Abstract: The energy consumption of atmospheric and vacuum distillation unit is the highest in refinery, and the optimization of heat exchanger network is an effective means of energy saving. Given the variability of crude oils, heat exchanger network that was previously designed for specific crude oils is no longer optimal for other crude oils. A multi-period flexible optimization method was proposed: firstly, Aspen Plus was used to simulate the process of different crude oil periods; then pinch design method was adopted and Aspen Energy Analyzer was used to simulate the current heat exchanger network, identify the pinch position offset, find the unreasonable energy use, and eliminate some common cross-pinch heat transfer by changing the pipeline structure and adjusting the heat transfer matching. The application results in a refinery showed that the multi-period flexible design could save 1 421, 880, 3 842 and 3 421 kW of heating furnace heat load and equivalent cooling water heat load in period 1, 2, 3 and 4, respectively. Further study and flexible design of multi-period heat exchanger network can make greater contribution to energy saving and consumption reduction in refineries

Key words: atmospheric and vacuum distillation, process simulation, heat exchanger network, pinch technology, multi-period, flexibility, optimization