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Crossflow condenser design.

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  • harisaki2004
    Hello group, I have built, a couple of years ago, one of Harry s cross-flow condensers. My insulated keg and column is run on LP gas. I estimate about 600W of
    Message 1 of 3 , Jul 31, 2010
      Hello group,
      I have built, a couple of years ago, one of Harry's cross-flow condensers.

      My insulated keg and column is run on LP gas. I estimate about 600W of input heat when refluxing. More heat later on.

      When the system is initially refluxing and run at a low heat input I can smell a small amount of heads escaping from the vent although the top of the condenser is not very hot.
      To solve this issue I have attached a piece of 1/2 inch hose x 100mm and some copper pipe to vent any fumes away.

      The condenser has one top vent as per Harry's initial design. The height of the vent is 40mm. I saw a note recommending a vent at each end.

      Once I have collect the heads I can turn the gas up and I do not loose spirit. It just seems to be the heads!

      What are other people using and does any one else have the same symptoms?

      regards

      Hari.
    • Harry
      ... Hari, Full marks for diligent observation! What you are observing is non-condensable gases venting to atmosphere. In any fermentation there is always
      Message 2 of 3 , Jul 31, 2010
        --- In Distillers@yahoogroups.com, "harisaki2004" <ledaswan@...> wrote:
        >
        > Hello group,
        > I have built, a couple of years ago, one of Harry's cross-flow condensers.
        >
        > My insulated keg and column is run on LP gas. I estimate about 600W of input heat when refluxing. More heat later on.
        >
        > When the system is initially refluxing and run at a low heat input I can smell a small amount of heads escaping from the vent although the top of the condenser is not very hot.
        > To solve this issue I have attached a piece of 1/2 inch hose x 100mm and some copper pipe to vent any fumes away.
        >
        > The condenser has one top vent as per Harry's initial design. The height of the vent is 40mm. I saw a note recommending a vent at each end.
        >
        > Once I have collect the heads I can turn the gas up and I do not loose spirit. It just seems to be the heads!
        >
        > What are other people using and does any one else have the same symptoms?
        >
        > regards
        >
        > Hari.
        >

        Hari,

        Full marks for diligent observation!

        What you are observing is non-condensable gases venting to atmosphere.
        In any fermentation there is always non-condensable gases dissolved in the liquid. CO2 is the main one (the bubbles you see in a ferment). Air can also be introduced in some commercial agitation processes. Air is 78% nitrogen and 21% oxygen plus other trace gases eg argon & CO2. All are non-condensable therefore must be vented.

        There is also a tiny amount of ethanol vapors expelled with the non-condensables. In commercial operations this is recovered via trapping (through water), or eliminated altogether via a dedicated final non-refluxing column. In our hobby setups it is such an infinitesimal amount to not be an issue.

        However, if you really want to try trapping this tiny amount of ethanol (roughly 1/2 a teaspoon in a 20 litre run), then attach a tube to the vent and put the other end in a small container of water, similar to a fermentation lock. The gas will bubble through and the ethanol will bind with the water. You can throw this water into your next run, or fermentation, or feints drum. To me it's not worth the bother. There's way more ethanol still remaining in your boiler that you can recycle.

        re 2 vents: All that does is double the escape routes for the non-condensables and also increases the chances of more (but still small amounts) of ethanol being able to exit the system.

        Final word. It is not dangerous in tiny amounts as it evaporates and dissipates to atmosphere, and quickly ceases once the heads concentration phase is finished. However, if you CONTINUE to smell ethanol when you're in the hearts draw phase, then you have a real issue. You're running your still too hard and the condenser cannot handle the load. THIS IS DANGEROUS! Why? Because ethanol is heavier than air and will settle to floor level, where your gas burner is (if you use one. Many do.). I don't need to tell you what comes next, do I?


        Slainte!
        regards Harry
      • landrover_ffr
        Hi Hari, I experienced the same vapour escape issue the first time I ran my x-flow on my VM rig which cause me to panic a bit. But I don t think it s x-flow
        Message 3 of 3 , Aug 1, 2010
          Hi Hari,
          I experienced the same vapour escape issue the first time I ran my x-flow on my VM rig which cause me to panic a bit. But I don't think it's x-flow only issue.
          I added another condenser on the top and that seemed to solver things, but hard to diagnose when the top of the still is 10 feet in the air.
          Anyway now the vapour wafts out the product condenser at the start of take off. I can now smell it and it's defiantly not something I want to keep!
          Harry will be right about it having some ethanol in it. To me it smells like an acetate so vial one good sniff of it could render you unable to make good cuts for a week. For purely interests sake I love to know exactly what it is, but luckily there isn't much of it.
          REgards,
          Sid.
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