Simulation And Retrofit Design Of An Atmosphere-Vacuum Distillation Unit And Its Heat-Exchanger Networks

Petroleum-processing consumes enormous energy. The atmosphere-vacuum unit is the leading process in a refinery plant, which consumes 20~30 percent of the total energy consumption of the plant. The atmosphere-vacuum process and its energy consumption are of great importance for equipment investment, operation mangement, energy saving optimization and economic benefit of a refinery plant. Therefore, it is necessary to reduce the energy consumption and improve the efficiency of the atmosphere-vacuum distillation process .Based on the praticle data of an atmosphere-vacuum distillation unit in a refinery plant, its atmosphere-vacuum distillation unit is simulated and optimized in this dissertation. The research content mainly includes the following aspects:The atmosphere-vacuum distillation is simulated by using PRO/Ⅱsimulator, based on the properties of the crude oil and design specifications. In the simulation, SRK equation is uesd in themodynamic calculation, and simple heat exchanger model is used to simulate the heat exchangers transfer and furnaces. Flow rate and temperature of each product obtained in the simulation are consistent with the practical data of the commercial plant.Based on the data of the commercial refinery factory, this work discusses the effect of adding pump-around circuits and reducing stripping steam flow rate on improving energy efficiency and increasing processing capacity of the atmosphere column. It is shown that both the capacity and energy efficiency of the atmosphere column can be increased by adding pump-around circuits and reducing stripping steam flow rate. The modifications discussed in this work will affect the separation of the atmosphere column in some way. However, the product qualities can still meet the specifications, if the changes in the parameters are not significant. Therefore, the above issues should be considered in the modification overall.There is large amount of low-temperature heat in an atmosphere column. The low-temperature heat can be used in the solvent recovering system of butanone-toluene dewaxing process. The solvent recovering system of butanone-toluene dewaxing process and atmosphere distillation unit are simulated with process simulator. The integration of the low-temperature heat of the atmospheric unit in the solvent recovering system of butanone-toluene dewaxing process is analyzed with Aspen Energy Analyzer. It is shown that the furnace duty of the solvent recovering system of butanone-toluene dewaxing process can be reduced, and the low-temperature heat of atmosphere distillation unit can be utilized. The energy efficiency of the system can be increased by using the modification discussed in this work .The investment pay-back period is about half year.