How to make high-quality alcohol, and what is the difference between rectified and distillate. These two technologies for the production of alcohol and moonshine raise questions among beginners. They wonder what the technology is all about and which one is better? What is the difference between distillation and rectification, using what methods and devices to achieve the desired result.
When they say “distill moonshine”, this means distillation (distillatio is a Latin word, translated as dripping). During distillation, alcohol vapors evaporate from the mash and condense. To increase the strength and get rid of excess impurities, moonshine is distilled several times.
Distillation is the production of alcohol from mash using a distiller
To do this, the ripened mash is heated and waited for evaporation. After cooling, the steam that has passed through the cooler (coil) condenses and an aqueous-alcohol solution begins to drip. Distillation is divided into simple and fractional. What is the difference between them?
Simple distillation or production of raw alcohol, the mash is simply distilled on a moonshine still in a quick way without separation into fractions. With this distillation, impurities are not removed from the drink, as required by the technology. The first drops of moonshine with harmful impurities remain in the drink. This product has an unpleasant odor. Some unscrupulous winemakers purify low-quality distillate with chemicals to get rid of the smell. This alcohol is harmful to health, as it contains methyl alcohol, harmful aldehydes and fusel oils. This method requires further processing, fractional distillation with separation into fractions or rectification.
Good moonshine is obtained by fractional distillation with the separation of head and tail fractions, which are harmful and are not needed in the final product. This method allows you to get a high-quality drink.
Features of fractional distillation:
After distilling twice, the finished drink is free of harmful impurities, its strength is 90-92%. The moonshine turns out pure, but the specific taste and aroma of the raw materials is preserved.
To obtain drinking alcohol at home, use a special distillation column. This device is a little more complicated than moonshine, but it is quite affordable and is commercially available. Most of the new generation moonshine stills come as a distiller or rectification column at the same time; by simply changing the configuration, you can make alcohol and moonshine. The cost of high-quality columns is quite high, but it is better not to buy inexpensive models, as they can spoil the drink.
The process of rectification is different from re-distillation. The purity of the alcohol at the output is at least 96%. The rectification column produces alcohol without the taste and aroma of the raw material. For rectification, you cannot use pure mash, only raw alcohol after the first distillation with a strength of 30-40%.
To evaluate the advantages and disadvantages of rectified and distillate, it is important to decide which result you want: a delicate taste of the drink or pure alcohol.
Distillation and rectification - these methods are used to obtain different products: moonshine is obtained by distillation, and vodka is a rectification product
Main differences:
It’s difficult to say whether it’s better to drink distillate or rectified drink. These are different alcoholic drinks; some people prefer moonshine, while others prefer alcohol. Opponents of rectification argue that rectification produces a “dead” drink.
For systems without an azeotropic point and far from the critical point, the rule is true that in equilibrium with the liquid phase, vapor is always enriched with a more volatile component, i.e. one that, in its pure form, has a lower boiling point and a higher vapor pressure. In any case (except Tyr, close to critical) Konovalov’s first law is valid: vapor in equilibrium with the liquid phase is relatively richer in that component, the addition of which increases the phase equilibrium pressure at a given temperature or lowers the phase equilibrium temperature at a given pressure.
Another rule, known as Konovalov's third law, states: with an increase in the content of one of the components in the liquid phase at a constant temperature or pressure, its content in the equilibrium gas phase increases.(That is, y in is an increasing function of x in.)
These properties are the basis for a method of separating the components of liquid mixtures called distillation or distillation. Let's imagine that a mixture of benzene and toluene was heated at constant pressure to a temperature where the figurative point passed approximately halfway in the region of two-phase states (point “a” in Fig. 7.7). Equilibrium vapor at point “d” has a mole fraction of benzene y in, which is greater than the benzene content p v / p in system. If the system is “opened” and the steam is condensed separately from the liquid phase, the result is a liquid (condensate) enriched in benzene compared to the initial composition. The condensate can be heated again to liquid-steam equilibrium, the system can be opened and steam, even richer in benzene, can be condensed into a separate container. By repeating the process several times, you can get almost pure benzene, although in smaller quantities, the purer it is. A similar process of separating components can be accomplished at a constant temperature by reducing the pressure to evaporate, then separating the vapor, and then increasing the pressure to condense in a separate container. This separation method is called isothermal distillation.
Rice. 7.7.
In practice, instead of staged condensation into different containers, a continuous process is used in which steam and liquid move in a vertical factional column over a container containing the liquid being distilled. This type of distillation is called fractional distillation. The steam rises through a column that has many “shelves” for condensation. The liquid flows down the shelves in the opposite direction. In steady state, which is achieved after some time of operation of the device, the temperature in the column is smoothly distributed along the height from high temperatures at the bottom to lower temperatures at the top. Since the compositions of liquid and vapor are functions of temperature, vapor with a relatively high content of the higher boiling point component condenses on low shelves, while the vapor rising through the column is enriched in the lower boiling point component. As a result of successive condensation, on its upward path the steam gradually becomes enriched in one component and finally condenses into a separate container. Figure 7.8 gives an idea of how this process can be carried out in the laboratory. The fractional column in such an installation is called a reflux condenser. It is a hollow tube, usually glass, with a heat-insulating jacket around it and many small glass
Rice. 7.8. Distillation with a reflux condenser in the laboratory of parts inside (for example, poured glass rings or radial projections from glass walls). The final condensation occurs in a “refrigerator” - a hollow tube around which cold water flows to sharply reduce the temperature of the steam.
For a given difference in boiling temperatures of pure components, the degree of enrichment of steam with one component depends on the length and design of the fractionation column. From this point of view, the process is characterized number of theoretical plates(plates on which sequential condensation and evaporation of the mixture could occur). This number can be calculated using a liquid-vapor diagram, if you imagine that the processes of evaporation and condensation occur in stages and with the maximum possible enrichment at each stage (on each plate). For example, if, as a result of distillation, a benzene-toluene mixture is enriched from xb = 0.20 to xb = 0.81, then the number of theoretical plates in the phase diagram of this system is three (Fig. 7.9).
Rice. 7.9.
In industry, it is often necessary to separate a mixture of many components, some of which differ significantly in volatility, while others differ very little. For this purpose, a preliminary, rough separation into fractions is first carried out by simple distillation, and then one or each of the fractions is distilled with reflux to completely separate the components. The deeper separation stage is called rectification. In industrial production, a distillation column can be up to 75 m high and feature thousands of theoretical plates. This is necessary to separate components that have very close boiling points.
If there is an azeotrope point on the system diagram, then the separation of the liquid into pure components is impossible. For any initial composition (with the exception of pure components and the azeotrope itself), the most complete separation ends in two liquids: one pure component and an azeotrope. For example, a mixture of ethanol and water has an azeotropic composition with weight fractions of 96% ethanol and 4% water (at normal pressure). This ethanol content is the maximum that can be achieved by distillation of any binary mixture of water - ethanol with an initial water content of more than 4%. On the other hand, the existence of an azeotropic point makes it possible to obtain two-component mixtures with a precisely defined and known composition. For example, concentrated hydrochloric acid HC1 (aqueous solution) has a mass fraction of HC1 known to five significant figures, namely 20.222% if obtained by distillation at 101.325 kPa (standard pressure). This industrial product is used in laboratories to prepare HC1 solutions with precisely known concentrations.
When it is necessary to purify a solvent from solutes that have a very high boiling point or a very low vapor pressure at ordinary temperature (such as inorganic salts), fractional distillation is not necessary. It is enough to use simple distillation: evaporate the liquid and condense it into a separate container. Such simple distillation is widely used to purify water from “hardness salts” and iron hydroxides - common impurities in tap water in cities.
Distillation is often carried out at atmospheric pressure. But if the boiling point of the distilled liquid is high, and especially if the substance decomposes at this temperature, then distillation is used at reduced pressure and, accordingly, at a lower temperature. In many cases, there is no need to reduce the total pressure in the system with a pump; it is enough to introduce an inert component into it, which does not mix with the substance being distilled in the liquid phase, but simply reduces the partial pressure of the saturated vapor. For organic substances that are practically immiscible with H20 in the liquid phase, steam distillation is used.
In practice, steam distillation consists of passing H 2 0 steam through the liquid being distilled (in which H 2 0 is practically insoluble) so that a mixture of saturated vapors is above the liquid when the temperature of the system rises to the joint boiling point of water and liquid G A+B. The gas phase is condensed separately and two liquids are obtained: water and the purified distilled product.
The efficiency of this process is usually characterized by the ratio of the mass of water /Poison to the mass of the product distilled with it W/IW (steam consumption per 1 kg of distilled substance). Since distillation is carried out at pressure R, equal to the sum of the saturated vapor pressures of pure components: R = r in + r A, can be written for the mass of one component in the gas phase:
Similarly for the mass of the second component:
As a result:
Since the molar mass of water (component A) is much less than the molar mass of any organic substance with a high boiling point, steam consumption is usually relatively small.
Basic types of concentration, purification and separation of substances.
Currently, there are a significant number of methods for separating, concentrating and purifying substances, and more and more new ones are being created due to the relevance of the problems of obtaining and analyzing superpure materials with specified properties, for example, for nanoelectronics, semiconductor and computer technology, and new generation biological drugs. The most common ones are:
Ø evaporation methods (distillation, evaporation and distillation);
Ø ashing;
Ø extraction;
Ø precipitation and coprecipitation;
Ø controlled crystallization;
Ø sorption and ion exchange methods;
Ø electrochemical methods.
The use of each purification method is determined both by the chosen analysis technique and by the physicochemical properties of the system (aggregate state of the components, chemical and thermal stability of the substances, content of the component being determined in the original sample, etc.). Usually at the heart of the cleaning process lies either a chemical reaction (precipitation reactions, ion exchange, oxidation) or a physical process (diffusion, adsorption and desorption, evaporation and condensation) (Figure 2.1).
Figure 2.1 – general principles and methods of separating components into phases (concentrating and separating substances).
Considering the variety of methods for concentrating substances, let us explain the meaning of some terms.
Separation is an operation as a result of which the components included in the initial mixture are separated from each other.
Concentration is a process as a result of which the content of the determined or purified component in a substance increases compared to its original content. Concentration can be absolute And relative.
Absolute concentration– this is the transfer of a microcomponent (impurity) from an initial sample of large volume or mass to a new sample with a smaller volume (mass). Such concentration occurs during the processes of extraction, precipitation, distillation, etc.
Relative concentration (enrichment) consists of increasing the content of the component of interest in the original sample relative to other components or solvent. For example, when evaporating a solution or ashing a sample.
Evaporation – the process of transition of a substance from a liquid or solid phase to a gaseous phase, which is carried out in one way or another. Evaporation methods can be implemented in the form distillation and distillation (evaporation, evaporation and sublimation).
Distillation- this is separation liquid mixtures, based on the transfer of the volatile component into the gas phase by evaporation and subsequent condensation.
Condensate– a product formed during cooling of the gas or vapor phase.
Distillation– removal of volatile components from solids (powders, crystals) or solutions when heated.
Evaporation– a distillation method, during which part of the solvent and volatile impurities are removed as a result of prolonged heating of the sample. During evaporation, part of the base (usually the solvent) remains in the sample.
Evaporation(until dry) accompanied complete removing solvent and volatile components from the original sample.
Sublimation or sublimation is a process in which a solid is transferred to the gas phase without going through the melting stage. The condensation product formed during the sublimation process is called sublimate.
Ashing– a method in which the original sample is converted into a mineral residue by heating is called ash. It is usually used when analyzing various substances for the content of microelements or total organic matter (soil analysis). Distinguish dry ashing when a sample of a substance is heated in a crucible at temperatures not exceeding 500ºС, and damp (wet). At wet ashing The initial sample of the substance is placed in a crucible and treated with either acids or alkalis, and the resulting volatile products are removed during the process of calcination. Ashing can be considered as a special case mineralization samples.
Distillation method
Distillation (distillation) belongs to a group of methods based on thermal evaporation of substances, and is used for water purification and separation of organic liquids from relatively close boiling temperatures. She based on differences in the volatility of substances. The essence of the distillation process is that in an evaporator a mixture of substances (usually a solution) is heated above the boiling point of the most volatile component. The gas (vapor) phase thus formed has a higher concentration of the volatile component compared to the original solution. This phase is then cooled (condensed) in a refrigerator, resulting in condensate(liquid or solid) enriched with the most volatile compound. If necessary, the process is repeated until the required degree of separation or concentration of the components is achieved.
The distillation process can be characterized quantitatively by calculating distribution coefficient D. Let there be a 2-component ideal system A + B(there is no intermolecular interaction, and the components are chemically inert towards each other). When such a system is heated to the evaporation temperature, for example a component A, we obtain a gas phase that is in equilibrium with the remaining solution. In this case, the gas phase will be enriched with a more volatile component A, and in the remaining solution the concentration of the component will increase accordingly IN. Mole fractions of components A And IN in both phases are related by the relation:
where y A and y B are mole fractions in the gas phase; a = 1/D – separation coefficient (relative volatility); x A and x B are the mole fractions of the components in the liquid phase. Considering that x + y = 1 is the sum of the molar fractions of the components in the original solution, and x A + x B = x; y A + y B = y, then the distribution coefficient D can be calculated from the relation:
D= 
. (2.2)
Formula (3.2) can be transformed using the Clausius-Clapeyron equation into an expression for approximate calculation of the volatility of the components:
lga = 8.9 
. (2.3)
where T boil (A) and T boil (B) are the boiling temperatures of the separated components A And IN respectively. From formula 2.3 it follows that The higher the difference in boiling points of the separated components, the higher the degree of their separation in a one-stage process.
In the food, pharmaceutical and chemical industries, distillation is one of the water treatment methods that is used along with ion exchange. For analytical purposes, water is either single purified (distillate) or double purified - bidistillate. Single stage distillation is commonly used to separate substances with significant differences in boiling points. In this case, both the liquid phase remaining after distillation and the gas phase, and hence the resulting condensate, can be enriched in the analyzed component. This method is not suitable for azeotropic mixtures(systems in which the composition of the gas and liquid phases are the same and are in a state of equilibrium). In this case, complete separation of the components cannot be achieved.
Method step distillation (rectification) carried out in special columns and used for separation into fractions multicomponent homogeneous mixtures of liquids with fairly close boiling points. It is widely used in the processing industry, in particular, in the production of petroleum distillation products, such as petroleum ethers, gasolines, kerosenes and oils.
When purifying products with low thermal stability, inherent in some organic and biologically active substances, molecular distillation - low temperature distillation in high vacuum, which is carried out at a residual pressure of 1.3 - 1.8 kPa and below. In this case, the separation and concentration process can occur either without heating or at temperatures significantly below room temperature. Molecular distillation is used in the production of pharmaceuticals and bioactive food supplements.
Distillation methods.
Distillation divided into simple or evaporation And sublimation (sublimation). At evaporation substances are removed in the form of ready-made volatile compounds. Evaporation can be carried out in various ways: heating from below(water and sand baths); above(infrared lamps), using vacuum drying (freeze drying) - to eliminate losses of bound moisture or thermally unstable components. Evaporation allows, for example, to significantly increase the concentration of salts in the solution (producing brine).
A special case of evaporation - evaporation to dryness . This technique is used when it is necessary either to significantly increase the concentration of a non-volatile component, or when the solvent and volatile impurities interfere with the analysis. At evaporation the substance is first carefully heated for a long time ( evaporate) until an almost dry residue forms. Sometimes additionally calcining the dry residue at a higher temperature is used to remove trace amounts of solvent. The quality of evaporation can be controlled by changing the mass of the dry residue.
Distillation will be more effective if the substance is also affected chemically using reagents - dry and wet mineralization . Mineralization of samples is widely used in elemental organic analysis. The sample, organic or biological, is placed in a tube furnace or autoclave through which air or oxygen is blown. In the process of oxidation (combustion), volatile compounds are formed such as CO, CO 2, N 2, SO 2, SO 3, which can easily be determined using special instruments - gas analyzers or, after selective absorption ( adsorption) gases, according to standard methods. With ear mineralization the analysis error is higher than with wet. This is due to the loss of highly volatile components and partly non-volatile components captured by droplets of the resulting aerosol. Reducing the loss of substance during dry mineralization can be achieved by using autoclaves(devices for heating at elevated pressure).
Wet mineralization consists of exposing a sample to mineral acids or alkalis in combination with oxidizing agents (H 2 O 2 , KClO 3 , KMnO 4 ), the dissolution of stable compounds is carried out in autoclaves under heating and high pressure, and the determination is carried out in special chambers connected to the analyzer. It is also effective to use a number of solid, liquid and gaseous mineralizers capable of selectively converting some sparingly soluble substances into the gas phase (halogens and hydrogen halides, CCl 4, AlCl 3, BBr 3).
Sublimation This is a variant of distillation, which consists in separating substances by transferring one or more components when heated into the gas phase, bypassing the liquid phase. For this purpose, devices are used - sublimators, consisting of an evaporator and a sublimation zone with a lower temperature (down to negative). In the sublimation zone, when gases condense, a solid substance (sublimate) is formed again. This method can be used when the components being separated are, for example, poorly soluble or difficult to melt. The limited use of sublimation is due to the small number of matrices suitable for this purpose. An example of sublimation purification for analytical purposes is the separation of crystalline iodine from non-volatile impurities.
The quality of cleaning during sublimation is affected by the size of the particles and the uniformity of the distribution of components in them. Therefore, distillation will be of higher quality in carefully crushed samples, as well as in those where the main substance is distilled off ( macrocomponent), not impurities ( micro components).
For low-temperature complete dehydration of unstable substances, low-temperature distillation under vacuum is used - freeze drying, which can be considered as an option freeze drying, performed in a more rigorous mode.
Extraction method.
Method extraction separation (extraction) is widely used not only in chemical analysis, but also in production, as it allows you to concentrate the analyte in a small volume of solution. The extraction process is based on the selective extraction of one or more components from a mixture of liquid or solid phases using an organic solvent (extractant) that is immiscible with water. The extraction process is based on difference in solubility of mixture components in aqueous and organic phases. Many inorganic salts (nitrates, chlorides, thiocyanates) and complex compounds dissolve well in organic substances (alcohols, ethers, gasoline, etc.).
More efficient extraction occurs when using a mixture of extractants. The phenomenon of increasing the degree of extraction when exposed to a mixture of extractants is called synergism. The degree of extraction can also be increased by adding an extraction reagent to the extractant, for example, dithizone or hydroxyquinoline, which form complexes with many metal cations. As a result of extraction it turns out extract, which can be either in the form of a solution or a dry substance ( dry extracts). Dry extracts are usually formed from liquid extracts by drying them in some way.
TO basic concepts of this method include:
Ø re-extraction– the process of extracting the isolated component from the extract into an aqueous or other phase;
Ø re-extractant– a reagent solution (usually aqueous) used to extract a substance from an extract;
Ø coextractant– an organic or other solvent used in a mixture with the main extractant in order to increase the selectivity of the process or the degree of extraction;
Ø synergy– a significant increase in the degree of extraction (extraction) when using a mixture of extractants, compared to the action of each of them separately;
Ø extractant– an organic or other solvent that extracts a component from an aqueous solution;
Ø extraction reagent– an integral part of the extractant, a reagent that forms with the extracted substance a compound that is highly soluble in the extractant, most often an organic complex;
Ø extract– organic phase containing the isolated component;
Ø extractor– apparatus for carrying out extraction.
The designs of extractors are quite diverse (Fig. 2.2) and are selected depending on the process conditions and the reagents used.
Figure 2.2 – diagrams of extractors for various purposes
(c – aqueous phase; o – organic solvent):
a – separating funnels (the case when the density of the extractant is higher than that of the aqueous phase); b – continuous extraction device (with extractant density lower than water).
There are: batch extraction(performed in separate portions of extractant), continuous(with constant movement of phases relative to each other, while the aqueous phase is usually stationary) and countercurrent, where the organic phase is constantly moved through a series of extraction tubes containing fresh portions of an aqueous solution. As a simple extractor, you can use a separating funnel with two taps (Fig. 2.2 - a), which is used to perform periodic extraction. After filling the funnel with an aqueous-organic mixture of solution, it is shaken vigorously and allowed to settle; the aqueous solution is carefully removed through the bottom tap (if the density of the organic reagent is less than the aqueous one), trying to ensure that the extract remains in the funnel. The separation of fractions occurs at high speed within 1 – 3 minutes. If the density of the organic phase is higher than the aqueous phase, then the extract will accumulate in the lower part of the funnel, which is then also carefully removed.
Distillation and rectification are widely used in industry. Using these methods, ethyl alcohol is purified, kerosene, gasoline, diesel fuel and other components are separated from oil, aromatic substances are obtained in perfumery, and much more.
Both technologies are based on the same principle of liquid distillation. However, there are differences, and quite serious ones.
Distillation is a process during which a liquid in a cube (container) is heated and evaporated, after which it cools and condenses. The vapor can ultimately be converted into a liquid or solid (the second option is not discussed in this article). The output product is called distillate. Or the bottom residue (the so-called liquid that has not evaporated), depending on the purpose for which the original mixture was distilled.
Construction of a simple apparatus for producing distilled water. The liquid is in cube 1 with a lid 2 and a thermometer 3. After heating the container, the water turns into steam, which rises up and enters tube 4 with valve 5. And from there into tube 6, located in refrigerator 7. So that the steam condenses and again has turned into a liquid state, it needs to be cooled. To do this, tube 6 is washed with running ice water. To improve cooling efficiency, it is wound in a spiral to keep the steam at a lower temperature for longer. After leaving the refrigerator, the liquid enters a vessel to collect the distillate.
When distilling a mixture consisting of two components (one of them is the base dissolving liquid, and the second is dissolved in it), a low-boiling one, that is, one with a lower boiling point, turns into steam. And high-boiling (with a higher boiling point) remains in a liquid state. A thermometer is needed to regulate the degree of heating so that this parameter is between the specified temperatures.
A distinctive feature of distillation is the fact that the volatile components evaporate once. With such a simple method it is impossible to achieve a high degree of separation of the components of the mixture. Additionally, only one ingredient stands out.
Rectification is a process at the initial stage of which the liquid, like distillation, is also heated and evaporated. But then the steam enters the distillation column. In it, due to the countercurrent between the liquid and gaseous phases of the mixture, thermal and mass exchange occurs between the steam and the condensed drops. The initial mixture is divided (with a high degree of purification) into components with different boiling points due to the fact that the liquid actually evaporates and condenses many times.
Diagram of a simple rectifier that can be made even at home. It consists of a cube heated over a fire or water bath. Above it there is a rectification column (in household devices - a drawer, which is a rigid pipe) with nozzles that fill it (in the figure they are called “scourers”, because for home devices they are often made from cheap metal kitchen sponges). Above it is a reflux condenser. On the side, opposite the distillate selection unit, there is a special outlet tube (colored red in the diagram). It is connected to the refrigerator and then to the receiving container. In laboratory and household rectifiers, nozzles are used as “scourers” with which the column is filled. The most popular: spiral prismatic (Selivanenko) and regular wire (Panchenkov). The first gives the best degree of cleaning, the second, with fairly effective operation, is the simplest in design. They are usually made from stainless steel or copper. In industrial installations, special plates are used instead of nozzles.
The device works as follows. The initial mixture is heated in the distillation cube and begins to evaporate. The steam passes through a distillation column. At the distillate selection unit, part of the steam is removed through the red tube, enters the refrigerator, condenses and flows into the receiving container. The other part rises into the reflux condenser. The latter is, in fact, another refrigerator with running water in a jacket. In it, this second part of the steam also condenses, after which in the form of drops, which are called reflux or reflux, it flows into the distillation column and moves inside it from top to bottom. The water flow rate for cooling the reflux condenser can be adjusted, thereby changing the amount of reflux flowing back into the column.
In the distillation column there is a counterflow of two phases - steam rises up, reflux falls down. Mass and heat exchange occurs between them, as a result of which the steam is enriched with low-boiling (highly volatile) components of the mixture, and the droplets of the flowing liquid are enriched with high-boiling (hardly volatile) ingredients. Due to this, if the height of the column is sufficient, the target fraction of high purity is removed from its upper part (distillate selection unit). The nozzles in the column serve to intensify mass and heat exchange, since steam condensation occurs precisely on their developed surface. In industrial installations this occurs on trays.
Each plate located in the column is called physical (PT). It is needed so that a state of equilibrium is achieved as quickly as possible between the liquid and vapor phases. Steam bubbles pass through the reflux layer located on the FT. As a result, mass and heat exchange between phases is accelerated. But, after the steam passes through one FT, there will still be no equilibrium, because the efficiency of this element ranges from 50% to 60%. Thus, in order to obtain an equilibrium state of phases that would correspond to one theoretical plate (TP), it is necessary to install two FTs. This means that if, according to calculations, a column of 40 TT is required, then in reality it is necessary to install 80 FT in it.
Rectification plants can be continuous or batch.
In the first, the liquid mixture is constantly fed into the column, and the separated ingredients are also constantly removed from it. Secondly, a certain amount of the mixture is immediately loaded into the cube, after which the device operates until it is completely processed.
In household devices, a drawer is used as a distillation column. This is a pipe with a diameter of 30mm to 50mm, filled throughout its entire volume with nozzles. To prevent the latter from spilling out, wads that are permeable to steam and drops are placed along the edges. The state of phase equilibrium is achieved when the steam passes through a certain layer of the frame, equivalent to one CT. Its height is calculated in millimeters and is called the height of the transfer unit.
The main features of rectification: isolation of the desired ingredient in its pure form and the ability to separate the initial mixture into several components at once. The higher the column, the slower the process, but the purer the final product.
In the alcoholic beverage industry, the difference between distilled and rectified alcohol is explained as follows. Distillate is a raw material in which the organoleptics (taste and smell) of the original product remain. That is, if a grain drink is made, then grains, if an apple drink, then apples, and so on. At the same time, distilled ethyl alcohol still contains many impurities. Some of them form taste and smell. Others can be gotten rid of using various recipes. Rectified alcohol is a refined alcohol. The organoleptic properties of the original product are completely absent. It tastes and smells only of alcohol, and nothing else. At the next stages of the technological process, with the help of flavoring additives and aromas, the desired organoleptic properties are added to it, after which a wide range of liqueurs, tinctures and other things are obtained.
Based on this, we cannot say that one method is better and the other is worse. Everyone has their own purpose. If, for example, brandy is made with the taste and aroma of grapes, then distillation is needed. After rectification, these features will disappear. To obtain a pleasant aroma, distilled alcohol is aged in oak barrels. But for rectified 96% alcohol this is useless; it is only suitable for dilution, for example, in the production of vodka. To this we can also add that equipment for rectification of alcohol is more expensive than for distillation. In addition, distilled mash is required for rectification.
In a mixture consisting of two ingredients (one of which is a liquid as the base of the solution), the concentration of the dissolved substance in the liquid C1 differs from the concentration C2 of it in the vapor of this liquid. Partition (distribution) coefficient
is a characteristic of the process. In some cases, it is more convenient to work with the reciprocal value: A = 1 / B, which is called the same. This parameter depends on the distillation conditions and the nature of the substances that make up the mixture.
Depending on the conditions, coefficient B can be:
Ideal. It is affected only by the partial pressures of the ingredients of the mixture (partial is the pressure of an individual gas included in a mixture of several gases; that is, it is the pressure of one gas that it would have if it occupied the entire volume occupied by the mixture of gases).
Equilibrium. In this case, the number of molecules of gas H evaporating from the liquid is equal to the number of its molecules H1, which return to the liquid in the same time.
Effective.
In practice, distillation is affected by the stirring of the solution and the presence of impurities in it. The presence of the latter may be so significant that the effective coefficient for the separation of the main substance and impurities may differ greatly from the ideal one.
No less important process parameters are the evaporation temperature and the degree of deviation of the system from phase equilibrium between liquid and vapor. During distillation:
Where NS is the number of molecules passing into the condensate. The deviation is quantitatively determined by the ratio: NS / N. In this case, there are two limiting states of the system. If HC = 0, then there is an equilibrium: how many particles left the liquid per unit time, the same number returned to it. If HC = H, then this is molecular distillation, that is, all the particles that evaporated from the liquid turned into condensate. This usually happens if the process is carried out in a vacuum, the vapor pressure is low, and the distance from the surface of the water to the condensation point is minimal. In this case, the vapor particles do not collide either with air molecules or with each other.
The process described at the beginning of the article, in which a liquid is heated and partially evaporated, and its vapors are continuously discharged into the refrigerator and condensed there, is called simple distillation. When working with a multicomponent liquid mixture, fractional distillation or fractional distillation is used. In this case, the ingredients of the mixture are collected into condensate in parts, depending on their volatility, starting with the lowest boiling one.
Rectification is considered by many experts to be a type of distillation. It occurs due to the fact that any closed system consisting of gas and liquid tends to a state of equilibrium. And during rectification, the working (actual) concentration of the ingredients in the vapor phase differs from what should be for this liquid to be in equilibrium.
Distillation and rectification are two methods of separating the components of a liquid mixture, which are based on the same physical process. But different technologies for their implementation allow obtaining completely different results.
