The Research On Energy-saving Characteristics And Thermodynamics Of Ethanol Heat Pump Distillation

Ethanol is an important chemical product,widely used in medical and health care,food processing,chemical production and automotive fuel and other daily life fields.As energy shortage and environmental pollution become more and more serious worldwide,ethanol as a new clean fuel is becoming the focus of people’s attention.The distillation process is the main part of the ethanol production process,which has many disadvantages such as high energy consumption,low thermodynamic efficiency and poor separation effect.Heat pump distillation is a new chemical technology with high efficiency and energy saving.However,due to the complex heat and mass transfer process of distillation,the research on the thermodynamics of the heat pump distillation system is not deep enough.In order to improve the energy saving characteristics of the ethanol distillation system,the thermodynamic effect of the ethanol heat pump distillation system was discussed.In this thesis,the state equation of ethanol is analyzed based on the solution characteristics of the ethanol-water system.Then,the direct compression ethanol heat pump distillation system,the applied working medium ethanol heat pump distillation system and the partition ethanol heat pump distillation system were established.The structure and working principle are introduced in detail to provide a basis for subsequent research.Secondly,Aspen plus software was used to simulate three different heat pump distillation systems,and the parameters of the distillation column were optimized.On this basis,thermal integration analysis of the heat pump distillation system was carried out.Finally,a thermodynamic model of the ethanol heat pump distillation system was established.Based on this model,the results of thermodynamic calculation were analyzed from the aspects of heat loss of distillation column,system performance and heat pump circulation.In addition,the thermodynamic effect,energy consumption and operating cost of the ethanol heat pump distillation system were evaluated.The results show that the relative volatility of ethanol and the phase equilibrium constant of ethanol and water are obtained by analyzing the characteristics of ethanol-water solution and the ethanol state equation.Aspen plus software was used to simulate and calculate heat pump distillation systems with different structures.Simulation results show that the optimal separation point of the separation system is 0.31 ethanol concentration,the optimal feeding position of the direct compression system is the 15 th tray,and the optimal reflux ratio of the external working medium system is 4.6.By comparing the simulation results and theoretical calculation results,the error between them is less than10%,indicating that the thermodynamic model has high reliability.Compared with the traditional distillation system,the fractional ethanol heat pump distillation system has the advantages of the highest thermodynamic efficiency,the lowest energy consumption and the lowest operating cost.