Design And Simulation Optimization Of Pilot-scale System For Alkaloid Purification Based On Molecular Distillation

Nicotine,also known as nicotine,is the most important alkaloid in tobacco and is widely used in the fields of pharmaceutical synthesis,fine chemicals and nicotine-based biological pesticides.However,there are still many problems in the in-depth development and application of nicotine,such as small scale,low purity and imperfect technology.Therefore,in view of the above problems,starting from the crude nicotine,based on the process simulation calculations,and using the advantages of molecular distillation in purifying heatsensitive and high-boiling natural compounds,the nicotine purification process and system were designed,integrated and optimized,and the steady-state and dynamic simulation of the system is studied.The research content of this paper is mainly divided into the following four parts:First,the physical properties of each component in the raw material system are analyzed from the perspective of thermodynamics,and the advantages of selecting molecular distillation for purification are explained according to the difference of the molecular free path and separation factor of the raw material components.It is calculated that the purification efficiency of molecular distillation is 1.46 times that of distillation.At the same time,according to the characteristics of the molecular distillation separation process,a process flow from crude nicotine to high-purity nicotine with a purity of 99.5 % was established on Aspen Plus.Second,a steady-state simulation of the nicotine purification process was studied.The main equipment parameters in the process were discussed and optimized,and the optimal operating conditions of molecular distillation were obtained: the feed rate was 50 kg/h;the absolute pressure was 100 Pa;and the evaporation temperature was 85 ℃.By comparing the simulation results with the experimental results,it is concluded that the data are in good agreement and the simulation process is reliable.Third,on the basis of completing the thermodynamic analysis and steady-state simulation of the nicotine system,a 50 kg/h molecular distillation pilot-scale system was designed and integrated,which laid the foundation for the industrial application of nicotine purified by molecular distillation.Fourth,on the basis of steady-state process simulation,the dynamic performance of the process is studied.The Aspen Plus Dynamics software was used to simulate the nicotine purification process.Three different system control schemes are formulated based on the technological process.By comparing the dynamic operation conditions under different control structures,the optimal control scheme for the dynamic process is obtained as the temperature-concentration cascade control scheme.