Clarification of Suspensions

• US 20100314324A1
• Filed: 06/16/2009
• Published: 12/16/2010
• Est. Priority Date: 06/16/2009
• Status: Active Grant

• Current Assignee: Aurora Algae, Incorporated (Reliance Industries Limited)
• Original Assignee: Aurora Algae, Incorporated (Reliance Industries Limited)
• Inventors: Radaelli, Guido, Rice, David, Parsheh, Mehran, Smith, Jordan
• Granted Patent: US 9,101,942 B2
• Time in Patent Office: Days
• US Class Current: 210/706
• CPC Class Codes: A01H 13/00 Algae unicellular algae C12N1/12
• CPC Class Codes: B03D 1/028 Control and monitoring of flotation processes; computer models therefor
• CPC Class Codes: B03D 1/1431 Dissolved air flotation machines
• CPC Class Codes: B03D 1/24 Pneumatic mixing gases or vapours with liquids B01F23/20
• CPC Class Codes: C12N 1/12 Unicellular algae; Culture media therefor as new plants A01H13/00
• CPC Class Codes: Y02W 10/37 using solar energy

Abstract

A clarification system may comprise a channel having an inlet and an outlet, a length, bottom, and a height sufficient to contain a liquid having a depth. The clarification system may include one or more gas injectors disposed within the channel, configured to inject gas bubbles into a suspension flowing in the channel. In some embodiments, at least one gas injector injects gas bubbles having average or median size that does not exceed 100 microns in diameter. Some gas injectors inject bubbles having mean size below 50 microns. Some gas injectors inject gas via the precipitation of gas bubbles from a supersaturated liquid including a dissolved gas. Certain embodiments may be configured to form a quiet zone, typically near the top of the flowing suspension, in which turbulence may be minimized or substantially eliminated. Certain systems include a plurality of gas injectors disposed at different lengths along the channel.

Claims

1. A clarification system comprising:

a channel having an inlet, an outlet, a length, a bottom, and a height sufficient to contain a liquid having a depth;

one or more gas injectors disposed within the channel between the inlet and outlet and configured to inject gas bubbles having a mean size that does not exceed 100 microns in diameter into a liquid flowing in the channel from the inlet to the outlet.

2. The clarification system of claim 1, wherein at least one gas injector is configured to inject gas bubbles having a mean size below 50 microns in diameter.

3. The clarification system of claim 1, further comprising two or more gas injectors disposed at different distances along the length.

4. The clarification system of claim 1, wherein any gas injector is disposed a distance from the bottom less than 25% of the height.

5. The clarification system of claim 1, wherein any gas injector is configured to inject gas bubbles by precipitating gas bubbles from a supersaturated liquid solution.

6. The clarification system of claim 1, wherein any gas injector is configured to inject gas bubbles in a downward and downstream direction with respect to the inlet and outlet.

7. The clarification system of claim 1, further comprising a scavenger injector disposed upstream of the outlet and configured to inject gas bubbles into a liquid flowing from the inlet to the outlet.

8. The clarification system of claim 7, wherein the gas bubbles injected by the scavenger injector have a mean size that does not exceed 40 microns in diameter.

9. The clarification system of claim 7, wherein the gas bubbles injected by the scavenger injector are injected in an upstream and downward direction with respect to the inlet and outlet.

10. A clarification system comprising:

a channel having an inlet, an outlet, a length, a bottom, and a height sufficient to contain a liquid having a depth;

a plurality of gas injectors disposed in the channel between the inlet and outlet at different distances along the length and configured to inject gas bubbles into a liquid flowing from the inlet to the outlet.

11. The clarification system of claim 10, wherein a first gas injector disposed a first distance from the inlet injects gas bubbles having a first average diameter, and a second gas injector disposed a second distance from the inlet injects gas bubbles having a second average diameter.

12. The clarification system of claim 11, wherein the second distance is greater than the first distance.

13. The clarification system of claim 11, wherein the second average diameter is less than the first average diameter.

14. The clarification system of claim 11, wherein the gas bubbles injected by the first gas injector have a mean size that does not exceed 100 microns.

15. The clarification system of claim 14, wherein the gas bubbles injected by the second gas injector have a mean size that does not exceed 40 microns.

16. The clarification system of claim 10, wherein 90% of the injected gas bubbles do not exceed 100 microns in diameter.

17. The clarification system of claim 10, further comprising a scavenger injector disposed upstream of the outlet and configured to inject gas bubbles into a liquid flowing from the inlet to the outlet.

18. The clarification system of claim 10, wherein the gas bubbles injected by the scavenger injector have a mean size that does not exceed 40 microns in diameter.

19. The clarification system of claim 10, wherein the gas bubbles injected by the scavenger injector are injected in an upstream and downward direction with respect to the inlet and outlet.

20. A method for clarifying a suspension comprising a liquid and a suspended phase, the method comprising:

providing a clarification system including;

a channel having an inlet, an outlet, a length, and a bottom, and

one or more gas injectors disposed within the channel between the inlet and outlet and configured to inject gas bubbles into the suspension;

causing the suspension to flow through the clarification system from the inlet to the outlet at a depth and a flow rate resulting in laminar flow in at least a top layer of the suspension;

injecting gas bubbles into the suspension using the gas injectors under injection conditions that result in segregation of the suspended phase within the top layer and do not induce turbulence in the top layer; and

removing the liquid at the outlet.

21. The method of claim 20, wherein injecting includes precipitating the gas bubbles from a supersaturated solution comprising the liquid.

22. The method of claim 20, wherein the gas bubbles have a mean size that does not exceed 100 microns.

23. The method of claim 20, wherein the top layer includes a top 10% of the suspension as measured from the bottom.

24. The method of claim 20, wherein the dominant transport mechanism of the gas bubbles in the top layer is Stokes-limited flow.

25. The method of claim 20, further comprising removing the segregated suspended phase.

26. The method of claim 20, wherein the suspended phase includes one or more algae.

27. The method of claim 26, wherein any of the algae is a member of the genus Nannochloropsis.

28. The method of claim 20, wherein the liquid includes water.

29. The method of claim 20, wherein the liquid has a salinity between 1 and 75 parts per thousand.

30. The method of claim 20, further comprising adding a flocculant to the suspension prior to causing the suspension to flow through the clarification system.

31. The method of claim 30, wherein the flocculant includes a metal-sulfate.

32. The method of claim 30, wherein flocculant is added in an amount that does not exceed 10 mg of dissolved metal per liter of suspension.

33. The method of claim 20, wherein a ratio of volume of injected gas bubbles to volume of suspended phase does not exceed 0.02:

1.

34. The method of claim 33, wherein the ratio does not exceed 0.002:

1.

35. The method of claim 20, wherein the clarification system includes a scavenger injector disposed proximate to and upstream of the outlet and configured to inject gas bubbles into a liquid flowing from the inlet to the outlet.

36. The method of claim 35, wherein the gas bubbles injected by the scavenger injector have a mean size that does not exceed 40 microns in diameter.

37. The method of claim 35, wherein the gas bubbles injected by the scavenger injector are injected in an upstream and downward direction with respect to the inlet and outlet.

38. The method of claim 20, wherein the liquid has a pH between 4 and 12.

39. The method of claim 20, wherein the suspension is flocculated into flocs having an average size below 50 microns.

40. The method of claim 20, wherein the injected gas bubbles have a rise rate through the liquid that does not exceed 3 cm/second.

41. A method for clarifying a suspension comprising a liquid and a suspended phase, the method comprising:

providing a clarification system including;

a channel having an inlet, an outlet, a length, and a bottom, and

one or more of gas injectors disposed within the channel between the inlet and outlet at different distances along the length and configured to inject gas bubbles into the suspension;

causing the suspension to flow through the clarification system from the inlet to the outlet;

injecting gas bubbles having a mean size that does not exceed 100 microns in size into the suspension using the gas injectors; and

removing the liquid at the outlet.

42. The method of claim 41, wherein injecting gas bubbles comprising injecting a first mean size of the gas bubbles from a first gas injector and a second mean size the gas bubbles from a second gas injector.

43. The method of claim 42, wherein the gas bubbles injected by the first gas injector have a mean size that does not exceed 100 microns in diameter, and the gas bubbles injected by the second gas injector have a mean size that does not exceed 40 microns in diameter.

44. The method of claim 41, wherein the clarification system further comprises a scavenger injector disposed upstream of the outlet and configured to inject gas bubbles into a liquid flowing from the inlet to the outlet.

45. The method of claim 44, wherein the gas bubbles injected by the scavenger injector have a mean size that does not exceed 40 microns in diameter.

46. The method of claim 44, wherein the gas bubbles injected by the scavenger injector are injected in an upstream and downward direction with respect to the inlet and outlet.

47. The method of claim 41, wherein any of the gas injectors injects gas bubbles by precipitating the gas bubbles from a supersaturated solution comprising the liquid.

48. The method of claim 41, wherein any of the gas injectors injects gas bubbles in a downstream and downward direction with respect to a flow of the suspension through the clarification system.

49. The method of claim 41, wherein the liquid has a pH between 4 and 12.

50. The method of claim 41, wherein the suspension is flocculated into flocs having an average size below 50 microns.

51. The method of claim 41, wherein the injected gas bubbles have a rise rate through the liquid that does not exceed 10 cm/second.

52. A method for clarifying a suspension comprising a liquid and a suspended phase, the method comprising:

providing a clarification system including;

a channel having an inlet, an outlet, a length, and a bottom, and

a plurality of gas injectors disposed within the channel between the inlet and outlet at different distances along the length and configured to inject gas bubbles into the suspension;

causing the suspension to flow through the clarification system from the inlet to the outlet at a depth and a flow rate resulting in laminar flow in at least a top layer of the suspension;

injecting gas bubbles into the suspension using the gas injectors under injection conditions that result in segregation of the suspended phase within the top layer and do not induce turbulence in the top layer; and

removing the liquid at the outlet.

53. The method of claim 52, wherein injecting gas bubbles comprising injecting a first mean size of the gas bubbles from a first gas injector and a second mean size the gas bubbles from a second gas injector.

54. The method of claim 53, wherein the gas bubbles injected by the first gas injector have a mean size that does not exceed 100 microns in diameter, and the gas bubbles injected by the second gas injector have a mean size that does not exceed 40 microns in diameter.

55. The method of claim 52, wherein the clarification system further comprises a scavenger injector disposed upstream of the outlet and configured to inject gas bubbles into a liquid flowing from the inlet to the outlet.

56. The method of claim 55, wherein the gas bubbles injected by the scavenger injector have a mean size that does not exceed 40 microns in diameter.

57. The method of claim 55, wherein the gas bubbles injected by the scavenger injector are injected in an upstream and downward direction with respect to the inlet and outlet.

58. The method of claim 52, wherein any of the gas injectors injects gas bubbles by precipitating the gas bubbles from a supersaturated solution comprising the liquid.

59. The method of claim 52, wherein any of the gas injectors injects gas bubbles in a downstream and downward direction with respect to a flow of the suspension through the clarification system.

60. The method of claim 52, wherein the liquid has a pH between 4 and 12.

61. The method of claim 52, wherein the suspension is flocculated into flocs having an average size below 50 microns.

62. The method of claim 52, wherein the injected gas bubbles have a mean rise rate through the liquid that does not exceed 1 cm/second.

63. The method of claim 52, wherein the injected gas bubbles have a median rise rate through the liquid that does not exceed 10 cm/second.