Apparatus and method for dissolving a gas in an aqueous stream

A vessel, for dissolving a gas in water, having a vertical axis and which is circular in horizontal section for most of its height;

• the vessel having upper and lower ends;
• the vessel including a conical portion with the apex at the upper end of the vessel;
• an aqueous stream inlet tangential to the vessel and communicating with the vessel interior space near the vessel upper end, whereby an aqueous stream fed to the vessel through the inlet rotates in a downwardly moving spiral stream from a high downward velocity in the upper portion of the vessel to a lower downward velocity in the lower portion of the vessel;
• and
• a gas diffuser means in the vessel for diffusing a gas into the aqueous stream so as to produce small gas bubbles which are rotated in generally spiral path by the aqueous stream thereby providing a long flow distance over which the bubbles have increased contact time with the aqueous stream to facilitate dissolution of the gas therein and in which rising of the gas bubbles is progressively opposed by the increased downward velocity of the aqueous stream higher in the vessel.

In combination:

• a reaction tank having a bottom and side wall extending up from and joined to the bottom thereby defining an aqueous liquid retaining space;
• a vessel, for dissolving a gas in water, having a vertical axis and which is circular in horizontal section for most of its height, the vessel having upper and lower ends, the vessel including a conical portion with the apex at the upper end of the vessel, and an aqueous stream inlet tangential to the vessel and communicating with the vessel interior space near the vessel upper end, whereby an aqueous stream fed to the vessel through the inlet rotates in a downwardly moving spiral stream from a high downward velocity in the upper portion of the vessel to a lower downward velocity in the lower portion of the vessel;
• the vessel being positioned vertically in the tank and having means at the vessel bottom portion for an aqueous stream to flow out of the vessel into the tank;
• means at the upper portion of the tank for removing an aqueous stream from the tank;
• and
• a gas diffuser means in the vessel for diffusing a gas into the aqueous stream so as to produce small gas bubbles which are rotated in a generally spiral path by the aqueous stream thereby providing a long flow distance over which the bubbles have increased contact time with the aqueous stream to facilitate dissolution of the gas therein and in which rising of the gas bubbles is progressively opposed by the increased downward velocity of the aqueous stream higher in the vessel.