Numerical problems in the solution of oxidation and combustion models

Faced with large and detailed kinetic schemes of pyrolysis, partial oxidati on and combustion of hydrocarbon mixtures, the complex process models usual ly constitute stiff systems of both differential and coupled differential-a lgebraic equations. This paper discusses different typical applications of a new robust and efficient numerical integration method to solve these prob lems. The examples refer to gas solid catalytic reactors, partial oxidation of hydrocarbons and homogeneous and heterogeneous combustion processes. The results show the clear advantages of this numerical package when compar ed with those commonly referred to and used in the scientific literature. I n our experience, the robustness of the new method allows the user to overc ome the failures of other codes and to reduce the critical selection of rel ative and absolute tolerances. Moreover, the efficiency of the method, in t erms of computing time, is significantly improved mainly due to a better po licy of Jacobian evaluations.