Lab Instruction Che 246

8/9/2019 Lab Instruction Che 246

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FACULTY OF CHEMCIAL ENGINEERING UITM PASIR GUDANG

CHE 246 SEPARATION

PROCESSLAB INSTRUCTION

A. DISTILLATION COLUMN

B. GAS ABSORPTION


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SECTION 1: DISTILLATION COLUMN

NOTES OF GUIDANCE

Lab workActivity 1Continuous distillation at constant reflux.

Learning outcome1. Describe the operation of continuous distillation column.

2. Draw the PFD and P&ID of continuous distillation column.

3. Perform mass balance calculations on continuous distillation column.

4. Demonstrate effective team role and responsibility in the task execution.

ScenarioYou have just joined as an assistant engineer in Maju Jaya Pte Ltd which produces methanol. Theprocess engineer asks you and your team to operate a continuous distillation column at constant refluxratio. In addition, you have to carry out mass balance calculations on the distillation column andexamine the effects of reflux ratio and feed conditions on the number of theoretical plates in acontinuous distillation. Refer to information of distillation column.

ObjectivesThis activity requires you to operate a continuous distillation column at constant reflux, carry out massbalance calculations on the distillation column and examine the effects of reflux ratio and feedconditions on the number of theoretical plates in a continuous distillation.

The process engineer has provided you the following information;1. Schematic diagram of the distillation unit (Appendix: Figure 1)

2. X-Y Equilibrium Diagram for Methanol-Water System at 1 atm (Appendix: Figure 2)

Upon completion of the test, write a technical memo of the result obtained. The memo should include(but not limited to) the following

a) Clearly states test parameters

b) Test results

c) Evaluation of results

Pre-Experiment Assessment

A. Planning/Preparation (10 marks)

All team members arrive at the process operation site to discuss on the plan to examine the effects ofreflux ratio and feed conditions on the number of theoretical plates in a continuous distillation. Pleaserecord as the team members in the process operation site by video.

TaskI. Distributed works and introduces the team.

II. Familiarize with the distillation column by determining the line tracing of this system. Withreference to Figure 1, identify the key components of the distillation column.


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2. Understand how the distillation column works

a. The function of column, reflux drum, condenser and reboiler in distillation column.

b. Explain distillation principles; volatility prior to boiling point of the component

3. Decide on the test parameters

a. Reflux ratio and feed temperature

B. Allocation of Roles and Teamwork (10 marks)

1. Analyze the tasks to be performed and divide among your team who to perform the tasks.

No Task description Member

1 Introduction and theory

2 Collecting data

3 Analyze the result4 Safety awareness

5 (Add if necessary)

2. Explain the basis for your groups task allocation.

3. Explain how will failure in performing the role of one of the above mentioned task affect the teamperformance.

C. Hazard Identification and Safety Precaution (10 marks)

Before starting the operation of the distillation column, it is important to identify hazards and precautionsto be taken to ensure safety of operators.

Study the process equipment, utilities involved, process materials and procedures carefully to identifypotential hazards.1. What are the hazards associated with ethanol?

2. What are the possible hazards if ethanol-water mixture is exchange to benzene-toluene mixture inthe process operation?

3. What safety precautions would you take in relation to the above mentioned hazards?

D. Performance Test Procedure

1. Perform the general start-up procedures.

a) Ensure all valves are closed.

b) Turn on the power for the control panel.

c) Prepare a 3040 L mixture containing ethanol and filtered water at the desired composition.Charge the unit as follows:i. Open the charge port cap at the reboiler B1, and fill the reboiler up to the level of the internaloverflow height.

ii. Pour the remaining ethanol-water mixture into the feed vessel B2 through the feed charge port.d) Set the reflux divider KFS-101 to total reflux. This is to prevent any distillate from escaping whenstarting up the distillation column.


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e) Let the cooling water flow into the condenser W2 and product coolers W3 & W4 by opening valvesV13, V14 and V15.

f) Ensure that the tip of the level switch is located below the reboiler equator, which is at the liquidinlet from the cartridge heaters.

g) Switch on the cartridge heaters at W1. Allow the liquid in the reboiler to boil.h) Observe the vapor rising from the boiling liquid into the distillation column. As the vapor reachesthe condenser, it will condense and flow back into the column as liquid. Mass transfer will take placebetween this liquid and vapor phase in the column.

i) Check that the condenser has sufficient cooling water flow to minimize escape of vapor into thevent.

j) Let the distillation column run until a stable condition is observed. The stable condition is reachedwhen all temperature indicators on the column give a constant reading with an allowable fluctuationof 0.2C.

2. Set the reflux divider to automatic reflux with a reflux ratio of 1 (e.g. 2 sec reflux and 2 sec distillate)

at the reflux divider controller (KFS-101).

4. Switch on the feed pump P1 and adjust the pump stroke and frequency in order to obtain a flow ratebetween 5 to 10 L/hr (80 to 100% stroke at 120 to 150 strokes/minute).

5. Switch on the bottom pump P2 and adjust the bottom flow rate (V7) to desired value by taking intoaccount of the feed and distillate flow rate to maintain the level in the reboiler.

6. Once the distillation column has reached stable condition, record the trays, top and bottomtemperature.

7. Collect samples from the trays, distillate and bottom product. Samples can be taken from the

distillate and the bottom product for analysis:

a. Distillate sampling:i) Drain any remaining liquid in the sampling valve V11.ii) Place a vial below valve V11.iii) Set the reflux divider to total distillate offtake for a few seconds.iv) Open valve V11, collect enough sample and close the valve.v) Switch the reflux divider back to the original setting.

b. Bottom sampling:i) Drain any stagnated liquid above valve V8.ii) Place a vial below valve V8.

iii) Open valve V8, collect enough sample and close the valve. Be careful of the hot liquid whilecollecting a sample.iv) Cool the sample by immersing the vial in cold water.Note: Always re-cap the vials quickly after collecting samples to avoid excessive evaporation ofethanol before analysis.

8. Measure the refractive index for all samples and determine their compositions.Measure the refractive index of a sample and determine its composition from the calibration curve. Ifthe composition value is difficult to be determined accurately due to the calibration curves flat slope,dilute the sample so that a more accurate reading can be obtained. Perform the dilution as follows:

a. Place a 10 mL measuring cylinder on a weighing scale (accurate to 0.01 g) and zero the scale.


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b. Using a dropper, transfer 1 to 2 g of sample into the measuring cylinder. Record the sampleweight.c. Add water into the measuring cylinder to dilute the sample. Obtain a total solution weight in therange of 5 to 10 g. Record the solution weight.

d. Ensure that the diluted solution is well mixed before measuring its refractive index (RI).e. Obtain the diluted solution's composition from the calibration curve.f. Calculate the actual sample's composition.g. Use the sample table in Appendix C for data recording and calculation

9. Measure the bottom and distillate product flow rates at FI-302 and FI-303.10. Repeat the experiment (steps 3 to 8) with a different value of reflux ratio.11. Repeat the experiment (steps 4 to 8) with a different feed temperature by switching on the feed

preheater W5 and setting the feed temperature set point to 50C.

E. Post-Experiment Assessment (10 marks)

You have completed the task. Carry out a team review on the test result.1. Draw the PFD and P&ID of distillation column.

2. Write down the overall and component material balance equations for the distillation column.

3. Identify at least 2 observations (flaws or good features) made during the operation on the basicfunction of the distillation column.

REPORT ASSESSMENT (10 MARKS)F. Technical Memo

Draft a technical memo addressed to the Process Engineer on your te ams evaluation of the distillationunit. Your memo can take the technical format report.

Enclosed: Test results of distillation column at constant reflux ratio and key findingsThe enclosed Test results of distillation column at constant reflux ratio and key findings of the memoshould include detailed test results and key findings as follows:a) Test results. State the test parameters and provide proper tabulation with units clearly stated.

b) Evaluation of results.

For the section on Evaluationof results, you may use the following guiding questions to discuss theresults:By using X-Y equilibrium diagram for ethanol-water system1. Mark the trays, top and bottom compositions on the diagram

2. Determine the number of theoretical plates in the distillation column using the McCabe-Thielemethod.


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SECTION 2: GAS ABSORPTION

NOTES OF GUIDANCE

Lab workActivity 2: Gas Absorption.

Learning outcome1. Describe the operation of gas absorption column.

2. Draw the process flow diagram (PFD) and piping and instrumentation diagram (P&ID) of gasabsorption column.

3. Demonstrate effective team role and responsibility in the task execution.

ScenarioYou have just joined as an assistant engineer in Linde Pte Ltd. You and your teammates have given atask to operate a gas absorption column of a carbon dioxide (CO2) with water as solvent. In addition,

you have to calculate the rate of absorption of CO2 into water. You can refer any references related tothe theory.

ObjectivesThis activity requires you to operate gas absorption column, carry out mass balance calculations on thegas absorption column and examine the effects of flow rate of CO2into water.

Upon completion of the test, write a technical memo of the result obtained. The memo should include(but not limited to) the following:

a) Clearly states test parameters

b) Test results

c) Evaluation of results


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A. Planning/Preparation (10 marks)

All team members arrive at the process operation site to discuss on the plan to examine the effect ofCO2absorption rate into water.

1. Familiarize with the gas absorption column by determining the line tracing of this system.2. Understand how the gas absorption works

a) The function of each component in the gas absorption column (receiving vessels, absorptioncolumn, centrifugal pump).

b) Explain gas absorption principles.3. Decide on the test parameters

B. Allocation of Roles and Teamwork (10 marks)

Analyze the tasks to be performed and divide among your team who to perform the tasks.

no Task description Member1 Introduction and theory

2 Collecting Data3 Analyze the result

4 Safety awareness

5 (any if necessary)

Explain the basis for your groups task allocation.

Explain how will failure in performing the role of one of the above mentioned task affect the teamperformance.

C. Hazard Identification and Safety Precaution (10 marks)

Before starting the operation of the gas absorption column, it is important to identify hazards andprecautions to be taken to ensure safety of operators. Study the process equipment, utilities involved,process materials and procedures carefully to identify potential hazards.

1. What are the hazards associated with the operation of gas absorption column?

2. What safety precautions would you take in relation to the above mentioned hazards?

D. Performance Test Procedure

1.0 OPERATING PROCEDURES

1.1 General Operating Proced ures

It is important that the user read and fully understand all the instructions and precautions statedin the manufacturer's manuals supplied with the absorption unit prior to operation. The following

procedures will serve as a quick reference for operating the unit.

1.2 General Start-Up Proced ures

a) Ensure all valves are closed except the ventilation valve V13.b) Check that all gas connections are properly fitted.c) Open the valve on the compressed air supply line. Set the supply pressure to between 2 to 3

bar by turning the regulator knob clockwise.


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d) Open the shut-off valve on the CO2gas cylinder. Check that the CO2cylinder pressure issufficient. Replace the cylinder if necessary.

e) Turn on the power for the control panel.

1.3 General Shut-Down Proceduresa) Switch off pump P1.b) Close valves V1, V2 and V12.c) Close the valve on the compressed air supply line and exhaust the supply pressure by

turning the regulator knob counterclockwise all the way.d) Close the shut-off valve on the CO2gas cylinder.e) Drain all liquid in the column K1 by opening valve V4 and V5.f) Drain all liquid from the receiving vessels B1 and B2 by opening valves V7 and V8.g) Drain all liquid from the pump P1 by opening valve V10.h) Turn off the power for the control panel.

1.4 Liquid Sampling Procedures

Samples can be taken from the liquid entering and exiting the absorption column for analysis.The sampling valves are located at:

a) V8 for inlet liquid to absorption column K1b) V7 for outlet liquid from absorption column K1

The procedures for collecting a sample are as follows:a) Drain any stagnated liquid above the sampling valve.b) ii) Place a vial below the sampling valve.c) iii) Open sampling valve and collect about 100 mL of sample.d) iv) Close the sampling valve.

1.5 Analysis of Dissolved CO2in Water

Water used for absorption should be deionised because presence of dissolved salts could affectthe analysis method as described below.

CHEMICALS NEEDED:a) Deionised and CO2 free waterb) Phenolphthalein indicator (AR grade)c) 1.0 L of standard 0.05 M sodium hydroxide (NaOH) solutiond) 100 mL of standard 0.01M sodium bicarbonate (NaHCO3) solution

PROCEDURES:a) Obtain a sample from Section 4.4.b) Prepare exactly 100 mL of sample in a conical flask.

c) Add 510 drops of phenolphthalein indicator. If the sample turns red immediately, no freeCO2is present. If the sample remains colourless, titrate with the standard 0.05 M NaOHsolution.

d) Measure the volume of 0.05 M NaOH required to reach the end point. The end pointoccurs when a definite pink colour persists in the solution for longer than 30 seconds.

e) For best results, use a colour comparison standard. Prepare exactly 100 mL of 0.01 MNaHCO3solution in a conical flask and add 510 drops of phenolphthalein indicator.


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2.0 EXPERIMENTAL PROCEDURES:

a) Fill the receiving vessel B2 through the charge port with 25 L of deionised water by openingvalve V3 and V5.

b) Close valve V3.c) Open valve V10 and valve V9 slightly. Observe the flow of water from vessel B1 through

pump P1.d) Open and adjust valve V1 to give a flow rate of 30 L/min air into column K1.e) Open and adjust valve V2 to give a flow rate of 2 L/min CO2into column K1.f) For continuous monitoring of CO2 composition at the outlet gas flow, open valve V12 and

slowly close valve V13 to give a flow rate of 2 L/min at FT-304. Always maintain this flowrate throughout the experiment.

g) Monitor the CO2composition at QI-401 until it is constant. Record the value.h) Switch on pump P1, then slowly open and adjust valve V11 to give a water flow rate of

around 0.5 L/min. Allow the water to enter the top of column K1, flow down the column andaccumulate at the bottom until it overflows back into vessel B2.

i) Start collecting liquid samples from both inlet and outlet of absorption column K1 (Section4.4). Always collect the samples simultaneously.

j) To collect liquid sample for outlet of the adsorption column, close valve V5, open valve V4and V7.

k) After finish collecting sample, close valve V4 and V7, open valve V5.l) Analyse the collected samples to determine the composition of dissolved CO2(Section 4.5).m) At the same time, record the outlet CO2composition at QI-401.n) Continue to collect the liquid samples and record the outlet CO2 composition at every 5-

minute intervals until there are no more changes in CO2composition over time.o) Throughout the experiment, monitor and maintain the air, CO2 and water flow rates by

adjusting the appropriate valves.p) At the end of the experiment, close valves V1, V2 and V12. Switch off pump P1. Transfer all

the CO2rich water in receiving vessel B1 to vessel B2.q) Repeat the experiment (steps 2 to 14) by changing the water flow rate from 0.5 to 1 L/min.r) Perform shut down procedure

E. Post-Experiment Assessment (10 marks)

a) Use the sample table in Appendix A, B, for data collection.b) Plot the CO2concentration in the outlet water flow as a function of time.c) Plot the CO2concentration in the outlet gas flow as a function of time.d) Compare the CO2concentration plots for different water flow rates.


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REPORT ASSESSMENT (10 MARKS)

F. Technical Memo

Draft a technical memo addressed to the Process Engineer of Linde Pte Ltd. on your teams evaluationof the distillation unit. Your memo can take the format of technical report format.

Enclosed: Test results of gas absorption and key findings

The enclosed Test results of gas absorption rate and key findings ofthe memo should include detailedtest results and key findings as follows:a) Test results. State the test parameters and provide proper tabulation with units clearly stated.

b) Evaluation of results.

For the section on Evaluation of results, you may use the following guiding questions to discuss theresults:

a) Calculate the concentration of CO2.

(Sample calculation of Concentration of CO2in Feed Tank)Let say volume of NaOH needed to reach end point = y ml,Molarity of NaOH = 0.05 mol/L,Thus, concentration of CO2in Feed Tank = (mol/l).

b) Plot the graph CO2 concentration in the outlet water flow as a function of time.c) Plot the CO2concentration in the outlet gas flow as a function of time.d) Compare the CO2 concentration plots for different water flow rates.

e) Calculate the rate of absorption into water.


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APPENDICES


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APPENDIX A

Theory on Distillation Column

The principle for continuous distillation is the same as for normal distillation: when a liquid mixture isheat so that it boils, the composition of the vapor above the liquid differs from the liquid composition. Ifthis vapor is then separated and condensed into a liquid, it becomes richer in the lower boilingcomponent(s) of the original mixture. This is what happens in a continuous distillation column. A mixtureis heated up, and routed into the distillation column. On entering the column, the feed starts flowingdown but part of it, richer in lower boiling component(s), vaporizes and rises. However, as it rises, itcools and while part of it continues up as vapor, some of it (enriched in the less volatile component)begins to descend again. Since a continuous distillation unit is fed constantly with a feed mixture andnot filled all at once like e a batch distillation, a continuous distillation unit does not need a sizabledistillation pot, vessel, or reservoir for a batch fill. Instead, the mixture can be fed directly into thecolumn, where the actual separation occurs. The height of the feed point along the column can vary onthe situation and is designed so as to provide optimal results. A continuous distillation is often a

fractional distillation and can be a vacuum distillation or a steam distillation.

Figure 1:A binary distillation separates a feed mixture stream into two fractions: one distillate and one

bottoms fractions


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SAMPLE TABLE FOR PREPARATION OF CALIBRATION CURVE

Purity of ethanol = __________Density of ethanol = _____ g/mL

Density of water = _____ g/mLMolar volume of ethanol = _____ mol/mLMolar volume of water = _____ mol/ml


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SAMPLE TABLE FOR EXPERIMENTS 1

Initial reboiler composition=Feed temperature =

Reflux ratio = _____Feed flow rate = _____ LPMDistillate flow rate = _____ LPMBottom product flow rate = _____ LPM


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PHYSICAL PROPERTIES OF COMPONENTS

Properties of Pure Components


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Figure: 2 X-Y Equilibrium Diagram for Methaol-Water System at 1 atm


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APPENDIX B

Theory on Gas Absorption

Gas absorption is a unit operation in which soluble components of a gas mixture are dissolved into aliquid phase. Absorption, in common with distillation, makes use of special equipment for bringing gasand liquid phases into intimate contact. Gas absorption is a unit operation in which soluble componentsof a gas mixture are dissolved into a liquid phase.

It is meant to demonstrate the absorption of carbon dioxide into water in a packed column. The gas andliquid normally flow counter currently, and the packings serve to provide the contacting anddevelopment of interfacial surface through which mass transfer takes place.

Consider a system in which a gaseous component A is in equilibrium with both air and water at a giventemperature. The equilibrium relationship between the partial pressure,pA in the gas phase and thecomposition,xA in the liquid phase can often be expressed by a straight line Henrys Law equation at

low concentrations.

pA = H xA [1]

where H is the Henrys Law constant for the given system expressed in atm/mole fraction. If both sidesof the equation is divided by the total pressure, P in atm, the composition, yA in the gas phase can berelated below:

yA = H xA [2]

where H is equal to H/P. However, H is more often used because it is independent of the total systempressure. Equilibrium data for most systems follow Henrys Law up to a concentration of about 1 mol%

in the liquid phase.

Single stage equilibrium process.

One in which two different phases are brought into intimate contact with each other and then areseparated. Various components transfer between the two phases and are essentially at equilibrium with

each other after considerable mixing. The process can be represented in Figure 2 below.


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Figure 3: Gas absorption column.


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SAMPLE TABLE FOR EXPERIMENT 2

Process: Absorption

Air flow rate : L/minCO2 flow rate : L/minCO2 inlet composition : vol%Liquid flow rate : L/min

Outlet gas Outlet waterTime (min) Vol% of CO2 in outlet

gasVol% of NaOH for

sample titration (mL)Vol% of CO2 in outlet

water

0

5

10

1520

25

3035

40

45

50

5560


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APPENDIX C

AssessmentThis activity contributes 20% of the marks weighting for this course. The distribution of marks for the

various activity component is contain in Table 1

Criteria 1 2 3 4 5 Points

LabPreparation

Unpreparedand needscompletedirectives fromdemonstrator

Marginalpreparation,needsconstantsupervision

Pre-preparation issatisfactory.Requiresoccasionalreminders.

Pre-preparation isvery good.Seems toknoweverything thatis required.

Pre-preparation isexcellent. Willoften helpothers in theexperiments.

FollowingProcedure

Lacks theappropriateknowledge of

the labprocedures

Often requireshelp from thedemomstratorto evencompletebasicprocedures

Demonstratesgeneralknowledge of

labprocedures

Requires helpfromdemonstratorwith somesteps inprocedures

Demonstratesgoodknowledge of

the labprocedures

Asks peers forhelp withproblems inlabprocedures

Works tofollow eachstep beforemoving on to

the next step

Demonstratessoundknowledge of

labprocedures

Discuss withpeers to solveproblems inprocedures

Carefullyfollows eachstep

Demonstratesvery goodknowledge of

the labprocedures

Gladly helpsother studentsto followprocedures

Thoroughlyand carefullyfollows eachstep beforemoving on to

next step

DataCollection

Measurementsareincomplete,inaccurate andimprecise

Observationsare incompleteor not included

Symbols, unitsand significant

figures are notincluded

Measurementsare somewhatinaccurate andvery imprecise

Observationsare incompleteor recorded ina confusingway

There are 3 or

more minorerrors usingsymbols, unitsand significantdigits or 2major errors

Measurementsare mostlyaccurate

Observationsare generallycomplete

Work isorganizedOnly 2 or 3minor errors

using symbols,units andsignificantdigits

Measurementsare accuratewithreasonableprecision

Observationsare thorough

Work isgenerally neatand

organized.Includessymbols, unitsand significantdigits

Measurementsare bothaccurate andprecise

Observationsare verythorough andmay recognizepossible errorsin datacollection

Work is neatandorganized.Includesappropriatesymbols, unitsand significantdigits


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Safety Proper safetyprecautionsareconsistentlymissed

Needs to beremindedoften duringthe lab

Proper safetyprecautionsare oftenmissed

Needs to beremindedmore thanonce duringthe lab

Proper safetyprecautionsare generallyused

May need tobe remindedonce duringthe lab

Proper safetyproceduresareconsistentlyused

Uses generalreminders ofsafe practicesindependently

Proper safetyprecautionsareconsistentlyused

Consistentlythinks aheadto ensuresafety

Will often helpother studentsto conductlabs safely

Q & ASession

Very poorresponses to

questions.

Marginalresponses.

Needsguideline tothe correctanswers.

Satisfactoryresponses to

questions withoccasionalmistakes

Very goodresponses to

questions andexhibit aboveaverageknowledge onexperiments

Exhibitexcellent

responses toquestions andable to discussthe subjectmatter

Clean-up Proper clean-up proceduresare seldomused

Needs to beremindedmore thanonce duringthe lab to useproper clean-up procedures

Proper clean-up proceduresgenerally used

Consistentlyuses properclean-upprocedures

Consistentlyuses properclean-upprocedures

help tocompleteclean-up

1 or 2 itemsleft at stationor not cleaned

May needsome help onoccasion tocompletetasks

Stationgenerally neatand clean

Often will helpother studentsto completetasks properly

3 or moreitems left atstation orstation notcleaned

Stationgenerally leftclean

Station alwaysleft neat andclean

3 or moreitems left atstation orstation notcleaned

Stationgenerally leftclean

Overall

performance

Unacceptable Marginal Acceptable Exceptional Excellent

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Lab Instruction Che 246