iPedia Free Information Center

Information about Batch Distillation

Batch distillation[1] refers to the use of distillation in batches, meaning that a mixture is distilled to separate it into its component fractions before the distillation still is again charged with more mixture and the process is repeated. This is in contrast with continuous distillation where the feedstock is added and the distillate drawn off without interruption.

Batch distillation has always been an important part of the production of seasonal, or low capacity and high-purity chemicals. It is a very frequent separation process in the pharmaceutical industry and in wastewater treatment units.

Batch rectifier

Diagram of a Batch Rectifier
The simplest and most frequently used batch distillation configuration is the batch rectifier, including the alembic and pot still. The batch rectifier consists of a pot (or reboiler), rectifying column, a condenser, some means of splitting off a portion of the condensed vapour (distillate) as reflux, and one or more receivers.

The pot is filled with liquid mixture and heated. Vapour flows upwards in the rectifying column and condenses at the top. Usually, the entire condensate is initially returned to the column as reflux. This contacting of vapour and liquid considerably improves the separation. Generally, this step is named start-up. After some time, a part of the overhead condensate is withdrawn continuously as distillate and it is accumulated in the receivers, and the other part is recycled into the column as reflux.

Owing to the differing vapour pressures of the distillate, there will be a change in the overhead distillation with time, as early on in the batch distillation the components with a lower vapour pressure wil be evaporated first. As the supply of the material is limited and lighter components are removed, the relative fraction of heavier components will increase as the distillation progresses.

Batch stripper

Diagram of a Batch Stripper
The other simple batch distillation configuration is the batch stripper. The batch stripper consists of the same parts as the batch rectifier. However, in this case, the charge pot is located above the stripping column.

During operation (after charging the pot and starting up the system) the high boiling constituents are primarily separated from the charge mixture. The liquid in the pot is depleted in the high boiling constituents, and enriched in low boiling ones. The high boiling product is routed into the bottom product receivers. The residual low boiling product is withdrawn from the charge pot. This mode of batch distillation is very seldom applied in industrial processes.
Diagram of a Middle Vessel Column

Middle vessel column

A third feasible batch column configuration is the middle vessel column. The middle vessel column consists of both a rectifying and a stripping section and the charge pot is located at the middle of the column.

Feasibility studies

Generally, the feasibility studies of batch distillation are based on analyses of the following maps:
  • Residue Curve map
  • still path map
  • distillate path map
  • different column profile maps
During the feasibility studies, the following basic simplifying assumptions are made:
  • an infinite number of equilibrium stages
  • an infinite reflux ratio
  • a negligible tray hold-up in the two column sections
  • a quasi-steady state in the column
  • a constant molar overflow
Bernot et al.[2] used the batch distillation regions to determine the sequence of the fractions. According to Ewell and Welch,[3] a batch distillation region gives the same fractions upon rectification of any mixture lying within it. Bernot et al.[2] examined the still and distillate paths for the determination of the region boundaries under high number of stages and high reflux ratio, named maximal separation. Pham and Doherty in pioneering work[4] described the structure and properties of residue curve maps for ternary heterogeneous azeotropic mixtures. In their model, the possibility of the phase separation of the vapour condensed is not taken into consideration yet. The singular points of the residue curve maps determined by this method were used to assign batch distillation regions by Rodriguez-Donis et al.[5][6] and Skouras et al.[7][8] Modla et al.[9] pointed out that this method may give misleading results for the minimal amount of entrainer. Lang and Modla[10] the method of Pham and Doherty and suggested a new, general method for the calculation of residue curves and for the determination of batch distillation regions of heteroazeotropic distillation.

Lelkes et al.[11] published a feasibility method for the separation of minimum boiling point azeotropes by continuously entrainer feeding batch distillation. This method has been applied for the use of a light entrainer in the batch rectifier and stripper by Lang et al. (1999)[12] and it applied for maximum azeotropes by Lang et al.[13] Modla et al.[9] extended this method for batch heteroazeotropic distillation under continuous entrainer feeding.

See also

References

1. ^ Kister, Henry Z. (1992). Distillation Design, 1st Edition, McGraw-Hill. ISBN 0-07-034909-6. 
2. ^ Bernot C., M. Doherty, M. and M. F. Malone, Patterns of composition change in multicomponent batch distillation, Chem. Eng. Sci., 45, 1207, (1990)
3. ^ Ewell, R. H. and L. M. Welch, Rectification in Ternary Systems Containing Binary Azeotropes, Industrial Engineering Chemistry, 37, 1224,(1945)
4. ^ Pham, H. N. and M. F. Doherty, Design and synthesis of heterogeneous azeotropic distillations II. Residue curve maps, Chem. Eng. Sci., 45, 1987-1843, (1990)
5. ^ Rodriguez-Donis I, V. Gerbaud and X. Joulia, Feasibility of Heterogeneous Batch Distillation Processes, AIChE Journal, 48 (6), 1168, (2002)
6. ^ Rodriguez-Donis Y., J. A. Equijarosa, V. Gerbaud and X. Joulia, Heterogeneous Batch-extractive Distillation of Minimum Boiling Azeotropic Mixtures, AIChE Journal, 49 (12), 3074, (2003)
7. ^ Skouras S., V. Kiva and S. Skogestad, Feasible separations and entrainer selection rules for heteroazeotropic batch distillation, Chemical Engineering Science, 60, 2895, (2005)
8. ^ Skouras S., S. Skogestad and V. Kiva, Analysis and Control of Heteroazeotropic Batch Distillation, AIChE Journal, 51 (4), 1144-1157, (2005)
9. ^ Modla G., P. Lang, B. Kotai and K. Molnar, Batch Heteroazeotropic Rectification of a Low Relative Volatility Mixture under Continuous Entrainer Feeding, AIChE Journal, 49 (10), 2533, (2003)
10. ^ * Lang P. and Modla G., Generalised method for the determination of heterogeneous batch distillation regions, Chem. Eng. Sci., 61, 4262-4270, (2006)
11. ^ Lelkes Z., P. Lang, P. Moszkowicz, B. Benadda and M. Otterbein, Batch extractive distillation: the process and the operational policies, Chem. Eng. Sci., 53,1331 (1998)
12. ^ Lang, P., Lelkes Z., Otterbein M., Benadda B., Modla G. ”Feasibility studies for batch extractive distillation with a light entrainer”, Comp. Chem. Eng., 23, S93-S96, (1999).
13. ^ Lang P., G. Modla, B. Benadda and Z. Lelkes, Homoazeotropic Distillation of Maximum Azeotropes in a Batch Rectifier with Continuous Entrainer Feeding: I. Feasibility Studie, Comp. Chem. Eng., 24, 1465, (2000)

Further reading

  • Perry, Robert H. and Green, Don W. (1984). Perry's Chemical Engineers' Handbook, 7th Edition, McGraw-Hill. ISBN 0-07-049841-5. 
  • Johann G. Stichlmair, James R. Fair (1998). Distillation: principles and practice. Wiley-VCH. ISBN 0-471-25241-7. 
  • I.M. Mujtaba (2004). Batch Distillation:Design and Operation. Imperial College Press. ISBN 1-86094-437-X. 
  • Hilmen Eva-Katrine, Separation of Azeotropic Mixtures:Tools for Analysis and Studies on Batch Distillation Operation, Thesis, Norwegian University of Science and Technology Department of Chemical Engineering, (2000).
  • Beychok, Milton (May 1951). "Algebraic Solution of McCabe-Thiele Diagram". Chemical Engineering Progress. 
 •  • [ e]
Concepts in distillation
PrinciplesRaoult's law, Dalton's law, Reflux, Fenske equation, McCabe-Thiele method, Theoretical plate
Industrial processesBatch distillation, Continuous distillation, Fractionating column
Laboratory methodsRotary evaporator, Kugelrohr, Spinning band distillation
TechniquesFractional distillation, Vacuum distillation, Extractive distillation, Reactive distillation, Dry distillation, Destructive distillation, Azeotropic distillation, Steam distillation
Distillation is a method of separating chemical substances based on differences in their volatilities in a boiling liquid mixture. Distillation usually forms part of a larger chemical process, and is thus referred to as a unit operation.
..... Click the link for more information.
Continuous distillation, a form of distillation, is an ongoing separation in which a mixture is continuously (without interruption) fed into the process and separated fractions are removed continuously as output streams as time passes during the operation.
..... Click the link for more information.
Editing of this page by unregistered or newly registered users is currently disabled due to vandalism.
If you are prevented from editing this page, and you wish to make a change, please discuss changes on the talk page, request unprotection, log in, or .
..... Click the link for more information.
sEParation is an EP by Destroy Babylon, released on May 4th, 2007.

Tracks

1. Dubblespeak
2. Apathy Keeps Me Going
3. A Pathetic Dubb Ya
4. Choice Hops
5. The President's Hidden Horns
6. ADD to the Oligopuzzle
7.
..... Click the link for more information.
A pharmaceutical company, or drug company, is a commercial business whose focus is to research, develop, market and/or distribute drugs, most commonly in the context of healthcare. They can deal in generic and/or brand medications.
..... Click the link for more information.
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and
..... Click the link for more information.
alembic (From Arabic,Al-ambiq الأنبيق ) is an alchemical still consisting of two retorts connected by a tube. Technically, the alembic is only the upper part (the capital or still-head
..... Click the link for more information.
A pot still is a type of still used in distilling spirits such as whisky or brandy. Heat is applied directly to the pot in which the mash (in the case of whisky) or wine (in the case of Cognac) is contained.
..... Click the link for more information.
Reboilers are heat exchangers typically used to provide heat to the bottom of industrial distillation columns. They boil the liquid from the bottom of a distillation column to generate vapors which are returned to the column to drive the distillation separation.
..... Click the link for more information.
Reflux is a technique used in industrial and laboratory distillations. It is also used in chemistry to apply energy to reactions over a long time.

Reflux in industrial distillation

The term reflux [1][2]
..... Click the link for more information.
Reflux is a technique used in industrial and laboratory distillations. It is also used in chemistry to apply energy to reactions over a long time.

Reflux in industrial distillation

The term reflux [1][2]
..... Click the link for more information.
Node: Residue curves begin and end at nodes.

Stable node: The component or azeotrope with the highest boiling point in the region. All the residue curves in the region point to (terminate) at this point.
..... Click the link for more information.
In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i.e. density, crystal structure, index of refraction, and so forth).
..... Click the link for more information.
An azeotrope is a mixture of two or more pure compounds (chemicals) in such a ratio that its composition cannot be changed by simple distillation.[1] This is because when an azeotrope is boiled, the resulting vapor has the same ratio of constituents as the
..... Click the link for more information.
In chemistry, azeotropic distillation[1] is any of a range of techniques used to break an azeotrope in distillation. In chemical engineering, azeotropic distillation
..... Click the link for more information.
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.
..... Click the link for more information.
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.
..... Click the link for more information.
A heteroazeotrope is an azeotrope where the vapour phase coexists with two liquid phases.

Examples of heteroazeotropes

  • Benzene - Water NBP 69.2 °C
  • Dichloromethane - Water NBP 38.5 °C

See also

  • Azeotrope
  • Batch distillation
  • Distillation

..... Click the link for more information.
A pot still is a type of still used in distilling spirits such as whisky or brandy. Heat is applied directly to the pot in which the mash (in the case of whisky) or wine (in the case of Cognac) is contained.
..... Click the link for more information.
Steam distillation is a special type of distillation (a separation process) for temperature sensitive materials like natural aromatic compounds.

Many organic compounds tend to decompose at high sustained temperatures.
..... Click the link for more information.
Vacuum distillation is a method of distillation whereby the pressure above the liquid mixture to be distilled is reduced to less than its vapor pressure (usually less than atmospheric) causing evaporation of the least volatile liquid(s) (those with the highest boiling points).
..... Click the link for more information.
A theoretical plate in many separation processes is a hypothetical zone or stage in which two phases, such as the liquid and vapor phases of a substance, establish an equilibrium with each other.
..... Click the link for more information.
Distillation Design
Author Henry Z. Kister
Language English
Subject(s) Chemical engineering: Distillation design
Publisher McGraw-Hill
Publication date 1992 (1st Edition)
Media type Hardback
Pages 710
..... Click the link for more information.
Relative volatility is a measure comparing the vapor pressures of the components in a liquid mixture of chemicals. This quantity is widely used in designing large industrial distillation processes.
..... Click the link for more information.
Perry's Chemical Engineers' Handbook
Author Perry, R.H. and Green, D.W. (Editors)
Language English
Subject(s) Chemical Engineering
Publisher McGraw-Hill
Publication date June 1997 (7th Edition)
..... Click the link for more information.
Distillation is a method of separating chemical substances based on differences in their volatilities in a boiling liquid mixture. Distillation usually forms part of a larger chemical process, and is thus referred to as a unit operation.
..... Click the link for more information.
Raoult's law states that
The vapor pressure of an ideal solution is dependent on the vapor pressure of each chemical component and the mole fraction of the component present in the solution [1].

..... Click the link for more information.
Dalton's law (also called Dalton's law of partial pressures) states that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture.
..... Click the link for more information.
Reflux is a technique used in industrial and laboratory distillations. It is also used in chemistry to apply energy to reactions over a long time.

Reflux in industrial distillation

The term reflux [1][2]
..... Click the link for more information.
The Fenske equation in continuous fractional distillation is an equation used for calculating the minimum number of theoretical plates required for the separation of a binary feed stream by a fractionation column that is being operated at total reflux (i.e.
..... Click the link for more information.


This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.
Herod_Archelaus


page counter