The feed to a distillation column is a 45.0 mole% n-pentane.-55.0 mole% n-hexane liquid mixture. The vapor stream leaving the top of the column, which contains 98.0 mole% pentane and the balance hexane, goes to a total condenser (in which all the vapor is condensed). Half of the liquid condensate is returned to the top of the column as reflux and the rest is withdrawn as overhead product (distillate) at a rate of 85.0 k mol/h. The distillate contains 95.0% of the pentane fed to the column. The liquid stream leaving the bottom of the column goes to a re-boiler. Part of the stream is vaporized; the vapor is recycled to the bottom of the column as boil up, and the residual liquid is withdrawn as bottoms product.

(a) Calculate the molar flow rate of the feed stream and the molar flow rate and composition of the bottoms product stream.

(b) Estimate the temperature of the vapor entering the condenser, assuming that it is saturated (at its dew point) at an absolute pressure of I atm and that Raoult?s law applies to both pentane and hexane. Then estimate the volumetric flow rates of the vapor stream leaving the column and of the liquid distillate product. State any assumptions you make.

(c) Estimate the temperature of the re-boiler and the composition of the vapor boil up, again assuming operation at 1 atm.

(d) Calculate the minimum diameter of the pipe connecting the column and the condenser if the maximum allowable velocity in the pipe is 10m/s. Then list all the assumptions underlying the calculation of that number.

Feed to column Vapor from top of column Liquid from bottom of column CONDENSER Reflux (liquid) DISTILLATION COLUMN Boilup (vapor) 22 Cooling fluid Heating fluid Distillate (liquid) REBOILER Bottoms product (liquid)