Equilibrium Staged Separation Processes

Question :

You are to separate up to 1.000 lbmol.'b (but not less than 500 lbrnol.'b) of a binary tixnire as assigned in the table below into a liquid distillate of 99 mol % of light key (MVC - most volatile component) and a liquid bottoms product of 98 mol % heavy key (or LVC - least volatile component). The feed is a saturated liquid at 55 psia and the colurrin operates at a pressurr in the influx dmni of 18 psia. A totRl COfldenser is used to obtain sstiuated liquid reflex and liquid distillate at its bubble point. A partial reboiler i used at the bottom of the colinnn to produce vapor boil-up and s saturated liquid bottom! icduct.

Answer :

SEPARATION COLUMN DESIGN

To solve the given exercise, I set up ASPEN HSYSY Simulation by adding the components of my system and then choosing the Peng-Robison as Fluid Package. Then I entered into the simulation environment and I choose English Engineering Units for my system. Then I started building my PFD.  First, I entered the feed properties (Vapor Fraction, Pressure, Composition, Molar Flow). The parameters I entered are shown in the below picture.

Figure 1: Feed Conditions

Case 1: Short-Cut Distillation

Then I simulated a Short-Cut Distillation Column according to the provided instructions. I entered 18psia condenser pressure, 24 psia reboiler pressure and external reflux ratio as 1.2 times of minimum reflux ration. The results are shown in the below picture of Hysys Simulation. The toluene is light key component in our case, and it has 99mole% composition in the distillate and 2 %mole composition in the bottom product. 

Figure 2: Short-Cut Distillation

The final results are reported in the below table:

Case 2: Continuous Steady State Distillation

A continuous steady state distillation column was simulated similar to short cut distillation and temperature and pressure profiles of the column are shown below.