Distillation column (fractionation column)- cylindrical vertical apparatus, equipped with internal heat and mass transfer devices and auxiliary units, designed for the separation of two-component or multi-component liquid mixtures into fractions, each of which contains substances with similar boiling points.

Distillation columns are divided into:

by the number of products received:

Simple distillation columns ensure the separation of the initial mixture (raw materials) into two products: rectificate (distillate), removed from the top of the column in a vapor state, and the residue (lower liquid rectification product)

Complex Distillation columns separate raw materials into more than two products. There are complex columns with the selection of additional fractions from the column in the form of side straps and columns in which additional products are selected from special stripping columns (stripping).

by purpose:

1) for atmospheric and vacuum distillation of oil and fuel oil

2) for secondary distillation of gasoline

3) for stabilization of oil, gas condensates, unstable gasolines

4) for fractionation of refinery refineries, oils and natural gases

5) for distilling off solvents in oil purification processes

6) for separation of tube furnace products and catalytic processes for processing petroleum feedstock and gases, etc.

by pressure value:

these are columns in the upper part of which the pressure is slightly higher than atmospheric (0.1...0.2 MPa). The pressure at the bottom of the column, as a rule, depends on its resistance internal devices and can significantly exceed atmospheric. Such columns are used for the distillation of stabilized or stripped oil into fuel fractions and fuel oil.

work under vacuum (or deep vacuum). In other words, the pressure in them is lower than atmospheric (a vacuum is created), which makes it possible to reduce operating temperature process and avoid product decomposition. Such columns are intended for fractionating fuel oil into vacuum (deep vacuum) gas oil or narrow oil fractions and tar.

are used in the stabilization or topping of oil, stabilization of gas gasolines, petroleum distillation gasolines and secondary processes, and fractionation of refinery or associated petroleum gases.

according to the operating principle:

are used in low-capacity installations when it is necessary to select a large number of fractions and have high separation clarity. The feedstock is poured into the cube to a height equal to 2/3 of its diameter. Heating is carried out with silent steam. During the first period of operation of the distillation unit, the most volatile component of the mixture is selected, for example, benzene head, then components with more high temperature boiling (benzene, toluene, etc.). The highest boiling components of the mixture remain in the cube, forming a bottom residue. At the end of the rectification process, this residue is cooled and pumped out. The cube is again filled with raw materials and rectification is resumed. The periodicity of the process results in greater heat consumption, lower labor productivity and less efficient use equipment.

Installations with continuous columns do not have the disadvantages of periodic columns. In such columns, heated raw materials are introduced into distillation column, where it is divided into liquid and vapor phases. As a result of rectification, isopentane is selected from the top of the column as the main product and n-pentane as the residue from the bottom of the column.

according to the method of interstage fluid transfer:

1) with transfer devices (with one, two or more)

2) without transfer devices (failure type)

according to the method of organizing contact between the vapor-gas and liquid phases:

These columns are used, for example, for the separation of heavy water. The plates are conical shields with an inclination angle of 40°. Fixed plates 4 are attached at the periphery to the body of the column 1, movable plates 3 are attached in the center to the shaft 5 and rotate with it. Rotating plates alternate with stationary ones. Every 1.5 m in height, the shaft is covered by ball bearings 6 operating without lubrication. For ease of installation, the column is assembled from frames (parts / on flanges). The phlegm descends from above along the stationary plate 4 and at the center overflows onto the underlying rotating plate 3. Under the influence of centrifugal force, the phlegm moves along the rotating plate up to its periphery and, in the form of a continuous annular film, overflows onto the stationary plate. The vapors move countercurrently over the phlegm.

In packed columns, contact between gas (steam) and liquid occurs on the surface of special packed bodies, as well as in free space between them.

Nozzle - body made of inert materials, it is designed to create a larger contact surface between the liquid flowing down it and the rising flow of vapors and intensively mix them. The nozzle is usually made of corrosion-resistant material (ceramics, porcelain, glass).

The nozzle is placed on plates equipped with two openings of two types: small - for the drainage of irrigation (reflux) and large - for the passage of vapors. The nozzle layer is divided into several small layers 1-1.5 m high, separating them with free space.

The smaller the packed rings, the better the contact between vapor and reflux, but the higher the hydraulic resistance to the movement of vapor in the column. At a certain limit value of the load of the packed column, i.e., at high speed vapors or liquids, may be observed “choking” of the nozzle, when the flow of liquid stops and its ejection from the column begins. The main disadvantage of packed columns is the formation of “dead” zones in the packing, through which neither vapors nor reflux pass, which worsens the contact between mass-exchange phases and reduces the separation efficiency.

The designs of nozzles used in industrial equipment for oil and gas refining and petrochemistry can be divided into two groups - irregular (bulk) and regular nozzles.

Used as irregular (bulk) nozzles solids various shapes, loaded into the body in bulk. As a result, a complex spatial structure is formed in the column, providing a significant phase contact surface.

Among the nozzles poured into bulk, Raschig rings, which are sections of pipes whose height is equal to the outer diameter, are widely used. The low cost and ease of manufacturing of Raschig rings make them one of the most common types of attachments. Along with smooth cylindrical rings made of metal, ceramics or porcelain, nozzles with ribbed outer and (or) inner surfaces have been developed. To intensify the mass transfer process, designs of cylindrical nozzles with partitions have been developed.


Nozzle from Raschig rings (1 - separate ring; 2 - rings in bulk; 3 - regular nozzle)

Another ring attachment, the Pall rings, has now found industrial use. When making such rings, two rows of rectangular cuts are made on the side walls, offset relative to each other, the petals of which are bent inside the nozzle. The design of Pall rings compared to Raschig rings makes it possible to increase throughput and reduce hydraulic resistance.

The saddle known as Intallox saddles is the most common ceramic saddle today. Its surface is part of a torus. Intallox saddles have mechanical strength, ensure uniform placement of the nozzle and good self-distribution of the liquid.

IN dish columns contact between phases occurs when steam (gas) passes through a layer of liquid located on a contact device (plate).

Distillation column plate It is a horizontal partition in a column; on a plate there is a layer of liquid flowing down the column (irrigation), through which vapors rising from below bubble.

In the book Skoblo A.I., Molokanov Yu.K., Vladimirov A.I., Shchelkunov V.A. “Processes and Apparatuses of Oil and Gas Refining and Petrochemicals” column apparatuses are divided into disc, packed and film devices based on the type of internal contact devices (the authors of this publication include film devices in which the phases are in contact on the surface of a thin film of liquid flowing down a vertical or inclined surface).

The invention relates to mass transfer equipment in the field of processing hydrocarbon raw materials, chemical and food products, in particular to devices for rectification, absorption of petroleum products, chemical and food products by separating products by boiling points in the process of mass and heat exchange between liquid and steam (gas), and can find application in the oil refining, chemical, petrochemical, gas, food industries . The rectification column includes a housing with process fittings, trays with steam and overflow pipes, as well as height-adjustable bubble caps. The upper end of each overflow pipe is fixed in a plate with the possibility of axial movement of the pipe relative to the latter, and its lower end is equipped with a plate-shaped perforated disk, as well as a glass concentric to the overflow pipe and forming a water seal with it. Technical result: improving the quality and productivity of the column for target products, increasing the efficiency of the distillation column. 2 ill.

The invention relates to mass transfer equipment in the field of processing of hydrocarbon raw materials, chemical and food products, in particular to devices for rectification, absorption of petroleum products, chemical and food products by separating them by boiling point in the process of mass transfer between liquid and steam, and can find application in oil refining , chemical, petrochemical, gas, food industries.

Known distillation column for separating a three-component mixture (patent 2234356), containing a vertical body with plates and a longitudinal vertical partition intersecting part of the plates and dividing the column body into vertical sectors. The column contains a reflux flow regulator and a vapor phase flow regulator.

A columnar apparatus with cap plates is known (patent 2214852). In that column apparatus with cap plates, the body is made of drawers; support rings are sandwiched between their bases, on which plates with elastic seals rest. Central supports equipped with locks. The base of the plate is dome-shaped. All column elements are made of fluoroplastic and are designed for processing corrosive materials.

The disadvantage of both of these columns is that, due to the rigid fastening of all elements of the cap plate, it is not possible to change such technological parameters as, for example, the thickness of the liquid layer on the plate and the difference in liquid levels under the caps relative to its level on the plate, which does not allows you to change the operating mode of the column in height depending on the changing properties of the processed products, i.e. influence the process of heat and mass transfer in the column.

A distillation column with cap plates is also known, for example, described in the book “Processes and Apparatuses”, D.A. Baranov, A.M. Kutepov, M., Academy, 2005, pp. 182, 183, in which the disadvantage of the above-mentioned columns according to patents is partially eliminated, so at least the caps are fixed with the ability to adjust their position in height.

The specified distillation column with cap-shaped plates, as the closest in technical essence to the proposed device, was adopted as a prototype.

However, the prototype is not without the disadvantages characteristic of known columns, namely, there is no possibility of adjusting the thickness of the liquid layer on the plate, and there is also no possibility of developing the interphase contact surface, which largely determines the efficiency of the heat and mass transfer process, i.e. efficiency of the column as a whole.

The purpose of the present invention is to eliminate the listed disadvantages and increase the efficiency of the column.

Essentially, the problem is solved due to the fact that the upper end of each overflow pipe is fixed in a plate with the possibility of axial movement of the pipe relative to the latter, and its lower end is equipped with a plate-shaped perforated disk, as well as a glass concentric to the overflow pipe and forming a water seal with it.

As a result of this technical solution the vapor-liquid mixture passes the steam pipe and cap, bubbling through the cracks of the cap and contacting the liquid on the plate. The vapor-gas mixture goes to the overlying plate, and the excess liquid (heavy) fraction is drained through the overflow pipe into the water seal glass, from where it ends up on a perforated plate disk. Some of the liquid flows over the side of the disk, forming an annular film. The other part of the liquid in the form of drops and streams passes through the perforations in the disk and drains onto the underlying plate. The easily evaporating liquid, located on the plate in a film, drops, streams, evaporates and passes through the steam pipes to the overlying plate. Taking into account the change in temperature, viscosity of the liquid, composition and state of aggregation of the medium along the height of the column, it is possible to adjust the ratio and height (gaps) between the steam pipes and caps, between the overflow pipes and the glasses of water seals with disc disks, and also use the overflow pipes to change the height (and , respectively, the resistance to bubbling) of liquid on the plate and the open cross-section for bubbling of vapors through the slots of the caps.

This allows you to optimize the process of dividing the processed product into specified fractions.

Figure 1 schematically shows a longitudinal section of the column.

Figure 2 is view A, which shows on an enlarged scale trays with steam and overflow pipes, brackets with clamps and adjusting pins, steam caps, and water seals with disc discs.

The proposed distillation column consists of a housing 1, fitting 2 for the inlet of the vapor-liquid mixture, fitting 3 for the liquid outlet (heavy fraction) and fitting 4 for the vapor outlet (light fraction). In addition, the column contains plates 5 with steam pipes 6 and overflow pipes 7, as well as caps 8 and water seal cups 9, brackets 10 with clamps 11, pins 12, transverse strips 13 and perforated disks 14.

The proposed column works as follows. The initial vapor-liquid mixture is fed into the column through fitting 2. Vapors through steam pipes 6 enter the cavity of the caps 8, displace liquid from them through the slots of the caps 8, after which the steam mixture begins to bubble into the liquid layer outside the caps 8, and a lighter vapor-gas mixture enters onto the plate above. The heavy fraction condenses in this liquid on a plate, through overflow pipes 7 enters the water seal glass 9, overflows over the edges of the glass 9 and falls onto the perforated discs 14. The liquid then drains from these discs through the sides of the discs in the form of a film, as well as through the perforations of the discs in the form of drops and streams.

Equipping the lower ends of the overflow pipes 7 with disc-shaped overflow disks 14 provided a significant increase in the surface due to the outflow of liquid from these disks in the form of a film, drops and jets, which in turn increased the efficiency of the heat and mass exchange process in the column as a whole.

In case of clogging of steam caps and overflow pipes, it is possible to dismantle them and clean them from contaminants and then install them through hatches in the column body, which significantly reduces the time and labor costs for cleaning and Maintenance columns.

Thus, changing the height of the overflow pipe (and the liquid layer) on the plate, in combination with a perforated disc on the overflow pipe, made it possible to optimize the liquid level on the plate and significantly increase the interfacial contact surface on each plate, the total height of the liquid column (resistance) in the column , operating mode of the column in height, heat and mass transfer surface depending on the changing properties of the processed products (boiling point, liquid viscosity, mixture composition).

This makes it possible to separate products into clearer fractions and, accordingly, improve the quality of the target products. The advantages outlined above lead to a significant increase in the efficiency of the column.

A rectification column, including a housing with process fittings, trays with steam and overflow pipes, as well as height-adjustable bubble caps, characterized in that the upper end of each overflow pipe is fixed in a plate with the possibility of axial movement of the pipe relative to the latter, and its lower end is equipped with a disc-shaped a perforated disk, as well as a glass concentric with the overflow pipe and forming a water seal with it.

Similar patents:

The invention relates to the design of contact devices for absorption plates, rectification and other heat and mass transfer devices equipped with overflow devices, and can be used in the chemical, gas, petrochemical, food, energy, mining and related industries.

The invention relates to mass transfer equipment in the field of processing hydrocarbon raw materials, chemical and food products, in particular to devices for rectification, absorption of petroleum products, chemical and food products by separating products by boiling point in the process of mass transfer between liquid and steam (gas), and can find Application in oil refining, chemical, petrochemical, gas, food industries. The rectification column includes a housing with process fittings, trays with steam pipes and overflow devices, as well as caps with vertical slots. The horizontal edges of the cap slots are equipped with blades located with outside caps radially and horizontally. The technical result is to increase the efficiency of the mass transfer process in the distillation column as a whole. 3 ill.

The invention relates to an improved method for producing para-tert-butylphenol by alkylation of phenol with isobutylene on a heterogeneous sulfonic cation exchange catalyst, separation of the reaction mass containing phenol, para-tert-butylphenol, ortho-tert-butylphenol, 2,4-di-tert-butylphenol, high-boiling impurities, by vacuum rectification in two columns with the selection of phenol and ortho-tert-butylphenol in the form of a distillate. In this case, the reaction mass is subjected to rotary film evaporation to separate high-boiling impurities from it, the commercial product is isolated in an additional distillation column in the form of a distillate, vacuum line absorption capture of non-condensed vapors of para-tert-butylphenol is carried out, the bottoms of the column for separating the commercial product, containing 2,4-di-tert-butylphenol and para-tert-butylphenol, are recycled to the stage of alkylation of phenol with isobutylene. The invention also relates to a device for implementing a method for producing para-tert-butylphenol. The method makes it possible to obtain a product with high degree purity and high yield. 2 n.p. f-ly, 1 ill.

The invention relates to the field of radionuclide technology and can be used both in technological processes, using molecular tritium and tritium-containing compounds, and for deep cleaning gas discharges from tritium from nuclear industry enterprises when solving environmental problems. The method for purifying gases from tritiated water vapor is that the gas flow is supplied from below a countercurrent phase isotope exchange column filled with a spirally prismatic nozzle made of of stainless steel, and a flow is supplied from above the column natural water, and the process is carried out at room temperature, and the height of the column is selected based on the required degree of gas detritiation. The technical result of the invention is to increase the degree of purification and switch to a continuous mode of the gas detritiation process. 2 ill., 1 tab., 2 ex.

The invention relates to a device for carrying out thermodestructive processes for processing heavy oil residues, which can be used in the oil refining, petrochemical and gas industries. The device, which is a reaction-distillation apparatus, includes a housing, a combustion chamber, fittings for supplying raw materials, fuel, oxidizing gas, and removing reaction products and combustion gases. In this case, the combustion chamber is located in the lower part of the apparatus and is hermetically connected to the apparatus body by a fitting; in the lower part of the combustion chamber there is a water supply fitting, and the raw material input fitting is located above the combustion product input fitting and a mixing section is located between them; Above the raw material input there are at least two more sections: separation and vapor condensation. The technical result is a reduction in energy consumption, metal consumption and equipment dimensions, an increase in operational reliability and safety due to the fact that the possibility of coking and burning of pipes is eliminated. 5 ill.

The invention can be used in the coke industry. The rectification column for a delayed coking installation includes a strengthening part (1) with distillation plates (26) and a stripping part (2), in which a jet washing chamber (27) and an inclined partition (33) with a pocket (34) equipped with a fitting (10) are located ) for the removal of super-heavy coking gas oil, located between the feedstock input fittings (6) and the vapor input from the coking chamber (7, 8). Between the jet washing chamber (27) and the inclined partition (33) with a pocket (34), an intermediate partition (28) is installed, equipped with branch pipes (29) with baffle plates (30) and a pocket (31) for removing heavy gas oil contaminated after washing. The invention makes it possible to reduce the energy intensity of the delayed coking process by 1.1-1.3 times. 1 ill.

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The invention relates to a rectification device for purifying water from impurities in the form of water molecules containing heavy isotopes of hydrogen and oxygen. The device contains a distillation column operating under vacuum, an evaporator, a condenser and a heat pump. In this case, the distillation column consists of two coaxial pipes with diameters D1 and D2, with D1>D2 and (D1-D2)/2<300 мм, со слоем насыпной насадки, расположенным в зазоре между ними, при этом распределитель жидкости вверху колонны имеет не менее 800 точек орошения па квадратный метр площади сечения насадочной части колонны. Изобретение обеспечивает повышение производительности и снижение энергетических затрат. 4 з.п. ф-лы, 5 ил., 4 табл., 3 пр.

The invention relates to mass transfer equipment in the field of processing hydrocarbon raw materials, chemical and food products, in particular to devices for rectification, absorption of petroleum products, chemical and food products by separating products by boiling point in the process of mass and heat exchange between liquid and steam, and can find application in oil refining, chemical, petrochemical, gas, food industries

A cap distillation column is an industrial device that is used primarily in the production of raw alcohol in large distilleries and vodka factories. Not everyone can use it under amateur conditions, much less do it with their own hands.

Factory cap column

This is not because its structure is too complex, but its manufacture requires special tools or high skill. Any qualified mechanic, or a person who knows how to work with basic hand-held power tools, can handle the construction of a cap column in a home workshop. All components of the cap column can be easily purchased in a store or online. It is not difficult to assemble them with your own hands using equipment that is available in any garage. With certain skills, many parts of the column can be made independently.

If you decide to build a moonshine still equipped with a cap column with your own hands, then you should remember that the dimensions of the device play a very important role here. If you violate the proportions, then instead of a cap-type distillation column you will get an ordinary distiller, which works even worse than a classically designed apparatus.

Operating principle of a cap column

The bell-cap column operates on the principle of heat and mass transfer between steam rising from below, from the evaporator, and cooled reflux flowing down from above. Caps or plates serve to increase the contact area of ​​heated steam and liquid. The number of points where steam turns into liquid and where the liquid re-evaporates depends on the number of plates. Alcohol-containing vapor condenses not only on the inner walls of the column, but also on the surface of the plates. They have the shape of a hemisphere, convexly facing upward.

The reflux condensing on the outer surface flows down through the overflow holes and falls onto the lower plate, heated to a higher temperature. The alcohol and other low-boiling fractions are re-evaporated, and liquids with a higher boiling point (fusel oils and water) flow back to the evaporator, where they remain in the form of an aqueous solution.

When alcohol vapor passes through a column 50 centimeters high and 8-10 caps are installed inside it, the process of converting the liquid into steam and back occurs at least 30-40 times. This amount is called the cleaning factor. If you read in the characteristics of industrially manufactured cap columns, which you can easily buy on the Internet, that their purification ratio is 20 or 50, this does not mean that the alcohol becomes so many times purer, but characterizes only the features of the technological process.

Naturally, the higher the frequency, the better the quality of the alcohol, and the fewer impurities it contains. The ratio of the diameter and height of the column should be at least 1 to 8; these are the optimal dimensions for both industrial and amateur installations. Rising up the column, the steam is enriched with alcohol and impurities are removed from it, it is strengthened, which is why such columns are often called strengthening columns.

Features of work

If you are going to distill the mash on a bell-shaped column, then you should remember that during the distillation process only the tails of the moonshine are cut off; to remove the heads - methyl alcohol, acetone, ether and aldehydes, you must use fractional distillation and select the estimated number of heads, as in the work in a conventional distiller. If you are distilling raw alcohol, the selection of heads is no longer required; they are removed at the stage of primary distillation.

It is very easy to maintain the temperature regime of distillation on a cap column - the temperature on the upper thermometer (near the outlet pipe from the column) should be 72-75 degrees Celsius. When re-distilling, the temperature can be raised to 78 C, the quality of the resulting raw alcohol will not deteriorate too much.

Manufacturing of a cap column

It’s not difficult to make a bell-shaped column with your own hands if you have one of the most difficult components to make - bell-shaped plates. You can buy them on the corresponding websites on the Internet. In most cases, plates are sold from China. But you don’t have to choose - the product is too specific and only a few workshops produce them. Making work plates yourself is quite difficult, but possible.

To do this, you will need copper or stainless steel plates, from which circles are cut equal to the internal diameter of the main pipe of the column. The column itself is made of glass, copper or stainless steel pipe, with a diameter of 8-10 mm and a length (height) of about 75 cm. Glass columns, offered by many manufacturers, are popular due to the fact that the bubbling process can be observed - this is a rather spectacular sight . But the material has little effect on the performance of the column.

4 holes with a diameter of 1-1.5 mm are made in the cut out disks and copper or stainless steel tubes about 1.5 cm high are inserted into them. They serve to pass steam from the bottom up. Two holes are made along the edges of the disk. Their diameter is about 10 mm. Tubes are also inserted into them, but smaller in height - 1.5-0.8 cm. The joints of the tubes and disks are soldered.

Copper plates for column

Caps are placed on the ends of the middle tubes so that they touch the surface of the disk. The upper part of the tubes is perforated around the perimeter with holes 1-2 mm in diameter to allow steam to escape. The more there are, the better. The lower edges of the caps are sawed to a height of 0.5 cm. They should be 2 mm below the cut of the side tubes.

It is difficult to make classic hemispherical caps, so you can make them cone-shaped or glass-shaped. They can be secured to the steam pipes with self-tapping screws or couplings. The plate assembly represents one working element. In a column of the specified height there must be at least 5 of them, maximum - 8.

To make it more convenient to insert the plates into the column and remove them for cleaning, they are placed on a pin with a diameter of 5-8 mm and secured with nuts at an equal distance from each other. The upper edge of the column is connected by a steam line to a flow-type refrigerator. Thermometers are installed at the top of the column and on the cube. To make it more convenient to install and remove the plate assembly from the body, the top of the column is made in the form of a screw cap. The steam outlet pipe is installed below the thread level by 1-1.5 cm.

How it works

Video on how to make a cap column:

Steam from the cube with mash rises up and fills the space above the first plate through the steam pipes. There it condenses and settles as a liquid on its surface. When its level becomes higher than the slots on the caps, steam breaks through the liquid and, due to the bubbling phenomenon, removes the remaining alcohol vapor from it and rises up, entering another plate. There the process is repeated.

When the level of phlegm on the plate rises above the cut of the pouring tube, it flows down into the cube. As the steam rises, it becomes richer in alcohol and, after passing through the last plate, is almost completely freed from impurities.

A cap-shaped distillation column works most effectively when re-distilling moonshine obtained in a conventional moonshine still, but primary mash can also be distilled on it. True, the process will go quite slowly.

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Introduction

Rectification(from Latin rectus - correct and facio - I do) - separation of homogeneous liquid mixtures into practically pure components, differing in boiling points, through repeated evaporation of liquid and condensation of vapor. This is the main difference between rectification and distillation, in which, as a result of a single cycle of partial evaporation-condensation, only preliminary separation of liquid mixtures is achieved. Flows of steam and liquid during the rectification process, moving in countercurrent, repeatedly contact each other in special devices - distillation columns. Part of the steam (or liquid) leaving the apparatus is returned back after condensation (for steam) or evaporation (for liquid). This countercurrent movement of the contacting flows is accompanied by processes of heat exchange and mass transfer, which at each stage of contact proceed to a state of equilibrium; at the same time, the ascending steam flows are continuously enriched with more volatile low-boiling component (NC), and the flowing liquid is less volatile - high boiling point (HC). Using the same amount of heat as during distillation, rectification allows one to achieve greater extraction and enrichment of the desired component or group of components. Rectification is distinguished between continuous and periodic. In the case of continuous rectification, the mixture to be separated is continuously fed into the rectification column and two or more fractions, enriched with some components and combined with others, are continuously removed from the column. The complete column consists of 2 sections - strengthening and exhaustive. The initial mixture (usually at boiling point) is fed into the column, where it is mixed with the extracted liquid and flows down the contact devices (plates or nozzle) of the exhaust section in countercurrent to the rising steam flow. Having reached the bottom of the column, the liquid stream, enriched with highly volatile components, is fed into the column cube. Here the liquid is partially evaporated by heating with a suitable coolant, and the steam again enters the exhaust section. The steam coming out of this section enters the strengthening section. Having passed through it, the steam, enriched with volatile components, enters the reflux condenser, where it is usually completely condensed with a suitable refrigerant. The resulting liquid is divided into 2 streams: distillate and reflux. Distillate is a product flow, and reflux goes to irrigate the strengthening section, through the contact devices of which it flows. Part of the liquid is removed from the bottom of the column in the form of a bottom residue. The ratio of the amount of reflux to the amount of distillate is denoted by R and is called reflux ratio. This number is an important characteristic of the rectification process: the higher R, the higher the operating costs of the process. The minimum required heat and cold costs associated with performing any specific separation task can be found using the concept minimum reflux ratio. The minimum reflux ratio is found by calculation based on the assumption that the number of contact devices, or the total height of the nozzle, tends to infinity. If the initial mixture needs to be divided continuously into a number of fractions greater than two, then a serial or parallel-series connection of columns is used. At periodic rectification the initial liquid mixture is simultaneously loaded into the column cube, the capacity of which corresponds to the desired productivity. Vapors from the cube enter the column and rise to the reflux condenser, where they are condensed. In the initial period, all condensate returns to the column, which corresponds to the full irrigation regime. The condensate is then divided into reflux and distillate. As the distillate is selected (either at a constant reflux ratio or with its change), first the highly volatile components are removed from the column, then the moderately volatile ones, etc. The required fraction (or fractions) is selected into the appropriate collection. The operation continues until the initially loaded mixture is completely processed. Apparatuses used for rectification - rectification columns - consist of the column itself, where countercurrent contact of steam and liquid occurs, and devices in which evaporation of liquid and condensation of steam occurs - a cube and a reflux condenser. The column is a vertically standing hollow cylinder, inside of which plates (contact devices of various designs) are installed or a shaped piece of material - a nozzle - is placed. The cube and reflux condenser are usually shell-and-tube heat exchangers (tube furnaces and rotary evaporators are also used). The purpose of the trays and nozzle is to develop the interfacial surface and improve the contact between liquid and vapor. The plates are usually equipped with a device for overflowing liquid. As a packing for distillation columns, rings are usually used, the outer diameter of which is equal to their height. The most common are Raschig rings and their various modifications. In both packed and disc columns, the kinetic energy of steam is used to overcome the hydraulic resistance of contact devices and to create a dynamic disperse system of steam - liquid with a large interfacial surface. There are also distillation columns with mechanical energy supply, in which a dispersed system is created by rotating a rotor mounted along the axis of the column. Rotary devices have a lower pressure drop over height, which is especially important for vacuum columns. Calculation of a distillation column comes down to determining the main geometric dimensions of the column - diameter and height. Both parameters are largely determined by the hydrodynamic operating mode of the column, which, in turn, depends on the speeds and physical properties of the phases, as well as on the type of packing. Rectification is widely used both on an industrial, preparative and laboratory scale, often in combination with other separation processes such as adsorption. Extraction and crystallization. Rectification is also applicable for the production of individual fractions and individual hydrocarbons from petroleum feedstocks in the oil refining and petrochemical industries. Rectification is widely used in many industries: coke-chemical, wood-chemical, food, chemical-pharmaceutical industries, etc. Recently, rectification has become increasingly practical in connection with the solution of such important problems as the purification of substances and the isolation of valuable components from waste or natural mixtures. This includes the isolation of stable isotopes of a number of light elements. Rectification as a cleaning method has a number of undeniable advantages, among which the most significant is that the process does not require the introduction of agents that themselves can be sources of pollution.

1. Requirements for the design of distillation columns

Typically, a distillation column is made in the form of a cylinder filled with special distribution devices to create a contact surface between the liquid phase flowing down from above and the vapors rising towards it. The design of distillation columns is usually guided by the requirements for the design of any chemical apparatus (cheapness, ease of maintenance, high productivity, strength, corrosion resistance, durability, etc.) In addition, the following specific requirements for the design of the column must be taken into account:

The column must have maximum throughput capacity for the vapor and liquid phases;

Contact devices must provide maximum contact surface between phases with maximum mass transfer efficiency;

The column must operate stably and uniformly over its entire cross-section under a wide range of loads;

The hydraulic resistance of switchgears should be minimal. The desire to maximally satisfy these requirements, as well as the specific properties of the mixtures to be separated (heat generation, aggressiveness, coking, formation of thermopolymers, etc.), leads to a variety of types of distillation columns.

2. Classification of column devices

2.1 Classification depending on the relative motion of the phases

Features of the devices cross current and complete mixing is that the interaction of phases in these devices is carried out by bubbling the vapor phase through the liquid phase. Therefore, these groups are usually combined under the general name bubble columns; since steam bubbling through a layer of liquid occurs on plates-plates equipped with special devices for introducing steam and flowing liquid, these two groups of distillation columns are also called disc-shaped. Complete mixing columns differ from cross-flow columns mainly in the absence of overflow devices for liquid. The liquid drains onto the underlying plates through the same holes through which the steam rises. As a result of this, complete mixing plates are called failed. IN counter-flow and direct-flow columns the steam flow interacts with the liquid flowing in the form of a thin film over the surface of a special nozzle. Therefore, these two groups of distillation columns are usually combined under the general name film or packed. The most widespread are bubble columns. The working space of these columns is divided into sections formed by plates.

2.2 Classification of plates

When quantitatively calculating the operation of distillation columns, the concept is used theoretical plate(a hypothetical contact device in which thermodynamic equilibrium is established between the flows of vapor and liquid leaving it, that is, the concentrations of the components of these flows are related to each other by a distribution coefficient). Any real distillation column can be associated with a column with a certain number of theoretical plates, the input and output flows of which, both in size and in concentration, coincide with the flows of the real column. Based on this, determine efficiency columns as the ratio of the number of theoretical plates corresponding to this column to the number of actually installed plates. For packed columns, the HETP value (height equivalent to a theoretical plate) can be determined as the ratio of the height of the packed layer to the number of theoretical plates to which it is equivalent in its separating action.

A) cap columns(Fig. a) are most often used in distillation units. Vapors from the previous plate enter the steam pipes of the caps and bubble through a layer of liquid in which the caps are partially immersed. When bubbling steam through a liquid, three bubbling modes are distinguished:

bubble mode (steam bubbles in the form of individual bubbles forming a chain near the wall of the cap);

jet mode (individual steam bubbles merge into a continuous stream);

torch mode (individual vapor bubbles merge into a common flow that looks like a torch).

The caps have holes or serrated slots that divide the vapor into small streams to increase the surface of its contact with the liquid. Overflow tubes serve to supply and drain liquid and regulate the liquid level on the plate. The main area of ​​mass transfer and heat exchange between vapor and liquid, as studies have shown, is the layer of foam and splashes above the plate, created as a result of steam bubbling. The height of this layer depends on the size of the caps, the depth of their immersion, the speed of steam, the thickness of the liquid layer on the plate, the physical properties of the liquid, etc.

It should be noted that, in addition to cap plates, valve, grooved, S-shaped, flake, failure and other plate designs are also used. The advantage of cap-shaped trays is satisfactory operation in a wide range of liquid and steam loads, as well as low operating cost.

b) sieve plates(Fig. b) are used mainly for the rectification of alcohol and liquid air. The permissible liquid and steam loads for them are relatively small, and regulating their operating mode is difficult. Liquid and steam pass alternately through each hole depending on the ratio of their pressures. The plates have low resistance, high efficiency, operate under significant loads and are simple in design. Mass and heat exchange between steam and liquid mainly occurs at some distance from the bottom of the plate in a layer of foam and spray. The pressure and speed of steam passing through the mesh holes must be sufficient to overcome the pressure of the liquid layer on the plate and create resistance to its swelling through the holes. Sieve plates are necessary install strictly horizontally to ensure the passage of steam through all the holes of the plate, as well as to prevent liquid from dripping through them. Typically, the diameter of the holes of the sieve plate is taken in the range of 0.8-8.0 mm.

V) valve plates occupy a middle position between cap and sieve. Valve discs have shown high efficiency over significant load intervals due to the possibility of self-regulation. Depending on the load, the valve moves vertically, changing the open cross-sectional area for the passage of steam, with the maximum cross-section determined by the height of the device that limits the rise. The live cross-sectional area of ​​the steam holes is 10-15% of the cross-sectional area of ​​the column. The steam speed reaches 1.2 m/s. The valves are manufactured in the form of round or rectangular plates with top or lower lift limiter. Trays assembled from S-shaped elements ensure the movement of vapor and liquid in one direction, helping to equalize the concentration of liquid on the plate. The live cross-sectional area of ​​the plate is 12-20% of the cross-sectional area of ​​the column. The box-shaped cross-section of the element creates significant rigidity, allowing it to be installed on a support ring without intermediate supports in columns with a diameter of up to 4.5 m.

G) cascading Venturi plates assembled from separate sheets, bent so that the direction of steam flow is horizontal. The channels for the passage of steam have a Venturi tube cross-section profile, which maximizes the use of steam energy and reduces hydraulic resistance. The flows of steam and liquid are directed in one direction, which ensures good mixing and phase contact. Compared to cap trays, the steam speed can be more than doubled. The design is flexible and does not allow liquid to leak and thereby reduce efficiency. The low holding capacity (30-40% compared to a cap plate) is a valuable feature when processing heat-sensitive liquids. The distance between the plates is selected within the range of 450-900 mm. Cascade trays are successfully used in installations where it is necessary to provide high velocities of steam and liquid.

d) grid plates made from stamped sheets with rectangular slots or assembled from strips. The need for a supporting structure is determined by the thickness of the metal and the diameter of the column. The distance between the plates is usually 300-450 mm. Better performance, compared to cap plates, at maximum loads.

e) wavy plates are made by stamping from perforated sheets 2.5-3 mm thick in the form of sine waves. The rigidity of the structure allows the use of thin metal. The direction of waves on adjacent plates is perpendicular. The depth of the waves is selected depending on the liquid being processed. Due to the greater turbulence of the liquid, the efficiency of the wavy plate is higher. And the risk of clogging is less than for a flat plate. Wave sizes increase with increasing design fluid load. The ratio of the wave height to its length is selected in the range from 0.2-0.4. The plates in the column are located at a distance of 400-600 mm from each other.

and) packed columns have become widespread in industry (see Fig. c). They are cylindrical devices filled with inert materials in the form of pieces of a certain size or packed bodies in the shape of, for example, rings, balls to increase the phase contact surface and intensify the mixing of the liquid and vapor phases.

The structure of a distillation column is quite complex, and it is unlikely to be possible to simulate it at home. But on specialized Internet sites you can buy a working installation at a very reasonable price, which will only require minor re-equipment of your moonshine still.

The conversion will only affect the evaporator tank - it is necessary to install a flange of a suitable diameter so that the column can be secured strictly vertically. If there was no thermometer on the tank, you will have to install one. Without measuring the temperature on the evaporator, it is extremely difficult to control the operation of the column, and, in principle, impossible at all.

How does a column work?

The column is a heat and mass exchanger in which complex physical and chemical processes occur. They are based on the difference in boiling temperatures of various liquids and the latent heat capacity of phase transitions. This sounds very mysterious, but in practice it looks somewhat simpler.

The theory is very simple - steam containing alcohol and various impurities, which boil at different temperatures differing by several degrees, rises up and condenses at the top of the column. The resulting liquid flows down and meets a new portion of hot steam along the way. Those liquids whose boiling point is higher evaporate again. And those that lack thermal energy remain in a liquid state.

The distillation column is constantly in a state of dynamic equilibrium of vapor and liquid; in many cases it is difficult to separate the liquid and gaseous phases - everything seethes and boils. But according to density, depending on the altitude, all substances are divided very clearly - light at the top, then heavier, and at the very bottom - fusel oils, other impurities with a high boiling point, water. Separation into fractions is carried out very quickly, and this state is maintained almost indefinitely, subject to the temperature conditions in the column.

At a height corresponding to the maximum content of alcohol vapor, an intake pipe is installed, through which steam is released and enters the condenser (refrigerator), from where the alcohol flows into a collecting container. The distillation column for a moonshine still operates very slowly - selection, as a rule, is done drip-by-drop, but at the same time a high level of purification is ensured.

The column operates at atmospheric pressure, or slightly above it. To do this, an atmospheric valve or simply an open tube is installed at the top point - the vapors that have not had time to condense leave the column. As a rule, there is practically no alcohol in them.

States of vapor-liquid components at different heights of the column

The graph shows the fixed states of the vapor-liquid components at different heights of the column, which can be controlled by the temperature at a given point. The horizontal part of the graph corresponds to the maximum concentration of the substance. The division has no clear boundaries - the vertical line corresponds to a mixture of the lower and upper fractions. As you can see, the volume of the boundary zones is much smaller than the fractional zones, which gives a certain backlash in the temperature regime.

Distillation column design

The base for the column is a vertical pipe made of stainless steel or copper. Other metals, especially aluminum, are not suitable for this purpose. The pipe is insulated from the outside with a material of low thermal conductivity - energy leakage can upset the established balance and reduce the efficiency of heat exchange processes.

A reflux condenser pre-cooler is mounted at the top of the column. Typically, it is an internal or external coil that cools approximately 1/8-1/10 of the column height. You can also find distillation columns with a water jacket or complex spherical refrigerators on the Internet. Apart from price, they don't affect anything else. The classic coil does its job perfectly.

Column "Baby"

The ratio of the amount of condensate collected to the total amount of reflux returning to the tank is called the reflux ratio. This is a characteristic of an individual column model and describes its operating capabilities.

The lower the reflux ratio, the more productive the column. When Ф=1, the column works like a regular moonshine still.

Industrial installations have a high fractional separation ability, so their number is 1.1-1.4. For a household moonshine column, the optimal value is Ф = 3-5.

Types of columns

The distillation column for a moonshine still is equipped with fillers that significantly increase the contact area to increase the points of contact between vapor and liquid, where heat exchange and diffusion processes occur. Based on the type of internal structure, columns are divided into plate and packed. Classification by performance or height does not show real capabilities.

To increase the contact area, a fine stainless steel mesh twisted into a spiral, loose small balls, Raschig rings, and small wire spirals are placed inside the column. They are packed tightly or backfilled to a height of up to ¾ of the length of the column, without reaching the alcohol intake point.

The thermometer must be located in an area free from nozzles and show the real temperature of the environment. An electronic thermometer is selected as having the least inertia. In some column models, tenths of a degree play a role. To obtain pure alcohol in the selection area, the temperature must be maintained within 72.5-77 C.

A tray distillation column is much more difficult to manufacture - the design is of cap or sieve trays, which are horizontal partitions inside, through which the liquid flows with some delay. A bubbling zone is created on each of the plates, increasing the degree of extraction of alcohol vapor from the reflux. Sometimes distillation columns are called strengthening columns - they achieve almost one hundred percent alcohol yield with a minimum of foreign additives.

The column operates at atmospheric pressure; to communicate with the external environment, the column is equipped with a special valve or an open tube in the upper part of the structure. This fact determines one of the features of the distillation column for a moonshine still - it works differently at different atmospheric pressures. The temperature regime varies within a few degrees (the difference on the thermometer of the tank and the column). The relationship is established experimentally. For this reason, with a heating element column.

By purchasing a working distillation column, or building it yourself, you can obtain highly purified alcohol without much difficulty. The column is especially effective when distilling moonshine obtained from a conventional distiller.