Types of column trays. Classification and types of bubble columns (trays)

03.03.2020

Modular plate column. Practice on automation BKU - 011M.

Copper cone lids. A column of copper flavor. Theory and practice.

Alcohol mashine. Cap column HD/3-500 KKS-N. Part 1. New in 2016.

Alcohol mashine. Cap column HD/3-500 KKS-N. Part 2. New in 2016.

Alcohol mashine. Plate column.

What is a tray column and why is it needed at all... prismatic attachment) actually plates. With the help of a tray column, we will not get pure alcohol. However, we can get on it the so-called under-rectification with a strength of 90-95 vol. That is, it is also not alcohol, but it is no longer a distillate. A very highly refined distillate that still retains notes of the original raw material. This technology has been used for more than a hundred years, and it is actively used by distillers around the world. Our country in this sense has not been an exception in recent years. These columns are gaining immense popularity.

Let us analyze the main differences between the columns for a correct understanding of the choice of a particular column.

Like all our equipment, tray columns are distinguished by series: HD/4 or HD/3. Everything is simple here. If you already have HD equipment, the choice is made according to the corresponding series of equipment. If you are only going to purchase equipment, then you need to understand the difference between the HD / 4 and HD / 3 series. The HD/4 series is more budgetary, it has an optimal price-quality ratio. The HD/3 series has a higher price but also higher performance.
Materials used in the manufacture of columns. It is either food grade stainless steel or quartz glass. In the latter case, you have the opportunity to observe the process visually, which is a real pleasure. Do not forget that in the first place we do this hobby for the sake of pleasure.
The columns also differ in height and in the number of plates in them. The height of the column comes in two sizes: 375 and 750 mm, respectively. On a shortened column, you can get "under-rectified" with a strength of 91-92C, on a column of 750 mm you can get "under-rectified" about 95C. Since the disc columns are collapsible, the number of plates in the column can be adjusted by the distiller independently.
Plate execution type. Plates are made of two types: failure and cap. It is difficult to say unequivocally which of the plates is better and on which plates the drink will turn out tastier. The fact is that failure plates are good if we use a stable heating power, without jumps in the network. If the network is unstable, then you can use a heating power stabilizer for example. The cap-type plates are more unpretentious and any heating can be used. However, due to the complexity of manufacturing such columns, they are more expensive. But also more aesthetic in the process.
Plate making materials. Failed plates are made of inert PTFE. Cap cymbals are made from either stainless steel or copper. Stainless steel is known to be inert. And therefore, the drink obtained on its surface does not have any characteristic additional tastes, except for the original raw material. Copper, on the other hand, is believed to absorb harmful sulfur released during the distillation process, thereby relieving the drink of unpleasant odors and tastes. Supporters of copper and stainless steel have many fans. Everyone has their own arguments in favor of the material used for the plates.

You can learn more about working with disc columns here.

The purpose of the article is to analyze the theoretical and some practical aspects of homework distillation column, aimed at obtaining ethyl alcohol, as well as to dispel the most common myths on the Internet and clarify the points that equipment sellers are “silent about”.

Alcohol rectification– separation of a multicomponent alcohol-containing mixture into pure fractions (ethyl and methyl alcohols, water, fusel oils, aldehydes, and others) having different boiling points by repeated evaporation of the liquid and condensation of steam on contact devices (trays or nozzles) in special counterflow tower apparatuses.

From a physical point of view, rectification is possible, since initially the concentration of individual components of the mixture in the vapor and liquid phases is different, but the system tends to equilibrium - the same pressure, temperature and concentration of all substances in each phase. Upon contact with a liquid, the vapor is enriched with volatile (low-boiling) components, while the liquid, in turn, is enriched with low-volatile (high-boiling) components. Simultaneously with enrichment, heat exchange takes place.

circuit diagram

The moment of contact (interaction of flows) between vapor and liquid is called the process of heat and mass transfer.

Due to the different directions of movements (steam rises, and the liquid flows down), after the system reaches equilibrium in the upper part of the distillation column, it is possible to separately select practically pure components that were part of the mixture. First, substances with a lower boiling point (aldehydes, esters and alcohols) come out, then with a high one (fusel oils).

A state of balance. Appears at the very boundary of the phase separation. This can only be achieved if two conditions are met simultaneously:

Equal pressure of each individual component of the mixture.
The temperature and concentration of substances in both phases (vapor and liquid) is the same.

The more often the system comes into equilibrium, the more efficient the heat and mass transfer and the separation of the mixture into individual components.

Difference between distillation and rectification

As you can see in the graph, from a 10% alcohol solution (mash) you can get 40% moonshine, and during the second distillation of this mixture, a 60-degree distillate will come out, and during the third - 70%. The following intervals are possible: 10-40; 40-60; 60-70; 70-75 and so on up to a maximum of 96%.

Theoretically, to get pure alcohol, 9-10 successive distillations are required on a moonshine still. In practice, distillation of alcohol-containing liquids with a concentration above 20-30% is explosive, moreover, due to the high energy and time costs, it is economically unprofitable.

From this point of view, the rectification of alcohol is a minimum of 9-10 simultaneous, stepwise distillations that occur on different contact elements of the column (packings or plates) along the entire height.

difference	Distillation	Rectification
Organoleptics of the drink	Keeps aroma and taste of initial raw materials.	It turns out pure alcohol without smell and taste (the problem has a solution).
Fortress at the exit	Depends on the number of distillations and the design of the apparatus (usually 40-65%).	Up to 96%.
The degree of separation into fractions	Low, substances even with different boiling points are mixed, it is impossible to fix this.	High, pure substances can be isolated (only with different boiling points).
Ability to clean harmful substances	Low or medium. To improve the quality, a minimum of two distillations with separation into fractions in at least one of them is required.	High, with the right approach, all harmful substances are cut off.
Alcohol loss	High. Even with the right approach, you can extract up to 80% of the total amount, while maintaining an acceptable quality.	Low. Theoretically, it is possible to extract all the ethyl alcohol without loss of quality. In practice, at least 1-3% losses.
The complexity of the technology for implementation at home	Low and medium. Even the most primitive apparatus with a coil is suitable. Equipment improvements are possible. The technology of distillation is simple and clear. A moonshine still does not usually take up much space in working order.	High. Special equipment is required, which is impossible to manufacture without knowledge and experience. The process is more difficult to understand, preliminary at least theoretical preparation is needed. The column takes up more space (especially in height).
Danger (compared to each other), both processes are flammable and explosive.	Due to the simplicity of the moonshine still, distillation is somewhat safer (subjective opinion of the author of the article).	Due to the complex equipment, when working with which there is a risk of making more mistakes, rectification is more dangerous.

Operation of the distillation column

Distillation column- a device designed to separate a multicomponent liquid mixture into separate fractions according to the boiling point. It is a cylinder of constant or variable section, inside which there are contact elements - plates or nozzles.

Also, almost every column has auxiliary units for supplying the initial mixture (raw alcohol), controlling the rectification process (thermometers, automation) and distillate extraction - a module in which the vapor of a certain substance extracted from the system is condensed and then taken out.

One of the most common home designs

Raw alcohol- a product of the distillation of mash by the classical distillation method, which can be "filled" into a distillation column. In fact, this is moonshine with a strength of 35-45 degrees.

Reflux- steam condensed in the dephlegmator, flowing down the walls of the column.

Phlegm number- the ratio of the amount of reflux to the mass of the sampled distillate. There are three streams in the alcohol distillation column: steam, phlegm and distillate (end goal). At the beginning of the process, the distillate is not withdrawn so that there is enough reflux in the column for heat and mass transfer. Then part of the alcohol vapor is condensed and taken from the column, and the remaining alcohol vapor continues to create a reflux flow, ensuring normal operation.

For the operation of most installations, the reflux ratio must be at least 3, that is, 25% of the distillate is taken, the rest is needed in the column for irrigating the contact elements. General rule: The slower the alcohol is withdrawn, the higher the quality.

Distillation column contact devices (trays and packings)

They are responsible for the multiple and simultaneous separation of the mixture into liquid and vapor, followed by the condensation of vapor into a liquid - the achievement of an equilibrium state in the column. Ceteris paribus, the more contact devices in the design, the more effective distillation in terms of alcohol purification, since the surface of phase interaction increases, which intensifies the entire heat and mass transfer.

theoretical plate- one cycle of exit from the equilibrium state with its repeated achievement. To obtain high-quality alcohol, a minimum of 25-30 theoretical plates is required.

physical plate- a real working device. The vapor passes through the liquid layer in the plate in the form of many bubbles, creating an extensive contact surface. In the classical design, the physical plate provides about half of the conditions for reaching one equilibrium state. Therefore, for the normal operation of the distillation column, two times more physical plates are required than the theoretical (calculated) minimum - 50-60 pieces.

Nozzles. Often, plates are placed only on industrial installations. In laboratory and home distillation columns nozzles are used as contact elements - copper (or steel) wire twisted in a special way or dishwashing nets. In this case, the phlegm flows down in a thin stream over the entire surface of the nozzle, providing the maximum contact area with steam.

Washcloth nozzles are the most practical

There are a lot of structures. The disadvantage of home-made wire nozzles is the possible damage to the material (blackening, rust), factory counterparts are devoid of such problems.

Properties of distillation column

Material and dimensions. The column cylinder, nozzles, cube and distillers must be made of a food-grade, stainless, heat-safe (expands evenly) alloy. IN makeshift designs as a cube, cans and pressure cookers are most often used.

The minimum length of the pipe of a home distillation column is 120-150 cm, diameter is 30-40 mm.

heating system. In the process of rectification, it is very important to control and quickly adjust the heating power. Therefore, the most successful solution is heating with the help of heating elements built into the bottom of the cube. The supply of heat through a gas stove is not recommended, because it does not allow you to quickly change the temperature range (high inertia of the system).

Process control. During rectification, it is important to follow the instructions of the column manufacturer, which must indicate the features of operation, heating power, reflux ratio and model performance.

The thermometer allows precise control of the sampling process

It is very difficult to control the rectification process without two simple devices - a thermometer (helps determine the correct degree of heating) and an alcohol meter (measures the strength of the resulting alcohol).

Performance. It does not depend on the size of the column, since the higher the side (pipe), the more physical plates are inside, therefore, the cleaning is better. The performance is affected by the heating power, which determines the speed of steam and reflux flows. But with an excess of supplied power, the column chokes (stops working).

The average performance of home distillation columns is 1 liter per hour with a heating power of 1 kW.

Influence of pressure. The boiling point of liquids depends on pressure. For successful distillation of alcohol, the pressure at the top of the column should be close to atmospheric - 720-780 mm Hg. Otherwise, when the pressure decreases, the vapor density will decrease and the evaporation rate will increase, which may cause flooding of the column. If the pressure is too high, the evaporation rate drops, making the operation of the device inefficient (there is no separation of the mixture into fractions). To maintain the correct pressure, each distillation column is equipped with an atmospheric connection tube.

About the possibility of self-made assembly. Theoretically, a distillation column is not a very complex device. Designs are successfully implemented by craftsmen at home.

But in practice, without understanding the physical foundations of the rectification process, correct calculations of equipment parameters, selection of materials and high-quality assembly of units, the use of a home-made distillation column turns into a dangerous occupation. Even one mistake can lead to fire, explosion or burns.

In terms of safety, factory columns that have been tested (have supporting documentation) are more reliable, and they are also supplied with instructions (must be detailed). The risk of a critical situation comes down to only two factors - proper assembly and operation according to the instructions, but this is a problem for almost all household appliances, and not just columns or moonshine stills.

The principle of operation of the distillation column

The cube is filled with a maximum of 2/3 of the volume. Before turning on the installation, it is imperative to check the tightness of the connections and assemblies, shut off the distillate extraction unit and supply cooling water. Only after that you can start heating the cube.

The optimal strength of the alcohol-containing mixture fed into the column is 35-45%. That is, in any case, distillation of the mash is required before rectification. The resulting product (raw alcohol) is then processed on a column, obtaining almost pure alcohol.

This means that a home distillation column is not a complete replacement for the classic moonshine still (distiller) and can only be considered as an additional purification step that replaces re-distillation (second distillation) with better quality, but levels the organoleptic properties of the drink.

In fairness, I note that most modern models of distillation columns involve working in the moonshine still mode. To proceed to distillation, it is only necessary to close the connection to the atmosphere and open the distillate selection unit.

If both nozzles are closed at the same time, then the heated column may explode due to excess pressure! Don't make these mistakes!

In continuous industrial plants, mash is often distilled immediately, but this is possible due to its gigantic size and design features. For example, a pipe 80 meters high and 6 meters in diameter is considered a standard, in which many more contact elements are installed than on distillation columns for a house.

Size matters. The possibilities of distilleries in terms of cleaning the cube are greater than with home distillation

After switching on, the liquid in the cube is brought to a boil by the heater. The resulting vapor rises up the column, then enters the reflux condenser, where it condenses (phlegm appears) and returns in liquid form along the walls of the pipe to the lower part of the column, on the way back coming into contact with the rising steam on plates or nozzles. Under the action of the heater, the phlegm again becomes steam, and the steam at the top is again condensed by a dephlegmator. The process becomes cyclic, both streams are in continuous contact with each other.

After stabilization (steam and phlegm are sufficient for an equilibrium state), pure (separated) fractions with the lowest boiling point (methyl alcohol, acetaldehyde, ethers, ethyl alcohol) accumulate in the upper part of the column, with the highest (fusel oils) at the bottom. As the selection of the lower fractions gradually rise up the column.

In most cases, a column in which the temperature does not change for 10 minutes is considered stable (you can start sampling) (the total warm-up time is 20-60 minutes). Up to this point, the device works "on its own", creating flows of steam and phlegm that tend to balance. After stabilization, the selection of the head fraction containing harmful substances begins: esters, aldehydes and methyl alcohol.

The distillation column does not eliminate the need to separate the output into fractions. As in the case of a conventional moonshine still, you have to assemble the “head”, “body” and “tail”. The difference is only in the purity of the output. During rectification, the fractions are not “lubricated” - substances with a close, but at least a tenth of a degree, different boiling point do not intersect, therefore, when the “body” is selected, almost pure alcohol is obtained. During conventional distillation, it is physically impossible to separate the yield into fractions consisting of only one substance, no matter what design is used.

If the column is brought to the optimal mode of operation, then there are no difficulties during the selection of the “body”, since the temperature is stable all the time.

The lower fractions (“tails”) are selected during rectification, guided by temperature or smell, but unlike distillation, these substances do not contain alcohol.

Return to alcohol of organoleptic properties. Often, "tails" are required to return the "soul" to rectified alcohol - the aroma and taste of the raw material, for example, apples or grapes. After the process is completed, a certain amount of collected tail fractions is added to pure alcohol. The concentration is calculated empirically by experimenting on a small amount of product.

The advantage of rectification is the ability to extract almost all the alcohol contained in the liquid without losing its quality. This means that the “heads” and “tails” obtained on a moonshine still can be processed on a distillation column and ethyl alcohol safe for health can be obtained.

Flooding of distillation column

Each design has a maximum speed of steam movement, after which the flow of reflux in the cube first slows down, and then stops altogether. The liquid accumulates in the distillation part of the column and "flooding" occurs - the termination of the heat and mass transfer process. Inside there is a sharp pressure drop, extraneous noise or gurgling appears.

Causes of flooding of the distillation column:

exceeding the permissible heating power (most common);
clogging the bottom of the device and overflowing the cube;
very low atmospheric pressure (typical for high mountains);
the voltage in the network is higher than 220V - as a result, the power of the heating elements increases;
design errors and failures.

According to the internal structure, columns are divided into two main groups: tray (Fig. 10.2) and packed.

The most common tray columns are vertical cylindrical vessels, inside which are located transverse partitions - bubbling trays. Each plate is a stage of contact between the rising gases (vapours) and the flowing liquid. The degree of extraction of components from the gas, the clarity of the separation of hydrocarbons, as well as the stripping of the absorbed components from the liquid depends on the number of contact stages and on how good the contact is provided by the design of the plates.

The following requirements are imposed on the trays of distillation and absorption columns: they must provide good contact between liquid and vapor, have low hydraulic resistance, and operate stably with significant fluctuations in steam and liquid flow rates. The plates should be simple in design, easy to use, and have a low weight.

Plates are classified according to the number of flows, types and design of contact elements, the nature of the interaction of phases in the contact zone, and the organization of liquid overflow. According to the number of threads, the plates are made single-, double- and multi-threaded (Fig. 10.3) and plates with a cascading arrangement of the web.

According to the type of contact elements, the plates are divided into cap plates, from S-shaped elements, valve, sieve, lattice, scaly, reed, etc.

Depending on the direction of movement of the vapor and liquid phases, plates with cross-flow, direct-flow and counter-flow are distinguished in the contact zone. According to the organization of the overflow of liquid, the plates are divided into overflow and non-overflow (failure type).

Depending on the diameter of the apparatus, the plates are made with a continuous web and a collapsible design. Plates of a collapsible design are assembled from separate canvases, the width of which allows them to be brought into the column through hatches. The canvases are placed on the support beams.

Fig.10.3. Plate schemes:

a - single-threaded; b- two-stream; in - three-line; g - four-stream; d- cascading

Variants of fastening of sections of the plate sheet and the plate sheet to the body of the apparatus are shown respectively in fig. 10.3. and 10.4

Fig.10.4. Mounting options for plate web sections:

1 - canvas; 2- gasket; 3- plank; 4- clamping area; 5- wedge; 6- bracket

Rice. 10.2 Atmospheric distillation column.

Fig.10.4. Options for attaching the cymbal blade to the body:

a - welding; b - on a gasket with a clamping bar on top; c - on a gasket with a clamp; g - on stuffing box with packing

For ease of installation and repair of plates, the distance between them is taken at least 450 mm, and in the places where hatches are installed in the column body - at least 600 mm.

At present, bubble-cap tray columns predominate on old operating columns. They are complex and metal intensive compared to other types of cymbals. Some of their performance is inferior to more modern types of plates, but they are well mastered. The scheme of operation of cap plates is shown in fig. 10.5.

The gas bubbles through the liquid layer, spraying into small bubbles, which form a layer of foam with a large specific surface area above the liquid on the plate. Each plate has a plurality of round or rectangular holes into which pipes of a certain height are rolled or welded. The pipes are covered with caps having a round or hexagonal section. Between the upper cut of the pipe and the cap there is a gap for the passage of vapors or gases coming from under the plate. The lower part of the caps during operation of the column is in the liquid. The lower edge of the cap has denticles and slots.

The liquid level on the tray is maintained by special baffles, the lower part of which extends to the underlying tray. Due to this, a hydraulic seal is formed, and gases (vapors) pass only through the nozzles under the caps and bubble through the liquid layer, and do not go through the drain pipes or segments.

On fig. 10.6. the top two trays of the distillation column are shown.

The position of the caps can be adjusted, i.e., to set a certain gap between the caps and the upper cuts of the nozzles.

Rice. 10.6. Rice. 10.7.

Rice. 10.6. Scheme of operation of cap plates: 1 - plate; 2 - caps; 3 - drain partition; 4 - nozzles for the passage of vapors; 5 - drain pocket.

Rice. 10.7. General view of the two upper plates: 1 - branch pipe for the exit of vapors from the column; 2 - outlet partition; 3 - entrance partition; 4 - branch pipe for irrigation input; 5 - cap.

Each plate must be strictly horizontal; the position of the caps must be adjusted so that the gases or vapors meet on their way a layer of liquid of the same height. If in any part of the plate the height of the liquid layer turns out to be less, then all the vapors, or their predominant part, will pass in this part of the plate. Here, due to the increased vapor velocity, the caps will work poorly, the liquid will be pushed aside by vapors, the contact between the phases will deteriorate and the efficiency of the process will decrease.

Drain pockets and segments of neighboring trays (see Fig. 10.6.) are located on opposite sides, so the liquid, before entering the underlying tray, passes through the entire area of the tray. The height of the liquid layer on the plate is regulated by means of an overflow plate, bolted to the edge of the outlet baffle

During operation of the column, the height of the liquid level when entering the column more height in front of the spillway. This level difference is called the hydraulic gradient. The larger the column diameter, the longer the fluid path and the higher the hydraulic gradient.

Rice. 10.8. Rice. 10.9.

Rice. 10.8. Distribution of liquid on one - drain (a), two - drain (b), and four - drain (c) plates

Rice. 10.9. Scheme of work of a plate from S - figurative elements

in columns large diameter at high loads on the liquid, a significant hydraulic gradient is created, as a result of which most of the vapors (gases) can pass through the caps located at the drain threshold, causing increased liquid entrainment up to “flooding”, at the same time, overflow through the steam pipes is possible on the opposite plate. To reduce the hydraulic gradient in large-diameter columns, the trays are made two- or four-stream.

With an increase in the flow rate of the tray (Fig. 10.3.), the flow rate of the liquid and the gradient decrease, the permissible maximum vapor velocity increases, but the working area of the tray decreases. When handing over the column, the cap trays are tested for bubbling. After closing the hatch of that part of the column, which is below the test plate, the last plate is filled with water. From below, air is supplied under low pressure from a fan or compressor into the column. With the correct assembly of the plate, air should bubble evenly over the entire cross section. If the air is not flowing evenly, the plate is not assembled correctly: a slope is allowed in one direction or the caps are lowered unevenly or skewed. Plate tests continue after the assembly errors are eliminated. These operations (testing and troubleshooting and leaks) continue until a uniform bubbling of air over the entire cross section of the plate is achieved and all air gaps are eliminated in addition to the slots of the caps.

Dishes S- figurative elements(Fig. 10.10) are designed to create the best possible contact between vapor and liquid and therefore must have a developed contact surface.

Rice. 10.10. plate of S- figurative elements.

On plates of this type, the troughs and caps are formed during assembly S- figurative elements with the same cross section. The assembly is carried out in such a way that the cap part of the element covers the grooved part of the adjacent one, forming a lock for the hydraulic lock during the operation of the plate. The cap part of the element is closed at the ends with plugs that prevent vapor and liquid leakage through the ends.

The main advantages of this type of plates are:

high rigidity of the profile, which makes it possible to manufacture S- figurative elements from sheet steel of small thickness - 2.5 - 3.0 mm; low specific metal consumption; low labor intensity of work on manufacturing, installation and repair; the possibility of using plates without intermediate supports in devices with a diameter of up to 4 m; slight sensitivity to load unevenness and the admissibility of significant regime overloads.

The disadvantages of plates of this type include:

small free section of the column (11-12% of the total section); significant resistance to the passage of vapors, which makes their use undesirable for columns operating under vacuum; sensitivity to contamination and sediments during the processing of contaminated or polymerizing products.

Valve poppets are solid or assembled from several sections of disks in which there are elongated slots or round holes. The slots are covered with plate valves, and the holes are round (Fig. 10.12.). Unlike poppets operating in static mode, i.e. with a constant distance between structural elements, valve poppets operate in dynamic mode.

With an increase in steam flow, the valve rises and opens a larger section for the passage of steam (Fig. 10.13), as a result of which the valve discs have a wide range of steam load changes. Due to the simplicity of design, low weight and stable operation, valve discs are a very promising design. They are less prone to fouling, but fouling and coking can interfere with their operation, because as a result of coking, the valves “stick” and stop working dynamically.

Fig.10.12. . Valve designs:

a- type "Glitch"; b- type "Flexitrey

Fig.10.13. Scheme of operation of the valve of a direct-flow plate of a standard design with loads in pairs:

a- small; b- medium; in - big.

With an increase in steam flow, the valve rises and opens a larger section for the passage of steam, as a result of which the valve discs have a wide range of steam load changes.

Valve trays have other advantages over bubble cap trays, such as:

Uniform distribution of steam over the plate area;

Small weight;

Simplicity of design.

All this makes the use of valve trays promising. Valves are made by stamping from sheet metal with a thickness of 2-3 mm. Valve trays have downcomers of the same type as cap and sieve trays.

sieve the plate is a flat perforated sheet with drain devices with round or slotted holes with a diameter (width) of 3 - 4 mm and more, t = (3-5) d(Fig. 10.14). The total area of the holes, depending on the steam capacity, ranges from 8 to 30% of the sectional area of the column. The steam speed in the holes of the sieve plates is 10 - 12 m/s.

Rice. 10.14. Sieve plate cloth

Sieve plates with baffle elements. The canvas of the plate is made of expanded metal sheets (Fig. 10.15). The direction of the cut coincides with the direction of fluid movement. Above the tray plate (Fig. 7.10) across the liquid flow with a step of 200 mm and an angle of inclination of 60 ° to the canvas, fender elements from an expanded metal sheet with a height of 150 are installed mm at a distance of 40 mm from the canvas of the plate. Sieve trays with baffle elements have high steam productivity, low hydraulic resistance; they are used along with valve trays in vacuum columns.

The direction of the punching of the fender elements is oriented so that the gas-liquid flow, falling on them, is thrown down to the web. Fender elements organize the phase contact zone, promote liquid separation and reduce its entrainment.

Fig.10.15. Plate element made of expanded metal sheets.

1 - plate canvas; 2- baffle element

A variety of sieve plates are lattice failure plates, in which there are no overflow pipes and the liquid flows into the holes in the grate towards the vapors.

There are no overflow partitions in the lattice failure trays (Fig. 10.16.). Liquid and gases (vapours) countercurrently pass through the same openings (slits 3-4 mm), so the level over the entire area is the same. The recommended height of the liquid layer on the plate is 30 mm.

Rice. 10.16a. Fig.10.16b.

Rice. 10.16a. Scheme of operation of a column with mesh plates and downcomers

Rice. 10.16b. The scheme of operation of the column with lattice (failure) plates

The throughput capacity of lattice plates is higher than that of bubble caps. At low speeds of the gas (steam) flow, the efficiency of contact between the phases is greatly reduced.

A variety of lattice plates - tubular or tubular-lattice plates, made up of pipes so that there are gaps between them, through which gases and liquids move countercurrently. A refrigerant is passed through the pipes to remove the heat released during absorption.

The cymbal sections have rectangular slots measuring 4x140 mm, in steps from 8 to 36 mm. Typically, the area of the slots is 10 - 30% of the area of the entire plate. On two adjacent plates, the slots are made in mutually perpendicular directions.

One of the drawbacks of the failure-type lattice trays is their sensitivity to changes in the flow rates of the vapor and liquid phases; therefore, they are used in cases where only relatively small fluctuations in flow are possible

jet plates(Fig.10.17.) have a canvas with notches, the metal of which is bent in the form of petals or tongues. In some cases, transverse partitions are installed on the jet tray, which section off the liquid flow, improve contact, and create the necessary liquid supply on the tray. For the passage of liquid in the partitions, a slot with a height of 10 - 15 mm.

The design of the tray and the way it is connected to the body is usually chosen depending on the diameter of the column and the design of the body. Small diameter plates (up to 1600 mm) are made in the form of a single sheet with or without sides. Plates of large sizes are made detachable, from several segments. Split plates are usually mounted through the top of the column. The dismantling of the elements of split plates during repairs is carried out through side hatches, the dimensions of which must be sufficient so that parts of the plates can pass through them. Hatches are installed through 4 - 10 plates.

Fig.10.17. Baffled jet plate

The trays in the column must be installed horizontally, since when skewed, some of the tray elements are not filled with liquid to the required level, and it is through these elements that the main steam flow rushes, and this sharply worsens the operation of the column. For this reason, warping of the plates and their deflection under the action of their own gravity and the gravity of the liquid are not allowed.

Jet-directed plates. They use the kinetic energy of the vapors to direct the movement of the liquid across the plate, resulting in improved contact between the liquid and the vapor.

Jet-directed plates are made from expanded metal or from sheet with bent tongues that impart oblique movement to the pair.

Tray spacing for small diameter columns (up to 0.8 m) is taken equal to 300 mm, and for columns of larger diameter (450-600 mm) the distance between the plates should provide:

Ease of installation, revision and repair of plates;

Deposition of the main part of the drops carried away by steam from the underlying plate;

Support for the normal flow of phlegm through the drain pipes without flooding.

Column devices are equipped with manholes for inspection and installation of plates. The number of hatches in the column should be such that when disassembling the plates and laying the parts to be disassembled on the platform, mounted near each hatch, it is possible to get to the lower hatch from it. Usually, every five plates arrange one manhole with a diameter of at least 450 mm.

If the medium in the columns is non-corrosive and clogging of the trays with corrosion products, resins, coke, etc. is excluded, i.e. there is no need for frequent disassembly of the trays, then hatches are located after ten trays or more.

The fewer hatches, the lower the cost of the column, the lower the likelihood of product leakage and gas leakage.

10.2. Packed columns.

Packed columns at oil and gas refineries are most often used as absorbers and desorbers, in gas purification and drying processes.

Fig.10.18 Packed column

1 - column body; 2 - distribution grid; 3 - nozzle; 4 - sprinkler.

A packed column is an apparatus with perforated support-distribution grids onto which packing is loaded. From above, the column is irrigated with liquid, from below a stream of vapors (gases) enters. Contact between the flowing liquid and the rising vapors (gases) occurs continuously at the height of the packing layer.

Packed columns operate in various hydrodynamic modes. At low flow rates of vapors (gases) and low liquid irrigation densities, the columns operate in film mode. In this mode, the liquid flows through the packing element in the form of a thin film, so the phase contact surface is mainly the wetted surface of the packing.

With an increase in the speed of movement of gas and liquid, the friction force between them increases, splashes, bubbles, foam are formed, and at the same time the contact surface between the phases increases, this mode of operation is called the suspension mode.

With a further increase in the velocity of vapor (gas) movement, a significant deceleration of the flow of liquid occurs. Liquid begins to accumulate in the free volume of the nozzle. The accumulation of liquid occurs until the friction force between the flowing liquid and the gas rising through the column balances the gravity of the liquid in the packing.

The gas begins to bubble through the liquids. A gas-liquid dispersed system is formed in the column, appearance resembling a gas-liquid emulsion.

This hydrodynamic regime is called the emulsification regime. Even with a slight subsequent increase in the velocity of the gas (vapors), liquid is ejected from the column - the flooding regime. The column works most effectively when switching from the suspension mode to the emulsification mode.

Packed columns differ in the type of packing used, as well as in the method of filling with packing.

The following requirements are imposed on the packing: it must be cheap, easy to manufacture, have a large specific surface area by 1 m 3 occupied volume, provide low hydraulic resistance, be well wetted by the irrigating liquid, have a low bulk density, be resistant to the chemical attack of liquid and gas, and have high mechanical strength.

As elements of bulk nozzles, Raschig rings, Pall rings and saddle nozzles are used (Fig. 10 19.).

Rice. 10.19. Packing elements: a – Raschig rings; b - Pall rings; c - saddle nozzle

Nozzle elements are made of ceramics, porcelain, polymers or sheet metal.

When choosing the size of the packing, it should be taken into account that the larger the size of its element, the higher the allowable gas velocity, the higher the productivity of the column and the lower its hydraulic resistance, but the worse the intensity of mass transfer.

A fine nozzle is preferable when carrying out the process under high pressure, since in this case the hydraulic resistance is not significant. A small nozzle has a large specific surface area.

The main advantages of packed columns are simplicity of construction and low hydraulic resistance.

Disadvantages - the difficulty of removing heat in the process of absorption and poor wettability of the packing at low irrigation densities.

Absorption The process of absorption of a gas or vapor by a liquid absorbent (absorbent) is called.

The process in which a gas or vapor reacts chemically with a liquid is called chemsorption.

Absorption is a selective process. The selectivity of the absorption process makes it possible to extract a certain substance from a gas mixture using an appropriate absorber.

Absorption processes are widely used in various branches of the chemical and oil refining industries for the absorption of ammonia, nitrogen oxides, sulfuric anhydride, hydrocarbon gases, as well as for the sanitation of exhaust gases emitted into the atmosphere.

Absorption is usually accompanied by the release of heat. An increase in temperature impairs the performance of the process, which is why absorption plants are in many cases provided with refrigeration elements.

The process of removing absorbed gases from a liquid is called desorption. Desorption is carried out in a stream of inert gas by evaporation of the solution or under vacuum.

Desorption is used to extract gases and vapors dissolved in the absorber when they are the target products of production.

Absorbers

absorbers call the apparatus (Fig. 10.20) in which the absorption process takes place. According to the method of creating a contact surface between liquid and vapor, absorbers are divided into surface-type devices, packed, bubbling (dish-shaped) and mechanical.

If the gas is well absorbed by the liquid, then there is no need to create a large phase contact surface. In this case, for a good

Rice. 10.20. Absorbers.

A. - plate-shaped: 1- body; 2- droplet eliminator; 3- plate; 4-hatch; 5 - support shell;

V. - nozzle: 1 - body; 2- distribution plate; 3- nozzle; 4- support grid; 5- loading hatches; 6- support; 7- hatches for unloading the nozzle;

I- unsaturated absorbent; II - dry gas; III - raw gas; IV- saturated absorbent

gas absorption, it is enough to pass it over the liquid surface (for example, the process of absorbing hydrogen chloride).

The most widely used for absorption packed columns, relatively simple in design (Fig. 10.20). These are hollow cylindrical apparatuses, into which packing bodies of various shapes are loaded, providing a developed contact surface between liquid and gas. The gas is brought from below under the packing layer, and the liquid is supplied to the packing, while providing a counterflow between the liquid and gas.

Recently, plane-parallel (Fig. 5.3) and honeycomb packings have been mastered, consisting of vertically mounted plates or honeycomb elements that provide good contact between liquid and gas and at the same time have low hydraulic resistance.

The nozzle is placed on the support grate (grate). The grate is made from several sections (Fig. 10.21) laid on the support beams. The clear size between the grate bars should be no more than 0.6 -0.7 of the smallest size of the nozzle element.

Expanded metal gratings are also good support structures for small diameter columns.

Packed absorbers work well with abundant and uniform irrigation, so irrigation devices are one of the important components of the column.

The following basic requirements are imposed on sprinklers: they must not increase the entrainment of liquid with gas; the height of the irrigation device and the distance from the sprinkler to the nozzle should be minimal; they must work stably with fluid flow fluctuations;

Be simple in design and easy to use;

Must not clog when handling contaminated fluids. Sprinklers are divided into gravity and spray. From gravity sprinklers, the liquid flows out in separate streams through holes or slots. Gravity sprinklers include a distribution plate, which is a plate with nozzles through which the liquid flows in separate streams onto the nozzle.

The level of the plate is adjusted with set screws. The diameter of the plate is 0.6 - 0.7 of the diameter of the apparatus. Irrigating liquid is supplied through the nozzle to the center of the plate. Distribution plates are simple in design and reliable in operation, however, with a large diameter of the column, they become bulky and therefore are not used for devices with a diameter of more than 3 m.

In devices of large diameter, irrigation gutters are used (Fig. 10.23), consisting of a number of parallel gutters 1 and main distribution chute 2, located below them. The gutters are bulky and require careful leveling, which is done with set screws.

To sprinklers applies to the tangential nozzle (Fig. 10.24). The liquid to be sprayed is fed into the inner circular chamber of the nozzle tangentially, swirls there and exits at high speed through the central opening. The swirling jet at the exit from the nozzle breaks up into drops. The tangential nozzle provides intensive and relatively uniform irrigation within a radius of 2 - 2.5 m. Several nozzles are installed in large-diameter devices.

Limited use for absorption purposes is found dish columns. They are mainly used in cases where the amount of irrigating liquid is very small. The devices use standard cap, sieve, valve, jet and failure plates. A liquid layer is supported on the plate, through which an ascending gas flow bubbles, distributing in the liquid in bubbles and streams. The gas sequentially passes through the layers of liquid on plates located in the column at a certain distance. Liquid flows continuously from the upper to the lower trays. In the inter-plate space, the gas is separated from the entrained droplets and splashes. The contact between the rising gas and the falling liquid is continuous.

in mechanical absorbers the interfacial contact surface is formed by spraying a liquid in a gaseous medium using various types of rotating devices.

Fig.10.23. Irrigation complaint

Fig.10.24. Tangential nozzle

Mechanical absorbers are superior in efficiency to other types of absorbers. This is explained by the fact that, firstly, when a liquid is sprayed into small drops, a large expanded phase contact surface is formed, and secondly, the absorption of gases by flying liquid drops is several times greater than under the same conditions by a falling film. Due to this, mechanical absorbers are very compact (Fig. 10.25). General disadvantage mechanical absorbers - the complexity of the design and significant spray.

Fig.10.25. Mechanical absorber

Adsorbers

Adsorbers are devices (Fig. 10.26) in which gas, vapor or liquid mixtures are separated by selective absorption of one or more components of the initial mixture by the surface of a porous solid body - an adsorbent.

Most often, adsorbers are used to separate gas or vapor mixtures, purify and dry gas, and capture valuable organic substances from vapor-gas mixtures.

The adsorption process is selective and reversible. This means that each adsorbent is able to absorb only certain substances and not absorb other substances contained in the gas mixture.

Rice. 10.26. Adsorber loading scheme:

1 - lower deflector; 2 - mullite; 3, b - grids; 4 - finely porous silica gel; 5- coarse-pore silica gel; 7 - top deflector

Absorbed matter can be released from the adsorbent by desorption, the reverse process of adsorption.

As adsorbents, solids are used in the form of grains with a size of 2 - 8 mm or dust with a particle size of 50 - 200 micron, with high porosity (for example, 1 g of activated carbon has a pore surface of 200 to 1000 m 2, pore surface 1 G. silica gel is up to 500 m 2).

Adsorbers are divided into the following types:

1) with immobile granular adsorbent; 2) with moving granular adsorbent; 3) with a fluidized (“boiling”) layer of pulverized adsorbent.

Adsorbers with a fixed bed of granular adsorbent are hollow vertical or horizontal devices (Fig. 10.27) in which the adsorbent is placed. The steam-air or gas mixture to be separated is fed into the housing 1 adsorber through a special fitting. Inside the adsorber, the mixture passes through a layer of granular adsorbent laid on a grate. 2 . Adsorbent grains absorb a certain component from the mixture. After that, the gas mixture is removed from the adsorber through the exhaust pipe.

The adsorbent can absorb the extracted component up to a certain saturation limit, after which the desorption process is carried out. For this purpose, the supply of the vapor-air mixture to the adsorber is stopped, and then superheated water vapor (or another displacing agent) is supplied to the apparatus, which moves in the direction opposite to the movement of the vapor-air mixture. The vapor mixture (a mixture of water vapor and the extracted component) is removed from the adsorber and fed to the separation in a distillation column or settling tank.

After desorption, which lasts approximately the same time as the adsorption process, hot air is passed through the adsorbent bed, which dries the adsorbent. Air enters the apparatus through the steam connection and is removed through the steam mixture connection.

Fig.10.27. Adsorbers with a fixed bed of granular adsorbent:

a - vertical; b- horizontal; 1- case; 2- lattice; 3.5 fittings

The dried adsorbent is then cooled with cold air to the required temperature.

A modern adsorber is equipped with a system of devices that automatically switch flows from adsorption to desorption, then to drying and cooling at the right time. In order for the installation to continuously separate the gas mixture, it is equipped with two or more adsorbers, which are switched on for absorption and other operations in turn.

Adsorbers with a fluidized bed of pulverized adsorbent are divided into single-stage and multi-stage.

A single-stage adsorber of this type (Fig. 10.29) has a hollow cylindrical vessel 1, in the lower part of which a gas distribution grill is fixed 3. Fluidizing gas, which is also the initial mixture, is fed under the grate. After passing the grate holes, the gas enters the fluidized bed of the pulverized adsorbent 3, where the adsorption process takes place. Gas exiting the bed is cleaned of dust in a cyclone and removed from the apparatus. The adsorbent is continuously introduced from above into the fluidized bed and removed through the tube. The adsorbent is regenerated in another apparatus similar in design to the first one.

Fig.10.29. Single stage adsorber

1- cylindrical body; 2 - gas distribution grid; 3 - fluidized layer of granular pulverized absorbent.

There are quite a few devices and devices for processing fermentation products through distillation. One of these devices, which have become widespread, is a conventional moonshine still. The primitive unit has a fairly simple design and consists of a tank and a steamer. However, some craftsmen who prefer a high quality natural product also use devices such as distillation columns to process the mash. What is it and why they are needed, you will learn further.

general information

The usual distillation moonshine with a primitive design, which is used by most of the inhabitants, will not allow you to get high-quality moonshine. This requires modernized devices, which, in their design features and principle of operation, are similar to industrial units used in distilleries. However, the whole problem lies in the fact that they are not only quite difficult to use, but also require certain knowledge and tools for making at home.

The main difference between industrial equipment and amateur moonshine stills is that they have distillation columns. Every person who has at least some experience with electric tools can make them, and all the necessary parts can be easily purchased at the store. In this case, the dimensions and columns should be taken into account. The thing is that they must be of certain proportions. If you do not comply with them, then you will not get a modernized industrial-type moonshine, but an ordinary distiller.

The purpose of the cap column

Cap columns have a simpler design, and therefore they have become more widespread. Therefore, we will consider the process of upgrading the moonshine still using its example. However, before talking about how to make it, you need to understand the purpose and principle of work.

The bubble cap distillation column performs the function of heat and mass transfer between vapor and liquid. They can have a different number of caps, the more of which there are, the more points in the device for converting vapor into liquid, and the greater the amount of the finished product will be at the outlet.

Principle of operation

As mentioned earlier, the column may have a different number of caps. During the processing of the mash, the caps are heated, and their temperature increases from top to bottom. Each cap has several holes through which phlegm flows and enters the cap located below. In this way, several re-evaporation processes take place, resulting in water with a higher boiling point at the outlet. Thanks to this, alcohol with a high degree is obtained.

To make it clearer, it is worth looking at specific example. Let's imagine we have a 50 cm high capped distillation column with ten caps. For one cycle of mash processing, it provides up to 40 repeated evaporation processes, due to which pure alcohol is obtained at the output, the purity ratio of which corresponds to the total amount of evaporation.

Features of the use of columns in the distillation of alcohol

If the distillation moonshine is equipped with a cap-type column, then when processing mash at home, tails should be cut off. The thing is that it is in the very first moonshine that comes out at the beginning of distillation that substances harmful and dangerous to the body, such as ethers, methyl alcohol, acetone and aldehydes, are contained, the use of which can be life-threatening. Therefore, in order to obtain clean, high-quality and safe moonshine, it is recommended to use fractional distillation.

As for the optimum temperature, during the first distillation it should be around 73 degrees, and during the second it should be increased to 78 degrees. This will not affect the volume of the pure product at the output.

How to make a cap column with your own hands?

So, we have considered the principle of operation of the cap column, so it's time to start making it. First of all, you need to buy cap plates in the store, which are the main component of this device. If you already have them, then there will be no problems with the production of the column at home. It is worth noting that you can make the plates yourself, but this process is rather complicated and troublesome, so it is better to buy ready-made ones.

As mentioned earlier, it is very important to maintain the correct ratio of the device, so the first step is to calculate the cap distillation column. The diameter of the shaft in relation to its height must be at least 1 to 8. If this is not done, then harmful impurities will not be completely removed from the alcohol, which will significantly reduce its quality.

In addition to cap plates, you will also need:

copper plate;
glass or copper tube 75 mm high and 10 mm in diameter.

First of all, you need to cut circles with a diameter of 10 mm from them and make four holes in them. Two of them should be in the center of the disk, and two - at the edges and have a diameter of one millimeter. Copper pipes of the appropriate diameter must be inserted into these holes, through which steam will be supplied. To ensure tightness, all holes are recommended to be soldered.

Next, cap plates are mounted on ten-millimeter tubes so that they come into contact with the disks. For fixing with a cap, you can use ordinary metal screws. Small holes with a diameter of 1 mm are made in the upper part of the tube. The more holes there are, the better the tray column will perform its functions. From below, the tubes are cut by 2 millimeters.

Thus, you will have one element of the column ready. For one moonshine still, you need from 5 to 8 of them. To fix each plate on the moonshine still, small pins are used, which provide the plates with good stability and allow you to easily remove them for cleaning.

When processing the mash, the cap columns are connected to the refrigerator using two thermocouples, which are located at the bottom of the device and on the cube. The steam outlet should be slightly below the thread, approximately one centimeter.

How it works?

During the distillation process, hot steam enters through pipes from a tank of mash, which is on fire, into the space above the first cap, where it is converted into a liquid that flows through holes onto a plate. Gradually, the liquid becomes more and more. After the level rises to a certain point, the steam, passing through this liquid, rises together with alcohols to the next plate located above, where the whole process is repeated. After the liquid level exceeds the cut, the reflux flows into the cube.

As the steam passes through the capped plates, the degrees of alcohol increase, and the amount of harmful impurities decreases. Absolutely all cap columns work in a similar way. However, there is one important nuance. If you want to get the highest quality alcohol, it is recommended to do a double distillation. To do this, the mash is first processed on a conventional moonshine still, after which the raw material passes through the column again. It takes quite a long time, but this is the only way to get crystal clear alcohol.

Tray vs. Cap Column: What's the Difference?

Many people are interested in the question of which column is better: plate or cap, but there is no definite answer. The thing is that the type of this equipment does not affect the quality of alcohol, and the main difference lies in design features. Tray columns use traditional trays instead of special caps. Despite the fact that it is impossible to produce natural alcohol on such equipment, it is quite possible to distill the mash into a high-quality distillate.

In our country, the plate column is very popular among the vast majority of distillers and has many variations that allow you to get the most diverse result. To understand what kind of column better fit for you, let's understand their main differences.

Equipment Series

Everything here is quite simple and clear. Depending on the application, all equipment is divided into series. The most popular is the HD 4 cap column, designed specifically for processing mash into high-quality moonshine at home. This equipment is of high quality and affordable price. The second popular series is HD/3, designed for high production volumes and capable of continuous operation.

materials

Modern cap columns can be made of metal or glass. If durability is more important to you, then you should give preference to the first option, however, the metal gives a slight aftertaste, which only glass columns will help get rid of.

Design features

Different variations of the columns have different heights and the number of plates. In most cases, the equipment has a size of 375 or 750 millimeters. The number of plates may vary depending on how strong the product should be at the exit. The more caps, the higher the degree will be in the distillate. It is important to understand that the number of plates can be adjusted manually.

Cymbal type

To date, there are many options for sale on the market, but the most common are cap and failure. The latter are more affordable and allow you to get a quality product, subject to the correct heating regime. Cap-shaped ones have a higher efficiency and allow you to process mash into high-quality distillate in any conditions.

As it turned out, it is not difficult to master the principle of operation of the cap column. In addition, you can make it at home with your own hands. The most important thing is to follow certain instructions during the manufacturing process and observe safety precautions. Don't be afraid to experiment! Only the one who does nothing fails.

CLASSIFICATION AND TYPES OF BUBBLING COLUMNS (PLATES)

When quantitatively calculating the operation of distillation columns, the concept of a theoretical plate is used (a hypothetical contact device in which thermodynamic equilibrium is established between the vapor and liquid flows leaving it, that is, the concentrations of the components of these flows are interconnected by a distribution coefficient). Any real distillation column can be associated with a column with a certain number of theoretical plates, the inlet and outlet flows of which, both in magnitude and in concentration, coincide with the flows of the real column. Based on this, determine the 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 (theoretical tray equivalent height) can be defined as the ratio of the packed bed height to the number of theoretical trays to which it is equivalent in its separating effect.

use different kinds plates: sieve, cap, failure, valve, lamellar, etc.

1. Sieve plates.

They are mainly used in the distillation of alcohol and liquid air. Permissible liquid and steam loads are relatively small for them, and it is difficult to regulate their operation mode. 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 vapor and liquid mainly occurs at some distance from the bottom of the tray in a layer of foam and spray. The pressure and speed of the steam passing through the holes of the mesh must be sufficient to overcome the pressure of the liquid layer on the plate and create resistance to its flow through the holes, sieve plates must be installed strictly horizontally to ensure the passage of steam through all the holes of the plate, and also to prevent liquid from draining through them. usually the diameter of the holes of the sieve plate is taken in the range of 0.8--8.0 mm.

A column with sieve plates is a vertical cylindrical body with horizontal plates (Figure 3.), in which a significant number of holes with a diameter of 1-5 mm are drilled evenly over the entire surface. gas passes through the holes of the plate and is distributed in the liquid in the form of small streams and bubbles. sieve trays are characterized by simplicity of device, ease of installation, inspection and repair. the hydraulic resistance of these plates is small. sieve trays operate stably over a fairly wide range of gas velocities, and in certain gas and liquid loads, these trays are highly efficient. however, sieve trays are susceptible to contaminants and sediments that clog the tray openings.

Figure 3

2. Cap plates.

The caps have holes or scalloped cuts that dismember the vapor into small streams to increase the surface of its contact with the liquid (Figure 4). Overflow pipes are used to supply and discharge liquid and to control the level of liquid on the plate. The main area of mass transfer and heat exchange between vapors and liquid, as studies have shown, is a layer of foam and splashes above the plate, which is 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 steam velocity, the thickness of the liquid layer on the plate, the physical properties of the liquid, etc. other plate designs. The advantage of bubble cap trays is their satisfactory operation in a wide range of liquid and steam loads, as well as low operating costs.

When bubbling steam through a liquid, there are three modes of bubbling:

Ш Bubble mode (steam bubbles in the form of individual bubbles forming a chain near the wall of the cap);
Ш Jet mode (individual steam bubbles merge into a continuous stream);
Ш Torch mode (individual steam bubbles merge into a common flow, which looks like a torch).

They are less sensitive to contaminants than sieve ones and are characterized by a higher interval of stable operation of the column with capped trays. The gas enters the plate through the nozzles, then breaking through the slots of the cap into big number individual jets. Next, the gas passes through a layer of liquid flowing over the plates from one drain device to another.

The vapor formed in the column evaporator enters the first plate and passes through the steam nozzles of the caps. The caps are immersed to a certain level in the liquid phase. As a result, the vapor phase passes through the slots of the caps and bubbling in the form of bubbles in the liquid phase, thereby providing a contact surface between the vapor and liquid phases and the flow of heat and mass transfer processes on this surface. Since the vapor has a higher temperature than the liquid, when interacting with the liquid phase, the vapor cools and a volatile component partially condenses from it, which joins the liquid phase. Thus, it is enriched with a low volatile component, and the content of a highly volatile component increases in the vapor.

Figure 4

3. Valve plates.

Occupy a middle position between cap and sieve. Valve discs have shown high efficiency at significant load intervals due to the possibility of self-regulation. Depending on the load, the valve moves vertically, changing the free area for the passage of steam, and the maximum area is determined by the height of the device that limits the lift (Figure 5). The open area of the steam holes is 10-15% of the sectional area of the column. The steam speed reaches 1.2 m/s. Valves are made in the form of plates of round or rectangular section with an upper or lower lift limiter. Trays assembled from S-shaped elements allow the movement of vapor and liquid in the same direction, helping to equalize the concentration of liquid on the tray. The open section area of the plate is 12-20% of the 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 up to 4.5 m in diameter.

The principle of operation of valve discs is that a freely lying or freely lying round valve above the hole in the plate with a change in gas flow automatically adjusts the size of the gap area between the valve and the plane of the plate for the passage of gas with its weight and thereby maintains a constant gas velocity when it flows out in bubbling layer.

Figure 5. a, b - with round caps; c, with plate valve; g - ballast; 1 - valve; 2 - bracket-limiter; 3 - ballast.

At the same time, with an increase in the gas velocity in the column, the hydraulic resistance of the valve disc increases slightly. The valve lift is limited by the height of the restrictor bracket and usually does not exceed 8 mm.

Advantages of valve trays: relatively high gas throughput and hydrodynamic stability, constant high efficiency over a wide range of gas loads.

4. Venturi Cascades

They are assembled from separate sheets, curved so that the direction of the steam flow is horizontal. The steam passage channels have a Venturi cross-sectional profile, which maximizes the use of steam energy and reduces hydraulic resistance. The vapor and liquid flows are directed in the same direction, which ensures good mixing and phase contact. Compared to bubble caps, the steam speed can be more than doubled. The design is flexible, does not allow the failure of the liquid and reduce the efficiency due to this. The low holding capacity (30-40% compared to bubble caps) is valuable when processing heat sensitive liquids. The distance between the plates is selected within 450-900 mm. Cascade trays are successfully used in installations where it is necessary to provide high vapor and liquid velocities.

5. Lattice plates

They are made from stamped sheets with rectangular slots or are recruited from strips. The need for a support 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 bubble-top trays, at maximum loads.

6. Wavy plates

They are made by stamping from perforated sheets with a thickness of 2.5-3 mm in the form of sinusoidal waves. The rigidity of the structure allows the use thin metal. The direction of the waves on adjacent plates is perpendicular. The depth of the waves is selected depending on the liquid being processed. Due to the large turbulence of the liquid, the efficiency of the wavy tray is higher. And the risk of clogging is less than for a flat plate. The size of the waves increases with the increase in the calculated load on the liquid. The ratio of the wave height to its length is selected in the range of 0.2-0.4. The plates in the column are located at a distance of 400-600 mm from each other.

PACKED COLUMNS

Packed columns are widely used in industry. They are cylindrical apparatuses filled with inert materials in the form of pieces of a certain size or packed bodies, shaped, for example, as rings or balls to increase the phase contact surface and intensify the mixing of the liquid and vapor phases (Figure 6).

Irregular fitting. Irregular packing is used in mass transfer processes under pressure or under low vacuum conditions. This nozzle has a number of advantages, one of which is the practical absence of the problem of material selection. The nozzle can be made of metals, polymers, ceramics.

Lump nozzle. Crushed rocks (quartz, andesite, coke) are used as a lumpy packing. The size of the lumpy nozzle is 25-100 mm with random filling. The advantage of the nozzle are: low cost, chemical resistance. Disadvantage: small specific surface, small free volume.

ring nozzle. The most common type of ring packing is the Raschig ring. They are made of ceramics, porcelain, plastics, metals, carbon-graphite masses. Ring diameter 25-150 mm. Rings up to 50 mm in diameter are loaded in bulk. With large diameters, the rings are stacked in rows.

There are other ring nozzles: rings with a simple and cruciform septum, with perforated walls, etc.

The Rashig nozzle has a low cost, but is ineffective. To increase the efficiency of mass transfer, the annular nozzle is made perforated and with internal partitions - Pall rings and their modifications. The Cascade-mini-ring nozzle belongs to the annular nozzle with a perforated cylindrical part and internal partitions.

Saddle attachment. It has a large specific surface area (25% more than an annular one) and a large free volume. Such a nozzle is produced mainly in the form of Intalox saddles and Berl saddles made of ceramics and plastic in sizes 37x37 mm and 50x50 mm. A special place among the saddle nozzles is occupied by the Intalox metal nozzle, which has a high efficiency.

Regular fit. Properly placed packing differs from irregular packing in lower hydraulic resistance and is therefore particularly suitable for vacuum distillation processes. The disadvantages include their high sensitivity to the uniformity of irrigation.

The simplest regular nozzle - plane-parallel - is a package collected from flat vertical, usually metal plates 0.4-1.2 mm thick, arranged in parallel with the same gap of 10-20 mm. The height of the plate pack is 400-1000 mm. The outer diameter of the package corresponds to inner diameter columns. To increase the uniformity of liquid distribution in the column, the packages are installed one above the other, mutually rotated at an angle of 45-900. Disadvantages of this packing: high metal consumption, poor liquid redistribution, relatively low efficiency.

Figure 6

SCHEMES OF RECTIFYING INSTALLATIONS

Distillation column of periodic (stepwise) action is shown in Figure 7.

Figure 7. 1.Cube; 2 distillation column; 3 dephlegmator; 4 Refrigerator; 5 Sorting lamp.

The cube performs two functions at the same time: it serves as a container for alcohol undergoing rectification and an alcohol vapor converter.

Distillation column of continuous action, shown in the figure

2. A distillation column of continuous operation, shown in Figure 8.

Figure 8.1 Top of the column; 2 Lower part of the column; 3 Cube; 4 Dephlegmator; 5 Reflux cooler; 6 Refrigerator; 8 Output of the finished product.

Also distillation columns are divided into complete and incomplete.

Incomplete columns are divided into two types:

· Brazhnye (distillation) columns operate according to the following principle: food is supplied to the upper plate in the form of steam, and almost pure water comes out of the cube. Steam enriched with alcohol is discharged from the upper part. A reflux condenser is not installed in such a column, so the vapor phase is condensed in a refrigerator.
· In alcohol (concentration) columns, steam is supplied to the cube (under the bottom plate). Alcohol is removed from the upper part, and the residue enriched with water from the lower part. A reflux condenser installed in such columns performs the function of supplying liquid.

Alcohol (concentration) columns are not intended for obtaining clean water, and in the mash (distiller) column it is impossible to obtain pure alcohol.

The full column is a collective version of the mash and alcohol. This view consists of the lower (exhaustive) and upper (concentration) parts. The upper part is fed through the middle part. In full columns, it is possible to obtain both components of the mixture to be separated, but this is only permissible if this mixture consists of two parts. In order to separate the mash (multicomponent mixture), several columns installed in series are changed. Each column separates the mixture into a distillate, which is one or more components, and a residue (non-volatile mixture).

COMPLETE COLUMN

Figure 9. Schematic diagrams of distillation columns: a - complete; b - incomplete distillation; c - incomplete concentration

In a complete distillation column 1, it is possible to obtain almost in pure form both components of the binary (two-component) mixture to be separated. In an incomplete stripping column, an almost pure low-volatility component is discharged from the lower part, and steam, somewhat enriched with a highly volatile component, is removed from the upper part. From the upper part of the incomplete concentration column, an almost pure volatile component is withdrawn, and from the lower part, the residue S, somewhat enriched in the hardly volatile component.

BRAG DISTRIBUTION PLANTS

Figure 10.

In the alcohol industry, two types of distillation plants are used - single-column and double-column. In a single-column installation, the mash, preheated in a dephlegmator 4, enters the upper plate of column 1. The lower part of the column is called the mash, where heating steam is supplied from below. From beer column water-alcohol vapors are sent to the bottom of the alcohol column 2; here couples get stronger. From column 2, the fortified vapors enter the annular space of the dephlegmator 4.

Condensing, the vapors give off heat to the mash flowing in the pipes of the reflux condenser. The water-alcohol vapor condensate returns to column 2 in the form of reflux. Uncondensed vapors are sent to refrigerator 5, where they condense and form raw alcohol. Raw alcohol contains not only water and alcohol, but also other volatile products that are part of the mash. Bragorektifikatsionny installations happen direct, semidirect and indirect action.

1. DIRECT ACTION

Figure 11.

The installation consists of an epuration column 3 with a concentration part 4 and a distillation column 9, which include dephlegmators 5 and 7, as well as condensers 6 and 8. The mash enters beer column 1. Here, ethyl alcohol, tail impurities and the remains of head and intermediate impurities are separated from the mash. The bulk of the vapor from the beer column 1 is sent to the distillation column 9. Some of the vapor from the beer column 1 enters the epuration column 3 to heat it. For this purpose, pipe 2, equipped with a throttle valve, serves. The amount of steam entering the epuration column is controlled by a throttle valve. Tailings and intermediate products, as well as the remains of the head products are taken in a distillation column. The rectified product is withdrawn in liquid form from one of the upper trays of the distillation column.

2. SEMI-DIRECT ACTION

Figure 12.

In the installation of semi-direct action, the mash, without undergoing preliminary epuration, enters directly into the mash column 1. Alcohol and all impurities are separated in this column. Vapors are sent through a trap-separator 3 to an epuration column 2 with a concentration part 4, a dephlegmator 5 and a condenser 6, where head impurities are separated from them.

Alcohol purified from head impurities, containing tail and intermediate impurities (epurate), in liquid form enters the distillation column 9, equipped with a reflux condenser 8 and a condenser 7. The selection of rectified alcohol, fusel oil and intermediate products is carried out in the same way as in direct actions.

3. INDIRECT ACTION

Figure 13.

Water-alcohol vapors rising from the mash column 7 are completely condensed in the reflux condenser 2 and condenser 3, after which they enter in liquid form for epuration in the epuration column 4 with reflux condenser 5 and condenser 6.

The epuret is sent to a distillation column 9, equipped with a reflux condenser 8 and a condenser 7, where intermediate products, fusel oil and rectified alcohol are separated. This installation is accepted as typical due to high performance.

PRACTICAL PART.

To separate simple binary mixtures, one simple column with a small number of device trays (usually no more than ten) is used; to separate multicomponent and continuous mixtures (oil, wide gasoline fractions), a system of columns is required, each of which separates the mixture entering it into the corresponding components (fractions). The number of plates in each of these columns can reach several tens.

The main operating parameters of the rectification process are the pressure and temperature in the system, the ratio of liquid and vapor flows (reflux ratio), the number of contact stages.

Trays are commonly used as contact elements in large distillation columns. Each such plate located in the column is called a physical plate. The purpose of such a plate, like any other contact device, is to ensure the closest contact between the liquid and vapor phases in order to achieve the maximum state of equilibrium between them. Plates work as follows. Steam in the form of bubbles with a developed surface passes through the reflux layer located on the plate. As a result of such "bubbling", heat and mass transfer between the liquid and vapor phases is intensified. The designs of the plates are varied, some of them are standardized. The choice of the type of plate is determined by the type of mixture, the productivity of the column, the requirements for the degree of rectification, the quality of the separated components (fractions), etc. Tray columns are used, as a rule, in large-scale production.