Reactor

Abstract

A reactor for aerating a fluid with a gas comprises a mixing tank ( 12 ) for the fluid and a centrally located vertical draft tube ( 13 ) submerged in the fluid to divide the mixing tank ( 12 ) into an inner chamber ( 21 ) and an outer chamber ( 23 ). The reactor further comprises a motor driven axial flow impeller ( 14 ) located in the draft tube ( 13 ) for circulating fluid downwardly through the inner chamber ( 21 ) and upwardly through the outer chamber ( 23 ). The reactor further comprises an external circuit for withdrawing a portion of the fluid from the mixing tank ( 12 ), aerating the fluid, and returning the aerated fluid to the mixing tank ( 12 ). The aerator is in the form of a venturi device ( 17 ).

1 . A reactor for introducing a gas into a fluid comprising, a mixing tank for the fluid, a partition means for dividing the tank into at least two chambers and for allowing the fluid to flow between the chambers at a lower region and an upper region of the tank, a pump means located in one of the chambers for circulating the fluid downwards in one chamber and then upwards in the other chamber, a means for creating a region of reduced pressure in a portion of the fluid, a means for introducing the gas into the fluid in the region of reduced pressure to aerate the fluid, and a means for introducing the aerated fluid into the circulating fluid in the tank.  
     
     
         2 . The reactor defined in    claim 1   , wherein the partition means comprises a draft tube adapted to be submerged in the fluid in the tank, the draft tube having an open upper end and an open lower end.  
     
     
         3 . The reactor defined in    claim 2   , wherein the tank is cylindrical and the draft tube is located centrally in the tank to divide the tank into an inner chamber and an outer annular chamber.  
     
     
         4 . The reactor defined in any one of the preceding claims wherein the pump means comprises an axial flow pump.  
     
     
         5 . The reactor defined in    claim 4   , wherein the axial flow pump comprises an impeller located in the draft tube.  
     
     
         6 . The reactor defined in    claim 1   , wherein the means for creating the region of reduced pressure in the fluid comprises a tubular member which has a region of restricted cross-section for imparting a venturi effect to the fluid passing through the tubular member whereby the velocity of the fluid increases and the pressure of the fluid decreases in the region of restricted cross-section.  
     
     
         7 . The reactor defined in    claim 6   , wherein the region of restricted cross-section is formed by providing a throat in the tubular member.  
     
     
         8 . The reactor defined in    claim 6   , wherein the region of restricted cross-section is formed by inserting a restriction in the tubular member.  
     
     
         9 . The reactor defined in    claim 1   , wherein the means for introducing the gas into the fluid comprises a porous membrane, holes, or jets.  
     
     
         10 . A method of introducing a gas into a fluid comprising, circulating the fluid by means of a pump means in a mixing tank having at least two chambers that are in fluid communication at upper and lower regions of the tank so that the fluid flows downwards in one chamber and upwards in the other chamber, creating a region of reduced pressure in a portion of the fluid, introducing the gas into the portion of the fluid in the region of reduced pressure to aerate the fluid, and introducing the aerated fluid into the circulating fluid in the tank.  
     
     
         11 . A reactor for introducing a gas into a fluid comprising, a mixing tank for the fluid, a draft tube for dividing the tank into at least two chambers, the draft tube having an open upper end and an open lower end for allowing the fluid to flow between the chambers at a lower region and an upper region of the tank, an axial flow pump having an impeller located in the draft tube for circulating the fluid downwards in the draft tube and then upwards in the other chamber, a means for creating a region of reduced pressure in a portion of the fluid comprising a tubular member which has a region of restricted cross-section for imparting a venturi effect to the fluid passing through the tubular member whereby the velocity of the fluid increases and the pressure of the fluid decreases in the region of restricted cross-section, a means for introducing the gas into the fluid in the region of reduced pressure to aerate the fluid, and a means for introducing the aerated fluid into the circulating fluid in the tank.