Cascade Distillation Energy Conservation Technology Of Crude Oil And Optimization Of Heat Exchanger Networks

The processing capacity and energy consumption of the atmospheric and vacuum distillation unit is the symbol of a refinery's technology level. Now the technology of atmospheric and vacuum distillation process is mature with little transformation space, and the main problem is high energy consumption. According to the high energy consumption status in crude oil distillation process in china, develop a more optimized cascade distillation process based on comprehensive research and analysis of domestic and abroad advanced theories and technologies, which will provides a suggestion in the construction of new plants and the transformation of old plants for oil refining industry.First of all, optimized operating conditions of conventional atmospheric and vacuum distillation three towers process for comparison using PRO/Ⅱ, the large-scale chemical process steady-state simulation software; then designed atmospheric and vacuum cascade distillation four towers, five towers and six towers processes. Vaporize crude oil with the method of cascade heating and cascade decompression. Separate the vaporization distillate timely and reduce irreversible heating and cooling, in order to achieve the goal of energy conservation. Calculate pinch point of the four processes using ASPEN PINCH software. Design and optimize the heat exchanger networks of the four processes, according to the feasibility rules and experience rules of pinch technology. At last propose utilization and recovery approach of the low-temperature heat of the four processes.Calculate and compare energy consumption of the four processes, based on the same capacity and total distillation yield. Although the recoverable low-temperature heat of cascade five towers process is lower than conventional three towers process's, the energy consumption 10.5% lower than conventional three towers process's, which is due to the input heat of the cascade five towers process is significantly lower than conventional three towers process. The energy consumption of cascade four towers process and conventional three towers process are equivalent; Although the input heat of the cascade six towers process is equivalent with the conventional three towers process, due to the recoverable low-temperature heat of it is lower than three towers proecess's, the energy consumption of cascade six towers process is higher than the conventional three towers process. Carry out a simple technical and economic evaluation of the conventional three towers process, cascade four towers and five towers processes. Comparing with the conventional three towers process, the annual net profit of cascade four towers process is lower, and cascade fiver towers process is higher than conventional three towers process's; the investment payback period of cascade four towers process is longer, but fiver towers process's is quite equivalent with conventional three towers process's. Thus we can find that the cascade five towers process is the best.Therefore, design a new atmospheric and vacuum distillation unit using cascade distillation energy conservation technology, the size of the main equipments will be reduced, but the cost is not significantly reduced. While transform an old atmospheric and vacuum distillation unit using cascade distillation energy conservation technology, the main equipments mainly can be kept invariant or shift for reuse. Using this technology can significantly improve capacity of the crude oil plant, reduce the investment, and shorten construction periods. The energy conservation effect is considerable and the economic benefit is also significantly increased.