Equation‐oriented flowsheet simulation and optimization using pseudo‐transient models

Abstract

Tight integration through material and energy recycling is essential to the energy efficiency and economic viability of process and energy systems. Equation-oriented (EO) steady-state process simulation and optimization are key enablers in the optimal design of integrated processes. A new process modeling and simulation concept based on pseudotransient continuation is introduced. An algorithm for reformulating the steady-state models of process unit operations as differential-algebraic equation systems that are statically equivalent with the original model is presented. These pseudo-transient models improve the convergence of EO process flowsheet simulations by expanding the convergence basin. This concept is used to build a library of pseudo-transient models for common process unit operations, and this modeling concept seamlessly integrates with a previously developed time-relaxation optimization algorithm. Two design case studies are presented to validate the proposed framework.The framework developed in this article consists of converting the algebraic model into a pseudo-transient process model with an equivalent steady-state solution, which can be obtained by a DAE time integration.The pseudo-transient models described above were implemented in gPROMS. 57 In the following sections, we 4116

Equation‐oriented simulation and optimization of process flowsheets incorporating detailed spiral‐wound multistream heat exchanger models

“…has been developed. [20][21][22][23] We describe the pseudo-transient continuation concept as relevant to flowsheet simulation and optimization below. To this end, consider a steady state model which describes a process flowsheet f ss :…”

“…A library of pseudo‐transient models for common unit operations (reactors, compressors, flash tanks, distillation columns, etc.) has been developed . We describe the pseudo‐transient continuation concept as relevant to flowsheet simulation and optimization below.…”

“…The general method for converting algebraic process models to DAE systems is detailed by Pattison and Baldea and a few key elements central to solution of complex, physics‐based models (such as spiral‐wound SWHXs) and process flowsheets are summarized below:…”

“…In a recent contribution, 20 we have shown that robust equation-oriented flowsheet modeling, simulation, and optimization of flowsheets featuring MHEX models are possible using a pseudo-transient continuation approach. 21 This involves converting a subset of the algebraic (steady state) model equations in the flowsheet to ordinary differential equations (ODEs) in a fictitious time variable. The pseudo-transient models are formulated such that they are statically equivalent to the original equations, that is, they have the same steady state solution to the original algebraic model.…”

Quantitative Systems Pharmacology: A Framework for Context

“…However, each component and element of the network is well annotated and described by appropriate constitutive equations. Each element of the network can be represented as an appropriate object in modular form (Chen, Adomaitis 2006), whereas the equation-oriented formalism enables the exact representation of each module by a set of detailed mathematical equations (Pattison, Baldea 2014). Assembling of individual models can easily be automated in a “drag-and-drop” manner and complex models can therefore be generated and analyzed in great detail.…”