Horizontal CO2 reactor - Estimations for a big tank, or small tank

[22802]

Inspired by this great project (thank you @Unexpected 🙏 ) some new insights ...

We may want to reduce the capacity of our horizontal reactor, so that even when something goes wrong (regulator, pH/CO2 controller failure) we are not at risk gassing our lifestock. This is a key benefit of CO2 Spray Bar, but it appears this can easily be replicated on the Horizontal CO2 Reactor.

Raise the end of the reactor a bit, so that CO2 starts purging through the exit. Assume, we target a 1.0 pH drop for the tank, we may then raise the reactor exit to the point where the purging of CO2 will make sure our pH can never drop more than 1.1 - limited by the reactors capacity.
No need to worry anymore about injecting too much CO2, points of failure, as we have now made the reactor inherently safe 🙂

I have tested CO2 Spray Bar in overflow mode , which has the benefit of inherent safety but also that we do not longer depend on the accuracy and stability of our CO2 regulator. We may want to test in the future if same can be achieved with a horizontal generator, slightly adjusted from the horizontal level.

 

[Unexpected]

I was thinking along the same line earlier. I will tinker with it on Tuesday when I have the whole day to monitor it.

 

[Unexpected]

I sent you a PM about this but maybe it's better to discuss things here for others.

I noticed a sudden lack of a pH drop a few days ago so I decided to pull the HR (horizontal reactor) out. I replaced it with 2x10 Inch Cerge reactors running inline with a dedicated pump. What I didn't notice, not until I went through a 10lb CO2 tank in 4 days, was that I had a massive leak in my regulator. So I think this explains why I was getting less drop later.
Here's the interesting thing, the Cerges reactor is only achieving a similar drop. Per our discussion, it appears the off gassing going on in this tank is going to be a challenge.

I want to try again, because I know it works and I want all my equipment hidden. So here's my question. Let me preface, I don't know anything about surface area. Would reducing pipe diameter by half, and doubling the length increase surface area? Or would I need to significantly increase length while using a smaller diameter pipe. Basically, say 2x1 1/2 in parallel. Or maybe 4x1 1/2 pipe, over under and in parallel? Or does it not matter due to the significant off gassing?

 

[22802]

So I think this explains why I was getting less drop later.

Perhaps try first to fix this leak, and retest your original horizontal reactor setup? Your initial results were great, and not even at maximum capacity.

The big unknown to me is the overflow and the overflow chamber at the back of your tank, I was not aware of that (apologize) and did not count that in in any calculations.

Perhaps it is usefull to redo the calculations as in my first post I don't know your tank height, but assume 20 inch for now (we mainly look at surface area, so don't care too much about volume at this stage - volume will start to count for ramping up in the morning, but less so for steady state)




So if we ignore the overflow and overflow chamber, we would estimate that your reactor should balance the outgassing of a 2.4 times higher surface area than tank. The maximum surface area of your reactor we estimate as the area when it is half filled (water flowing in lower half, CO2 pocket above), so this is the length * diameter of the tube. So we estimate that your reactor surface area should be abount 2.4 times bigger than reactor.

With your initial setup (your reactor just about half of your tank length, but compensated with a good 2 inch diameter) your are really hitting this 2.4 target:



So this is why I was quite excited (and not really surprised) that your initial results looked good 🙂

If you want to scale up your reactor in the limited building space in the overflow chamber you may indeed try to combine tubes.

Would reducing pipe diameter by half, and doubling the length increase surface area?

Probably not, because the combined length * diameter of the tubes is not bigger than the original design. As you noticed when you started using a big pump, it will also be more challenging to have a nice flow in a tube with lesser diameter.

Basically, say 2x1 1/2 in parallel.

This could work, because you have more surface area in the 2 reactors combined

Or maybe 4x1 1/2 pipe, over under and in parallel?

Of course even more potential, we then get to what was called 'multi stage' in the first post. This will be a beast, because you get to 2*3.7 = 7.4 times the capacity of 22802 reference, for a tank that has only 2.4 times more surface area. Probably this is too much, and not worth the complications of this build.

 

[Unexpected]

Perhaps it is usefull to redo the calculations as in my first post I don't know your tank height

These are the tank dimensions.

 

[22802]

These are the tank dimensions.

This is not high tech, this is hyper tech - From now I will go for low tech (yes seriously).

I see that the overflow compartment was actually already included in the width, so that only leaves the agitation of the overflow as an additional factor for CO2 outgassing. I would guess that the best step is to test your original design after fixing the leak, and hope that the initial results (with an easy 1 pH drop) would reproduce. If that does not work, then probably go for a single 3 inch tube (preferred in my opinion), or the two 1.5 inch tubes in parallel as you suggest. I am assuming you can't go for the full tank length?

 

[Unexpected]

This is not high tech, this is hyper tech - From now I will go for low tech (yes seriously).

I see that the overflow compartment was actually already included in the width, so that only leaves the agitation of the overflow as an additional factor for CO2 outgassing. I would guess that the best step is to test your original design after fixing the leak, and hope that the initial results (with an easy 1 pH drop) would reproduce. If that does not work, then probably go for a single 3 inch tube (preferred in my opinion), or the two 1.5 inch tubes in parallel as you suggest. I am assuming you can't go for the full tank length?

If I want to keep it all hidden I would need to keep it located in the back. I might give the 1.5 inch in parallel a go. I wonder if it would make less trickle noise with the smaller diameter.

 

[22802]

If I want to keep it all hidden I would need to keep it located in the back. I might give the 1.5 inch in parallel a go. I wonder if it would make less trickle noise with the smaller diameter.

Suggest to use a bypass, so that you have just a gentle flow through the two tubes. The CO2 enriched water will then mix with the water that went through te bypass, and you still have the maximum benefit from the pump flow.

Before starting the new design, you may want to check if the leakage was the issue after the initial good results. My gut feel is that your 2 inch tube, 39 inch, should be sufficient for the 1.0 pH drop that you aim for (even with the outgassing that you have in the overflow).

 

[Unexpected]

Alright, attempt #2.

Using 1 1/2 diameter pipe at about 72 inches total length in over under configuration. I added a simple bypass to this build. I will have only about 3 hours of testing for pH drop.

So far, this is much quieter than the 2 inch diameter pipe. Is it the bypass? Or a smaller resonating chamber?

My question, do I increase flow through the reactor, or increase injection rate for CO2 increase?

It does show a bit above the overflow chamber. After testing, I could swap to black pipe. Either way, if I get a solid and consistent drop I'll be thrilled.

 

[hypnogogia]

@22802 do you have any photos of your reactor. Presumably it’s a lot quieter than other reactors as it doesn’t create a vortex. Also, I assume it needs to be perfectly level to stop gas being pushed out one end.

 

[Unexpected]

Looks like I'm easily able to hit a 5.85 pH. This is at a much lower injection rate than I had to use in my Cerges reactor. My morning, before injection, pH is 6.9. I'm going to try tilting the top reactor so the bottom reactor fills sooner. Maybe this would reduce my current injection rate. I'm still unclear how increasing or decreasing flow through the reactor would change things. I'm open for clarification on this part

 

[22802]

I'm still unclear how increasing or decreasing flow through the reactor would change things. I'm open for clarification on this part

I have not tested this, but I am pretty sure that the absorption of CO2 in the water is nearly independent of the water flow - unless the flow is very low and water nearly stagnant (in that case CO2 absorption is limited by diffusion at the boundary). At any reasonable flow, the CO2 absorption will be mainly dependent on the surface area between CO2 pocket and water. I would therefore use the reactor with a gentle flow (this will reduce any risk for noise), and just as with any other reactor regulate the CO2 injection with the needle valve.

@22802 do you have any photos of your reactor.

My CO2 Spray Bar works so well that I continue with that. Both work from the same principle - a pocket of CO2 gas, with absorption into a gentle water flow below - whereas the CO2 Spray Bar uses the tank water flow and the Horizontal Reactor uses the pump inline water flow.

Presumably it’s a lot quieter than other reactors as it doesn’t create a vortex

Correct, and it is much easier to design, build and operate than a bubble reactor or diffuser. It may take some time, but my bet is that gradually the far majority of reactors and many diffusers will be replaced by horizontal reactors. Just a simple tube or box with water flowing in it, follow the design rules, and job done for a nano tank or a tank the size of a swimming pool if you like.

Also, I assume it needs to be perfectly level to stop gas being pushed out one end.

Correct, and it helps if the tube has a slightly larger diameter and a gentle not too strong water flow.

Note: apologize for late reply, I have been travelling with limited access.

 

[Unexpected]

Hello all!

I wanted to post a small update. Currently, everything is running perfectly and the horizontal reactor "Horizontal reactor" as I call it is performing better than imagined. I'm only seeing a .02 to .04 variance from peak pH drop to mid photo period. This has inspired me to make some changes and have another go at the AGA Dutch competition.

I ordered 2 Weak Aqua P600's and ripping the hardscape out to begin my journey. I think this will give the Horizontal reactor a solid stress test and will report back here from time to time.

Here's a quick shot of what the tank looks like currently. It's a bit haphazard and has only been running for a month and a half. As you can see, my current light doesn't cover the entire tank. I'd imagine these new lights will push the tank much harder. I'm excited to see how the reactor performs with increased demand.

 

[Unexpected]

I was able to get the hardscape pulled and spread some plants around to begin propagation and species selection. The last round of plants arrive Thursday and the Weak Aquas are in the mail. I've increased nutrients, raised GH and increased tank turnover along with increased CO2. Initially, the pH increased by a .1. This tank degasses quite well so this .1 increase makes sense. Just a small bump was all that that was needed to bring it back down.

This small bump in demand was easily handled by the reactor.

 

[Hufsa]

I was able to get the hardscape pulled and spread some plants around to begin propagation and species selection.

Ooooooohh so much room for plants 👁️👄👁️

is there a journal associated with this tank? I want to live vicariously 😅

 

[Unexpected]

Ooooooohh so much room for plants 👁️👄👁️

is there a journal associated with this tank? I want to live vicariously 😅

I don't have one for this tank. Would it be weird to start one since it's already going?

 

[MichaelJ]

Would it be weird to start one since it's already going?

Not at all... plenty of folks around here did that... including myself.

I sort of like @Hufsa's idea of experiencing the hobby through someone else's tank.... Imagine how much money, time and headache we could save if we could just ask some of the best tank keepers around here to install a webcam in front of their tanks and let us peek in at our leisure... No? 🙂

Cheers,
Michael

 

[Unexpected]

let us peek in at our leisure

That would be great.

 

[Unexpected]

I finally got around to being less lazy and found out my degassed pH level. The tank is officially at a 1.5 pH drop. The amazing thing is the length and diameter used. The second pipe purges the excess CO2 right when it's hitting the 1.5 drop. There's no way I can gas my fish at this point and I see no reason to continue running my CO2 controller. My goal now is to reduce injection rate to reduce or eliminate the purge yet keep the 1.5 drop.

Unfortunately, my new lights did not include the hanging kit and I had to buy them separately. So there's a small delay with performance under higher light.

 

[22802]

I finally got around to being less lazy and found out my degassed pH level. The tank is officially at a 1.5 pH drop. The amazing thing is the length and diameter used. The second pipe purges the excess CO2 right when it's hitting the 1.5 drop. There's no way I can gas my fish at this point and I see no reason to continue running my CO2 controller. My goal now is to reduce injection rate to reduce or eliminate the purge yet keep the 1.5 drop.

Unfortunately, my new lights did not include the hanging kit and I had to buy them separately. So there's a small delay with performance under higher light.

Thank you for the update @Unexpected . At some point in the future I will collect all user data, and update / fine-tune the design rules so that new users can hit the right dimensions first time.

With the reactor now purging at 1.5 pH drop we achieve the same inherent safety feature (impossible to inject too much CO2 and gas fish) that I found on the CO2 Spray Bar and that applies to this reactor as well. Now going forward you could consider using the "overflow mode" that I described for CO2 Spray Bar and use the slow self purging to stabilise the CO2 ppm at your desired level. If that works well (it did for me), you do not longer need a precision CO2 regulator, nor a CO2 controller, as the reactor will control your CO2 injection rate.