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Thread: Turbidity issues

  1. #1
    Join Date
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    Turbidity issues

    Hi all,

    We've been experiencing some turbidity mysteries during lautering. Somewhere during the process, turbidity seems to increase greatly and I don't understand why.

    The problem is mostly when we brew our low gravity beers (around 11P) and most apparent when brewing our beer that has a malt bill made up of 30% corn flakes. In our 40hL brewing system, we always see a big drop in clarity after about 20hL of wort has been pumped to the brew kettle and it usually results in having to mix up the grain bed, start vorlauf again, which takes about 45 minutes before a proper clarity is reached again.

    We have a lauter tun and software designed for batch sparging (don't ask me why). The corn flake beer wort is mashed in in a 1:3 ratio with 19,5 hL water (so we use 650kg of malt/corn). First sparge is after 11hL of lautering. By that time there's still a bit of wort on top of the bed. Lautering keeps going after each sparge (5 sparges in total, each half the volume of the one before. I'm not sure about the theory behind this, please enlighten me if you do know), we usually don't do or need to mix and recirculate, the idea behind it that we don't mix the wort as much as 'replace' it from the top down with lesser strength wort. We rake about 5cm above the false bottom at a very slow speed during the process.

    It seems to have something to do with the thickness of the bed, since our higher gravity beers (usually between 15 and 18P), don't exhibit these problems to this extent (in all fairness, there usually does seems to be a smaller drop in clarity around the 30hL mark).

    Some extra or maybe redundant info: the corn flake wort get's a 90 minutes step mash, including 20 minute beta-glucanase rest at 45 degrees Celsius. Lauter tun diameter is 3m. The top of the filterbed of the corn flake wort looks quite solid and cake-y.

    One theory so far: finer particles that settles on top of the filter bed migrate down at some point and find their way through the false bottom. But why?

    Pardon my metric. And thanks in advance.

  2. #2
    Join Date
    Jan 2003
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    Can't tell you why anyone does batch sparging...

    I've never found a reason to go there. But, it is common for bits to get through the lauter bed. First step in mitigation is vorlauf. Apparently, you've got this covered. As you lauter, the malt "cookie" shrinks. Especially using adjuncts like corn flakes. They nearly disappear during mashing/sparging. To counter the tendency of the cookie to shrink and leave massive gaps around the perimeter and giant cracks in the cookie, I paddle the top half of the mash. Don't need to disturb the settled bed below, and this helps greatly. If done too much and too deep, then the draff migrates into the settled bed and your differential pressure across the bed rises. But gentle stirring and redistribution of the top half of bed seems to work well with us. Especially with rice adjuncts. But your system apparently has rakes. If they are designed right, they will redistribute and lift the bed to counter the bed shrinking. Can you adjust the rake speed? Can you quit the batch sparge? Seems as if raising/lowering the liquid height on the bed will tend to compress the bed too.
    Phillip Kelm--Palau Brewing Company Manager--

  3. #3
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    Mar 2018
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    Thanks for the reply Phillip.

    Quote Originally Posted by gitchegumee View Post
    If they are designed right, they will redistribute and lift the bed to counter the bed shrinking. Can you adjust the rake speed? Can you quit the batch sparge? Seems as if raising/lowering the liquid height on the bed will tend to compress the bed too.
    We do seem to get bed shrinkage occasionally, proven by the cookie getting off the side of the lauter tun. We can adjust rake speed yes. Quitting batch sparging not so much. We can adjust the volumes we sparge each time, thereby 'modelling' fly sparging a bit more, but we haven't found the sweet spot yet. The bed getting compressed because of too much liquid on top sounds plausible. I am actually brewing the mentioned beer now. I will redistribute the sparge water over the 5 sparges equally, instead of 40% at the first sparge. See if that helps, together with raking the top half of the bed. I must add, the bed seems to be very thin since the flakes don't add that much solids to it.

  4. #4
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    Some other considerations.

    If you let the sparge water drop to the level of grain bed, then the bed will begin to compress as the liquid level drops and the grain ceases to float. This done once is enough to impede liquid flow through the bed. It's possible to accelerate the sparge as the process proceeds. Higher temperature sparge and grain temperature along with lower sugar concentrations make the viscosity drop and flow rates increase. So normally I start the sparge slow and increase the sparge rate as the kettle fills. I try to keep the lauter process to 120 minutes.
    Phillip Kelm--Palau Brewing Company Manager--

  5. #5
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    Quote Originally Posted by gitchegumee View Post
    If you let the sparge water drop to the level of grain bed, then the bed will begin to compress as the liquid level drops and the grain ceases to float. This done once is enough to impede liquid flow through the bed. It's possible to accelerate the sparge as the process proceeds. Higher temperature sparge and grain temperature along with lower sugar concentrations make the viscosity drop and flow rates increase. So normally I start the sparge slow and increase the sparge rate as the kettle fills. I try to keep the lauter process to 120 minutes.
    Thank you once more for your input.

    We use the same methods that you mentioned. The change that I made to the sparging moments and volumes two weeks back (smaller but equal volumes in six sparge moments) and raking with the arms higher up did a good job reducing turbidity. It did seem to come at the cost of reduced yield (about 0.3P). Might be a sacrifice I've to make.

  6. #6
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    Loss of efficiency?

    That should not happen. I see no reason why "batch sparging" would be any more efficient. I do see reasons for it to be less efficient. I know of no large breweries who exercise batch sparging. And they have incredible efficiencies. My understanding of typical, traditional, continuous sparge is that gentle rain on top of 3cm of water covering the grain cookie will gently and slowly run through the grain, picking up sugars, gaining gravity, and leaving the false bottom without much, if any stratification. I see it as a hydronamically balanced system that carefully extracts solids with a slow sparge migration through the bed. The only thing I can see a batch sparge do is disturb the bed by repeatedly floating and sinking it. Increasing the odds of turbidity. I'd like to hear arguments for batch sparging. I must be missing something.
    Phillip Kelm--Palau Brewing Company Manager--

  7. #7
    Join Date
    Nov 2016
    Location
    Port Lincoln, South Australia
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    Back let?

    I had the same issue with turbidity increasing around half way through run off.
    Our plates don't create a perfect seal against each other, nor the LT so I thought flour was escaping around these gaps
    I've started employing a back/under let as soon as the mash is transferred to LT. - running the rakes during the process.
    My theory on this is that it gives the smaller floury particles opportunity to travel higher up through the bed to find a home.
    Coming from a Braumeister background (where the whole mash is performed by the liquid being recirced bottom to top) and seeing how perfectly clear the wort was from this proccess, I thought it was worth a short blast.

    - settle - vorlauf - run off - no issues since.

    I'm back letting roughly 40-50L for a 12hL batch

  8. #8
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    Hi ya, thanks for the replies.

    I'd like to hear arguments for batch sparging. I must be missing something.
    Phillip, you won't be hearing any arguments from me in favor of batch sparging, I'm sure to lobby for a fly sparging system once we grow bigger again. Other than that I 100% agree with your view on batch sparging vs. fly.

    I've started employing a back/under let as soon as the mash is transferred to LT. - running the rakes during the process.
    My theory on this is that it gives the smaller floury particles opportunity to travel higher up through the bed to find a home.
    Coming from a Braumeister background (where the whole mash is performed by the liquid being recirced bottom to top) and seeing how perfectly clear the wort was from this proccess, I thought it was worth a short blast.

    - settle - vorlauf - run off - no issues since.
    Dan, thanks for the tip! Will try it tomorrow.

  9. #9
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    Update?

    Hi Allard

    Did you have any success with your turbidity issue?

  10. #10
    Join Date
    Mar 2018
    Location
    Amsterdam, The Netherlands
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    Hi Dan,

    I've had mixed results with the method you suggested. The best remedy for our problem was to go back to vorlauf, until the wort was clear enough again. Bit more time consuming, but effective.

    We're finished with brewing this particular beer for this year, so I'll come back to this topic asking for help next year again .

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