System and method for dissolving gases in liquids

Abstract

Apparatus and methods for dissolving a gas into a liquid comprises a saturation tank, a high pressure liquid pump in fluid communication with the tank, and a pressurized gas source in communication with a regulated gas head space of the saturation tank. The saturation tank comprises a pressure vessel for containing the liquid and has a regulated gas head space above the liquid, contains at least one liquid spray nozzle that permits passage of liquid into the pressure vessel, and an outlet for the liquid containing dissolved gas. Upon passing the gas-containing liquid into a second fluid, the gas is released in the form of microbubbles. The microbubbles aid in flocculation of suspended particles and promote dissolution of the gas in the second fluid. Preferred gases for use with the apparatus are oxygen, air, and ozone. Anticipated uses include treatment of rivers, streams, and ponds in natural or industrial settings, as well as smaller scale applications.

1 . An apparatus for dissolving a gas in a liquid comprising: 
 (a) a saturation tank comprising (i) a pressure vessel for containing the liquid and providing a regulated gas head space above the liquid, (ii) at least one liquid spray nozzle that permits passage of liquid into the pressure vessel, and (iii) an outlet for the liquid;    (b) liquid pumping means in fluid communication with the at least one liquid spray nozzle;    (c) a source of the gas in communication with the regulated gas head space of the saturation tank; and    (d) a chamber external the saturation tank and connected thereto via the liquid outlet, which chamber is provided with a plurality of orifices through which liquid containing dissolved gas from the saturation tank can be released into a region external the chamber.    
   
   
       2 . The apparatus of  claim 1 , wherein said region external the chamber has a lower pressure than internal the chamber, so that the saturation concentration for the dissolved gas in liquid exiting the chamber is exceeded and microbubbles of gas are formed at or near the chamber orifices.  
   
   
       3 . The apparatus of  claim 2 , wherein the microbubbles have an average diameter less than about 150 microns.  
   
   
       4 . The apparatus of  claim 1 , wherein the gas is selected from the group consisting of air, oxygen, ozone, hydrogen, nitrogen, nitrous oxide, and carbon dioxide.  
   
   
       5 . The apparatus of  claim 1 , wherein the liquid primarily comprises water.  
   
   
       6 . The apparatus of  claim 1 , wherein the pressurized pumping means is provided by (i) a high pressure liquid pump, (ii) a line source in a residential or industrial setting, or (iii) a plurality of fixed volume vessels capable of forcing liquid into the saturation tank upon pressurization of the fixed vessel with a high pressure gas that enters the vessel and displaces the liquid through an outlet in the vessel.  
   
   
       7 . The apparatus of  claim 1 , wherein the ratio of liquid volume to head space gas volume in the saturation tank is maintained with an open-loop or closed-loop control system.  
   
   
       8 . The apparatus of  claim 1 , wherein the number, size, and placement of orifices in said chamber are predefined so as to permit the rate of liquid flow rate out of the chamber to balance the rate of liquid flow into the saturation tank, thereby maintaining a constant desired pressure internal the saturation tank under constant flow conditions.  
   
   
       9 . The apparatus of  claim 1 , wherein the orifices have a diameter in the range of about 1 mm to about 15 mm.  
   
   
       10 . The apparatus of  claim 1 , wherein said chamber is provided internal a liquid entrainment means, so that the liquid containing dissolved gas exiting the chamber mixes with lower pressure ambient liquid.  
   
   
       11 . The apparatus of  claim 1 , wherein the gas saturation threshold for the liquid is thermally controlled.  
   
   
       12 . The apparatus of  claim 1 , wherein said at least one spray nozzle is adjustable so as to optimize the liquid droplet size and control the rate of gas saturation in the liquid.  
   
   
       13 . The apparatus of  claim 1 , wherein the source of gas comprises means for separating oxygen from ambient air.  
   
   
       14 . The apparatus of  claim 1 , wherein the source of gas comprises an ozone generator provided internal the saturation tank.  
   
   
       15 . The apparatus of  claim 1 , further comprising a control system for controlling operation of the apparatus.  
   
   
       16 . The apparatus of  claim 1 , further comprising a feedback loop that permits recovery and recycling of the gas to the saturation tank.  
   
   
       17 . A method of dissolving a gas in a liquid comprising: 
 (a) pressurizing an enclosed vessel with the gas;    (b) spraying a first portion of the liquid into the vessel containing the gas under conditions effective to dissolve the gas in the liquid;    (c) passing the first portion of liquid containing dissolved gas from the vessel into a chamber that is provided with a plurality of orifices and which is immersed in a second portion of the liquid; and    (d) discharging the first liquid portion containing dissolved gas through the chamber orifices into the second liquid portion.    
   
   
       18 . The method of  claim 17 , wherein said pressurizing is conducted with a gas selected from the group consisting of air, oxygen, ozone, hydrogen, nitrogen, nitrous oxide, and carbon dioxide.  
   
   
       19 . The method of  claim 17 , wherein said spraying is performed with a liquid primarily comprising water.  
   
   
       20 . The method of  claim 17 , wherein said spraying is performed until the first portion of liquid is dissolved with gas to 95% of saturation at the enclosed vessel pressure.  
   
   
       21 . The method of  claim 17 , wherein the gas is separated on-site from ambient air prior to being pressurized into the vessel.  
   
   
       22 . The method of  claim 17 , wherein said pressurizing is conducted with ozone gas.  
   
   
       23 . The method of  claim 17 , wherein the gas is provided by on-site generation.  
   
   
       24 . The method of  claim 17 , wherein the liquid is provided by a water tap located in a residence or industrial site and liquid is transferred into the vessel under tap pressure.  
   
   
       25 . The method of  claim 17 , which is performed in continuous mode.  
   
   
       26 . The method of  claim 17 , wherein the liquid is sprayed into the vessel under pressure provided by a high pressure liquid pump.  
   
   
       27 . The method of  claim 17 , wherein fluid flow into the vessel from a high pressure pump is controlled via feedback from sensors indicating water capacity within the saturation tank.  
   
   
       28 . The method of  claim 17 , wherein said discharging of liquid containing dissolved gas is effective to: (i) enhance microbe growth and respiration rate in waste water treatment, fermentation processes, food synthesis and manufacturing, or solid waste treatment; (ii) promote physical flotation of matter suspended in the liquid; (iii) quench anaerobic biological activity in the liquid; (iv) produce nanobubbles (10-100 nm diameter); (v) foam a polymer; (vi) create a biorefuge for attracting or sustaining fish populations; (vii) sterilize a body of water; (viii) facilitate surface freezing while aerating/oxygenating during cold weather; (ix) to control odor, antibiotic residuals, and/or bacterial loads in sewage transport conduits; (x) improve the quality of water entering, transducing, or exiting a darn; (xi) improving aerobic digestion efficiency and/or odor control in a wastewater treatment pond (lagoon); (xii) respond to a pollutant spill into an environmental water body; (xiii) isolate and/or treat a plume of pollution; (xiv) disinfect and reduce organic carbon in drinking water; (xv) control aerobic and anaerobic conditions in biological processes associated with pharmaceuticals and biotechnology; (xvi) deliver hydrogen or other gases to create and control aerobic and anaerobic conditions in biological processes associated with in situ waste treatment in groundwater; (xvii) deliver hydrogen or other gases to create and control aerobic and anaerobic conditions in biological processes associated with in situ waste treatment in surface waters; (xviii) deliver a high concentration of dissolved oxygen to enhance biological oxidation of organic carbon and nitrogen removal within wastewater treatment facilities; (xix) oxidize sediment in situ for enhanced bioremediation of contaminants sorbed to and associated with river, lake, and estuarine sediments; (xx) enhance oxygen treatment of refractory pollutants such as antibiotic residuals, endocrine disruptors, pesticides, and similar chemicals; (xxi) enhance ozone treatment of refractory pollutants such as antibiotic residuals, endocrine disruptors, pesticides, and similar chemicals; (xxii) inject supersaturated stream of oxygen, ozone, hydrogen or other gases for direct treatment or enhancing treatment of groundwater to remove pollutants; (xxiii) increase the rate of BOD removal because of improved treatment rate from smaller bubble size; or (xxiv) increase the thickness of the aerobic layer in sediment for increase storage capacity of phosphorus or other water pollutants.