An algorithm for gradient-based dynamic optimization of UV flash processes

Ritschel, Tobias; Capolei, Andrea; Gáspár, Jozsef; Jørgensen, John Bagterp

doi:10.1016/j.compchemeng.2017.10.007

Cited by 10 publications

(8 citation statements)

References 43 publications

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“…Extensive variables in (19a) are considerably larger in magnitude than the intensive variables in the interface description (19b). Such differences are known to cause the Jacobian matrix of the system to be ill-conditioned (Ritschel et al, 2018). This leads to precision problems during the numerical integration of a DAE or an ODE system.…”

Section: Change Of Coordinatesmentioning

confidence: 99%

A Non-equilibrium Approach to Model Flash Dynamics with Interface Transport

et al. 2018

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This article presents a modeling framework for a class of multiphase chemical systems based on non-equilibrium thermodynamics. Compartmental modeling is used to establish the dynamic properties of liquid-vapor systems operating far from thermodynamic equilibrium. In addition to the bulk-phase molar/energetic dynamics, interface transport processes yield to algebraic constraints in the model description.The irreversible system is thus written as a system of Differential-Algebraic Equations (DAEs). The non-equilibrium liquid-vapor DAE system is proven to be of index one. A local stability analysis for the model shows that the equilibrium state is unstable for non-isobaric operation regimes, whereas numerical evidence shows that isobaric operation regimes are stable. To extend the stability analysis, internal entropy production for the irreversible flash-drum is presented as a Lyapunov function candidate.

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Section: Change Of Coordinatesmentioning

confidence: 99%

A Non-equilibrium Approach to Model Flash Dynamics with Interface Transport

et al. 2018

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“…The condensate consists of eleven hydrocarbons as well as CO 2 , N 2 , and H 2 S. The separation process is assumed to be at vapor-liquid equilibrium. The dynamic optimization of the isoenergetic-isochoric (UV) flash process can be formulated as a bilevel optimization problem (Ritschel et al, 2017). The inner optimization problem is the 2nd law of thermodynamics that says that equilibrium of a closed systems is obtained at maximum entropy of the system.…”

Section: Flash Separation Processmentioning

confidence: 99%

A Thermodynamic Library for Simulation and Optimization of Dynamic Processes

2017

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Process system tools, such as simulation and optimization of dynamic systems, are widely used in the process industries for development of operational strategies and control for process systems. These tools rely on thermodynamic models and many thermodynamic models have been developed for different compounds and mixtures. However, rigorous thermodynamic models are generally computationally intensive and not available as open-source libraries for process simulation and optimization. In this paper, we describe the application of a novel opensource rigorous thermodynamic library, ThermoLib, which is designed for dynamic simulation and optimization of vapor-liquid processes. ThermoLib is implemented in Matlab and C and uses cubic equations of state to compute vapor and liquid phase thermodynamic properties. The novelty of ThermoLib is that it provides analytical first and second order derivatives. These derivatives are needed for efficient dynamic simulation and optimization. The analytical derivatives improve the computational performance by a factor between 12 and 35 as compared to finite difference approximations. We present two examples that use ThermoLib routines in their implementations: (1) simulation of a vapor-compression cycle, and (2) optimal control of an isoenergetic-isochoric flash separation process. The ThermoLib software used in this paper is distributed as open-source software at www.psetools.org.

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“…Consequently, it is natural to model dynamic phase equilibrium processes with differential-algebraic equations (DAEs). Dynamic optimization algorithms for UV flash processes have recently been developed [25], but state estimation in such systems has not been addressed yet.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Filters for State Estimation of UV Flash Processes

Ritschel

Jørgensen

2018

2018 IEEE Conference on Control Technology and Applications (CCTA)

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An algorithm for gradient-based dynamic optimization of UV flash processes

Cited by 10 publications

References 43 publications

A Non-equilibrium Approach to Model Flash Dynamics with Interface Transport

A Non-equilibrium Approach to Model Flash Dynamics with Interface Transport

A Thermodynamic Library for Simulation and Optimization of Dynamic Processes

Nonlinear Filters for State Estimation of UV Flash Processes

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