THE SIMPLE BLOCKS - Teach Yourself the Basics of Aspen Plus - page 44

TABLE 3.1 Stream Specifications for Workshop 3.1a
Stream/

Temperature Pressure Flow Rate Vapor

( ◦ F)

Component (psi) (lbmol/hr) Fraction

1 200 300

C3 20

NC4 30

NC5 30

NC6 20

2 250 400

C3 30

NC4 30

NC5 20

NC6 20

3 200 0.5

C3 50

NC4 0

NC5 30

NC6 20

1. 50% of the combined feeds are to be directed to stream D.
2. 50 lbmol/hr of NC4 will exit in stream SS.

Solve the flowsheet. Is something wrong? What? Why?

Workshop 3.2b Change Workshop 3.2a such that 20 lbmol/hr of NC4 exits in stream
SS. Solve the flowsheet. What do you observe?

Workshop 3.3a A two-feed, two-product distillation column operating at 1 atmo-
sphere is to be simulated using the Sep2 block. The system components are methanol,
water, and normal hexane. You may assume that the system thermodynamics can be
represented by an ideal vapor phase and the Unifac correlation for the liquid phase.
The componential flow rates of the first feed, a saturated liquid at 14.696 psi, are 50
lbmol/hr of methanol and 100 lbmol/hr of water. The second feed flow rate is 150
lbmol/hr of pure n -hexane at 120 ◦ F and 14.696 psi. Both feeds are at 1 atmosphere
and are saturated liquids. The column performance specifications are as follows:

1. One-half of the methanol fed is to be recovered in the overhead product.
2. 99% of the water fed is recovered in the overhead product.
3. 99% of the n -hexane fed is recovered in the bottom product.

Set up the problem and solve.

Workshop 3.3b Specifications 2 and 3 above are to be changed as follows:

2. The mole fraction of water in the overhead product is 0.788.
3. The mole fraction of n -hexane in the bottom product is 0.85.

Modify Workshop 3.3a and solve.