No abstract

A study was made of the effect of physical properties and of geometrical and dynamical characteristics of several liquid-liquid extraction systems on the mass transfer coe5cients. The two-component systems studied consisted of the following solvents with water: cyclohexanol, methyl ethyl ketone, furfural, normal butanol, and nitromethane. The transfer studies were made in a horizontal glass pipe with the phaaes flowing countercurrently at velocities from 1,000 to 15,000 lb./(hr.i(sq. ft.). The transfer of solvents into the water phase and of the water into the solvent phase was measured. The film coefficients of mass transfer for a solvent through the water film and for water through the solvent film were correlated by new dimensionless equations which include interfacial tension and diffusivity.Since 1939 liquid-liquid extraction has assumed considerable importanw as a unit operation of chemical engineering, particularly :is a n adjunct to distillation in the manufacture of organic chemicals and the processing of crude petroleum. Liquid-liquid extraction has proved to bc valuablc in thc scparation of itzcotropic mixtures arid in thc c:oncciitrrition o f ehernicds from dilute solutions. For a long tinic liquid-liquid extraction was considered as the last resort for purification of chcinirals, but with t h r iritroduction of more efficient cquipnicnt designs rcceritly it has heeri winning f:ivor. Iri all the proccsscts nieritioncd in the literature (1 0') considerablc progress has bwn made in t.he devc,lopmcnt of suita1)le equipment and the :icquisition of the necessary opelatirig t4~hriiquc~s. Ido\vrvt~, this progress has I)wn the result of trial arid error in tlvsign and testing. More scientific design of (.xtraction :ippar:itus had to await dwc4opinc:nt of :t nictliod for the corrclatiori of the rate of extraction with the oporatirig viirinbles and the propertics of thc systcms involved.Quantitatively tlie rnerhanism of cxtraction ctnd the c l c~p c t n t l c "~ of extraction ratcs upon pliysicd propertiw and dy- Vol. 2, No. 4v a l u~s thtit arc more funtlamcntal and more widely useful for design purposes, the data are of valuc in the design of cquipmrnt for only thosc systems that have bccn invwtigtited cxperirntmtally.Fcw investigators (9, 8, 10) have attempted to sc?paratc the over-:ill coefficients into the individual rtsistances. They iwrc able to do this only \vhen cttrtuin rcstrictions were applic?d to their rnethod of rcsolution. The rostrictioris set forth (3) require that thc valuc of the distribution eoefficiciit be unity and that either individual corfficicnt (-:in be affected by hoth fluid ratcs but not both together. Invariably all h:ive usc:tl tlie samr niethod of rrsolution, whcrctby the individual rc.sist:incc:s :ire :itldcd to givc: the ovt?r-:tll resistance and a n over-dl coefficient is obtaiiictf as a rwiprocal of the latter. Early data indic:ate (14) that nites of flow of both phases a f h % thc int1ividu:il extraction coefficients of both films and that ncithw p l i u s t~ may be said to...