Visual Study On The Extraction Of Organic Solvent By Supercritical Carbon Dioxide

Extraction is one of the means used in the laboratory to purify compounds,and has been the focus of research in the field of chemical engineering.Commonly used extraction methods often require the use of a large amount of organic solvents,causing serious harm to the human body,causing a large amount of waste and organic solvent remained in the extract,and the solute may be deteriorated due to chemical reaction during the extraction process.Supercritical extraction has been widely used in extraction operations due to its mild conditions,easy operation,and no solvent residue.Studying the phase change and velocity vector field information in supercritical extraction process can help to understand and master the extraction mechanism and extraction effect,which can provide theoretical basis and basis for CFD simulation research of supercritical extraction.Based on this,the main research contents of this thesis are as follows:?1?It can be seen from the visual study that CO₂/ethyl acetate/water has a distinct phase interface when the supercritical conditions are not reached.When the pressure reaches 9 MPa,the phase interface becomes blurred,the organic solvent swells,and the volume increases significantly.?2?The extraction efficiency of three organic solvents,ethyl acetate,dichloromethane and acetone,was studied by single factor experiment.When no aeration,CO₂ has low extraction efficiency?<15%?for organic solvents in the presence of surfactants and no surfactants,and extraction efficiency when surfactants are lower than when there are no surfactants.?3?In order to enhance the mass transfer rate and increase the gas-liquid contact area,an aeration device was added to obtain the extraction efficiency of ethyl acetate,acetone and dichloromethane under aeration.The extraction efficiency is significantly increased to about90%.The optimal process parameters were as follows:extraction temperature 42.4?,extraction pressure 9.09 MPa,extraction time 14.59 min.At this time,the extraction efficiency was 97.5%and the results verified was 94.3%.?4?PIV and CFD simulation results show that flow field strengthening has a direct impact on the extraction effect,and there are two vortices of different sizes in the window region.After 30 minutes,the ethyl acetate still has 10%remaining in the kettle.It is necessary to pass supercritical CO₂ multiple times to completely replace the organic solvent.Therefore,an improved method of supercritical extraction,namely secondary extraction,is proposed.The extraction efficiency of the new method is greater than that 95%,and operating parameters such as temperature and pressure have little effect on the secondary extraction.