Extended Utilization of the Characterization of Petroleum Mixtures Based on Real Components

Recently, a novel approach to the characterization of petroleum mixtures based on substitute mixtures of real components has been described. This approach can replace the traditional approach based on pseudo-components. It can be shown that the approach based on real components is also well-suited for certain special tasks in the modelling of oil processing. Very often it is needed to blend petroleum fractions. It is shown how to modify the basic algorithm for assembling the substitute mixture of real components in order to cover also this problem. Second interesting area is incorporation of compounds containing sulphur, which is currently in the focus of refiners according to increasing environmental demands. The content of thiols and other compounds having impact on the environment is rather low but cannot be neglected for the simulation of separation processes if the results should be realistic and showing the way how to decrease the content of sulphur in gasoline mixtures. The adoption of the algorithm for the selection of real components into the substitute mixture for both cases is described and documented by examples. The new approach of a complex mixture characterization can be used in many directions. It is not only substituting the traditional approach based on pseudo-components but also enables to solve special tasks as the problems of oil blending and characterization of mixtures containing sulphur. The superiority of the approach using real components becomes apparent when the information about well-defined components is needed for modelling, i.e. when reliable physical property data and/or chemical character of components should be known. Characterization of complex mixtures is an important task, especially in oil processing industry. For the modelling, simulation, and other chemical engineering calculations, it is impossible to deal with thousands or even millions of components, which, moreover, cannot be properly identified. A common method is to find a substitute mixture comprising a relatively low number of components (usually 10—40) and having its behaviour close to the original mixture. For this purpose a novel approach to the characterization of petroleum mixtures based on substitute mixtures of real components has been described in several previous contributions [1—3]. Therefore, the traditional approach based on pseudo-components can be replaced by this new one exhibiting a number of advantageous features, e.g. direct availability of physical and chemical properties from the database or definition of the “chemical character” of the substitute mixture, which might be useful in certain situations. Generally, properties of pseudo-components have to be estimated using various more or less unreliable empirical relations and no chemical character is defined for the substitute mixture of pseudocomponents. Other possibilities for the characterization of complex mixtures, i.e. continuous thermodynamics [4] or wavelet models [5] are employing different mathematical background and will not be discussed here. Moreover, their practical applicability within simulation calculations is not easy since the models of unit operations must be formulated on a completely different basis. Therefore, in standard commercial simulation programs the principles of continuous thermodynamics mostly have not been implemented so far.