[APD] Re: CO2 reactor orientation

[Bill Wichers <billw at waveform_net>]

> Is it determined that an external, "bio-ball-type" CO2 reactor needs to be
> counter-current (i.e. water flow down while gas is injected at the bottom)
> -?  I thought I had once read (can't remember where) that good diffusion may
> also happen when gas and water are flowing up together.  It was probably a
> discussion of protein skimmers, but the principle should be the same - how
> to maximize the gas/water interface.  I ask because I want to add the
> reactor inline to the output end of the canister, without looping up then
> down.  What's your opinion?  Thanks...
>
> Lew Newcomb
> SE Michigan

The general idea is to keep the CO2 bubbles in contact with water for as 
long as possible. With a counter-current setup, the flow of the water helps 
to keep the bubble suspended (rather than shooting it out the outlet of the 
reactor) longer and thus provides a longer contact time and more efficient 
operation as a result. Protein skimmers work on a rather different 
principle since they end goal to remove as large an amount of dissolved 
organics as possible rather than to maximize gas exchange in the water. 
Even so, most of the better skimmers are counter-current designs. The 
skimmers also need long contact times, but for different reasons.

You should see maximum efficiency using a counter-current setup in your 
reactor. Hose is cheap and will only cost you once, while the efficiency 
you gain will save you real money in the form of fewer CO2 tank refills 
over the long term.

        -Bill


*****************************
Waveform Technology
UNIX Systems Administrator

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