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Reflux Valve = Temperature Controller (?)

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  • smudge311065
    I ve read that the design of a reflux valve/still is not temperature based. That may be true, but analysing its operation in terms of temperature will make a
    Message 1 of 17 , Mar 28, 2003
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      I've read that the design of a reflux valve/still is not temperature
      based. That may be true, but analysing its operation in terms of
      temperature will make a lot of sense to us non-chemical engineers...

      If you operate a perfectly insulated column with zero-reflux there
      would be no heat loss up its length and the temperature of the vapour
      at the top would be the same as the temperature of the boiling wash
      at the bottom.

      Consider the same set-up, but now with 100%-reflux: The reflux causes
      the temperature at the top of the column to drop. If it drops too low
      (eg 77 degrees) then ethanol cannot exist as vapour – no vapour means
      no reflux, and the temperature will rise towards the zero-reflux
      equilibrium point. The result of these opposing effects is a 100%-
      reflux equilibrium point very close to the lowest temperature at
      which ethanol can exist as vapour.

      Setting the reflux ratio somewhere between 0% and 100% will result in
      an equilibrium temperature at the top of the column somewhere between
      the wash temperature and 78.15 degrees. As distillation progresses,
      the boiling wash temperature increases so the controlling range of
      your reflux valve increases, which is why the output temperature
      rises. (The midpoint of the small range is lower than the midpoint of
      the large range)

      You may not intend to set the output temperature with the reflux
      valve, but that is the effect of what you are doing. The truth is
      this method of control is extremely effective at setting the
      temperature which might be why temperature has been considered
      irrelevant: The 100%-reflux end of the reflux valve range will always
      be very close to the point of maximum purity, automatically allowing
      for everything that might change it, and without the need to
      accurately measure it. This is certainly not the true for direct
      temperature control, where equipment accuracy limits your ability to
      find this point.

      The big disadvantage of this method of control is that you have to
      manually intervene to separate the heads, body and tails: It will
      find the maximum purity point of whatever happens to be boiling at
      the time, whether it's ethanol or not.

      If I were designing my still again (and I'm not) I would combine both
      methods of control. I think the reflux valve has real advantages if
      you want the highest possible purity, but a temperature controller is
      great for allowing the system to operate without constant supervision
      and maximising heat input for stripping runs.


      Smudge
    • rodmacd2000
      I ve been following this discussion and apparently you **still** don t get the point Smudge. ... temperature ... vapour ... *Right ... causes ... low ... means
      Message 2 of 17 , Mar 29, 2003
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        I've been following this discussion and apparently you **still**
        don't get the point Smudge.

        --- In Distillers@yahoogroups.com, "smudge311065" <smudge@b...> wrote:
        > I've read that the design of a reflux valve/still is not
        temperature
        > based. That may be true, but analysing its operation in terms of
        > temperature will make a lot of sense to us non-chemical engineers...
        >
        > If you operate a perfectly insulated column with zero-reflux there
        > would be no heat loss up its length and the temperature of the
        vapour
        > at the top would be the same as the temperature of the boiling wash
        > at the bottom.
        >

        *Right

        > Consider the same set-up, but now with 100%-reflux: The reflux
        causes
        > the temperature at the top of the column to drop. If it drops too
        low
        > (eg 77 degrees) then ethanol cannot exist as vapour – no vapour
        means
        > no reflux, and the temperature will rise towards the zero-reflux
        > equilibrium point. The result of these opposing effects is a 100%-
        > reflux equilibrium point very close to the lowest temperature at
        > which ethanol can exist as vapour.
        >

        *Well sort of. A drop in temperature at the still-head when there are
        multiple chemicals in the wash is caused by the different volatility
        (boiling points) of the chemicals involved. Under 100% reflux in a
        well designed still the highest substance in the column will have the
        lowest boiling point and so of course will show a relatively low
        temperature. In our case we first see methanol, acetone and other
        assorted nastys.

        > Setting the reflux ratio somewhere between 0% and 100% will result
        in
        > an equilibrium temperature at the top of the column somewhere
        between
        > the wash temperature and 78.15 degrees. As distillation progresses,
        > the boiling wash temperature increases so the controlling range of
        > your reflux valve increases, which is why the output temperature
        > rises. (The midpoint of the small range is lower than the midpoint
        of
        > the large range)
        >

        *As we *slowly* (i.e. RR= 10 or greater) operate our still after
        first attaing equilibrium the highest
        volatility (lowest BP) stuff will be drawn off first and as it is,
        still-head temp will slowly rise until we hit our goal of the ethyl
        alcohol Azeotrope. NB We are not *controlling* still head
        temperature - just letting it follow the rules of physical chemistry
        as we keep the system close to total reflux.

        > You may not intend to set the output temperature with the reflux
        > valve, but that is the effect of what you are doing. The truth is
        > this method of control is extremely effective at setting the
        > temperature which might be why temperature has been considered
        > irrelevant: The 100%-reflux end of the reflux valve range will
        always
        > be very close to the point of maximum purity, automatically
        allowing
        > for everything that might change it, and without the need to
        > accurately measure it. This is certainly not the true for direct
        > temperature control, where equipment accuracy limits your ability
        to
        > find this point.
        >

        *Once we start drawing off our goal of ethyl alcohol still-head
        temperature *will not budge* while we draw off the product we are
        interested in. For example I use a Checktemp 1 digital Fahrenheit
        thermometer which remains absolutely locked within 1/10 of a F degree
        for at least 15 hours while my 96% Azeotrope is being collected.

        During this 15 hours, of course, the temperature in the boiler
        increases as alcohol concentration decreases. This is where the
        importance of good still design/construction/operation comes in. As
        the temperature differential between boiler and still-head increases
        we require that purity of the product stay at the same high level.

        > The big disadvantage of this method of control is that you have to
        > manually intervene to separate the heads, body and tails: It will
        > find the maximum purity point of whatever happens to be boiling at
        > the time, whether it's ethanol or not.
        >
        > If I were designing my still again (and I'm not) I would combine
        both
        > methods of control. I think the reflux valve has real advantages if
        > you want the highest possible purity, but a temperature controller
        is
        > great for allowing the system to operate without constant
        supervision
        > and maximising heat input for stripping runs.
        >
        >
        > Smudge

        Sorry if I sound a little dogmatic. I know there is more than one way
        of doing just about anything and of course I'm aware that many others
        are interested in something other than just collecting pure spirit.
      • homedistiller
        Don t be so fast to judge! Smudge certainly DOES get the point and proves this, with his set-up, in practice. He has a very scientific and very accurate
        Message 3 of 17 , Mar 29, 2003
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          Don't be so fast to judge!

          Smudge certainly DOES get the point and proves this, with his set-up,
          in practice.

          He has a very scientific and very accurate approach to the matter and
          yes, he dares to question and challenge. Anything wrong with that ?

          When he puts his still on, he can go to bed. By the time he wakes up,
          he has over 20 liters of very pure alcohol waiting for him.
          All by controlling the temperature.

          Dirk




          --- In Distillers@yahoogroups.com, "rodmacd2000" <rmacdoug@s...>
          wrote:
          > I've been following this discussion and apparently you **still**
          > don't get the point Smudge.
        • peter_vcb
          Setting the reflux ratio somewhere between 0% and 100% will result in an equilibrium temperature at the top of the column somewhere between the wash
          Message 4 of 17 , Mar 31, 2003
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            "Setting the reflux ratio somewhere between 0% and 100% will result
            in an equilibrium temperature at the top of the column somewhere
            between the wash temperature and 78.15 degrees."

            -this is true only if the column is high enough to get that purity.
            Adrian ran his column at full reflux and got no output until about
            80C. meaning the column was not tall enough to ever get 96% alcohol
            in it. if you had a 100mm column with no packing which was cooled to
            78C you would get no output.

            MIKE N- could you please comment on Johans 1/2" copper tube still.
            95% from a 3% wash with no packing, what is going on there! all i can
            consider is that the tube is so narrow that the vapour is exposed to
            a large surface area just like packing.

            "*Once we start drawing off our goal of ethyl alcohol still-head
            temperature *will not budge* while we draw off the product we are
            interested in. For example I use a Checktemp 1 digital Fahrenheit
            thermometer which remains absolutely locked within 1/10 of a F degree
            for at least 15 hours while my 96% Azeotrope is being collected."

            -i dont totally agree with this ( i do believe it was locked for 15
            hours though). Alex says he doesnt have to change his reflux ratio
            during the main run either. BUT if you started the still and had just
            enough reflux going on to get 96% then the pot % will start to lower
            and you will need more reflux, this may be only a tiny amount at a
            time but the need for reflux will increase if you are running at the
            bare minimum reflux needed for this purity. yourself and Alex do not
            have to change that RR since you run at such a high RR to begin with
            (a good idea).

            as for Smudge's goats

            C- it doesnt matter if he showed him the goat before he made the
            choice or after so it is a 50/50 chance, there may aswell be just one
            goat and one car.

            Peter
          • Johan
            ... Here is a picture of the column. Johan MIKE N- could you please comment on Johans 1/2 copper tube still. 95% from a 3% wash with no packing, what is going
            Message 5 of 17 , Mar 31, 2003
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              >
              ---
              Here is a picture of the column.

              Johan


              MIKE N- could you please comment on Johans 1/2" copper tube still.
              95% from a 3% wash with no packing, what is going on there! all i can
              consider is that the tube is so narrow that the vapour is exposed to
              a large surface area just like packing.
            • rodmacd2000
              Unless my eyes fail me what we have here is a (somewhat crude) version of the Vigreux fractionating still. Just serves to remind us that the packed column is
              Message 6 of 17 , Mar 31, 2003
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                Unless my eyes fail me what we have here is a (somewhat crude)
                version of the Vigreux fractionating still. Just serves to remind us
                that the packed column is not the only way to construct a
                fractionating column (just the best!).

                --- In Distillers@yahoogroups.com, "Johan" <mugg@h...> wrote:
                > >
                > ---
                > Here is a picture of the column.
                >
                > Johan
                >
                >
                > MIKE N- could you please comment on Johans 1/2" copper tube still.
                > 95% from a 3% wash with no packing, what is going on there! all i
                can
                > consider is that the tube is so narrow that the vapour is exposed
                to
                > a large surface area just like packing.
              • Mike Nixon
                peter_vcb wrote: Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?) MIKE N- could you please comment on Johans 1/2 copper tube still. 95%
                Message 7 of 17 , Mar 31, 2003
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                  peter_vcb wrote:
                  Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)

                  MIKE N- could you please comment on Johans 1/2" copper tube still.
                  95% from a 3% wash with no packing, what is going on there! all i can consider is that the tube is so narrow that the vapour is exposed to a large surface area just like packing.
                  =============================
                  Hi Peter,
                   
                  I'll give it a go, but first thanks to Johan for the pic.  Helps a lot, so I've shoved it in here as well
                  Rodmac is right ... with those indentations it's reminiscent of a Vigreux condenser that has its internal surface area increased by lots of indentations.
                  As I see it, the main feature of Johan's procedure is that it is deliberately kept very slow, so the vapor is moving up this column at a very low speed indeed.  As in a lyne arm, vapor will condense on the walls and some of this liquid will be re-evaporated to give vapor with a higher concentration of volatiles.  Stripped liquid will accumulate and trickle back down, and the richer vapor will condense a little further up to repeat the process.  As the vapor speed is very low, we can think of the column in Tony's terms as having a very small HETP, so we can envisage this liquid/vapor interchange being repeated many, many times before the vapor reaches the top, resulting in good separation.
                   
                  The low speed of the vapor is one important factor.  The other is the surface/volume ratio.  Same reasoning that we use with packing ... the greater the surface area of the liquid in a given volume of vapor, then the more efficient the evaporation interchange will be.  Now the ratio between the internal surface area of a tube and its volume (which will be the same thing as liquid surface area/vapor volume) is very simple: it's 4/D, where D is the diameter.  Other things like length and Pi all cancel out.  Johan is using 1/2" diameter tubing, so the ratio is 8.  Compare this with, say, a 2" diameter tube where the ratio is just 2.  He has also increased this ratio slightly by getting busy with his trusty Thor's Hammer, so the ratio could possibly be nearer 9 than 8.  We can also see that if he had used 1/4" diameter tubing them the ratio would be up to 16.
                   
                  I reckon that it is this combination of slow vapor speed and fairly high surface/volume ratio that makes Johan's method work so well.  I would also think that using several 1/4" diameter tubes would be even better ... the surface/volume ratio would remain the same of course (16), but the volume being processed would increase with every extra tube used.  However, if anyone cares to see is this works, I wouldn't bother with the indentations.  They are a good idea with 1/2" tubing, but the slight increase in surface area you would get with 1/4" diameter wouldn't be worth mangling a bunch of nice copper tubing that could be used for other purposes at another time.
                   
                  Make any sense?
                   
                  Mike N
                   


                • Johan
                  ... Från: Mike Nixon [mailto:mike@silverkey.co.nz] Skickat: den 31 mars 2003 23:20 Till: Distillers@yahoogroups.com Ämne: Re: [Distillers] Re: Reflux Valve =
                  Message 8 of 17 , Mar 31, 2003
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                    -----Ursprungligt meddelande-----
                    Från: Mike Nixon [mailto:mike@...]
                    Skickat: den 31 mars 2003 23:20
                    Till: Distillers@yahoogroups.com
                    Ämne: Re: [Distillers] Re: Reflux Valve = Temperature Controller (?)

                     

                    peter_vcb wrote:
                    Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)

                    MIKE N- could you please comment on Johans 1/2" copper tube still.
                    95% from a 3% wash with no packing, what is going on there! all i can consider is that the tube is so narrow that the vapour is exposed to a large surface area just like packing.

                    =============================

                    Hi Peter,

                     

                    I'll give it a go, but first thanks to Johan for the pic.  Helps a lot, so I've shoved it in here as well

                    Rodmac is right ... with those indentations it's reminiscent of a Vigreux condenser that has its internal surface area increased by lots of indentations.

                     

                    As I see it, the main feature of Johan's procedure is that it is deliberately kept very slow, so the vapor is moving up this column at a very low speed indeed. 

                    --

                    >

                    I should give it a try with much less heat, I have only tried it with 500-550W because of the thermostat regulated boiler, so vapour speed is high.

                    But the reflux was high as well when I got 95%

                    On the other hand reflux was low when I got 92% from about 12 % mash and 550W

                     

                    I wonder how it will work with less heat..

                    --

                     

                     As in a lyne arm, vapor will condense on the walls and some of this liquid will be re-evaporated to give vapor with a higher concentration of volatiles.  Stripped liquid will accumulate and trickle back down, and the richer vapor will condense a little further up to repeat the process.  As the vapor speed is very low, we can think of the column in Tony's terms as having a very small HETP, so we can envisage this liquid/vapor interchange being repeated many, many times before the vapor reaches the top, resulting in good separation.

                     

                    The low speed of the vapor is one important factor.  The other is the surface/volume ratio.  Same reasoning that we use with packing ... the greater the surface area of the liquid in a given volume of vapor, then the more efficient the evaporation interchange will be.  Now the ratio between the internal surface area of a tube and its volume (which will be the same thing as liquid surface area/vapor volume) is very simple: it's 4/D, where D is the diameter.  Other things like length and Pi all cancel out.  Johan is using 1/2" diameter tubing, so the ratio is 8.  Compare this with, say, a 2" diameter tube where the ratio is just 2.  He has also increased this ratio slightly by getting busy with his trusty Thor's Hammer, so the ratio could possibly be nearer 9 than 8.  We can also see that if he had used 1/4" diameter tubing them the ratio would be up to 16.

                     

                    I reckon that it is this combination of slow vapor speed and fairly high surface/volume ratio that makes Johan's method work so well.  I would also think that using several 1/4" diameter tubes would be even better ... the surface/volume ratio would remain the same of course (16), but the volume being processed would increase with every extra tube used.  However, if anyone cares to see is this works, I wouldn't bother with the indentations.  They are a good idea with 1/2" tubing, but the slight increase in surface area you would get with 1/4" diameter wouldn't be worth mangling a bunch of nice copper tubing that could be used for other purposes at another time.

                     

                    Make any sense?

                     

                    Mike N

                     

                     



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                  • Mike Nixon
                    Johan wrote: Subject: SV: [Distillers] Re: Reflux Valve = Temperature Controller (?) I should give it a try with much less heat, I have only tried it with
                    Message 9 of 17 , Mar 31, 2003
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                      Johan wrote:
                      Subject: SV: [Distillers] Re: Reflux Valve = Temperature Controller (?)

                      I should give it a try with much less heat, I have only tried it with 500-550W because of the thermostat regulated boiler, so vapour speed is high.
                      But the reflux was high as well when I got 95%
                      On the other hand reflux was low when I got 92% from about 12 % mash and 550W

                      I wonder how it will work with less heat..
                      ===========================================
                      Much better separation I reckon.  I had no idea you were running it at that power ... I had imagined that it was much lower.
                      At 550W, speed of vapor in a 1/2" diameter column is 109 cm/sec!  That is seriously FAST
                       
                      Mike N
                       
                    • peter_vcb
                      hi Mike makes lots of sense, thanks. i did an excel file after i posted yesterday to see the variance in the ratio just like you mention. i got different
                      Message 10 of 17 , Apr 1, 2003
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                        hi Mike
                        makes lots of sense, thanks. i did an excel file after i posted
                        yesterday to see the variance in the ratio just like you mention. i
                        got different ratios than you (i used mm) but same ratios between
                        diameters (i.e. 1/2" was 4 times 2"). i tried putting them into Tonys
                        calculators but gave up quickly! Johan initialy had an undeformed
                        tube and still got high strength. i am planning on making one with
                        several columns. i found out 1/2" 316 s/s tube is cheaper than copper
                        for me so i will use that (just over 2euro per metre). i figure that
                        i can add many columns and if they are tall enough and identical i
                        should get an even output from each of them (and hence run at high
                        power). i am thinking of columns 4 or 5 metres high without
                        insulation for the top metre to cause some ambient reflux. i think if
                        they are outdoors then the long fall of 4 metres on the output side
                        may mean they need no cooling at all. i will make one and get it
                        right before replicating the other columns.

                        Peter

                        --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
                        > peter_vcb wrote:
                        > Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)
                        >
                        > MIKE N- could you please comment on Johans 1/2" copper tube still.
                        > 95% from a 3% wash with no packing, what is going on there! all i
                        can consider is that the tube is so narrow that the vapour is exposed
                        to a large surface area just like packing.
                        > =============================
                        > Hi Peter,
                        >
                        > I'll give it a go, but first thanks to Johan for the pic. Helps a
                        lot, so I've shoved it in here as well
                        > Rodmac is right ... with those indentations it's reminiscent of a
                        Vigreux condenser that has its internal surface area increased by
                        lots of indentations.
                        >
                        > As I see it, the main feature of Johan's procedure is that it is
                        deliberately kept very slow, so the vapor is moving up this column at
                        a very low speed indeed. As in a lyne arm, vapor will condense on
                        the walls and some of this liquid will be re-evaporated to give vapor
                        with a higher concentration of volatiles. Stripped liquid will
                        accumulate and trickle back down, and the richer vapor will condense
                        a little further up to repeat the process. As the vapor speed is
                        very low, we can think of the column in Tony's terms as having a very
                        small HETP, so we can envisage this liquid/vapor interchange being
                        repeated many, many times before the vapor reaches the top, resulting
                        in good separation.
                        >
                        > The low speed of the vapor is one important factor. The other is
                        the surface/volume ratio. Same reasoning that we use with
                        packing ... the greater the surface area of the liquid in a given
                        volume of vapor, then the more efficient the evaporation interchange
                        will be. Now the ratio between the internal surface area of a tube
                        and its volume (which will be the same thing as liquid surface
                        area/vapor volume) is very simple: it's 4/D, where D is the
                        diameter. Other things like length and Pi all cancel out. Johan is
                        using 1/2" diameter tubing, so the ratio is 8. Compare this with,
                        say, a 2" diameter tube where the ratio is just 2. He has also
                        increased this ratio slightly by getting busy with his trusty Thor's
                        Hammer, so the ratio could possibly be nearer 9 than 8. We can also
                        see that if he had used 1/4" diameter tubing them the ratio would be
                        up to 16.
                        >
                        > I reckon that it is this combination of slow vapor speed and fairly
                        high surface/volume ratio that makes Johan's method work so well. I
                        would also think that using several 1/4" diameter tubes would be even
                        better ... the surface/volume ratio would remain the same of course
                        (16), but the volume being processed would increase with every extra
                        tube used. However, if anyone cares to see is this works, I wouldn't
                        bother with the indentations. They are a good idea with 1/2" tubing,
                        but the slight increase in surface area you would get with 1/4"
                        diameter wouldn't be worth mangling a bunch of nice copper tubing
                        that could be used for other purposes at another time.
                        >
                        > Make any sense?
                        >
                        > Mike N
                      • Mike Nixon
                        peter_vcb wrote: Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?) hi Mike makes lots of sense, thanks. i did an excel file after i posted
                        Message 11 of 17 , Apr 1, 2003
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                          peter_vcb wrote:
                          Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)

                          hi Mike
                          makes lots of sense, thanks. i did an excel file after i posted yesterday to see the variance in the ratio just like you mention. i
                          got different ratios than you (i used mm)  .....
                          ============================
                          Hi Peter,
                          The way I figured it, the circumference of a cylinder diameter D is (Pi)D, so the surface area is(Pi)DL
                          The volume of that cylinder is (Pi)D2L/4
                          so the ratio of surface area/volume came to 4(Pi)DL / (Pi)D2L  .... or 4/D
                          Snag is, the dimensions of this are "per length" so yes, the number you get will indeed depend on what units you use, so it's better to get rid of that length by comparing different tubes to get a dimensionless number.
                           
                          So if we compare tube A with diameter Da with tube B with diameter Db we get TubeA/Tube B = Db/Da
                          Suppose Tube A is 1/4 inches diameter and tube B is 2 inches diameter, we get Db/Da = 2*4 = 8
                          In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B is 2 * 25.4 mm diameter, and the ratio is again 8.
                          In words, Tube A has 8 times as much surface area per volume than tube B
                           
                          Better?
                          Mike N
                        • homedistiller
                          Hi all, I also follow, with interest, the pipe column experiments. On the next page, it says that a single, (insulated of course!) open tube column of 6 mm
                          Message 12 of 17 , Apr 2, 2003
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                            Hi all,
                            I also follow, with interest, the "pipe column" experiments.
                            On the next page, it says that a single, (insulated of course!) open
                            tube column of 6 mm (.25 inch) has a plate height of 80 cm for a
                            throughput of 10 ml/minute.

                            http://ull.chemistry.uakron.edu/chemsep/slide.html$Chapter=/chemsep/
                            distillation/&Last=34&Slide=31

                            I was thinking of just stretching a thin polypropylene rope, copper
                            electricity wire, stainless steel cable (2 or 3 mm diameter ?) inside
                            this column.
                            The slightest obstruction inside this pipe would instantly reduce the
                            plate height and thus create many more stages for the same length of
                            pipe. It would increase the contact surface, would reduce the
                            downward velocity of the reflux and a rope or a cable can be easily
                            removed for cleaning purposes.

                            As Mike Nixon proposed already in an earlier post, similar of those
                            "pipe columns" can be bundled in parallel.

                            Dirk




                            --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
                            > peter_vcb wrote:
                            > Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)
                            >
                            > hi Mike
                            > makes lots of sense, thanks. i did an excel file after i posted
                            yesterday to see the variance in the ratio just like you mention. i
                            > got different ratios than you (i used mm) .....
                            > ============================
                            > Hi Peter,
                            > The way I figured it, the circumference of a cylinder diameter D is
                            (Pi)D, so the surface area is(Pi)DL
                            > The volume of that cylinder is (Pi)D2L/4
                            > so the ratio of surface area/volume came to 4(Pi)DL / (Pi)D2L ....
                            or 4/D
                            > Snag is, the dimensions of this are "per length" so yes, the number
                            you get will indeed depend on what units you use, so it's better to
                            get rid of that length by comparing different tubes to get a
                            dimensionless number.
                            >
                            > So if we compare tube A with diameter Da with tube B with diameter
                            Db we get TubeA/Tube B = Db/Da
                            > Suppose Tube A is 1/4 inches diameter and tube B is 2 inches
                            diameter, we get Db/Da = 2*4 = 8
                            > In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B is
                            2 * 25.4 mm diameter, and the ratio is again 8.
                            > In words, Tube A has 8 times as much surface area per volume than
                            tube B
                            >
                            > Better?
                            > Mike N
                          • peter_vcb
                            Mike, yep i was working the same way using mm and using a standard length of 1m. so do you think Johans coiled copper tube idea would work as well or even
                            Message 13 of 17 , Apr 2, 2003
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                              Mike,
                              yep i was working the same way using mm and using a standard length
                              of 1m.
                              so do you think Johans coiled copper tube idea would work as well or
                              even better? if coiled the cooled vapour will flow down the tube
                              whereas if it is vertical it may fall straight down and the tube may
                              experience less wetting of the available surface. conversely it will
                              only flow on the lower section of the tube so vertical may be better.
                              if a coiled one would work it would easier to use indoors you could
                              have 10metres coiled to a low height. it could coil up fully
                              insulated and coil back down over itself with a fan blowing on it. i
                              still have this idea of a nice efficient radiator in my room pumping
                              out booze all day and keeping me warm :-)

                              if it scaled up perfectly (i know it wont) a 2" column would need to
                              be 6m high to work the same as the 1/2" 1.5m column. the cross
                              section area of a 2" column is 16 times that of a 1/2" column. so to
                              run at the same power i would need 16 columns at 1.5m which is 24m of
                              1/2" tube (56euro to me) compared to 6m of 2" tube (105euro). so has
                              anybody heard of a very high column run with no scrubbers? cheaper
                              than copper of s/s would be scaffolding poles. you could get 6m very
                              cheap and redistill the output to leave the nasties behind.

                              Peter


                              --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
                              > peter_vcb wrote:
                              > Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)
                              >
                              > hi Mike
                              > makes lots of sense, thanks. i did an excel file after i posted
                              yesterday to see the variance in the ratio just like you mention. i
                              > got different ratios than you (i used mm) .....
                              > ============================
                              > Hi Peter,
                              > The way I figured it, the circumference of a cylinder diameter D is
                              (Pi)D, so the surface area is(Pi)DL
                              > The volume of that cylinder is (Pi)D2L/4
                              > so the ratio of surface area/volume came to 4(Pi)DL / (Pi)D2L ....
                              or 4/D
                              > Snag is, the dimensions of this are "per length" so yes, the number
                              you get will indeed depend on what units you use, so it's better to
                              get rid of that length by comparing different tubes to get a
                              dimensionless number.
                              >
                              > So if we compare tube A with diameter Da with tube B with diameter
                              Db we get TubeA/Tube B = Db/Da
                              > Suppose Tube A is 1/4 inches diameter and tube B is 2 inches
                              diameter, we get Db/Da = 2*4 = 8
                              > In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B is
                              2 * 25.4 mm diameter, and the ratio is again 8.
                              > In words, Tube A has 8 times as much surface area per volume than
                              tube B
                              >
                              > Better?
                              > Mike N
                            • Aaron Pelly
                              Did you never get your low power input-air cooled-heater-still to work? I had forgotten about it actually. What progress _did_ you make? ... ...
                              Message 14 of 17 , Apr 2, 2003
                              • 0 Attachment
                                Did you never get your low power input-air cooled-heater-still to work?

                                I had forgotten about it actually.

                                What progress _did_ you make?

                                > -----Original Message-----
                                > From: peter_vcb [mailto:viciousblackout@...]
                                > Sent: Wednesday, 2 April 2003 21:55
                                > To: Distillers@yahoogroups.com
                                > Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)

                                <snip>
                                > i
                                > still have this idea of a nice efficient radiator in my room pumping
                                > out booze all day and keeping me warm :-)
                                <snip>
                              • peter_vcb
                                Hi Aaron i never actually tried it (it is made though). i made the air stripping still instead but it stank my room out and that was at 60C. my fan didnt have
                                Message 15 of 17 , Apr 2, 2003
                                • 0 Attachment
                                  Hi Aaron
                                  i never actually tried it (it is made though). i made the air
                                  stripping still instead but it stank my room out and that was at 60C.
                                  my fan didnt have much of a cooling effect on that so i presumed it
                                  would have had very little effect if it was actually boiling.

                                  for those who missed it my plan was to have my own reflux still run
                                  at such low power that it would only need air cooling and i could
                                  leave it on all day long. i ran my reflux still it at about 600W and
                                  got about 600ml per hour. if i made an "air liebeg" it may work. a
                                  large diameter pvc tube with the copper outlet tube in it and a fan
                                  blowing up it. Johans 1.5m 1/2" copper tube is a better and cheaper
                                  bet, very easy to make and gives the same output. if the copper
                                  outlet (or downturn on Johans) is long enough then it will cool by
                                  ambient air if the power is low enough. otherwise i would have the
                                  tube going into a worm in a bucket of water which would be changed
                                  daily. my other idea is an outdoor still like Johans 1/2" tube but
                                  have it about 5m high so it will be completely cool by the time it
                                  travels downturned 5m of tube. the downturn tube could also be filled
                                  with carbon to slow the distillate down to allow more cooling.

                                  Peter


                                  --- In Distillers@yahoogroups.com, "Aaron Pelly" <apelly@m...> wrote:
                                  > Did you never get your low power input-air cooled-heater-still to
                                  work?
                                  >
                                  > I had forgotten about it actually.
                                  >
                                  > What progress _did_ you make?
                                  >
                                  > > -----Original Message-----
                                  > > From: peter_vcb [mailto:viciousblackout@y...]
                                  > > Sent: Wednesday, 2 April 2003 21:55
                                  > > To: Distillers@yahoogroups.com
                                  > > Subject: [Distillers] Re: Reflux Valve = Temperature Controller
                                  (?)
                                  >
                                  > <snip>
                                  > > i
                                  > > still have this idea of a nice efficient radiator in my room
                                  pumping
                                  > > out booze all day and keeping me warm :-)
                                  > <snip>
                                • mwmccaw
                                  Peter, what you are describing begins to sound a lot like a gas chromatography column, which is often a very long coil of very fine tubing. The key problem I
                                  Message 16 of 17 , Apr 2, 2003
                                  • 0 Attachment
                                    Peter, what you are describing begins to sound a lot like a gas
                                    chromatography column, which is often a very long coil of very fine
                                    tubing.
                                    The key problem I see with what you describe will be heat loss - the
                                    smaller the column diameter, the faster the heat loss per unit
                                    length, so there will be a maximum length you can run - as soon as
                                    the column temperature falls below 78 deg C, you're hosed....
                                    You're right that you would have more potential area for reflux, and
                                    that it should proceed downward more slowly, but it will also only
                                    coat a fraction of the tube diameter.
                                    In short, worthy of an experiment!
                                    Mike McCaw



                                    --- In Distillers@yahoogroups.com, "peter_vcb"
                                    <viciousblackout@y...> wrote:
                                    > Mike,
                                    > yep i was working the same way using mm and using a standard
                                    length
                                    > of 1m.
                                    > so do you think Johans coiled copper tube idea would work as well
                                    or
                                    > even better? if coiled the cooled vapour will flow down the tube
                                    > whereas if it is vertical it may fall straight down and the tube
                                    may
                                    > experience less wetting of the available surface. conversely it
                                    will
                                    > only flow on the lower section of the tube so vertical may be
                                    better.
                                    > if a coiled one would work it would easier to use indoors you
                                    could
                                    > have 10metres coiled to a low height. it could coil up fully
                                    > insulated and coil back down over itself with a fan blowing on it.
                                    i
                                    > still have this idea of a nice efficient radiator in my room
                                    pumping
                                    > out booze all day and keeping me warm :-)
                                    >
                                    > if it scaled up perfectly (i know it wont) a 2" column would need
                                    to
                                    > be 6m high to work the same as the 1/2" 1.5m column. the cross
                                    > section area of a 2" column is 16 times that of a 1/2" column. so
                                    to
                                    > run at the same power i would need 16 columns at 1.5m which is 24m
                                    of
                                    > 1/2" tube (56euro to me) compared to 6m of 2" tube (105euro). so
                                    has
                                    > anybody heard of a very high column run with no scrubbers? cheaper
                                    > than copper of s/s would be scaffolding poles. you could get 6m
                                    very
                                    > cheap and redistill the output to leave the nasties behind.
                                    >
                                    > Peter
                                    >
                                    >
                                    > --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
                                    > > peter_vcb wrote:
                                    > > Subject: [Distillers] Re: Reflux Valve = Temperature Controller
                                    (?)
                                    > >
                                    > > hi Mike
                                    > > makes lots of sense, thanks. i did an excel file after i posted
                                    > yesterday to see the variance in the ratio just like you mention.
                                    i
                                    > > got different ratios than you (i used mm) .....
                                    > > ============================
                                    > > Hi Peter,
                                    > > The way I figured it, the circumference of a cylinder diameter D
                                    is
                                    > (Pi)D, so the surface area is(Pi)DL
                                    > > The volume of that cylinder is (Pi)D2L/4
                                    > > so the ratio of surface area/volume came to 4(Pi)DL / (Pi)
                                    D2L ....
                                    > or 4/D
                                    > > Snag is, the dimensions of this are "per length" so yes, the
                                    number
                                    > you get will indeed depend on what units you use, so it's better
                                    to
                                    > get rid of that length by comparing different tubes to get a
                                    > dimensionless number.
                                    > >
                                    > > So if we compare tube A with diameter Da with tube B with
                                    diameter
                                    > Db we get TubeA/Tube B = Db/Da
                                    > > Suppose Tube A is 1/4 inches diameter and tube B is 2 inches
                                    > diameter, we get Db/Da = 2*4 = 8
                                    > > In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B
                                    is
                                    > 2 * 25.4 mm diameter, and the ratio is again 8.
                                    > > In words, Tube A has 8 times as much surface area per volume
                                    than
                                    > tube B
                                    > >
                                    > > Better?
                                    > > Mike N
                                  • Johan
                                    I agree that heatloss probably is a problem, but insulate it may not be so hard since it is a coil. Johan Peter, what you are describing begins to sound a lot
                                    Message 17 of 17 , Apr 2, 2003
                                    • 0 Attachment
                                      I agree that heatloss probably is a problem, but insulate it may not be so
                                      hard since it is a coil.

                                      Johan

                                      Peter, what you are describing begins to sound a lot like a gas
                                      chromatography column, which is often a very long coil of very fine
                                      tubing.
                                      The key problem I see with what you describe will be heat loss - the
                                      smaller the column diameter, the faster the heat loss per unit
                                      length, so there will be a maximum length you can run - as soon as
                                      the column temperature falls below 78 deg C, you're hosed....
                                      You're right that you would have more potential area for reflux, and
                                      that it should proceed downward more slowly, but it will also only
                                      coat a fraction of the tube diameter.
                                      In short, worthy of an experiment!
                                      Mike McCaw



                                      --- In Distillers@yahoogroups.com, "peter_vcb"
                                      <viciousblackout@y...> wrote:
                                      > Mike,
                                      > yep i was working the same way using mm and using a standard
                                      length
                                      > of 1m.
                                      > so do you think Johans coiled copper tube idea would work as well
                                      or
                                      > even better? if coiled the cooled vapour will flow down the tube
                                      > whereas if it is vertical it may fall straight down and the tube
                                      may
                                      > experience less wetting of the available surface. conversely it
                                      will
                                      > only flow on the lower section of the tube so vertical may be
                                      better.
                                      > if a coiled one would work it would easier to use indoors you
                                      could
                                      > have 10metres coiled to a low height. it could coil up fully
                                      > insulated and coil back down over itself with a fan blowing on it.
                                      i
                                      > still have this idea of a nice efficient radiator in my room
                                      pumping
                                      > out booze all day and keeping me warm :-)
                                      >
                                      > if it scaled up perfectly (i know it wont) a 2" column would need
                                      to
                                      > be 6m high to work the same as the 1/2" 1.5m column. the cross
                                      > section area of a 2" column is 16 times that of a 1/2" column. so
                                      to
                                      > run at the same power i would need 16 columns at 1.5m which is 24m
                                      of
                                      > 1/2" tube (56euro to me) compared to 6m of 2" tube (105euro). so
                                      has
                                      > anybody heard of a very high column run with no scrubbers? cheaper
                                      > than copper of s/s would be scaffolding poles. you could get 6m
                                      very
                                      > cheap and redistill the output to leave the nasties behind.
                                      >
                                      > Peter
                                      >
                                      >
                                      > --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
                                      > > peter_vcb wrote:
                                      > > Subject: [Distillers] Re: Reflux Valve = Temperature Controller
                                      (?)
                                      > >
                                      > > hi Mike
                                      > > makes lots of sense, thanks. i did an excel file after i posted
                                      > yesterday to see the variance in the ratio just like you mention.
                                      i
                                      > > got different ratios than you (i used mm) .....
                                      > > ============================
                                      > > Hi Peter,
                                      > > The way I figured it, the circumference of a cylinder diameter D
                                      is
                                      > (Pi)D, so the surface area is(Pi)DL
                                      > > The volume of that cylinder is (Pi)D2L/4
                                      > > so the ratio of surface area/volume came to 4(Pi)DL / (Pi)
                                      D2L ....
                                      > or 4/D
                                      > > Snag is, the dimensions of this are "per length" so yes, the
                                      number
                                      > you get will indeed depend on what units you use, so it's better
                                      to
                                      > get rid of that length by comparing different tubes to get a
                                      > dimensionless number.
                                      > >
                                      > > So if we compare tube A with diameter Da with tube B with
                                      diameter
                                      > Db we get TubeA/Tube B = Db/Da
                                      > > Suppose Tube A is 1/4 inches diameter and tube B is 2 inches
                                      > diameter, we get Db/Da = 2*4 = 8
                                      > > In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B
                                      is
                                      > 2 * 25.4 mm diameter, and the ratio is again 8.
                                      > > In words, Tube A has 8 times as much surface area per volume
                                      than
                                      > tube B
                                      > >
                                      > > Better?
                                      > > Mike N



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