Showing papers in "Computers & Chemical Engineering in 1985"

TL;DR: In this paper, an efficient method for sensitivity analysis of nonlinear initial value problems, which may include algebraic equations as well as ordinary differential equations, is described, which is implemented with the implicit integrator DASSL and demonstrated on a stiff industrial reaction model.

TL;DR: This two-part study considers and improves several factors that affect the efficiency and robustness of the successive quadratic programming (SQP) optimization algorithm and describes several improvements to this infeasible-path approach.

TL;DR: It is shown that mixed- integer programming is the natural underlying tool for these types of methods, and mixed-integer linear programming models are reviewed for utility systems, heat-recovery networks and total processing systems.

TL;DR: The detailed techniques for improving the efficiency of a fault-diagnosis algorithm can be based on the signed directed graph, and the usefulness of the improved algorithm is demonstrated using a model of a chemical process comprising a reactor, a heat exchanger and a distillation tower.

TL;DR: Developing both algorithmic- and heuristic-based tree search algorithms for discovering the better systems of non-heat-integrated columns and new results permit the design of heat- integrated systems are highlighted.

TL;DR: This note discusses problems which arise when adapting a common approach to process optimization problems, and presents three examples where the use of simplified models can lead to detection of false optima or convergence failures.

TL;DR: In this article, a complete reaction network is generated by computer, using Boolean matrices as logical operators that describe the structure of the hydrocarbons and carbenium ions, and accounting for each elementary step.

TL;DR: In this article, a parametric sensitivity analysis of mathematical models consisting of sets of differential and algebraic equations is presented, which can be used to efficiently produce the model sensitivity coefficients, simultaneously with the solution of the model.

TL;DR: The structure of the inference networks in CONPHYDE which capture the intent of the 37 heuristic rules that from the knowledge base on which the current version is based are presented.

TL;DR: In this paper, a chain-ruling algorithm is proposed to incorporate analytic derivative information for parts of the flowsheet and generally leads to less frequent evaluation of the flow-sheet modules.

TL;DR: This work uses a hierarchical concept, whereby separation tasks selected by the algorithm at the top level are converted to cost-estimated sharp separation sequences at the second level, whereby the entire system is self- adapting, but also includes opportunities for interaction by the user.

TL;DR: Three optimization methods based on the efficient successive quadratic programming (SQP) algorithm of nonlinear programming and the Reduced and Complete Feasible Variant (RFV and CFV) algorithms perform efficiently and interface easily with most current sequential modular simulators.

TL;DR: In this article, a numerical procedure for the solution of transient models for the simulation of fixed bed catalytic reactors is developed, which includes axial dispersion in the external fluid phase, interphase mass and heat transfer resistances, intraphase mass resistance and any given kinetic scheme with complex reaction rate expressions.

TL;DR: In this paper, three methods are described for determining the strategy of opportunity maintenance which will maximize the overall performance of the plant, where the problem posed in the form of a stochastic decision tree is treated by a branch and bound procedure.

TL;DR: In this paper, an index called ORP (Order Reduction Parameter) is developed to predict a priori, the extent of order reduction achievable and to provide guidelines for choosing a reduced-order model of the appropriate size.

TL;DR: These desirable attributes that should be present in commercially available equation-oriented flowsheeting systems developed in the future are described and modeling considerations for complex flowsheets and the solving of models are considered.

TL;DR: In this article, a depth-first algorithm based on reversible thermodynamics and second-law analysis is proposed to synthesize acyclic separation trains with minimum reversible work of separation and irreversibility.

TL;DR: In this article, five codes for solving systems of nonlinear equations, which are available in the literature, are compared using 10 test problems, and the results of this study give the chemical engineer clear guidelines concerning the method that should be used for solving a particular problem.

TL;DR: In this article, a shortcut model is presented for vapor-compression refrigeration cycles which is expressed explicitly in terms of temperature and requires only saturated refrigerant data for evaluation, based on this model, an index of performance for pure refrigeration is proposed.

TL;DR: In this article, general criteria leading to a better choice of a model that fulfills the objectives of the simulation, are established, and different ways in which the parameters can be obtained are analyzed, and the numerical methods for solving the model equations are discussed.

TL;DR: The locally parameterized continuation method (LPM) as mentioned in this paper is a convergence technique for distillation models, where the starting point on the path corresponds to the solution of an easy, but somewhat unrealistic, distillation model, and the stopping point is a solution of a difficult more realistic model.

TL;DR: A systematic, noniterative procedure requiring minimal numeric information has extended structural analysis to the synthesis of regulatory control systems comprising single-input single-output (SISO) controllers as discussed by the authors.

TL;DR: In this article, the application of three constrained, nonlinear optimization methods (method of multipliers, complex method and adaptive random search method) to six chemical process problems is described.

TL;DR: In this paper, the heat and mass transfer processes between gas phase and solid particles are studied in a fixed bed throughflow dryer, and the relationship of this model to the cell model with lumped variables for the particles, as well as to the continuous two phase model is analyzed.

TL;DR: In this article, a mixed K-value model for the simulation of three-phase vapor-liquid equilibrium stages has been proposed and implemented with a minimum effort into the Badger General Material Balance flow-sheeting program.

TL;DR: By beginning with the most general implicit relationships between the controlled variables and the manipulated variables of a control system, formulas for computing the relative gain are developed, which leads to a more comprehensive analysis and consequently a better understanding of the conditions responsible for infinite relative gains.

TL;DR: In this paper, a branch and bound solution procedure is presented which uses a simulation model to evaluate sequence compeltion times and an initial upper bound completion time is determined based on a heuristic scheduling rule.

TL;DR: In this article, the mass balance coefficient matrix was transformed into an M-Matrix and the row sums of the transformed matrix were used to provide linear inequalities for non-linear systems.

TL;DR: In this paper, the authors propose a strategy generale de calcul des procedes de separation a contrecourant des melanges complexes, a strategy based on the theory of resolution numerique des grands systemes d'equations.

TL;DR: The overall design methodology is based on a unified treatment of recent theoretical results in modern control and new computational techniques in symbolic logic manipulation, singular value decomposition and optimization.