A COMPREHENSIVE PROGRAM FOR VISBREAKING SIMULATION - PRODUCT AMOUNTS AND THEIR PROPERTIES PREDICTION

The visbreaking process is adopted in many refineries, particularly in Europe and the Far East. It consists of a liquid phase pyrolysis of a tmospheric or vacuum residues, with the aim to reduce the viscosity of the visbroken residues and, in doing that, to significantly increase the distillate yields. In spite of the importance of the process, main ly empirical models have been proposed. However rising interest appear s to be towards a deeper understanding of the phenomena influencing pr ocess performance. The largest difficulties, in principle, are connect ed with the infinite number of components, reactions involved and, in the mean time, to the relatively poor level of the available data for the feedstock characterisation. Also, the prediction of the product am ounts and their properties presents considerable problems. A mechanist ic approach to this process is proposed, including aspects such as fou ling of the coils, effluent amounts and properties (residue stabilitie s, sulphur and asphaltene content, viscosity, specific gravity and so on). A set of results is compared with data from literature, research lab tests and commercial units. (C) 1997 Elsevier Science Ltd.