formulation lends itself well to parallel computation. Unlike other simultaneous strategies based on collocation, direct use is made of existing advanced, fully adaptive DAE solvers. An implementation of this strategy is provided by the recently developed modular optimal control package MUSCODII. Apart from a difficult DAE test problem with control and path constrain...
Dynamic Optimization Of Bioprocesses: Deterministic And Stochastic Strategies
, 1998
"... The general problem of dynamic optimization of bioprocesses with unspecified final time is considered. Several solution strategies, both deterministic and stochastic, are compared based on their results for three bioprocess case studies. A hybrid (stochasticdeterministic) method is also presented a ..."
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Cited by 3 (1 self)
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The general problem of dynamic optimization of bioprocesses with unspecified final time is considered. Several solution strategies, both deterministic and stochastic, are compared based on their results for three bioprocess case studies. A hybrid (stochasticdeterministic) method is also presented and evaluated, showing significant advantages in terms of robustness and computational effort. INTRODUCTION In recent years, many efforts have been devoted to the optimization and control of bioprocesses. An example of a problem that has received major attention is the dynamic optimization (open loop optimal control) of fedbatch bioreactors (e.g. van Impe, 1996; Roubos et al, 1997; Banga et al., 1997; Tholudur and Ramirez, 1997). Most bioprocesses have highly nonlinear dynamics, and constraints are also frequently present on both the state and the control variables. Thus, efficient and robust dynamic optimization methods are needed in order to successfully obtain their optimal operating po...
Optimization Strategies for Dynamic Systems
 In C. Floudas, P. Pardalos (Eds), Encyclopedia of Optimization
, 1999
"... Introduction and Problem Statement Interest in dynamic simulation and optimization of chemical processes has increased significantly during the last two decades. Common problems include control and scheduling of batch processes; startup, upset, shutdown and transient analysis; safety studies and th ..."
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Cited by 3 (0 self)
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Introduction and Problem Statement Interest in dynamic simulation and optimization of chemical processes has increased significantly during the last two decades. Common problems include control and scheduling of batch processes; startup, upset, shutdown and transient analysis; safety studies and the evaluation of control schemes. Chemical processes are modeled dynamically using differentialalgebraic equations (DAEs). The DAE formulation consists of differential equations that describe the dynamic behavior of the system, such as mass and energy balances, and algebraic equations that ensure physical and thermodynamic relations. The general dynamic optimization problem can be stated as follows: min z(t);y(t);u(t);t f ;p '(z(t f ); y(t f ); u(t<F8
Optimization Framework for the Synthesis of Chemical Reactor Networks
, 1998
"... The reactor network synthesis problem involves determining the type, size, and interconnections of the reactor units, optimal concentration and temperature profiles, and the heat load requirements of the process. A general framework is presented for the synthesis of optimal chemical reactor networks ..."
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Cited by 2 (1 self)
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The reactor network synthesis problem involves determining the type, size, and interconnections of the reactor units, optimal concentration and temperature profiles, and the heat load requirements of the process. A general framework is presented for the synthesis of optimal chemical reactor networks via an optimization approach. The possible design alternatives are represented via a process superstructure which includes continuous stirred tank reactors and cross flow reactors along with mixers and splitters that connect the units. The superstructure is mathematically modeled using differential and algebraic constraints and the resulting problem is formulated as an optimal control problem. The solution methodology for addressing the optimal control formulation involves the application of a control parameterization approach where the selected control variables are discretized in terms of time invariant parameters. The dynamic system is decoupled from the optimization and solved as a func...
State of the Art of Research in Flexibility, Operability & Dynamics
, 1998
"... this paper and need to be defined. Flexibility commonly refers to the range of operating conditions, normally steady state conditions, which a particular process design can achieve. Switchability refers to the ability of a plant to move from alternative steady state conditions. Controllability refer ..."
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Cited by 1 (0 self)
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this paper and need to be defined. Flexibility commonly refers to the range of operating conditions, normally steady state conditions, which a particular process design can achieve. Switchability refers to the ability of a plant to move from alternative steady state conditions. Controllability refers to the ability of a particular design, usually including TWG3/D Bogle/R&D SoA Review/Rev P/19980112 3 the control system, to maintain safe and stable operating conditions following disturbances.
Optimal Operation of Alternating Activated Sludge Processes
"... The study presents dynamic optimisation of a small size single basin wastewater treatment plant. The objectives are to determine an optimal sequence of aeration/nonaeration times so that for a typical diurnal pattern of disturbances, the e#uent constraints are respected, the plant remains in peri ..."
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Cited by 1 (0 self)
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The study presents dynamic optimisation of a small size single basin wastewater treatment plant. The objectives are to determine an optimal sequence of aeration/nonaeration times so that for a typical diurnal pattern of disturbances, the e#uent constraints are respected, the plant remains in periodical steady state, and energy consumption is minimised.
Combined Continuous And Discrete Dynamics
"... Introduction There are various sources of discrete phenomena in chemical processes: . discrete changes in the processes (e.g., a vessel becomes empty, a liquid is completely evaporated, a column is flooded) . instruments which give discrete rather than continuous outputs (especially for levels a ..."
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Introduction There are various sources of discrete phenomena in chemical processes: . discrete changes in the processes (e.g., a vessel becomes empty, a liquid is completely evaporated, a column is flooded) . instruments which give discrete rather than continuous outputs (especially for levels and flows) . actuators with discrete settings/positions (e.g., on/off valves, pumps, heatings with constant current, motors without speed control) and the associated binary feedback signals . continuous measurements trigger thresholds (e.g. alarms) or the plant is classified by discrete states ("normal", "exceptional", "dangerous / shutdown necessary") . steps in recipes, transitions between batches or cuts in batch distillation . startup and shutdown of continuous plants, product changeover, etc. In the process control system, various layers of the automation hierarchy can be disti
Switchability and Flexibility of Dynamic Processes
"... This report is a survey on the current state of the art in switchability and #exibility analysis written for use within the technical working group #Flexibility, Operability and Dynamics #TWG3#" of the European CAPE.NET initiative. ..."
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This report is a survey on the current state of the art in switchability and #exibility analysis written for use within the technical working group #Flexibility, Operability and Dynamics #TWG3#" of the European CAPE.NET initiative.
Interaction of Design and Control: Optimization with Dynamic Models
, 1997
"... Process design is usually approached by considering the steadystate performance of the process based on an economic objective. Only after the process design is determined are the operability aspects of the process considered. This sequential treatment of the process design problem neglects the fact ..."
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Process design is usually approached by considering the steadystate performance of the process based on an economic objective. Only after the process design is determined are the operability aspects of the process considered. This sequential treatment of the process design problem neglects the fact that the dynamic controllability of the process is an inherent property of its design. This work considers a systematic approach where the interaction between the steadystate design and the dynamic controllability is analyzed by simultaneously considering both economic and controllability criteria. This method follows a process synthesis approach where a process superstructure is used to represent the set of structural alternatives. This superstructure is modeled mathematically by a set of differential and algebraic equations which contains both continuous and integer variables. Two objectives representing the steadystate design and dynamic controllability of the process are considered. T...