One of the most common methods for separating liquid homogeneous mixtures consisting of two or more components is distillation (distillation and rectification). In a broad sense, distillation is a process that includes partial evaporation of the mixture to be separated and subsequent condensation of the resulting vapors, carried out once or repeatedly. As a result of condensation, a liquid is obtained, the composition of which differs from the composition of the initial mixture.
Rectification is a process of repeated partial evaporation of a liquid and condensation of vapors. The process is carried out by contacting vapor and liquid flows with different temperatures, and is usually carried out in column apparatus. At each contact, a predominantly low-boiling component (LBC) evaporates from the liquid, which enriches the vapors, and a predominantly high-boiling component (HBC) condenses from the vapors, passing into the liquid. Such a two-sided exchange of components, repeated many times, makes it possible, in the end, to obtain pairs that are almost pure FCC. These vapors, after condensation in a separate apparatus, give a distillate (rectified) and phlegm - a liquid returned to irrigate the column and interact with rising vapors. Vapors are obtained by partial evaporation from the bottom of the column of the residue, which is almost pure FCC.
Rectification processes are carried out in apparatuses, the technological scheme of which depends on the purpose of the apparatus and the pressure in it, and the design depends on the method of organizing phase contact.
With the stepwise implementation of the rectification process in column apparatus, the contact of vapor and liquid can occur in countercurrent (on failure type trays), in cross current (on cap trays), in cocurrent (jet trays).
If the rectification process is carried out continuously throughout the entire volume of the column apparatus, then the contact of vapor and liquid during the movement of both phases can occur only in countercurrent. Modern rectifiers can be classified depending on the technological purpose, pressure and internal device that provides contact between vapor and liquid.
According to the technological purpose, distillation apparatuses are divided into columns for atmospheric vacuum installations, thermal and catalytic cracking, secondary distillation of petroleum products, as well as for rectification of gases, stabilization of light oil fractions, etc.
The following requirements are imposed on modern distillation apparatuses: high separation capacity and productive capacity, sufficient reliability and flexibility in operation, low operating costs, light weight and simplicity, technical design.
The latter requirements are no less important than the former, since they not only determine capital costs, but also largely affect the value of operating costs, provide ease and convenience in the manufacture of the apparatus, installation and dismantling, repair, control, testing, as well as the safety of operation and etc.
In addition to the requirements listed above, distillation apparatus must also meet the requirements state standards, departmental standards and inspections of Gostekhnadzor.
Technology system of the apparatus depends on the composition of the mixture being separated, the requirements for the quality of the products obtained, on the possibilities of reducing energy costs, the purpose of the apparatus, its place in the technological chain of the entire installation, and on many other factors.
The process of distillation of liquid mixtures is carried out on distillation plants, consisting of several apparatuses. Consider the principle of separation of a two-component mixture by rectification using the example of the operation of a similar installation (Fig. 10.1). The mixture to be separated is continuously fed into the distillation column through an inlet located slightly above the middle of the column body. The introduced liquid mixture descends through the contact devices (trays) to the lower part of the column, called the cube. Steam rises towards the liquid flow, which is formed as a result of liquid boiling in the bottom of the column. The resulting vapors contain mainly NCC and some VKK. When the vapor interacts with the liquid on the plates of the column, the VKK condenses and is carried away down the column by the liquid flow. Due to this, in the rising pairs, the amount NCC. Thus, when the vapor rises, they are enriched NCC, while the liquid flowing down is enriched WCC.
The initial mixture from the intermediate tank 1 is fed by a centrifugal pump 2 to the heat exchanger 3, where it is heated to the boiling point. The heated mixture is fed to the division in the distillation column 5 on the feed plate, where the composition of the liquid is equal to the composition of the initial mixture. Flowing down the column, the liquid interacts with the ascending vapor, which is formed during the boiling of the bottom liquid in the boiler 4. The initial composition of the vapor is approximately equal to the composition of the bottom residue, i.e., it is depleted in a volatile component. As a result of mass exchange with the liquid, the vapor is enriched with a highly volatile component
Rice. 10.1. Schematic diagram of the distillation plant:
1 - container for the initial mixture; 2, 9 - pumps; 3- heat exchanger - feedstock heater; 4 - boiler; 5 - distillation column; 6 - dephlegmator; 7 – distillate cooler; 8 - container for collecting distillate; 10 – bottom liquid cooler; 11 - container for bottom liquid.
For a more complete enrichment, the upper part of the column is irrigated in accordance with a given reflux ratio with liquid (reflux), which is obtained in the dephlegmator 6 by condensing the steam leaving the column. Part of the condensate is removed from the reflux condenser in the form of a finished separation product - distillate, which is cooled in the heat exchanger 7 and sent to the intermediate tank 8.
From the bottom part of the column, the pump 9 continuously removes the bottom liquid - a product enriched with a non-volatile component, which is cooled in the heat exchanger 10 and sent to the tank 11.
Thus, in the distillation column, a continuous non-equilibrium process of separation of the initial binary mixture into a distillate with a high content of a volatile component and a distillation residue enriched in a non-volatile component is carried out.
The rectification of multicomponent mixtures, which are more common in practice than two-component mixtures, proceeds according to the above scheme, although the number of equipment used in this case increases.
In distillation plants, two types of apparatus are mainly used: columns with stepped phase contact (tray) and continuous contact (film and packed).
Rectification of multicomponent mixtures can be carried out in different sequences, using many simple columns (one less than the number of components of the initial mixture) and using one complex column.
Tray columns are mainly used for the distillation process. They install horizontal plates with devices that provide good contact between liquid and vapor.
The diameter of the column is determined depending on the performance of the installation and the vapor velocity in the column, which is chosen in the range of 0.6 - 1.0 m/s. Distillation columns of various sizes are used: from small columns with a diameter of 300 - 400 mm to high-performance installations, with columns with a diameter of 6, 8, 10, 12 m and more.
The height of the column depends on the number of plates and the distance between them. The smaller the distance between the plates, the lower the column. However, with a decrease in the distance between the plates, the entrainment of splashes increases and there is a danger of transferring liquids from the lower plates to the upper ones, which significantly reduces the efficiency. installation. The distance between the plates is usually taken depending on the diameter of the column, taking into account the possibility of repair and cleaning of the column. The recommended distances between the plates of distillation columns, depending on their diameter, are given below:
column diameter, mm up to 800, 800 - 1600, 1600 - 2000
Distance between plates mm 200 -350, 350 - 400, 400 - 500
column diameter, mm from 2000 - 2400 and over 2400
Distance between plates mm 500 - 600, over 600.
The number of plates of the distillation column or the height of the packing are determined by technological calculation; it depends on the physicochemical properties of the components to be separated, the required separation purity, and efficiency. plates. Typically, distillation columns have 10 - 30 plates, but columns for separating mixtures with close boiling points have hundreds of plates and have a height of up to 30 - 90, respectively. m.
Distillation columns usually operate at atmospheric or slight overpressure. Vacuum columns and columns operating at elevated pressure are of limited use. Vacuum rectification is used when one wants to reduce the temperature in the column, which is necessary when separating components with a high boiling point or substances that are unstable at high temperatures. Rectification under high pressure is used to separate liquefied gases and volatile liquids.
In the distillation column (Figure 2.2), vapors move from below, and a liquid is fed from above towards the vapors, which is an almost pure low-boiling component (phlegm). On each tray, the vapor and liquid columns come into contact. At the same time, from the steam
predominantly the high-boiling component is condensed, and the low-boiling component is predominantly evaporated from the phlegm (Figure 2.3).
As a result, the compositions of the vapor and liquid change, approaching equilibrium. The vapor becomes richer in the low-boiling component and the liquid becomes saturated in the high-boiling component. The steam is condensed in a condenser. Part of this condensate goes in the form of phlegm to irrigate the column, and the other part, the distillate, is taken as a finished product. The liquid leaving the bottom of the column is called the bottoms.
Figure 2.2 - Scheme of a distillation column
Figure 2.3 - Scheme of the interaction of liquid and vapor
Usually a distillation apparatus consists of two parts - upper and lower, each of which is an organized surface of phase contact between vapor and liquid. Initial mixture F is fed into the middle part of the column and as a result of the process is divided into two parts: the part enriched with a low-boiling component (LC) - distillate D, and the part depleted in NK - VAT residue W.
2.3.3 Continuous distillation
When carrying out continuous rectification, the initial mixture is introduced onto a feed plate, which divides the column into two parts (Figure 2.4). In the upper part of the column, the greatest possible strengthening of vapors should be provided, i.e. enriching them with NK so that vapors close in composition to pure NK are sent to the reflux condenser. Therefore, this part of the column is called reinforcing. In the lower part of the column (from the feeder to the bottom plate), it is necessary to remove the low-boiling component from the liquid to a minimum extent, i.e. exhaust the liquid so that a liquid close in composition to the pure high-boiling component flows into the boiler. Accordingly, this part of the column is called exhaustive.
1 - distillation column (1a - strengthening part, 1b - exhaustive part); 2 - boiler; 3 - dephlegmator; 4 - reflux divider; 5 – initial mixture heater; 6 - distillate refrigerator (or refrigerator-condenser); 7 - refrigerator of the residue (or bottom product); 8.9 - collections; 10 - pumps
Figure 2.4 - Scheme of a distillation unit of continuous operation
Steam for feeding the distillation column is formed in the cube by evaporating part of the liquid entering the cube; liquid for irrigation apparatus W (phlegm) is obtained in the reflux condenser by condensing steam, which has a composition similar to that of the distillate.
The heat required to evaporate the mixture is reported to it in the cube. In the reflux condenser, heat is removed, as a result of which the vapors entering it are completely or partially condensed.
Material balance equations for a continuous distillation column:
,
(2.1)
,
(2.2)
where F, D, W - mass or molar flow rates of food, distillate and distillation residue;
– content of the low-boiling component in the feed, distillate and distillate residue, mass or mole fractions.
Working line equations:
a) the upper (strengthening) part of the distillation column
,
(2.3)
b) the lower (exhaustive) part of the column
,
(2.4)
where y and x are non-equilibrium concentrations variable along the height of the column, mole fractions of the volatile component in the vapor and in the liquid in a given section of the column;
R= F/ D– reflux number;
– relative (per 1 kmol of distillate) molar consumption of food.
In a distillation column, in contrast to an absorption column, on the basis of theoretical assumptions, the total molar flow rates of vapor and liquid are assumed to be constant along the height of the column, in accordance with this, in equations (2.3) and (2.4), molar flow rates and concentrations are used. In the upper part of the column, above the input of the initial liquid mixture, the molar flow rate of the liquid, constant along the height of the column, is equal to 
, at the bottom of the column it is equal to . The height-constant molar flow rate of steam is the same in the upper and lower parts of the column.
The principle of the rectification process.
The device of distillation columns.
Causes of damage to distillation columns and measures to prevent them.
Fire hazard of distillation plants. Fire prevention measures.
Question 1. The principle of rectification
The processes of distillation of solutions, in other words, the separation of solutions into their constituent components, are very common in modern technology.
For example, the separation of natural petroleum hydrocarbons in order to obtain motor fuels and lubricating oils.
Separation of individual gases from their mixtures occurs by their preliminary liquefaction with subsequent distillation of the liquid mixture.
The vast majority of flammable liquids and liquid liquids (alcohol, acetone, acetic acid, benzene and its homologues, gasoline, kerosene and many other products) are also obtained using distillation processes.
Distinguish between simple distillation and rectification.
Simple distillation is the process of partial evaporation of a solution and complete condensation of the resulting vapors.
Rectification, on the other hand, is the process of separating liquid homogeneous mixtures into their constituent components as a result of repeated countercurrent interaction of vapor with liquid.
According to According to Konovalov's first law, the vapor is enriched with that component, the addition of which to the liquid increases the vapor pressure above it or lowers the boiling point.
Ideal mixtures obey Raoult's law, according to which the partial pressure of a component in a system is equal to the vapor pressure of a pure component multiplied by its mole fraction in solution:P partz =P pair m
And according to Dalton's law, the partial pressure of a component in a gas mixture is equal to the total pressure multiplied by the mole fraction of this component in the mixture:P partz =P common m
Schematically, the rectification process can be represented as follows.
Where m 1 , m 2 , m 3 - the amount of the mixture received for rectification, the resulting distillate and the remaining residue;
X 1 , X 2 , X 3 is the content (mole fraction) of the volatile component in them, respectively.
Question 2. The device of distillation plants
So, rectification is the process of separating liquid homogeneous mixtures into their constituent components as a result of repeated countercurrent interaction of vapor with liquid.
Rectification processes are carried out in distillation plants.
Distillation columns are classified:
by design: dish-shaped; packed.
depending on working pressure: working under vacuum; working at atmospheric pressure; working under pressure.
Cymbals Distinguish : valve; jet; sieve; cap.
Let's take a look at how the rectification process is carried out.
In the middle of the column the raw material subject to rectification arrives heated to a certain temperature.
The feed may be supplied to the column as a liquid, vapor, or a mixture of vapor and liquid.
When raw materials enter the column, a single evaporation process occurs, as a result of which vapors and a liquid of a certain composition are formed, which are in equilibrium.
To ensure rectification, it is necessary to the top of the column towards the vapors to organize the flow of liquid (phlegm, irrigation). To do this, heat is removed at the top of the column in one way or another (heat of the partial condenser). Due to this, part of the vapor rising from the upper plate is condensed, forming the necessary downward flow of liquid.
Phlegm number is the ratio of the amount of distillate (phlegm) returned to the column to the amount of distillate withdrawn as a product.
A schematic diagram of a distillation column is shown in the figure.
Receipt of raw materials
The flow of phlegm
Vapor outlet to dephlegmator
boiler
Yield of VAT residue
An ascending vapor flow must be provided at the bottom of the column. To do this, heat is supplied to the bottom of the column in one way or another (heat of the boiler). In this case, part of the liquid flowing down from the lower plate evaporates, forming a vapor stream.
In this mode: the lowest temperature will be at the top of the column and the highest at the bottom of the column.
The product taken from the top of the column, enriched with a low-boiling component, is called rectified (or distillate). And from the bottom of the column, the sampled product, enriched with a high-boiling component, is called residue or bottom (bottom) product.
The part of the column where the raw material is introduced is called feeding section or evaporative space. Part of the distillation column located above the input of raw materials - upper, concentration or firming, and below the input of raw materials - lower, distant or exhaustive .
The same distillation process takes place in both parts of the column.
This figure shows a diagram of a simple (I) and complex (II) columns:
a - complete; b- strengthening; in - distillate; G - with the selection of additional products from above and below from the main column; d - with the selection of additional product from the top of the stripping column.
I wonder if every lover alcoholic products wondering what a reconciliation is? But this process is directly related to these drinks. Many novice moonshiners often confuse it with secondary distillation, which is not true. In reality, liquids are run through several times using special equipment, resulting in pure alcohol. There is a slightly similar process called distillation.
In our modern age, propaganda is actively carried out healthy lifestyle life, however, it has always been so, but recently it has become more obvious. We are constantly urged to give up alcoholic products, and to completely eliminate them from our diet. But since humanity has been using alcohol since the first days of its appearance, it is unlikely that it will be possible to completely abandon it. And we are talking not only about wine, vodka and other drinks obtained by distillation. But what is rectification? More on that below.
Features of alcohol
From Latin, alcohol (spiritus) is translated as spirit and is an organic compound, which is represented by a variety of compounds. The most common of them are:
- ethyl;
- methyl;
- phenylethyl.
Some species are obtained not only in laboratory conditions, they can also be found in nature. For example, in plant leaves it is methyl alcohol, fermented organic products contain ethanol. Some types of vitamins can also be attributed to the class of alcohols: A, B8 and D.
Under normal physical conditions, alcohol is a clear liquid with a sharp, characteristic odor and taste. It is able to dissolve oily and fat-containing substances. As for its main characteristic, strength, it is 95.57-100%.
Before answering the question of what rectification is, it is worth clarifying whether or not alcohol has any beneficial features? Without a doubt, they exist, and there are plenty of them. And first of all, it is an antiseptic and deodorizing agent, which is used to disinfect medical instruments, the surface of the skin, as well as to treat the hands of medical personnel before performing operations. In the ventilator, alcohol acts as a defoamer. It is used as a solvent for the production of medicines.
But, in addition to medicine, alcohol is also good in the production of alcoholic products - it increases the degree of drinks. AT living conditions a strong liquid is often used to lower the temperature by rubbing. With it, you can prepare healing tinctures or make a warm compress.
Enumerate all the useful properties and qualities of alcohol can be infinitely long. But back to our topic, what is rectification.
What is this process
The word rectification comes from the fusion of two Latin words:
- rectus - straight;
- facio - do.
In fact, this is a special kind of process that is used to separate liquid mixtures into its individual components, depending on the boiling point (each one has its own). In simple terms, decomposition into different fractions (heavy and light) occurs.
It only happens when the flow of liquids and steam come into contact. It is thanks to this process that you can get the purest and strongest alcohol.
Often the production of alcoholic beverages is not complete without two important processes, such as:
- rectification;
- distillation.
We have dealt with the first, but what is the second process? Many people confuse these two terms, believing that they are practically the same thing. In fact, there are significant differences between the rectification of alcohol (or any other mixture) and distillation, which we will touch on a little later.
A slightly similar process is distillation
So, this definition refers to the process of extracting a liquid component by boiling any mixture, where it is present, and cooling its vapors in order to form condensate and collect. This method successfully used for desalination of mixtures. This makes it possible not only to separate the liquid components present, but also to separate the solids from the liquid solvent.
In addition, distillation is excellent for obtaining drinking water from a sea source. Also, many lovers of homemade alcohol produce drinks in this way at home.
The listed processes (distillation and rectification of mixtures) are used not only in the laboratory, pharmaceuticals or at home. They are also widely used in industry, where they are used to separate oil into different components:
- petrol;
- kerosene;
- diesel fuel;
- jet fuel;
- fuel oil
In addition to liquid products, solids such as bitumen, tar, and asphalt can be obtained from oil.
Distinctive features
Distillation is considered a simple process (distillation): fermented raw materials (for example, wine) are placed in a special cube, and it is heated to the boiling point. In this case, vapors are released, which are sent to the cooler, where they are collected in the form of condensate in a container. The resulting product is raw alcohol. Its strength is from 40 to 50 degrees. However, it is still contaminated with impurities, so it needs to be cleaned and further refined.
In most cases, this distillate is re-distilled, which increases its strength. But if you want to get strong and pure alcohol, you should choose another method. At first glance, it seems that there is no difference between distillation and rectification. In reality, this is far from the case.
A high degree of purification can only be achieved using special equipment called a distillation column. Its device includes a drawer, a dephlegmator nozzle and a cooler. The released steam from the heated raw material enters the pipe and contacts with the liquid phlegm inside its walls. In this case, some of the steam in the form of condensate settles in the dephlegmator, and the rest returns to the drawer.
Thus, the process of rectification takes place. At the same time, the source material is maximally purified from harmful impurities (suspensions, fusel oils, etc.). The resulting rectified alcohol has the highest possible strength - up to 96%. Such a product is completely ready for technical, medical purposes.
As you can see, the differences concern not only the distillation technique, but also the quality of the product itself.
Alcohol
For the rectification of alcohol, mixtures that contain it are used as the main source - they are driven through special columns. As a result of heating, the solutions are separated into two components:
- Liquid.
The output is the purest alcohol. People have learned to produce alcoholic products since ancient times. Fermented berries and fruits were used as raw materials. Only in the resulting product was a negligible amount of alcohol. The situation improved with the development of the chemical industry. And there was a whole direction aimed at increasing the degree of alcoholic beverages.
Completely pure 100% alcohol was obtained only at the end of the 18th century. This was done by the Russian chemist Johann Tobias (Toviy Egorovich) Lovitz. It is he who can be deservedly considered the creator of the rectification process.
Oil
The main purpose of oil rectification is to obtain light fractions from oil, which are:
- Petrol.
- Kerosene.
- Gasoil.
Petrol is a combination of petrenes, alkanes and aromatic hydrocarbons. The temperature reaches +150...+205 °C. It all depends on what kind of transport you need to get fuel for - cars, aircraft or other equipment.
Kerosene It is a common type of fuel for powering tractors and other types of agricultural vehicles. In addition, it serves as a component for diesel fuel. In addition, some lighting systems also work on it. The heating temperature is selected based on the purpose of the appointment, and can be +150...+180 °C or +270...+280 °C.
Concerning gas oil, then this distillate is mainly used for the production of diesel fuel. The process temperature depends on the required qualities of the final product and ranges from +270...+280 to +320...+350 degrees.
Also, as a result of the rectification of oil, solid fractions are obtained, which include:
- Fuel oil.
- Tar.
fuel oil good as boiler fuel or may be further processed. For example, it is distilled under reduced pressure, bringing it to a vacuum. In this way, various oils are obtained. In addition, it is used for cracking, the purpose of which is to obtain high-octane gasoline. The temperature for fuel oil is from +230 to +350 degrees.
After the oils are separated from the fuel oil, an almost solid substance is obtained - tar. In turn, bitumen can be obtained from it, which is a component of asphalt. In addition, tar is valuable for the metallurgical industry, where coke is obtained from it.
Characteristic features of the rectification process
Understanding the distillation process can be useful for lovers of alcoholic products of any strength.
And knowing how it differs from distillation, you can choose the right equipment for your needs, even with automatic distillation for the production of the necessary drinks. For example, if you need to get a product based on grape or any other fruit juice with pomace, then a classic distiller is enough. If you need to get alcohol with a high degree, then you can’t do without a distillation column.
Fortunately, some universal type moonshine stills have an atmospheric fitting. Now it is only necessary to install an additional drawer, as the equipment will be upgraded to a distillation column. Such devices are more preferable, especially for all those who prefer to experiment and develop their skills.
However, the rectification process would not be so popular with most moonshiners if it did not have its own tricks. One of them is the use of ready-made distillate as an alternative to Braga. This way you can avoid unnecessary hassle. The fact is that the use of mash is accompanied by the release of foam, and in large quantities, which cannot be said about the distillate. In this connection, by distilling raw alcohol, it is possible to protect the distillation column from damage.
Another feature is that, than more height column, the more intense will be the mass and heat exchange of two counter flows, and the better the final product will be. That is, the values \u200b\u200bare proportional: the higher the tsarga, the higher the quality of the alcohol.
Dephlegmator, refrigerator-condenser, heater - conventional heat exchangers, the main device of all equipment is a distillation column. It is in it that the vapors of the distilled mixture rise, and the liquid (phlegm) flows towards them, which is fed into its upper part.
The classic column looks like this: a long pipe is placed on the evaporation cube (the higher, the better), which is called a tsarga, as well as a dephlegmator with a trailer. There are no complicated mechanisms here, only a tap for selection, a viewing glass and a thermometer. In some cases, there may be a power regulator.
Column work
The whole procedure is carried out in several stages:
- The mash or any other alcohol-containing solution is heated to the desired rectification temperature.
- The resulting vapors enter the column and then fall into the refrigerator.
- At the top, the vapors condense into a liquid state and move in the opposite direction already in the form of a liquid (phlegm).
- The condensate flows down, vapor rises towards it, and in the process of such mixing, they are saturated with alcohol from phlegm.
Such a cycle occurs many times, and as a result, the vapors are saturated with alcohol so much that the strength of the condensate reaches 93% or a little more. As for impurities, they are less volatile and settle in the column. For this reason, it is preferable to use high pipes, and the longer they are, the better the final product is.
After using a distillation column, there is no need to carry out additional purification of the resulting drinks. In addition, along with impurities, the product gets rid of an unpleasant odor and unwanted taste.
As for the use of mash, it is better to do without it if possible, as mentioned above. The process must run at a stable temperature, and a thermally insulated column avoids temperature fluctuations.
Atmosphere pressure
The operation of the moonshine still depends on atmospheric pressure, and many models are equipped with a special fitting. When it is closed, the apparatus functions in distillation mode, but once it is opened, this is already a rectification method.
After the raw material is heated to the desired boiling point, the selection nozzle is closed. The unit has been operating offline for some time. At this point, the alcohol vapor circulates inside the column, increasing the reflux ratio and removing impurities. Then the fitting opens, and a procedure takes place during which the pressure and temperature of rectification are kept at high level. To avoid overheating of the equipment, the atmospheric valve is open during the entire rectification. This regulates the pressure.
Since the nozzle is constantly open, atmospheric pressure has its effect on the rectification process taking place in the column. With its decrease, the density of alcohol vapors decreases, which leads to an increase in their consumption and speed of passage in the installation. Exceeding the allowable value results in flooding of the column.
And if the pressure increases, then the vapor velocity will decrease, which slows down the division into fractions. This can be corrected by temporarily closing the fitting.
Do not lose sight of the pressure in the column. In a dephlegmator, it is always equal to the atmospheric value due to the open fitting. Directly in the tsarga, it is due to the movement of vapors and their interaction with phlegm. In this case, the value of the pressure drop should not exceed the maximum values that are set by the manufacturers. In order to be able to control this value, the columns are equipped with special manometric tubes.
Many companies that produce modern distillation plants are trying to stabilize the operation of the equipment so that it does not depend on external factors. Unfortunately, this shortcoming has not yet been completely avoided. In this connection, the instructions directly state that rectification should not be carried out on days when a decrease in atmospheric pressure is likely.
Automated process
During the rectification process, personal presence and constant monitoring of everything that happens is necessary. However, you can also act wisely - use automation. Such devices are designed to automate the entire procedure and without the direct participation of a person.
High-quality devices will select the so-called heads in a separate container and exclude the ingress of tails into the finished product. The control unit will release water for cooling at the right time, reduce power during the selection. After the tailings are collected, the water supply and heating will be turned off.
As you can understand, automation for rectification is a necessary thing, especially when urgent matters arise, the solution of which cannot be postponed to another time.
In the modern world, methods are often used to extract individual elements from multicomponent mixtures, which can later be used for industrial and many other purposes. The rectification process is one of the most efficient. Many use it for the production of alcoholic beverages at home.
Rectification is a procedure for separating mixtures of a multicomponent type into individual elements. The separation is carried out due to the fact that a countercurrent exchange of mass and heat appears between the vapor and liquid. The rectification process can be carried out continuously and from time to time.
In order to be able to carry out rectification, it is necessary to have specialized equipment. It can be represented by a distillation column. It is an equipment that is very often used in industry and at home in the manufacture of highly purified alcohol for the production of alcoholic beverages or medical preparations. Also, with the help of distillation columns, you can get gasoline and other types of fuel.
A distillation column is a vertical type vessel with a constant or variable cross section. Inside this cylinder there are special auxiliary units and devices for the exchange of mass and temperature in order to be able to separate multicomponent liquids into separate fractions for their subsequent use. In the column, all separated components have a temperature close to the boiling point.
The most common column for carrying out the distillation process is a cylindrical vessel, which has built-in contact devices. They are represented by various plates and nozzles. It also has auxiliary nodes, the activity of which is aimed at leading or distributing liquid and vapor inside the vessel in the right way, so that a quality product is obtained at the output.
In the modern world, rectification is used various kinds multicomponent liquids to isolate from them the elements necessary for further use. Rectification of alcohol is quite common.
This process consists of several stages:
- First of all, it is necessary to bring to a boil the liquid, which, along with other substances, contains alcohol.
- After that, the vapors of the heated liquid rise up the column. They accumulate in the dephlegmator.
- After that, the dephlegmator is cooled down.
- After the cooling process, condensate forms on the surface of the reflux condenser.
- Drops of condensate flow down the column.
- At the bottom of the column, all drops of condensate accumulate in a special nozzle.
- The nozzle lifts them back up.
- As a result, liquid accumulates in the upper part of the column, which is easily subjected to boiling. Part of it accumulates in the condenser, and the other part enters the receiving tank.
In the modern world, oil rectification is used to obtain certain types of fuel. This process consumes a lot of time and energy. As a result, it is possible to get gasoline or gas at the output. This process is also carried out in distillation columns, which are larger than household ones. Their principle of operation is similar. The stages of oil rectification are the same as in the rectification of sprit-containing liquids. Only at the output are formed certain types fuel.
Rectification of benzene has found wide application at coke production enterprises.
In this case, substances such as:
- pure benzene,
- tluene,
- xylene.
In the modern world, there are three types of rectification.
They are represented by the following types:
Simple rectification.
This procedure is typical for cases where a tray distillation column is used. As a result of thermal and mass exchange of vapors, a purified liquid of the desired type is obtained at the outlet.
Steam circular rectification.
This fork is based on the use of distillation columns, which operate on the principle of circulating water vapor. In this case, impurities are distributed differently between the liquid substrate and vapors.
This type of rectification is suitable for isolating the desired element from raw materials that contain a minimum amount of non-aromatic hydrocarbons.
All these methods are aimed at isolating certain substances from liquids consisting of many components that are necessary for further use. Their choice depends on the type of distillation column and on the raw material that needs to be divided into fractions and the desired substance is isolated.
Table 1. Boiling point of a water-alcohol mixture.
| Boiling point of the mixture (0 C) | Alcohol content mixed (0) | Alcohol content in pairs (0) |
|---|---|---|
| 100 | 0 | 0 |
| 98,75 | 1 | 13 |
| 97,50 | 2 | 28 |
| 95 | 5 | 42 |
| 93,75 | 7 | 50 |
| 92,50 | 10 | 55 |
| 91,25 | 12 | 61 |
| 90 | 15 | 66 |
| 88,75 | 18 | 68 |
| 87,50 | 20 | 71 |
| 85 | 30 | 78 |
| 83,75 | 40 | 82 |
Table 2. The yield of alcohol and vodka from one kilogram of raw materials.
| Type of raw material | Yield spiritaliter/kg | Vodka yield 40 0 liter/kg |
|---|---|---|
| Potato | 0,11-0,18 | 0,35 |
| Rye | 0,4-0,43 | 0,88 |
| Wheat | 0,433 | 0,92 |
| Rice | 0,587 | 1,247 |
| oats | 0,358 | 0,895 |
| Peas | 0,408 | 0,767 |
| Millet | 0,413 | 0,876 |
| Starch | 0,716 | 1,521 |
| acorns | 0,25 | 0,558 |
| Beet | 0,082-0,12 | 0,212 |
| Grape | 0,09-0,14 | 0,247 |
| Apples | 0,064 | 0,138 |
| Pears | 0,052-0,10 | 0,165 |
| Barley | 0,344 | 0,724 |
| Buckwheat | 0,473 | 1,004 |
| Cherry | 0,045-0,06 | 0,121 |
| Sugar | 0,511 | 1,080 |
| Chestnut | 0,258 | 0,572 |
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