Absorption Heat Pump Distillation Based On Intermediate Heat Transfer Energy Saving System Optimization

Distillation process accounts for about 30%of energy consumption in petroleum refining.Deeply tapping the energy saving potential of distillation waste heat and improving energy utilization rate are important directions in the energy saving field of distillation system.For the depropanizer with a processing capacity of 180,000 t/year,the cascade energy utilization of the distillation column and the efficient utilization of the waste heat at the top of the column are realized.In this paper,an absorption heat pump distillation system based on intermediate heat transfer is proposed,and the comprehensive energy efficiency evaluation method of the new system is established.Based on the basic principle of"temperature matching and step energy consumption",the absorption heat pump distillation system based on intermediate heat transfer is constructed by combining the intermediate heat exchange with heat pump technology.The thermodynamic advantage of intermediate heat exchanger is that the heat source(cold source)temperature can be more matched with the material heating(cooling)demand,and the irreversible loss of the distillation column material heating or cooling process can be reduced by cascade energy utilization.The use of heat pump technology is to prepare heat sources with lower energy quality(compared with the bottom reboiler)by recycling waste heat,and to add cold sources with lower cost(compared with the power consumption of the condenser).In-depth study of the intermediate heat exchanger material extraction position and quantity,the influence on the heating load and cooling load of the distillation column,under the premise of ensuring the normal heat and mass transfer in the tower,considering the heat pump heating performance coefficient COP_h,determine the operating parameters of the intermediate heat exchanger in the distillation column.Aiming at the absorption heat pump distillation system based on intermediate reboiling and the absorption heat pump distillation system based on intermediate reboiling+intermediate condensation,the effects of operating pressure and intermediate material heating temperature on the heating load of the distillation column and the COP_hof the heat pump heating performance coefficient are analyzed,and the optimal working conditions of the new system are obtained to reduce the total steam consumption of the system.Taking the three-column process of gas fractionation with a processing capacity of180,000 t/year as an example,the energy-saving transformation scheme is designed by using the theoretical results of this paper,and the application value of the new distillation energy-saving method is verified around the energy-saving and economic analysis.