Compiled Lab Problem Statements
Compiled Lab Problem Statements
Introduction
Catalytic Methanation
Ethyl Acetate Kinetics
Bioreactor Kinetics
Phenolphthalein Kinetics-A
Phenolphthalein Kinetics-B
Continuous Distillation
Batch Distillation
Pulsed-plate Column
Freeze-Dryer
Wetted-wall Column
Environmental Protection (Instrumentation and LabVIEW)
Fluidization
Introduction
The following list of problem statements has been developed for each of the experiments in ChE 477. The represent a fairly realistic sampling of assignments that could arise in either corporate or small business settings.
Catalytic Methanation
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Catalytic Hydrogenation of CO2 to Methane
The company is considering using the waste CO2 and H2 streams from the plant to produce methane. In order to design a reactor to do this, basic kinetic data for the reaction of CO2 and H2 over nickel catalysts are needed.
A laboratory reactor designed to measure these data has been recently renovated in the UO lab. It is your assignment to obtain kinetic data (reaction orders and activation energies) for one nickel catalyst (Harshaw G-87). Limit your study to compositions that are stoichiometric or excess in hydrogen and contain from 1.0 to 4.0% CO2. The temperature range of your study will probably be around 250 to 330 0C, but you only need to determine the concentration dependencies at one temperature.
I would also like you to determine at what temperature pore diffusion limitations begin to come into play, if at all. Also, please comment on the catalyst's stability with time, both during a run and over long periods of time.
Design problem: How much methane can be produced in an isothermal CSTR containing one ton of the G-87 catalyst if you operate at 270 0C and 1 atm with a feed of 1.0 x 104 SLM containing 4.0% CO2 and 20% H2?
Hints:
1)Be sure to learn how to use the gas chromatograph by reading the manual and discussing it with Mr. M. Beliveau.
2)You will probably want to keep CO2 conversion levels below 20% in order to use the assumption of differential reactor performance. Staying in this conversion range can be done by finding the right temperature and flowrate ranges in which to operate.
3)You will want to refer to the work of Weatherbee and Bartholomew [J. Catalysis 77, 460 (1982)] with regard to the previously measured kinetics for this reaction.
Ethyl Acetate Kinetics
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Ethyl Acetate Kinetics
In our design study for the new reactor for the Ethyl-Acetate/Sodium Hydroxide Plant, we have discovered that our supplies of solid sodium hydroxide contains the impurity KCl. We need you to determine how up to 4 weight percent of this impurity in the feed stream affects the kinetics of the reaction. Please determine the kinetic parameters (rate constant, reaction order, activation energy) for the reaction with and without this impurity.
We already have a stirred-tank reactor (volume = 80 cubic meters) on hand which was salvaged from the old polymers plant. Would you please determine if this tank would be an adequate reactor to achieve a 96 percent conversion of our ethyl-acetate under the following conditions:
Reaction temperature = 28 degrees centigrade
Et Ac feed-stream flowrate = 5300 moles Et Ac per day
Et Ac feed-stream concentration = 0.023 molar Et Ac
NaOH feed-stream flowrate = 7950 moles NaOH per day
NaOH feed-stream concentration = 0.046 M NaOH
Please comment on whether we should consider methods of removing the impurities from the sodium hydroxide stream.
Useful Reference:
Laidler, K.J. and Chen, D., Trans. Far. Soc., 54, 1026, (1958).
Bioreactor Kinetics
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Bioreactor Kinetics
Our company has been asked to test a certain yeast strain (saccharomyces cerevisiae) for general use in an organic ethanol production facility. Ethanol can be produced by fermentation of glucose by yeast when in an anaerobic environment . A small amount of yeast can be cultivated in a reactor to quickly increase the cell mass under aerobic conditions. The increased cell mass can then be sent to a second reactor for ethanol production.
Use the company's bioreactor to test the yeast strain in aerobic conditions. Please determine the following parameters for this yeast: gas-liquid mass transfer coefficient, specific cell growth rate, specific cell respiration rate, and specific glucose uptake rate. The experiment works much better if fresh yeast is used.
There are several references in the company’s library that might be beneficial (see below) and a copy of a Cornell experiment (first reference) is attached.
References:
Shuler, M.L., N. Mufti, M. Donaldson, and R. Taticek, "A Bioreactor Experiment for the Senior Laboratory," Chemical Engineering Education, Winter 1994.
Wang, D.I.C., "Fermentation and Enzyme Technology".
Shuler, M.L., "Bioprocess Engineering" in Encyclopedia of Physical Science and Technology, Vol. 2
Bailey, J.E., "Biochemical Engineering Fundamentals"
Phenolphthalein Kinetics-A
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Phenolphthalein Kinetics-A
The reaction of phenolphthalein with a base solution follows the 2 reaction sequence given below.
Reaction 1
Reaction 2
We are considering using phenolphthalein as an indicator to determine the residence time of several large CSTR reactors in the pilot plant (see Fogler chapters 13-14). Please determine the kinetic parameters with respect to phenolphthalein associated with the fading of phenolphthalein in sodium hydroxide solutions (order, k, and Ea). Please use a temperature range of 50 - 180 oF. What is the heat of reaction as a function of temperature within a 95% confidence level? What are the corresponding equilibrium constant values.
How do you propose to do an analysis, i.e., what concentrations will you measure in order to obtain kinetic information? What do you know about the kinetics of the above reaction sequence that allows you to use this approach?
Hint: Absorbence, which is proportional to concentration is equal to the log (base 10) of 1/Transmittance.
References:
Andres and Hile, Chem. Eng. Education, Winter 1976, pp. 18-22.
Barnes, M.O. and LaMer, V.K., J. Amer. Chem. Soc., 64, 2312, (1942).
Chen, P.T.Y. and Laidler, K.J., Canad. J. Chem., 37, 599, (1959).
Phenolphthalein Kinetics-B
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Phenolphthalein Kinetics-B
The reaction of phenolphthalein with a base solution follows the 2 reaction sequence given below.
Reaction 1
Reaction 2
We are considering using phenolphthalein as an indicator to determine the residence time of several large CSTR reactors in the pilot plant. In order to do this, we need to understand the fundamental phenomenon that govern the above reaction sequence at room temperature.
Please answer the following questions:
1.How do you propose to do an analysis, i.e., what concentrations will you measure in order to obtain kinetic information? What do you know about the kinetics of the above reaction sequence that allows you to use this approach?
1.Determine the forward and reverse equilibrium constants at room temperature using a 0.1 N hydroxide concentration. What happens when the hydroxide concentration is doubled? What does this suggest about the order of the reaction with respect to both phenolphthalein and hydroxide?
1.What is the effect of ionic strength on the reaction kinetics? Propose a set of experiments to investigate this effect and carry them out to determine the effect.
Hint: Absorbence, which is proportional to concentration is equal to the log (base 10) of 1/Transmittance.
References:
Andres and Hile, Chem. Eng. Education, Winter 1976, pp. 18-22.
Barnes, M.O. and LaMer, V.K., J. Amer. Chem. Soc., 64, 2312, (1942).
Chen, P.T.Y. and Laidler, K.J., Canad. J. Chem., 37, 599, (1959).
Continuous Distillation
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Continuous Distillation
It has recently come to our attention that the ATF (Bureau of Alcohol, Tobacco, and Firearms) has confiscated a large quantity of a 75/25 wt % mixture of ethanol and methanol. They have traditionally burned such confiscated mixtures, but are now having a problem because the EPA has decided that burning it at the present site is not environmentally safe. The ATF is willing to give us this mixture for the price of shipping it. However, we cannot sell this until we separate it into two streams. The maximum allowable impurity of the ethanol can only be 0.5 wt % methanol and the maximum allowable impurity of the methanol stream can only be 0.3 wt % ethanol in order to sell it. Design a tower using sieve trays that can process 8,000 kg/hr of the above feed. Use the Oldershaw column (continuous column) in the unit operations laboratory to find the EOV. Using procedures found on page 303 of Seader and Henley or in King page 619, find the EMV. Find the number of actual stages and reflux ratio needed for the separation. Use the correlations in Chapter 6 of Seader and Henley to find the correct diameter of the desired column, as well as the downcomer area and weir height. Use a tray spacing of two feet.
It is extremely important that we avoid flooding, weeping, or serious entrainment. The first thing you should do is determine when these conditions exist in the Oldershaw column by using various reflux ratios, boilup ratios, and feed rates. Determine the feed rates and reflux ratios that yield weeping conditions and plot them up in a parametric plot. Describe what you physically observe when flooding and serious entrainment occur in the Oldershaw column as well as the conditions under which they occur. Take digital pictures of these conditions and include then in your report.
Hints: Be wary of flow meters. Be sure they are working correctly and are calibrated before trusting them.
Suggested References:
Faust, A.S., Principles of Unit Operations, John Wiley and Sons, New York, NY (1962)
Henley, E.J., and Seader, J.D., Equilibrium Stage Operations in Chemical Engineering, John Wiley and Sons, New York, NY (1981)
King, C.J., Separation Processes, 2nd Edition, McGraw-Hill Book Company, New York, NY (1980)
Thompson, R.E., McCabe-Thiele Methods - Simple Columns, p.p. 27-34 in AIChE Modular Instruction Series B: Stagewise and Mass Transfer Operations, Vol 1: Binary Distillation, Ed. by E.J. Henley, American Institute of Chemical Engineers, New York, NY (1980)
Treybal, Robert E., Mass-Transfer Operations, 3rd Edition, p.p. 202-211, McGraw-Hill Book Company, New York, NY (1980)
Batch Distillation
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Batch Distillation
The specialty chemical division has begun production of deuterated methanol (CH3OD) at 4 kg/day. Unfortunately the final step in the synthesis requires the addition of one volume ethanol for every volume CH3OD produced. Can we use the small batch distillation column to recover the CH3OD in better than 97 wt% purity? If so, how much can be recovered at this concentration? Do you have any recommended modifications to the column to improve its operation. Be creative and consider all options. This CH3OD is worth $700/kg at 99% purity and only $200/kg at 97% purity. The specialty chemical division indicated that they could use recycled EtOH containing some residual CH3OD in the final step of their synthesis, i.e., you may want to consider recycling the bottoms so that none of the CH3OD is lost. Does the theoretical equation for batch distillation apply to this column?
Suggested References:
Seader, J.D. and E.J. Henley, Separation Process Principles. 1998, New York: John Wiley & Sons, Inc. 886.
McCabe, Smith and Harriott, Unit Operationsof Chemical Engineering, McGraw Hill, New York, (1985).
King, C.J., Separation Processes, 2nd Edition, McGraw-Hill Book Company, New York, NY (1980)
Perry, R.H., and Chilton, C.H., Chemical Engineers' Handbook, 5th Edition, McGraw-Hill Book Company, New York, NY (1973)
Treybal, Robert E., Mass-Transfer Operations, 3rd Edition, p.p. 202-211, McGraw-Hill Book Company, New York, NY (1980)
Pulsed-plate Column
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Pulsed-plate Column
Our company has recently received a computer controlled pulsed-plate column. We intend to use it to purify Stoddard solvent which has been contaminated with small amounts, 2 - 3 wt%, of propionic acid. Only sketchy operating instructions have been included. We need to evaluate the usefulness of the column in extracting propionic acid from the solvent using water. We also need to learn the operating procedures and the useful range of operating conditions. Please perform some experiments on this piece of equipment which will help us determine its proper use in the future. It is important that we find the equilibrium distribution of propionic acid in the water and Stoddard solvent phases (in wt%).
The variables you should vary include pulse frequency, pulse amplitude, and water flow rate. Fix the organic flow rate at 35% of pump capacity.
Hint from JLOscarson (5/99): From previous experience with pulsed-plate columns, it has been found that entrainment is a problem. Before determining the concentrations of the solutions, let the organic and the aqueous phases separate and then analyze each phase. Also, determine the amount of entrainment in the overhead and the bottoms for each of the runs.
Do trends you observe in HTU agree with HTU values you can estimate from packed column correlations found in the literature?
Reference
White, S. C., Ph. D. Dissertation, Dynamic Matrix Control of a Pulsed-Plate Liquid-Liquid Extraction Column Using a Low-Level Controller, Brigham Young University, Provo, Utah (1994).
see Dr. Hecker for other literature.
Freeze-Dryer
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Freeze-Dryer
The company is considering developing freeze-dried orange juice as a new product and needs design information for the process. A small-scale freeze dryer is available for this purpose. We are also interested in developing reasonable surrogates with which to do process optimization to avoid the natural variations in orange juice itself. Please use the existing apparatus to develop the following data:
- Drying rate of water
- Drying rate of a 10% mass solution of fructose in water
- Drying rate of fresh orange juice.
Determine differences and similarities in the rates of drying and identify the major sources of such variations. Determine from the data and appropriate analysis what major factors control the rate of drying. Discuss the merits of a standardized mixture as a surrogate with which to optimize a new process.
Wetted-wall Column
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Wetted-wall Column
A small plant is being designed for a remote desert location. Within the plant, a stream of 10 gpm of chemically treated water must be cooled from 100°C to 50°C before entering another process. A local engineer has suggested that some surplus 1 inch and 1 3/8 inch wetted wall columns already at the plant site could be used to evaporatively cool the water. Another engineer has expressed concern that too much of the feed water stream (valued at $0.06 per gallon) would be lost in the process.
Please determine the mass transfer coefficient for the water into air over as wide a range of air velocities as possible, and compare with values reported in the literature. Based on your results, design a system that provides optimal cooling from the columns, and then estimate the percent of mass lost in the process and the cost of the lost water. Should we go with the wetted wall cooling process? If not what do you suggest?
See Transport Phenomena by Bird, Stewart, and Lightfoot
Environmental Protection (Instrumentation and LabVIEW)
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Environmental Protection (Instrumentation and LabVIEW)
The operating permit for our plant requires that our liquid effluent have a pH that varies by less than +/- 0.5 from local tap water and a temperature lower than 35 ºC based on a rolling one-minute average. Large financial penalties and extensive regulatory review are imposed if we do not meet these specifications. Your assignment is to develop a computer-based logging and measurement system with the following capabilities.
- Monitor the temperature and pH of the stream based on 5 second averages to insure compliance with the specification.
- Turn off the pump to the system if the flow exceeds the specified limits.
If time and resources allow, incorporate the following features into the design.
- Divert streams that violate the pH specification to a holding tank for later treatment. The holding tank should have a capacity for three minutes of flow.
- Divert streams that violate the temperature requirement to a holding tank where the stream will cool. Monitor the temperature of the diverted stream and reintroduce it into the effluent when sufficiently cool. The holding tank should have a capacity for three minutes of flow.
- Provide holding tank level alarms for both tanks and an effluent shutoff to prevent upset conditions from being discharged.
- Record rolling 1-minute average effluent properties.
Demonstrate the capability of the system to provide documented compliance with these requirements. That is, demonstrate appropriate system responses when pH or temperature limits are exceeded, when tank levels are high, and when shutoff signals are received.
A computer, a variety of sensors and valves, and appropriate software are provided for you. You will need to familiarize yourself with the computer-based signal acquisition and control software (LabVIEW – a very common commercial package for such projects), write an appropriate acquisition and control program, design, build and wire the hardware, interface the hardware and your computer program, and test the system.
Fluidization
8 January 2001
TO: Engineering Development Branch
FROM: Engineering Division
SUBJECT: Fluidization
The company needs to evaluate heat transfer in a fluid bed but has not equipment with which to do so. Your assignment is to construct a small-scale fluid bed that is able to simulate the essential characteristics of a commercial facility. Appropriate instrumentation and data acquisition/process control tools are also required. As a minimum, the following characteristics should be monitored:
- Gas flowrate through the bed
- Bed pressure drop
- Bed temperature distribution
- Heat flux to a cylinder placed in the bed and in air without fluidization particles
- Minimum fluidization velocity
- Heat exchange rate between air and particles
Your group is asked to design and construct the system and verify its usefulness.