ECH4404L: Unit Operations Lab II
Instructor: Dr. Loren B. Schreiber
Senior Lab Engineer: Mr. Richard Crisler
Teaching Assistant: Mike Kirkpatrick
Team Leader: Calvin Alleyne
Safety Officer: Tehra Bouldin
' Operation and Data Acquisition Details
' Introduction to Experiment 350 :
' Physical Situation
' Plan of investigation
' Experiment 350 involves the removal of ethanol
from a 40% ethanol / 60% n-heptane mixture
(percentages based on mass).
' The organic mixture is fed counter-current to the
extraction solvent, water, to a 6 foot high, 1 inch
diameter Karr extraction column.
' The vertical column houses reciprocating plates
that agitate the n-heptane, allowing for more
solvent flow rate for 99.5% removal of ethanol from the feed
speed of reciprocating plates to remove 99.5% of the ethanol
from the feed using 65% and 35 % of the initial solvent flow
theoretical number of stages necessary for the separation
the reproducibility of the measurements
' Gain experience working with an
' Learn to use a Gas Chromatagraph in
a real world application.
The countercurrent extraction of ethanol from
heptane to water occurs mostly because of the
solubility differences of ethanol in these two
solvents. Ethanol is more miscible in water than in
The reciprocator plates housed in the Karr
extractor column have an impact on the extent of
extraction as well. Physically the plates disperse
the ethanol-heptane bubbles as they rise through
the water. The reduction in the volume of the
individual bubbles allows for more surface area
of the bubbles to be in contact with the solvent.
Due to the increase of surface area more mass
transfer can occur, as the ethanol leaves a non-
aqueous phase liquid (heptane) and dissolves into
Ternary system data provided by Dr. Schreiber in the
laboratory was highly helpful, allowing for a plot of the
equilibrium curve. Also, "tie-line" data was provided for the
components of the ternary system.
Using a procedure outlined in Transport Process and Unit
Operations (Geankopolis) an equilibrium plot was created
with Microsoft Excel using the "tie line" data. The "D point"
was then extrapolated from the "tie line" data. From this
plot, the theoretical number of equilibrium stages of the
extractor column was calculated.
Ternary Plot: 2d
Let L0 = initial mass flow rate of feed;
xethanol = mass fraction of ethanol in feed;
xheptane = mass fraction of heptane in feed;
Vn = the mass flow rate of the solvent (water) entering the
Vn+1 = the mass flow rate of the raffinate;
yheptane = mass fraction of heptane in raffinate;
yethanol = mass fraction of ethanol in raffinate
Mass Balance (cont.)
Ln = the mass flow rate of the extract leaving the column;
x'ethanol = mass fraction of ethanol in the extract;
x'heptane = mass fraction of heptane in extract;
x'water = mass fraction of water in the extract
Special note: 1- x'ethanol - x'heptane = x'water
Mass Balance (cont.)
L0 + Vn = Vn+1 + Ln
Species Balance on Ethanol: xethanol L0 = yethanol Vn+1 + x'ethanol Ln
Species Balance on Heptane: xheptane L0 = yheptane Vn+1 + x'heptane Ln
Mass % Conversion of Ethanol:
100% + ((yethanol Vn+1 + x'ethanol Ln) - (xethanol L0) / (xethanol L0)) = mass %
conversion of ethanol
' Proper Personal Protective Equipment must be worn at all
times during this experiment. This includes:
' Goggles (NO CONTACTS)
' Close-toed leather shoes, Jeans
' No loose clothing
' Gloves when dealing with any chemicals
' Hard Hats in the designated area
' n-Heptane and Ethanol-Signs of acute exposure:
' Skin-irritation, redness, and pain
' Eyes-Irritation, redness, and pain
' Inhalation-Irritation of respiratory track. Aspiration into
lungs can cause severe lung damage
' Ingestion-Nausea and abdominal pain
' First-Aid Measures:
' Skin- Flush the skin with water and soap for at least
15 minutes. Remove contaminated cloths and wash
before wearing again.
' Eyes- Flush the eyes with water for at least 15
minutes. Get medical attention.
' Ingestion- Aspiration hazard. Get medical attention
and seek medical attention immediately.
Operations and Data
' Calibrating the Pumps
' Calibrating the GC
' Data Acquisition
' Close the valve that runs into the column and open solvent
valve to allow the liquid to flow into a jar placed on the mass
' Set the flow rate on the rotameter and turn on the pump to
start the liquid flowing. Time for 1 minute after flow stabilizes
Record the mass at the initial and the final times.
' Repeat the measurement at the set flow rate at least twice for
' Standard Preparation
' Sample Injection
' Data Analysis
' Prepared Samples:
' 0.2, 0.4, 0.6, 0.8, 1.0% Ethanol
' At least 2 GC's performed on each standard
' Analyzed the data based on the average
area percent of the ethanol peak given by
' A linear regression of the data gives:
(Area %) = (% Ethanol)*0.723 -0.0721
GC Sample Injection
' Shake the sample for 30 seconds in the bottle .
' Take the cap off.
' Wipe the microsyringe needle clean.
' Flush the syringe 3 times with sample, ejecting into
' Draw 10 microliters into syringe. Invert and push
out some fluid while tapping. Set mark at 1
' Aim, push in, inject, press run and withdraw.
' Cap sample.
Standard Calibration Curve
Area % vs % Ethanol
Avg Area %
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
' Raffinate Samples:
' Methods of taking samples
' Sample Analysis using the GC
' Extract Samples:
' Methods of taking the samples
' Sample Analysis using the Pcynometer
' Unscrew top of raffinate collection
' Wash the sample bottle three times with
the raffinate. Fill to top and cap.
' Label with sample #.
' Shake bottle for 30 seconds.
' Run 2 GC's
Raffinate Data Analysis
' Average the area percent response given
by the GC for each sample.
' Use the calibration curve from the
standards to determine the percent of
ethanol in the sample.
% Ethanol in the Raffinate
vs Sample Number
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
' Sampling Method
' Fill the pycnometer with the extract and weigh
' Measure the temperature of the solution
' Clean out and dry the pycnometer and repeat
Extract: Data Analysis
' Determine the density of solution using
the recorded mass and the known
' Using published data relating the
percentage of ethanol in water to
solution density, perform a quadratic
' Using the regression, determine the
percentage of ethanol in the extract
' Safely shutting down the extraction
' Disposal of waste:
' Feed, extract and raffinate
' Samples taken from the Raffinate
' Samples taken from the Extract
' Visual inspection
The removal of ethanol from the feed occurred at a minimum of
99.2% via mass from our experimental data (with 35% of the
solvent flow rate) and a high reciprocator plate speed (approx. 100
cycles / minute)
Our solvent flow rate at 35% was too small for proper removal of
99.5% of ethanol via mass (we picked too low of a feed flow rate,
which implies the 35% solvent flow rate) even though plate speeds
were in excess of 100 cycles / minute
The plate speed of about 50 cycles / minute kept our removal at
approximately 99.5% while at 65% of the solvent H2O flow rate
" At approximately 0.6 g/s of water (solvent flow rate into
the system) we achieved 99.5% removal
" Although the theoretical data provided was "slightly
skewed" (at a lower temperature 25C) than the
experimental data (approximately 33C),
" the equilibrium data provided by Dr. Schreiber was
consistent with the experimental data, specifically the
equilibrium curve calculating the equilibrium number of
stages (drawn out from a procedure outlined in
Thanks go to:
' Dr. Pedro Arce
' For taking time out of his busy schedule to listen to
' Dr. Loren B. Schreiber
' For providing us the opportunity to learn.
' Mr. Richard Crisler
' For keeping the GC running.
' Mike Kirkpatrick
' For keeping us straight.