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Temperature control again

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  • Greg Denehy
    Hi all again, I still have absolutely no control over my head temperature. I have a 1 scrubber packed column, 600W heater, reflux condensor is a copper pipe
    Message 1 of 4 , Mar 21, 2003
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      Temperature control again

      Hi all again,
      I still have absolutely no control over my head temperature.
      I have a 1" scrubber packed column, 600W heater, reflux condensor is a copper pipe with watter running through it VERTICALLY inside an extension of the reflux column. Thermometer is sittin on top of this.

      I heat it up, run it on full full reflux for 15mins once vapour starts to rise up the tube.  I then back off the reflux water slowly until I see the temperature on the head start to rise.  It then usually gets too hot, so I slowly put in a little more reflux water.  The temperature immediately drops right off for about 5 minutes then heats up again to too high, so I add a little more water and the same thing happens again.

      Is this what is supposed to happen?
      If not, how am I supposed to reduce the temperature of the head?
      This same thing will happen at any heat setting I choose, just at different rates.

      The other odd thing I notice is that there is often nothing or very little coming out of the oulet, even tho the temperature is constant at 80C to 90C.  Why is this?

      I thought that if my thermometer is reading a temperature, then there must be vapour at the head…

      I hope you guys can help me, I just cant get this to work!

      Greg

      **********************
        Veni    Vedi    Velcro
      I came.  I saw.  I got stuck.
      **********************


    • Ackland, Tony (CALNZAS)
      Greg, That is a puzzler. Probably something easy to spot if were to pop around when you were next distilling, but cant quite do that. Maybe the next best
      Message 2 of 4 , Mar 22, 2003
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        Greg,

        That is a puzzler. Probably something easy to spot if were to pop around when you were next distilling, but cant quite do that. Maybe the next best thing would be a photo of the setup ? Or are there any other similar photographs at any sites ?

        >I have a 1" scrubber packed column, 600W heater, reflux condensor is a copper pipe with watter running through it VERTICALLY inside an extension of the reflux column. Thermometer is sittin on top of this.
        I heat it up, run it on full full reflux for 15mins once vapour starts to rise up the tube. I then back off the reflux water slowly until I see the temperature on the head start to rise. It then usually gets too hot,

        Thats the weird bit - if you are only slowly backing down the reflux ratio, then you should be able to keep control at the temp where you want it. Are you only doing very little adjustments, and waiting 2-3 minutes after each touch to see where it stabilises ? Sometimes controlling these is a bit like steering a huge ship - dont respond too fast, and only need the smallest touch. However, you should be able to control via that cooling water without needing too much precision - the only time precise control of the liquid flows is when directly metering the reflux itself. Have you tried just small changes, and then waiting quite a bit (5 min) for it to settle, before adjusting again ?

        If its rising too far after being at total reflux, then it simply sounds that you've reduced the reflux too much in that initial adjustment.

        > so I slowly put in a little more reflux water. The temperature immediately drops right off for about 5 minutes then heats up again to too high, so I add a little more water and the same thing happens again.

        I dont understand why it would drop then rise. Drop - yes - it means that the reflux is working, but the rise is then maybe a surge of hot vapour ? Could it be that the packing is too tight - the reflux is blocking it off, and then its eventually blowing a surge of hot vapour up past it ?

        One way to experiment with this would be to put in absolutely the minimum amount of packing (or even none), and see what the control is like - it should be more controllable, but just at a lower purity / higher temperature. Then just progressively add more packing as you learn how it wants to run ?

        > Is this what is supposed to happen?

        No - it should always be a nice steady progression.

        >If not, how am I supposed to reduce the temperature of the head?
        >This same thing will happen at any heat setting I choose, just at different rates.
        >The other odd thing I notice is that there is often nothing or very little coming out of the oulet, even tho the temperature is constant at 80C to 90C. Why is this?

        Rather than try and control at 80C, is it possible to control it at some other temperature - eg 82 or 84C ? Will it stabilise at a higher temperature ? Could it be that 78-80C is just too ambitios for the particular design, and its only capable of a lower purity ? In that case, you may only be getting the 78-80 when under total reflux, but that its impossible to operate there for longer

        >I thought that if my thermometer is reading a temperature, then there must be vapour at the head...

        True - if its hot, its because its in vapour. If theres vapour there, but its not coming out, thats because either its blocked off, or the head is running at total reflux.

        I hope we can get to the bottom of this and solve it for you.

        Tony
      • Robert N
        ... copper pipe with water running through it VERTICALLY inside an extension of the reflux column. Thermometer is sitting on top of this is it that the
        Message 3 of 4 , Mar 23, 2003
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          >I have a 1" scrubber packed column, 600W heater, reflux condenser is a copper pipe with water running through it >VERTICALLY inside an extension of the reflux column. Thermometer is sitting on top of this

           

          is it that the thermometer is sitting ABOVE the condenser? If it is, move the thermometer to below the condenser. As Tony said, remove half the packing (scrubbers) and I would also only add half fill the boiler. Then do another run. This way you eliminate any potential for flooding, etc because of what YOU are doing and then concentrate on what the COLUMN is doing. This way you can take a systematic approach, best of luck.

           

           

          Yours in Spirit

           

           

          Robert

           

           

          -----Original Message-----
          From: Ackland, Tony (CALNZAS) [mailto:Tony.Ackland@...]
          Sent
          :
          Sunday, March 23, 2003 6:43 AM
          To: new_distillers@yahoogroups.com
          Subject: RE: [new_distillers] Temperature control again

           

          Greg,

          That is a puzzler.  Probably something easy to spot if were to pop around when you were next distilling, but  cant quite do that.  Maybe the next best thing would be a photo of the setup ?  Or are there any other similar photographs at any sites ?

          >I have a 1" scrubber packed column, 600W heater, reflux condensor is a copper pipe with watter running through it VERTICALLY inside an extension of the reflux column. Thermometer is sittin on top of this.
          I heat it up, run it on full full reflux for 15mins once vapour starts to rise up the tube.  I then back off the reflux water slowly until I see the temperature on the head start to rise.  It then usually gets too hot,

          Thats the weird bit - if you are only slowly backing down the reflux ratio, then you should be able to keep control at the temp where you want it.  Are you only doing very little adjustments, and waiting 2-3 minutes after each touch to see where it stabilises ?  Sometimes controlling these is a bit like steering a huge ship - dont respond too fast, and only need the smallest touch.    However, you should be able to control via that cooling water without needing too much precision - the only time precise control of the liquid flows is when directly metering the reflux itself.  Have you tried just small changes, and then waiting quite a bit (5 min) for it to settle, before adjusting again ?

          If its rising too far after being at total reflux, then it simply sounds that you've reduced the reflux too much in that initial adjustment.

          > so I slowly put in a little more reflux water.  The temperature immediately drops right off for about 5 minutes then heats up again to too high, so I add a little more water and the same thing happens again.

          I dont understand why it would drop then rise.  Drop - yes - it means that the reflux is working, but the rise is then maybe a surge of hot vapour ?  Could it be that the packing is too tight - the reflux is blocking it off, and then its eventually blowing a surge of hot vapour up past it ?

          One way to experiment with this would be to put in absolutely the minimum amount of packing (or even none), and see what the control is like - it should be more controllable, but just at a lower purity / higher temperature.  Then just progressively add more packing as you learn how it wants to run ?

          > Is this what is supposed to happen?

          No - it should always be a nice steady progression.

          >If not, how am I supposed to reduce the temperature of the head?
          >This same thing will happen at any heat setting I choose, just at different rates.
          >The other odd thing I notice is that there is often nothing or very little coming out of the oulet, even tho the temperature is constant at 80C to 90C.  Why is this?

          Rather than try and control at 80C, is it possible to control it at some other temperature - eg 82 or 84C ?  Will it stabilise at a higher temperature ? Could it be that 78-80C is just too ambitios for the particular design, and its only capable of a lower purity ?  In that case, you may only be getting the 78-80 when under total reflux, but that its impossible to operate there for longer

          >I thought that if my thermometer is reading a temperature, then there must be vapour at the head...

          True - if its hot, its because its in vapour.  If theres vapour there, but its not coming out, thats because either its blocked off, or the head is running at total reflux.

          I hope we can get to the bottom of this and solve it for you.

          Tony


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        • glasses97
          ... I experience the same phenomena when my column floods. The boiling is going like crazy, the temp at the top of the column raises rapidly and I get no or
          Message 4 of 4 , Mar 23, 2003
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            --- In new_distillers@yahoogroups.com, "Greg Denehy" <greg@t...> wro

            I experience the same phenomena when my column floods. The boiling is
            going like crazy, the temp at the top of the column raises rapidly
            and I get no or almost no output. Reduce the amount of liquid in
            your boiler or take some packing out of the BOTTOM part of your
            column, again increasing the distance from the fluid to the packing.

            Hope this helps

            Glasses 97


            > Hi all again,
            > I still have absolutely no control over my head temperature.
            > I have a 1" scrubber packed column, 600W heater, reflux condensor
            is a
            > copper pipe with watter running through it VERTICALLY inside an
            > extension of the reflux column. Thermometer is sittin on top of
            this.
            >
            > I heat it up, run it on full full reflux for 15mins once vapour
            starts
            > to rise up the tube. I then back off the reflux water slowly until
            I
            > see the temperature on the head start to rise. It then usually
            gets too
            > hot, so I slowly put in a little more reflux water. The temperature
            > immediately drops right off for about 5 minutes then heats up again
            to
            > too high, so I add a little more water and the same thing happens
            again.
            >
            > Is this what is supposed to happen?
            > If not, how am I supposed to reduce the temperature of the head?
            > This same thing will happen at any heat setting I choose, just at
            > different rates.
            >
            > The other odd thing I notice is that there is often nothing or very
            > little coming out of the oulet, even tho the temperature is
            constant at
            > 80C to 90C. Why is this?
            > I thought that if my thermometer is reading a temperature, then
            there
            > must be vapour at the head.
            >
            > I hope you guys can help me, I just cant get this to work!
            >
            > Greg
            >
            > **********************
            > Veni Vedi Velcro
            > I came. I saw. I got stuck.
            > **********************
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