عنوان مقاله [English]
In this study, thermal cracking of two vacuum residues (VRs) from Tehran and Bandar Abbas refineries has been carried out. The products of this process consist of gas, liquid, and quasi-coke residue. Coke formation and the high sulfur content of products are the most difficulties that VR upgrading processes are faced with. The distribution of sulfur among these products has been studied. The investigation of the effect of operating conditions on the sulfur content of the liquid product has proven that sulfur concentration in the liquid fraction increases with temperature, while longer residence time can dilute the sulfur compounds and lessen their concentrations in the liquid product. The product of Bandar Abbas VR has a higher sulfur concentration relative to Tehran VR. It was shown that the liquid products, containing a high sulfur concentration, have higher densities and refractive indexes. On the other hand, higher process temperatures result in a greater production of the more desirable (liquid) product accompanied by lowering its quality. The effect of physicochemical properties of the VRs (sulfur content, density, Conradson Carbon Residue and H/C ratio) on the sulfur content of the liquid product has also been investigated. The kinetic modeling of reactions of sulfur compounds has been implemented for both VRs. Kinetic constants at different temperatures are given on the basis of the experimental results.