Column flooding is possible on any column-type apparatus in distillation or rectification mode, both during the first and second distillation. The problem is complicated by the fact that devices of this design work most efficiently in pre-suffocation mode – close to the complete collapse of the system. Next, we will figure out why the column is chocking, how to identify it, eliminate it, and also use it for our own benefit.
Theory
Column flooding is an emergency situation in which the rising hot alcohol vapor does not allow the descending liquid cooled in the dephlegmator – phlegm – to pass in the opposite direction.
As a result, an emulsion plug appears in a certain place of the tsargi, where liquid and vapor are in equilibrium. Steam gradually breaks through the phlegm, seething is heard in the apparatus. At the same time, the steam pressure force is always higher than the reflux pressure, so if the cube heating power, pressure and temperature of the cooling water do not change, then the plug gradually moves up until the alcohol liquid and steam leave the column through the atmosphere connection pipe, emergency valve or sampling unit . This is the final stage of choking, in the slang of moonshiners it means that “the column began to spit.”
From the beginning of the seething to the “spitting”, the flooding of the column lasts no longer than a minute and a half, that is, everything happens relatively quickly. At the same time, you should not try to avoid “spitting” by blocking the pipe for communication with the atmosphere, the valve or the selection unit – this is fraught with an explosion!
Initially, the choke appears in the narrowest place, that is, the effect of a bottle neck is created. For example, a cork can form where a heavily compacted nozzle turns into a less dense one, or when the diameter of the drawstring narrows.
Why you should avoid choking
When the column is overflowing, the process of heat and mass transfer does not occur, therefore, there is no separation of the alcohol liquid into fractions. As a result, the moonshine obtained during the “spitting” and after it is in no way purified from harmful impurities. Therefore, the choking of the column must be eliminated and after it the apparatus should be allowed to “work for itself”.
How to determine the choking of the column
Signs of choking:
- increase in hum and vibration in the column;
- a sharp increase in temperature in the tsarga;
- pressure drops;
- a sharp ejection (“spit”) of liquid through a pipe for communication with the atmosphere, an emergency valve or a selection unit is the final stage of choke;
- in the diopter, seething is visible, resembling the active boiling of water.
It is believed that the choke can be seen and controlled through a diopter – a transparent, usually glass, part of the tsarga. But this is relevant only if the flooding of the column occurs in this particular place. If it is lower or higher, then it will be problematic to see, and even more so control it by changing the supplied heating power or cooling water temperature.
Causes of column choking and methods for their elimination
1. Heating power too high. The most common reason. In this case, the cross-sectional area of the drawer is insufficient relative to the power of the heating element and the dephlegmator, so steam and phlegm cannot be normally distributed in the volume of the drawer. The easiest way is to reduce the steam speed.
How to fix: turn off the heat when choking, wait 1,5-2 minutes for all the phlegm to go down into the cube. Turn on the heating back, but with a lower power by 3-4%. If the column choked again, then repeat the described steps.
If everything is fine, then this will be the power of the operating pre-suffocation mode of the column until such time as other important parameters of the system (pressure and temperature of the cooling water, the length and cross-sectional area of the drawer, the power of the refrigerator and dephlegmator, etc.) will not be changed . In case of changes, the column is first brought to choke, and then the pre-choke regime is again sought.
Some moonshiners solve this problem by removing excess reflux, but if there is too little reflux, then it does not cool the nozzle well, and the column does not work at 100%. It is advisable to increase the selection of phlegm only if the column choked while “working for itself” and the extra phlegm went into the selection.
2. Hypothermia of phlegm. Alcohol vapor better passes through and passes hot phlegm through itself. The optimum water temperature at the outlet of the dephlegmator is 50-60 °C. If the temperature is lower, then you need to reduce the water pressure.
3. Uneven packing of the nozzle in the side. Beginning moonshiners usually sin with this. In places of very dense packing, narrowing of the steam line is formed and a plug appears. On-load tap-changers (regular wire attachments) must not be tightly twisted and tamped. In the case of SPN (spiral-prismatic nozzles), the uniformity of the filling should be controlled. The fewer wads, the better.
4. Power surges and (or) pressure in the water supply. If the heating element is electric, then power surges change the heating power. Spontaneous change in water pressure leads to uneven cooling of the entire system.
5. Uneven installation of the column. If the column-type apparatus is not installed strictly vertically, then the phlegm begins to flow down the wall. As a result, all processes are disrupted.
6. Incorrect filling of the cube and bulk strength. The cube can be filled with a maximum of ¾ of the volume, while the strength of the filled water-alcohol mixture should not exceed 35% vol.
7. Contamination of the inside of the machine. Accumulations inside the tubes prevent the normal movement of phlegm. The apparatus must be periodically disassembled and cleaned, especially if its individual parts are used for the first and second distillation, distillation and rectification.
8. Difference in atmospheric pressure. The problem is relevant for columns with a height of more than 1,5 m. When the atmospheric pressure changes, the supplied power of the pre-suffocation mode can change by 5-10%. At the same time, it is important to take into account that atmospheric pressure changes not only with the weather, but also with altitude. For example, the operating parameters of the same apparatus in a private house and on the ninth floor of an apartment building may differ.
9. The choke of the shell-and-tube dephlegmator. It usually occurs during the second distillation, if the on-load tap-changer nozzle is pressed tightly against the bottom of the reflux condenser. The risk of flooding is higher in a reflux condenser (with an equal total area of the steam pipeline), assembled from a large number of narrow tubes.
