1 Distillation Column

1
1
Distillation Column
1.1 Description of Apparatus
Contents
DC
PS
PP
PB
GP
HX
MR
IX
TD
The distillation experimental station consists of a distillation system (column, reboiler, product and fees tanks, condensers, reflux splitter, etc.), a process control computer, and a gas chromatograph.
The column consists twelve bubble cap trays, which were eight inches in diameter. Each tray
contains five bubble caps. The bubble caps allow vapor to pass upward from the tray below and
condense while allowing liquid to pass back. Each tray is spaced six inches apart and is numbered
one to thirteen but there is no tray eight. Possible feed locations are at trays 3, 5, 7, 9, and 11. A
thermocouple at each tray monitors the temperature, while spigots located at each tray allow for
the collection of liquid and vapor samples. Four viewing ports are positioned on the column, two
ports at the top, and two ports midway up the column.
Two heat exchangers are located above the column. One exchanger is used to preheat the feed
using hot vapor from the top of the column. The second exchanger acts as a condenser, using cooling water to condense the vapor leaving the first exchanger. The inlet and outlet temperatures of
the cooling water are monitored by thermocouples to determine heat exchanged. The condensate
flows into a reflux tank. From the reflux tank, the condensate can be refluxed back to the top of the
column and/or directed to the product tank.
A reboiler heated by steam is located at the bottom of the column. A thermostat two spigots
for sample vapor and liquid collection, a steam pressure gauge hooked and a level meter monitor
the performance of the reboiler. The bottoms stream passes through a chiller to ensure that no
vapor enters the bottoms t tank.
The reflux tank, products tank, two bottoms tanks and feed tank are located next to the column. A level gauge is attached to each tank to indicate the amount of fluid. The feed tank initially
contains 20% methanol, by weight, and 80% water. During continuous operation, the feed tank
can be replenished from the products and bottoms tanks.
A computer is used to monitor process variables. The computer records tray temperatures and
temperatures at the reboiler, the chiller, and the condenser. The program also allows adjustment of
feed flow rate, reflux ratio, and the steam pressure. All flow rates can be determined manually
using the rotometers located throughout the apparatus.
A Hewlett Packard 5890 Series II Gas Chromatograph (GC) is used to analyze composition of
collected samples. A sample of the solution is injected into the port to scan the spectrum. The
height of the peaks correspond to the amount of methanol and water. The instrument should be
calibrated at the beginning of each lab period using various concentrations of methanol in water
(for example: 0%, 25%, 50%, 75%, 80%, 85%, 90%, 95%, and 100%).
1.2 Experimental Procedure
I.
Operating the Column:
A.
The technicians should start the distillation column at least three hours in advance
of the scheduled time in lab.
2
B.
C.
D.
E.
F.
Contents
G.
DC
H.
PS
I.
PP
J.
PB
K.
GP
L.
M.
N.
HX
O.
MR
P.
IX
Q.
R.
TD
S.
Open the valve on the side of the column to select the feed tray.
From the computer terminal and the calibration chart proportioned by the technicians, set the feed flow rate, the reflux ratio and bottom flow rates.
Take readings of the flow rates from the flow meters behind the computer terminal.
Wait until the flows are stable.
The level in the reflux tank, shown by the level monitor in front of the tank, must
contain some liquid and remain constant over time.
The reflux flow rate, shown by the flow meter in front and to the right of the reflux
tank, must remain constant.
Take a sample of the feed composition from the storage tank near the distillation
column.
Make sure that the reboiler level is within the green range shown on the liquid level
meter on the side of the reboiler. This is a good way to avoid weeping and flooding
conditions.
From the main screen of the computer, record the temperatures of all the trays.
(This represents the temperature profile in the column.)
After 10-15 minutes, compare the recorded temperature profile with the actual
temperature profile currently on the computer screen.
If the temperature profile has changed, record the new set of temperatures.
Wait another 5-10 minutes and compare temperature profiles again.
If the temperature profile has not changed, the column is at steady state and samples can be taken. (Note: that at steady state, temperatures can fluctuate within a
small range (0.2 ˚C.)
Depending on the objective of the lab, samples can be taken at the trays and/or
from spigots located underneath the storage tanks behind the flow meters.
Depending on the objective, adjust the feed, reflux, and/or bottoms flow rate and/or
steam pressure. Repeat the process starting from step C.
Take a sample of the feed composition from the tank at the end of each lab period.
After four or five different reflux flowrates have been analyzed, shut down the distillation system. This can be done using the computer terminal.
Clean the glass sample containers and shut down the GC.
II.
Procedure to measure the steam flow rate:
A.
Weigh a clean, empty 200 ml glass container
B.
Locate the steam coil behind the reboiler at its base.
C.
Fill the coil container with ice to condense the steam.
D.
Open the valve that connects the main steam exit with the coil condenser.
E.
Close the main steam exit.
F.
Record the time that it takes to fill the 200-ml flask.
G.
Weigh the amount of material collected in the 200-ml container.
H.
Calculate the steam flowrate by dividing the mass of condensate by the time it
takes to fill the container.
III.
Procedure for the GC analysis:
A.
Calibrate the equipment with specific concentrations of methanol in water.
B.
The GC prints the data out as an area plot that is proportional to the compositions.
3
C.
D.
E.
Put the samples into the injection port of the GC.
Collect the data from the samples.
Compare with the calibrated results.
1.3 Software
Contents
THE MENU:
DC
1).
SELECT DATA SAVED
Look at 5) first to see how the data is stored. Take note of the
DDIN!(#) items that you wish to save. Go to 2) and execute.
PS
2).
AUTO DATA SAVE This option sets up the data save. Name the file, time between samples and the sample period. e.g. Sample time between seconds is 3 seconds and the sample
period is 20 seconds. This means that every 3 seconds one set of data selected will be
saved. This will happen every three 3 seconds for 20 seconds and then stop. If you press
the'S' key again the process will be repeated. The next set of data will be added to the bottom of the previous set. The set numbers will increase for each sample set. 12001, 12002
and 1200n.
3).
CHANGES & PUMPING This option allows you to change the settings of the flowrates.
Currently the flowrates must be read from the rotometer as they are being set. We are currently searching for hardware that can be set and will monitor flowrates within a reasonable tolerance.
4).
RETRIEVE DATA Data that has been previously saved can be retrieved and examined.
There is a provision to look at a few screens at a time.
5).
DATA FORMAT This is the format by which the data is stored in the system. The first set
of saved data contains the labels for the data. Subsequent data is without the labels to conserve space.
6).
SET CONTROL CONDITIONS One stream at a time can be controlled. This options
allows you to input the control constants that you learned how to calculate in the control
course. The current algorithm is called “VELOCITY ALGORITHM” on page 615 of
PROCESS DYNAMICS AND CONTROL by Seborg, Edgar and Mellichamp.
7).
GRAPH OPEN LOOP
option.
8).
DIAGRAM This diagram relates the thermocouples with the numbers found in 5). above.
9).
SHUT DOWN Will do what it implies.
PP
PB
GP
HX
MR
IX
TD
The open loop response can be observed and saved using this
TEST DISPLAY One value from 5). above can be monitored. You must enter 10) again to
turn the display off by entering -5.
4
RUN STARTUP The column will be automatically started. When the operating temperature is reached, The #1 thermocouple is reading above 70 ˚C., the column is automatically
switched over to a full reflux mode of operation.
STARTUP INSTRUCTIONS This is self explanatory.
Contents
RUN PROGRAM Choose this option after any menu selection.
DC
CHECK OVER RIDE For maintenance purposes only. Not working at this time.
PS
1.4 References
PP
McCabe, and J. Smith, Unit Operations of Chemical Engineering, McGraw-Hill, New York
(1976).
Treybal, R., Mass Transfer Operations, 3rd ed., McGraw-Hill, New York (1980).
PB
GP
HX
MR
IX
TD
5
2
Polymer Synthesis
2.1 Description of Apparatus
Contents
DC
PS
PP
PB
GP
HX
MR
IX
TD
The polymerization experiment that consists of three main components: a dilatometer, a paraffin oil bath, and a cathetometer.
The dilatometer is a U-shaped piece of glassware comprised of three sections. The reaction
section is the main bulb and holds the majority of the solution. The capillary section is a thick
walled tube. The filling section consists of a thin walled glass tube with a stopcock affixed to its
end. This section is used to transfer the reaction liquid into the reaction section and to remove the
solution after the experiment. The stopcock also prevents the solution from spilling out.
A five-gallon paraffin oil bath is used to maintain the temperature of the solutions in the
dilatometer. The left side bath was heated by an Omega CN 9000 heating coil, while the right side
utilized an Omega 6100 model. Temperatures are preset using the device on the heaters, and are
monitored using standard thermometers. Mixers keep the baths well stirred so that no temperature
gradients occurred throughout the oil.
The cathetometer is a telescoping lens that focuses on the capillary section of the dilatometer.
The collection optics ride on a vertical track. By turning a threaded screw the vertical position of
the optics may be adjusted. A graduated scale attached to the track records the position of the collection optics. The height of the meniscus is measured by aligning crosshairs in the optics to the
meniscus and reading the corresponding position on the graduated scale. The time was monitored
with a stopwatch provided by the laboratory technicians.
During sample preparation, a Fisher magnetic stirrer and a Thermolyne Sybron hot plate, type
1900 are used to allow for complete mixing and dissolution,. All balance measurements were
taken on a College Mettler Toledo balance with maximum capacity of 151 g.
2.2 Experimental Procedure
I.
Setup
A.
Technicians preheat paraffin baths to desired temperature
B.
Clean all glassware thoroughly
II.
Prepare 0.1 M NaOH
A.
Weigh out 1.2g NaOH
B.
Mix with 600mL distilled water
III.
Prepare MMA solution
A.
Pour our 600mL of MMA stock solution into 1500mL flask
B.
Add 600mL of the NaOH solution
C.
Mix 1200mL solution and allow time for separation
D.
Decant lower layer and discard in waste bottle
E.
Now there will be 600mL of inhibitor free MMA
F.
Fit a Buchner funnel with a piece of filter paper and fill with 3 A molecular sieve
G.
Dry MMA over sieve
6
H.
IV.
Making run solutions (mixing solvent if required, MMA and AIBN)
A.
Tare 150mL beaker
B.
Weigh out desired grams of MMA
C.
Pour MMA into 250mL flask
D.
Weigh out desired AIBN
E.
Add to MMA
F.
Mix with magnetic mixer
G.
Weigh out desired out desired solvent amount
H.
Add to flask
I.
Mix until solution no longer appears white
V.
Loading the dilatometer
A.
Place the three-way rubber pump on the filling end of the dilatometer
B.
Make sure stopcock is open
C.
Place capillary into solution and pump
D.
Once bulb is filled close the stopcock
E.
Tip dilatometer right side up, open stopcock fill the solution bulb to the top and to
the bottom of the stopcock
F.
Close stopcock, get rid of air bubbles
VI.
Performing experimental runs
A.
Place dilatometer in the oil bath and clamp into position
B.
Have paper towels in hand, just in case the dilatometer is overfilled
C.
Set cathetometer to 40 cm line
D.
Watching through telescope record time when crosshair aligns with meniscus
E.
Move cathetometer setting to 39 cm and repeat until 9 cm is reached
VII.
Cleaning
A.
Remove the polymer solution from dilatometer before it solidifies.
B.
Dispose of material in MMA waste
C.
Rinse twice with acetone
D.
Rinse once with deionized water
E.
Rinse once with acetone
F.
Dry dilatometer with compressed air.
Contents
DC
PS
PP
Discard used sieve
PB
GP
HX
MR
IX
TD
2.3 References
Burnett, G.M., G.G. Cameron, and M.M. Zafar, “Polymerization of Methyl Methacralate in
Solution,” European Polymer Journal, 6, 823-830 (1970).
Clouet, G. and P. Corpart, “Studies on Bulk Polymerization of Methyl Methacralate. I. Thermal Polymerization,” J. Polym. Sci. A, 31, 2815-2824 (1993).
Fogler, S.M., Elements of Chemical Reaction Engineering, Prentice Hall, New Jersey (1992).
Odian, G., Principles of Polymerization, Wiley, New York (1981).
7
Seymour, R.B. and C.E. Carraher, Polymer Chemistry: An Introduction, Dekker, New York
(1992).
Contents
DC
PS
PP
PB
GP
HX
MR
IX
TD
8
3
Polymer Processing
3.1 Description of Extrusion Apparatus
Contents
DC
PS
PP
PB
GP
A model KL-125 Killion extruder is the apparatus used in this experiment. The extruder consists of a motor, panel, barrel, screw, and die. A computer system controls experimental conditions.
A 230V Seco DC (direct current) motor produces motor speeds ranging from 87 to 1750 rpm
and drives a 24 inch flame hardened screw. The tachometer controls the screw speed and has a
range from zero to 215. Manual calibration by either a flashlight or strobe light gun of the screw is
necessary to determine the correct speed.
The screw is located inside a barrel made of Xaloy-306 and is heated in three different zones:
the feed zone, the transition zone, and the metering zone. These zones are heated by five heater
bands per zone. A round protective cover encircles the barrel allowed for no venting. Temperatures along the barrel is measured by thermocouples, located at five different positions: the die,
the head, the feed zone, the transition zone, and the metering zone. The computer allows for
changing and monitoring the temperatures.
The die can be changed for different experiments. All dies have a circular geometry and vary
in length and diameter.
HX
Cooled samples were weighed with a Mettler Toledo balance with a maximum capacity of 510
grams.
MR
3.2 Experimental Extrusion Procedure
IX
The following is a list of the procedures, which is needed for the proper operation of the Killion extruder.
TD
The laboratory technicians turn on the computer, the main power supply to the extruder, the
control system, and the cooling water. Installation of the correct die is also done by the technicians before they heat up the extruder. The technicians also preset the temperatures.
Make sure the appropriate safety procedures are being followed upon entering the lab. These
include wearing safety goggles, checking that the hopper is in place, and wearing protective
gloves when working around the die end of the extruder.
The computer is used to set the temperatures of the five zones. These five zones are the feed
zone, the transition zone, the metering zone, the head (just before the die), and the die. The best
temperatures are such that the first two zones are just below the melt temperature of the polymer;
the next two are around the melt temperature, and the last one just above the melt temperature.
Temperatures sometimes oscillate due to the control system.
Before the screw speed can be set, the temperatures need to be constant. If the screw is started
before the extruder is up to temperature, problems may arise due to left over polymer in the
extruder.
Fill the hopper half full with polymer pellets.
9
Fill the metal waste bucket at least half full with water, and place it so that it can collect and
cool the extruded polymer that leaves the die.
Contents
DC
PS
PP
PB
GP
HX
MR
IX
TD
Set the screw speed using the knob on the control panel (the speed should be at the lowest possible setting). Rotation is then started using the black start button, and the speed is increased to the
desired value.
The values shown on the screw speed dial represent the amount of power that is supplied to
the motor turning the screw. These values are not a direct correlation of the speed of the screw.
The speed setting is monitored on the computer but is inaccurate, and needs to be determined
manually.
Calibrate the screw speed by counting the number of screw rotations for a set time interval (30
seconds). The screw can be seen with a flashlight through the window guarded with wire mesh.
This window is on the side of the extruder opposite that of the die.
Observe the condition of the extruded polymer to determine the correct operating temperatures. If the polymer is yellow or sticking to the metal sheet at the exit of the die then the polymer
is burning and the temperatures need to be lowered. Yet, if the polymer is cloudy and thick in
appearance the temperature is too low and needs to be increased.
The next step is to start collecting the data. One person needs to be at the computer monitor to
record pressure gradients and temperatures as each sample is collected. A second person needs to
use a stop watch to time the ten second runs, while the third person, wearing gloves, is at the die
ready to collect the samples. To collect the samples the polymer must be cut with a spatula and
placed on a metal tray to cool.
Once the data has been collected, the pressure drops, stream temperatures, and masses are
averaged. These average values are then used throughout the data analysis.
When at least five speeds have been analyzed for the die, the screw is stopped from rotating by
turning the screw speed dial to zero and then pressing the red stop button. Shutting off the temperature at the head and die zones, allows the apparatus to cool down enough to be handled by the lab
technicians so that they can change the die.
Turn the temperatures back up to the desired points, and allow for the temperatures to reach a
steady value. At this point a new experiment can be started.
At the end of each lab day, turn the screw speed dial to zero and press the red stop button, set
all temperature set points to zero, empty the hopper, and waste all of the extruded polymer that
has collected. Inform the lab technicians that you are leaving for the day. The technicians will then
take care of turning off the main power supply, the control panel, the computer, and the cooling
water.
3.3 Description of Injection Molding Apparatus
The injection molding apparatus consists of three major parts: the injection unit, the mold and
the clamping unit. Polymer pellets enter the injection unit through the hopper travel into the barrel
where they are heated to a molten state. The screw pushes the polymer through the injection nozzle and into the mold. Single or double gated dies can be used. After a specified time, the clamping unit opens the mold and a tensile bar is ejected from the machine.
10
3.4 Experimental Injection Molding Procedure
Contents
DC
PS
Injection molding is performed using a single or double gated die. Three parameters are varied
for each die: cycle time, injection pressure and barrel temperature. To determine the effects of
cycle time on tensile strength, the barrel temperature is set for example to 220 ˚C and the injection
pressure at 90 psig (for polystyrene). These setting depend on the type of polymer used, but the
temperature must of course be at least 20 - 30 ˚C above the melting temperature. Vary the cycle
time typically over a range of 30 - 60 seconds.
Reject the first five tensile bars to ensure that new settings have taken effect.
Collect the next ten tensile bars and select five for testing on the Instron.
3.5 References
PP
PB
GP
HX
MR
IX
TD
Rauwendaal, C., Polymer Extrusion, Hanser, Munich (1986).
Ram, A., and R.L. Laurence, Polymer Processing Notes, University of Massachusetts,
Amherst, MA (1996).
11
4
Packed Bed
4.1 Description of Apparatus
Contents
DC
PS
PP
PB
GP
HX
MR
IX
TD
The primary piece of equipment used in this experiment is a packed bed column standing perpendicular to the floor and made of clear Plexiglas. The packed portion of the column has an inner
diameter of 3.05 inches and a length of 56.5 inches. The column packing consists of glass spheres
0.131 (0.017 inches in diameter). Water is fed to the column by a closed-loop cycle. The water
enters the top of the column, passes through the packed bed, and then is collected in a water storage tank. The water collected in the storage tank is pumped through rotometers and then back to
the top of the column. The small rotometer is capable of measuring 0.00 to 0.25 gallons per
minute (GPM), while the large rotometer is used for larger desired water flow rates ranging from
0.0 to 3.0 GPM. The flow through each rotometer is controlled by a manual valve. A fresh water
supply is available when there is no water in the storage tank. The air is supplied to the system
from a compressor. The compressed air is fed to a water separator and air filter before flowing
through either of two air rotometers. The small air rotometer measures air flows from 0.0 to 3.2
standard cubic feet per minute (SCFPM). The large air rotometer measure flow rates in the range
of 0 to 250 SCFPM. The compressed air enters at the top of the column to flow co-currently with
the water
Three pressure transducers are mounted on the column. The top pressure transducer is
mounted above the packed portion of the column to transmit a signal indicating the entering pressure of fluid(s). The middle and bottom transducers are separated by a 5.0 inch axial distance.
These pressure transducers are used to obtain a pressure drop gradient in the packed bed column.
The transducers feed a signal to a nearby desktop computer. The computer receives and analyzes
these signals using a Basic program. The Basic program outputs the three pressure readings in
psig in psig to a PRN file. The pressure signals are typically received at a rate of 50 per second
over a 2 second period once the column reached a steady flow pattern.
If you are experiencing negative readings of pressure, the power supply on the post near the
methanation experiment, is not working.
4.2 Experimental Procedure
Gauge pressure data from three pressure transducers mounted along the axis of the column
was obtained by use of a computerized data acquisition program.
I.
Diagnostic Run
The column is stored under the atmospheric pressure of air, and is void of water. First the data
acquisition computer is turned on and a diagnostic run is made. No gas or liquid is flowing to the
column. The diagnostic run tests the pressure transducers to see if the transducers are reading
there correct zero values. The diagnostic run is also used to set the data acquisition parameters.
The user to selects the number of data points taken per second, and the length of time the data
is going to be collected over. Values of 50 points per second, and 5 sec are typically adequate in
trickling flow while 500 points per second is adequate for pulsing flow. The acquisition program
displays the pressure data in a graphical form as the data is acquired.
12
II.
Contents
Pump and Compressor Activation
The column is coupled to a centrifugal water pump that feeds the top of the column with
water. An air compressor is also coupled to the column and feeds the top of the column with pressurized air. Circuit breakers control the power to the compressor and water pump, and are located
on the wall by the computer station. The flow of air and water to the column are controlled by two
sets of control valves.
DC
The control valves are opened, to avoid any pressure build up in the pipes, and then the water
pump and the compressor are turned on, allowing air and water to flow into the column.
PS
PP
III.
Experimental Measurements
By varying the gas and liquid flow rates to the column a full range of operating conditions can
be explored. Both trickling and pulsing flow patterns are explored during our experiment. The gas
flow rate and the liquid flow rate were simultaneously adjusted to observe trickle and pulse flow.
GP
The liquid and gas rate are set as desired, then the flow pattern in the column is allowed to stabilize. The stability of the column is determined through the data acquisition program. The program plots the transducer pressure readings as a function of time. Stability for trickling flow is
achieved when the pressure is a constant value with time. Stability for pulsing flow occurs when
the pulses occur with some periodic behavior.
HX
When stability is achieved the past 5 seconds of data acquired are saved as a (*.prn) file on a
floppy disk.
PB
IX
Column Shut Down
At the end of each experimental session, the flow of water to the column is cut and the gas
valve is opened. This forces all of the water in the bed packing to exit the column, so that it is dry
for the next laboratory session.
TD
The computer program is deactivated and the computer is turned off. When the column is dry
the air compressor is turned off. The control valves are then closed completely to avoid back flow.
MR
IV.
4.3 References
Chu, C., “Transport in Trickle Beds: Fluid Flow, Dispersion, and Heat Transfer,” Ph.D. Thesis
University of Massachusetts-Amherst, (1988).
Ellman, M.J., N. Midoux, A. Laurent, and J.C. Charpentier, “A New Improved Pressure Drop
Correlation for Trickle-Bed Reactors,” Chem. Eng. Sci., 43, 2201 (1988).
Ergun, S., “Fluid Flow Through Packed Columns,” Chem. Eng. Pro., 48, 89 (1952).
Iliuta, I., F.C. Thyrion, and O. Muntean, "Hydrodynamic Characteristics of Two-Phase Flow
Through Fixed Beds: Air/Newtonian and Non-Newtonian Liquids," Chem. Eng. Sci., 51, 4987,
(1996).
Sai, P.S.T., and Y.B.G Varma, "Pressure Drop in Gas-Liquid Downflow Through Packed
Beds," AIChE J., 33, 2027 (1987).
Sato, Yuji, Tsutomu Hirose, "Flow Pattern and Pulsation Properties of Cocurrent Gas-Liquid
Downflow in Packed Beds," Journal of Chem. Eng. of Japan, 6, 315 (1973).
13
5
Gas Permeation
5.1 Description of Apparatus
Contents
DC
PS
PP
PB
GP
The gas permeation experimental station consists of a Permea Prism Separation System, gas
tanks, pressure gauges, filters, flow meters and oxygen analyzers.
A tank of compressed air feeds the system. Three valves with two pressure gauges on the tank
are used to regulate the air pressure entering the permeation system. The main tank valve is
opened and air flows into the manifold. A main pressure gauge measures the air pressure inside
the tank. There is also a pressure gauge on the manifold. The manifold pressure is regulated using
a needle valve. The final valve on the tank allows the air to flow to the system.
A ball valve after the feed tank controls the air flow to the system. The ball valve is open when
its handle is horizontal. The air passes through two Permea gas filters to remove moisture from the
air.
A pressure regulator sets the air pressure of the system after the filters. A pressure gauge down
stream of the regulator indicates the pressure entering the system. The air flows through the two
Permea polysulfone membrane separators operated in series or parallel, and counter-current or cocurrent configuration. The Prism Separator consists of a bundle of hollow 450 µm diameter
polysulfone fibers that run the length of the tube.
HX
MR
IX
TD
The non-permeate steam exits the top of the second column and flows through a needle valve,
which controls the flow rate of the stream. The stream then flows through a Top Trak flow meter
that determines the flow rate in standard liters per minute (SLPM). The flow meter works with
resistance temperature detector (rtd) coils. The gas molecules carry heat through the path. The
coils detect the temperature difference between two points and send out a signal. The molecules
carry the heat away so the output signal is linearly proportional to the gas flow.
Oxygen content in each stream is determined with Oxan oxygen analyzers. The oxygen analyzer works by using a oxygen selective membrane and a potassium hydroxide galvanic cell.
Within the galvanic cell oxygen electrons are carried across a salt bridge. When the electrons
cross a voltage is produced. The voltage produced is directly proportional to the percent of oxygen. The permeate stream flows through a similar setup, but with no needle valve to constrain the
flow. Both streams finally leave the system by the way of vents.
5.2 Experimental Procedure
I.
Calibration
A.
Plug in flow meters. Wait 15 minutes for the meters to warm up and then record the
zero reading.
B.
Turn on the oxygen sensors and select the ‘%’ setting. Disconnect the tubes at the
oxygen sensors. Calibrate the sensors using air by adjusting to 20.9% oxygen.
II.
Set Up Procedure
A.
Arrange the apparatus in series/parallel, co- or counter-current, and tube/shell side
feed configuration as required.
14
B.
C.
D.
E.
F.
Contents
DC
Open the feed tank valve.
Adjust the small tank valves to obtain a pressure (ex. 100 psig) on the tank’s pressure gauge higher than the maximum desired pressure in the separator.
Open the ball valve.
Set the desired inlet pressure (ex. 80 psig) on the pressure regulator.
While the system is initially approaching steady state, check for leaks at all the
connection points by using the provided soap solution. Perform a material balance
to ensure the system’s integrity.
III.
Experiments
A.
Set non-permeate flow rate.
B.
Allow the apparatus to reach steady state (allow about 5 minutes).
C.
Record permeate and non-permeate flow rates and oxygen compositions.
D.
Adjust non-permeate flow rate by discrete intervals while keeping the pressure
constant.
E.
Repeat steps B through D for a range of non-permeate flow rates.
Change the inlet pressure using the pressure regulator and repeat steps B through
D for a range of pressures.
IV.
Shut Down
A.
Close the main tank valves and allow the system pressure to reduce to atmospheric
pressure.
B.
Turn off the flow meters by unplugging the AC adapter.
C.
Turn of the oxygen analyzers by turning the dial to ‘off’.
PS
PP
PB
GP
HX
MR
IX
TD
5.3 References
Blaisdell, C.T., and K.Kammermeyer, “Counter-current and co-current gas separation,” Chemical Engineering Science, 28, 1249 (1973).
Davis, R.A., and O.C. Sandall, “A Membrane Gas Separation Experiment for the Undergraduate Laboratory,” Chemical Engineering Education, 10, 10 (1991).
Kesting, R.E., and A.K. Fritzche, Polymeric Gas Separation Membranes, Wiley, New York
(1993).
McHattie, J.S., W.S. Koros, and D.R. Paul, Polymer, 32, 2618 (1991).
Tillwick, D.C., “Measurement of Multicomponent Diffusion and Permeation of Gases in
Polymer Membranes,” PhD Thesis, Department of Chemical Engineering, University of Massachusetts (1988).
Walawender, W.P., and S.A. Stern, “Analysis of Membrane Separation Parameters. II:
Counter-Current and Cocurrent Flow in a Single Permeation Stage,” Sep. Sci., 7, 553 (1972).
15
6
Heat Exchanger
6.1 Description of Apparatus
Contents
DC
PS
PP
PB
The heat exchanger experimental station consists of two shell-and-tuber exchangers in
series.The first exchanger uses condensing steam to heat a stream of cool feed water. The tubeside contains the feed water and the shell-side is a steam manifold that condenses vapor to heat the
flow in the tubes. The outlet flow of the tube-side then enters a second exchanger. Cooling water
passes through the shell side.
Thermocouples are situated at 14 locations along the streams and temperatures are recorded
and stored by computer. Steam pressure, and liquid flow rates are set by adjusting three electronically actuated valves controlled by the computer. Valve settings can be converted to mass flow
rates using correlations.
6.2 Experimental Procedure
I.
Obtain the steam quality
A.
Crack the steam valve in the pipe connected to the main line
B.
Measure the temperature of the throttled steam
C.
Record the pressure in the main line
II.
Calibration of flows
A.
Feed water mass flow-rate
1.
Set voltage from the computer (4-8).
2.
Measure length of time to collect 100lbs. of water in 55 gallon barrel for
each voltage.
B.
Steam flow rate
1.
Set voltage from the computer (4-8).
2.
Measure the amount of condensate collected over a given time interval.
III.
Experimental Runs
A.
Set the steam and feed water flows
B.
Allow the steam heater to reach steady state
1.
Record the thermocouple temperatures until they are constant.
2.
Record the steam pressure in the main line and at the steam heater exit.
3.
Be sure the condensate level remains constant.
GP
HX
MR
IX
TD
6.3 Software Details
THE MENU:
1).
SELECT DATA SAVED
Look at 4) first to see how the data is stored. Take note of the
DDIN!(#) items that you wish to save. Go to 2) and execute.
2).
AUTO DATA SAVE This option sets up the data save. Name the file, time between samples and the sample period. e.g. Sample time between seconds is 3 seconds and the sample
16
period is 20 seconds. This means that every 3 seconds one set of data selected will be
saved. This will happen every three 3 seconds for 20 seconds and then stop. If you press
the 'S' key again the process will be repeated. The next set of data will be added to the bottom of the previous set. The set numbers will increase for each sample set. 12001, 12002
and 1200n.
Contents
3).
SET FLOWS The flow rate can be set for the Feed, Cooling Water or the Steam. The
range is 0 to 9.98. The minimum Feed flowrate is software controlled such that the heat
exchanger section for the steam will not be damaged.
PS
4).
DATA FORMAT
array.
PP
5).
RETRIEVE DATA The last data saved can be retrieved and examined with this option.
PB
6).
SET CONTROL CONDITIONS Somehow you need to have the coefficients for a PID
controller. These coefficients are entered. There are other options. Save the data. Graph the
data. A combination of both graph and save.
7).
GRAPH, OPEN LOOP You select some thermocouple and some stream. There is a provision to step change the stream that you choose. The open loop response can be observed
and the data saved.
8).
DIAGRAM The diagram shows the thermocouple locations by number.
9).
EXIT The program is terminated and none of the settings are saved.
DC
The order of the elements is given according to their position in the
GP
HX
MR
IX
6.4 References
TD
Bird, R.B., W. Stewart and E. Lightfoot, Transport Phenomena, Wiley, New York (1961).
Denn, M., Process Fluid Mechanics, Prentice-Hall, Englewood Cliffs, NJ (1980).
Incropera, F.P. and D.P. DeWitt, Fundamentals of Heat and Mass Transfer, 4th ed., Wiley,
New York (1996).
Kern, D., Process Heat Transfer, McGraw Hill, New York (1950).
Palen, J., Heat Exchanger Sourcebook, Hemispher, Washington (1986).
Rohsenow, W. and H. Choi, Heat, Mass and Momentum Transfer, Prentice-Hall, Englewood
Cliffs, NJ (1961).
17
7
Methanation Reaction
7.1 Description of Apparatus
Contents
DC
PS
PP
PB
GP
The apparatus for the methanation reaction consists of two tubular reactors, Reactor I and
Reactor II, containing 5 g and 1 g of alumina supported nickel catalyst, respectively. Input gases
H2 and CO (reactants) and N2 are stored in compress gas cylinders, which must be securely
chained at all times.
The input gases flow from the cylinders through flow meters and then into an eight-way valve.
The valve allows for control of reactor choice. After reaction takes place in the reactor, output
gases (products, unreacted reactant and N2 flow through a chiller, and then to a HORIBA Pir-2000
IR analyzer, which measures the composition.
Flow meters, pressure gauges and analyzer readouts are integrated with a data acquisition program, allowing for computerized data collection. Flow rates, temperature and pressure are computer-controlled. Calibration is done manually.
7.2 Experimental Procedure
I.
The IR analyzer and the reactor must be turned on 2 hours before the lab starts.
A.
At this time make sure that there is 400scc/mn of N2 going through the reactor.
1.
If not, press ‘enter’ ‘3’ ‘enter’ ‘1’ enter’ ‘400’ ‘enter’. This sets the desired
flow rate at 400 scc/min.
B.
The reactor temperatures can be set to T1 for reactor 1 and T2 for reactor 2 as follows.
1.
Press ‘enter’ ‘1’ enter’ ‘T1,T2’ ‘enter’.
2.
If you do not intend using one of the reactors, set the temperature of that
reactor to 0.
II.
Calibration of IR analyzer (after the station has been running for two hours)
A.
The analyzer should read zero CO concentration (only gas is N2).
1.
If not, unlock the ‘zero’ knob on the analyzer.
2.
Adjusted so as to zero the CO readout.
3.
Relock the “zero”knob.
B.
Open the CO and H2 valves.
C.
Set the CO to 400 scc/min.
D.
Set the N2 to zero
E.
The readout should say 2%.
1.
If it does not, the knob on the analyzer labeled calibrate should be unlocked
and turned until the readout registers 2.
2.
Relock the knob.
III.
Set operating conditions
A.
Go to screen 3 and edit the values
B.
Set the desired gas flow rates
C.
If necessary adjust the temperature.
HX
MR
IX
TD
18
IV.
Set up auto-save
A.
Type enter, 7, enter, W, enter. This tells the computer what to save.
B.
Type enter, 6, enter, and answer the questions. If a 3.5” disk is used, select drive B.
V.
Run the experiment
A.
Switch the knob on the IR analyzer from ‘calibrate’ to ‘run’.
B.
Move the large selector from horizontal to vertical.
C.
Hit ‘S’ to start auto-save.
VI.
Repeat III-V as needed.
Contents
DC
PS
7.3 References
PP
Felder, R.M., and Rousseau, R.W., Elementary Principles of Chemical Processes, 2nd ed.,
Wiley, New York (1986).
PB
Fogler, H.S., Elements of Chemical Reaction Engineering, 2nd. ed., Prentice-Hall, New Jersey
(1992).
GP
HX
MR
IX
TD
Mills, G.A., and Steffgen, F.W., “Catalytic Methanation”, Catal. Rev., 8, 159-210 (1973).
Yadav, R., and Rinker, R.G., “Steady State Methanation over a Ni/Al2O3 Catalyst,” Can. J.
Chem. Eng. 71, 202-207 (1993).
19
8
Ion Exchanger
8.1 Description of Apparatus
Contents
DC
PS
PP
PB
GP
HX
The apparatus is designed to investigate the batch sorption kinetics of cupric sulfate ion
exchange with Dowex resin of different mesh sizes. The reaction takes place in a 500 ml beaker
containing the desired solution of Dowex resin. Using a peristaltic pump, the solution is pumped
through a filter to the spectrophotometer, where it is analyzed in a flow-through cuvet. The solution is then recycled back to the reaction vessel.
The apparatus consists of the 500 ml Pyrex beaker (where the reaction takes place), plastic
tubing and fittings (to carry the solution from the beaker to the analyzer and back), the peristaltic
pump, the spectrophotometer, a cuvet and appropriate tubing.
The pump is a L/S Multi Channel Cartridge Pump Head with eight rollers and two cartridges.
The pump is constructed of a stainless steal rotor, and Rulon rollers with polysulfone ends. The
pump cannot be operated above 250 rpm. The filter is designed to connect to the end of the tubing,
is made of a plastic casing and contains a glass mesh disk. This disk allows the solution but not
the Dowex resin to pass through. From the pump, the solution flow through a Perkin-Elmer
Lambda 3 spectrophotometer. The spectrophotometer contains a Fisher flow-through cuvet to analyze the concentration. The cuvet has a 0.6 ml capacity encased in black opaque quartz SUPRASIL quartz window and has a 10 mm light path. Tubing is then used to recycle the analyzed
solution back to the reaction vessel. The beaker sits on a heater/stirrer to keep the solution wellmixed and at the desired temperature.
MR
8.2 Experimental Procedure
IX
I.
Calibrate spectrophotometer
A.
Prepare solutions for spectrophotometer calibration
1.
Prepare stock solution of aqueous cupric sulphate
a.
Weigh 11.03 g of CuSO4
b.
Use a graduated cylinder to measure 500 ml of distilled water in an
Erlenmeyer flask.
c.
Stir CuSO4 into distilled water until dissolved.
2.
Prepare four dilutions from stock solution.
B.
Procedure for calibrating spectrophotometer.
1.
Purge spectrophotometer with distilled water and set the absorbence to
zero.
2.
The wavelength is 720 nm.
3.
Run each solution through the spectrophotometer.
a.
Allow absorbence of each solution to reach equilibrium.
b.
Record equilibrium absorbence.
c.
Purge spectrophotometer with distilled water between solutions.
II.
Regenerate Dowex for experimental run.
A.
Weigh out 30 g Dowex (16-40 mesh or 200-400 mesh)
1.
Weigh out excess Dowex to account for mass loss during vessel transfer.
TD
20
B.
C.
D.
E.
F.
Contents
DC
III.
Experimental Run
A.
Prepare stock solution for experimental run
1.
Weigh out 6.54 g CuSO4 onto weighing paper.
2.
Use a graduated cylinder to measure out 500 ml of distilled water and place
in Erlenmeyer flask.
3.
Stir CuSO4 into solution until all solid is dissolved in solution.
B.
Purge spectrophotometer with stock solution.
C.
Measure out 150 ml of stock solution with graduated cylinder and place in reaction
beaker.
D.
Place Dowex in reaction beaker and run through spectrophotometer.
E.
Record absorbence every 30 s until solution reaches equilibrium.
F.
Purge spectrophotometer with stock solution.
IV.
Waste Clean-up
A.
Decant solution off top of beaker and place copper solution in waste jar.
B.
Place exhausted Dowex into beaker to be regenerated for future use.
PS
PP
PB
GP
HX
Place Dowex into a glass beaker and wash with 1 M HCl solution
Run Dowex/HCl solution through a funnel lined with filter paper into HCl waste
beaker.
Wash Dowex with distilled water and filter into HCl waste beaker.
Place HCl waste into waste disposal jar.
Remove regenerated Dowex and sore on dry filter paper.
MR
8.3 References
IX
TD
Anklam, M.R., Prud’homme, R.K., and Finlayson, B.A., “Ion Exchange Chromatography
Laboratory,” Chemical Engineering Education, vol, pp (1997).
Helfferich, F., Ion Exchange, McGraw-Hill, New York (1962).
Marinsky, J.A., Ion Exchange, Vol. 1 and Vol. 7, Marcel Dekker, New York (1966).
Reid, R.C., Prausnitz, J.M., and Sherwood, T.K., The Properties of Gases and Liquids,
McGraw-Hill, New York (1972).
Wankat, P.C., Rate Controlled Separations, Chapman and Hall, Glasgow, UK (1974).
21
9
Tray Dryer
9.1 Description of Apparatus
Contents
DC
PS
PP
PB
GP
The main part of this experimental station is an Armfield Tray Dryer. A fan at the entrance of
the dryer draws air into one side of the apparatus. Prior to entering the drying compartment, the
air is heated by a series of heating coils. The drying compartment can be accessed through a hatch
on the face of the dryer.
The controls on the front of the dryer consist of a fan speed control, temperature control and
main power switch.
In the drying compartment, a rack is suspended fro an electronic scale that is on top of the tray
dryer. The scale is used to monitor the mass of the sample, which is placed upon the rack.
Ten thermocouples are available to monitor temperature within the drying compartment. The
thermocouples are connected to an electronic switchboard and LED display.
In addition, an electronic anemometer is used to measure air stream velocity and a stopwatch
is used to monitor time elapsed during the experiment.
9.2 Experimental Procedure
HX
I.
MR
IX
Setup:
A.
B.
C.
D.
E.
F.
TD
Ensure that the power cord is plugged into the surge protector on the lab wall.
Switch on the main power to the tray dryer.
Set the temperature of the heating coils and the fan speed.
Fill the sample tray to the top of the lip with sand and saturate the sample with
water.
Place the sample on the tray in the drying compartment.
Place the thermocouples in the sample.
II.
Experiments:
A.
Allow the system to reach steady state as indicated by constant surface temperature.
B.
Start timing: every two minutes for thirty minutes take measurements of: (a) the
sample mass using the scale; (b) the air velocity using the anemometer; and (c) the
temperatures at all thermocouple points via the switchboard and the LED display.
C.
Change the air velocity and repeat steps A and B.
III.
Shutdown:
A.
Switch off heating coils and turn up fan speed to cool the sample.
Switch off the power to the tray dryer.
9.3 References
Foust, A.S., Principles of Unit Operations, Wiley, New York (1980).
22
Incropera, F.P. and D.P. DeWitt, Fundamentals of Heat and Mass Transfer, 4th ed., Wiley,
New York (1996).
Perry, R.H., and Green, D., Perry’s Chemical Engineer;s Handbook, McGraw-Hill, New York
(1984).
Contents
DC
PS
PP
PB
GP
HX
MR
IX
TD