External CO2 reactor design

[PeterGwee]

Tom, something about planted tank related stuff then since you are not interested in the website design.

I know from the APD that your external reactor design places much emphasis on the CO2 being fed into the suction of a small powerhead (smaller bubbles = more surface area of contact.) which is then output into the external reactor. Now, since the bubbles are being smaller and hence lighter, do they get carried out by the water current more easily such that it bypasses the entire reaction chamber? (I know I ask you alot of times about this issue offlist...I have yet to make a workable one that has a very fast response time though.). When I use a maxi jet of around 225gal/hr flowrate, I get small bubbles exiting after some gurgling noise in the reaction chamber whereas a powerhead of 120gal/hr does not but the flowrate out the reactor is kinda weak. (potential response time issue since the flow is low?). What is so different in your reactor? When will the article on reactor design be up?


Regards

Peter Gwee

 

[Tom Barr]

Re: External CO2 reactor design

They will bypass the chamber if the chamber's capcity is exceeded, the contact time is too low, the design is too narrow and does not allow the bubbles to flat up or stay suspended long enough etc.

You can reduce the flow or expand the reactor tube length, shape or diameter. You can also increase the bubble size. That does not help responsiveness(reduces it), but increases the efficiency.

If you change the tube size and add more flow, more contact time, you will have more responsiveness and efficency, but then you have a big device.

Not bad if it's outside the tank. For the intenal designs, this seldom matters much. The DIY internal is very good on tanks up to about 40-50 gallons, if you use a Rio 180-200 and a 6" tube near the outflow of a filter, this will be fine for larger tanks also. You can also use 2 small ones on a large tank etc.

I'm not sure about the External, I'll get to it shortly, I have many things going on these days. I'm just happy to get the new software for the sitre up and Greg is being worked like a slave on a Viking Row boat.

It works very well efficiency wise, removes the O2(or excess CO2) automatically as the levels falls in the reactor chamber. This reduces efficiency at the expense of maintaining good contact with CO2 and repsonsiveness/reducing gas lock back pressure.

So it will bubble out some fine mist but not much since the venturi recirculates and the size and diameter of the tube is larger than the 2" sizes for the internals(You can get the larger sizes for the internals, but then they get big in the tank, outside the tank, the size and length issue is not a big deal).

Regards,
Tom Barr

 

[PeterGwee]

Re: External CO2 reactor design

Tom, the conditions that you stated are if the reactor chamber is the one causing the problem (too small) but if the pump is oversized, the ideal solution would be to slow down the flowrate?

I was wondering how do you go about picking the ideal powerhead flowrate for a particular tank? Eg. 100gallon, 55gallon and etc. For internals, due to less pressure head and tube friction, the flowrate tends to be lower?

Regards
Peter Gwee

 

[Tom Barr]

Re: External CO2 reactor design

I keep the flow rate high as possible and then good mixing as it leaves the reacting chamber with tank water(place near a spray bar etc).

Regards,
Tom Barr