Method and apparatus for passively bubbling gas through liquid

Patent metadata

Field	Value
Publication number	US-11400419-B2
Application number	US-201816959984-A
Country	US
Kind code	B2
Filing date	Dec 24, 2018
Priority date	Jan 2, 2018
Publication date	Aug 2, 2022
Grant date	Aug 2, 2022

Abstract

Methods and apparatuses for adding gas bubbles to a tank containing liquid at locations that allow the bubbles to rise to the top of the tank are disclosed. One embodiment comprises a membrane filtration system connected to a gas source and a drain. The membrane filtration system draws gas into the system from the gas in response to a reduced pressure profile created by opening a drain. The gas may be air supplied at atmospheric pressure.

First claim

What is claimed is:

1. A method for introducing gas into a liquid, the method comprising:
reducing a pressure of the liquid within a closed tank by placing the liquid within the tank in fluid communication with a fluid outlet such that, at a gas supply location above the fluid outlet, the pressure of the liquid is reduced from a pressure that is greater or equal to a gas supply pressure to a reduced pressure that is lower than the gas supply pressure;
supplying a gas at the gas supply pressure at the gas supply location, allowing the gas to enter the liquid as a result of the difference between the reduced pressure of the liquid and the gas supply pressure; and
allowing the gas to rise from the gas supply location through the tank and allowing the liquid displaced by the gas to exit by way of the fluid outlet.

2. The method according to claim 1 wherein the gas supply pressure is ambient atmospheric pressure.

3. The method according to claim 1 wherein the gas is ambient air.

4. The method according to claim 1 wherein supplying the gas at the supply location comprises opening a gas supply valve.

5. The method according to claim 4 wherein placing the liquid within the tank in fluid communication with the fluid outlet comprises opening a drain valve that is below the gas supply location.

6. The method according to claim 5 comprising opening the gas supply valve after the drain valve has been opened.

7. The method according to claim 1 wherein supplying the gas at the supply location comprises draining any of the liquid out of an open gas supply conduit that is open to the atmosphere at a location above the gas supply location.

8. The method according to claim 1 wherein the fluid outlet connects to the tank by way of a drain line and the gas supply location is in the drain line.

9. The method according to claim 8 wherein the gas enters the tank by way of the drain line.

10. The method according to claim 1 wherein the gas supply location comprises a port located at or below a bottom of the tank.

11. The method according to claim 1 wherein a filter is located in the tank and the method comprises allowing the gas to scour the filter as the gas rises through the tank.

12. The method according to claim 11 wherein the reduced pressure draws liquid from a permeate tank located above the closed tank back through a permeate line in fluid communication with the filter to backwash the filter.

13. The method according to claim 11 comprising allowing foulants scoured from the filter to drain by way of the fluid outlet.

14. The method according to claim 11 comprising subsequently refilling the tank with the liquid through a liquid inlet and applying a pressure differential to cause the liquid to pass through the filter wherein refilling the tank comprises venting the gas from a gas vent valve of the tank.

15. The method according to claim 1 wherein the liquid is water.

16. Apparatus for introducing gas into a liquid, the apparatus comprising:
a closed tank having a drain port located at or near a bottom of the tank;
a downwardly extending conduit connecting the drain port to a fluid outlet located below the tank;
a drain valve connected between the drain port of the tank and the fluid outlet, the drain valve operative to place an interior of the tank in fluid communication with the fluid outlet;
a gas source in fluid communication with the interior of the tank, the gas source arranged to supply a gas at a gas supply location at an elevation above the fluid outlet and below a top of the closed tank;
and a controller connected to control the drain valve, the controller configured to periodically open the drain valve to reduce a pressure within the liquid at the gas supply location from a pressure that is above a pressure of the gas to a reduced pressure that is below a pressure of the gas to thereby allow the gas to enter the tank as a result of the difference between the reduced pressure within the tank and the pressure of the gas.

17. The apparatus according to claim 16 wherein the gas source is operative to supply the gas at atmospheric pressure and the gas source comprises a source of air.

18. The apparatus according to claim 17 wherein the gas supply comprises an open gas supply conduit that is open to the atmosphere at a location above the gas supply location.

19. The apparatus according to claim 16 comprising a filter in the tank, the filter located in a path taken by the gas in rising through the tank such that the rising gas scours the filter.

20. A membrane filtration system comprising:
a tank comprising at least one fluid port located at or near a bottom of the tank;
a membrane filter in the tank, the membrane filter connected to a permeate line that exits the tank;
a drain line in fluid connection with an interior of the tank by way of the at least one fluid port;
a drain valve operative to open or close the drain line;
a liquid supply valve in fluid communication with the interior of the tank and a liquid supply connected to supply liquid to the interior of the tank by way of the liquid supply valve and the at least one fluid port;
a gas source connected to supply gas at a gas supply location in fluid communication with the interior of the tank, the gas supply location at an elevation below the filter and above an outlet of the drain line; and
a controller connected to control the drain valve and the liquid supply valve and configured to close the liquid supply valve and open the drain valve to thereby reduce a pressure within the liquid at the gas supply location from a pressure above a pressure of the gas to a reduced pressure below the pressure of the gas to allow the gas to enter the liquid as a result of the difference between the reduced pressure within the liquid and the pressure of the gas and to bubble upwardly past the filter.

Assignees

• Univ British Columbia

Inventors

• Bérubé Pierre

Classifications

• B01D2321/185

  Aeration · CPC title

• B01D2321/04

  Backflushing · CPC title

• B01D61/14 Primary

  Ultrafiltration; Microfiltration · CPC title

• B01F33/403

  for mixing liquids (B01F33/402, B01F33/405, B01F33/406 take precedence) · CPC title

• B01F33/409

  Parts, e.g. diffusion elements; Accessories · CPC title