Challenges of modeling steam cracking of heavy feedstocks

Today single event microkinetic (SEMK) models for steam cracking of hydrocarbons allow simulating the conversion of heavy fractions. The key challenge to model the cracking behavior of these heavy feedstocks is related to feedstock reconstruction. The latter depends on the required level of molecular detail of the reaction network and of the feedstock characterization/ reconstruction model. This is illustrated for gas condensate feedstocks. Comparison of yield predictions with yields obtained in a pilot plant illustrate how uncertainties in the feedstock characterization propagate to the simulation results. The combination of a SEMK model and the feedstock reconstruction method based on maximization of the Shannon entropy allows to obtain accurate simulation results, provided that the specific density, the global PIONA weight or volume fractions, and the initial, 50% and final boiling point are known. Specifying less commercial indices results in a decrease of the agreement between simulated and experimentally obtained product yields. The developed methodology can be extended in a straightforward way to any heavy feedstock.