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still surging, hot distillate.

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  • chris jude
    Folks, I d love a little wisdom here. We ve just begun using our 100 gallon pot still with thumper. The system is heated by low pressure steam, and we have
    Message 1 of 5 , Jan 17, 2014
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      Folks,  I'd love a little wisdom here.  We've just begun using our 100 gallon pot still with thumper.  The system is heated by low pressure steam, and we have two tube in shell condensors, the first is cooled by 55 deg well water, the second is cooled by a recirculation tank.  This is the second time we've run it, and we've had really bad surging and the distillate has jumped in temperature a few times somewhat randomly.
      This morning we were running for about an hour and a half and everything was fine and balanced, distillate coming out at 66 degrees with just one condenser running.  Water input was around 55 degrees, output around 140 degrees.  I shut the dephlegmator off on the thumper, which caused more water to flow through the condenser, water output temperature dropped to around 70 degrees.  Soon after that the distillate temp jumped up to over 100 degrees, while the jacket of the condenser remained cool to the touch.  The system chugged and spit distillate out the parrot.  As far as I could tell, the cooling water continued to flow, but suddenly the condenser was not cooling the distillate properly.  There is a chance that the water valve was clogged by debris, but when i took it apart, it appeared clean.
      I'm puzzled, after the first instance, it happened again, in the same manner, for several minutes the distillate came through hot, I turned the steam down slightly, and the turned the cooling water down till i saw a water temperature rise across the condenser.  I can't pinpoint what is happening here.  Any ideas?

      Chris
    • DAVE DELANEY
      Chris, have you checked the temperature of the mash in the still? It should be well below the boiling point of water..it should simmer rather than boil. If it
      Message 2 of 5 , Jan 17, 2014
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        Chris, have you checked the temperature of the mash in the still? It should be well below the boiling point of water..it should simmer rather than boil. If it boils, you will get too much water in the distillate, even possible spurts of raw water. Perhaps slow down your steam delivery rate. Can you post a pix.? That might help... even an accurate drawing...

        Dave
         
         
         
         
         


        On Friday, January 17, 2014 1:41:26 PM, chris jude <vegbenz300@...> wrote:
         
        Folks,  I'd love a little wisdom here.  We've just begun using our 100 gallon pot still with thumper.  The system is heated by low pressure steam, and we have two tube in shell condensors, the first is cooled by 55 deg well water, the second is cooled by a recirculation tank.  This is the second time we've run it, and we've had really bad surging and the distillate has jumped in temperature a few times somewhat randomly.
        This morning we were running for about an hour and a half and everything was fine and balanced, distillate coming out at 66 degrees with just one condenser running.  Water input was around 55 degrees, output around 140 degrees.  I shut the dephlegmator off on the thumper, which caused more water to flow through the condenser, water output temperature dropped to around 70 degrees.  Soon after that the distillate temp jumped up to over 100 degrees, while the jacket of the condenser remained cool to the touch.  The system chugged and spit distillate out the parrot.  As far as I could tell, the cooling water continued to flow, but suddenly the condenser was not cooling the distillate properly.  There is a chance that the water valve was clogged by debris, but when i took it apart, it appeared clean.
        I'm puzzled, after the first instance, it happened again, in the same manner, for several minutes the distillate came through hot, I turned the steam down slightly, and the turned the cooling water down till i saw a water temperature rise across the condenser.  I can't pinpoint what is happening here.  Any ideas?

        Chris


      • chris jude
        The mash is around 200-202F. Attached is a photo, not sure if this will go to the list? We ve changed the condensers from this picture, they are now stacked
        Message 3 of 5 , Jan 17, 2014
        The mash is around 200-202F.  Attached is a photo, not sure if this will go to the list? 
        We've changed the condensers from this picture,  they are now stacked vertically, with the vapor passing through the tubes and the water in the shell.
        I'm thinking that the water line was clogging?  It's just odd.  We had a leak at one of the temp sensors on the doubler, when we plugged that, the temperature and surging started.
        Maybe I've just got the heating and cooling out of balance?  I've got it running again now and every thing is smooth, and i turned on the secondary condenser to be sure that the vapor is cool enough

        chris


        On Fri, Jan 17, 2014 at 12:51 PM, DAVE DELANEY <daveandsue@...> wrote:
         

        Chris, have you checked the temperature of the mash in the still? It should be well below the boiling point of water..it should simmer rather than boil. If it boils, you will get too much water in the distillate, even possible spurts of raw water. Perhaps slow down your steam delivery rate. Can you post a pix.? That might help... even an accurate drawing...

        Dave
         
         
         
         
         


        On Friday, January 17, 2014 1:41:26 PM, chris jude <vegbenz300@...> wrote:
         
        Folks,  I'd love a little wisdom here.  We've just begun using our 100 gallon pot still with thumper.  The system is heated by low pressure steam, and we have two tube in shell condensors, the first is cooled by 55 deg well water, the second is cooled by a recirculation tank.  This is the second time we've run it, and we've had really bad surging and the distillate has jumped in temperature a few times somewhat randomly.
        This morning we were running for about an hour and a half and everything was fine and balanced, distillate coming out at 66 degrees with just one condenser running.  Water input was around 55 degrees, output around 140 degrees.  I shut the dephlegmator off on the thumper, which caused more water to flow through the condenser, water output temperature dropped to around 70 degrees.  Soon after that the distillate temp jumped up to over 100 degrees, while the jacket of the condenser remained cool to the touch.  The system chugged and spit distillate out the parrot.  As far as I could tell, the cooling water continued to flow, but suddenly the condenser was not cooling the distillate properly.  There is a chance that the water valve was clogged by debris, but when i took it apart, it appeared clean.
        I'm puzzled, after the first instance, it happened again, in the same manner, for several minutes the distillate came through hot, I turned the steam down slightly, and the turned the cooling water down till i saw a water temperature rise across the condenser.  I can't pinpoint what is happening here.  Any ideas?

        Chris



      • azeo2
        any updates? A number of issues can causes the problems you describe. Interesting that a pot-like still has a dephleg on top without a column. Without a column
        Message 4 of 5 , Feb 4, 2014
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          any updates? A number of issues can causes the problems you describe. Interesting that a pot-like still has a dephleg on top without a column. Without a column to raise proof through managed reflux+height, the dephleg is mainly acting as a way to control the amount of vapor entering the product condensors.  Any reflux is going straight back into the boiler again to be reboiled - alot of wasted energy for very little gain when controlling/reducing the amount of energy going into the boiler would acheive the same result.

          Often tube and shell dephlegs "choke" when overdriven this can casue surgig as the vapor blows through the liquid, likewise if any of the product condensors or parrot form a liquid trap, surging will ocurr as the still "breathes".

           

          Another issue known to cause surging or resonance in a unit is sudden cooling of a large amount of vapor when it first enters the condensor, this creates a temporary partial vacuum that sucks in air from the outside, followed by pressure from the boiler driving vapor out. The frequency is set by the size of the still, length and diamater of piping, condesnors etc, energy balance etc, and can be fast huffing or puffing in a small still, or slow surging in a larger still/longer piping system. Seems to be common practice to have the coldest cooling water entering condensors at the bottom/product exit, in a stacked system that may be your well water for the bottom one, and the recirculated supply for the first.

           

          If the thumper is flooding, that could cause surging too. This being the second time running the still, depending on previous experience, a "gentle" start-up regime and practise runs would be the "go" to get the feel for energy balance and control. In the early stages i'ts best to use only the amount of energy/steam to produce gentle simmering and plenty of time to get used to various controls at minumum settings, this helps minimse "overshoot" and having to "tune" several things at once; take-off rates can be checked, proof and distillation times stabilised and measured etc., and a feel for the "cuts" established.

           

          If things seem sweet, and under control and a desire is then for faster batches/higher take off, the energy in can be incremented up, dephleg adjusted until the sweet spot is found for most efficient or timely use without surging, spitting, or excessive use of cooling water in the phleg to compensate for an over-driven boiler. Insulating the boiler is going to save some energy too.

           

          Just a few ideas/comments, hope they may be useful. I know others could chime in too. The usual disclaimer applies. Good luck!

        • chris jude
          Thanks for your post. It was very informative and good to read. After several more runs, I seem to be able to control the surging much better. We
          Message 5 of 5 , Feb 24, 2014
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            Thanks for your post.  It was very informative and good to read.

            After several more runs, I seem to be able to control the surging much better.  We repositioned the condensers into a vertical position with the vapor traveling through tubes and the cooling water in the shell.  Then, we put a vent condenser inline above the condensers.  This is to allow some noncondensable vapors out while keeping condensable vapors headed down through the product condensers.  I've also been keeping the cooling water (which does flow up through the condensers as you recommend) slow enough that it comes out up top around 140-170 deg F. 
            I believe, though I still was never able to quite nail down the cause, that it was an inbalance between heating and cooling that was pulling a vacuum and sucking air in through the check valve, causing the surge. 




            On Wed, Feb 5, 2014 at 2:07 AM, <azeo2@...> wrote:
             

            any updates? A number of issues can causes the problems you describe. Interesting that a pot-like still has a dephleg on top without a column. Without a column to raise proof through managed reflux+height, the dephleg is mainly acting as a way to control the amount of vapor entering the product condensors.  Any reflux is going straight back into the boiler again to be reboiled - alot of wasted energy for very little gain when controlling/reducing the amount of energy going into the boiler would acheive the same result.

            Often tube and shell dephlegs "choke" when overdriven this can casue surgig as the vapor blows through the liquid, likewise if any of the product condensors or parrot form a liquid trap, surging will ocurr as the still "breathes".

             

            Another issue known to cause surging or resonance in a unit is sudden cooling of a large amount of vapor when it first enters the condensor, this creates a temporary partial vacuum that sucks in air from the outside, followed by pressure from the boiler driving vapor out. The frequency is set by the size of the still, length and diamater of piping, condesnors etc, energy balance etc, and can be fast huffing or puffing in a small still, or slow surging in a larger still/longer piping system. Seems to be common practice to have the coldest cooling water entering condensors at the bottom/product exit, in a stacked system that may be your well water for the bottom one, and the recirculated supply for the first.

             

            If the thumper is flooding, that could cause surging too. This being the second time running the still, depending on previous experience, a "gentle" start-up regime and practise runs would be the "go" to get the feel for energy balance and control. In the early stages i'ts best to use only the amount of energy/steam to produce gentle simmering and plenty of time to get used to various controls at minumum settings, this helps minimse "overshoot" and having to "tune" several things at once; take-off rates can be checked, proof and distillation times stabilised and measured etc., and a feel for the "cuts" established.

             

            If things seem sweet, and under control and a desire is then for faster batches/higher take off, the energy in can be incremented up, dephleg adjusted until the sweet spot is found for most efficient or timely use without surging, spitting, or excessive use of cooling water in the phleg to compensate for an over-driven boiler. Insulating the boiler is going to save some energy too.

             

            Just a few ideas/comments, hope they may be useful. I know others could chime in too. The usual disclaimer applies. Good luck!


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