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Re: [new_distillers] introduction

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  • Bob Glicksman
    There are lots of opinons about still design details. Here is mine!: I believe that a good, efficient still design requires three thermometers: 1.
    Message 1 of 3 , Dec 3 10:29 AM
      There are lots of opinons about still design details.  Here is mine!:  I believe that a good, efficient still design requires three thermometers:
      1.  Thermometer above the packing.  This is the most important thermometer, as it measures the bp, hence the proof, of the product.
      2.  Thermometer just above the boiler or reboiler.  This is important for safety and in calculating the necessary reflux and thus still energy efficiency, as it measures the bp of the beer vapors and hence is a proxy for proof of the beer.
      3.  Thermometer somewhere in the middle of the (rectifier section) packing.  This is often missed and is the hardest to install correctly (must not interfere with reflux flow).  It is not strictly necessary, but a good idea if you want to maximize energy efficiency by minimizing the reflux ratio needed to achieve whatever the product goal is.  If you don't have this thermometer and you desire azeotropic ethanol, you monitor the top thermometer and if the temperature goes above the bp of the azeotrope, you increase the reflux.  You will know if you haven't increased the reflux ratio enough because the temperature reading will be too high.  But you cannot tell if you have over-refluxed your still.  If you are producing distilled spirits, you might not care about over refluxing.  If you are producing fuel ethanol, then you should be concerned about over refluxing because it wastes energy and thus reduces the cost benefit of your producing fuel.  If your product goal is azeotropic ethanol, the temperature of the product will not go any lower than the bp of the azeotrope, regardless of how much product is returned into the column as reflux.  You can diddle around with the reflux ratio control and observe the temperature of the product vapors,each time going a little above the azeotropic bp and then backing off just a little to see how close you can get to ideal.  This is tedious if done manually, and very hard to automate.  The better approach (IMHO) is to monitor the temperature in the middle of the packing, where the proof is lower than azeotrope and the temperature can vary above and below whatever set-point you are trying to achieve.  This is very important if you want to use a PID controller to vary the heater or the reflux ratio, as any sort of proportional control needs to sense system reaction both above and below the setpoint, and in a more or less linear fashion.
      I hope this line of thought helps.

      -----Original Message-----
      From: kno_man51 <papaowens51@...>
      To: new_distillers <new_distillers@yahoogroups.com>
      Sent: Fri, Dec 2, 2011 9:02 pm
      Subject: [new_distillers] introduction

      hello everyone,this is my first posting.my idea of a social forom is over a cup of coffee at waffle house,so forgive any mistakes. i bookmarked tony ackland's site about ayear ago.i'm mustly completed the mini still,i have only one question. why is the theremeter so far down the column,can place it just above the packing.
      thanks alot

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