MEMORANDUM

TO: Daniel Groom FROM: Clayton Gregory and Antonio HernandezDATE: 08 June 2015SUBJECT: Distillation Operation Draft Report

Introduction:

The main objective for this experiment is for the students so gain experience operating and controlling industrial distillation equipment. Also, it is important for the students to learn how to perform field operational capacity tests of a column and understand the theory behind a column’s flood point and column flooding in general. The experiment will operate the column at a total reflux condition, obtain samples from the reboiler, each tray, and the accumulator, and analyze each sample in a gas chromatographer. McCabe-Thiele diagrams, Murphree efficiency equations, and tray compositions will be used to determine the efficiency of the column.

Methods:

Distillations columns are used to separate different components of a mixture based on the differences in the boiling points of such species. The components used in the experiment, water and ethanol, have boiling points of 100°C and 78°C, respectively. The mixture of water and ethanol forms an azeotrope, meaning the composition of the vapor and the composition of the liquid are directly proportional. The use of an optimum number of trays in a separation column can increase efficiency and purity of the separated components.

The methods and theory given in the experiment guide were used. Pre-Lab Questions:

1)The flooding velocities at the bottom of the column and at the top of the colmn were 3.01 m/s and 1.31 m/s, respectively.

2)Flooding Percentages 0.5 0.8 1 1.25

Steam Flow Rates (kg/min) 0.431773 0.690836 0.863546 1.079432

3)The first part of the column to flood will be towards the top, since vapor entrains liquid in its flow toward the top of the column (Pless, et al., 2002). From there, flooding will spread. This answer was confirmed by experimental results; the flooding velocity (0.90 kg/min) is closer to the value predicted by calculating for ethanol than the value predicted by calculating for water.

4)As the steam rate is increased, the vapor velocity and flow up the distillation column increases, restricting the flow of liquid down the column. This results in the increase of pressure drop (ΔP) across the column.

Flooding occurs when the internal vapor rate is so high that the liquid is unable to flow down the column. When flooding occurs in the distillation column, there is a very large pressure drop (ΔP) on the ΔP curve.

5)Entrainment is defined as the entrapment of one substance by another substance. In the context of the experiment, vapor at high rates entrains the downward-flowing liquid. In comparison, down-comer flooding occurs when the liquid backs up into the down-comer due to a large pressure drop across the tray. When the back-up liquid in the down-comer exceeds the tray spacing, liquid accumulates on the tray above.

8) McCabe Thiele Plotsa. Total reflux- 4 theoretical stagesb. Murphee efficiency of 0.82 – theoretical stagesc. Reflux Ratio of 1.8 – 6 theoretical stages

0.00 0.20 0.40 0.60 0.80 1.00 1.200.00

0.20

0.40

0.60

0.80

1.00

1.20

Total Reflux

Equilibrium Line45 degree line

0.00 0.20 0.40 0.60 0.80 1.00 1.200.00

0.20

0.40

0.60

0.80

1.00

1.20

Murphree Liquid Efficiency of 0.82

Equilibrium Line45 degree line

0.00 0.20 0.40 0.60 0.80 1.00 1.200.00

0.20

0.40

0.60

0.80

1.00

1.20

Reflux Ratio of 1.8

Equilibrium Line45 degree lineRectifying LineStripping Lineq-Line

Appendices

Appendix A: Safety

Overall Hazard Analysis

Description/ Details of steps in activities

Hazards Possible accidents/ consequences

Existing Risk Control

Usage of ethanol for distillation experiment

Fire/ explosive hazard

May result in a fire or explosion that may cause burns, other injuries and even death.

1) Donning of PPE such as safety goggles, lab coats and hard hats.2) Cooling water have be flowing before the steam valve is opened.3) Noting location of manual steam

valves and main shut-offs in the event of an emergency.

Gas cylinders of gas chromatograph are pressurized during experiments

Explosion / cracking due to pressurized cylinders

May cause burns and other injuries. Projectiles flying at high speed in the event of an explosion may hit operators.

1) Donning of PPE such as safety goggles, lab coats and hard hats.2) Ensuring pressure values are appropriately monitored and within the safe limits.3) Ensure cylinder is properly mounted and chained.

Distillation column may be subjected to overpressure (excessive pressure beyond what the column is designed for).

Explosion or cracking of the column due to high pressure.

May cause burns and other injuries. Projectiles flying at high speed in the event of an explosion may hit operators.

1) Column is protected against overpressure by pressure relief devices such as relief valves.2) Donning of PPE such as safety goggles, lab coats and hard hats.

Handling of hot valves or surfaces of hot objects. Accidental contact with steam pipes.

Burn hazard May cause varying degrees of burn injuries.

Donning of PPE as well as thick gloves. Be alert when in close proximity of steam pipes and other hot surfaces.

Climbing the column stairs

Sharp edges May cause cuts or lacerations.

Use care when climbing the column stairs. Be careful not to back into stairs when working under them.

Handling of electrical hazard during experiment and data collection

Electrical hazard Electrocution and electric shocks.

Check for any damaged electrical equipment or wires and any liquid

purposes. pools near electrical connections.

MSDS (Ethanol)Description:

Colorless clear liquid with a mild odor. Flammable liquid and vapor. Flash point = 16.6°C. Molecular weight = 46.0414 g/ mole, Boiling point (1 atm) = 78°C, Melting point =

-114.1°C, Solubility: Miscible Health Effects:

Causes severe eye irritation and moderate skin irritation when coming in contact. Ingestion may cause gastrointestinal irritation with nausea, vomiting and diarrhea.

May cause central nervous system (CNS) depression characterized by excitement, followed by headache, dizziness, drowsiness and nausea.

Causes respiratory tract irritation, dizziness or suffocation when inhaled. May have an adverse reproductive and fetal effects in humans. Prolonged exposure

may also cause liver, kidney and heart damage. First aid:

For eye contact, remove any contact lenses and immediately flush eyes with plenty of water for at least 15 minutes. Get medical attention immediately.

For skin contact, immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes.

Do NOT induce vomiting when ingested. Give the victim 2-4 cupfuls of milk or water if he is conscious and seek medical attention. Storage & Handling:

Container should be tightly closed and kept away from heat, sparks and flame. Keep away from sources of ignition and contact with oxidizing materials. Store in a cool, dry, well-ventilated area.

MSDS (Water)Description:

Colorless, odorless liquid Molecular weight = 18.02 g/ mole, pH (1% soln/water) = 7 (Neutral), Boiling point

(1 atm) = 100°C (212°F) Health Effects:

Non-corrosive for skin, non-irritant for skin. Non-sensitive for skin. Non-permeator by skin. Non-irritating to the eyes. Non-hazardous in case of ingestion. Non-hazardous in case of inhalation. Non-irritant for lungs. Non-sensitive for lungs. Non-corrosive to the eyes. Non-corrosive for lungs. First aid:

Not applicableStorage & Handling:

Not applicable

Appendix B: References

Friedman, K. (2015, Summer). Distillation Operation Experiment. Lab Handout ChE 264, TheUniversity of Texas at Austin.

Green, D.W., ed. (1984). Perry’s Chemical Engineering Handbook. Sixth Edition. McGraw-Hill Book Company, New York.

McCabe, W. L., Smith, J. C., & Harriott, P. (2005). Unit Operations of Chemical Engineering (7th ed.). Boston: McGraw Hill.

Pless, L., & Xu, S. X. (2002, June). Distillation tower flooding--more complex than you think: while other “predictive” methods tell too little, too late, gamma scans indicate where and why flooding occurs—invaluable insight for troubleshooters. (Feature Report). Chemical Engineering, 109(6), 60+.

Smith, J.M. and H.C. Van Ness. (1975). Introduction to Chemical Engineering Thermodynamics, Third Edition. McGraw-Hill book company, New York.

Weast, Robert C., et al. ed. (1985). CRC handbook of Chemistry and Physics, 66th Edition. CRC Press, Boca Raton, FL.

Appendix C: Sample Calculations

Flooding Velocity:

Flooding velocity calculation at the bottom of the distillation column: Assumption: Pure Water Physical Properties

V F=C F √ ( ρL−ρG )ρG

Where: VF = Flooding Velocity (m/s)CF = Empirical Constant (m/s)ρL = Liquid Density (g/cm3)ρG = Vapor Density (g/cm3)

CF=0.075ms

ρL

=0.95g

c m3

Vapor density calculation using the ideal gas law:Assumption: Pure Ethanol Physical Properties

ρG=P × MWR ×T

ρG=(1 atm )(18.02

gmol )

(0.08206L ∙atmmol ∙ K ) (373.15 K )

=0.5885gL=5.89 ×10−4 g

c m3

V F=(0.075ms )√ (0.95−5.89× 10−4 )

5.89× 10−4 =3.01ms

Flooding velocity calculation at the top of the distillation column:

ρG=(1 atm )(46.07

gmol )

(0.08206L ∙atmmol ∙ K ) (351.55 K )

=1.597gL=1.597 ×10−3 g

c m3

V F=(0.059ms )√ (0.789−1.597× 10−3 )

1.597 ×10−3 =1.31ms

Steam Flow Rates:

Steam flow rate calculation using an energy balance around the reboiler at 50% flooding:

msteam=H vap , ethanolV top

H vap , steam

Where:

V top=fA ρG V F

MW

Therefore: msteam=H vap , ethanol× f × A × ρG ×V F

H vap , steam × MW

Where:f = Fraction of Flooding (unitless)

A = Column Area (cm2)ρG = Density of Ethanol Vapor (g/cm3)VF = Flooding Velocity (cm/s)MW = Molecular Weight of Ethanol (g/mol)

msteam=9674

calgmol

× 0.5× π × 7.52 cm2× 1.597 ×10−3 g

cm3× 131

cms

9718cal

gmol× 46.07

gmol

×(1.081kg ∙ s

mol ∙min )

msteam=0.432kg

min

Average Molecular Weight:

Average Molecular Weight calculation of the feed stream:

M W feed=∑ ¿¿¿Where:

x ij=mass fraction of component i∈stream j

M W feed=[|0.32 gethanol

gfeed | mo lehtanol

46.07 gethanol|+|0.68gwater

g feed | mo lwater

18.02 gwater|]

−1

=22.38g feed

mo lfeed

Average Molar Flow Rate:

Average Molar Flow Rate calculation of the feed stream:

n j=m j ( M W j)−1

Where:n j=mol ar flow rate of stream j

m j=mass flow rate of stream j

˙n feed=|35 kg feed

min | kgmo lfeed

22.38 kg feed|=1.56

kgmolfeed

min

Average Mole Fraction:

Average Mole Fraction calculation of the feed stream:

y ij=¿¿¿

y EF=(|0.32 k gethanol

k gfeed | kgmolethanol

46.07 k gethanol|)(22.38

k g feed

kgmolfeed)=0.16

kgmo lethanol

kgmolfeed