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Are CO2 reactors 'scalable'?

Discussion in 'CO2 Enrichment' started by scottward, Sep 8, 2010.

  1. scottward

    scottward Guru Class Expert

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    Just wondering, are CO2 reactors typically scalable?

    For example, if I'm finding that my AM1000 is being 'maxed out' in my tank, rather than employing a second AM1000, could I DIY a new AM1000 that is twice the diameter and height of the existing one, double the water rate and therefore increase the CO2 input rate?

    Sorry if this is a dumb question...

    I'm just trying to see if rather than buying another AM1000 I could do something else, maybe DIY a bigger one...but I think if I did this I would also have to up the flow rate or, as a result of a larger reactor size the water flow rate would be reduced such that larger bubbles collect at the top and do not dissolve effectively.

    Scott.
     
  2. nipat

    nipat Guru Class Expert

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    This is interesting question. Since I'm thinking about making a couple of shorter reactors
    for short cabinet. I think the height doesn't matter as much as diameter.

    To make a better performance reactor, I think it has to be bigger with stronger flow rate.
     
  3. csmith

    csmith Guest

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    I personally think length matters more than diameter. More length means more distance for the CO2 bubbles to travel upward against the flow of the water. The actual reaction chamber on the AM1000 is 10.5" long. Most of the DIY versions preach 12-15". I'd have to assume there'd be reason for the longer distance on the DIY tubes.

    That's not to say short reactors won't work. I have a 15" tube on both a 55 gallon and a 20 gallon and it's severe overkill for the smaller tank. I honestly think I could have halfed the size as it's only 1 bubble every two seconds.
     
  4. scottward

    scottward Guru Class Expert

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    Would just increasing the length make much of a difference? I was thinking that if increasing the water flow was also required, an increase in diameter would be needed to reduce the water velocity?
     
  5. shoggoth43

    shoggoth43 Lifetime Charter Member
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    Try taking a look at some of the skimmers the reefers use. They're doing a lot of things you want to do but for different reasons. The whole idea for them is surface area and dwell time. This is what we're after as well when trying to dissolve CO2. We're not looking to pull anything out in the process but some of the designs they use might be of use. i.e. tangential flow and counter current.

    -
    S
     
  6. Biollante

    Biollante Lifetime Charter Member
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    Yes To CO2 Reactor Scalability

    Hi Scott,

    Kind of yes to all the above. :gw

    What Shoggoth43 (*) and C. Smith (**) say is correct. I have found that a 10 foot by 4 inch (3 meter by 10 cm) PVC pipe with a glass diffuser we induce circular motion (tangential flow) with three 100 mm (4 inch) mixing vanes (wire paint mixing thingies) wielded to a shaft and turned at 250-260-revolutions/minute, about 3 mile/hour (4.8 km/hour). Not practical but an excellent CO2 reactor. :eek:

    (*) Shoggoth
    [video=youtube;js2sFtmdKgM]http://www.youtube.com/watch?v=js2sFtmdKgM [/video]
    and
    (**) The improbably C. Smith
    [video]http://www.imdb.com/media/rm3191838976/tt0033922 [/video]

    Biollante
     
  7. scottward

    scottward Guru Class Expert

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    Biollante...what are you on???

    I wasn't actually sure what a 'Shoggoth' was, so I googled it. ;-)

    Regarding up-scaling a reactor....
    I'm experimenting with my AM1000 at the moment. With the bleed valve closed eventually I get about 2" of CO2 built up at the top of the reactor during the course of the day. If I wanted to eliminate this, it seems that:

    1. More water needs to go through the reactor. It doesn't matter how I change the width or length of the reactor, nothing is going to get rid of this air bubble other than more water. By changing the width all I'll be doing will be changing the velocity of the water, but not the volume of water passing through.
    2. After increasing the velocity of the water, if bubbles start to pass to frequently out the bottom of the reactor, then I need to either increase the diameter to slow down the velocity of the water OR increase the length to provide longer travel time for the bubble to hopefully dissolve.

    Does this sound about right?
     
  8. scottward

    scottward Guru Class Expert

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    1. Is there a build up of CO2 at the top of the reactor?
    Yes - goto 2.
    No - all good; finished.
    2. Increase the flow of water through the reactor
    3. Is there CO2 escaping through the outlet of the reactor?
    Yes - Increase the length of the reactor until bubbles are no longer escaping. Goto 1.
    No - Goto 1.
     
  9. pat w

    pat w Member

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    The higher flow volume would serve to maintain a fresher supply of water with a realitivly lower concentration of CO2, thereby promoting a higher exchange rate. Reducing the size of the bubbles would help as well by increasing the effective surface area but, you would then be restricted by the velocity limit that would keep the smaller bubbles in the reactor. If you want the absolute best performance, I guess a system that recirculates the finly chopped bubbles within the reactor while maintaining a high flow volume through it, to and from the tank. .... hmmm

    Pat
     
  10. nipat

    nipat Guru Class Expert

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    I don't believe increase the modest length will prevent the bubble escaping.
    If you want to solve this with length, it must be quite long. Have you noticed
    how fast fine bubbles move? So increasing the width (with more water in&out of
    the reactor) is what I believe.
     
    #10 nipat, Sep 17, 2010
    Last edited by a moderator: Sep 17, 2010
  11. shoggoth43

    shoggoth43 Lifetime Charter Member
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    I think doing the repurposed calcium reactor method would work fairly well.

    And for Biollante's benefit... :p

    Bob The Angry Flower

    http://www.angryflower.com/biolla.gif

    PS- I'm not implying anything here, Bob is just a hilarious cartoon at times...

    -
    S
     
    #11 shoggoth43, Sep 17, 2010
    Last edited by a moderator: Sep 17, 2010
  12. scottward

    scottward Guru Class Expert

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    Ok. Thanks. I understand what you're saying there.
     
  13. scottward

    scottward Guru Class Expert

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    I was wondering about this, whether it would be better to make the reactor longer, or, to increase it's diameter. I'm more swayed towards increasing diameter now, such that as the water flow is increased, the velocity is controlled via the diameter. Much more fresh water entering (as Pat was saying). Only the finest bubbles should ever make it out of the reactor, the rest of the bubbles should remain in there, ideally with the average sized bubble 'static' i.e. not moving up or down in the reactor and only slowly starting to move downwards as it's size is reduced. Not that you could actually sit there and watch a single bubble though, of course... ;-)

    So, I think, in terms of scalability, up the water flow, keep the velocity in the reactor the same = increase diameter.
     
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