Abstract: Limited by the environmental temperature, the operating pressure of the pressurized distillation column is generally higher, and the energy consumption is increased. Taking depropanizing column as an example, if the operating pressure drops from 2.00 MPa to 1.60 MPa, the heat duty of reboiler can reduce by 12.9%. If the operating pressure drops further, it could saves more energy. By using “the cascade heating method for feed of distillation column based on absorption heat pump”, the cooling capacity of the condenser is improved and the temperature of the condenser at gas outlet of the distillation column can be reduced, resulting in lower pressure of 1.30 MPa. At the same time, the waste heat recovered from the gas outlet material is used to preheat the feed instead of steam from the reboiler. The system energy consumption can reduce by 23.3% through the optimization of the new system. On the other hand, the hot water produced by the absorption heat pump can be used as the heat source for the deethanizing column and propylene rectification column, so the waste heat recovery efficiency of the system is obvious.

Key words: distillation, feed temperature, operating pressure, absorption heat pump, energy optimization