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Thread: Re-circulation Explained

  1. #11
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    wmick, to address your questions. My pump moves just over 4 gpm. I have no measure of how much is recirculating, it utilizes a small needle valve just ahead of the main needle valve that controls the pressure of the system and I have 2- 4x40 membranes in series. My pump is belt drive off a 2HP motor.
    I only get my flow numbers from observing the flow meters.
    On my RO with no recirculation I get barely over 4 gpm, adding the concentrate and permeate flows. With 2% sap I can adjust those ratios from well below 1 gpm of concentrate at about 285 PSI (about .6 gpm) up to about 1.8 gpm at between 240- 250 PSI, in each case the balance of just over 4 gpm is in permeate.
    I run most of the time, when inputting about 2% sap at 270-275 PSI and get about 1.1-1.2 gpm of concentrate and 2.8-2.9 gpm permeate. That is with my recirculation needle valve open about 1/2-2/3 turn (I have no idea how much is recirculating when I do this.
    Just an observation, when on wash cycle, as the cycle is nearly done I get readings of about 2.6-2.8 GPM on both flow meters and at that the pressure is about 60-70 psi. All during my wash cycles I try to balance both flow meters, Early in the cycle it is not achieved, but within a couple of minutes I can balance the meters. From then on I adjust the pressure to maintain equal flows, as the membranes get cleaner the pressure needs to be set slightly lower and the totals of the 2 flow meters slowly climb until I get to between the 2.6-2.8 GPM on each.
    Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
    Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
    Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
    After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.

  2. #12
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    Marysville, Ohio
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    Your explanation looks pretty accurate too me. i would add one more benefit of recirculation. Recirculation allows the sugar concentration to be more uniform across the entire membrane and therefore the permeation rate and fouling rates are more uniform. For example if you are running once through and the sugar is 2% on the inlet it end, it's about 4% on the outlet with 50% water removal. The pressure is roughly the same on the inlet and outlet ends. Because the sugar content is half as high on the inlet end, the osmotic pressure is low and the permeation rate and fouling rates are very high. The inlet end starts to foul very quickly and becomes completely plugged over a short period of time. The effective area of the membrane becomes smaller and smaller as it continues to run. I run less than 15% recovery with pretty high recirculation rates. I can run my membrane for at least 5 all day runs before it requires soap washing. This year I never had to soap wash during the season at all. I only did permeate flushes at the end of every run. The second benefit to minimal soap washing is limiting damage to the membrane. Soap washing can slowly degrade it over time.
    Last edited by bowhunter; 05-04-2019 at 10:38 AM.
    Leader 1/2 pint - Kawasaki Mule - Smoky Lake Filter Bottler
    24 GPH RO, 2 1/2 x 40 NF3 (NF270), 140 GPH (Brass with no relief valve ) ProCon pump
    2013 - 44 taps - 16 gallons syrup, 2014 - 109 taps - 26 gallons syrup
    2015 - 71 taps - 13.5 gallons syrup, 2016 - 125 taps - 24.25 gallons syrup
    2017 - 129 taps - 17.5 gallons syrup, 2018 - 128 taps- 18 gallons syrup
    2019 -130 taps - 18.5 gallons syrup, 2020 ~125 taps-19.75 gallons syrup

  3. #13
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    Apr 2016
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    Mapleton Twp, SW Ontario
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    Quote Originally Posted by arcticmaple8 View Post
    Wmick: i read your link to lappiere. Good read. I see it recomends mot concentrating past 70% in beginning and uses 75% as an example in the testing procedure. This is very typical in maple ros. I didnt see anything about 15% recovery.
    Yes - I find it a bit confusing. Hoping someone might clarify.

    Slide #7 says this.
    "According to membrane manufacturers, a membrane must operate with a maximum recovery rate of 15%.
    RECIRCULATION or an increase in the NUMBER of membranes allows increasing the total recovery rate of a system without damaging the membranes."


    Yet - Slide number 8 has a chart showing 75% recovery...

    So - What gives??? Is the chart on slide 8 assuming recirculation? or are they operating at 5X the manufacturers recommendations? or ??

    I sent the question to H20 Innovations.... Hopefully they can clarify.... The other 2 manufacturers that I emailed last week have not yet.
    Last edited by wmick; 05-06-2019 at 07:22 AM.

  4. #14
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    Quote Originally Posted by maple flats View Post
    I run most of the time, when inputting about 2% sap at 270-275 PSI and get about 1.1-1.2 gpm of concentrate and 2.8-2.9 gpm permeate. That is with my recirculation needle valve open about 1/2-2/3 turn (I have no idea how much is recirculating when I do this.
    Just an observation, when on wash cycle, as the cycle is nearly done I get readings of about 2.6-2.8 GPM on both flow meters
    So - your "recovery rate" is maybe not quite as high as you thought...
    If we assume that your wash flow is actually your total pump flow... your total flow is 2.8 + 2.8 = 5.6 gpm
    and your permeate is 2.8 gpm. divided by 2 membranes = 1.4 gpm per membrane with 5.6 gpm total flow. 1.4/5.6= 25% membrane "recovery" rate.

  5. #15
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    Oneida NY
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    when I have my re-circulation needle valve closed, the 2 do not equal 5.6 GPM except near the end of a wash cycle. Thus that math is in error. With that needle valve closed and just the main needle valve open to give me about 275 PSI I get a total flow when I add both of 4.0-4.2 gpm. When I observe the 2.8 and 2.8 the pressure is about 40-50 PSI. Thus, with my Deer Run RO the pressure make a big difference of what total flow I get.
    Back in my insulation background and my farming background with mixing chemicals to create foam insulation and with irrigation as well as spraying pesticides, as the pressure increased the flow decreased, in every case. The pumps do not have a linear performance, it is a decreasing curve.
    For example, on my irrigation pump (a 13 HP centrifical 3" pump) I used to get 43 sprinklers flowing and impacting properly and got over 60 psi at the sprinklers for 60 gph/sprinkler or about 2600 gph. When I was just transfering water, with a 17' rise to refill my pond I got over 10,000 gph at about 30 PSI open discharge. In both cases the throttle was on high. Pump performance is not linear.
    Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
    Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
    Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
    After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.

  6. #16
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    Oneida NY
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    My thought is that you are too hung up trying to calculate flow with a small portion of the data that would be needed.
    Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
    Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
    Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
    After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.

  7. #17
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    Mapleton Twp, SW Ontario
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    Quote Originally Posted by maple flats View Post
    My thought is that you are too hung up trying to calculate flow with a small portion of the data that would be needed.
    You are quite right... Just trying to wrap my head around all the different variations... I do understand that pumps have a psi/flow curve at a given rpm. What type of high pressure pump does your Deer Run use? I'm a little surprised at your "curve". Vane pumps seem to be common , from what I've read on here... and procon's series 4 curve only varies by about 0.2 gpm between 50psi and 250psi ... Are other pump styles used too?
    Thanks

  8. #18
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    Vane pumps and piston pump are positive displacement. They will give the same relstive flow at different pressure. More pres requires more hp. Multistage or other centrifugal pumps have pump curves showing flow vs psi

  9. #19
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    Quote Originally Posted by arcticmaple8 View Post
    Vane pumps and piston pump are positive displacement. They will give the same relative flow at different pressure. More pres requires more hp. Multistage or other centrifugal pumps have pump curves showing flow vs psi
    Yep - agreed - This is why I'm surprised at Maple Flats' flow difference at different pressures.... I'm thinking it must be a different type of pump??.

  10. #20
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    Yes. Different type pumps have very different curves or pressure/flow relationships. The ProCons are considered positive displacement and show very little difference in flow vs pressure. A centrifugal pump on the other hand is very responsive to back pressure.

    To your recovery question: Without recirculation the recovery is very easy to calculate for a single membrane system. It is the permeate flow divided by the total sap flow to the membrane expressed as a %. With recirculation the membrane recovery is not as easy to understand. Lets suppose you have an single membrane RO system with recirculation that is feeding 100 gph of fresh sap into the system, and it is removing 75 gph of permeate. The system recovery is 75%, however the membrane recovery is 15% because the flow through the membrane including recirculating concentrate and fresh sap is 500 gph. So you are recirculating 400 gph of concentrate and adding 100 gph of fresh sap. Hope this helps.
    Leader 1/2 pint - Kawasaki Mule - Smoky Lake Filter Bottler
    24 GPH RO, 2 1/2 x 40 NF3 (NF270), 140 GPH (Brass with no relief valve ) ProCon pump
    2013 - 44 taps - 16 gallons syrup, 2014 - 109 taps - 26 gallons syrup
    2015 - 71 taps - 13.5 gallons syrup, 2016 - 125 taps - 24.25 gallons syrup
    2017 - 129 taps - 17.5 gallons syrup, 2018 - 128 taps- 18 gallons syrup
    2019 -130 taps - 18.5 gallons syrup, 2020 ~125 taps-19.75 gallons syrup

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