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meerkat

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  1. To move the apparent ABV from a true value of 42.52% down to the 41.97% that you are reading would require only 0.26 mass % of sugar/solids. The only way to be sure of what is happening is to do as Silk City has recommended and do the evaporation test. This will tell you the quantity of solids present. If your column was sufficiently overloaded to carry over that quantity of sugar you would not achieve any rectification at all, so I believe you can rule out sugar from distillation being the cause. If there are solids present they would have to be leached out from the maturation barrels, but I don't have the experience to judge whether this is possible. Anyway, the first step must be to determine if there are solids present, and then the next step will be to track down the source. A word on the results from the external lab. The top-of-the-range digital density meters sometimes incorporate a refractometer and with some fancy math the density and RI can be combined to give you the alcohol and sugar content. But this is not very accurate and is not accepted by the TTB. Is you external lab doing it this way, or with a proper TTB approved lab distillation?
  2. There is not enough information to comment meaningfully. Was the external lab's ABV higher or lower than yours? Have you given any other samples to this lab where their readings match yours? (in other words - do you trust this lab? if so, why?). What analysis method did the external lab use? If they were compensating for obscuration by solids, did they report any solids levels? If the SNAP 50 does not compensate adequately for temperature, a high temperature sample would have the opposite effect to dissolved solids. High temperature decreases the density of the sample, while dissolved solids increase the density. Does 18 months of aging usually change the ABV? In which direction? Are the readings you are getting now similar to the ABV changes you have seen in the past?
  3. @Birster If each column has its own drain line with the discharge end below the liquid surface in the pot then the siphon-break holes are not required. This arrangement will prevent vapor traveling between the column bases and the U-bend seals are therefore also not required. Without the U-bend seals there is nothing to siphon out. Doing away with the seals also makes the piping easier to flush and drain. The extra expense of the separate lines does make for a nicer system.
  4. ViolentBlue and I were replying at the same time so I did not see his reply before I hit "submit". It is true that for optimum energy efficiency the bottoms from a column should be pumped as reflux to the top of the previous column. It is always done this way in large commercial distilleries. However, it is common in craft distilleries to drain the bottoms from each column directly back to the pot and each column generates its own reflux by using a deflegmator built into the top of the column. This works just fine, and maybe even adds a bit of flexibility, even if it is a bit less energy efficient.
  5. It is very common for them to share a common return line. However, it is important that vapor cannot travel from one column to another via this line. This seal can be made by using a U bend or a P-trap (but not an S trap). The return line must also not cause a siphon which would pull all the liquid from the return line. The siphon is usually prevented by making sure that the return line is big enough to never run full and by drilling a small (approx 3 mm) hole in the return line inside the pot above the bulk liquid level.
  6. I accept that the time taken for water addition can affect the taste and appearance of the product, but I doubt that this is because of any chemical reactions taking place with the water. I know through personal experience, as well as from studying the theory, that some of the cogeners are not soluble in water. If you add the water too quickly there will be zones in the mixing vessel where the cogeners are in contact with high concentrations of water and very little alcohol. The oils can form emulsions that cause haze and taste concentrations, and these emulsions are extremely difficult to get back into solution. In his book "Distillery Operations" Payton Fireman refers to a blending operation where he weighed out the required quantity of water and then added the whiskey to it. The batch was ruined and had to be entirely re-distilled. The first whiskey to enter the water would have quickly become highly diluted, exactly as I have described above, and the oils would have come out of solution. So I don't believe the problem is a chemical reaction that is happening over time. It seems to me to be a physical phenomenon where the oils are "squeezed" out of the alcohol and impact the appearance and taste. This physical phenomenon would be dependent not so much on the time that it takes to add the water, but rather the local rate at which it was added. Ideally the water should be added via a sparger where there will be many zones of low water concentration during mixing, rather than only one zone of much higher water concentration. The blend should be stirred during the entire operation. If my understanding is correct, the reason for better tasting products being produced when the dilution is done over a long period would be because the rate at which the water was added was much lower than when it was done quickly. It would be interesting to hear from @JustAndy whether the water was added at a lower rate when it was done over weeks rather than over one or two days.
  7. It is important to remember that the temperature is not an independent variable that we can set arbitrarily. The temperatures in the table I posted earlier are boiling point temperatures and are fixed by the composition of the boiling liquid. The only way to change the boiling point for a given concentration is to change the pressure, but I am assuming here that everything is being done at normal atmospheric pressure. Let me take the data from the 4th row in the table as an example and assume you have material from a previous stripping run at 32.26 %ABV. If you put this in a pot still and start heating it, the temperature will rise but it will not boil until the temperature reaches 85.3°C. Spirit at this composition can only be distilled at 85.3°C and at any lower temperature there will be no boiling and therefore no distillation. If you continue heating the pot and boiling the spirit the boiling point will slowly rise as the concentration of the ethanol in the pot decreases - because more ethanol than water has been removed by distillation. The new temperature is just an indicator of the new composition in the pot, and cannot be increased (or decreased) arbitrarily while maintaining boiling. Even when we use reflux on a column to "control the temperature" we are not truly controlling the temperature as an independent variable. Changing the reflux rate changes the composition in the column and the measured temperature is just an indication of that changed composition. The measured temperature can be used to interpolate the data in my table to work out what the actual composition is because we know it is at its boiling point. We are all guilty of talking of controlling the temperature, but strictly that is not true. The temperature is just a proxy for the composition. We could take this analogy a step further and say we do not really even measure the temperature. Just as we have no direct way to measure the composition inside the column, we actually have no way to directly measure its temperature. We measure the length of a column of mercury in a pencil thermometer (or the resistance of an RTD probe) and from this length (or resistance) we infer a temperature. And in turn from this inferred temperature we infer a composition. I have heard of distillers preferring "slow distillation" but have no direct experience of this myself. True distillation is not impacted by the rate at which it occurs (as long as the column is still operating properly) so if the taste/smell of the product changes with the rate of distillation there is some other phenomenon occurring. We know that in alcohol distillation there are some chemical reactions going on - particularly between any sulfur compounds and the copper - so I can accept that the rate at which a product is distilled can affect its quality but it is not the distillation itself that is having that effect.
  8. In general, mixtures of two liquids will boil at temperatures between the boiling points of the two pure liquids and the boiling point will vary with the concentration. The ethanol-water mixture is a bit different in that it forms an azeotrope. From the first sentence above we would expect the boiling point (at atmospheric pressure) of a mixture of ethanol and water to be between 100°C (boiling point of pure water) and 78.37°C (boiling point of pure ethanol). In most cases this is true. However, a mixture containing 95.58 mass % ethanol will boil at 78.15°C, which is lower than the boiling point of pure ethanol. This is called the azeotrope. To really split hairs, it is called a minimum boiling azeotrope because you can also get maximum boiling azeotropes where the boiling point of the mixture is higher than either of the pure boiling points. The existence of the azeotrope is why we cannot achieve 100% ethanol by normal distillation. The lowest temperature occurs at the top of the column and for ethanol-water this would be the azeotrope temperature of 78.15°C and no matter how much taller you made the column you could never go beyond the 95.58 mass % concentration. I have attached a table of boiling point data. In addition to showing the boiling point at various liquid concentrations it also shows the composition of the vapour that is generated. Between 100°C and the azeotrope ethanol is more volatile than water and there will be a higher concentration of ethanol in the vapour than was in the boiling liquid. If this were not so, distillation columns would not work. The "VLE" in the title on the attachment stands for Vapour Liquid Equilibrium - sorry for the jargon. Carey and Lewis MF Mass and ABV.pdf
  9. For a column of 300 mm ID you definitely do not want to go for the split flow design you have shown. It is unnecessarily complex and restricts the bubbling area. I have seen single pass trays of 2 m diameter working very well, even back in the days of bubble caps. I have never seen a downcomer with perforations at the bottom. You want the flow down the downcomer to be as unimpeded as possible, especially if the liquid is not totally clear. I would leave the bottom of the DC totally open. The residence time is calculated as DC volume divided by volumetric flowrate. Your flowrate of 480 l/h (actually a bit less because some goes out as vapor) is equivalent to 0.000133 m3/s going down the DC and for an 80 mm ID pipe 300 mm long the volume of the DC is 0.0015 m3. If you divide m3 by m3/s the m3 cancels and you are left with seconds, so that is why it is called a residence time. Here we get 11.3 seconds - a nice safe number. The downcomer does not run full. Typically the level in the downcomer would be 30 to 50 % of the tray spacing. So the true time that the liquid spends in the downcomer is 3 to 5 seconds, but this is enough for the bubbles to disengage, thus avoiding vapor being carried downwards when it should be going upwards. The reason the level in the downcomer backs up is because the pressure on any tray has to be a bit higher than on the tray above it to force the vapor up through the tray and this pressure holds the liquid in the downcomer back. There is also a small pressure drop as the liquid flows under the downcomer and onto the tray. The diagram below, from Peters and Timmerhaus, shows a variety of different tray types but I like these simple downcomers Here they have shown segmental downcomers where the column shell forms the outer part of the downcomer but this is difficult to fabricate in smaller columns and it is more usual to weld a pipe or D section into the tray to achieve the all-round seal. A very important aspect shown in this diagram is the sealing of the bottom downcomer in the base of the column. For a tray to function properly the vapor must not flow up any of the downcomers. The bottom tray seals first and then the seal is achieved in turn on each higher tray until all the DCs are sealed. Imagine the column at start-up with the bottom DC sealed by the liquid in the pot. When boiling starts in the pot the vapor cannot flow up the bottom DC and it flows up through the perforations in the first tray. The bottom of the DC from the 2nd tray will not be sealed with liquid yet and vapor will flow up this DC, as well as through the perforations of the second tray. But because the vapor flowing up through the bottom tray prevents any liquid from weeping through the holes the liquid will accumulate on the bottom tray until it can overflow the weir into the downcomer. As long as the downcomer projects above the tray more than the gap between the tray and the bottom of the DC from tray 2, when the liquid gets to a height sufficient to overflow into the downcomer it will have sealed the bottom of the next downcomer. Now all the vapor from tray 1 goes through the perforations in tray 2 and the same process allows the next downcomer to achieve its seal. 30 mm is a reasonable height for the weirs, but maybe a bit on the high side. They cannot be too low because (as explained above) they must be higher than the gap at the bottom of the downcomer so that the tray can seal the bottom of the DC. The higher the weir, the higher the liquid level will be on the tray. The higher this level the higher the efficiency of the tray, but also the more easily the tray will weep. It's all a trade-off between the competing factors.
  10. @Modernity I would be wary of using perforated trays if you are going to be distilling grain in. If you are going to make the trays into a removable cassette then that could work if you need to clean them. Maybe wait for @PeteB to post his photos and diagrams to see how he did it. He and I discussed using very simple splash trays before he built his first column, and he came up with a very innovative way of installing the trays but I have not seen what he finally built. If you do go with the perforated trays be generous with your downcomer sizing. I like to allow a downcomer residence time of 10 seconds, based on the full volume of the downcomer. If your tray spacing is around 300 mm then it would be better to install a 3” downcomer. I also prefer D shaped downcomers. You can make these easily by splitting a 6” pipe in half longitudinally and then welding in a plate to seal the straight part of the D. Half a 6” pipe has double the area of a 3” pipe, but is still only 3” wide. Some references for downcomer design also specify a maximum velocity, but this only comes into play with large hydrocarbon columns that can have +3 ft tray spacings. The hole area (perforations) is much harder to calculate. I found this reference that states % Hole Area: This is the ratio of hole area to bubbling area. The default practice is to target a hole area of 8 to 10 % of bubbling area for pressure services. The acceptable range for percentage hole area is 5 % to 15 %. However for some critical services, we can go % hole area up to 17-17.5 % provided that weeping is under control. Hole areas below 5 % are not used. Despite their claim that hole areas of less than 5 % are not used I designed a column that uses 2.9 % and has been running very stably 24/7 for 33 years. That column was a bit unusual in that it had a very high liquid to vapor ratio and I had a lot of pressure drop to play with. For your stripper you will also have a relatively high liquid to gas ratio and I would guess that it will need 6 to 8 % open area, but that really is just a guess. If the hole area is too small it will unnecessarily limit the capacity of the column, and if the hole area is too large the trays will weep and their separation power will be low. Rather than taking the risk of deciding on the hole area yourself it might be better to buy trays from a supplier with a track record and who offers a guarantee. (I am not touting for business – I do not supply equipment or consulting services.)
  11. @John Bassett Yes, that is correct. The final product should have an apparent proof of 157.8 if its true proof is 160.
  12. This post is just to pull this thread to the top again. I have made an edit to the obscuration factor that I had calculated above for glycerol and I would like anyone who has used the old number to be aware of the change. @John Bassett @CalwiseSpirits @Jedd Haas @DrDistillation @SCLabGuy
  13. @SCLabGuy - I am happy to share the calculations for the obscuration numbers, but I doubt whether many would be interested to see them here. They are hand-written and I will send you a scan if you write to me at the support address given in my software. The calculations in AlcoDens LQ are based on hard data and not on theoretical calculations. This is important for the contraction calculations, which are totally neglected in the simple obscuration estimates I have done for the glycerol. I would be reluctant to add untested calculations into the software. And I get too many people saying that the software needs to be simplified for me to go the other way and add in extra complications and options. Thanks for the pointer to the FDA guidelines.
  14. Hi @Jedd Haas - please can you point me to the FDA recommendation that the alcohol content should be verified with a hydrometer. I have not been following the sanitizer threads closely and am not up to speed on the regulations. Using a hydrometer to check the final product will indicate if there are gross mistakes, but it is not sufficient to truly verify the composition of the product. It will tell you if your formulation is wrong, but will not confirm if it is correct. Here are a few of my observations that may help you good people helping us all out by providing the much-needed sanitizers. Isopropanol has a very similar density to ethanol. My estimate is that if you substitute 5 parts by volume of the ethanol in a 160 proof spirit with 5 parts of isopropanol then the apparent proof would increase to 160.16. In a non-potable product I would guess this is negligible. The glycerol and peroxide are both heavier than ethanol or water, so they will definitely obscure the ethanol. Unfortunately both are lighter than sugar, so I can't push my blending calculator here! I have tried to work out obscuration rules for glycerol and peroxide in the same format that the TTB uses for sugar. The TTB uses the units of 100 mg of sugar per 100 ml of spirit. This is equivalent to 1000 mg of sugar per 1000 ml of spirit or 1 gram per liter, which I find a much easier unit to work with, so I will quote everything in those terms, but the numbers are actually the same as what the TTB uses. [Edit April 10: After doing more calculations together with @SCLabGuy we found that the numbers below were a bit too high. My latest number for glycerol (the only bit that really counts) is 0.12 Proof per gram/L. This makes it even more reasonable to use a hydrometer to check the final product - as the FDA recommends. End Edit] For glycerol I come to 0.23 Proof per gram/L and for peroxide 0.29 Proof per gram/L. These would be specifically for an 80 % ABV alcohol content and would definitely vary with the alcohol strength. These numbers compare with the 0.4 Proof per gram/L the TTB gives for sugar in 80-100 proof spirits. Glycerol at 1.45 v/v is equivalent to 18.3 gram/L so the obscuration would be 18.3 x 0.23 = 4.2 Proof. Peroxide at 0.125 v/v is equivalent to 0.181 gram/L, making the obscuration 0.181 x 0.29 = 0.05 proof and probably not worth worrying about. So if we ignore the variance caused by the isopropanol and the peroxide we can say that the apparent proof should be 160 - 4.2 = 155.8 Proof. Some formulations recommend half the glycerol (i.e. 0.725 v/v) and then the apparent proof would be 160 - 2.1 = 157.9 Proof. Please note that these are all theoretical calculations and you should verify everything with actual measurements. I look forward to @SCLabGuy showing his lab results to see how close we can get with calculations. If my numbers need to be expressed in different terms to make them more useful in practice please let me know and I can rework them.
  15. I haven't seen a way to run Windows applications on the iPad itself, but there are several solutions which allow you to use the iPad to view and control a Windows program running on a separate Windows computer. Have a look at Team Viewer, Jump Desktop, Parallels Access etc. But please note, we have not tested any of these ourselves.
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