The most annoying thing about running a horizontal reactor in overflow mode….

[Pepere]

Especially with a bubble counter with a needle valve….

So reading @Yugang description you want to adjust so you get a single bubble come out the outflow every 75-90 seconds I believe…

This ensures the gas in the chamber is predominantly co2 as atmospheric air also comes out of the water into the chamber, and keeps wasted co2 to a minimum vs having too much co2 escaping the system..

Well, first of all, running a spray bar you dont get a single bubble but a bunch of small bubbles. And the timing of those bubbles is not terribly consistent. I can have no bubbles for a minute, a blurp, and then another blurp 20 seconds later, followed by 45 seconds of no bubbles followed by 90 seconds of no bubbles…

The volume of bubbles each blurp also varies…

And adjusting bubble count in a bubble counter is a sysiphian task…. Add to that having more than one bubble counter on a manifold….as you adjust 1 bubble counter, the other one is also affected since unlike a ceramic diffuser, there is precious little pressure once the bubble escapes the needle valve…

So here is what I have worked out as the best I could come up with.

I turned the pressure as high as it could go and filled both chambers until bubbles were blowing out both spray bars in the two tanks…. Aimed for about every 2-3 seconds or so. Where both tanks were different size, a 75 and a 29, I aimed for the smaller tank to have thefaster purging of the two.

Once that was achieved, I then start dialing down the secondary pressure out of the regulator…



Now since the bubbles through a spray bar is not regular in rythym, I set a timer for 5 mi utes and counted how many episodes of bubble blurps popped out and divided 300 by the number of blurps…. This gave the average number of seconds between blurps…. Once I got around an average of 60 seconds a blurp. I left it be for an hour and then checked again and fine tuned it a bit…

Solenoid will be shutting off soon. Tomorrow I will run multiple ph tests over the course of the morning to graph the ph drop over time and when I get to equilibrium…

 

[HardeeParty]

So wait, the new measure of injection rate is blurps per minute (bpm)?

 

[Pepere]

So wait, the new measure of injection rate is blurps per minute (bpm)?

Well, you could reduce co2 to point you dont get any blurps from the outlet.. that would decrease co2 waste at the cost of reduced ppm in the water column…

I will be curious to run ph drop tests tomorrow…

 

[Yugang]

The title of the thread caught my eye

The basic idea of overflow mode is to stabilise CO2 injection by the reactor’s geometry, and we don’t care much about how much CO2 flows from the regulator.

Optimising the frequency of bubble release from the overflow is unnecessary.

Let’s first take a step back, and explain overflow mode for readers who are not familiar with the concept.

The assumption for the horizontal reactor in overflow mode is that the rate of CO2 injection is proportional to the surface area between flowing water and a pocket of “pure” CO2 above it. So we can stabilise the rate of injection if

• the surface area is constant, ie we inject enough CO2 so that the reactor is always filled to its maximum. The surface area is then determined by the reactors geometry and position of overflow.
• The CO2 pocket is almost pure CO2, and not too much diluted by other gases that would compromise the efficiency of CO2 absorption in the water. These other gases would not be injected, as our bottle has pure CO2, but rather originate from back diffusion from the aquarium water into the CO2 gas pocket.

We might conclude that we’ll inject a lot of CO2 into the reactor, which will always be full of CO2 with a constant surface area. All other gases (oxygen, nitrogen) will be purged by escaping gas bubbles from the overflow. However, we care about efficiency and don’t want to lose too much CO2.

Post in thread 'Horizontal CO2 Reactor - Yugang 鱼缸 Reactor'

Oct 8, 2023

Context

As described earlier, we could operate the reactor in three different ways

• Using a pH/CO2 controller for CO2 injection and stability
• Using a precision CO2 regulator to precisely adjust CO2 injection
• Overflow mode.

Most current users are either using a pH/CO2 controller or a precision CO2 regulator. There will be a reservoir of almost pure CO2 gas in the reactor, and the physics/chemistry of CO2 absorption into the water will be similar to any other reactor that may or may not use CO2 bubbles. As is also the case in bubble reactors, gradually we...

• Yugang

• 
• 

In post 156 in the reactor thread I calculated how much extra CO2 we would have to inject to have sufficient purging to keep the gas pocket pure CO2, while not wasting more CO2 than necessary. Roughly speaking, if we inject some 10% extra CO2, as compared to what the reactor injects in the water, then we may assume that the injection rate is constant and not dependent anymore in the flow from the regulator. In other words, if we see just a little bit of gas coming from the overflow from time to time, we are good.

With my calculation to find an optimum between stability and CO2 consumption I may have caused some confusion with readers. It was not meant to say that now we need to measure the rate of overflow. In practice, if we see some gas escape from time to time, we are good.

Finally, the best indicator that I use to monitor overflow mode is not the rate of bubbles escaping, but rather the volume of gas that remains in the reactor a few hours after CO2 off in the evening. If CO2 in the gas pocket was perfectly pure with good overflow mode, it would all be absorbed and no gas left the the evening. If I would see still a significant pocket of gas in the evening it tells me that other gases have accumulated in the reactor, and that it would be good to give it a bit more CO2 injection to purge it.

 

[Burr740]

I love these threads! lol. @Pepere maybe I missed it but do you have two separate needle valves for both tanks, or are you just splitting off one needle valve into two bubble counters?

This is the sentence that threw me off

And adjusting bubble count in a bubble counter is a sysiphian task…. Add to that having more than one bubble counter on a manifold….as you adjust 1 bubble counter, the other one is also affected since unlike a ceramic....

 

[Cornelius]

Especially with a bubble counter with a needle valve….

A reactor is generally used in large tanks.
A bubble counter is a bit useless because the injection rate is so high that you can't count the bubbles anyway?

 

[Yugang]

A reactor is generally used in large tanks.
A bubble counter is a bit useless because the injection rate is so high that you can't count the bubbles anyway?

I'll answer this in the context of using the horizontal reactor in overflow mode.

First, as the reactor stabilises CO2 injection, we don't really care about CO2 flow or measuring bubble per second.

In my reactor I inject the CO2 through a tube that is below the water surface in the reactor. The bubbles that escape are larger than the small bubbles we typically see in bubble counters. On my 50 gallon tank I know I need 3-4 bubbles per second, as visible within the reactor, and can estimate that by eye without using any video in slow motion. Then I use the overflow as well as the remaining gas pocket after CO2 off to check if my injection is good enough for stable overflow mode, and I don't care really about accurately counting bubbles per second.

 

[Pepere]

maybe I missed it but do you have two separate needle valves for both tanks, or are you just splitting off one needle valve into two bubble counters

I have needle valves for each bubble counter.

What I have found, is that since there is low pressure after the bubble counter with horizontal reactors due to no ceramic diffuser creating back pressure is that as you adjust 1 buble counter needle valve, it subtly affects the pressure and flow on the other one as well..

The best I have found is to get them both at a similar over flow rate and then back off the pressure on the regulator to slow down the overflow from both reactors…


Needle valves are frustratingly imprecise in adjusting flow…. A tiny mov3ment of the valve results in huge differences in flow…

 

[Pepere]

In my reactor I inject the CO2 through a tube that is below the water surface in the reactor. The bubbles that escape are larger than the small bubbles we typically see in bubble counters

Fair enough if you have a transparent reactor…

Mine are cheap pvc pipe and opaque….

I view the bubble counter simple for visual indication that flow rate has increased or decreased some…

Where there is minimal back pressure from the horizontal reactors due to being that there is no ceramic diffuser, there is much less pressure on the secondary guage of the regulator. The pressure on the redulator affects how much gas is in a bubble in the bubble counter. Hence I use the regulator pressure to fine tune the amount of gas entering the reactor after making gross adjustments with the needle valves are. Easier to do when you only have 1 bubble counter downstream from the regulator…

 

[Yugang]

Fair enough if you have a transparent reactor…

Mine are cheap pvc pipe and opaque….

I view the bubble counter simple for visual indication that flow rate has increased or decreased some…

Where there is minimal back pressure from the horizontal reactors due to being that there is no ceramic diffuser, there is much less pressure on the secondary guage of the regulator. The pressure on the redulator affects how much gas is in a bubble in the bubble counter. Hence I use the regulator pressure to fine tune the amount of gas entering the reactor after making gross adjustments with the needle valves are. Easier to do when you only have 1 bubble counter downstream from the regulator…

Is it fair to state that you would have same, if not more challenges when using a vertical bubble reactor? The root cause seems to be your setup serving multiple tanks from one CO2 supply, not so much your reactor.

If your reactor is not transparent, no worry. Just observe if from time to time you see some gas bubbles from your spray bar, and all be good then. Only worry if you never see some gas coming out (not in overflow mode) or really a lot (waste of CO2, but perfect stability). Don't try to measure how many bubbles come from your overflow, I believe that is the key message in reply to your original post.

 

[Pepere]

Is it fair to state that you would have same, if not more challenges when using a vertical bubble reactor?

Needle valves and bubble counters are a pain regardless what you are using to inject co2 into the tank with.

The beauty of the horizontal reactors with overflow is the inherent safety limiting risk of gassing the fish…

The only difficulty I face is limiting the overflow to minimize gas waste as fine adjustment abilities via needle valve is limited…

I love the reactor. The needle valve, not so much…

It was a game changer for me to hatch on the idea of using the needle valve for gross adjustment and the regulators pressure valve to fine tune the output. Seeing as the horizontal reactors with overflow does not have a ceramic diffuser to push gas through, actual secondary pressure is not as critical to an absolute pressure,

 

[Yugang]

I love the reactor. The needle valve, not so much…

Same here, this is why I started to think about CO2 a few years ago. We had a lot of discussion in the community, hoping for a good regulator for 100-150 USD at most. Hobby-grade regulators, even from renowned brands, lack the stability and longevity we require. We’d need to invest in a more professional-grade regulator, which I considered beyond my budget.

So that's why I started to think about alternative solutions, and believe that the reactor not only addresses the stability issue, but a lot more. I really don't care about my regulator any more.

 

[Unexpected]

Those cheap needle valves are the problem. Saving money for a bigger headache .

 

[Unexpected]

And since we are on the subject of regulators, I asked Alanle if he could build me a budget option. This was only 240 and has a precision needle valve. Heck, GLA pro series are more than this and their needle valve is meh.