Hydrodesulfurization unit for natural gas condensate

Abstract

Nowadays, most of the world’s energy consumption is from fossil fuels. One of these fossil fuels is natural gas condensate which consists of various hydrocarbon components and could be used as the main fuel resource. However, these condensates contain sulfur contents (0.048 mass%) such as hydrogen sulfide, thiols (mercaptan), and aromatics, which are known as environmental pollutants. Hence, these sour hydrocarbon resources need to be purified to reduce the sulfur content. This study concerns the desulfurization of the natural gas condensate of South Pars field of Iran along with the elimination of disulfide oils of South Pars refinery, through hydrodesulfurization approach, which is simulated using Aspen Plus software. To reduce operating costs, unused hydrogen in outlet stream is recovered by the amine treatment. Purified condensates contain “petroleum cuts” which are classified by their boiling point ranges. These petroleum cuts from distillation unit are composed of butane, light naphtha, heavy naphtha, kerosene, and gasoil. The aim of this study is to reduce the sulfur content of these hydrocarbon cuts to less than 10 ppmw. The simulation results showed that the final products of distillation column were sulfur free (with sulfur content less than 1 ppmw). In this article, one optimization problem is formulated and solved using Aspen Plus software, to obtain the optimal stripper reflux ratio and feed stage. The objective function chosen in our optimization study is the minimization of the sulfur mass fraction at the bottom of stripper. To reduce the energy consumption, the effect of the reflux ratio on the reboiler and condenser duty was also studied by performing a sensitivity analysis. It was found that in the reflux ratio range from 3 up to 3.5 not only the mass fraction of sulfur at the bottom of the stripper was reduced but also the reboiler and condenser duty was minimized.