How to make a distillation column – calculation of system parameters

Sooner or later, almost every homemade alcohol lover thinks about purchasing or manufacturing a distillation column (RK) – a device for obtaining pure alcohol. You need to start with a comprehensive calculation of the basic parameters: power, height, drawer diameter, cube volume, etc. This information will be useful both for those who want to make all the elements with their own hands, and for those who are going to buy a ready-made distillation column (it will help you make a choice and check the seller). Without affecting the design features of individual nodes, we will consider the general principles for building a balanced system for rectification at home.

Characteristics of the pipe (tsargi) and nozzles

Материал. The pipe largely determines the parameters of the distillation column and the requirements for all units of the apparatus. The material for the manufacture of the side is chromium-nickel stainless steel – “food” stainless steel.

Due to chemical neutrality, food grade stainless steel does not affect the composition of the product, which is required. Raw sugar mash or distillation waste (“heads” and “tails”) are distilled into alcohol, therefore the main purpose of rectification is to maximize the purification of the output from impurities, and not change the organoleptic properties of alcohol in one direction or another. It is inappropriate to use copper in classic distillation columns, since this material slightly changes the chemical composition of the drink and is suitable for the production of a distiller (ordinary moonshine still) or a beer column (a special case of rectification).

Thickness. The drawer side is made of stainless steel pipe with a wall thickness of 1-1,5 mm. A thicker wall is not needed, as this will increase the cost and weight of the structure without obtaining any advantages.

Nozzle options. It is not correct to talk about the characteristics of the column without reference to the packing. When rectifying at home, nozzles with a contact surface area of ​​1,5 to 4 square meters are used. m/liter. With an increase in the area of ​​the contact surface, the separating ability also increases, but the productivity decreases. Reducing the area leads to a decrease in the separating and strengthening ability.

The productivity of the column initially increases, but then, to maintain the strength of the output, the operator is forced to lower the selection rate. This means that there is a certain optimal size of the packing, which depends on the diameter of the column and will allow you to achieve the best combination of parameters.

The dimensions of the spiral prismatic packing (SPN) should be less than the inner diameter of the column by about 12-15 times. For a pipe diameter of 50 mm – 3.5×3.5×0.25 mm, for 40 – 3x3x0.25 mm, and for 32 and 28 – 2x2x0.25 mm.

Depending on the tasks, it is advisable to use different nozzles. For example, when obtaining fortified distillates, copper rings with a diameter and height of 10 mm are often used. It is clear that in this case the goal is not the separating and strengthening ability of the system, but a completely different criterion – the catalytic ability of copper to eliminate sulfur compounds from alcohol.

You should not limit your arsenal to one, even the best nozzle, there are simply no such ones. There are the most suitable for each specific task.

Even a small change in the column diameter seriously affects the parameters. To evaluate, it is enough to remember that the nominal power (W) and productivity (ml / h) are numerically equal to the cross-sectional area of ​​​​the column (sq. mm), and therefore are proportional to the square of the diameter. Pay attention to this when choosing a drawer, always consider the inner diameter and compare options using it.

Dependence of power on pipe diameter

Pipe height. To ensure good holding and separation capacity, regardless of the diameter, the height of the distillation column should be from 1 to 1,5 m. If it is less, there will not be enough space for the fusel oils accumulated during operation, as a result, the fusel oil will begin to break into the selection. Another drawback is that the heads will not be clearly divided into fractions. If the pipe height is greater, this will not lead to a significant improvement in the separating and holding capacity of the system, but will increase the driving time, as well as the number of “heads” and “headrests”. decreases. The effect of increasing the pipe from 50 cm to 60 cm is an order of magnitude higher than from 140 cm to 150 cm.

The volume of the cube for the distillation column

In order to increase the yield of high-quality alcohol, but to prevent overfilling of the fusel column, the bulk (filling) of raw alcohol in the cube is limited in the range of 10-20 packing volumes. For columns 1,5 m high and 50 mm in diameter – 30-60 l, 40 mm – 17-34 l, 32 mm – 10-20 l, 28 mm – 7-14 l.

Taking into account the filling of the cube by 2/3 of the volume, a 50-40 liter container is suitable for a column with an internal diameter of a tsarga of 80 mm, a 40-30 liter container for 50 mm, a 32-20 liter cube for 30 mm, and a pressure cooker for 28 mm.

When using a cube with a volume closer to the lower limit of the recommended range, you can safely remove one drawer and reduce the height to 1-1,2 meters. As a result, there will be relatively little fuselage for a breakthrough in the selection, but the volume of “head restraints” will noticeably decrease.

Source and power of column heating

Plate type. The moonshine past haunts many beginners who believe that if they previously used a gas, induction or conventional electric stove to heat the moonshine, then you can leave this source for the column.

The rectification process is significantly different from distillation, everything is much more complicated and the fire will not work. It is necessary to ensure smooth adjustment and stability of the supplied heating power.

Electric stoves operating on a thermostat in start-stop mode are not used, because as soon as a short-term power outage occurs, the steam will stop going into the column, and the phlegm will collapse into a cube. In this case, you will have to start rectification again – with the work of the column for yourself and the selection of “heads”.

An induction cooker is an extremely rough apparatus with a step change in power of 100-200 W, and during rectification, you need to change the power smoothly, literally by 5-10 W. Yes, and it is unlikely that it will be possible to stabilize the heating, regardless of the voltage fluctuation at the input.

A gas stove with 40% raw alcohol poured into a cube and a 96-degree product at the outlet is a mortal danger, not to mention fluctuations in the heating temperature.

The optimal solution is to embed a heating element of the required power into the cube, and for adjustment use a relay with output voltage stabilization, for example, RM-2 16A. You can take analogs. The main thing is to get a stabilized voltage at the output and the ability to smoothly change the heating temperature by 5-10 watts.

Power supplied. In order to heat the cube in an acceptable time, one must proceed from a power of 1 kW per 10 liters of raw alcohol. This means that for a 50 l cube filled with 40 liters, a minimum of 4 kW is required, 40 l – 3 kW, 30 l – 2-2.5 kW, 20 l – 1.5 kW.

With the same volume, cubes can be low and wide, narrow and high. When choosing a suitable container, it should be taken into account that the cube is often used not only for rectification, but also for distillation, therefore, they proceed from the most severe conditions so that the input power does not lead to rapid foaming with splashes from the cube into the steam pipeline.

It has been experimentally established that at a heating element placement depth of about 40-50 cm, normal boiling occurs if per 1 sq. cm bulk mirrors account for no more than 4-5 watts of power. With a decrease in depth, the allowable power increases, and with an increase, it decreases.

There are other factors that affect the nature of boiling: the density, viscosity and surface tension of the liquid. It happens that emissions occur at the end of the mash distillation, when the density increases. Therefore, conducting the rectification process at the border of the permitted range is always fraught with trouble.

Common cylindrical cubes have a diameter of 26, 32, 40 cm. Based on the allowable power for the surface area of ​​​​the cube bulk mirror of 26 cm, the cube will work normally with a heating power of up to 2,5 kW, for 30 cm – 3.5 kW, 40 cm – 5 kW .

The third factor that determines the heating power is the use of one of the tsarg columns without a nozzle as a dry steamer to combat splashing. To do this, it is necessary that the steam velocity in the pipe does not exceed 1 m/s, at 2-3 m/s the protective effect weakens, and at high values, the steam will drive the phlegm up the pipe and throw it into the selection.

Formula for calculating steam speed:

V u750d N * XNUMX / S (m / s),

where:

• N – power, kW;
• 750 – vaporization (cub. cm / sec kW);
• S is the cross-sectional area of ​​the column (sq. mm).

A pipe with a diameter of 50 mm will cope with spray when heated up to 4 kW, 40-42 mm – up to 3 kW, 38 – up to 2 kW, 32 – up to 1,5 kW.

Based on the above considerations, we select the volume, cube dimensions, heating and distillation power. All these parameters are coordinated with the diameter and height of the column.

Calculation of the parameters of the dephlegmator of the distillation column

The power of the reflux condenser is determined depending on the type of distillation column. If we are building a column with liquid extraction or steam below the reflux condenser, then the required power must not be less than the rated power of the column. Usually in these cases, a Dimroth refrigerator with a utilization power of 4-5 watts per 1 sq. see surface.

If the steam extraction column is higher than the reflux condenser, then the calculated capacity is 2/3 of the nominal one. In this case, you can use Dimroth or “shirt”. The utilization power of the shirt is lower than that of the dimroth and is about 2 watts per square centimeter.

Further, everything is simple: we divide the rated power by the utilization one. For example, for a column with an inner diameter of 50 mm: 1950/5= 390 sq. cm area of ​​Dimroth or 975 sq. see shirt. This means that the Dimrot refrigerator can be made from a 6×1 mm tube 487 / (0.6 * 3.14) = 2.58 cm long for the first option, taking into account the safety factor of 3 meters. For the second option, we multiply by two thirds: 258 * 2/3 = 172 cm, taking into account the safety factor of 2 meters.

Column shirt 52 x 1 – 975 / 5.2 / 3.14 u59d 2 cm * 3/39 uXNUMXd XNUMX cm. But this is for rooms with high ceilings.

Calculation of a once-through refrigerator

If the straight-through is used as an aftercooler in a distillation column with liquid withdrawal, then choose the smallest and most compact option. Enough power is 30-40% of the nominal power of the column.

A direct-flow refrigerator is made without a spiral in the gap between the jacket and the inner pipe, then the selection is started into the jacket, and the cooling water is supplied through the central pipe. In this case, the shirt is welded onto the water supply pipe to the dephlegmator. This is a small “pencil” about 30 cm long.

But if the same straight-through is used both for distillation and for rectification, being a universal unit, they do not proceed from the need of the Republic of Kazakhstan, but from the maximum heating power during distillation.

To create a turbulent steam flow in the refrigerator, which allows for a heat transfer rate of at least 10 watts / sq. cm, it is necessary to provide a steam speed of about 10-20 m / s.

The range of possible diameters is quite wide. The minimum diameter is determined from the conditions of not creating a large overpressure in the cube (no more than 50 mm of water column), but the maximum by calculating the Reynolds number, based on the minimum speed and maximum coefficient of kinematic viscosity of vapors.

In order not to go into unnecessary details, here is the most common definition: “In order for the turbulent mode of steam movement to be maintained in the pipe, it is sufficient that the inner diameter (in millimeters) be no more than 6 times the heating power (in kilowatts).”

Recommended steam pipe diameters

To prevent the water jacket from airing, it is necessary to maintain a linear water velocity of at least 11 cm / s, but an excessive increase in speed will require high pressure in the water supply. Therefore, the range from 12 to 20 cm/s is considered optimal.

To condense the steam and cool the condensate to an acceptable temperature, water must be supplied at 20°C at a rate of about 4.8 cc/s (17 liters per hour) for every kilowatt of power input. In this case, the water will heat up by 50 degrees – up to 70 ° C. Naturally, less water will be needed in winter, and when using autonomous cooling systems, about one and a half times more.

Based on the previous data, the annulus cross-sectional area and the inside diameter of the jacket can be calculated. It is necessary to take into account the available assortment of pipes. Calculations and practice have shown that a gap of 1-1.5 mm is quite sufficient to meet all the necessary conditions. This corresponds to pairs of pipes: 10×1 – 14×1, 12×1 – 16×1, 14×1 – 18×1, 16×1 – 20×1 and 20×1 – 25×1.5, which cover the entire power range used at home.

There is another important detail of the straight-through – a spiral wound on a steam pipe. Such a spiral is made of wire with a diameter that provides a gap of 0.2-0.3 mm to the inner surface of the shirt. It is wound with a step equal to 2-3 diameters of the steam pipe. The main purpose is to center the steam pipe, in which, during operation, the temperature is higher than in the jacket pipe. This means that as a result of thermal expansion, the steam pipe lengthens and bends, leaning against the jacket, dead zones appear that are not washed by cooling water, as a result, the efficiency of the refrigerator drops sharply. Additional advantages of spiral winding are the lengthening of the path and the creation of turbulence in the cooling water flow.

A well-made straight-through can utilize up to 15 watts / sq. cm of the heat exchange area, which is confirmed by experience. To determine the length of the cooled part of the direct flow, we use a rated power of 10 W / sq. cm (100 sq. cm / kW).

The required heat exchange area is equal to the heating power in kilowatts multiplied by 100:

S = P * 100 (sq. cm).

Steam pipe outer circumference:

Lокр = 3.14 * Д.

Cooling jacket height:

H = S / Lокр.

General calculation formula:

H = 3183 * P / D (power in kW, height and outer diameter of the steam pipe in millimeters).

An example of the calculation of a straight pipe

Heating power – 2 kW.

It is possible to use pipes 12×1 and 14×1.

Cross-sectional areas – 78,5 and 113 square meters. mm.

Steam volume – 750 * 2 u1500d XNUMX cubic meters. cm / s.

Steam velocities in pipes: 19,1 and 13,2 m/s.

The 14×1 pipe looks preferable, as it allows you to have a power margin, while remaining in the recommended steam speed range.

The steam pipe for the shirt is 18×1, the annular gap will be 1 mm.

Water supply rate: 4,8 * 2= 9.6 cm3/s.

Annular gap area – 3.14 / 4 * (16 * 16 – 14 * 14) = 47.1 sq. mm = 0,471 sq. cm.

Linear speed – 9.6 / 0.471 = 20 cm/s – the value remains within the recommended limits.

If the annular gap were 1,5 mm – 13 cm / s. If 2 mm, then the linear speed would drop to 9.6 cm / s and water would have to be supplied above the nominal volume, solely so that the refrigerator does not air up – a waste of money.

Shirt height – 3183 * 2 / 14 = 454 mm or 45 cm. The safety factor is not needed, everything is taken into account.

Result: 14×1-18×1 with a height of the cooled part 45 cm, nominal water flow – 9.6 cubic meters. cm/s or 34.5 liters per hour.

With a rated heating power of 2 kW, the refrigerator will produce 4 liters of alcohol per hour with a good margin.

An efficient and balanced straight-through distillation should have a ratio of extraction rate to heating power and water consumption for cooling 1 liter / hour – 0,5 kW – 10 liters / hour. If the power is higher, there will be large heat losses, if it is small, the useful heating power will decrease. If the water flow is higher, the direct flow is inefficiently designed.

The distillation column can be used as a wash column. The equipment for the beer columns has its own characteristics, but the second distillation differs mainly in technology. For the first distillation, there are more features and individual nodes may not be applicable, but this is a topic for a separate discussion.

Based on real household needs and the existing range of pipes, we will calculate typical options for a distillation column using the above method.

PS We express our gratitude for the systematization of the material and assistance in preparing the article to the user of our forum IgorGor.