Studies On The Solubility Of Solids In Supercritical Fluids Using Statiscial Associating Fluid Theory

For the supercritical fluid extraction (SCFE) process design,development and optimization, the solubility of solids in supercritical fluids(SCFs) play a key role, and an accurate model for the calculation of thesolubility is needed. Statistical associating fluid theory (SAFT) hasreceived great attention recently. The SAFT equation of state (EOS) hasgood theoretical basis and physical meaningful parameters and so on. TheSAFT approach is very successful in modeling the phase equilibria of manykinds of systems, especially for complex systems. In this work, the SAFTEOS was used to model the solubility of solids in SCFs and acomprehensive investigation of the capability of the SAFT approach formodeling this kind of processes was firstly carried out,in addition to itswidely use in other fields. Firstly, a SAFT EOS combined with eight mixing rules was usedto evaluate the capability of the SAFT approach for modeling the solubilityof solids in pure SCFs. The results show that the SAFT approach givesgood correlative accuracy in general, and the results are satisfactory whenthe three-parameter mixing rules are used, where the average absolutedeviation of solid solubility in SCF phase is normally smaller than 10%. II北京化工大学硕士学位论文The present work shows that the SAFT approach can be used to modelsolid-SCF equilibria, which gives slightly better correlative accuracy thanthe cubic EOSs. Secondly, based on previous work, the same SAFT EOScombined with a one-parameter mixing rule was used to evaluate thecapability of the SAFT approach for modeling the solubility of solids inSCFs with cosolvents. Whenever possible, the binary interactionparameters were obtained by fitting the phase equilibria data of theconstituent binary systems. The SAFT EOS was used to predict thesolubility of solids in SCFs with cosolvents for five systems, and theoverall average absolute relative deviation (AARD) is 20.43%. For theother twelve systems, the binary interaction parameter of solid-cosolventwas obtained by fitting the ternary solubility data, and the overall AARD is17.58%. The present work shows that the SAFT approach is reliable andcan be used to model the solubility of solids in SCFs with cosolvents withreasonable accuracy.