Out of the corner of my eye I saw on one of the forums another discussion on 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 boiler room. I have not touched on this topic before, so I decided to express 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 reflux condenser along with the steam (forward flow), and into the refrigerator in the opposite direction (counterflow). Is it correct? The classical theory of heat exchangers states that counterflow 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 heat exchanger. As can be seen from the temperature graphs, with counterflow, the temperature of 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 coolant are leveled to some average value, and in a counter-flow heat exchanger the temperature of the hot coolant approaches the temperature of the cold one and vice versa. The temperature delta (heat flow) in the case of a counterflow heat exchanger is larger. Accordingly, the efficiency of the counterflow is higher; it can be made more compact (or it will be more effective with the same dimensions). Everything seems clear.
But, as always, from general rule there are exceptions. IN in this case this exception states that if the temperature of one of the coolants does not change continuously, but only up to certain value(which happens during condensation or evaporation), then the heat flow at different options connection becomes the same. This is what happens in the case of a reflux condenser. Our task is to maintain a certain temperature of the steam (for steam extraction - the boiling point of alcohol, for liquid - the temperature of its condensation, in fact, this is practically the same temperature). In the case of a direct-flow refrigerator (in other articles, out of habit, I incorrectly call it direct-flow, although it can also be counter-flow), the task is somewhat different - to condense the product and then cool it to the temperature of the cooling water, i.e. classically “heat exchange”. It turns out that the reflux condenser BC does not matter how to connect it, but the refrigerator needs to be connected opposite.
There is one more point here. There is always a dissolved gas in water, which tends to be released when the temperature rises and “airing” forms in the system, even causing plugs. Therefore, it is more expedient to supply water to the jacket reflux condenser from below, eliminating airing - the flow of water removes air bubbles. With small flows through the reflux condenser, you 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.
Thus , it is advisable to connect the water supply to the BC from below - simultaneously into the reflux condenser (forward flow) and towards the refrigerator (counterflow).
It has long been known that properly prepared moonshine does not give a severe hangover. It is better to purify alcohol vapors immediately during distillation rather than later. folk remedies. After all, if cleaned incorrectly, they may not even be able to save the ruined drink. What can help to accurately separate fractions? Each moonshine still, if it is proudly called a column, has a reflux condenser. In another way it is also called a strengthening refrigerator. Without a reflux condenser, the metal tube rising above the still is just a tube. Why is it needed and what is the principle of operation of the reflux condenser in a moonshine still? Everything is very simple. Let's start with the design and location.
Moonshine reflux condenser device
The reflux condenser (strengthening refrigerator) is something like a “water jacket” located in the upper quarter of the column. Essentially, the design of the column section 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 permanently mounted on the column itself. The reflux condenser zone does not have any internal attachments. In this regard, the reflux condenser of a distillation column is no different from that of a conventional mash column. Highly efficient distillation columns may not have a reflux condenser, but it will be impossible to distill the mash on such columns: it will “clog” the nozzle, no matter which one is used. Therefore, household column devices They have a reflux condenser for distillation “in moonshine still mode.” Therefore, when planning (we recommend choosing a brand device), pay attention Special attention on possible modes of its operation.
Operating principle of the reflux condenser
The essence of this device is to create desired temperature for purification and strengthening of alcohol vapors due to their cooling and so-called priority condensation.
Let's explain with an example.
In the self-propelled operation mode of the column (mash or distillation), complete condensation of all vapors coming from alembic. At this stage, the maximum cooling flow is supplied to the reflux condenser. All condensate flows down the column towards new portions of vapor. When they meet, partial evaporation occurs due to heating of the liquid (reflux). When the column warms up and enters operating mode, a separation of temperature regions occurs in it. Vapors of substances with a lower boiling point will condense in the upper part, and vapors with a higher boiling point in the lower part. As soon as this mode is established, the cooling of the reflux condenser can be reduced.
The temperature must 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 condensing refrigerator, while all other fractions will not be able to leave the column. Once the low-boiling fractions (heads) are selected, the temperature in the column changes again, so that now the main fraction of the “body” evaporates in the same upper region of the reflux condenser. In this way, it is possible to separate all components of the mixture that have different temperatures boiling. It turns out that the reflux condenser is a “barrier” that can clearly separate the components of the liquid. It is only important to remember that cooling adjustments should be made as smoothly and “little by little” as possible, since the system needs time to establish a new equilibrium. Typically this takes 20-30 seconds.
Types of reflux condensers
Although the operating principle of reflux condensers is the same, they may differ in design and size. The larger the contact area between reflux and steam (within certain limits), and the more precise the temperature control, the greater the separation capacity of the reflux condenser. And there are only two designs: direct-flow and Dimroth reflux condenser. Sometimes they are confused, mixing everything into one.
A direct-flow dephlegmator is exactly the “tube in a tube” that was described above. But the Dimroth reflux condenser has a slightly different design. It is made in the form of a tube, inside of which there is a second tube in the form of a spiral. It is into the internal one 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 advantage of this design is that this phase contact occurs in the zone of maximum temperature - in the center of the tube. And this also helps better cleaning alcohol vapors, even
However, despite the widespread use of these names, if you analyze the numerous information on the Internet, then there is widespread confusion regarding the purpose of these devices. There are especially many discrepancies in the functions and essence of the operation of the reflux condenser and the steam boiler. Let's figure it out and start with the basics.
Rectification and distillation
Distillation- This is evaporation followed by condensation of vapor. This is exactly what happens when using the simplest type of moonshine still.
Rectification- separation of the mixture into fractions due to the countercurrent movement of steam and the same steam condensed into liquid (reflux).
Thus, it can be seen that during distillation, the steam formed during boiling of the liquid flows directly to the condenser. As a result, we get a homogeneous mixture containing alcohol, water, and fusel oils. The alcohol content increases due to the fact that it evaporates at higher temperatures. low temperatures and faster than water and other fractions.
During rectification, part of the condensed steam flows back towards the distillation tank, is heated by the newly formed steam and evaporates again many times. As a result of the process of re-evaporation, the distilled liquid is divided into its component parts. In the case of moonshine: fusel oils, water and the alcohol we need. The degree of separation depends on the design of the distillation column.
Looking ahead a little, let's say that a reflux condenser for a moonshine still is one of the elements included in the design of a distillation column.
Dry steamers and wet steamers
Actually, these are two names for the same element. They are also known as cubs. Both the steam steamer and the wet steamer are structurally a thin-walled closed container of small volume with two steam lines in the upper part: inlet and outlet.
A tap is embedded in the lower part of the diving board for discharging waste condensate. However, bite-cups are often made from glass jars, then, naturally, there can be no talk of a crane. The accumulated liquid is drained through the neck and only after the distillation is completed.
A simple steamer from a can
There is one structural difference between a wet and dry steamer: in a wet steamer, the outlet of the inlet pipe is lowered to the very bottom, so that the steam from the distillation cube “gurgles” through the liquid poured into the container. Hence, a wet steamer is often called a bubbler.
How it works
- Steam enters the container and, due to the temperature difference, begins to condense on the walls and flow to the bottom.
- As the steam boiler body heats up with new steam, the intensity of condensation decreases, and part of the steam begins to escape.
- At the same time, the condensate begins to heat up and evaporate and also goes into extraction.
- At a certain point, due to re-evaporation, there is only “dirty” phlegm at the bottom, which is better to dump through the tap and start the cycle from the beginning.
- If there is no tap, then there is only one option - selection before flushing, i.e. At the exit we get a “dirty” product.
Both the “reset” and “selection to victory” options are not good - the end result will still not be the highest quality product. In fact, the steamer performs only two useful functions:
- prevents mash pairs from being selected;
- due to re-evaporation, it slightly increases the strength of the product.
Is it possible to improve the efficiency of the bite? It is possible, but it is necessary to change its structure: the body should be located above the distillation cube, and the condensate should be discharged directly into the cube. Only this will no longer be a dry steam tank, but a quite decent uncontrolled reflux condenser.
How does a reflux condenser work?
The reflux condenser device in its simplest form is two welded tubes of different diameters installed vertically on a distillation cube. Coolant (water) circulates in the jacket between them, and a smaller diameter tube serves as a pipeline for the release of alcohol-containing steam.
To explain the principle of operation of this device, let us conventionally assume that the distilled liquid has 2 components, having different temperatures boiling. The division into fractions is carried out as follows:
- At the initial stage, cooling starts at full power and until the distillation cube is heated, the apparatus works “on itself.” That is, the liquid evaporating from the container condenses, forms a thin film on the walls and flows towards the rising steam back into the cube. On its way, it is heated by the newly formed steam and partially evaporates - this is “re-evaporation”
- After the temperature in the container reaches a temperature sufficient for both fractions to boil, two areas form inside the structure:
- The upper one, where vapors of the fraction with a low boiling point condense.
- The lower one is the region of condensation of the second component.
- Nothing is still getting into the main refrigerator, that is, there is no selection yet.
- The evaporation and condensation temperatures of each fraction are known. Now you can change the cooling mode so that the evaporation point of the first fraction is at the upper edge of the reflux condenser.
- The selection of the first component of the mixture begins.
- After the low-temperature fraction is selected, the mode is changed again and the second part of the mixture is selected.
The method allows you to separate a liquid into any number of components having different boiling points. The process is inertial, and it is better to change the cooling mode very carefully, slowly and stepwise.
Dimroth reflux condenser
The separating ability of the reflux condenser depends on the size of the contact area between the reflux condenser and the steam and the accuracy of the adjustment. The principle of operation is the same for all types of these devices; they differ only in design.
The one that was described in the previous section is a direct-flow film-type refrigerator. The design is simple to manufacture and quite effective. But it has disadvantages - a small interaction area, which generally tends to zero when the structure deviates from the vertical. The second is the difficulty of adjusting the steam temperature. The Dimroth design is partially devoid of these shortcomings.
The Dimroth reflux condenser is a glass or metal flask with a spiral tube in the center. Water circulates through it and phlegm condenses on it.
The principle of operation is the same, but it is obvious that such a design, even by eye, has a larger contact area between steam and liquid than a film apparatus. In addition, the interaction of phlegm and steam occurs in the center of the flask, where its temperature is maximum. Consequently, the resulting product will be cleaner and stronger.
Why is a Dimroth reflux condenser or a film reflux condenser for a moonshine still most often used in everyday life? This is due to the properties of the raw material - mash. If, when distilling it, you use the most efficient packed column with large area filler, then after half an hour of work the filler will become so contaminated that any rectification will become impossible.