Optimization of a crude oil distillation unit based on total-process simulation

Crude oil distillation unit (CDU) is significant in refinery, and retrofitting a crude oil distillation unit is more common than building a new one as consideration of the enormous investment cost. The process simulation system PRO/II is used to build a rigorous model for the crude oil distillation unit based on the conventional two-furnace and three-column process flow in refinery that addresses both the distillation columns and the heat exchanger network (HEN) simultaneously. The effect of the differences of crude oil properties on the product yield, pumparounds for heat removals, the design of heat exchanger networks and CO2 emissions in crude distillation units is focused. Furthermore, energy use improvement for crude oil distillation units with consideration of light and heavy crude oil is proposed. Based on the investigation carried out on the existing CDU, the optimum operating conditions and retrofitting solutions have been obtained by two actual crude oil distillation units with three columns and corresponding HEN, effectiveness of the retrofits is finally evaluated by means of thermodynamics and economic analysis. The results show that the retrofits required a fixed capital cost of $102925 and $177215 and saving operation cost is about 355226$/year and 656181$/year. The payback time is approximately0.29 and 0.27 year for the retrofits and optimization of light crude oil distillation process and heavy crude oil distillation process.