Simulation And Thermodynamic Study Of Heat Pump Distillation System

In the field of chemical separation,distillation technology is the most widely used.However,the problem of high energy consumption and low thermal efficiency in distillation process is serious.Based on this,this paper tak es propylene-propane near boiling compound as the research object,and takes heat pump distillation system as the research focus.Through the simulation study of heat pump distillation system,the separation rule of matter system and the energy-saving situation in the distillation process are mastered,which provides certain data reference for realizing energy-saving production and design.Finally,based on the generalized Carnot theorem,the conversion mechanism between heat transfer and work in heat pump distillation system is analyzed theoretically,which provides a new direction for the development of energy saving technology in distillation process.The research contents and results of this paper are as follows:(1)The composition of different distillation system and heat pump distillation system is compared and analyzed.Based on the principle of energy saving technology of distillation,four energy saving systems of multi-effect distillation,heat pump distillation,heat-coupled distillation and internal heat integration distillation were studied and analyzed.Based on the different structures of steam pressure heat pump distillation system,the energy saving technology of heat pump distillation was further studied,and the energy saving scheme suitable for the separation technology of propylene and propane near boiling compound was determined.(2)The phase equilibrium of propylene-propane system was studied,and the numerical simulation of propylene distillation column was carried out by using Aspen Plus simulation software.The phase equilibrium of propene-propane system was studied by PR equation of state.The sensitivity analysis tool was used to optimize the operating parameters of the distillation system,and the optimum values were determined comprehensively.At the same time,the simulation research on energy saving of three different structure heat pump technologies,namely tower direct compression type,tower kettle flash reboiler type and split type,was carried out for propylene distillation tower.The results show that the total energy consumption of the distillation system is reduced by14.6% after parameter optimization.Three different structures of heat pump distillation system have achieved the purpose of energy saving.(3)The thermodynamic model of conventional distillation system and heat pump distillation system is established.Through thermodynamic efficiency calculation,energy consumption calculation and economic evaluation,the energy saving analysis of conventional distillation,distillation system with optimized operation parameters,tower direct compression,tower kettle flash reboiler and split type heat pump distillation system was carried out.The results show that the reboiler heat pump distillation system has the highest thermodynamic efficiency,which increases by 163%.Tower direct compression heat pump rectification system is the most energy saving,saving 72.7%.Direct compression heat pump rectification system at the top of the tower h as the lowest annual total operating cost,saving 68.2%.Finally,The direct compression heat pump system at the top of the tower and the flash reboiling heat pump system at the bottom of the tower were selected to transform the process of a hexane oil distillation unit.The total energy consumption was about55% and 43.9%,respectively.(4)Based on the generalized Carnot theorem,the thermodynamic coupling mechanism contained in the heat pump distillation process is theoretically studied by using the generalized heat engine and heat pump model,that is,the thermodynamic mechanism between the heat transfer process driven by temperature gradient and the generalized work process driven by chemical potential gradient.The thermodynamics of heat pump distillation process is explained from a new Angle to reveal the energy conversion mechanism,tha t is,positive entropy production rate,spontaneous thermodynamic process drive negative entropy production rate,non-spontaneous thermodynamic process.It expands a new idea for energy saving technology in distillation process from main structure optimization innovation to local structure design optimization.