College of Engineering
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Department of
Chemical Engineering
College of Engineering |
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Experiment 300: Distillation
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This page presents some background information for Unit Operations Experiment 300: Distillation . This experiment investigates several operating conditions for the Technovate Fractional Distillation Column while separating a mixture of ethanol and n-propanol. Unlike other experiments in the Unit Operations Lab, this experiment was performed as a class, or rather as a SuperTeam.
Experiment 300 provides a platform for applying engineering theory to a real world situation involving distillation. The next section introduces the apparatus. This is followed by a section covering some safety issues related to working around the unit.
Distillation is a very important process. Many chemicals that you use on a daily basis have gone through a distillation column at some point. Please look to the "Everyday Uses" section here for some examples.
Experiment 300: Distillation involves an experimental apparatus with:
A process flow diagram and pictures of this apparatus are here.
Please see the materials safety page for Ethanol and n-propanol here.
Ethanol and propanol are mild skin irritants; therefore, nitrile or latex gloves are worn when the potential for contact exists. There is also an inhalant and ingestion hazard linked with these chemicals. Due to the nature of the experiment vapors from the two chemicals will escape although the air circulation should prevent inhalation of a significant amount of vapors. However, if eye irritation, headache, dizziness or nausea occurs, leave the lab immediately and inhale fresh air.
The distillation column is located in a hardhat area therefore when near the column a hard hat must be worn.
Safety glasses or goggles must be worn inside the lab at all times.
When removing the liquid or vapor samples, a pigskin glove may be worn due to the high temperature of the samples.
The energy to heat the reboiler must ONLY be turned on when the reboiler is filled above the red mark on the side of the tank. During operation the level must NOT fall below this level.
*When running the re-mix pump, at least one valve (either coming out of the products tank or the bottoms tank) must be open to ensure that the pump is not working against itself.
*After re-mixing, be sure that both valves are closed so that the feed pump can operate properly.
The cooling water should be turned on before any heating element is turned on to ensure that any vapor created is condensed.
The level in the distillate receiver must be above the red line for the products pump to be running.
When starting up, once condensation has begun to fill the distillate receiver, do NOT allow the level to go beyond the foil. To regulate this level, turn on the REFLUX pump to ensure the overall system maintains its initial component ratios.
*After all heated elements have been turned off, leave the reflux pump on to remove the distillate from the distillate receiver.
When stirring the feed tank after re-mixing, hitting the walls of the tank with the metal stirrer should be avoided to avoid the potential of sparks.
Finally, the cooling water can be turned off once no more condensate forms on the pipes within the condenser.
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There are essentially two parts to the theoretical background regarding the analysis of the distillation column in our laboratory. The first area of interest is predicting values of the bottoms and distillate ethanol mole fractions based on the number of theoretical stages measured at total reflux and the known feed, bottoms, reflux, and distillate flow rates for the various experimental runs.
The second area of interest is determining the theoretical minimum number of stages and minimum reflux ratio based on the measured values of the bottoms and distillate ethanol mole fractions, not at total reflux.
The theoretical minimum number of stages is the number of stages needed to reach a desired separation. The theoretical number of stages at total reflux may be calculated using the Fenske Equation and the McCabe Thiele Model.
The Fenske equation may be used to calculate the theoretical minimum number of stages, Nm, at total reflux for a distillation column with a total condenser.
XD=mole fraction of desired product in distillate
XB= mole fraction of desired product in bottoms
a1 = relative volatility of the overhead vapor
aw= relative volatility of the bottoms liquid
The McCabe Thiele model may also be used to determine the number of theoretical stages at total reflux. The following steps will enable one to determine the number of stages:
Draw the equilibrium line on an x-y plot.
Draw the y=x line.
Plot the measured bottoms and distillate ethanol mole fractions along the y = x line. For total reflux this line will be your operating line.
Draw a horizontal line from the distillate mole fraction on the operating line to the equilibrium line, followed by a vertical line drawn back down to the operating line. Repeat this until the desired bottoms composition is reached.
Count the number of times the horizontal line hits the equilibrium line to get the number of stages. Note: The last stage is the reboiler.
The McCabe Thiele Model is used to determine the theoretical number of stages when not at total reflux.
Draw the equilibrium line on an x-y plot.
Draw the y = x line.
Plot the bottoms, feed, and distillate ethanol mole fractions along the y = x line.
Plot the q-line (feed line) starting from the mole fraction of the feed extending through the equilibrium curve. The q-line is the moles of liquid produced per mole of feed. The feed is pure liquid therefore the q-line is 1 and should be at a 90 degree angle from the operating line.
Plot the enriching operating line. The enriching operating line is calculated using the following equation:
R is the reflux ratio.
xD= mole fraction of desired product in the distillate
xn is the composition leaving the nth stage.
yn+1 =vapor composition entering the bottom of the column
Plot the stripping operating line by extending a line from the bottoms mole fraction through the point where the enriching operating line intersects the q line.
Draw a horizontal line from the distillate mole fraction on the operating line to the equilibrium line, followed by a vertical line drawn back down to the operating line. Repeat this until the desired bottoms composition is reached.
Count the number of times the horizontal line hits the equilibrium line to determine the number of stages. Note: The last stage is the reboiler.
The reflux ratio R, relates the compositions of two streams passing each other. The following equation can be used to calculate the reflux ratio:
Ln is the reflux flow rate
D is the distillate flow rate
The minimum reflux ratio Rm is the reflux ratio that will require an infinite number of trays for a desired separation.
xD= mole fraction of desired component in distillate
y'=mole fraction in vapor where the operating lines touch the equilibrium line
x'= mole fraction in liquid where both operating lines touch the equilibrium line
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It may not be common knowledge, but distillation plays an important roll in the everyday American life. Distillation plays a roll in the water we drink, the two-for-one cocktails we have at happy hour, the gas we put in our cars, and even the perfumes we wear.
The list of company's that use distillation for chemical separations is endless, so there is no point in trying to list them all. Instead the following text gives a little information on a few products that undergo distillation at some point when they are being made and links to find out more information about these products and companies that make them.
The popularity of aroma-therapy has put distilled oils and scents in high demand. Essential Aura Aromatics a leader in the distillation of organic essential oils. This company uses ancient distillation methods from Arabia, Pakistan, and China. They promote the environmental sustainability of specific essential oil production and the use of organic essential oils.
Essential Aura distills with a portable distillation system. By having a portable still they have the flexibility to work with growers in different areas of Vancouver Island, British Columbia, and the Pacific North West. During the first half of 2000, a 400-liter Stainless Steel distillation system was built in Costa Rica. 15 different essential oils were distilled with this system with very positive results. A further 30 essential oils were distilled with there laboratory still.
For more in formation of this company visit their website at http://www.essentialaura.com.
Petroleum refineries are among the wonders of modern chemical engineering. These refineries are mazes of pipes, distillation columns, and chemical reactors that turn crude oil into usable, marketable products. Large refineries cost billions of dollars, employ several thousand workers, operate around the clock, and can be large as several hundred football stadiums. The U.S. has about 300 refineries that can process anywhere from 40 to 400,000 barrels of oil a day. These refineries turn out the gasoline and oil that quite literally keep the country running.
To learn more about petroleum refineries visit these website at http://www.exxonmobil.com/
During the 1980s and 1990s pop culture brought on a desire for healthier exercise, food, and cleaner water. As a result, the spring and tap water bottling industry has bloomed. Distillation has become the tool of choice for this industry. When combined with carbon filtration, the two processed will remove most of bacteria, viruses, cysts, and heavy metals and inorganics found in source water.
For more information on distilled water visit the following website: http://www.waterwise.com/water/distillers/index.html
3.4 Distillation of Ethyl Alcohol
Ethyl alcohol is the drinkable alcohol that is found in drinks like wine, beer, and liquor. In the making of alcoholic beverages, the distilled products of wheat, cereal grains, and grapes are combined with yeast and ethyl alcohol. If not for distillation, the strongest drink you would ever get would not be more than about 15% alcohol. Beyond this point, the fermentation process stops.
Here are some links about alcoholic beverages:
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http://www.irish-whiskey-trail.com/makeit/makeit.htm
http://www.homebrewheaven.com/default.htm.
4 Manufacturers
Buffalo Technologies Corp.
www.buffalotechnologies.com
Tel.: 888-529-9925
Fax: 716-895-8263
Vendome Copper and Brass Works, Inc.
www.vendomecopper.com
Tel.: 502-587-1930
Fax: 502-589-0639
GEA Evaporation Technologies, LL
www.evaptec.com
Tel: 410-992-7400
Fax: 410-992-7426
Patterson Industries (Canada) Limited
www.pattersonindustries.com
Tel.: 800-336-1110, Ext.1078
Fax: 416-691-2768
Quark Enterprises, Inc.
www.quarkglass.com
Tel.: 800-462-7062
Fax: 800-462-7063
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This section presents the process flow diagram and some pictures of the Distillation Column used for Experiment 300.
Front view of distillation column.
Control Panel.
Side view showing the column in relation to the control panel.
Back of the unit.
Bottoms Tank.
Close-up of the column showing the feed ports. (This column can be fed on different trays.)
Reboiler.
Varian Gas Chromatograph and accompanying Gateway Pentium 133 used for the data processing and printing of the GC's.
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Please direct all inquiries to:
decoteau@eng.fsu.edu
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