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Is This Normal?

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  • eric_yendall
    I am running a standard compound reflux still with a 40 column and 22 coil reflux condenser at the top. Between the column and condenser is the off-take
    Message 1 of 10 , Aug 30, 2008
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      I am running a standard compound reflux still with a 40" column and
      22" coil reflux condenser at the top. Between the column and condenser
      is the off-take leading to a 30" Liebig 1" product condenser. The
      temperature gauge is 3" below the off-take valve. I am running 28
      litres of stripped runs and feints through to produce neutral spirit.

      In my reading I frequently come across advice such as "Maintain the
      head at between 78C and 80C preferably around 78.4C and collect the
      hearts.......cut to tails collection when flow rate slows and
      temperature at the head wants to rise say above 80C and ABV has
      dropped to around 85%..."

      Is this only relevant for spirit runs? If so, my spirit runs don't
      seem to follow this pattern. Most of the product off-take is done well
      below this temperature at around 64C.

      During reflux operation the temperature stays steady at around 60C-61C
      with occasional dips to 59C and jumps to 62C. I am getting about one
      drop per second (can't seem able to increase the flow) over 48hours
      (so far) with product coming out cool at around 94%ABV. Must be doing
      something right but I would like to understand better the context and
      relevance of the advice reproduced above. Is there a flaw in my
      set-up? I don't have continuous cooling water flow to my condensers so
      often the water temperature is quite hot. Then I drain and refill with
      cold water but sometimes not before several hours have elapsed. What
      am I failing to understand? Thanks
    • abbababbaccc
      Get a better thermometer and/or shield it from reflux. Colder reflux dropping to your thermometer will cause all kinds of weird readings. Cheers, Riku
      Message 2 of 10 , Aug 30, 2008
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        Get a better thermometer and/or shield it from reflux. Colder reflux
        dropping to your thermometer will cause all kinds of weird readings.

        Cheers, Riku

        --- In Distillers@yahoogroups.com, "eric_yendall" <eric_yendall@...>
        wrote:
        >
        > I am running a standard compound reflux still with a 40" column and
        > 22" coil reflux condenser at the top. Between the column and condenser
        > is the off-take leading to a 30" Liebig 1" product condenser. The
        > temperature gauge is 3" below the off-take valve. I am running 28
        > litres of stripped runs and feints through to produce neutral spirit.
        >
        > In my reading I frequently come across advice such as "Maintain the
        > head at between 78C and 80C preferably around 78.4C and collect the
        > hearts.......cut to tails collection when flow rate slows and
        > temperature at the head wants to rise say above 80C and ABV has
        > dropped to around 85%..."
        >
        > Is this only relevant for spirit runs? If so, my spirit runs don't
        > seem to follow this pattern. Most of the product off-take is done well
        > below this temperature at around 64C.
        >
        > During reflux operation the temperature stays steady at around 60C-61C
        > with occasional dips to 59C and jumps to 62C. I am getting about one
        > drop per second (can't seem able to increase the flow) over 48hours
        > (so far) with product coming out cool at around 94%ABV. Must be doing
        > something right but I would like to understand better the context and
        > relevance of the advice reproduced above. Is there a flaw in my
        > set-up? I don't have continuous cooling water flow to my condensers so
        > often the water temperature is quite hot. Then I drain and refill with
        > cold water but sometimes not before several hours have elapsed. What
        > am I failing to understand? Thanks
        >
      • burrows206
        Hi Eric, As Riku says cooled reflux splashing down on your temperature probe it is going to give erratic readings. Picture what is happening inside the column
        Message 3 of 10 , Aug 30, 2008
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          Hi Eric,
          As Riku says cooled reflux splashing down on your temperature
          probe it is going to give erratic readings. Picture what is
          happening inside the column you get well cooled ethanol well below 78
          C hitting the probe, then vapour coming up and heating it and taking
          it up higher than 78C and that bringing the temp up to silly temps,
          and then another splash from the condenser hitting it and the
          temperature starts coming down again and this goes round and round
          etc. etc.
          I would be more inclined to take a reading in the pipe between
          the column away from the splashing of the condensed coil reflux and
          the actual leibig condenser, because you know that is the actual
          temperature you are about to condense for product. And your readings
          should at least be uniform (for fore shots, heads, hearts and tails)
          and in line and in keeping with what you have been reading. The
          start of your hearts run before condensing at the leibig should be as
          near as dam at a nice steady 78 degrees C.
          Location of the probe is the important thing. If the take off
          for your leibig comes out of the column horizontal a good few inches
          and then drops vertical. You could drill into the elbow (that drops
          to the leibig) horizontally but before the actual leibig and get a
          dead accurate reading every time from the passuing vapour.(not
          forgetting to insulate the horizonal pipe)
          Geoff


          --- In Distillers@yahoogroups.com, "abbababbaccc" <abbababbaccc@...>
          wrote:
          >
          > Get a better thermometer and/or shield it from reflux. Colder reflux
          > dropping to your thermometer will cause all kinds of weird readings.
          >
          > Cheers, Riku
          >
          > --- In Distillers@yahoogroups.com, "eric_yendall" <eric_yendall@>
          > wrote:
          > >
          > > I am running a standard compound reflux still with a 40" column
          and
          > > 22" coil reflux condenser at the top. Between the column and
          condenser
          > > is the off-take leading to a 30" Liebig 1" product condenser. The
          > > temperature gauge is 3" below the off-take valve. I am running 28
          > > litres of stripped runs and feints through to produce neutral
          spirit.
          > >
          > > In my reading I frequently come across advice such as "Maintain
          the
          > > head at between 78C and 80C preferably around 78.4C and collect
          the
          > > hearts.......cut to tails collection when flow rate slows and
          > > temperature at the head wants to rise say above 80C and ABV has
          > > dropped to around 85%..."
          > >
          > > Is this only relevant for spirit runs? If so, my spirit runs don't
          > > seem to follow this pattern. Most of the product off-take is done
          well
          > > below this temperature at around 64C.
          > >
          > > During reflux operation the temperature stays steady at around
          60C-61C
          > > with occasional dips to 59C and jumps to 62C. I am getting about
          one
          > > drop per second (can't seem able to increase the flow) over
          48hours
          > > (so far) with product coming out cool at around 94%ABV. Must be
          doing
          > > something right but I would like to understand better the context
          and
          > > relevance of the advice reproduced above. Is there a flaw in my
          > > set-up? I don't have continuous cooling water flow to my
          condensers so
          > > often the water temperature is quite hot. Then I drain and refill
          with
          > > cold water but sometimes not before several hours have elapsed.
          What
          > > am I failing to understand? Thanks
          > >
          >
        • Harry
          ... I would be more inclined to take a reading in the pipe between ... .........That s a good location for a VM type takeoff still. But it may not be
          Message 4 of 10 , Aug 30, 2008
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            --- In Distillers@yahoogroups.com, "burrows206" <jeffrey.burrows@...> wrote:

            >
                I would be more inclined to take a reading in the pipe between
            > the column away from the splashing of the condensed coil reflux and
            > the actual leibig condenser, because you know that is the actual
            > temperature you are about to condense for product.  And your readings
            > should at least be uniform (for fore shots, heads, hearts and tails)
            > and in line and in keeping with what you have been reading.


            .........That's a good location for a VM type takeoff still.  But it may not be achievable for a LM type.

             

            > > --- In Distillers@yahoogroups.com, "eric_yendall" <eric_yendall@>
            > > wrote:
            > > >
            > > > I am running a standard compound reflux still with a 40" column
            > and
            > > > 22" coil reflux condenser at the top.


            ...........That's a BIG condenser, easily capable of SUB-cooling the reflux liquid (more on this later).


             my spirit runs don't

            > > > seem to follow this pattern. Most of the product off-take is done
            > well
            > > > below this temperature at around 64C.


            ................As others have mentioned, your temp gauge is reading the temp of the returning reflux, not the rising vapours.  It requires a splash plate or tube for isolation from falling liquids yet still be exposed to rising vapours, which is REALLY what needs to be measured.

            However it does show one important thing:  At 64°C, the reflux is being heavily SUB-COOLED and destroying the efficiency of your column separation capability.  This is a direct result of the size of your overhead condenser being too much capacity (overkill) for the output of that diameter column.

            Fix it by restricting the coolant flow to the overhead coil to raise the coolant discharge temp to around 50°C.  Put a splash guard over the thermometer, and you should see the temp readings stabilize at close to the correct temps.

            SUBCOOLING

            The DEW POINT of the of the rising vapours is the temp point at which they change phase to liquid.  This point is between 78°C - 79°C depending on vapour purity. SUBCOOLING is the lowering of the condensed liquid's temperature  below the dew point. Any excess cooling of the liquid is pointless.  It's a waste of energy and probably the number one (No 1) contributor to a Reflux Still's inefficiencies.  All you achieve is to drive the refluxing liquid further DOWN the column, reducing the column's active length by upsetting the boiler-to-head temperature gradient.  Subcooling (or rather lack of) is one of the critical objectives to be taken into account when designing efficient overhead condensers. That's why this type condenser is always configured to remove the condensed liquid from the cooling surfaces IMMEDIATELY the liquid has formed, to prevent subcooling.

            > > >
            > > > During reflux operation the temperature stays steady at around
            > 60C-61C
            > > > with occasional dips to 59C and jumps to 62C. I am getting about
            > one
            > > > drop per second (can't seem able to increase the flow) over
            > 48hours
            > > > (so far) with product coming out cool at around 94%ABV.


            What type still takeoff is it?  Vapour (VM) or liquid (LM)?

            If it's LM, then you need to enlarge your takeoff plumbing.  If it's VM, then you may need to redesign the way you split the rising vapours.  And what about your Liebig condenser you use?  Is it 1" outer, or 1" inner?  And is it angled, or straight down?  These are important question you need to give answers to, so we can resolve your issues.  Posting a pic or drawing of the setup will be useful.


            Slainte!
            regards Harry

          • Harry
            ... which ... condensed ... number one ... achieve ... the ... overhead ... the ... Further information: Tony Ackland has a really good easy to understand
            Message 5 of 10 , Aug 30, 2008
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              --- In Distillers@yahoogroups.com, "Harry" <gnikomson2000@...> wrote:
              > SUBCOOLING
              >
              > The DEW POINT of the of the rising vapours is the temp point at
              which
              > they change phase to liquid. This point is between 78°C - 79°C
              > depending on vapour purity. SUBCOOLING is the lowering of the
              condensed
              > liquid's temperature below the dew point. Any excess cooling of the
              > liquid is pointless. It's a waste of energy and probably the
              number one
              > (No 1) contributor to a Reflux Still's inefficiencies. All you
              achieve
              > is to drive the refluxing liquid further DOWN the column, reducing
              the
              > column's active length by upsetting the boiler-to-head temperature
              > gradient. Subcooling (or rather lack of) is one of the critical
              > objectives to be taken into account when designing efficient
              overhead
              > condensers. That's why this type condenser is always configured to
              > remove the condensed liquid from the cooling surfaces IMMEDIATELY
              the
              > liquid has formed, to prevent subcooling.



              Further information:

              Tony Ackland has a really good easy to understand explanation of this
              phenomenon here...
              http://homedistiller.org/heatmass.htm

              Slainte!
              regards Harry
            • abbababbaccc
              Harry, IIRC there was discussion about subcooling few years back where Mike Nixon was also contributing. If I m not mistaken the subcooling only forms a short
              Message 6 of 10 , Aug 31, 2008
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                Harry,

                IIRC there was discussion about subcooling few years back where Mike
                Nixon was also contributing. If I'm not mistaken the subcooling only
                forms a short (1-2cm) transition layer on top of the packing thus
                making any drop in column efficiency negligible. It is a waste of
                energy and water but then again it's better to waste a bit while
                making sure you don't fill your garage/shed with alcohol vapor.

                Of course this only applies to columns with condenser on top of the
                packing and gives out the reason why through tubes are really a bad idea.

                Cheers, Riku

                --- In Distillers@yahoogroups.com, "Harry" <gnikomson2000@...> wrote:
                >
                > ................As others have mentioned, your temp gauge is reading the
                > temp of the returning reflux, not the rising vapours. It requires a
                > splash plate or tube for isolation from falling liquids yet still be
                > exposed to rising vapours, which is REALLY what needs to be measured.
                >
                > However it does show one important thing: At 64°C, the reflux is
                > being heavily SUB-COOLED and destroying the efficiency of your column
                > separation capability. This is a direct result of the size of your
                > overhead condenser being too much capacity (overkill) for the output of
                > that diameter column.
                >
                > Fix it by restricting the coolant flow to the overhead coil to raise the
                > coolant discharge temp to around 50°C. Put a splash guard over the
                > thermometer, and you should see the temp readings stabilize at close to
                > the correct temps.
                >
                > SUBCOOLING
                >
                > The DEW POINT of the of the rising vapours is the temp point at which
                > they change phase to liquid. This point is between 78°C - 79°C
                > depending on vapour purity. SUBCOOLING is the lowering of the condensed
                > liquid's temperature below the dew point. Any excess cooling of the
                > liquid is pointless. It's a waste of energy and probably the number one
                > (No 1) contributor to a Reflux Still's inefficiencies. All you achieve
                > is to drive the refluxing liquid further DOWN the column, reducing the
                > column's active length by upsetting the boiler-to-head temperature
                > gradient. Subcooling (or rather lack of) is one of the critical
                > objectives to be taken into account when designing efficient overhead
                > condensers. That's why this type condenser is always configured to
                > remove the condensed liquid from the cooling surfaces IMMEDIATELY the
                > liquid has formed, to prevent subcooling.
                >
                > Slainte!
                > regards Harry
                >
              • Harry
                ... If I m not mistaken the subcooling only ... This may be correct for a properly adjusted and balanced column/condenser design, but not for a design where
                Message 7 of 10 , Aug 31, 2008
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                  --- In Distillers@yahoogroups.com, "abbababbaccc" <abbababbaccc@...> wrote:
                  >
                  > Harry,
                  >
                   If I'm not mistaken the subcooling only
                  > forms a short (1-2cm) transition layer on top of the packing thus
                  > making any drop in column efficiency negligible.

                  > Cheers, Riku

                   

                  This may be correct for a properly adjusted and balanced column/condenser design, but not for a design where excessive cooling capacity is available and being applied.

                  As Tony explains in his notes, the colder (subcooled) liquid will continue to descend the column until rising (hotter) vapours reheat it to vapour point and again begin the usual heat exchange/separation process.

                  Excessive subcooling does not happen 1-2 cm down.  The liquid does not somehow float on top of the rising vapour.  Gravity is the over-riding force in play here, and liquid being way heavier than gas, the sub-cooled liquid goes sometimes halfway down a 100 cm column, creating a similar effect as if you had a pass-through cooling tube at that point.  It also interferes with the temp of the rising vapours and disrupts the bottom-to-top heat gradient of the column, further robbing the column of its capabilities.

                  You can verify this for yourself.  Take an overhead total condenser with excess cooling capacity, such as the one the original thread poster has.  Fit a test column to it made as follows:  The column will have temp gauges at points along its length bottom to top, or ports for a temp probe to be introduced.  Threaded & capped brass nipples are easy to fit and can be uncapped to introduce a temp probe at any point on the column.

                  Either conduct the test outdoors, or vent the column top to the outside via attached tubing or hose so that any vapours that may pass through the condenser are vented outdoors and dissipate harmlessly.

                  Start the test by shutting off the water feed to the overhead condenser.  Boil up the beer.  Once boiling, adjust the energy feed for that size column (1000-1200 watts is about right for a 50mm x 100cm column).  At boiling point take & record readings at the various points along the column.  Now slowly feed coolant to the condenser.  Again take readings.  Continue to increase the coolant flow in steps, taking readings at every increase step, until you are feeding coolant at the maximum flow capacity of the condenser.

                  Shut everything down and compare your readings.  Find the column point that reads the coolest temp.  This is the point that your column has been reduced to in regards to operating length (height).  You'll find it's a good deal further down than 1-2 cm below the top of the packing.

                  The total refluxing liquid at this point is the sum of the liquid condensed overhead, and the condensate from rising vapours condensed through heat exchange contact with the falling subcooled liquid.  These vapours never reached the condenser but are now liquid and add to the overall liquid load on the column.  In severe cases you can reach a point where the column is rendered inoperable due to excess liquid which creates flooding and it will dump through to the boiler.

                  A series of distillation textbooks (pricey) By Henry Z. Kist explains subcooling, of both column beer feed and reflux, and many other aspects of designing, building and troubleshooting columns & condensers.  They are mainly aimed at the commercial petro-chemical industry but the principles apply equally to ethanol distilling, even hobby-sized outfits.  Distilling is distilling, whatever the size of the rig.

                  HTH

                  Slainte!
                  regards Harry

                • Eric Yendall
                  Thanks everyone for your terrific responses. They have gotten me thinking again. Probably I should have done more of that before posting the original question
                  Message 8 of 10 , Aug 31, 2008
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                    Thanks everyone for your terrific responses. They have gotten me thinking again. Probably I should have done more of that before posting the original question but hey, if everyone did that, we wouldn't have much of a forum here would we.

                    Forget about my reference to 64C and spirit run. I use a different column and no reflux condenser and I should have typed 69C.

                    I am distilling a 40%ABV solution.

                    The temperature gauge I am using is the digital model as sold by Brewhaus via Ian Smiley so it should be up to the job. I will test it again with boiling water. It is inserted into a quarter inch OD copper tube which protrudes about three-quarter inches into the column. I cut away the underside within the column so the top acts as a hood. I don't think liquid should be hitting the probe. Now could the problem be that the probe is touching the copper and is measuring the temperature of the copper column and not the vapour? The internal diameter of the tube is not much greater than the probe. I wrapped teflon tape at both ends to avoid contact with the copper but perhaps this is not effective. If this is the problem, would would you suggest as a solution.

                    Harry, to answer your question: the offtake is 90deg from the column to the gate valve then immediately down 90deg to the Liebig which is a half-inch tube within a one inch tube. About six inches over the six inches down to the condenser.When you talk about the efficiency of the still are you talking about the heat input required to produce the product, or the quality of the product. My still seems to be OK on both of these as it achieves reflux as one would expect, the output at one drop per second seems acceptable, and the product quality is excellent.

                    Riku: the temperature remains fairly constant within a very narrow range, so I would not characterize it as erratic.

                    Don't misunderstand me, I am not challenging any of your responses; just trying to understand better how my still should operate.

                    Eric


                    In politics and government, never attribute to conspiracy what can be adequately explained by stupidity.
                  • Harry
                    ... column and no reflux condenser and I should have typed 69C. .........In your first post you said I am running a standard compound reflux still with
                    Message 9 of 10 , Aug 31, 2008
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                      --- In Distillers@yahoogroups.com, Eric Yendall <eric_yendall@...> wrote:

                      >
                      > Forget about my reference to 64C and spirit run. I use a different column and no reflux condenser and I should have typed 69C.


                      .........In your first post you said <quote> I am running a standard compound reflux still with a 40" column and 22" coil reflux condenser at the top. <unquote>.

                      Now you say you DON'T HAVE a reflux condenser?  So do you or don't you?  If you don't have an overhead condenser, you have a pot still, not a reflux still, compound or otherwise.

                      >
                      > I am distilling a 40%ABV solution.

                      .........Obviously a charge of strippate + water/feints from a previous stripping run.

                      >
                      > The temperature gauge I am using is the digital model as sold by Brewhaus via Ian Smiley so it should be up to the job. I will test it again with boiling water. It is inserted into a quarter inch OD copper tube which protrudes about three-quarter inches into the column. I cut away the underside within the column so the top acts as a hood. I don't think liquid should be hitting the probe.

                      .....You'd be surprised how much liquid falls down a column from an overhead condenser (if you have one).  If you don't have one then the only liquid in the column will be condensate caused by heat losses to the air around the column.  IOW VERY LITTLE MOISTURE.  Certainly not an amount you could call standard reflux.


                       Now could the problem be that the probe is touching the copper and is measuring the temperature of the copper column and not the vapour?

                      The temp of the copper column will be the temp of the rising vapour AT THAT POINT minus a little bit due to any losses of heat to surrounding air.  If your column is insulated, this loss will be virtually nil.


                       The internal diameter of the tube is not much greater than the probe. I wrapped teflon tape at both ends to avoid contact with the copper but perhaps this is not effective. If this is the problem, would would you suggest as a solution.

                      >
                      > Harry, to answer your question:  the offtake is 90deg from the column to the gate valve then immediately down 90deg to the Liebig which is a half-inch tube within a one inch tube.


                      ......So this is a Vapour Management (VM) still?  Then it MUST have some sort of overhead condenser.  A gate valve in a pot still (a still without an overhead condenser) would be a useless appendage.  You could have save us a bit of guesswork if you'd posted a pic or drawing of the rig.

                       About six inches over the six inches down to the condenser.When you talk about the efficiency of the still are you talking about the heat input required to produce the product, or the quality of the product.


                      ...........Efficiency of the still is the ability to function properly (little or no faults) and vapourise & separate volatile substances according to its design parameters, thus producing product.
                      The quality of that product largely depends on your ability to operate the said still within those parameters IOW not creating subcooling, excess vapour speed or overdriving the rig in any way.


                       My still seems to be OK on both of these as it achieves reflux as one would expect, the output at one drop per second seems acceptable, and the product quality is excellent.


                      .........If it is indeed a VM still, there's a few tricks you can pull to get better product takeoff rate.  A dedicated in-column vapour stream splitter/diverter is one.  A bit of copper mesh packing in the liebig vapour tube to create turbulence is another, and probably advisable for any vertically mounted liebig.  It will prevent gas bypass.  Do you get your theoretical yield now?  Or are you short?


                      Slainte!
                      regards Harry

                    • eric_yendall
                      Harry It is a compound reflux vapour management still. Forget any previous references to spirit runs. Eric ... probe. I
                      Message 10 of 10 , Aug 31, 2008
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                        Harry
                        It is a compound reflux vapour management still. Forget any previous
                        references to spirit runs.
                        Eric



                        --- In Distillers@yahoogroups.com, "Harry" <gnikomson2000@...> wrote:
                        >
                        >
                        > --- In Distillers@yahoogroups.com <mailto:Distillers@yahoogroups.com> ,
                        > Eric Yendall <eric_yendall@> wrote:
                        > >
                        > > Forget about my reference to 64C and spirit run. I use a different
                        > column and no reflux condenser and I should have typed 69C.
                        >
                        >
                        > .........In your first post you said <quote> I am running a standard
                        > compound reflux still with a 40" column and 22" coil reflux condenser at
                        > the top. <unquote>.
                        >
                        > Now you say you DON'T HAVE a reflux condenser? So do you or don't you?
                        > If you don't have an overhead condenser, you have a pot still, not a
                        > reflux still, compound or otherwise.
                        >
                        > >
                        > > I am distilling a 40%ABV solution.
                        >
                        > .........Obviously a charge of strippate + water/feints from a previous
                        > stripping run.
                        >
                        > >
                        > > The temperature gauge I am using is the digital model as sold by
                        > Brewhaus via Ian Smiley so it should be up to the job. I will test it
                        > again with boiling water. It is inserted into a quarter inch OD copper
                        > tube which protrudes about three-quarter inches into the column. I cut
                        > away the underside within the column so the top acts as a hood. I don't
                        > think liquid should be hitting the probe.
                        >
                        > .....You'd be surprised how much liquid falls down a column from an
                        > overhead condenser (if you have one). If you don't have one then the
                        > only liquid in the column will be condensate caused by heat losses to
                        > the air around the column. IOW VERY LITTLE MOISTURE. Certainly not an
                        > amount you could call standard reflux.
                        >
                        >
                        > Now could the problem be that the probe is touching the copper and is
                        > measuring the temperature of the copper column and not the vapour?
                        >
                        > The temp of the copper column will be the temp of the rising vapour AT
                        > THAT POINT minus a little bit due to any losses of heat to surrounding
                        > air. If your column is insulated, this loss will be virtually nil.
                        >
                        >
                        > The internal diameter of the tube is not much greater than the
                        probe. I
                        > wrapped teflon tape at both ends to avoid contact with the copper but
                        > perhaps this is not effective. If this is the problem, would would you
                        > suggest as a solution.
                        > >
                        > > Harry, to answer your question: the offtake is 90deg from the column
                        > to the gate valve then immediately down 90deg to the Liebig which is a
                        > half-inch tube within a one inch tube.
                        >
                        >
                        > ......So this is a Vapour Management (VM) still? Then it MUST have some
                        > sort of overhead condenser. A gate valve in a pot still (a still
                        > without an overhead condenser) would be a useless appendage. You could
                        > have save us a bit of guesswork if you'd posted a pic or drawing of the
                        > rig.
                        >
                        > About six inches over the six inches down to the condenser.When you
                        > talk about the efficiency of the still are you talking about the heat
                        > input required to produce the product, or the quality of the product.
                        >
                        >
                        > ...........Efficiency of the still is the ability to function properly
                        > (little or no faults) and vapourise & separate volatile substances
                        > according to its design parameters, thus producing product.
                        > The quality of that product largely depends on your ability to operate
                        > the said still within those parameters IOW not creating subcooling,
                        > excess vapour speed or overdriving the rig in any way.
                        >
                        >
                        > My still seems to be OK on both of these as it achieves reflux as one
                        > would expect, the output at one drop per second seems acceptable, and
                        > the product quality is excellent.
                        >
                        >
                        > .........If it is indeed a VM still, there's a few tricks you can pull
                        > to get better product takeoff rate. A dedicated in-column vapour stream
                        > splitter/diverter is one. A bit of copper mesh packing in the liebig
                        > vapour tube to create turbulence is another, and probably advisable for
                        > any vertically mounted liebig. It will prevent gas bypass. Do you get
                        > your theoretical yield now? Or are you short?
                        >
                        >
                        > Slainte!
                        > regards Harry
                        >
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