A fractionating column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities. Fractionating columns are used in small-scale laboratory distillations as well as for large-scale industrial distillations. Laboratory distillation set-up using, without a fractionating column 1: Heat source 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed... Volatility in physics is a measure of the speed at which a chemical element or chemical compound evaporates. ...

Laboratory fractionating columns

A laboratory fractionating column is a piece of glassware used to separate vaporized mixtures of liquid compounds with close volatilities. It can also be called a fractional column. Most commonly used is either a Vigreux column or a straight column packed with glass beads or metal pieces such as Raschig rings. A Vigreux column is a type of fractionating column. ... Raschig rings are referred to as random packing and are used in commercial fractional distillation columns to reduce pressure loss (versus using trays), while maintaining good efficiency and economy. ...

Image 1: Fractional distillation apparatus using a Liebig condenser

Fractionating columns help to separate the mixture by allowing the mixed vapors to cool, condense, and vaporize again in accordance with Raoult's law. With each condensation-vaporization cycle, the vapors are enriched in a certain component. A larger surface area allows more cycles, improving separation. This is the rationale for a Vigreux fractionating column or a packed fractionating column. Spinning band distillation achieves the same outcome by using a rotating band within the column to force the rising vapors and descending condensate into close contact, achieving equilibrium more quickly. Diagram , drawn by theresa knott. ... Diagram , drawn by theresa knott. ... Liebig condenser The Liebig condenser or straight condenser is a piece of laboratory equipment consisting of a straight glass tube surrounded by a water jacket. ... In chemistry, Raoults law states that the vapor pressure of mixed liquids is dependent on the vapor pressures of the individual liquids and the molar vulgar fraction of each present in solution. ... A Vigreux column is a type of fractionating column. ...

As shown in Image 1, as a liquid mixture in the round bottomed flask is boiled, vapor rises up the fractionating column. The vapor condenses on the glass platforms (known as trays or plates) inside the column, and runs back down into the liquid below and refluxes the upflowing distillate vapor. The hottest tray is at the bottom of the column and the coolest tray is at the top. At steady state conditions, the vapor and liquid on each tray is at equilibrium. Only the most volatile of the vapors stays in gaseous form all the way to the top. The vapor at the top of the column, then flows through the water-cooled condenser, which cools the vapor down until it condenses into a liquid distillate. The separation may be enhanced by the addition of more trays (to a practical limitation of heat, flow, etc.) A theoretical plate in separation processes is a hypothetical zone in which two phases establish an equilibrium, also referred to as an equilibrium stage or a theoretical tray. ... Diagram of typical reflux apparatus. ... HELLO EVERYONE!! Steady state is a more general situation than Dynamic equilibrium. ... Vapor-liquid equilibrium, abbreviated as VLE by some, is a condition where a liquid and its vapor (gas phase) are in equilibrium with each other, a condition or state where the rate of evaporation (liquid changing to vapor) equals the rate of condensation (vapor changing to liquid) on a molecular... This article or section does not cite its references or sources. ... Look up condenser in Wiktionary, the free dictionary. ...

Image 2: Typical industrial fractionating columns

Image File history File linksMetadata Download high-resolution version (1609x2120, 552 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Distillation Fractional distillation Fractionating column User talk:Shanel Reflux Continuous distillation User talk:Randfan/Super Desk Metadata This... Image File history File linksMetadata Download high-resolution version (1609x2120, 552 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Distillation Fractional distillation Fractionating column User talk:Shanel Reflux Continuous distillation User talk:Randfan/Super Desk Metadata This...

Industrial fractionating columns

Fractional distillation is one of the unit operations of chemical engineering.^[1][2] Fractionating columns are widely used in the chemical process industries where large quantities of liquids have to be distilled.^[3][4][5] Such industries are the petroleum processing, petrochemical production, natural gas processing, coal tar processing, brewing, liquified air separation, and hydrocarbon solvents production and similar industries but it finds its widest application in petroleum refineries. In such refineries, the crude oil feedstock is a very complex multicomponent mixture that must be separated and yields of pure chemical compounds are not expected, only groups of compounds within a relatively small range of boiling points, also called fractions and that is the origin of the name fractional distillation or fractionation. It is often not worthwhile separating the components in these fractions any further based on product requirements and economics. Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate. ... Unit operation is the basic principle of chemical engineering. ... Chemical engineering is the branch of engineering that deals with the application of physical science (e. ... Pumpjack pumping an oil well near Lubbock, Texas Ignacy Łukasiewicz - inventor of the refining of kerosene from crude oil. ... Petrochemicals are chemical products made from raw materials of petroleum (hydrocarbon) origin. ... A natural gas processing plant Natural gas processing plants are used to purify the raw natural gas extracted from underground gas fields and brought up to the surface by gas wells. ... Coal tar is the liquid by-product of the distillation of coal to make coke. ... A 16th century brewer A 21st century brewer This article concerns the production of alcoholic beverages. ... Liquid air is air that has been liquified by compression and cooled to very low temperatures. ... Oil refineries are key to obtaining hydrocarbons; crude oil is processed through several stages to form desirable hydrocarbons, used in fuel and other commercial products. ... A substance is soluble in a fluid if it dissolves in the fluid. ... View of Shell Oil Refinery in Martinez, California. ... Alternate use: Boiling Point, English title of Kitano Takeshis film 3-4X Jūgatsu; Boiling Point (TV series) The boiling point of a substance is the temperature at which it can change state from a liquid to a gas throughout the bulk of the liquid. ...

Industrial distillation is typically performed in large, vertical cylindrical columns (as shown in image 2) known as "distillation towers" or "distillation columns" with diameters ranging from about 65 centimeters to 6 meters and heights ranging from about 6 meters to 60 meters or more.

Image 3: Chemical engineering schematic of a continuous fractionating column

Image 4: Chemical engineering schematic of typical bubble-cap trays in a fractionating column

Industrial distillation towers are usually operated at a continuous steady state. Unless disturbed by changes in feed, heat, ambient temperature, or condensing, the amount of feed being added normally equals the amount of product being removed. Image File history File links Continuous_Binary_Fractional_Distillation. ... Image File history File links Tray_Distillation_Tower. ...

It should also be noted that the amount of heat entering the column from the reboiler and with the feed must equal the amount heat removed by the overhead condenser and with the products. [edit] Reboilers Reboilers are heat exchangers typically attached to a distillation column. ... Look up condenser in Wiktionary, the free dictionary. ...

Image 3 depicts an industrial fractionating column separating a feed stream into one distillate fraction and one bottoms fraction. However, many industrial fractionating columns have outlets at intervals up the column so that multiple products having different boiling ranges may be withdrawn from a column distilling a multi-component feed stream. The "lightest" products with the lowest boiling points exit from the top of the columns and the "heaviest" products with the highest boiling points exit from the bottom.

Industrial fractionating columns use external reflux to achieve better separation of products.^[3][5] Reflux refers to the portion of the condensed overhead liquid product that returns to the upper part of the fractionating column as shown in Image 3.

Inside the column, the downflowing reflux liquid provides cooling and condensation of upflowing vapors thereby increasing the efficacy of the distillation tower. The more reflux and/or more trays provided, the better is the tower's separation of lower boiling materials from higher boiling materials.

The design and operation of a fractionating column depends on the composition of the feed and as well as the composition of the desired products. Given a simple, binary component feed, analytical methods such as the McCabe-Thiele method^[5][6][7] or the Fenske equation^[5] can be used. For a multi-component feed, simulation models are used both for design and operation. The graphical approach presented by McCabe and Thiele in 1925, the McCabe-Thiele Method is considered the simplest and perhaps most instructive method for analysis of binary distillation. ... The Fenske equation in fractional distillation is an equation for calculating the minimum number of theoretical plates required for separation of a binary feed stream by a fractionation column operated at total reflux (i. ... Look up simulation in Wiktionary, the free dictionary. ...

Bubble-cap "trays" or "plates" are one of the types of physical devices which are used to provide good contact between the upflowing vapor and the downflowing liquid inside an industrial fractionating column. Such trays are shown in Images 4 and 5.

The efficiency of a tray or plate is typically lower than that of a theoretical 100% efficient equilibrium stage. Hence, a fractionating column almost always needs more actual, physical plates than the required number of theoretical vapor-liquid equilibrium stages. A theoretical plate in separation processes is a hypothetical zone in which two phases establish an equilibrium, also referred to as an equilibrium stage or a theoretical tray. ... Vapor-liquid equilibrium, abbreviated as VLE by some, is a condition where a liquid and its vapor (gas phase) are in equilibrium with each other, a condition or state where the rate of evaporation (liquid changing to vapor) equals the rate of condensation (vapor changing to liquid) on a molecular...

Image 5: Section of fractionating tower of Image 4 showing detail of a pair of trays with bubble caps

In industrial uses, sometimes a packing material is used in the column instead of trays, especially when low pressure drops across the column are required, as when operating under vacuum. This packing material can either be random dumped packing (1–3" wide) such as Raschig rings or structured sheet metal. Liquids tend to wet the surface of the packing and the vapors pass across this wetted surface, where mass transfer takes place. Differently shaped packings have different surface areas and void space between packings. Both of these factors affect packing performance. Image File history File links Bubble_Cap_Trays. ... A packed bed is a hollow tube or pipe that is filled with a packing material. ... Raschig rings are referred to as random packing and are used in commercial fractional distillation columns to reduce pressure loss (versus using trays), while maintaining good efficiency and economy. ... The term Structured packing refers to a range of specially designed materials for use in distillation columns and chemical reactors. ... Mass transfer is the phrase commonly used in engineering for physical processes that involve molecular and convective transport of atoms and molecules within physical systems. ...

See also

• Azeotropic distillation
• Batch distillation
• Continuous distillation
• Extractive distillation
• Fractional distillation
• Laboratory glassware
• Steam distillation
• Theoretical plate
• Vacuum distillation

In chemistry, azeotropic distillation is any of a range of techniques used to break an azeotrope in distillation. ... Bold textBold textBatch distillation[1] refers to the use of distillation, the separation of components in a system by volatilities, in batches. ... Continuous distillation is a distillation process, which does not require interruption for adding raw material. ... Extractive Distillation is defined as distillation in the presence of a miscible, high boiling, relatively non-volatile component, the solvent, that forms no azeotrope with the other components in the mixture. ... Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate. ... Brown glass jars with some clear lab glassware in the background Laboratory glassware refers to a variety of equipment, traditionally made of glass, used for scientific experiments and other work in science, especially in chemistry and biology laboratories. ... Laboratory set-up for steam distillation Steam distillation is a special type of distillation (a separation process) for temperature sensitive materials like natural aromatic compounds. ... A theoretical plate in separation processes is a hypothetical zone in which two phases establish an equilibrium, also referred to as an equilibrium stage or a theoretical tray. ... This article or section does not cite its references or sources. ...

References

1. ^ Editors: Jacqueline I. Kroschwitz and Arza Seidel (2004). Kirk-Othmer Encyclopedia of Chemical Technology, 5th Edition, Hoboken, NJ: Wiley-Interscience. ISBN 0-471-48810-0. 
2. ^ McCabe, W., Smith, J. and Harriott, P. (2004). Unit Operations of Chemical Engineering, 7th Edition, McGraw Hill. ISBN 0-07-284823-5. 
3. ^ ^{a b} Kister, Henry Z. (1992). Distillation Design, 1st Edition, McGraw-Hill. ISBN 0-07-034909-6. 
4. ^ King, C.J. (1980). Separation Processes. McGraw Hill. 0-07-034612-7. 
5. ^ ^{a b c d} Perry, Robert H. and Green, Don W. (1984). Perry's Chemical Engineers' Handbook, 6th Edition, McGraw-Hill. ISBN 0-07-049479-7. 
6. ^ Beychok, Milton (May 1951). "Algebraic Solution of McCabe-Thiele Diagram". Chemical Engineering Progress. 
7. ^ Seader, J. D., and Henley, Ernest J.. Separation Process Principles. New York: Wiley. ISBN 0-471-58626-9. 

Distillation Design provides complete coverage of the design of industrial distillation columns for the petroleum refining, chemical and petrochemical plants, natural gas processing, pharmaceutical, food and alcohol distilling industries. ... Perrys Chemical Engineers Handbook was first published in 1934 and the seventh edition was published in 1997. ...

External Links

• Drawings of laboratory glassware fractionating columns
• More drawings of glassware including Vigreux columns

• Distillation Theory by Ivar J. Halvorsen and Sigurd Skogestad, Norwegian University of Science and Technology, Norway
• Distillation, An Introduction by Ming Tham, Newcastle University, UK
• Distillation by the Distillation Group, USA
• Distillation simulation software
• Fractional Distillation Explained for High School Students