Lumping procedures in detailed kinetic modeling of gasification, pyrolysis, partial oxidation and combustion of hydrocarbon mixtures

Kinetic modeling can prove to be a powerful tool in the analysis of many sy stems. It has already been applied to a wide variety of chemical engineerin g problems, including gas phase and liquid phase pyrolysis, polymer thermal degradation, oxidative coupling and several other chemical processes. Exte nded kinetic schemes are now being used with increasing frequency in practi cal applications and most of them are available in the technical literature . Their dimensions and complexity justify the adoption of analogy rules and other simplifying assumptions within the different chemical reaction class es. The levels of simplification have to be carefully evaluated to make the m coherent with the final aim of the model. Owing to the huge amount of pos sible isomers for large hydrocarbons, it is usually necessary to lump a lar ge number of real components into a properly selected number of equivalent components. Consequently, the corresponding elementary reactions are also g rouped into equivalent or lumped reactions. The application of automatic generation techniques is particularly attracti ve where the extension of a core kinetic mechanism to higher hydrocarbons i s concerned. Generally speaking, this extension only requires a relatively limited set of independent elementary kinetic parameters. This approach has been successfully applied for many years to vapor phase h ydrocarbon pyrolysis; more recently, it was also extended to the liquid pha se pyrolysis of complex hydrocarbon mixtures (such as visbreaking or delaye d coking of refinery residues), to polyolefin thermal degradation and hydro carbon mixture combustion processes. Similarly, the low and high temperature mechanisms of the oxidation process can be organized into a comprehensive kinetic scheme able to simulate the oxidation of natural gas, commercial gasolines and jet-fuels. Several examples are reported here to demonstrate the reliability and effec tiveness of these mechanistic schemes and, more importantly, to discuss the adopted lumping and simplifying rules. (C) 2000 Published by Elsevier Scie nce Ltd.