NAME: ___________________________________________________ DATE: _________________
CO-WORKER’S NAME: ______________________________________________________________
Instructor’s Signature: ____________________
ACTIVITY NO. 5
MULTI-COMPONENT DISTILLATION
CONCEPT:
Distillation is a separation process which is used to separate various components of a liquid solution
which depends upon the distribution of these components between a vapor phase and a liquid phase. The
basic requirement for the separation of components is that the composition of the vapor be different from
the composition of the liquid with which it is in equilibrium at the boiling point of the liquid.
Most of the distillation processes deal with multicomponent mixtures. Processes involving
multicomponent phase behavior are much more complex than that for binary mixtures. For its design
calculation methods, using equilibrium data, equilibrium calculations are used to obtain the boiling point and
equilibrium vapor composition from a given liquid composition or the dew point and liquid composition from
a given vapor composition. Material balances and heat balances are then used to calculate the flows to
and from the adjacent stages. These stage-to-stage design calculations involve trial-and-error calculations,
and high-speed digital computers are generally used to provide rigorous solutions.
For multicomponent mixtures, two components separation are selected of which serves as a good
indication that a desired degree of separation is achieved. These two components are called key
components which are the light key and heavy key. Components that are present in both the distillate and
bottoms product are called distributed components. The components with negligible concentration in one of
the products are called undistributed. Light non-distributed components will end up in the overhead product
while heavy non-distributed components will end up in the bottoms product.
OBJECTIVE:
● To determine the optimum parameters of the distillation system
● To determine the effect of parameter variations on minimum reflux, minimum number of stages, and
actual number of stages in the distillation system.
SIMULATION SOFTWARE:
● WSIM_bin_v57u14_setup
DWSIM - File Name: D
Download here: https://drive.google.com/drive/u/0/folders/1HooNUVVFSbiPmuE2z9fBHh-l-IuqY_YL
● Install and check components (1) DWSIM, (2) ChemSep 8.14, (3) CAPE OPEN Type Libraries, and
(4) Register Type Libraries
PROCEDURE:
For the first objective, there will be different cases/problems to be simulated for each group. Refer below for
the assigned problems. For each problem, a simulation model (DWSIM) will be provided to determine the
requirements.
Download here: https://drive.google.com/drive/u/0/folders/1HooNUVVFSbiPmuE2z9fBHh-l-IuqY_YL
roblem 1 for Group 1, Problem 2 for Group 2, etc.
File Name: P
1. Open DWSIM simulation software.
2. Use the shortcut column provided to obtain initial results. The property package used is Raoult’s Law and
the flash algorithm used is Default. Insert material streams for the feed, distillate and bottoms. Insert energy
streams for the condenser duty and reboiler duty.
3. Supply the necessary feed stream conditions and compound amounts. In the shortcut column, connect
the material and energy streams. Supply the light key and heavy key compounds as well as their mole
fractions. Specify the reflux ratio and condenser type.
4. After all the necessary values are supplied in the simulator, click solve flowsheet. The results are
displayed for the shortcut column.
For the second objective, three parameter variations are considered: decreasing concentration of LK in the
distillate (XLK,D), the concentration of HK in the bottoms (XHK,K), and increased reflux ratio. To do this
experiment, another simulation software will be provided (ChemSep) for a distillation system.
Download here: https://drive.google.com/drive/u/0/folders/1HooNUVVFSbiPmuE2z9fBHh-l-IuqY_YL
arameter Variations
File Name: P
1. In the file, click the figure labelled “Distillation Column 2”.
2. Click Open CAPE-OPEN Object Editor.
Figure 1. Step 1 and 2 in parameter variation
3. After the “Open CAPE-OPEN Object Editor” is clicked, the figure 2 will be displayed. Simply click the
outline labeled FUG.
4. Vary the parameters according to the requirement. Observe the effect on minimum reflux, minimum
number of stages, and actual number of stages.
Figure 2. Step 3 and 4 in parameter variation
To obtain a graphical representation of the process, click the outline named “McCabe-Thiel”.
Problem Assignments
Group 1
A liquid mixture 100 kmol/hr with 4 percent n-pentane, 40 percent n-hexane, 50 percent n-heptane, and 6
percent n-octane is to be distilled at 1 atm with 98 percent of the hexane and 1 percent of the heptane
recovered in the distillate. The n-hexane is the light key and the n-heptane is the heavy key. The reflux ratio
is assumed to be 1.5 of the minimum reflux ratio.
a. What is the minimum number of stages for total reflux
b. What is the minimum reflux ratio for a liquid feed at the boiling point?
c. What are the compositions in the upper and lower invariant zone?
d. What are the temperatures in the upper and lower invariant zone?
Group 2
A given vapor mixture of 100 kmol/hr 50 percent Propylene, 40 percent Propane, 4 percent Acetylene, and
6 percent 1-butene is distilled at 1668 kPa. It is desired to obtain 99 mol% of the propylene in the distillate.
The propylene is the light key component and the propane is the heavy key component. The reflux ratio is
assumed to be 1.5 of the minimum reflux ratio.
Calculate the following:
a. Moles per hour and composition of distillate and bottoms
b. Top and bottom temperature of tower
c. Minimum number of stages for total reflux
d. Minimum reflux ratio
Group 3
Nitrogen and oxygen can be separated by the fractional distillation of liquid air. Air is filtered to remove dust,
and then cooled in stages until it reaches –200 °C, at which point it is liquefied. As the air liquefies, water
vapor condenses, and is removed using absorbent filters; carbon dioxide freezes at –79 oC, and is
removed; oxygen liquefies at –183 oC, and nitrogen liquefies at –196 oC. The air thus liquefied is then
purified by fractional distillation. Liquid air containing 78.0 mole% nitrogen, 21.0 mole% oxygen, 0.96
mole% argon, and 0.04 mole% carbon dioxide enters the top of the column, which operates at 1.4 atm.
Liquid oxygen collects at the bottom and is to be drawn off as product, which is to contain not more than 0.2
mole% nitrogen. Reflux ratio is assumed to be 1.5.
a. Moles per hour and composition of distillate and bottoms
a. Top and bottom temperature of tower
b. Number of stages for total reflux
c. Minimum reflux ratio
Group 4
A liquid mixture 100 kmol/hr with 40 percent n-hexane, 55 percent n-heptane, and 5 percent n-octane is to
be distilled at 1 atm with 98 percent of the hexane and 1 percent of the heptane recovered in the distillate.
The n-hexane is the light key and the n-heptane is the heavy key. The reflux ratio is assumed to be 1.5 of
the minimum reflux ratio.
a. What is the minimum number of stages for total reflux
b. What is the minimum reflux ratio for a liquid feed at the boiling point?
c. What are the compositions in the upper and lower invariant zone?
d. What are the temperatures in the upper and lower invariant zone?
REFERENCE:
Geankoplis, C. (2014). Transport Processes and Separation Process Principles (Includes Unit
Operations) (4th ed.). Harlow: Pearson.
Tambe, S. (2015, April 4). Introduction to multicomponent distillation. Slideshare.
https://www.slideshare.net/sujeet2685/multi-distill
