I need to designate a symbol to note important comments concerning experiment operation

BRIEF DESCRIPTION OF EXPERIMENTS

Chemical Engineering Laboratory IIC&PE 626

Department of Chemical and Petroleum EngineeringUniversity of Kansas

Spring 2015List of Experiments

1. Multi-stage Distillation

2. Continuous Stirred Tank Experiment

3. Liquid Level Control System

4. Transient Heat Transfer

5. Vapor Liquid Equilibria Measurement

6. IPA Dehydration and Dehydrogenation Studies in a Tubular Reactor

1) Multi-stage DistillationA. BackgroundThe separation of mixtures into essentially pure components is of central importance in the manufacture of chemicals. Much of the equipment in the average chemical plant has the purpose of purifying raw materials, intermediates, and products by multiphase mass transfer operations. The laboratory utilizes a 21-stage Oldershaw distillation column that can be operated with continuous feed or with total reflux.

B. ObjectivesTo operate a laboratory scale, multi-stage distillation column and to reconcile its performance with expectations based on the operating variables. You will explore the operating envelope for the column and to integrate the use of CHEMCAD simulator with the operation of the column in order to evaluate the performance.

C. Experimental ApparatusThe laboratory utilizes a modified Oldershaw column. It has been equipped with appropriate sensors and control elements for semi-automatic operation. The column is controlled and data is acquired using the Camile system.

The reboiler counts as the 1st tray, there are 10 stages between the reboiler and feed, and another 10 stages above the feed for a total of 21 trays. The overall process is as follows: Feed is pumped at a specified power setting from the blue feed container through an electrical resistance preheater into the column at stage 11. At the top of the column, the overhead vapor is condensed in a cooling water condenser. The reflux ratio is set on the Camile, reflux drips directly back into the column, product drips to a volumetric cylinder for measurement. The reboiler is a 200 mL three necked flask heated by a 470 W electric mantle (note that most of the heat from the mantle is lost to the atmosphere). The bottoms product can be pumped out of the reboiler through a water-cooled condenser to the collection point. Liquid samples are analyzed using a refractometer.

Instrumentation for the column is interfaced with the CAMILE and consists of two pumps (feed and bottoms), bottoms pressure, several temperature measurements, feed and reboiler heaters, and reflux ratio.

D. OperationStarting OutThis initializes the Camile application.1. Press the button on the menu bar.2. Press and the blue button on the Camile. 3. If you ever have to stop running the column quickly, press and the red button on the Camile.

Calibrations1. Pump Calibrationa. Initially run the pump at 100% power for several minutes to ensure the pump is properly primed.b. Calibrate the feed and bottoms pumps by sending the flow to the appropriate volumetric cylinder. c. Place a well-labeled copy of your calibration spreadsheet in the Data folder for use by other groups. Be sure to list units and include plots. Have four equations listed: 1) feed power setting given the feed flow rate.2) Feed flow rate given the feed power setting.3) Bottoms power setting given the bottoms flow rate.4) Bottoms flow rate given the bottoms power setting.d. Check your calibrations by setting a pump output, then comparing your measured results with the calibration.e. Use the calibration for estimating flow rates and power settings - during normal operation you must measure the flow rate used.2. Temperature Calibrationa. Assume the temperature calibrations are correct.3. Index of refractiona. The first group should measure the index of refraction of various mixtures of methanol and IPA. 1) Measurements should be made by mass.2) Plots must be on a volume% basis. Ideal mixtures are linear only on a volume% basis.b. Place a well-labeled copy of your calibration spreadsheet in the Data folder for use by other groups. Be sure to list units and include plots. Have three equations listed:1) Volume% given the index of refraction.2) Mass% given the index of refraction.3) Mole% given the index of refraction.

Total Reflux OperationOnce the column is loaded with an appropriate amount of the feed stock, it should not be necessary to add more stock because all the overhead vapor gets refluxed.Realize that the relative volatility (VLE information) will govern the compositions of the distillate and bottoms. Note that during operation, the column will hold roughly 40 mL and the reboiler will hold roughly 200 mL. If you were to start with 220 mL of IPA and 20 mL of methanol, the reboiler would likely have no methanol all of which would be in the column.To the degree that you can depend on the temperatures measurements, you can use these with Txy data from Chemcad to determine the reboiler and distillate compositions. You can obtain better accuracy by analyzing samples using the refractometer, but BE WARNED, obtaining samples during steady-state, total reflux operation will remove a disproportionate amount of the volatile component and will change the steady state of the system.

Operating guidelines Total Reflux:1. Press the button on the menu bar.2. Press and the blue button on the Camile. This initializes the Camile application.3. If you ever have to stop running the column quickly, press and the red button on the Camile.4. Turn on the water for the condenser.5. Make sure that the lid on the feed tank is not closed tight to prevent a vacuum there, and allowing feed to flow to the column.6. Open the valve on the control column that states, vent while filling column.7. Load the column with the feed provided at 100% pump power.8. Close the vent while filling column valve. 9. Turn on the reboiler and set OP to a desired value (OP is in terms of percent of the maximum wattage of the mantle (i.e., 470 W). The maximum is about 50%. Note that Camile will shut down the equipment if the flask safety (reboiler heater) temperature exceeds 500 C. If this happens, fix the problem and use the buttons to reinitialize the apparatus.10. Set the reflux ratio by setting the on the Camile to 1 second, and for 1,000 seconds.11. Monitor the reboiler, feed-stage, and distillate temperatures during the approach to steady state. Use these temperatures to estimate compositions. Steady state is attained when the temperatures, and thus the compositions, are steady. Slowly rising temperatures may indicate a leak in the apparatus. Record the temperatures every 10 minutes in the laboratory notebook.12. Only upon reaching steady state, obtain refractometer data for the bottoms and distillate. Subtract the composition and volume removed from the total inventory in the column.13. Dispose of samples in the steel safety can provided. 14. If you need help, ask Jon for assistance.

Operating Guidelines Continuous Distillation:1. Press the button on the menu bar.2. Press and the blue button on the Camile. This initializes the Camile application.3. If you ever have to stop running the column quickly, press and the red button on the Camile.4. Turn on the water for the condenser.5. Make sure that the lid on the feed tank is not closed tight to prevent a vacuum there, and allowing feed to flow to the column.6. Open the valve on the control column that states, vent while filling column.7. Load the column with the feed provided at 100% pump power.8. Close the vent while filling column valve. 9. Turn off the feed pump.10. Turn on the reboiler and set OP to a desired value (OP is in terms of percent of the maximum wattage of the mantle (i.e., 470 W). The maximum is about 50%. Note that Camile will shut down the equipment if the flask safety (reboiler heater) temperature exceeds 500 C. If this happens, fix the problem and use the buttons to restart the experiment.11. Set the reflux ratio by setting the and to appropriate times ( plus should total roughly 20 seconds). a. If you used very long times for on and off, the column would cycle between two steady states. b. If you use too short of times, the uncertainty in the times would be sufficiently great as to make the true reflux ratio unknowable.12. Wait for the column to heat. When distillate starts to form, activate the feed pump for operation in the 2 10 ml/min range.13. Set the feed heater power to obtain the desired feed temperature.14. Keep track of the distillate flow rate. The bottoms flow rate should be set such that Feed Flow Distillate Flow = Bottoms Flow. Try to keep the liquid in the reboiler at a constant level. The bottoms flow may require minor adjustments several times during the experiment. It is preferable to adjust the bottoms flow instead of the feed flow because changing the bottoms flow does not change the steady state compositions in the column.15. Record all changes to the flow rates.16. Once the reboiler level appears to have stabilized (to some extent), monitor the column temperatures, and liquid composition while approaching steady state. Steady state is deemed to have been attained when the temperatures and refractometer readings are fairly steady. Slowly rising temperatures may indicate a leak in the apparatus.17. Record in the notebook temperatures and refractometer (composition) data during the approach to steady state. Record every data available in a data file and in the lab notebook when steady state is deemed to have been attained.18. If you need help, ask Jon for assistance.

How long does it take to reach steady state?If you took samples and recorded temperatures at one-minute intervals, you would find their values to be almost identical but you would not be at steady state. Use the residence time to guide you in how often to take measurements. The volume of the system is roughly 240 mL. If your flow is 6 mL/min, then the residence time is 240 mL/ (6 ml/min) = 40 minutes. Therefore, 20 - 40 minutes between measurements would be more appropriate. As a ballpark estimate, it will take 3-5 residence times to reach steady state (assuming you do nothing to upset the approach to steady state).

Other notes1.During start up, the user needs to monitor the system to ensure that it is behaving as expected. For example: Is the feed being heated to the set point temperature (Refer to the section control loop configurations)? Is the reboiler liquid level held at a reasonable level? This can be achieved by small manual changes in the bottoms flow rate. Is the heating mantle functioning flawlessly? Is the reflux temperature steady at the set point (Refer to the section control loop configurations)? Are the feed stage temperature and other temperatures along the column approaching expected or set values?2. When ready to change operating conditions, ask Jon if you require assistance. Some operating parameters that can be changed are feed compositions (the feed pump will have to be shut down for a few seconds to change the stock), reflux ratio, feed flow rate, and reboiler duty.3. When ready to shut down, buttons.

E. Dos and Donts1. DO NOT LET THE REBOILER RUN DRY. If the reboiler is close to running dry, turn off the heater and the bottoms pump.2. Do not leave the feed heater on for long periods when there is no feed flow (there is no feed flow during calibration and sampling).3. Pay attention to your operating parameters - determine what you expect to happen. Except for some safety items, there are no whistles that will alert you that you are running the apparatus incorrectly or that the apparatus has a "problem." You are the operating, you determine if there is a problem, then take appropriate action.

F. Safety1. Wear safety glasses at all times. Wear gloves when taking samples.2. In this experiment, methanol and isopropanol are used. Both substances are toxic and flammable. Review the MSDS sheets for these substances located in the CPE-626 folder on the world drive. If the chemicals get on you, use the eyewash or shower. In case of fire, use the fire extinguisher.3. Do not let the reboiler run dry! If the reboiler is close to running dry, turn off the heater and the bottoms pump.4. Do not leave the feed heater on for long periods when there is no feed flow (there is no feed flow during calibration and sampling).5. Turn on the hood.6. Guard against falls, burns, cuts, and other physical hazards.7. Think of safety in any action you take. If not certain, ask a faculty member before you act.8. The experiment is protected with ground fault breakers to help prevent electrocution. Care should always be taken when combining electricity with water.

methanol MSDS informationHealth Hazard Level 1 (on 4 point scale)Health Hazard Acute And Chronic: Harmful/fatal if ingested/absorbed through skin. Ingestion of 1 4 oz can cause irreversible injury to nervous system, blindness, death. Cant be made non-poisonous. Causes eye/respiratory system irritation. May cause skin irritation, defatting. Harmful if inhaled. May cause internal organ damage. Vapor inhalation/liquid penetration of skin can cause CNS depression (supple).

Signs/Symptoms Of Overexp: Inhalation: Nausea, drow, vertigo, FTG, convulsions, unconsciousness, death.Eye: Burning sensation, tearing, redness, swelling. Conjunctivitis, corneal burns.Ingestion: Blindness, systemic acidosis, symptoms may be delayed. Medical condition aggravated by Exposure: personnel with pre-existing CNS disease, skin disorders, impaired liver or kidney function, or chronic respiratory diseases should avoid exposure.

Emergency/First Aid Proc: Inhalation: Immediately remove to fresh air. Keep victim quiet. Give air/oxygen and/or CPR. Eye: Immediately flush with lots of water for at least 15 minutes, opening eyelids.Skin: Immediately remove contaminated clothing. Wash area well with soap/water.Ingestion: Symptoms may be delayed. Life threatening. Conscious drink 2 glasses of water. Induce vomiting. Follow emesis with 2 teaspoons of baking soda in water. Ethanol therapy may be indicated. In all cases see doctor immediately.

Isopropanol MSDS informationHealth Hazard Level 1 (on 4 point scale)Target Organs: Kidneys, central nervous system.Potential health affectsEye: Produces irritation, characterized by a burning sensation, redness, tearing, inflammation, and possible corneal injury. Skin: May cause skin sensitization, an allergic reaction, which becomes evident upon re-exposure to this material. Prolonged and/or repeated contact may cause defatting of the skin and dermatitis. May cause irritation with pain and stinging, especially if the skin is abraded. Ingestion: May cause gastrointestinal irritation with nausea, vomiting and diarrhea. May cause kidney damage. May cause central nervous system depression, characterized by excitement, followed by headache, dizziness, drowsiness, and nausea. Advanced stages may cause collapse, unconsciousness, coma and possible death due to respiratory failure. Inhalation: Inhalation of high concentrations may cause central nervous system effects characterized by headache, dizziness, unconsciousness and coma. Inhalation of vapor may cause respiratory tract irritation. May cause narcotic effects. Chronic: Prolonged or repeated skin contact may cause defatting and dermatitis. May cause allergic skin reaction in some individuals. First AidEyes: Immediately flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower lids. Get medical aid immediately. Skin: Get medical aid if irritation develops or persists. Flush skin with plenty of soap and water. Ingestion: If victim is conscious and alert, give 2-4 cupfuls of milk or water. Never give anything by mouth to an unconscious person. Get medical aid immediately. Induce vomiting by giving one teaspoon of Syrup of Ipecac. Inhalation: Get medical aid immediately. Remove from exposure to fresh air immediately. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Notes to Physician: Urine acetone test may be helpful in diagnosis. Antidote: None reported

2) Continuous Stirred Tank Experiment

A. BackgroundStirred tanks are used in a variety of situations in chemical plants. In some cases, they may be used to simply mix several streams or ingredients either in a continuous process or a batch process. In other cases, the tank may act as a chemical reactor, again in either continuous or batch processes. Different approaches may be taken for analyzing the transient characteristics of these tanks depending on the tanks ultimate use. For instance, if the tank is used to mix streams to form an outlet stream with specified concentration, we may be interested in the system response as viewed from a process control standpoint (i.e., does this act as a first order or second order system? Do we need to include dead time?). However, if the tank is to be used as a reactor, we may wish to determine how closely the tank behaves like a perfectly mixed continuous stirred tank (CST). If the tank is poorly described by an ideal mixing assumption, we may wish to model the system as a series of CSTs or other types of reactor models.

B. ObjectiveTo characterize the residence time distribution in a stirred tank.

C. Experimental ApparatusThe apparatus consists of a 40 liter tank equipped with a mechanical stirrer and baffles. The inlet to the stirred tank runs through a flow meter, which is interfaced with the Camile. The outlet line from the tank is constructed so that the amount of water in the tank remains roughly constant. A salt tracer is injected into the tank. The conductivities of the influent and effluent are monitored at regular time intervals using probes interfaced with the Camile. The frequency of the mechanical stirrer is also recorded using the Camile. There is also a pressure transducer used as a level indicator and a thermocouple to measure tank temperature.

D. OperationCalibration1. Calibrate the flow meter by removing the hose leading to the tank, then using the bucket/stopwatch method.2. The pressure transducer indicating water volume (mass) has been calibrated for you. Verify the calibration by closing the outlet and adding a known mass of water to the tank.a. The uncertainty of the mass with the stirrer off is 0.25 kg.b. Activating the stirrer can cause the indicated mass to increase from 0 to 0.30 kg above the correct value.3. You will not calibrate the conductivity probe per se, however, you need to determine the range of salt concentrations for which the conductivity is linear. Remove the inlet conductivity probe and use it to measure conductivities of known concentrations of salt water. Thereafter, use salt concentrations in the tank that are linear with conductivity. The maximum is not known at this time, but is less than 6 g salt/L. Announce the maximum value for linearity in the laboratory notebook - make sure this is well labeled for viewing by future groups.

Two main types of experiments will be used: Step Change, and Pulse Operating Guidelines: Step Change1. Fill the tank with tap water.2. Turn off the incoming water, close the outlet, then add an amount of concentrated salt solution to the tank. 3. Activate the mechanical stirrer. 4. After the solution is well mixed (about two minutes), quickly open then close the outlet. This permits the concentration in the outlet (where the conductivity probe is located) to equal the concentration inside the tank.5. Activate the logging function of Camile. Logging should be once every 20 - 30 s. Make the baseline is logged for at least two minutes.6. Both the inlet and outlet valves are opened. The conductivity of the outlet stream is then monitored in time. You must come up with a way to ensure that during this starting of the flow, the tank level varies as little as possible.

Operating Guidelines: Pulse1. Fill the CST with tap water initially and maintain a steady flow of water through the tank by opening both the inlet and outlet valves. 2. Activate the mechanical stirrer.3. Activate the logging function of Camile (once every second). Obtain a two minute baseline before adding the salt solution. One minute following the introduction of the salt solution, logging may be decreased to once every 20 - 30 s. 4. Once a steady flow and steady tank level have been achieved, an amount of salt water is injected into the inlet line of the tank from the attached reservoir. Note that the height of the injection pipe may be raised or lowered.

E. AnalysisThere are numerous ways to analyze mixing. The following is but one method.

(2.1)

(2.2)

(2.3)

where:C = salt concentration (g/l) = constant*conductivityC0= salt concentration that would be achieved at time zero if mixing were ideal (g/l)F = flow rate (l/min)t = time (min)M = mass of salt introduced to tank (g)V = tank volume (l)

C/C0tF/V

III

ln C/C0

Slope =

extrapolate

t F/V

t F/VT F/V

Back calculated from extrapolationIII

C/C0

Figure 2.1: Procedure for integrating elution profileI: plot of concentration in dimensionless timeII: plot of log concentration in dimensionless time Extrapolate for longer periods of timeIII: plot of concentration using original data plus extrapolated profileIf your value for F/V is correct, then integrating equation 3 should yield a value of 1. If your value is not 1, then your value for F/V is incorrect. See Jon if there is a problem.You are now ready to analyze your experimental data. The experimental response curve (for example Figure 1-II) can be described by

(2.4)

Case F/V

Perfect mixing10

plug flow>1>0

dead space>10

bypassing