The system docosane-diphenylhexane (DPH)-furfural is representative of more complex systems encountered in the solvent refining of lubricating oil. Five hundred kilograms per hour of a 40 wt% mixture of DPH in docosane are to be continuously extracted in a counter current system with 500 kg/h of a solvent containing 98 wt% furfural and 2 wt% DPH to produce a raffinate that contains only 5 wt% DPH. Calculate with a right-triangle diagram the number of theoretical stages required and the number of kilograms per hour of DPH in the extract at 45?C and at 80?C. Equilibrium data are as follows.

The tie lines in the docosane-diphenylhexane-furfural systemare:

EQUILIBRIUM DATA: BINODAL CURVES IN DOCOSANE-DIPHENYLHEXANE-FURFURAL SYSTEM [IND. ENG. CHEM., 35, 711 (1943) Wt% at 45C Wi% at 80C Docosane DPH Furfural Docosane DPH Furfural 0.0 11.0 90.3 50.5 34.2 0.0 9.7 96.0 4.0 84.0 5.0 29.5 20.0 67.0 7.0 26.0 35.8 30.0 36.2 52.5 37.5 10.0 23.8 40.0 32.6 47.4 20.0 16.2 33.8 50.0 21.3 48.7 30.0 10.7 29.3 60.0 13.2 46.8 40.0 6.9 23.1 70.0 7,7 42.3 50.0 4.6 15.4 80.0 4.4 35.6 60.0 3.0 7.0 90.0 27.4 18.5 9.0 2.6 70.0 2.2 0.0 97.8 1.5 80.0 90.0 1.0 0.7 0.0 99.3