A pilot plant was designed and set up to study the thermal cracking of atmospheric gasoil. Based on the CCD (central composite design) method, a set of systematic experiments were designed and carried out. The designed variables were COT (coil outlet temperature), steam ratio and feed flow rate. The ranges of these variables were, respectively, equal to 716-884 o C, 0.46-1.136 and 0.977-6.02 g/min. The obtained minimum and maximum yield of ethylene was, respectively, equal to 1.7% and 30.9%, as well as the maximum yield of propylene was 12.2%. To predict the yield distribution of products and the coke formation in the range of operating conditions, a mechanistic model was developed based on experimental results. To analyze and characterize the atmospheric gasoil, a novel algorithm was applied. This algorithm utilized density, ASTM distillation curve, H/C ratio and the total aromatic fraction and generates the detail analysis of feedstock including paraffinic, naphthenic, aromatics and poly aromatic compounds.

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To investigate the efficiency of a Co-Mo catalyst in HDS process, a set of experiments were designed and carried out based on central composite design (CCD) methodology in an HDS pilot plant. The designed variables included temperature, LHSV and pressure. However, the hydrogen over fresh feed ratio remained constant. The ranges of these variables were, respectively, equal to 335-361 o C, 1.06-1.8 1/hr and 46.8-53.2 bar. The outcomes of experiments were employed to determine the coefficients of statistical models. For the clarification of the accuracy of the model, several statistical tests like ANOVA (Analysis of Variance), Lack-of-Fit test and residual squares were carried out. To optimize the operating conditions to achieve maximum sulfur removal, an optimization algorithm was employed. The outcomes revealed that the minimum sulfur content, which is 23.65 ppm in the final product, is attained at 355 o C, 1.2 1/ hr and 49.2 bar.

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