Mathematical modeling of deactivation by coke formation in the cracking of gasoil

Abstract

In the present article the profile of coke formation for different gasoil (aromatic, paraffinic, naphthenic and equalized) feedstocks in a fixed bed traditional MAT reactor is studied. In order to achieve this goal, a 12-lump model was used. In this model the feedstock is divided into 4 different lumps: paraffins, naphthenes, aromatic rings and aromatic substituent groups. Three different deactivation functions were tested. Results have shown that a one parameter exponential deactivation function is satisfactory. The mathematical solution was performed using a differential-algebraic approach. Two different initial conditions were tested. Although higher coke formation in the begining of the bed is encountered for all feedstocks, the aromatic feedstock is the one that yields more coke. Also, the injection time was varied, showing that the higher the catalyst-to-oil ratio, the higher the influence of the injection time on the coke yield.