Accelerating complex chemical equilibrium calculations — a review

Show simple item record Roos, Willem Abraham Zietsman, Johannes Hendrik 2023-03-10T08:11:07Z 2022-06
dc.description.abstract Incorporating multicomponent, multiphase, high-temperature, complex chemical equilibrium calculations into process and multiphysics models can provide significant insights into materials, processes and equipment. We refer to applications where the inclusion of these calculations provided insights that would otherwise be difficult to obtain. From these examples, the advantages and importance of including complex equilibria into models are clear for cases where more accurate descriptions of practically relevant systems are needed. Equilibrium calculations are, in general, omitted or incorporated in a simplified manner due to their computational expense. The equilibrium state of a complex chemical system is determined by minimising the Gibbs free energy for a given set of system component concentrations, temperature, and pressure. This minimisation routine is computationally expensive and makes direct integration of chemical equilibrium calculations into models infeasible. There have been many attempts to, in one way or another, accelerate these calculations. This includes methods such as creating look-up tables prior to the simulation or in-situ, fitting piecewise polynomial functions to thermochemical properties, phase diagram discretisation, sensitivity derivatives, machine-learning algorithms, and parallelisation. Pre-calculated databases tend to become very large and require much storage space, even when unstructured grids are used or piece-wise polynomials fitted. Neural network results do not adhere to physical laws such as mass conservation and large training sets are required to reduce this error. In-situ or on-demand methods of creating a database shows great promise because only the thermochemical regions that are of interest to the model are captured in the database, reducing the storage size and the amount of data to search through. No prior knowledge of the system is required to create the database. The Gibbs phase rule can be used to determine which geometrical features of a phase diagram to discretise and create a sparse database that covers large temperature, pressure and compositional ranges. The lever rule can then be used for fast and accurate interpolation between data points. Established thermochemical theory provides security for the decisions made within the discretisation and interpolation algorithms. Based on this review, an in-situ phase diagram discretisation method strongly based on thermochemical theory such as the Gibbs phase rule and the lever rule holds potential for significant acceleration of complex chemical equilibrium calculations. en_US
dc.description.department Materials Science and Metallurgical Engineering en_US
dc.description.embargo 2024-03-05
dc.description.librarian hj2023 en_US
dc.description.sponsorship Ex Mente Technologies, South Africa as well as Glencore through their funding of the Chair in Pyrometallurgical Modelling at the University of Pretoria, South Africa. en_US
dc.description.uri en_US
dc.identifier.citation Roos, W.A. & Zietsman, J.H.2022, 'Accelerating complex chemical equilibrium calculations — a review', Calphad, vol. 77, art. 102380, pp. 1-10, doi : 10.1016/j.calphad.2021.102380. en_US
dc.identifier.issn 0364-5916 (print)
dc.identifier.issn 1873-2984(online)
dc.identifier.other 10.1016/j.calphad.2021.102380
dc.language.iso en en_US
dc.publisher Elsevier en_US
dc.rights © 2021 Published by Elsevier Ltd. Notice : this is the author’s version of a work that was accepted for publication in Calphad. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version was subsequently published in Calphad, vol. 77, art. 102380, pp. 1-10, 2022, doi : 10.1016/j.calphad.2021.102380. en_US
dc.subject Complex equilibrium calculations en_US
dc.subject CALPHAD en_US
dc.subject Acceleration en_US
dc.subject Multiphysics models en_US
dc.subject Process models en_US
dc.title Accelerating complex chemical equilibrium calculations — a review en_US
dc.type Postprint Article en_US

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