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MOLECULAR MANAGEMENT FOR REFINING OPERATIONS
[Thesis]. Manchester, UK: The University of Manchester; 2010.
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Abstract
Molecular management targets the right molecules to be at the right place, at theright time and at the right price. It consists of molecular characterisation of refiningstreams, molecular modelling and optimisation of refining processes, as well asoverall refinery optimisation integrating material processing system and utilitysystem on the molecular level. The need to increase modelling details to amolecular level is not just a result of political regulations, which force refiners tomanaging the molecule properly, but also seems to be a very promising to increasethe refining margin. In this work, four aspects of molecular management areinvestigated respectively.Molecular Type Homologous Series (MTHS) matrix framework is enhanced onboth representation construction and transformation methodology. To improve theaccuracy and adequacy of the representation model, different strategies areformulated separately to consider isomers for light and middle distillates. Byintroducing statistical distribution, which takes the composition distribution ofmolecules into account, the transformation approach is revolutionised to increasethe usability, and tackle the challenge of possibly achieving significantly differentcompositions from the same bulk properties by the existing approaches. Themethodology is also enhanced by applying extensive bulk properties. Case studiesdemonstrate the effectiveness and accuracy of the methodology.Based on the proposed characterisation method, refining processes are modelled ona molecular level, and then process level optimisation is preformed to have aninsight view of economic performance. Three different processes, includinggasoline blending, catalytic reforming, and diesel hydrotreating, are investigatedrespectively. Regarding gasoline blending, the property prediction of blendingcomponents, and the blending nonlinearity are discussed. To tightly control on theproperty giveaway, a molecular model of gasoline blending is developed, and thenintegrated into the recipe optimisation. As for the conversion processes, catalyticreforming and diesel hydrotreating, reactions and reactors are modelled separately,and then followed by the consideration of catalyst deactivation. A homogeneousrigorous molecular model of a semiregenerative catalytic reforming process,considering pressure drop, has been developed. In addition, a multi-period processoptimisation model has been formulated. Regarding diesel hydrotreating, amolecular model of reactions with a three-phase trickle-bed reactor has beendeveloped. The concept of reaction family is successfully applied. A structuralcontribution approach is used to obtain kinetics and adsorption parameters. Aseries of procedures are developed to solve the complex problem. Thereafter, aprocess optimisation model has been developed with the consideration of catalystdeactivation, with a new strategy on the division of catalyst life.Finally, a two-level decomposition optimisation method is extended to incorporatemolecular modelling into the overall refinery optimisation, and then applied in twoaspects. Firstly, with the integration of the process and the site-level models, abetter perspective is obtained with regard to a material processing system. Bymolecular modelling of refining streams and processes, the integrated approach notonly controls the molecules in products properly, but also increases the overallperformance. In the second application, a framework integrating a hydrogennetwork with hydroprocesses is developed to target the maximum profit, ratherthan saving hydrogen. It allocates hydrogen on the hydrogen network level andutilise hydrogen efficiently on the process level by optimising operatingconditions. Consequently, the extent of achieving the maximum profit could befully exploited with optimal hydrogen utilisation.
Keyword(s)
Molecular Characterisation; Molecular Management; Molecular Moelling; Refinery Optimisation