(52d) Single Event Kinetics Based Simulation of Vacuum Gas Oil Hydrocracking Using Deterministic Molecular Reconstruction

Martinis, J. - Presenter, Bryan Research & Engineering Inc
Froment, G. F. - Presenter, Texas A&M University

The usual characterization of vacuum gasoil practiced today is inadequate for the simulation of hydrocracking based upon a modern fundamental and realistic kinetic model. Significant progress has been achieved in this field by Molecular Reconstruction techniques. In the present work, a deterministic approach to Molecular Reconstruction of vacuum gasoil has been combined with Single-Event Kinetics in the simulation of a Hydrocracking Process Unit targeting maximum Diesel production. Three different process flow configurations combining pre-treatment, reaction, fractionation and recycle have been investigated. At the core of the simulation model, a computer-generated reaction network consisting of 126 million elementary steps and 18 million species describes the fundamental chemistry of hydrocracking. Subsequent identification of the rate-determining steps and application of equilibrium constraints to fast elementary steps permits to solve for intermediate species, leaving about 180,000 reaction rates and 1267 species to solve for in the formulation. Rate parameters of the elementary steps are modeled by means of the Single-Event concept, thus reducing the number of model parameters to be determined from plant data to a realistic level. In addition, a rigorous model for trickle-flow in packed-bed reactors has been validated for extreme limiting conditions such as local hydrogen depletion and transition to complete vaporization.