I believe Ghorigs reactor has the co2 coming in near the top. The closer to the bottom of the reactor without letting undissolved co2 escape, the better. Flow rate thru the reactor has a big effect on how close to the bottom you can let co2 in. The higher the flow rate of water thru the reactor the closer to the top of the reactor you have to put the inlet for the co2.
The reactor is far more efficient when the co2 bubbles churn in the water inside the reactor. It is less efficient if co2 is allowed to pool at the top of the reactor.
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