The system docosane–diphenylhexane (DPH)–furfural is representative of complex systems encountered in the solvent refining of lubricating oils. Five hundred kg/h of a 40 wt% mixture of DPH in docosane are to be extracted in a countercurrent system with 500 kg/h of a solvent containing 98 wt% furfural and 2 wt% DPH to produce a raffinate of 5 wt% DPH. Calculate, with a right-triangle diagram, the stages required and the kg/h of DPH in the extract at 45^οC and 80^οC.

The tie lines in the docosane–diphenylhexane–furfural system are:

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BINODAL CURVES IN DOCOSANE-DIPHENYLHEXANE- FURFURAL SYSTEM (IND. ENG. CHEM., 35,711 (1943)] Wt% at 45°C Wt% at 80°C Docosane DPH Furfural 4.0 5.0 7.0 10.0 20.0 30.0 96.0 84.0 67.0 52.5 32.6 21.3 13.2 7.7 4.4 2.6 1.5 1.0 0.7 0.0 11.0 26.0 37.5 47.4 48.7 46.8 42.3 35.6. 27.4 18.5 9.0 0.0 40.0 50.0 60.0 70.0 80.0 90.0 99.3 Docosane DPH 90.3 0.0 50.5 29.5 34.2 35.8 23.8 36.2 16.2 33.8 10.7 29.3 6.9 23.1 4.6 15.4 3.0 7.0 2.2 0.0 Furfural 9.7 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 97.8