Connection of a reflux condenser and a refrigerator in a beer column. What is a reflux condenser for a moonshine still, its home production

The most common type of heat exchanger in industry is the shell-and-tube type. Variant of it design depends on the tasks facing users. The shell-and-tube does not have to be multi-pipe - an ordinary shirt reflux condenser, direct-flow (a) or counter-flow (b) pipe-in-pipe refrigerator are also shell-and-tubes.

Single-pass heat exchangers with cross-flow movement of heat carriers are also used (c). But the most effective and often used for multi-pipe heat exchangers is the multi-pass cross-flow scheme (d).

With this scheme, one flow of liquid or vapor moves through the pipes, and the second coolant moves towards it in a zigzag manner, repeatedly crossing the pipes. This is a hybrid of counterflow and crossflow options, which allows you to make the heat exchanger as compact and efficient as possible.

The principle of operation of shell-and-tube heat exchangers and their scope

In moonshine brewing, multi-pass cross-flow refrigerators are commonly called shell-and-tube refrigerators (CCT), and their single-pipe version is called a counter- or direct-flow refrigerator. Accordingly, when using these structures as dephlegmators - shell-and-tube and jacket dephlegmators.

In home moonshine stills, brewers and distillation columns steam is supplied to these heat exchangers according to inner pipes, and cooling water - in the casing. Any industrial designer-heat engineer would be outraged, since it is in the pipes that a high coolant velocity can be created, significantly increasing the heat transfer and efficiency of the installation. However, distillers have their own goals and do not always need high efficiency.

For example, in dephlegmators for steam columns, on the contrary, it is required to soften the temperature gradient, spread the condensation zone as much as possible in height, and, having condensed the necessary part of the steam, prevent overcooling of the phlegm. Yes, and precisely regulate this process. Quite different criteria come to the fore.

Among the refrigerators used in moonshine brewing, the most widely used are coils, straight-throughs and shell-and-tubes. Each of them has its own area of ​​use.

For devices with low (up to 1.5-2 l / h) productivity, the most rational is the use of small flow coils. In the absence of running water, coils also give odds to other options. The classic version is a coil in a bucket of water. If there is a water supply system and the productivity of the device is up to 6-8 l / h, then direct-flow pipes designed according to the “pipe in pipe” principle, but with a very small annular gap (about 1-1.5 mm), have an advantage. A wire is spirally wound onto the steam pipe with a step of 2-3 cm, which centers the steam pipe and lengthens the path of the cooling water. With heating capacities up to 4-5 kW, this is the most economical option. A shell-and-tube can, of course, replace a straight-through, but the cost of manufacture and water consumption will be higher.

The shell and tube comes to the fore when autonomous systems cooling, because it is completely undemanding to water pressure. As a rule, a conventional aquarium pump is enough for successful operation. In addition, at heating powers of 5–6 kW and above, a shell-and-tube cooler becomes practically the only option, since the length of a once-through cooler for utilizing high powers will be irrational.

Shell and tube dephlegmator

For reflux reflux columns, the situation is somewhat different. With small, up to 28-30 mm, diameters of the columns, the most rational is an ordinary shirt (in principle, the same shell-and-tube).

For diameters 40-60 mm, this is a high-precision cooler with precise power control and absolute non-airing. Dimroth allows you to set modes with the least supercooling of phlegm. When working with packed columns, due to its design, it makes it possible to center the reflux return, the best way irrigating nozzle.

The shell and tube goes out to foreground with autonomous cooling systems. Irrigation of the nozzle with reflux occurs not in the center of the column, but over the entire plane. This is less effective than Dimroth's, but quite acceptable. The water consumption in this mode for the shell-and-tube will be significantly higher than for Dimroth.

If you need a condenser for a liquid extraction column, then Dimroth is unrivaled due to the accuracy of regulation and low reflux subcooling. A shell and tube is also used for this purpose, but supercooling of phlegm is difficult to avoid and water consumption will be higher.

The main reason for the popularity of shell-and-tubes with appliance manufacturers is that they are more versatile in use, and their parts are easily unified. In addition, the use of shell-and-tube dephlegmators in apparatuses of the “designer” or “changeling” type is unrivaled.

Calculation of the parameters of a shell-and-tube dephlegmator

The calculation of the required heat exchange area can be performed using a simplified method.

1. Determine the heat transfer coefficient.

Name	Layer thickness h, m	Thermal conductivity λ, W/(m*K)	Thermal resistance R, (m 2 K) / W
Metal-water contact zone (R1)			0,00001
	0,001	17	0,00006
Phlegm (average film thickness in the condensation zone for a dephlegmator 0.5 mm, for a refrigerator - 0.8 mm) , ( R3)	0,0005	1	0,0005
			0,0001
			0,00067
		1493

Formulas for calculations:

R = h / λ, (m2 K) / W;

Rs = R1 + R2 + R3 + R4, (m2 K) / W;

K \u003d 1 / Rs, W / (m2 K).

2. Determine the average temperature difference between steam and cooling water.

The temperature of saturated alcohol vapor Tp = 78.15 °C.

The maximum power from the dephlegmator is needed in the mode of operation of the column on itself, which is accompanied by a maximum supply of water and its minimum temperature at the outlet. Therefore, we assume that the water temperature at the inlet to the shell-and-tube (15 - 20) - T1 = 20 ° C, at the outlet (25 - 40) - T2 = 30 ° C.

Tin = Tp - T1;

Tout \u003d Tp - T2;

The average temperature (Тav) is calculated by the formula:

Tav = (Tin - Tout) / Ln (Tin / Tout).

That is, in our case rounded:

Tout = 48°C.

Тav = (58 - 48) / Ln (58 / 48) = 10 / Ln (1.21) = 53 °C.

3. Calculate the heat exchange area. Based on the known heat transfer coefficient (K) and the average temperature (Tav), we determine the required surface area for heat transfer (St) for the required heat output (N), W.

St \u003d N / (Tav * K), m 2;

If we, for example, need to utilize 1800 W, then St = 1800 / (53 * 1493) = 0.0227 m 2, or 227 cm 2.

4. Geometric calculation. Decide on minimum diameter tubes. In the dephlegmator, phlegm goes towards the steam, so it is necessary to meet the conditions for its free flow into the nozzle without excessive hypothermia. If you make tubes of too small diameter, you can provoke a choke or release of phlegm into the area above the reflux condenser and further into the selection, then you can simply forget about good purification from impurities.

The minimum total cross section of the tubes at a given power is calculated by the formula:

Ssec \u003d N * 750 / V, mm 2, where

N - power (kW);

750 - vaporization (cm 3 / s kW);

V is the steam velocity (m/s);

Ssec - the minimum cross-sectional area of ​​\u200b\u200bthe tubes (mm 2)

When calculating distillers column type the heating power is selected based on the maximum steam velocity in the column 1-2 m/s. It is believed that if the speed exceeds 3 m / s, then the steam will drive the phlegm up the column and throw it into the selection.

If you need to dispose of in a dephlegmator 1.8 kW:

Ssec \u003d 1.8 * 750 / 3 \u003d 450 mm 2.

If you make a reflux condenser with 3 tubes, then the cross-sectional area of ​​\u200b\u200bone tube is not less than 450 / 3 = 150 mm 2, the inner diameter is 13.8 mm. nearest larger of standard sizes pipes - 16 x 1 mm (inner diameter 14 mm).

With a known pipe diameter d (cm), we find the minimum required total length:

L \u003d St / (3.14 * d);

L= 227 / (3.14 * 1.6) = 45 cm.

If we make 3 tubes, then the length of the dephlegmator should be about 15 cm.

The length is adjusted taking into account that the distance between the partitions should approximately equal the inner radius of the hull. If the number of partitions is even, then the pipes for supplying and draining water will be on opposite sides, and if odd, on one side of the dephlegmator.

An increase or decrease in the length of the pipes within the radius of the domestic columns will not create problems with the controllability or power of the reflux condenser, as it corresponds to the errors in the calculation and can be compensated by further constructive solutions. You can consider options with 3, 5, 7 or more tubes, then choose the best one from your point of view.

Design features of the shell-and-tube heat exchanger

Partitions

The distance between the partitions is approximately equal to the radius of the body. The smaller this distance, the greater the flow velocity and the less the possibility of dead zones.

Baffles direct the flow across the tubes, this significantly increases the efficiency and power of the heat exchanger. Also, the baffles prevent the deflection of the tubes under the influence of thermal loads and increase the rigidity of the shell-and-tube dephlegmator.

Segments are cut out in the partitions for the passage of water. The segments must not be less than the cross-sectional area of ​​the pipes for water supply. Usually this value is about 25-30% of the partition area. In any case, the segments must ensure the equality of the water velocity along the entire trajectory of movement, both in the tube bundle and in the gap between the bundle and the body.

For a reflux condenser, despite its small (150-200 mm) length, it makes sense to make several partitions. If their number is even, the fittings will be on opposite sides, if odd - on one side of the dephlegmator.

When installing transverse baffles, it is important to ensure that the gap between the housing and the baffle is as small as possible.

tubes

The thickness of the walls of the tubes does not really matter. The difference in the heat transfer coefficient for a wall thickness of 0.5 and 1.5 mm is negligible. In fact, the tubes are thermally transparent. The choice between copper and stainless steel, in terms of thermal conductivity, also loses its meaning. When choosing, one must proceed from operational or technological properties.

When marking the tube plate, they are guided by the fact that the distances between the axes of the tubes should be the same. Usually they are placed at the vertices and along the sides of a regular triangle or hexagon. According to these schemes, with the same pitch, it is possible to place the maximum number of tubes. The central tube most often becomes a problem if the distances between the tubes in the bundle are not the same.

The figure shows an example correct location holes.

For the convenience of welding, the distance between the tubes should not be less than 3 mm. To ensure the strength of the joints, the material of the tube sheet must be harder than the material of the pipes, and the gap between the sheet and pipes should not exceed 1.5% of the pipe diameter.

When welding, the ends of the pipes should protrude above the grate by a distance equal to the wall thickness. In our examples - by 1 mm, this will allow you to make a high-quality seam by melting the pipe.

Calculation of parameters of a shell-and-tube cooler

The main difference between a shell-and-tube refrigerator and a reflux condenser is that the phlegm in the refrigerator flows in the same direction as the steam, so the phlegm layer in the condensation zone increases from the minimum to the maximum more smoothly, and its average thickness is somewhat larger.

For calculations, we recommend setting the thickness to 0.8 mm. In a dephlegmator, the opposite is true - at first, a thick layer of phlegm, which has merged from the entire surface, meets steam and practically prevents it from fully condensing. Then, having overcome this barrier, the vapor enters a zone with a minimum, about 0.5 mm thick, reflux film. This is the thickness at the level of its dynamic retention, condensation occurs mainly in this zone.

Taking the average thickness of the phlegm layer equal to 0.8 mm, on specific example Let us consider the features of calculating the parameters of a shell-and-tube cooler using a simplified method.

Name	Layer thickness h, m	Thermal conductivity λ, W/(m*K)	Thermal resistance R, (m 2 K) / W
Contact zone of metal with water, (R1)			0,00001
Pipe metal (stainless steel λ=17, copper - 400), (R2)	0,001	17	0,00006
Phlegm, (R3)	0,0008	1	0,001
Metal-steam contact zone, (R4)			0,0001
Total thermal resistance, (Rs)			0,00117
Heat transfer coefficient, (K)		855,6

The maximum power requirements for the refrigerator are made by the first distillation, for which the calculation is made. Useful heating power - 4.5 kW. Water inlet temperature - 20 °C, outlet - 30 °C, steam - 92 °C.

Tin \u003d 92 - 20 \u003d 72 ° C;

Tout \u003d 92 - 30 \u003d 62 ° C;

Тav = (72 - 62) / Ln (72 / 62) = 67 °C.

Heat transfer area:

St \u003d 4500 / (67 * 855.6) \u003d 787 cm².

Minimum total cross-sectional area of ​​pipes:

S sec \u003d 4.5 * 750 / 10 \u003d 338 mm²;

We choose a 7-pipe refrigerator. Sectional area of ​​one pipe: 338 / 7 = 48 mm or inner diameter 8 mm. From the standard range of pipes, 10x1 mm is suitable (with inside diameter 8 mm).

Attention! When calculating the length of the refrigerator, you need external diameter- 10 mm.

Determine the length of the refrigerator tubes:

L \u003d 787 / 3.14 / 1 \u003d 250 cm, therefore, the length of one tube: 250 / 7 \u003d 36 cm.

We clarify the length: if the refrigerator body is made of a pipe with an inner diameter of 50 mm, then there should be 25 mm between the partitions.

36 / 2,5 = 14,4.

Therefore, it is possible to make 14 partitions and get water input-output pipes in different directions, or 15 partitions and pipes will look in one direction, and the power will also increase slightly. We select 15 partitions and adjust the length of the tubes to 37.5 mm.

Drawings of shell-and-tube dephlegmators and refrigerators

Manufacturers are in no hurry to share their drawings of shell-and-tube heat exchangers, and home craftsmen do not really need them, but still some schemes are in the public domain.

Afterword

It should not be forgotten that all of the above is a theoretical calculation using a simplified method. Thermal engineering calculations much more complicated, but in the real household range of changes in heating power and other parameters, the technique gives correct results.

In practice, the heat transfer coefficient may be different. For example, due to the increased roughness inner surface pipes, the phlegm layer will become higher than the calculated one, or the refrigerator will not be located vertically, but at an angle, which will change its characteristics. There are many options.

The calculation allows you to accurately determine the dimensions of the heat exchanger, check how the change in pipe diameter will affect the characteristics without extra costs reject all unsuitable or guaranteed worst options.

The home master in the manufacture of strong spirits must correctly determine the desired end result. If the speed and cheapness of the equipment are important to the master, the apparatus will be simple: an alembic and a refrigerator.

If he wants to get the highest quality product at the output, purified from fusel oils and with a strength above 70 degrees, it is necessary to use various additional units: a dry steamer, a bubbler or a dephlegmator.

A reflux condenser is an apparatus for additional purification of alcohol-containing steam. The steam that is formed in the distillation cube when the mash is heated contains not only alcohol, but also heavier impurities of fusel oils and water. If the steam is cooled, these heavy impurities condense, and this condensate is called phlegm. The process of separating phlegm from steam is called reflux.

Definition from the Explanatory Dictionary of Foreign Words, ed. Krysina: “Deflegmation [de], and, pl. no, w. [German] Dephlegmation< лат. dē… от…, раз… + греч. phlegma мокрота, влага]. тех. Частичная конденсация смесей различных паров и газов с целью обогащения их низкокипящими компонентами.»

The phlegm also contains a certain amount of alcohol, so when various designs moonshine stills, it is possible to ensure the return of phlegm to the distillation cube.

The mechanism of work (what is needed)

Classic scheme moonshine still the cube-refrigerator turns into a cube-reflux condenser-super-cooler-refrigerator scheme. The order of the system is as follows:

• Braga is heated in the cube, light fractions evaporate from it - alcohol, fusel oils, water.
• The steam is cooled in a dephlegmator. installed on the cube. Phlegm falls into the cube. where it re-evaporates.
• Sukhoparnik - empty container through which steam passes. It is needed to separate the mash splashes and the heaviest condensate. The dephlegmator can be installed here as well. then the phlegm will be collected and disposed of.
• Bubbler by purpose and design similar to a dry steamer, the difference is that it is designed so that the vapors pass through the water, cooling and being cleaned. If a reflux condenser is installed on a bubbler, then steam bubbling will pass through the phlegm. not pure water.
• There is alcohol in the refrigerator condenses and collects in liquid form in the receiver.

Video review of the glass refrigerator:

Where is it installed?

The reflux condenser can also be installed on the tank of a dry steamer or bubbler. Then the phlegm will not be collected in a cube, which will provide a cleaner product at the exit, but some of the alcohol will remain in the phlegm. In some sources, a dephlegmator is confused with a dry steamer, but still they are different devices.

The dephlegmator is installed:

• On a distillation cube. In this case, we get the likeness of a distillation column.
• On a dryer. In this case, it must be equipped with a tap to drain the accumulated liquid.
• On the bubbler. In this case, it is better to make it transparent so that steam bubbles passing through the phlegm can be observed. and also monitor the level of accumulated phlegm.

Cooler device for moonshine still:

For example, consider the Dimroth dephlegmator. This is a classic laboratory equipment, usually made of heat-resistant double laboratory glass. Represents the main tube, entwined with a coil of glass. This design is placed in a flask that protects against mechanical damage.

The main tube is installed vertically on a cube or dry steamer so that the phlegm flows down due to gravity. Steam passing through the main tube is cooled by cold water from the coil. For supply and return of water, the coil must be equipped with fittings. Such systems are also called shell-and-tube systems.

We make with our own hands

In home moonshine brewing, not everyone uses reflux. But this leads to a deterioration in the quality of the resulting alcohol, or to the use of double distillation. In addition, the dephlegmator is easy to manufacture, and it will last quite a long time.

A home craftsman can make a dephlegmator both shell-and-tube and jacketed. In a jacketed dephlegmator, a simple water jacket will be used instead of a coil. In any case, to make a reflux condenser, you will need soldering or welding skills.

Note: When choosing a material for a reflux condenser, you need to know that the main tube must be made of glass, food grade stainless steel or copper.

These materials do not oxidize and do not change the taste of the resulting alcohol. A shirt or serpentine can be made from any other materials.

Watch a video on how to make a simple refrigerator for moonshine in 15 minutes:

• The shell-and-tube reflux condenser consists of a main tube and a coil wound around it. a simple stainless steel or copper tube can be used as the main tube.
• The length of the tube depends on the volume of production; for home-brewing, an inch tube 25 cm long is enough.
• The diameter can be increased, the length can be reduced.
• The thinner and longer the tube, the longer the distillation will take, and the higher the degree of purification.
• But if the reflux condenser cools the steam too much, then you won’t get the result at all - all the alcohols will drain back into the cube.

It is easy to make a shell-and-tube dephlegmator:

1. A copper tube 6 mm in diameter is wound onto the main tube.
2. Winding length - 15 - 20 cm.
3. The tube is fixed with plastic or clamping clamps; it is possible to put on this structure a suitable diameter foam rubber or foam insulation, which is used to insulate heating systems.
4. Cooling water is supplied to the copper tube.
5. Everything - the dephlegmator is ready.

A more efficient dephlegmator can be made from several tubes of small diameter, placed in a jacket with running water. In this design, the steam has a large contact area with cold walls, which makes the dephlegmator work more efficiently.

It is done like this:

1. Tubes of small diameter are assembled into a cassette, which looks like a revolver drum.
2. If we use this analogy, then steam flows through the cartridge cases, and coolant circulates in the drum housing.
3. This design is difficult to manufacture; to assemble such a design, you need to use stainless steel welding or copper soldering.

What to replace?

If it is problematic to make or purchase a reflux condenser, you can replace it with a simple bubbler.

• To do this, take a simple glass jar (preferably at least 1 liter) with a screw cap. Two holes are drilled in the cover - inlet and outlet.
• Tubes are inserted into the holes, while at the inlet the tube goes down almost to the very bottom, and the outlet tube is located at the very cover.
• It is important to carefully seal the junction of the tubes and the cover. For this you can use cold welding or soldering.
• About one third of cold water is poured into the jar. The mechanism of operation of the bubbler is simple: steam under pressure passes through the tube, passes through the water column. At the same time, it cools, fusel oils condense and dissolve in water.
• Part of the alcohol also dissolves in the water, but this is not a problem: the water is heated by hot steam during operation, and the alcohol re-evaporates from the surface of the can. It should be noted that the reflux condenser has a number of advantages over the bubbler, for example, the ability to adjust the intensity of the reflux process.

Watch the video where the Chinese moonshine cooler is disassembled, it was always interesting from what it is made at the factory:

Industrial apparatus

In the alcohol industry, the use of dephlegmators is a prerequisite. At the same time, there is different kinds- direct and reverse action.

1. Direct action - phlegm enters a separate tank, and is no longer involved in the process.
2. The reverse - phlegm is fed into the distillation cube, evaporates again and again, evaporating the remaining alcohol. In this case, special alcohol traps and ventilation systems are used.

The main purpose of the dephlegmator is to reduce the time and number of technological operations, to improve the initial quality of the product. The reflux condenser separates the steam into several fractions. Steam, passing through the blades and radiators, twists and cools. Control temperature regime carried out automatically using sensors and a controller.

As a result, after the device, the steam contains mainly alcohol and a small part of water - the alcohol strength can reach 70-90 degrees.

Conclusion

So, the use of intermediate refrigerators - reflux condensers - is necessary if you need to get better alcohol at minimal cost.

The use of this device is mandatory if the quality of the mash is low, there are extraneous odors or a high content of fusel oils is felt. At the same time, it is easy to make the simplest designs with your own hands, or order them from argon welders.

Out of the corner of my eye I saw on one of the forums another discussion of the topic “how to supply water to the refrigerator, towards steam or along the way”, in which they referred to my article on the construction of a BC. I have not touched this topic before, so I decided to state my opinion separately in this article.

In the BC design I proposed, water is supplied to the apparatus from below and it turns out that it enters the dephlegmator along the way (forward flow) to steam, and towards the refrigerator (counterflow). Is it correct? The classical theory of heat exchangers states that counter-flow heat exchangers are more efficient than direct-flow ones. This can be illustrated with a picture.

Figure a shows a direct-flow heat exchanger, figure b shows a counter-flow one. As can be seen from the temperature graphs, with counterflow, the temperature of the hot coolant A at the outlet is lower (point Y), and cold coolant B is higher (point Z) than with forward flow. This fact is explained by the fact that in a direct-flow heat exchanger, the temperatures of the heat carriers equalize to some average value, and in a counterflow heat exchanger, the temperature of the hot heat carrier approaches the temperature of the cold one and vice versa. The temperature delta (heat flow) is greater in the case of a counterflow heat exchanger. Accordingly, the efficiency of the counterflow is higher, it can be made more compact (or it will be more efficient for the same dimensions). Everything seems to be clear.

But, as always, from general rule there are exceptions. In this case, this exception states that if the temperature of one of the heat carriers does not change continuously, but only up to a certain value (which happens during condensation or evaporation), then the heat flux at different options connections are the same. In the case of the dehumidifier, this is what happens. Our mission is to support certain temperature couple (for steam extraction- the boiling point of alcohol, for liquid - the temperature of its condensation, in fact, this is almost the same temperature). In the case of a direct cooler (in other articles, out of habit, I incorrectly call it a direct-flow refrigerator, although it can also be a counterflow one), the task is somewhat different - to condense the product and then cool it to the temperature of the cooling water, i.e. classically "heat exchanger". It turns out that the BK dephlegmator does not care how to connect, and the refrigerator needs to be connected towards.

There is one more point here. Dissolved gas is always present in water, which, when the temperature rises, tends to be released and “airing” is formed in the system, up to traffic jams. Therefore, it is more expedient to supply water to the shirt reflux condenser from below, excluding airing - the flow of water takes out air bubbles. With small ducts through the reflux condenser, one can observe the formation of an air bubble at the very top of the outlet silicone tube at the height of the process - this is it.

In this way , it is advisable to connect the water supply to the BC from below - along the way to the dephlegmator (forward flow) and towards the refrigerator (counterflow).

It has long been known that properly obtained moonshine does not give a severe hangover. It is better to clean alcohol vapors immediately during distillation than later, folk remedies. Indeed, with improper cleaning, they may not even save a ruined drink. What can contribute to the accurate separation of fractions? Each moonshine still, if it is proudly called a column, has a dephlegmator. In another way, it is also called a strengthening refrigerator. Without a reflux condenser, a metal tube rising above alembic it's just a tube. Why is it needed and what is the principle of operation of a dephlegmator in a moonshine still? Everything is very simple. Let's start with the design and location.

Moonshine dephlegmator device

The reflux condenser (reinforcing refrigerator) is something like a “water jacket” located in the upper quarter of the column. In fact, the design of the section of the column with a reflux condenser is two concentric tubes of different diameters. The outer tube is welded to the inner one, and the space between them is supplied cold water. Sometimes the reflux condenser is removable, but most often it is integrally mounted on the column itself. The dephlegmator zone does not have any internal nozzles. In this regard, the dephlegmator of a distillation column is no different from that on a conventional beer column. High performance distillation columns may not have a reflux condenser, however, it will be impossible to distill the mash on such columns: it will “clog” the nozzle, no matter what is used. Therefore, household column apparatuses have a reflux condenser for distillation “in moonshine still mode”. Therefore, when planning (we recommend choosing a device of the brand), pay special attention to the possible modes of its operation.

The principle of operation of the dephlegmator

The essence of this device is to create desired temperature for purification and strengthening of alcohol vapors due to their cooling and the so-called priority condensation.

Let's explain with an example.

In the mode of operation of the column (mash or distillation) “on itself”, there is a complete condensation of all vapors coming from the distillation cube. At this stage, the reflux condenser receives the maximum cooling flow. All condensate flows down the column towards new portions of vapor. When they meet, partial evaporation occurs due to heating of the liquid (phlegm). When the column warms up and enters the operating mode, it separates the temperature regions. In the upper part, vapors of substances with a lower boiling point will condense, and in the lower part, with a higher one. As soon as this mode is established, it is possible to reduce the cooling of the reflux condenser.

The temperature should be set in such a way as to “shift” the area of ​​evaporation of low-boiling fractions to the upper area of ​​the reflux condenser. In this case, all low-boiling fractions will begin to evaporate here and pass further into the condenser, while all other fractions will not be able to leave the column. As soon as the low-boiling fractions (heads) are selected, the temperature in the column is changed again, so that now in the same upper region of the reflux condenser the main fraction of the “body” evaporates. Thus, it is possible to separate all components of the mixture having different temperature boiling. It turns out that the reflux condenser is such a “barrier”, which can clearly separate the components of the liquid. It is only important to remember that the cooling adjustment should be made as smoothly as possible and “little by little”, since the system needs time to establish a new balance. As a rule, it takes 20-30 seconds.

Types of dephlegmators

Although the principle behind the operation of reflux condensers is the same, they may differ in design and size. The larger the contact area of ​​phlegm and steam (within certain limits), and the more accurate the temperature control, the greater will be the separating power of the reflux condenser. And there are only two designs: direct-flow and Dimroth dephlegmator. Sometimes they are confused, mixing everything into one.

A straight-through reflux condenser is just a “tube in a tube”, which was described above. And the Dimroth reflux condenser has a slightly different design. It is made in the form of a tube, inside which there is a second tube in the form of a spiral. It is in the internal that water is supplied, and here the liquid condenses. Due to the spiral shape, the contact area of ​​the liquid-vapor phases increases, and, consequently, the separation efficiency. Another plus of this design is that this phase contact occurs in the zone maximum temperature in the center of the tube. And this also contributes better cleaning alcohol vapors, even