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Re:reflux ratio

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  • darryn
    Hi Tom I had exactly the same question when I started running my STILLMAKER still. I contacted Bob at the STILLMAKER site and asked him how I could test my
    Message 1 of 16 , Mar 8, 2000
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      Hi Tom
      I had exactly the same question when I started running my STILLMAKER still.
      I contacted Bob at the STILLMAKER site and asked him how I could test my reflux ratio but the answer was a bit ambiguous.The only way I know how to measure the reflux ratio is by fixing the heat setting and measuring the output without running cooling water through the column over a given period of time.Then you can adjust the cooling water until the output is a fraction of the original measurement eg.1:10.The problem that I found was that in order to condense the vapour when taking the first measurement you had to run cooling water through the column to cool the condenser therefore stuffing up the first measurement.Catch 22 ! To do it properly you would have to have cooling water running directly to the condenser indepedent of the cooling pipes that run through the column.In the end I just asked Bob how many mls per minute he drew out of the still and how much heat he was using and adjusted the water to suit.
      Bob take of between 15-20 mls per minute.If you have got any other questions I'll do my best to help.
      Darryn
    • chunkyboy86
      I ve been looking into the theory of ethanol distillation, and have some questions about the reflux ratio. According to homedistiller.org, the reflux ratio
      Message 2 of 16 , Sep 13, 2005
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        I've been looking into the theory of ethanol distillation, and have
        some questions about the reflux ratio. According to
        homedistiller.org, the reflux ratio doesn't matter too much.

        "The improvement isn't linear either - you can halve the HETP for
        Stainless Steel Wool (SS below) by going from "bugger-all" reflux
        to "some" reflux, but there is little improvement winding it up too
        far past there."

        By the chart given at http://homedistiller.org/refluxdesign.htm, it
        would seem that a reflux ratio of one would be about right. The HETP
        decreases fairly linearly down to about one, where it is approximatly
        120% of the minimum HETP. At 4-5, the improvement stops alltogether.

        Further down the page, it says:

        "Eg we may be able to start out with a reflux ratio of say 3-4 (ie
        return 30-40mL for every 10 mL we keep) when the pot is very rich in
        alcohol, but later on, when its getting down in alcohol, we may need
        to increase this up to 5-10 to keep the high purity."

        If the benifits really stop at 1, why are people running such high
        reflux ratios?

        I don't see how the HETP can stay fairly low with little to no
        reflux. If a column needs a temperature gradient to work, and there's
        no reflux to suck out heat, why doesn't the vapor 'ignore' the
        packing, and blow right by?

        If you're boiling wash produces 60% ethanol in the vapor in the pot,
        and 90% at the top, water needs to condense and flow back down. If
        you have a insulated column, and little reflux, where does the heat
        go?
      • Dean Thomas
        Reflux ratios, It all depends on what you want to produce. I produce as high a strength alcohol as I can typicaly 94-95% at high reflux ratios and
        Message 3 of 16 , Sep 13, 2005
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          Reflux ratios,

          It all depends on what you want to produce. I produce as high a strength
          alcohol as I can typicaly 94-95% at high reflux ratios and
          occasionally I've hit 96. I want my alcohol as pure and clean as I can.
          Because I'm not interested (yet) in flavour preservation I only do sugar
          washes.
          By distilling to a lower 40-70% at low to mid reflux ratios (or a pot
          still) you preserve more flavour this is done to produce Whiskey's and
          Brandy's etc. this is where you ferment molasses and grains and grapes
          and all the other lovely (Messy) stuff.

          Column insulation (Reflux stills)

          If the vapour is pushed up the column too fast and hard the lower
          packing becomes nothing more than an obstacle and may as well not be
          there. When a column is insulated there is still some heat loss, by
          insulating the column we reduce the amount of heat required to push the
          vapour to the top of the column. by reducing the heat input we reduce
          the rate that the alcohol boils off by doing this we also reduce the %
          of water that boils off with it a big plus yes ? All these reductions
          result in a gentler rise of the vapour up through the column, making the
          packing at the bottom much more effective greatly increasing the plate
          count resulting in a higher alcohol percentage. Then you throw a reflux
          condenser on top and increasing the reflux again and up goes the % again.

          Sorry I don't go for all those technical terms like HETP (sounds like
          one of those diseases you come out of hospital with) And I can't stand
          looking at charts and doing formula's I go to work for that stuff.
          My motto K.I.S.S. Keep It Simple Stupid, if I can picture how it works
          in my head It should work. :)

          Dean.

          hunkyboy86 wrote:

          >I've been looking into the theory of ethanol distillation, and have
          >some questions about the reflux ratio. According to
          >homedistiller.org, the reflux ratio doesn't matter too much.
          >
          >"The improvement isn't linear either - you can halve the HETP for
          >Stainless Steel Wool (SS below) by going from "bugger-all" reflux
          >to "some" reflux, but there is little improvement winding it up too
          >far past there."
          >
          >By the chart given at http://homedistiller.org/refluxdesign.htm, it
          >would seem that a reflux ratio of one would be about right. The HETP
          >decreases fairly linearly down to about one, where it is approximatly
          >120% of the minimum HETP. At 4-5, the improvement stops alltogether.
          >
          >Further down the page, it says:
          >
          >"Eg we may be able to start out with a reflux ratio of say 3-4 (ie
          >return 30-40mL for every 10 mL we keep) when the pot is very rich in
          >alcohol, but later on, when its getting down in alcohol, we may need
          >to increase this up to 5-10 to keep the high purity."
          >
          >If the benifits really stop at 1, why are people running such high
          >reflux ratios?
          >
          >I don't see how the HETP can stay fairly low with little to no
          >reflux. If a column needs a temperature gradient to work, and there's
          >no reflux to suck out heat, why doesn't the vapor 'ignore' the
          >packing, and blow right by?
          >
          >If you're boiling wash produces 60% ethanol in the vapor in the pot,
          >and 90% at the top, water needs to condense and flow back down. If
          >you have a insulated column, and little reflux, where does the heat
          >go?
          >
          >
        • Robert Thomas
          Hiya Chunkyboy, It s not all about strength of product. Tiny amounts of other alcohols/ethers/esters make or break the ... NO, no, no. You can get 60-80% on a
          Message 4 of 16 , Sep 13, 2005
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            Hiya Chunkyboy,
            It's not all about strength of product. Tiny amounts
            of other alcohols/ethers/esters make or break the
            product, so:


            --- chunkyboy86 <chunkyboy86@...> wrote:

            > I've been looking into the theory of ethanol
            > distillation, and have
            > some questions about the reflux ratio. According to
            > homedistiller.org, the reflux ratio doesn't matter
            > too much.
            NO, no, no. You can get 60-80% on a pot still, but
            full of flavour compounds. The extra r-ratio is for
            scrubbing these out.

            >
            > "The improvement isn't linear either - you can halve
            > the HETP for
            > Stainless Steel Wool (SS below) by going from
            > "bugger-all" reflux
            > to "some" reflux, but there is little improvement
            > winding it up too
            > far past there."
            Again, you're talking strength, not "drinkable" purity

            >
            > By the chart given at
            > http://homedistiller.org/refluxdesign.htm, it
            > would seem that a reflux ratio of one would be about
            > right. The HETP
            > decreases fairly linearly down to about one, where
            > it is approximatly
            > 120% of the minimum HETP. At 4-5, the improvement
            > stops alltogether.
            OK, you lose me there, as I don't know what you're
            looking at.

            >
            > Further down the page, it says:
            >
            > "Eg we may be able to start out with a reflux ratio
            > of say 3-4 (ie
            > return 30-40mL for every 10 mL we keep) when the pot
            > is very rich in
            > alcohol, but later on, when its getting down in
            > alcohol, we may need
            > to increase this up to 5-10 to keep the high
            > purity."
            >
            > If the benifits really stop at 1, why are people
            > running such high
            > reflux ratios?
            Benefits don't stop at HETP=1, and the whole
            "drinkability vs. partial purity thing"

            > I don't see how the HETP can stay fairly low with
            > little to no reflux.
            There you go.

            > If a column needs a temperature gradient to
            > work, and there's
            > no reflux to suck out heat, why doesn't the vapor
            > 'ignore' the
            > packing, and blow right by?
            Losses through the column, and limited heat input.

            >
            > If you're boiling wash produces 60% ethanol in the
            > vapor in the pot,
            Where did that number come from?

            > and 90% at the top, water needs to condense and flow
            Only if there is reflux occurring!

            > back down. If
            > you have a insulated column, and little reflux,
            > where does the heat
            > go?
            There is a balance between the heating element, the
            condenser, and any losses due to less-than-perfect
            insulation.
            The purification step(s) happen because condensed
            liquid meets boiling vapour in the column. If the heat
            of vaporisation of one component is less than the heat
            of condensation of the other, one will boil, and one
            will condense. No guesses which is which. In real life
            however, the mixtures (both vapour and condensate) are
            multicomponent. Because of this the more "stages"
            these evap/conense cycles do the better.

            The important thing to remember is that most theory is
            based on two component mixtures. In our case, all
            those niggling little impurities make all the
            difference to actually drinking the stuff, and
            enjoying it.
            Cheers,
            Rob.



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          • toddk63
            I have to agree with you. The biggest improvement in purity comes from the amount of packing you start with rather than your heat input or reflux ratio which
            Message 5 of 16 , Sep 13, 2005
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              I have to agree with you. The biggest improvement in purity comes
              from the amount of packing you start with rather than your heat input
              or reflux ratio which is just fine tuning.

              You can see this for yourself by running the little applet from
              homedistillers.org under the "Theory/Reflux Still Design Theory" tab
              called something like "Calculate the HETP for your still"

              My goal in a run is maximum yield, with the highest purity, in the
              shortest amount of time. I run a 16% abv brown sugar and molasses
              wash in my 1.2m x 50mm SS scrubber packed column with 1 kW (measured
              at the condenser). I can comfortably run at 2.3 RR(25ml/min offtake).
              I run into trouble if I try to push it lower than 1.7 RR(30 ml/min
              offtake). Results is 95%abv tapering off to 92% towards the end of
              the middle. My total middle collection is 94% abv and represents
              about 75% of all the potential alcohol available. The end result has
              an ever so slight aroma of tails, which I desire.

              Todd K.

              --- In Distillers@yahoogroups.com, "chunkyboy86" <chunkyboy86@y...> wrote:
              > I've been looking into the theory of ethanol distillation, and have
              > some questions about the reflux ratio. According to
              > homedistiller.org, the reflux ratio doesn't matter too much.
              >
              > "The improvement isn't linear either - you can halve the HETP for
              > Stainless Steel Wool (SS below) by going from "bugger-all" reflux
              > to "some" reflux, but there is little improvement winding it up too
              > far past there."
              >
              > By the chart given at http://homedistiller.org/refluxdesign.htm, it
              > would seem that a reflux ratio of one would be about right. The HETP
              > decreases fairly linearly down to about one, where it is approximatly
              > 120% of the minimum HETP. At 4-5, the improvement stops alltogether.
              >
              > Further down the page, it says:
              >
              > "Eg we may be able to start out with a reflux ratio of say 3-4 (ie
              > return 30-40mL for every 10 mL we keep) when the pot is very rich in
              > alcohol, but later on, when its getting down in alcohol, we may need
              > to increase this up to 5-10 to keep the high purity."
              >
              > If the benifits really stop at 1, why are people running such high
              > reflux ratios?
              >
              > I don't see how the HETP can stay fairly low with little to no
              > reflux. If a column needs a temperature gradient to work, and there's
              > no reflux to suck out heat, why doesn't the vapor 'ignore' the
              > packing, and blow right by?
              >
              > If you're boiling wash produces 60% ethanol in the vapor in the pot,
              > and 90% at the top, water needs to condense and flow back down. If
              > you have a insulated column, and little reflux, where does the heat
              > go?
            • chunkyboy86
              ... Of course. I m not worried about getting the last few % of water out, but higher % shows that it has passed through more plates, and the other impurities
              Message 6 of 16 , Sep 13, 2005
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                --- In Distillers@yahoogroups.com, Robert Thomas <whosbrewing@y...>
                wrote:
                > Hiya Chunkyboy,
                > It's not all about strength of product. Tiny amounts
                > of other alcohols/ethers/esters make or break the
                > product, so:

                Of course. I'm not worried about getting the last few % of water out,
                but higher % shows that it has passed through more plates, and the
                other impurities should be smaller as well. Another big advantage is
                the sharper cut off, which I'm not getting at all.

                >
                > --- chunkyboy86 <chunkyboy86@y...> wrote:
                >
                > > I've been looking into the theory of ethanol
                > > distillation, and have
                > > some questions about the reflux ratio. According to
                > > homedistiller.org, the reflux ratio doesn't matter
                > > too much.
                > NO, no, no. You can get 60-80% on a pot still, but
                > full of flavour compounds. The extra r-ratio is for
                > scrubbing these out.

                Yeah... But... The chart says you can get a HETP of 0.2M with just
                about 0 reflux. that means i should be running 7 plates, even without
                reflux.
                >
                > >
                > > "The improvement isn't linear either - you can halve
                > > the HETP for
                > > Stainless Steel Wool (SS below) by going from
                > > "bugger-all" reflux
                > > to "some" reflux, but there is little improvement
                > > winding it up too
                > > far past there."
                > Again, you're talking strength, not "drinkable" purity
                >

                But they should pretty much follow eachother...
                > >
                > > By the chart given at
                > > http://homedistiller.org/refluxdesign.htm, it
                > > would seem that a reflux ratio of one would be about
                > > right. The HETP
                > > decreases fairly linearly down to about one, where
                > > it is approximatly
                > > 120% of the minimum HETP. At 4-5, the improvement
                > > stops alltogether.
                > OK, you lose me there, as I don't know what you're
                > looking at.
                >

                Follow the link I gave. The chart is about halfway down, and labeled
                HETP vs Reflux Ratio.
                > >
                > > Further down the page, it says:
                > >
                > > "Eg we may be able to start out with a reflux ratio
                > > of say 3-4 (ie
                > > return 30-40mL for every 10 mL we keep) when the pot
                > > is very rich in
                > > alcohol, but later on, when its getting down in
                > > alcohol, we may need
                > > to increase this up to 5-10 to keep the high
                > > purity."
                > >
                > > If the benifits really stop at 1, why are people
                > > running such high
                > > reflux ratios?
                > Benefits don't stop at HETP=1, and the whole
                > "drinkability vs. partial purity thing"

                Not HETP=1, but reflux ratio=1. The chart shows only marginal
                improvement from reflux ratio of 1 to infinity (0.12M to 0.1M)

                What's your deal with the "drinkability vs. partial purity thing".
                How can you strip out the congeners without stripping the water, or
                vise versa? As far as I know, each plate reduces them both, so the
                amount of water reflects the amount of congeners
                >
                > > I don't see how the HETP can stay fairly low with
                > > little to no reflux.
                > There you go.
                >

                But the chart 'says' it does. =\
                > > If a column needs a temperature gradient to
                > > work, and there's
                > > no reflux to suck out heat, why doesn't the vapor
                > > 'ignore' the
                > > packing, and blow right by?
                > Losses through the column, and limited heat input.

                Ok, so you're saying that theres always 'some' reflux. Now that I
                look at the chart, it is a log scale on the x-axis, which means it
                doesn't stay at 0.2 down to 0, the HETP keeps increasing towards
                infinite, which makes more sense.

                Reflux ratio of 0.01 is supposed to be HETP=0.2, which I would be
                happy with right now.
                >
                > >
                > > If you're boiling wash produces 60% ethanol in the
                > > vapor in the pot,
                > Where did that number come from?
                >

                Say you have a 14% wash, the vapor in the boiler will be around 60%.

                > > and 90% at the top, water needs to condense and flow
                > Only if there is reflux occurring!
                >
                > > back down. If
                > > you have a insulated column, and little reflux,
                > > where does the heat
                > > go?
                > There is a balance between the heating element, the
                > condenser, and any losses due to less-than-perfect
                > insulation.
                > The purification step(s) happen because condensed
                > liquid meets boiling vapour in the column. If the heat
                > of vaporisation of one component is less than the heat
                > of condensation of the other, one will boil, and one
                > will condense. No guesses which is which. In real life
                > however, the mixtures (both vapour and condensate) are
                > multicomponent. Because of this the more "stages"
                > these evap/conense cycles do the better.
                >
                > The important thing to remember is that most theory is
                > based on two component mixtures. In our case, all
                > those niggling little impurities make all the
                > difference to actually drinking the stuff, and
                > enjoying it.
                > Cheers,
                > Rob.
                >
                >
                >
                > __________________________________________________
                > Do You Yahoo!?
                > Tired of spam? Yahoo! Mail has the best spam protection around
                > http://mail.yahoo.com
              • chunkyboy86
                ... input ... Yeah, that s a great applet, and I have played around with it a lot. ... offtake). Ok, 2.3 is doable, but according to the applet, you should
                Message 7 of 16 , Sep 13, 2005
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                  --- In Distillers@yahoogroups.com, "toddk63" <toddk63@y...> wrote:
                  > I have to agree with you. The biggest improvement in purity comes
                  > from the amount of packing you start with rather than your heat
                  input
                  > or reflux ratio which is just fine tuning.
                  >
                  > You can see this for yourself by running the little applet from
                  > homedistillers.org under the "Theory/Reflux Still Design Theory" tab
                  > called something like "Calculate the HETP for your still"

                  Yeah, that's a great applet, and I have played around with it a lot.
                  >
                  > My goal in a run is maximum yield, with the highest purity, in the
                  > shortest amount of time. I run a 16% abv brown sugar and molasses
                  > wash in my 1.2m x 50mm SS scrubber packed column with 1 kW (measured
                  > at the condenser). I can comfortably run at 2.3 RR(25ml/min
                  offtake).

                  Ok, 2.3 is doable, but according to the applet, you should lose one
                  plate (out of 13.1) and still get 94.9% with a reflux ratio of 1.

                  > I run into trouble if I try to push it lower than 1.7 RR(30 ml/min
                  > offtake).

                  This doesn't seem to follow the applet =\. What kind of trouble are
                  you running into? How bad does it get with RR of 1?

                  > Results is 95%abv tapering off to 92% towards the end of
                  > the middle. My total middle collection is 94% abv and represents
                  > about 75% of all the potential alcohol available. The end result has
                  > an ever so slight aroma of tails, which I desire.
                  >
                  > Todd K.
                  >
                  > --- In Distillers@yahoogroups.com, "chunkyboy86" <chunkyboy86@y...>
                  wrote:
                  > > I've been looking into the theory of ethanol distillation, and
                  have
                  > > some questions about the reflux ratio. According to
                  > > homedistiller.org, the reflux ratio doesn't matter too much.
                  > >
                  > > "The improvement isn't linear either - you can halve the HETP for
                  > > Stainless Steel Wool (SS below) by going from "bugger-all" reflux
                  > > to "some" reflux, but there is little improvement winding it up
                  too
                  > > far past there."
                  > >
                  > > By the chart given at http://homedistiller.org/refluxdesign.htm,
                  it
                  > > would seem that a reflux ratio of one would be about right. The
                  HETP
                  > > decreases fairly linearly down to about one, where it is
                  approximatly
                  > > 120% of the minimum HETP. At 4-5, the improvement stops
                  alltogether.
                  > >
                  > > Further down the page, it says:
                  > >
                  > > "Eg we may be able to start out with a reflux ratio of say 3-4
                  (ie
                  > > return 30-40mL for every 10 mL we keep) when the pot is very rich
                  in
                  > > alcohol, but later on, when its getting down in alcohol, we may
                  need
                  > > to increase this up to 5-10 to keep the high purity."
                  > >
                  > > If the benifits really stop at 1, why are people running such
                  high
                  > > reflux ratios?
                  > >
                  > > I don't see how the HETP can stay fairly low with little to no
                  > > reflux. If a column needs a temperature gradient to work, and
                  there's
                  > > no reflux to suck out heat, why doesn't the vapor 'ignore' the
                  > > packing, and blow right by?
                  > >
                  > > If you're boiling wash produces 60% ethanol in the vapor in the
                  pot,
                  > > and 90% at the top, water needs to condense and flow back down.
                  If
                  > > you have a insulated column, and little reflux, where does the
                  heat
                  > > go?
                • toddk63
                  You are right. I find that when I run my still, some minimum reflux is required just to keep things in equilibrium. If I go as low as 1.0, I completely lose
                  Message 8 of 16 , Sep 13, 2005
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                    You are right. I find that when I run my still, some minimum reflux
                    is required just to keep things in equilibrium. If I go as low as
                    1.0, I completely lose equilibrium and temps shoot up into 90's°C. I
                    don't believe the applet with low reflux ratios. I have a crude HYSYS
                    model of a still and what I describe seems to be verified with the
                    HYSYS model. BTW, can you ChemE's out there give me some tips on
                    converting my "Static" HYSYS still model into a "Dynamic"

                    Todd K.


                    >
                    > This doesn't seem to follow the applet =\. What kind of trouble are
                    > you running into? How bad does it get with RR of 1?
                    >
                    >
                  • chunkyboy86
                    That s interesting. I am not sure what about right is, so I couldnt tell when to trust the applet, although I did notice that it can go bad at extremes. Now
                    Message 9 of 16 , Sep 13, 2005
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                      That's interesting. I am not sure what 'about right' is, so I couldnt
                      tell when to trust the applet, although I did notice that it can go bad
                      at extremes. Now the main question is why the chart shows that it works
                      decently at low reflux.

                      What is your 'HYSYS' model?

                      Thanks

                      --- In Distillers@yahoogroups.com, "toddk63" <toddk63@y...> wrote:
                      > You are right. I find that when I run my still, some minimum reflux
                      > is required just to keep things in equilibrium. If I go as low as
                      > 1.0, I completely lose equilibrium and temps shoot up into 90's°C. I
                      > don't believe the applet with low reflux ratios. I have a crude HYSYS
                      > model of a still and what I describe seems to be verified with the
                      > HYSYS model. BTW, can you ChemE's out there give me some tips on
                      > converting my "Static" HYSYS still model into a "Dynamic"
                      >
                      > Todd K.
                      >
                      >
                      > >
                      > > This doesn't seem to follow the applet =\. What kind of trouble are
                      > > you running into? How bad does it get with RR of 1?
                      > >
                      > >
                    • Brendan Keith
                      ... Down the drain. Or your water vat for those that recycle. I often detect warm dry air coming out of the top of the column, too. -- Brendan Keith
                      Message 10 of 16 , Sep 13, 2005
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                        > -----Original Message-----
                        > From: Distillers@yahoogroups.com [mailto:Distillers@yahoogroups.com]On
                        > Behalf Of chunkyboy86
                        > Sent: Tuesday, September 13, 2005 3:45 AM
                        > To: Distillers@yahoogroups.com
                        > Subject: [Distillers] reflux ratio
                        >
                        >
                        ...
                        > If you're boiling wash produces 60% ethanol in the vapor in the pot,
                        > and 90% at the top, water needs to condense and flow back down. If
                        > you have a insulated column, and little reflux, where does the heat
                        > go?
                        >
                        >
                        >

                        Down the drain. Or your water vat for those that recycle.

                        I often detect warm dry air coming out of the top of the column, too.

                        --
                        Brendan Keith
                        bkeith@...
                      • Tony Ackland
                        Chunkyboy ... The increase in purity happens because you have a downcoming stream of liquid that is looking to decrease its alcohol concentration, and an
                        Message 11 of 16 , Sep 14, 2005
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                          Chunkyboy

                          > I don't see how the HETP can stay fairly low with little to no
                          > reflux. If a column needs a temperature gradient to work, and there's
                          > no reflux to suck out heat, why doesn't the vapor 'ignore' the
                          > packing, and blow right by?
                          >
                          > If you're boiling wash produces 60% ethanol in the vapor in the pot,
                          > and 90% at the top, water needs to condense and flow back down. If
                          > you have a insulated column, and little reflux, where does the heat
                          > go?

                          The increase in purity happens because you have a downcoming stream of
                          liquid that is looking to decrease its alcohol concentration, and an
                          uprising of vapour that wants to take on more alcohol, based on the
                          equilibrium concentrations of both that suit that particular
                          temperature zone of the column.

                          For example - looking at the graph in
                          http://homedistiller.org/theory.htm - at the zone in the column that is
                          at say 88C (eg mid way up) - the liquid wants to be at 22% alcohol, and
                          the vapour at 72% alcohol. That liquid is coming down from somewhere
                          cooler - lets say 86C - where its presently holding 27% alcohol, and
                          the vapour is coming from somewhere hotter - lets say 90C - with only
                          67% alcohol. So they spread out on the packing, and do their swap.

                          The temperature at that zone is therefore a reflection of the
                          concentration that is present there in its vapour and liquid. But not
                          vice versa. Its not that the alcohol is "condensing out" on cold
                          packing. Rather, its the cross-flow of the two streams, coming from
                          different concentrations, and they settle on the concentration and
                          temperature that will match equilibrium.

                          So its not that the column "needs" a temperature gradient to work, but
                          rather, the column "has" a gradient because it is working.

                          Tony
                          http://homedistiller.org
                        • emailbenja
                          the first colum i built was a hybrid air cooled pot still thingy. It had a packed column, 40 mm diameter, 600mm long (about 6 scrubbers inside). Heating was
                          Message 12 of 16 , Sep 14, 2005
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                            the first colum i built was a hybrid air cooled pot still thingy. It
                            had a packed column, 40 mm diameter, 600mm long (about 6 scrubbers
                            inside). Heating was controlled by a SSR setup, and i could get 93%
                            out of it, tapering off to about 85% at the end of the run. I had no
                            insulation on the column (its stainless,which has a low thermal
                            conductance compared to copper so why bother?).
                            Bugger about it was that it took about 20 hours to distill off 3L of
                            alcohol from a sugar wash, but it was efficient- only took about 300W
                            to maintain the head temp. But i got sick of waiting, and built a new
                            head?column (still air colled though).
                            Will be posting more when i have trialed it fully.
                            So in my opinion, its about controlling the vapour speed, and making
                            sure the temp where you are taking off the product is correct, rather
                            than the amount of reasonably good distillate you are returning to the
                            column.
                            Just my 2c worth
                            benja
                          • toddk63
                            Aspen HYSYS is a refinery process simulation software that ChemE s use. I m not a ChemE (but I play one on TV) so I stumble through it. Price tag has to be in
                            Message 13 of 16 , Sep 14, 2005
                            • 0 Attachment
                              Aspen HYSYS is a refinery process simulation software that ChemE's
                              use. I'm not a ChemE (but I play one on TV) so I stumble through it.
                              Price tag has to be in the $1000's if not $10,000's. I have acces to
                              it at work as a MechE, which helps me model combustion, heat
                              exchangers, gas hydrates and such. At the end of the work day, I'll
                              play with the distillation column models that you can build with it.

                              Todd K.
                              >
                              > What is your 'HYSYS' model?
                              >
                              >
                            • Robert Thomas
                              Hi Todd, the models are 2 component aren t they? I ve no access, so it s all academic anyway. I did find a free access distillation modeling prog somewhere on
                              Message 14 of 16 , Sep 14, 2005
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                                Hi Todd,
                                the models are 2 component aren't they? I've no
                                access, so it's all academic anyway. I did find a free
                                access distillation modeling prog somewhere on the
                                net. Got you 2 component and various setups. I vaguely
                                remember it being off a company that would then try
                                and sell/lease you the whole shebang with
                                thermodynamics linked in etc etc.
                                I'll look again.
                                Cheers,
                                Rob.


                                --- toddk63 <toddk63@...> wrote:

                                > Aspen HYSYS is a refinery process simulation
                                > software that ChemE's
                                > use. I'm not a ChemE (but I play one on TV) so I
                                > stumble through it.
                                > Price tag has to be in the $1000's if not
                                > $10,000's. I have acces to
                                > it at work as a MechE, which helps me model
                                > combustion, heat
                                > exchangers, gas hydrates and such. At the end of
                                > the work day, I'll
                                > play with the distillation column models that you
                                > can build with it.
                                >
                                > Todd K.
                                > >
                                > > What is your 'HYSYS' model?
                                > >
                                > >
                                >
                                >
                                >




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                              • chunkyboy86
                                ... there s ... pot, ... If ... heat ... of ... an ... Right, I understand all that. My question was What happens if you *don t* have the stream coming down?
                                Message 15 of 16 , Sep 14, 2005
                                • 0 Attachment
                                  --- In Distillers@yahoogroups.com, "Tony Ackland" <Tony.Ackland@c...>
                                  wrote:
                                  > Chunkyboy
                                  >
                                  > > I don't see how the HETP can stay fairly low with little to no
                                  > > reflux. If a column needs a temperature gradient to work, and
                                  there's
                                  > > no reflux to suck out heat, why doesn't the vapor 'ignore' the
                                  > > packing, and blow right by?
                                  > >
                                  > > If you're boiling wash produces 60% ethanol in the vapor in the
                                  pot,
                                  > > and 90% at the top, water needs to condense and flow back down.
                                  If
                                  > > you have a insulated column, and little reflux, where does the
                                  heat
                                  > > go?
                                  >
                                  > The increase in purity happens because you have a downcoming stream
                                  of
                                  > liquid that is looking to decrease its alcohol concentration, and
                                  an
                                  > uprising of vapour that wants to take on more alcohol, based on the
                                  > equilibrium concentrations of both that suit that particular
                                  > temperature zone of the column.

                                  Right, I understand all that. My question was "What happens if you
                                  *don't* have the stream coming down?"

                                  I misread the HETP vs Reflux Ratio chart, thinking that it doubled as
                                  the reflux ratio went to 0, and didn't notice the log scale on the x-
                                  axis. It makes more sense that way, since without *any* reflux, there
                                  would be nothing to condense the water out, and you would not get
                                  improvement (ignoring and blowing by the packing).

                                  I do still have a question on this though. Your chart and applet both
                                  show decent HETP with a reflux ratio of 0.01, which is practically
                                  nothing. If that is correct, how can it be true?

                                  Something seems odd with this. I have noticed that I need 'fairly
                                  high' reflux ratio for the still to work at all (it does now :o)).
                                  Todd K. says his still doesnt work right below RR=1.7. Later on your
                                  same page, you say:

                                  "Eg we may be able to start out with a reflux ratio of say 3-4 (ie
                                  return 30-40mL for every 10 mL we keep) when the pot is very rich in
                                  alcohol, but later on, when its getting down in alcohol, we may need
                                  to increase this up to 5-10 to keep the high purity."

                                  Which seems to suggest you really do need higher reflux ratio. Can
                                  you shed some light here?


                                  >
                                  > For example - looking at the graph in
                                  > http://homedistiller.org/theory.htm - at the zone in the column
                                  that is
                                  > at say 88C (eg mid way up) - the liquid wants to be at 22% alcohol,
                                  and
                                  > the vapour at 72% alcohol. That liquid is coming down from
                                  somewhere
                                  > cooler - lets say 86C - where its presently holding 27% alcohol,
                                  and
                                  > the vapour is coming from somewhere hotter - lets say 90C - with
                                  only
                                  > 67% alcohol. So they spread out on the packing, and do their swap.
                                  >
                                  > The temperature at that zone is therefore a reflection of the
                                  > concentration that is present there in its vapour and liquid. But
                                  not
                                  > vice versa. Its not that the alcohol is "condensing out" on cold
                                  > packing. Rather, its the cross-flow of the two streams, coming
                                  from
                                  > different concentrations, and they settle on the concentration and
                                  > temperature that will match equilibrium.

                                  Yep. You already explained that me, through your website :P

                                  >
                                  > So its not that the column "needs" a temperature gradient to work,
                                  but
                                  > rather, the column "has" a gradient because it is working.

                                  Well, its just getting into semantics now, but if you forced a temp
                                  gradient, it would work, if you forced a gradient of 0, it wouldnt.

                                  Anyway, we're in agreement, but I'm still confused about how it
                                  behaves under low reflux ratios.

                                  Thanks for keeping such an informative site, and helping me out here

                                  >
                                  > Tony
                                  > http://homedistiller.org
                                • Jan Ooms
                                  Hi Ben, Call at the slavedrivers joint and I have some goodies for you. Jan Ooms ... From: emailbenja To: Distillers@yahoogroups.com Sent: Wednesday, September
                                  Message 16 of 16 , Sep 17, 2005
                                  • 0 Attachment
                                    Hi Ben,
                                    Call at the slavedrivers joint and I have some goodies for you.
                                    Jan Ooms
                                    ----- Original Message -----
                                    From: emailbenja
                                    To: Distillers@yahoogroups.com
                                    Sent: Wednesday, September 14, 2005 9:39 PM
                                    Subject: [Distillers] Re: reflux ratio


                                    the first colum i built was a hybrid air cooled pot still thingy. It
                                    had a packed column, 40 mm diameter, 600mm long (about 6 scrubbers
                                    inside). Heating was controlled by a SSR setup, and i could get 93%
                                    out of it, tapering off to about 85% at the end of the run. I had no
                                    insulation on the column (its stainless,which has a low thermal
                                    conductance compared to copper so why bother?).
                                    Bugger about it was that it took about 20 hours to distill off 3L of
                                    alcohol from a sugar wash, but it was efficient- only took about 300W
                                    to maintain the head temp. But i got sick of waiting, and built a new
                                    head?column (still air colled though).
                                    Will be posting more when i have trialed it fully.
                                    So in my opinion, its about controlling the vapour speed, and making
                                    sure the temp where you are taking off the product is correct, rather
                                    than the amount of reasonably good distillate you are returning to the
                                    column.
                                    Just my 2c worth
                                    benja




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