CONTINUOUS LUMPING MODEL FOR SIMULATION OF HYDROCRACKING

Hydrocracking of vacuum gasoil is an important chemical process involv ing complex reaction mixtures. The reaction is carried out in a trickl e-bed reactor, considering reaction kinetics along with such hydrodyna mic effects as mass transfer, intraparticle diffusion, and partial wet ting. Since reaction kinetics is critical to modeling and simulation o f a hydrocracking reactor; a modeling approach needs to capture the co mplex chemistry of the process, along with the elegance of the solutio n method. The complex chemistry of hydrocarbon is represented by an el egant continuous lumping approach to modeling. The true boiling point of the mixture is used as the characterization parameter. Since the ra te constant of hydrocracking is assumed to be a monotonic function of the true boiling point, it is possible to reformulate mass-balance equ ations in terms of rate constant as a continuous variable. A novel dis tribution function p(k, K), which determines the fractional yield dist ribution of species, was formulated based on data from the cracking pa tterns of various model compounds. Resulting integrodifferential equat ions are solved numerically to obtain yields of various fractions as a function of reactor residence time. Model predictions are compared wi th limited published data to show the utility of the model.