Print Email Facebook Twitter Simultaneous Process Optimisation and Molecular Design: Development of a group contribution method for a physically based equation of state Title Simultaneous Process Optimisation and Molecular Design: Development of a group contribution method for a physically based equation of state Author Olthof, T. Contributor Gross, J. (mentor) Bardow, A. (mentor) Faculty Mechanical, Maritime and Materials Engineering Department Process and Energy Programme Engineering Thermodynamics Date 2009-11-04 Abstract In this report the range of compounds that can be considered for simultaneous optimisation of process parameters and molecular structure through the CoMT-CAMD method is largely increased. The approach is extended by expanding a database of component PCP-SAFT parameters and development and implementation of a group contribution method GCP-SAFT. Before implementation of these approaches, the amount of structures for consideration was about one hundred, but it was shown here that this amount can be increased to over 1,000 and 100,000 respectively through implementation of an expanded PCP-SAFT parameter database and development of a group-contribution method (GCP-SAFT) respectively. An expanded PCP-SAFT parameter database was created by fitting measurements from the DIPPR database When this expanded database, containing PCP-SAFT parameters for 1371 components, is used for structure mapping, the value of the minimisation goal function (Second order Taylor Expansion approximation) can be decreased by an order of magnitude, compared to results obtained by Steur (2009). This indicates that the potential process performance, utilising real molecules, can be further increased by increasing the amount of molecules taken into consideration. The thermodynamic behaviour of components, for which no measurements have been performed, can be predicted through the development of a group contribution method for a physically based equation of state: Group Contribution Polar Statistical Associating Fluid Theory (GCP-SAFT). Three related group contribution approaches, derived from homogeneous fluid theory, showed very similar accuracy for the prediction of adapted non-associative PC-SAFT parameters. Therefore the approach developed by Vijande et al (2004) was adopted here as well, where the molecular parameters m , ms 3 and me k are linearly dependant on contributions for thecontained functional groups. This approach was expanded to associative and polar components constituting a maximum of a single dipolar or associative group. Molecular quadrupolar moments and binary interaction parameters were left out of consideration. Both dipolar and associative group contribution parameters were obtained by simple averaging. The prediction of dipole moments was relatively accurate, with AARE values for this parameter generally below 10% (36 out of 45 polar functional groups). Furthermore it is shown that the assumption of constant relative associative volume is rather strong for the homologous series of alcohols, whereas it is not well, statistically, supported for acids and amines. This is mainly due to the rejection of associative behaviour (negligible converged e AB k and k AB values) for a large portion of these series of compounds by the algorithm that fits PCP-SAFT parameters. AARE values for molecular adapted PCP-SAFT parameters m ,ms 3 and m2s 3e k are 9.28; 2.87 and 5.58% respectively for the GCP-SAFT method that takes dipolar and associative behaviour into account. This is less accurately than literature values obtained for the same model but can be largely explained through the incorporation of associative components. It is expected that Simultaneous Process Optimisation and Molecular Design overall prediction accuracy for mixtures will increase through the added prediction of dipolar and associative parameters. Model constants were fitted to 593 component PCP-SAFT parameter sets, which contained data for 75 associative components. This produced a set of 66 first order functional groups for which GCP-SAFT contributions are known. The confidence of this method is limited to components with a maximum of three branches, as the linear equations for m ,ms 3 and m2s 3e k are biased for cyclic and highly branched structures. These 66 functional groups were utilised in a sample structure generation algorithm to conveniently generate over a 100,000 different non-linear, non-aromatic structures and corresponding GCP-SAFT parameter sets that can be taken into account in simultaneous process optimisation and molecular design. Subject process optimisationmolecular design To reference this document use: http://resolver.tudelft.nl/uuid:6726959f-2a08-4e6e-b0fe-95d2534707a9 Part of collection Student theses Document type master thesis Rights (c) 2009 Olthof, T. Files PDF MSc_Thesis_Tim_Olthof.pdf 2.83 MB Close viewer /islandora/object/uuid:6726959f-2a08-4e6e-b0fe-95d2534707a9/datastream/OBJ/view