A depropanizer distillation column is designed to operate at an average total pressure of 315 psia for separating a feed into distillate and bottoms with the flow rates shown next:

The thermal condition of the feed is such that it is 66 mol% vapor at tower pressure. Steam at 315 psia and cooling water at 65oF are available for the reboiler and condenser. The total pressure drop across the column may be taken to be 2 psi as a first approximation.

(a) Should a total condenser be used for this column?

(b) What are the feed temperature, K-values, and relative volatilities (with reference to Cg) at the feed temperature and pressure?

(c) If the reflux ratio is 1.3 times the minimum reflux, what is the actual reflux ratio? How many theoretical plates are needed in the rectifying and stripping sections?

(d) Compute the separation of species. How will the separation differ, if a reflux ratio of 1.5, 15 theoretical plates, and feed at the 9th plate are chosen.

(e) For part (c), compute the temperature and concentrations on each stage. What is the effect of feed plate location? How will the results differ if a reflux ratio of 1.5 and 15 theoretical plates areused?

Transcribed Image Text:

Ibmol/h Distillate Feed Bottoms Methane (C) Ethane (C2) Propane (C3) n-Butane (Ca) n-Pentane (Cs) n-Hexane (C6) 26 26 6. 25 24.6 0.4 17 0.3 16.7 11 11 12 12 Totals 40.1 100 59.9