Distillation
Distillation is a process used to separate components of a liquid mixture based on differences in their volatilities. It involves heating the mixture to create vapor, which is then cooled and condensed back into liquid form. This method is commonly used in the purification of liquids and the production of alcoholic beverages.
7 Key excerpts on "Distillation"
eBook - ePubFood Processing Technology
Principles and Practice
- P.J. Fellows(Author)
- 2009(Publication Date)
- Woodhead Publishing(Publisher)
...These are necessary to avoid sandiness, a texture defect that affects the mouthfeel. Further information is given by Goff (2007). 14.2 Distillation Distillation is the separation of more volatile components of a liquid mixture from less volatile components by the application of heat. The volatile-rich vapours are condensed to form a concentrated product. Although common in the chemical industry, Distillation in food processing is mostly confined to the production of alcoholic spirits and the preparation of volatile flavour and aroma compounds (e.g. production of essential oils and other flavouring ingredients, or aroma recovery in evaporation). 14.2.1 Theory In a liquid that contains two components, for example alcohol and water, the molecules are attracted to each other by van der Waals forces. The intermolecular forces (or linkages) that attract similar molecules are greater than those that attract dissimilar molecules. This has two important implications for Distillation: first, a dilute alcoholic feed material is easier to distil than a more concentrated feed liquor. This is because in dilute solutions the alcohol molecules are separated by a larger number of water molecules and there are thus fewer of the stronger alcohol-alcohol linkages and more of the weaker alcohol–water linkages. Therefore on heating the weaker alcohol–water linkages are broken more easily and the more volatile alcohol is vaporised. A feed liquor for alcohol Distillation is typically 5–7% ethanol rather than the more usual 10-13% found for example in wines (see also fermentation in Chapter 6, section 6.4.3). The second implication of intermolecular attraction is that the distillate contains a high proportion of alcohol molecules, and thus a large number of the stronger alcohol–alcohol linkages. This makes it much more difficult to further concentrate the alcohol by a second Distillation...
eBook - ePubIndustrial Separation Processes
Fundamentals
- André B. de Haan, H. Burak Eral, Boelo Schuur(Authors)
- 2020(Publication Date)
- De Gruyter(Publisher)
...Chapter 2 Evaporation and Distillation 2.1 Separation by evaporation 2.1.1 Introduction A large part of the separations of individual substances in a homogeneous liquid mixture or complete fractionation of such mixtures into their individual pure components is achieved through evaporative separations. Evaporative separations are based on the difference in composition between a liquid mixture and the vapor formed from it. This composition difference arises from differing effective vapor pressures, or volatilities, of the components in the liquid mixture. The required vapor phase is created by partial evaporation of the liquid feed through adding heat, followed by total condensation of the vapor. Due to the difference in volatility of the components, the feed mixture is separated into two or more products whose compositions differ from that of the feed. The resulting condensate is enriched in the more volatile components, in accordance with the vapor–liquid equilibrium (VLE) for the system at hand. When a difference in volatility does not exist, separation by simple evaporation is not possible. The basis for planning evaporative separations is knowledge of the VLE. Technically, evaporative separations are the most mature separation operations. Design and operating procedures are well established. Only when VLE or other data are uncertain, a laboratory and/or pilot plant study is necessary prior to the design of a commercial unit. The most elementary form is simple Distillation in which the liquid mixture is brought to boiling, partially evaporated and the vapor formed is separated and condensed to form a product...
eBook - ePub- Zeki Berk(Author)
- 2008(Publication Date)
- Academic Press(Publisher)
...Chapter 13. Distillation 13.1. Introduction Distillation is a separation operation based on differences in volatility. If a mixture containing substances that differ in their volatility is brought to ebullition, the composition of the vapors released will be different from that of the boiling liquid. After condensation, the vapors constitute the ‘distillate’. The remaining liquid is called ‘residue’ or ‘bottoms’. One of the oldest separation processes, Distillation is of central importance in the chemical process industry. In the food sector, its main application is in the production of ethanol and alcoholic beverages from fermented liquids. Other food-related applications include the recovery, fractionation and concentration of volatile aromas as well as recovery of organic solvents (desolventation) in the production of edible oils by solvent extraction and removal of undesirable odorous substances (e.g. deodorization of cream). Distillation may be carried out as a batch or as a continuous process. 13.2. Vapor–Liquid Equilibrium (VLE) Consider a binary liquid solution consisting of substances A and B. If the mixture behaves as an ideal solution, the vapor pressure of substance A, p A, is given by Raoult's law (François-Marie Raoult, French chemist, 1830–1901), as formulated in Eq. (13.1) : (13.1) where: x a =concentration of A in the solution, in mol fraction =vapor pressure of pure A, at the temperature of the solution. If, furthermore, the vapor phase behaves as an ideal gas mixture, then Dalton's law (John Dalton, English physicist and chemist, 1766–1844) applies. The partial pressure of A in the vapor is then: (13.2) where: y A =concentration of A in the vapor phase, in mol fraction P=total pressure. At equilibrium, the partial pressure of A in the gas must be equal to the vapor pressure of A over the solution...
eBook - ePub- John Kenkel(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...The separation is based on the solid’s solubility in a liquid solvent. A solvent is chosen such the solid is sparingly soluble at room temperature, but whose solubility increases considerably at higher temperatures. Both soluble and insoluble impurities are considered to be present, and the procedure removes both if their concentrations are not too large. The key to the procedure is to use a minimum amount of solvent, such that the solid will just dissolve at the elevated temperature (usually the boiling point, if the solid is stable at that temperature). While maintaining this elevated temperature, any impurity that has not dissolved can be filtered out. The “insoluble” impurities are thus removed. Soluble impurities, however, are still present in the filtrate. This is where the minimum amount of solvent comes into play. The procedure calls for the temperature to be lowered back to the original value. The soluble impurities will stay dissolved if their solubility has not been exceeded (if they are present in a small amount). However, the solid being purified will have its solubility exceeded. Since the minimum amount of solvent was used to just dissolve the solid at the elevated temperature, it will thus precipitate from the solution. The solid, presumably purified, can then be filtered and dried. It may be necessary to perform the recrystallization several times in order to get the desired purity. 8.3 Distillation Distillation is a method of purification of liquids contaminated with either dissolved solids or miscible liquids. The method consists of boiling and evaporating the mixture followed by recondensation of the vapors in a “condenser,” which is a tube cooled by isolated, cold tap water. The theory is that the vapors (and thus recondensed liquids) will be purer than the original liquid. The separation is based on the fact that the contaminants have different boiling points and vapor pressures than the liquid to be purified...
- William L. Luyben(Author)
- 2012(Publication Date)
- Wiley-AIChE(Publisher)
...CHAPTER 3 PRINCIPLES OF Distillation DESIGN AND CONTROL The separation section of the process has the job of taking the reactor effluent and producing reactant, recycle and product streams at their required purities. There are many separation techniques: Distillation, extraction, absorption, adsorption, gas diffusion through membranes, pervaporation, crystallization. The most widely applied and dominant separation technique is Distillation, so we will discuss this very important separation technology in this chapter. The design and control of the separation section of a process depends heavily on the design and control of the reaction section. And vice versa. In this chapter we discuss basic principles of Distillation design and control. Distillation columns are somewhat more complex to design because there are more design optimization variables: pressure, total number of trays, feed-tray location, reflux ratio (RR), and product composition specifications. But there are a number of heuristics that have been developed over the years that are quite effective and simplify the design optimization problems. On the other hand, the control of Distillation columns is somewhat easier and in a sense less critical because Distillation columns display well-behaved, stable, dynamic responses. Temperature runaways do not occur. However, tight control of the product streams leaving the columns is important to product-quality issues. Their multivariable nature introduces a measure of complexity compared to simple control of a single temperature in a reactor. There are a wide variety of Distillation columns because chemical components have a wide range of boiling points. Columns operate from vacuum conditions (10 mm Hg) to high pressure (20 atm). Temperature levels vary from cryogenic conditions to 600 K. There are a number of optimization variables in Distillation design that must be determined...
eBook - ePubHandbook of Molecular Gastronomy
Scientific Foundations, Educational Practices, and Culinary Applications
- Christophe Lavelle, Herve This, Alan L. Kelly, Roisin Burke, Christophe Lavelle, Herve This, Alan L. Kelly, Roisin Burke(Authors)
- 2021(Publication Date)
- CRC Press(Publisher)
...Distillation: The Behaviour of Volatile Compounds during Distillation of Hydro-Alcoholic Solutions and during Hydro-Distillation Martine Esteban-Decloux Unité Mixte de Recherche Ingénierie Procédés Aliments, AgroParisTech, INRAE, Université Paris-Saclay, F-91300 Massy, France When food ingredients are cooked, many volatile compounds are formed and escape. The goal of this chapter is to give some information on the behaviour of odorant compounds during the Distillation of hydro-alcoholic solutions, and to make a link with their elimination through steam Distillation. Characterization of Volatility Distillation is a unit operation that makes it possible to separate compounds all together present in one phase by using volatility differences. It is generally performed at pressures close to atmospheric pressure (from 0.2 bar to some bars). For each pure species separately, it is possible to calculate the saturating vapour pressure P sat as a function of temperature by using equation (31.1). The coefficients are generally given in handbooks or databases (Perry et al., 1997 ; ProSim, 2019). P s a t = e x p (a + b T + c. l n (T) + d. T e) (31.1) where T (kelvin) is the absolute temperature, P sat (Pascal) is the saturating vapour pressure, and a, b, c, d and e are particular constants for the various compounds. For example, Table 31.1 gives the values for water, ethanol and some categories of volatile compounds of the families of alcohols, esters, aldehydes and terpenes. TABLE 31.1 Coefficients for the Riedel Equation (31.1) According to ProSim (2019) for Water and Some Compounds of the Families of Alcohols, Esters, Aldehydes and Terpenes Compound Tmin (°C) Tmax (°C) a b c d e Water 0 374 73.64900 −7258.20000 −7.30370 4.1653 × 10 −6 2 Ethanol −114 241 73.30400 −7122.30000 −7.14240 2.8856 × 10 −6 2 Methanol −98 239 82.11780 −6905.50000 −8.86220 7.4664 × 10 −6 2 1-propanol −126 263 84.66416 −8307.24422 −8.57673 7.0509 ×...
eBook - ePubPinch Analysis for Energy and Carbon Footprint Reduction
User Guide to Process Integration for the Efficient Use of Energy
- Ian C. Kemp, Jeng Shiun Lim(Authors)
- 2020(Publication Date)
- Butterworth-Heinemann(Publisher)
...For example, in Figure 7.8 a further refinement has been added; instead of feeding the reactor with cold feed, it is preheated below the pinch. This will increase the heat that needs to be removed from the reactor, but since this is done above the pinch, it can be usefully used to heat the process. Reactor systems have been analysed in depth by Glavic et al (1988) and Smith and Omidkhah Nasrin (1993). 7.4: Distillation columns Distillation columns are of great importance in process analysis, as they are both the most common and the most energy-intensive separation system, and hence they were also the first separation system to be analysed specifically from a pinch viewpoint, by Linnhoff, Dunford and Smith (1983). Since then, many additional insights have been found. 7.4.1: Overview of basic analysis method In Distillation columns, a two- or multi-component mixture of volatile liquids is separated by application of heat. The difference in relative volatility makes the composition of the vapour phase different to that of the liquid phase. However, the difference is almost never enough to allow effective separation in a single stage. A tower with multiple trays is generally used and a large proportion of the top vapour is condensed and recycled to the column. Generally, Distillation is a very energy-intensive operation. It is also the most common liquid-phase separation system and is therefore treated in some depth here. The method of splitting the grand composite curve, described in Section 7.2.3, is generally very effective for analysing Distillation columns. However, important assumptions were made in the simple example given there which simplified the analysis considerably...
