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meerkat last won the day on November 13

meerkat had the most liked content!

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About meerkat

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  1. meerkat

    Dephleg hotter than column

    The liquid flow to the trays can only come from the dephlegs. With moderate heat on the still pot, open the water to the condenser and second dephleg. I would close the water to the 1st dephleg and get the trays in the second column loaded first. The aim is to get the 2nd column on total reflux to start with, but have water open to the condenser in case the vapor load is too much for the 2nd dephleg. At this stage the 1st column and dephleg is just a pipe to get the vapor to the 2nd column. Once you see that you have the trays in the second column loaded and bubbling then you can bring the 1st column on line. Open the water to the 1st dephleg a bit to start the liquid flow to the trays in column 1, and maybe a bit more heat to the still, and get the trays in this column loaded. If this causes the trays in the second column to run dry you have too much water on the 1st dephleg (or not enough heat in the still). Run the unit like this on total reflux with all the trays loaded for a while to get a feel for what is happening, and then you can gradually decrease the cooling water flow to the dephlegs so that some product goes over to the main condenser. Its hard to summarize all this in a few words. I am sure that a chat with Mike will give you a chance to ask the questions that are difficult here.
  2. meerkat

    Dephleg hotter than column

    The valves in the vapor line certainly look like they are correctly set, so that just adds to the mystery. You did not say whether the trays in the 2nd column were behaving correctly. Their behavior will be a good indicator of whether the vapors are following the correct path.
  3. meerkat

    Dephleg hotter than column

    When the dephleg is so hot and the 2nd column so cold are the trays in the second column bubbling normally? The only way I can see that you could get the dephleg so hot is if the vapor valve that is intended to isolate the 2nd dephleg (and main condenser) from the pot is passing hot vapor that should be going via all the trays and this vapor is going directly to the 2nd dephleg. If this valve is passing then the trays will not bubble properly. What is the temperature of the 1st dephleg when the second is at 90?
  4. meerkat

    Mixing ethanol and water

    If you need any help I am only too happy to guide you through a few calculations until your confidence builds. The learning curve is a bit steep, but quite short and you will quickly master it. The program is designed for speed and power and just like a powerful sports car, the effort of learning to drive it reaps the rewards.
  5. meerkat

    Mixing ethanol and water

    @Welshbrew You are correct. At 20°C 50 L of pure ethanol plus 50 L of pure water makes 96.46 L of spirit and your ABV would be ( (50 / 96.46) x 100) = 51.83% But (unfortunately) you have not gained any ethanol and if you could distill it out again you would get the same 50 L of pure ethanol back, as well as the 50L of water. Of course this is not possible because of the azeotrope, but I'm sure you get my drift. The ABV definition is actually very useful, because if you started with 50 L of pure ethanol then no matter how you diluted it and irrespective of the shrinkage that occurs (which is different at different dilutions) you will always have your 50 L of pure ethanol in there somewhere and that is the bit that the Tax people want to know about.
  6. meerkat

    steady take off rate

    @Southernhighlander Your explanation of the vent cleared up my confusion. I thought that it was part of the piping between the condenser and the parrot, but now I understand that it is a safety vent in case of condenser malfunction. I have seen vapors and liquid spewing out of condensers and I agree that safety is the first priority. @Allan No more info needed.
  7. meerkat

    steady take off rate

    @Allan I do not understand where the vent pipe was that you removed. Can you post a picture of how it was, or just a simple sketch of the before and after situation. Thanks.
  8. I haven't done it this way, but that is not to say you can't make it work. It seems unnecessarily complicated and I always prefer the KISS approach. Hopefully you will get a comment from someone who has tried it.
  9. The problem is not that the return line discharges above the level in the pot. The problem is that there is nothing to stop the vapors flowing up the return line. If the discharge is above the liquid level then there must be an external liquid seal in the return line to block the vapors. There are pro's and con's for internal and external liquid seals, but both can work perfectly well. A similar situation exists with the downcomer on a bubble cap tray. If the lower end of the downcomer does not have a liquid seal - either with an inverted cap or by extending the downcomer to below the liquid level on the tray below, then the vapor will flow up the downcomer rather than through the bubble caps.
  10. It is very important that vapor be prevented from going up the return line. As you said, the vapor will "fight" with the liquid because they are going in different directions. The way to stop the vapor going back up the return line is to install a liquid seal. This seal can either be inside the pot (by having the return line extend to below the liquid surface) or external to the pot by installing a U or P, but not an S, trap. I have seen vapor locking occur with an internal seal, ie one that enters the pot above the liquid level but extends down below the surface. This is because it is quite tricky to get the sizing of the line just right to be able to flush any incondensible gases down the seal leg. However, this is easily fixed by drilling a small hole (approx 1/8") in the elbow inside the pot above the liquid level. This is big enough to allow the small quantity of trapped gases to escape into the pot, but small enough to limit vapors from the pot entering the return line and causing problems.
  11. meerkat

    steady take off rate

    You can verify this during the next run by holding a sheet of paper over your burp tube to see if a vacuum is being developed at any stage.
  12. meerkat

    steady take off rate

    @Southernhighlander I have no doubt that you can build a complete bain marie-based system. The problem in this situation could be mismatched components. Is the column being used the same diameter that you would install on this boiler? Are the plates the same design? Are the power and positioning of the agitator as per your design? Is the heating power what you would use? @adamOVD It would be useful if you could find some other parameter that is cycling at the same frequency as the product flow, as this could indicate the cause. For example, can you measure the amps to the agitator? If the agitator is causing a vortex the entrained vapor might be interfering with the heat transfer from the shell and causing the cycling. Does the temperature in the jacket vary? Can you measure the pressure in the boiler? Does it cycle? I am pulling things out of the air here, but you need to measure whatever you can and try to find something that is cycling in sync with the production rate.
  13. meerkat

    steady take off rate

    @Southernhighlander and @adamOVD - I agree 100% on the need for the "burp tube". I always install them, although I always include a 3 or 4 ft vertical riser from the elbow. But even with the riser I have seen liquid gushing from the vent. The venting of uncondensible gases is critical and I have seen operators on continuous plants using the smell from these vents as an indication of the operation of the column. I would be very careful about blanking it off. PeteB's concern about sucking air into the condenser is valid, but I have found this to only happen when the condenser is significantly oversized or the water is unusually cold. In my experience this cycling of the product rate is caused by either bad piping design around the condenser, or by cycling of the heat input in the boiler. I suppose it could be caused by the plates but I have never seen that and it seems to be happening here whether the plates are installed or not. Most of the cycling cases I have come across have been caused by condenser piping design and that was the motivation for my questions. @vsaks had exactly this problem last year. But from the photo you have supplied and the answers to the questions I think in this case the problem is not around the condenser. Unfortunately most of my experience on the heating side has been with thermosiphon reboilers and I have never used a bain marie boiler. Cycling can definitely occur with an oversized thermosiphon reboiler so in view of the elimination of the condenser piping and the plates as suspected causes I would concentrate on the heating side.
  14. meerkat

    steady take off rate

    Below the tapered section at the bottom of the condenser there is a tee with a 90 degree elbow on it. Is this a vent that is always open? If it is a vent and the surging is significant I would expect liquid to come out here during the surges - or is the flow during the surges not that much more than during the slow times? Any feel for the ratio between the maximum and minimum flows? Are the surges enough to cause the parrot to overflow? Does the flow out of the parrot ever stop completely during the slow part of the cycle? Do you see bubbles coming to the surface of the parrot during the surges?
  15. meerkat

    TTB stopped our production due to high proof

    @Patio29Dadio - I agree with you. I have assumed that these density variations are "worst case" examples and that they therefore give the largest error possible in the proof reading. I only wanted to give a better feel for what these accuracies meant. The real interpretation of the accuracy is a bit more complicated. For example, Anton Paar give the accuracy of the 1001 as 0.0001 g/cm3 and the repeatability as 0.00005 g/cm3 (expressed as a standard deviation). This means that if you ran the same sample 1000 times then 680 of the readings would be within 0.00005 g/cm3 (1 std deviation) of some average density and 997 would be within 0.0001 g/cm3 (two std deviations) of that average. I suspect that the difference between this average and the true density is what they call the accuracy. If someone from Anton Paar is reading this it would be great to have your input. Very few labs interpret their results as rigorously as this.