Prediction of the Catalyst Activity in the Process of Vacuum Gas Oil Hydrocracking Using a Mathematical Model.

The article presents a mathematical model of the vacuum gas oil hydrocracking process, which takes into account chemical transformations of the grouped components, including n-paraffins C22-C40, iparaffins C22-C40, n-paraffins C5-C21, i-paraffins C5-C21, naphthenes, aromatics, resins, hydrocarbon gas, and the reactions of coke formation and its accumulation on the catalyst surface during the operation cycle. The model also includes the equation for calculation of temperature profile during the process and the equation for calculation of the catalyst activity depending on the content of coke accumulated. The results on the influence of the hydrogen-containing gas consumption and the feedstock flow rate on the coke content on the catalyst, the activity of the catalyst and the temperature profile in the catalyst layers, obtained by calculations using a model, are presented. It is shown that hydrogen-containing gas consumption has optimal values depending on the feedstock flow rate, which ensure the maintenance of the maximum possible catalyst activity and the required depth of feedstock conversion. The optimal consumption of hydrogen-containing gas is determined at different feedstock flow rates. The increase in the feedstock flow rate by 20 m³/h from 220 m³/h to 240 m³/h requires increasing in the hydrogen-containing gas consumption by 500 kg/h from 9500 kg/h to 10000 kg/h. Maintaining hydrogen-gas consumption higher than optimal is impractical because it leads to decrease in the temperature of the process lower than favorable for the target reactions thus decreasing the depth of feedstock conversion with simultaneous increasingly more lower influence on the coke formation and increased operational costs. [ABSTRACT FROM AUTHOR]