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Co2 ?

Discussion in 'CO2 Enrichment' started by trong, Mar 11, 2009.

  1. trong

    trong Lifetime Charter Member
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    is the air in the co2 reactor at the end of the day cycle (after the co2 has been shut off) just air, or is it still co2? Running many bubbles per second all day leads to some air at top of the reactor at the end of the day. I'm pretty sure its 95% air but does anyone now for sure? My reactor has a out gas button to purge pressure at the top of it, and i usually expel the gas cause i assume it's just air. Am I wrong?
     
  2. ccLansman

    ccLansman Guru Class Expert

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    good q? but why do you assume air? if you pump co2 in all day how would air creep into the mix?
     
  3. abcemorse

    abcemorse Prolific Poster

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    I would believe it to be CO2, I think that's the whole idea behind the venturi reactor, to capture the trapped CO2 and return it through the reactor.
     
  4. rafel

    rafel Junior Poster

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    Would we be able to damage our reactors if we DON'T expel the trapped CO2 (or air) ?
     
  5. ixxe

    ixxe Junior Poster

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    I beleave its both co2 and o2 i run co2 24/7 and i only get gas buildup in daytime when the plants are producing o2
     
  6. shoggoth43

    shoggoth43 Lifetime Charter Member
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    If you leave the "air" bubble in the reactor overnight, is it smaller in the morning? Most CO2 sources aren't going to give you 100% CO2. There's always going to be SOME levels of other gases in your CO2 tank. This amount is theoretically the difference between "welding" vs. the "medical" grade CO2. In most cases the gases are bits like nitrogen, argon, etc. and can just be purged.

    The idea behind Tom's venturi design is that you generally shouldn't have to purge it as it will eventually diffuse the bubble that's left over by morning ( hopefully ) so you don't have to worry about it. You probably won't damage anything if it builds up, but your efficiency will likely drop significantly over time. It is also possible to airlock your pump and plumbing depending on how you've implemented your setup as has happened to a few people here. This seems to be related to the flow of the pump. Less powerful pumps seem more prone to this if you feed the venturi back into the impeller.

    -
    S
     
  7. trong

    trong Lifetime Charter Member
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    i'm not using toms venturi. mine is a japanese reactor called a J mixer by Jaqno. it does use venturi to break down co2 into the water. my thoughts are that co2is not that stable in this environment and is broken down, or mixed with the water and what is left? is...... air? i'm not a scientist, just a regular guy with an average IQ. thats the reason for my question. i'm hoping someone will know, if whats left is air or how much of whats left is air?
     
  8. Tom Barr

    Tom Barr Founder
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    At the present time, no one really knows, some speculation.

    I can add a sealed O2 probe to measure, or a flow through gas hypo to withdraw gas and send it through an IR analyzer for CO2 etc.

    You can also add air and time the bubble till it's gone etc, or N2 gas etc.
    It might be just total dissolved gases coming out of a solution, not any one in paricular.
    I think the last one is much more eplanatory in the results and in what we know about venturi action on a sealed water/gas interface. Say the water has 30ppm of CO2, 7ppm of O2, 400ppm of N2 etc.......this just equilibrtaed in gas form in there, and some of the gas just builds up as it comes out of solution. Same deal in filters.

    CO2 in and of itself alone would dissolve pretty fast, but mixture with much less % likely would not.
    I'm not so sure that the 30ppm that came out of solution into the gas phase would rapidly dissolve back, vs the 10000000 ppm.


    Regards,
    Tom Barr
     
  9. shoggoth43

    shoggoth43 Lifetime Charter Member
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    What's left in your system will depend on the source of your CO2. For example, if you used a yeast reactor, you're going to have a bottle full of regular air which will need to empty into the reactor at some point. The air won't dissolve into the water as easily.

    If you use pressurized CO2, you still may have air in the line ( at some point it should clear ), plus you'll have a couple of trace gases in your cylinder. If you drive too much CO2 during the day, you'll end up with a pocket of CO2 in your reactor which may eventually dissolve overnight. That will depend on how large a pocket, surface ripple and so on.

    Most likely what you've got at the end of the day is a mix of CO2 and trace gases. If you leave it overnight, do you have as large a bubble or is it significantly reduced? If it's much smaller, it's most likely just excess CO2 and anything left at that point is trace gases. You might just purge it in the morning instead so as to put most of the CO2 into the water.
     
  10. ccLansman

    ccLansman Guru Class Expert

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    I don’t usually get a pocket unless the bps is > 12 or so.. and it’s dissolved by morning. I guess a good question would be, what are you using to power the reactor? May be it’s not enough, I have mine hooked to my eheim 2026 and it tares through the gas very quickly.
     
  11. trong

    trong Lifetime Charter Member
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    mine is also hooked up to a 2026 ehiem. I'll pay more attention to size of trapped air in the morning as opposed to night time. But at night time plants take in oxygen and expel C02, How will this change size of said pocket? I think i get it?
    My reactor is about 5 inches wide and is about10 inches tall. the gas pocket is almost 3/8" at center of venturi swirl. the reactor has 3 pipes in it 1 for co2 an inlet which is a vertical spray bar and an outlet that is from the bottom. Its very efficient. I get my drop checker w/appropiate solutions green yellow with about 2+bps. It's on a high light 80 gal heavy planted tank.
    I'll start purging gas in the am.
    thanks everyone who responded. i really appreciate the input, and am glad i asked.
     
  12. Philosophos

    Philosophos Lifetime Charter Member
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    How about rigging a small drop checker in there as a first test? If it's pure yellow or blue before the CO2 kicks on, you'd at least know what most of it is between the two.

    -Philosophos
     
  13. shoggoth43

    shoggoth43 Lifetime Charter Member
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    The pocket should still dissolve somewhat overnight. As long as you have some surface movement and no scum/film on the surface you will still have gas exchange. If you're running with a fairly high bubble rate during the day then you probably have plenty of surface movement to outgas any CO2 from the plants and fish at night. As long as that's the case, the CO2 bubble in the reactor should shrink overnight as well. If it's reduced dramatically in the morning, then maybe you'll just need to purge every couple of days or so. More flow through the reactor might eliminate even that issue but I can't guess on that as I'm using diffusers at the moment.

    -
    S
     
  14. ccLansman

    ccLansman Guru Class Expert

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    lol... if you can show me a way to do this without tearing apart the reactor ill try it :p
     
  15. ccLansman

    ccLansman Guru Class Expert

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    I guess im the only one, i run a 60gal planted and have to crank the sucker up to 9bps+ to get the plants going. I would not just go by what the drop checker is showing you. Are your plants pearling and doing well at only 2bps?

    5 inches wide,... wow!, im guessing you did not use standard pvc? Also im still unsure as to why you would get a pocket especially at only 2bps, i have mine 9+ and i don’t get a pocket. I don’t have any venturi, only the 2026 flowing in top and outlet on the bottom. Your venturi may be causing the excess gas at the end of the day, is it positioned well under the surface of the water? Can you click any pics so we can get a better idea of the situation?
     
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