Method for carrying out air oxidation and for adding fine bubbles to a liquid

A method of carrying out an air oxidation reaction in a liquid phase, comprising:

• substantially continuously feeding liquid and air at respective flow rates to an oxidizing tank via a bubble-forming device having no moving parts, the bubble-forming device being fixed at the bottom of said oxidizing tank to carry out air oxidation therein;
• feeding a part of the liquid out of the oxidizing tank via a lower port provided at the lower portion of said oxidizing tank to a gas-liquid separating device;
• returning the liquid free from gas from the separating device to the oxidizing tank through the bubble-forming device;
• supplying a stock solution from a liquid-conditioning tank and mixing the returned liquid from the gas-liquid separating device with the stock solution before the resulting mixture is fed to the bubble-forming device;
• maintaining the ratio of total liquid flow rate and total gas flow rate to said bubble-forming device at at least 1/2 (M.sup.3 /NM.sup.3);
• returning the air separated from the liquid in the gas-liquid separating device to the oxidizing tank;
• and
• overflowing out the finished solution from an upper overflow port located at the upper portion of said oxidizing tank;
• the step of substantially continuously feeding liquid and air to an oxidizing tank via a bubble-forming device, comprising:
• feeding air into the lower chamber of a two-chamber bubble-forming device via at least one nozzle, said at least one nozzle being aligned with and directed toward a respective orifice in a partition which divides said bubble-forming device into said two chambers, the air being fed via said nozzle to maintain the velocity of the stream passing through said orifice at at least 3 m/sec., a narrow space being provided between the nozzle tip of said at least one nozzle and the opening of its respective orifice, said narrow space being between about 0.8-2.0 times as large as the opening diameter of said orifice;
• feeding said liquid into said lower chamber of said bubble-forming device via a conduit;
• feeding said liquid and the outlet air of said at least one nozzle as a mixture through said respective orifice in said partition against the upper wall of the upper chamber of said bubble-forming device to more fully mix same, the distance between the upper surface of said partition and the lower surface of said upper wall of said upper chamber being about 1.0-5.0 times as large as said opening diameter of said orifice;
• and
• discharging said fully mixed fluid containing an enormous number of very fine air bubbles from an orifice in the upper chamber of said bubble-forming device and into said oxidizing tank.