Loading ...
Sorry, an error occurred while loading the content.

Re: Vacuum Distillation Column

Expand Messages
  • brzdistiller
    I really cant help you much, but two articles came to mind that I think you and others might want to check out. Both are about the guys at the French Culinary
    Message 1 of 9 , Mar 31 9:25 AM
    • 0 Attachment
      I really cant help you much, but two articles came to mind that I think you and others might want to check out.

      Both are about the guys at the French Culinary Institute using a Rotovap to distill under vacuum.

      Not at all the same, but some principles might apply.


      Rotovap Primer: http://www.cookingissues.com/primers/rotovap/

      Head to Tail Drinking: Breaking up Distillations in the Rotovap: http://www.cookingissues.com/2010/05/19/head-to-tail-drinking-breaking-up-distillations-in-the-rotovap/

      Cheers,

      TH



      --- In Distillers@yahoogroups.com, "bjpow42o" <bjpow42o@...> wrote:
      >
      > I am trying to separate alcohol from a solution under a near vacuum. I would like to achieve around 95% abv and I was wondering if a fractionating column would be necessary to do so. If so, what kind of packing should I use? Would the dimensions of the fractionating column and the number of trays/plates need to be different than a conventional column (one not under vacuum)?
      > Thanks in advance!
      >
    • landrover_ffr
      Hi, I ve did some investigation in distilling under vacuum a while back. I have some fairly detail information in my archive. I will look for it when I get
      Message 2 of 9 , Apr 2, 2011
      • 0 Attachment
        Hi,
        I've did some investigation in distilling under vacuum a while back. I have some fairly detail information in my archive. I will look for it when I get home. As a starting point I would say...
        a) Yyou will still need a column. Introducing a vacuum only really lowers the energy required to separate the components. You will still need surface area to allow the interaction between the liquid and vapor phases.
        b) Good old S/steel scrubbers would/should still do a fine job due to there high surface area and good turndown ratio (unless you are using a large diameter column i.e. greater than 3 inches or so)
        c) Sizing depends on a huge number of factors. I'd advise sticking with one of the many good sizings used by those here i.e. about 2 inches, by as high as particle, packed with scrubbers (unless you intend getting a masters degree in engineering ;)
        d) the trick will be getting the vacuum setup functioning correctly. You talked about using "a near vacuum", that scares me a little ;) Just how much vacuum do you intend pulling inside the column?
        Regards,
        Sid.


        --- In Distillers@yahoogroups.com, "bjpow42o" <bjpow42o@...> wrote:
        >
        > I am trying to separate alcohol from a solution under a near vacuum. I would like to achieve around 95% abv and I was wondering if a fractionating column would be necessary to do so. If so, what kind of packing should I use? Would the dimensions of the fractionating column and the number of trays/plates need to be different than a conventional column (one not under vacuum)?
        > Thanks in advance!
        >
      • bjpow42o
        Thanks for the information Sid. Right now I have a small scale experimental setup without a column. The vacuum pump pulls down to 40 torr, that s what I meant
        Message 3 of 9 , Apr 4, 2011
        • 0 Attachment
          Thanks for the information Sid.
          Right now I have a small scale experimental setup without a column. The vacuum pump pulls down to 40 torr, that's what I meant "near" vacuum... why does that scare you? I read somewhere that at pressures of 70 torr or less the water/alcohol azeotrope does not exist. That made me think that I could get nearly pure alcohol through a single run simple distillation. It sounds like this is not the case. If I set the temperature no higher than the boiling point of alcohol at 40 torr could I not get pure alcohol off?
          I am looking to scale up the design to about 50 liter capacity. I was planning on using SS scrubbers in the column if I can, but I am unsure of the size of the column and reflux ratio (if needed?). I also read somewhere that it is better to have a wider column when distilling under a vacuum for some reason. Have you heard this before? Any ideas on the height of the column (didn't understand "by as high as particle")? I'm trying to avoid getting another engineering degree if possibile :)
          Any further information from your past research would be greatly appreciated.
          Thanks again!

          --- In Distillers@yahoogroups.com, "landrover_ffr" <sid.rains@...> wrote:
          >
          > Hi,
          > I've did some investigation in distilling under vacuum a while back. I have some fairly detail information in my archive. I will look for it when I get home. As a starting point I would say...
          > a) Yyou will still need a column. Introducing a vacuum only really lowers the energy required to separate the components. You will still need surface area to allow the interaction between the liquid and vapor phases.
          > b) Good old S/steel scrubbers would/should still do a fine job due to there high surface area and good turndown ratio (unless you are using a large diameter column i.e. greater than 3 inches or so)
          > c) Sizing depends on a huge number of factors. I'd advise sticking with one of the many good sizings used by those here i.e. about 2 inches, by as high as particle, packed with scrubbers (unless you intend getting a masters degree in engineering ;)
          > d) the trick will be getting the vacuum setup functioning correctly. You talked about using "a near vacuum", that scares me a little ;) Just how much vacuum do you intend pulling inside the column?
          > Regards,
          > Sid.
          >
          >
          > --- In Distillers@yahoogroups.com, "bjpow42o" <bjpow42o@> wrote:
          > >
          > > I am trying to separate alcohol from a solution under a near vacuum. I would like to achieve around 95% abv and I was wondering if a fractionating column would be necessary to do so. If so, what kind of packing should I use? Would the dimensions of the fractionating column and the number of trays/plates need to be different than a conventional column (one not under vacuum)?
          > > Thanks in advance!
          > >
          >
        • tgfoitwoods
          bjpow, This is a very interesting restatement of the oldest misconception in spirit distillation, that by holding the boiling point (at any pressure) lower
          Message 4 of 9 , Apr 4, 2011
          • 0 Attachment
            bjpow,

            This is a very interesting restatement of the oldest misconception in
            spirit distillation, that by holding the boiling point (at any pressure)
            lower than the boiling point of water but greater than the boiling point
            of ethanol, only ethanol will vaporize from the wash. While it sounds ok
            at first blush, it's just not true.

            The proportions of water and ethanol in tha vapor are controlled by
            their respective vapor pressure as a fraction of the ambient pressure,
            even when that pressure has been lowered from atmospheric nominal 760mm
            Hg. The individual vapor pressures are determined by both the vapor
            pressure of the pure liquid (water or EtOH) and the mole fraction of
            that compound, that is, what fraction of the total molarity of the
            solution is that concentration. None of this changes with pressure.

            An unhappy side effect of keeping a depressed wash temperature is that a
            water-ethanol mixture has a very sepcific boiling point (at any given
            pressure) and until the wash is heated to that temperature, vaporization
            is painfully slow.

            In summary, if you are able to hold a 10% wash, which boils at 90C, at a
            steady temp of 80C, just a bit over the boiling point of ethanol, you'd
            get a vapor with about a 60% ethanol content, but you'd get it so slowly
            that you'd never do it again.

            Note that I'm speaking wash and vapor temperature here, and NOT the
            temperature that reflux 'stillers measure at the tops of their columns;
            that's something entirely different.

            Zymurgy Bob, a simple potstiller

            --- In Distillers@yahoogroups.com, "bjpow42o" <bjpow42o@...> wrote:
            >
            >
            >
            > Thanks for the information Sid.
            > Right now I have a small scale experimental setup without a column.
            The vacuum pump pulls down to 40 torr, that's what I meant "near"
            vacuum... why does that scare you? I read somewhere that at pressures
            of 70 torr or less the water/alcohol azeotrope does not exist. That
            made me think that I could get nearly pure alcohol through a single run
            simple distillation. It sounds like this is not the case. If I set the
            temperature no higher than the boiling point of alcohol at 40 torr could
            I not get pure alcohol off?
            > I am looking to scale up the design to about 50 liter capacity. I was
            planning on using SS scrubbers in the column if I can, but I am unsure
            of the size of the column and reflux ratio (if needed?). I also read
            somewhere that it is better to have a wider column when distilling under
            a vacuum for some reason. Have you heard this before? Any ideas on the
            height of the column (didn't understand "by as high as particle")? I'm
            trying to avoid getting another engineering degree if possibile :)
            > Any further information from your past research would be greatly
            appreciated.
            > Thanks again!
            >
            ----snip----
          • landrover_ffr
            Hi, Comments inserted bellow. ... Just checking. In my world you either pull a vacuum , or not. The term near vacuum got me worried that you had very little
            Message 5 of 9 , Apr 6, 2011
            • 0 Attachment
              Hi,
              Comments inserted bellow.

              > The vacuum pump pulls down to 40 torr, that's what I meant "near" vacuum... why does that scare you?
              Just checking. In my world you either pull a vacuum , or not. The term "near vacuum" got me worried that you had very little idea as to what you were attempting to do. Sorry.

              >I read somewhere that at pressures of 70 torr or less the water/alcohol azeotrope does not exist.
              That sounds familiar. Once the vacuum is removed though it will absorb moisture from the air again I believe. 40 torr is only about 1.5 psi if a remember correct, so not too bad to deal with.

              >If I set the temperature no higher than the boiling point of alcohol at 40 torr could I not get pure alcohol off?
              Nope, still need reflux to achieve the separation. As noted by another poster, the whole "temperature setting" concept is a fools errand.

              > I am looking to scale up the design to about 50 liter capacity. I was planning on using SS scrubbers in the column if I can, but I am unsure of the size of the column and reflux ratio (if needed?).
              Sound like an ok plan. I can't tell you what R/R to run (I could implement vacuum distillation in my software/model and see how it turns out). The key with the vacuum will be requiring less power input.

              >I also read somewhere that it is better to have a wider column when distilling under a vacuum for some reason.
              I've not herd this before. This is usually base on the moler flow rate expected in the column (among other things ;)

              >Any ideas on the height of the column (didn't understand "by as high as particle")?
              Sorry, my bad typing (after few too many glasses ;) I meant to say "as high/tall as practical".

              >I'm trying to avoid getting another engineering degree if possibile :)
              Yes, one is more than enough! I garner the help of two of my mates when things get too serious (one is a chemical engineer, the other and refrigeration engineer (among other things, two much education all together!)

              Hope this help a little. I try too be of more use asap.

              Regards,
              Sid.
            • bjpow42o
              OK, sounds good. I do have another question... I am trying to get 95% abv off the top of the column. However, I would also like to remove most of the water
              Message 6 of 9 , Apr 7, 2011
              • 0 Attachment
                OK, sounds good. I do have another question...

                I am trying to get 95% abv off the top of the column. However, I would also like to remove most of the water from the solution in the boiler at the same time. Does anyone have a good idea on how to do this? I have a couple, but I am not sure how well they will work.

                The first is instead of connecting the column to the top of the boiler tank I would have the column free standing next to the boiler and have the vapor feed into the side of the tower near the bottom. Then the alcohol vapor would rise to the outlet of the column on the top and to the condenser while the water vapor would fall into a receiving tank at the bottom of the column (which could be cooled to prevent reboiling if necessary). I know I may not capture all of the alcohol this way, but a good portion of it hopefully while still getting 95% off the top of the column.

                Another idea, which I am trying to avoid because it would most likely be more energy intensive, is to basically have a multi-stage distillation. The first would act as a pot still and take of all of the alcohol and most of the water and feed it into another boiler tank. The next stage would be a traditional fractional distillation with the column directly on the boiler tank. I think this would work, but I am looking for a way to do this without heating twice.

                Any ideas? Thanks again for all the helpful wisdom!

                --- In Distillers@yahoogroups.com, "landrover_ffr" <sid.rains@...> wrote:
                >
                > Hi,
                > Comments inserted bellow.
                >
                > > The vacuum pump pulls down to 40 torr, that's what I meant "near" vacuum... why does that scare you?
                > Just checking. In my world you either pull a vacuum , or not. The term "near vacuum" got me worried that you had very little idea as to what you were attempting to do. Sorry.
                >
                > >I read somewhere that at pressures of 70 torr or less the water/alcohol azeotrope does not exist.
                > That sounds familiar. Once the vacuum is removed though it will absorb moisture from the air again I believe. 40 torr is only about 1.5 psi if a remember correct, so not too bad to deal with.
                >
                > >If I set the temperature no higher than the boiling point of alcohol at 40 torr could I not get pure alcohol off?
                > Nope, still need reflux to achieve the separation. As noted by another poster, the whole "temperature setting" concept is a fools errand.
                >
                > > I am looking to scale up the design to about 50 liter capacity. I was planning on using SS scrubbers in the column if I can, but I am unsure of the size of the column and reflux ratio (if needed?).
                > Sound like an ok plan. I can't tell you what R/R to run (I could implement vacuum distillation in my software/model and see how it turns out). The key with the vacuum will be requiring less power input.
                >
                > >I also read somewhere that it is better to have a wider column when distilling under a vacuum for some reason.
                > I've not herd this before. This is usually base on the moler flow rate expected in the column (among other things ;)
                >
                > >Any ideas on the height of the column (didn't understand "by as high as particle")?
                > Sorry, my bad typing (after few too many glasses ;) I meant to say "as high/tall as practical".
                >
                > >I'm trying to avoid getting another engineering degree if possibile :)
                > Yes, one is more than enough! I garner the help of two of my mates when things get too serious (one is a chemical engineer, the other and refrigeration engineer (among other things, two much education all together!)
                >
                > Hope this help a little. I try too be of more use asap.
                >
                > Regards,
                > Sid.
                >
              • Stillton
                continuous distillation is probably the concept you are looking for. you should probably start with getting one of these concepts running before you try them
                Message 7 of 9 , May 7, 2011
                • 0 Attachment
                  continuous distillation is probably the concept you are looking for. you should probably start with getting one of these concepts running before you try them together.

                  in continuous distillation you should have a small reboiler in the bottom of the column and feed the mash half way up (well, as a general rule, but it will depend on your setup, and what you are trying to achieve).

                  to give you a basic idea.. put a 1500W small boiler under a 2 meter (7 feet) 2" LM column with packing. feed mash into it halfway up. pull of "water" from the boiler at 98-99C. use the waste water to preheat the mash for better efficiency.

                  you now have a continuous stripper that gets rid of most water and tails.
                  to achieve azeotropic ethanol, you will (probably) need a second column that draws tails from the bottom, and heads and ethanol in the top. then a third column that gives ethanol in the bottom and heads in the top.
                  to get this working in balance is not a simple task but can save you some energy if done correctly. (this is how the "big boys" vodka factories produce there ethanol).

                  but since you are trying to get rid of the water, im guessing you might be trying to produce fuel, and not drinking alcohol?
                  in this case you could use the first column as a stripper, and apply vacuum to the second column, your car will run fine on heads and ethanol, even if it doesn't taste well.
                • abbababbaccc
                  For stripping you should feed the mash to the top to use the column at it s full effect. With well balanced stripper high 80s or even 90s ABV is possible while
                  Message 8 of 9 , May 7, 2011
                  • 0 Attachment
                    For stripping you should feed the mash to the top to use the column at it's full effect. With well balanced stripper high 80s or even 90s ABV is possible while leaving most of the tails to the boiler. I don't know if that's enough for fuel use though. If you want to build something continuous I'd suggest keeping it simple and adding those efficiency improving heat exchangers once you have the rig up and working.

                    Slainte, Riku

                    --- In Distillers@yahoogroups.com, "Stillton" <stillton@...> wrote:
                    >
                    > continuous distillation is probably the concept you are looking for. you should probably start with getting one of these concepts running before you try them together.
                    >
                    > in continuous distillation you should have a small reboiler in the bottom of the column and feed the mash half way up (well, as a general rule, but it will depend on your setup, and what you are trying to achieve).
                    >
                    > to give you a basic idea.. put a 1500W small boiler under a 2 meter (7 feet) 2" LM column with packing. feed mash into it halfway up. pull of "water" from the boiler at 98-99C. use the waste water to preheat the mash for better efficiency.
                    >
                    > you now have a continuous stripper that gets rid of most water and tails.
                    > to achieve azeotropic ethanol, you will (probably) need a second column that draws tails from the bottom, and heads and ethanol in the top. then a third column that gives ethanol in the bottom and heads in the top.
                    > to get this working in balance is not a simple task but can save you some energy if done correctly. (this is how the "big boys" vodka factories produce there ethanol).
                    >
                    > but since you are trying to get rid of the water, im guessing you might be trying to produce fuel, and not drinking alcohol?
                    > in this case you could use the first column as a stripper, and apply vacuum to the second column, your car will run fine on heads and ethanol, even if it doesn't taste well.
                    >
                  Your message has been successfully submitted and would be delivered to recipients shortly.