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TitleLab Report Distillation
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Page 2

Executive Summary

The binary distillation of ethanol and water is made possible due to the difference
in volatilities of the components in the boiling liquid mixture. In this experiment, a
continuous distillation unit consisting of a perforated-tray column filled with packing of
IMTP #15 together with a partial reboiler and a total condenser. This column was used to
find the specifications and optimum operating conditions needed to produce 100 barrels
of strong, 80% mole of ethanol blend beverage from an 8% mole of ethanol mixture
everyday.

In the experiment, all the feed, distillate, bottom, and reflux flow-meters were
calibrated, taking into consideration that the flow meters provide accurate measurements
only for water flows. The refractometer was calibrated to enable the determination of the
concentration of ethanol in any given ethanol and water mixture from the refractive
index. The relationship between the mole composition of ethanol, xEtOH in the mixture to
the density of the mixture, ρ was found to be: ρ = 155.3*exp(-3.1752* xEtOH) +
843.4*exp(-0.05741*xEtOH). The relationship between the density of the mixture and the
composition of ethanol is no longer linear once it reaches higher concentration.

Therefore, the equation: )]*
18

)1822(
(1[ 22

s

Xs

Vs

V
XXs

OHOH
diluted ρ

ρ+
++= was used to

determine the initial ethanol composition of a diluted sample.

The experiment was done by varying the reflux ratio at 6.72 and 7.31, with having
the feed come in the middle stage. Then we kept the reflux ratio at 6.72 and varied the
feed stage which are the middle and the bottom stage. The actual number of stages of the
column used in the lab is 5 stages. To find the number of theoretical stages required for
the stage, the results from the distillation process was analyzed using the McCabe-Thiele
method. By comparing these values, the efficiency of the column was found from the
equation: Efficiency = (# Theoretical stages/# Actual stages). Once up-scaling calculation
was done, we used the new theoretical number of stages to run a simulation in Aspen for
the binary distillation process. Data from the experiment were used as process conditions
to find the heat duty of both the reboiler and the condenser.

When the reflux ratio was set to be 6.72, the purity of ethanol was extremely high,
which shows that the column has very high efficiency. However, because the value was
out of the range provided in the ethanol/water equilibrium curve, it was impossible to
determine the percent efficiency. This high purity gain might be due to the small amount
of the distillate produced. This occurred because it was difficult to maintain the flow rate
of the distillate at the specified value gained from Aspen.

The data from the experiment shows that the optimum specification for the
process is to have the feed enter the column from the middle and a reflux ratio of 7.31.
Even though a higher mole fraction of ethanol was obtained when the feed was at the
bottom, the amount of distillate produced was lower compared to the one when it is fed in
the middle. Moreover, the mole fraction gained from the latter was sufficient with what is

Page 11

Analysis

Design a process to concentrate a mash (8 mole% ethanol in water) to a very strong, but tasty, 80 mole% blend. Need to be able to
produce 100 barrels a day.

Design 1 Design 2 Design 3
Properties Feed Distillate Bottom Feed Distillate Bottom Feed Distillate Bottom

volumetric flow rate (L/day) 1.49E+05 1.19E+04 1.36E+05 1.36E+05 1.19E+04 1.22E+05 1.36E+05 1.19E+04 1.22E+05
mass flow rate (g/day) 1.43E+08 9.75E+06 1.33E+08 1.30E+08 9.75E+06 1.20E+08 1.30E+08 9.75E+06 1.21E+08
ethanol mass flow rate (g
EtOH/day) 2.61E+07 8.88E+06 1.72E+07 2.37E+07 8.88E+06 1.48E+07 2.37E+07 8.88E+06 1.48E+07
water mass flow rate (g
H2O/day) 1.17E+08 8.68E+05 1.16E+08 1.06E+08 8.68E+05 1.06E+08 1.07E+08 8.68E+05 1.06E+08
ethanol mass fraction (g
EtOH/g soln) 0.1820 0.9110 0.1287 0.1820 0.9110 0.1230 0.1820 0.9110 0.1230
water mass fraction (g H2O/g
soln) 0.8180 0.0890 0.8713 0.8180 0.0890 0.8770 0.8180 0.0890 0.8770
ethanol mole fraction (mol
EtOH/mol soln) 0.0800 0.8000 0.0274 0.0800 0.8000 0.0217 0.0800 0.8000 0.0218
water mole fraction (mol
H2O/mol soln) 0.9200 0.2000 0.9726 0.9200 0.2000 0.9783 0.9200 0.2000 0.9782

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