Another CO2 reactor thread

[esarkipato]

Well, I'm battling the usual algae and I'm pretty sure it's due to low co2. Currently, I have a ceramic diffuser running into my XP3, which then dissolves some bubbles but also spits some back out the spraybar. I suspect that i don't have enough dissolved co2. So I've got 3 goals/constraints in this project:

-Need more dissolved co2
-don't want any extra pumps (must use either passive or XP3)
-Don't trust my DIY Plumbing skill to doing it "inline", or out of tank --must be in-tank.
-as always, keep the cost down

My "inspiration" is a setup I had in the past, notice in the back right corner the reactor:



This time, I'd like to introduce some new features. they are

1. create a "vortex", a swirling effect which increases turbulence/dissolution
2. Have a plan for the gas buildup which inevitably occurs.
3. Better dispersion at the end of the reactor into the rest of hte tank.

HENCE....



A couple of notes:
-the XP3 return line will enter the reactor at an angle and off-center. The exact placement/angle will determine the "vortex" attributes I would think. Any suggestions? I was thinking going in at roughly 45 degrees.
-Drawing 2 shows the general direction of the swirling flow, and the off-center placement of the outflow tube.
-Drawing 3 shows the "burper" which is of course the techical term. I'm guessing that any gas building in the top of the reactor will be sucked through the tubing and back into the high velocity stream. Is this correct? Or will the water just flow down through the co2 tubing? I could use a check valve here......
-Drawing 4 (un-numbered) shows the cap and distribution on the end/bottom of the reactor.

I know, this looks primitive now and it definitely will once it's in-tank. My hope is just to get some practice at "plumbing" and maybe eventually mod this think to make it inline, out-of-tank!

It's my hope to construct this with MOSTLY things I already have, which is nice.

Please give me some feedback on the design/functionality of the unit! (criticisms of by MSpaint skills are begrudgingly accepted)

[plantbrain]

a clouple of things will help, fig 3 is good and will help, you should have the CO2 venturi recirculating level set at about 3" down in the reactor tube.

You need some room for the microbubbles to coalesce and get simple diffusion via the layer.

Adding a small diffuser disc might also help, then blast that around the tank without the Reactor there using the XP3 spray bar.

If you want the reactor still, I think you need to disperse the outflow from it better, add another reactor tube on the other side, or place a small poqwerhead near the bottom of the out flow the blast the CO2 rich away into other parts of the tank etc.

These might not be acceptable ideas for your goals.
But the disc idea would solve them also.

I tend to use disc and blast the gas around by placing the spray bar vertically in the corner of the tank and place the disc down low near this outflow.

I direct the mist to be blasted around the back wall of the tank which is the longest straight area and where you generally don't see the mist and where most of the plants are anyway.

This hides things well and gets the most of the gas.

Regards,
Tom Barr

[esarkipato]

Thanks for the reply, Tom.

a clouple of things will help, fig 3 is good and will help, you should have the CO2 venturi recirculating level set at about 3" down in the reactor tube.

This would allow 3" of air to build up in the top of the reactor, if I understand you correctly. This is desireable?

You need some room for the microbubbles to coalesce and get simple diffusion via the layer.

I'm not catching you here. Is this related to the previous 3" down advice? Clarification is appreciated .

Adding a small diffuser disc might also help, then blast that around the tank without the Reactor there using the XP3 spray bar.

This doesn't really help. Currently I have tons of small bubbles flying around the tank from the XP3 spraybar, and still suspect low co2-related algae! My goal is in-tank diffusion (no powerheads) with good dispersion, not micro-bubbles.

Your thoughts on dispersion of the co2-rich water.....are well placed. co2-enriched water is no good if it doesn't get to the plants! I just thought of another solution: Hook the spraybar to the BOTTOM of the reactor, and run that along the BOTTOM of hte back wall. I could then shoot it along the gravel and up into nearly 100% of the plants! Hmmmmmmm.....somehting like this?

[Rex Grigg]

Might want to take some fluid dynamics classes at the local community college. Your water is not going to swirl though the tube.

[plantbrain]

At this point, you have a CO2 in line reactor that's best placed outside the tank.

That's the only difference this design is, just pull it out of the tank and place on the back and keep that spray bar return pattern.

The reactor in lines are easy to make, see Rex's guide there.
Cost: 10$.

I can detail out a decent venturi loop for the in line reactors also, this will remove some of the gas build up that occurs during the day and allow the reactor to better dissolve CO2.

Regards,
Tom Barr

[Rex Grigg]

I get no gas buildup in my DIY reactors. If I did I would hear it. And the cost is more than $10. PVC prices are a bit high right now.

[esarkipato]

Uh-oh. I don't want to start "reactor war III". Let me try to clarify some of this...

Originally Posted by Rex Grigg

Might want to take some fluid dynamics classes at the local community college. Your water is not going to swirl though the tube.

That is dissapointing. I was reading this thread by jay1st and thought I would be able to create the same type of vortex with the above setup. I admit I really don't have a fluid dynamics degree, just an imagination . Rex, would you agree that Jay1st's setup above would create the swirling/vortex effect?

I know I could easily "contract" out the reactor....but what fun is that? In the words of Billy Madison, "I'm here to learn everybody.....not to makeout with you!".

I guess the above linked thread intrigued me with the creation of the vortex. If that's not possible without the introduction of another pump...I just might head back to the drawing board...

[Rex Grigg]

Nope. Jay's reactor doesn't swirl much at all. There is some extra turbulence at the top. That's about it.

[esarkipato]

Well damn. I very well might be barking up the wrong tree. I suppose I should check my assumptions....

Does/would the swirling vortex reactor be more efficient than a "conventional" one?

[Rex Grigg]

If you could get the water to swirl it would be cause it would result in a longer contact time with the water. But I have never had a problem with my "normal" reactors. But the very nature of fluid flow means that it will take the path of least resistance. The only way you will get fluid to swirl in a pipe is to deflectors in the pipe.

The swirling thing works quite well in very wide container with very high capacity pumps. In fact it's how they separate wort from the solids in a brewery. But the pumps in that case are huge. Imagine 8000 gallons of liquid in a brewing tun (about 20 feet across) swirling around the outside edge so fast that it's almost leaving a dry spot in the middle.

This whole thing reminds me of a common myth among cigar smokers. That if you cut the foot of a pyramid cigar at an angle it will direct the smoke at your upper palette.

That doesn't work either as the smoke is going to take the path of least resistance towards the vacuum.

[Hoppy]

Several years ago I made a reactor from clear acrylic. It was a 4" diameter pipe, about 10 inches long, closed on both ends, with tangential inlet and outlet for the return flow from my canister filter. The CO2 was bubbled up from the bottom and the water flow was in the same direction. (Yes, I know that isn't the way to do it, but I didn't know that then.) I did have a water vortex in the reactor tube, with the CO2 bubbles staying in the center and the surplus collecting at the top. There is such a huge difference in density between water and gas, that it takes very little swirl to hold the gas in the middle.

The Barr Internal Venturi reactor I use now also swirls the water, holding the CO2 in the middle, but the CO2 bubbles get recycled thru the venturi loop into mist. That Barr reactor doesn't even have tangential inlet from the powerhead. It just directs the water towards the side. Apparently there is less flow restriction if the water swirls than if it just tumbles every which way.

[esarkipato]

Just wanted to follow up a little more. I appreciate you guys' patience with my noobish theories!

I have decided that, for the sake of my plant's health and my own sanity, I will deviate from my original goal and utilize a powerhead for this project

The design is basically copied from the Barr Venturi I suppose:



My main concern is the 90 degree bend in the powerhead outlet. As I plan it, this will happen at the very, very top of the reactor tube (old gravel-vac syphon). Should I try to move this down the tube at all, or will this be effective enough?

I looked around, and actually have all the necessary components to create one of these reactors, or something like it. The powerhead and such things are drying out right now....hopefully the pump is powerful enough. The plastic tube I have is roughly 12" long, which might be too much I guess. But, I can always cut it down.

Just a seperate, but related observation, which has probably been pointed out before on this forum:

I'm assuming the rate of co2 gas dissolution will increase as the ratio of Surface Area to Volume increases. Simply, more area for the gas to escape. using the equations
Surface area = 4*pi*r^2 and
Volume = 4/3*pi*r^3
it becomes evident that this ratio increases with bubble diameter. Therefore, the rate of co2 dissolution is faster with bigger bubbles.

This fact considered, I am hoping that this reactor will be the best of both worlds. It should increase dissolved co2, as well as create microbubbles. Thoughts/comments are welcome!

[jay1st]

Nope. Jay's reactor doesn't swirl much at all. There is some extra turbulence at the top. That's about it.

Open your eyes when watching the vids man.