7/30/2019 Tutorial 4 2007

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CHEE 317, W 07

Queens University

Tutorial #4

Problem #1

A feed mixture of benzene (B), toluene (T), xylene (X), and cumene (C) is to be separated in adistillation column. Feed rate is 200 moles/hr. Feed concentrations are z B=0.2, zT=0.3, zX=0.1,

zC=0.4. The feed enters as a two-phase mixture that is 30% vapour. The column has a partialreboiler and a total condenser. Feed is returned to the column from the condenser as a saturated

liquid. The specifications require that 99.8% of the cumene be recovered in the bottoms and99.5% of the toluene be recovered in the distillate. The equilibrium data can be presented by

constant relative volatilities. We have decided to operate at total reflux. What is the recovery ofxylene in the distillate? Choosing toluene as the reference, the relative volatilities are benzene,

2.25 toluene, 1.00 xylene, 0.330 cumene, 0.210.

Problem #2

We are separating a mixture that is 10mole% methanol, 20mole% ethanol, 30mole% n-propanol,and 40mol% n-butanol in a distillation column. Methanol is most volatile and n-butanol is leastvolatile. The feed is a saturated liquid. We desire to recover 98% of the ethanol in the distillate

and 97% of the n-propanol in the bottoms product. The column has a total condenser and apartial reboiler. Feed rate is 100 kg moles/hr. Pressure is one atmosphere. L/D = 3.

1. The column is hottest at:

a. The condenser.b. The feed plate.

c. The reboiler.2. In the rectifying (enriching) section:

a. Liquid Flow rate > vapour flow rate.b. Liquid flow rate = vapour flow rate.

c. Liquid flow rate < vapour flow rate.3. Comparing the stripping section to the rectifying section:

a. Liquid flow rate in the stripping section > liquid flow rate in the rectifying section.b. Liquid flow rate in the stripping section = liquid flow rate in the rectifying section.

b. Liquid flow rate in the stripping section < liquid flow rate in the rectifying section.4. The HK is:

a. Methanol.b. Ethanol.

c. n-propanol.d. n-butanol.

5. If you were going to do external mass balances around the column to find B and D, the bestassumption to make is:

a. All of the methanol and n-propanol are in the distillate.b. All of the methanol is in the distillate and all o f the n-butanol is in the bottoms.

c. All of the ethanol is in the distillate and all of the n-propanol is in the bottoms.d. All of the n-propanol and n-butanol are in the bottoms.