An airlift pump is a pump that has low suction and moderate discharge of liquid and entrained solids. The pump injects compressed air at the bottom of the discharge pipe which is immersed in the liquid. The compressed air mixes with the liquid causing the air-water mixture to be less dense than the rest of the liquid around it and therefore is displaced upwards through the discharge pipe by the surrounding liquid of higher density. Solids may be entrained in the flow and if small enough to fit through the pipe, will be discharged with the rest of the flow at a shallower depth or above the surface. Airlift pumps are widely used in aquaculture to pump, circulate and aerate water in closed, recirculating systems and ponds. Other applications include dredging, underwater archaeology, salvage operations and collection of scientific specimens.

[An airlift pump, powered by compressed air, raises fluid by entraining gas to reduce its density.

1. air supply
2. liquid supply
3. air inlet port
4. air supply line
5. air port
6. air outlet
7. fluid intake
8. riser tube
9. air liquid mixture
10. pump outlet L: liquid, usually wastewater LL: liquid level V: Vessel G: Gravel or solids. | upload.wikimedia.org/wikipedia/commons/f/f5/Airliftpump1.PNG]

Principle

The only energy required is provided by compressed air. This air is usually compressed by a compressor or a blower. The air is injected in the lower part of a pipe that transports a liquid. By buoyancy the air, which has a lower density than the liquid, rises quickly. By fluid pressure, the liquid is taken in the ascendant air flow and moves in the same direction as the air. The calculation of the volume flow of the liquid is possible thanks to the physics of two-phase flow.

Use

Inventor

The first airlift pump is considered to be invented by the German engineer in 1797.

Advantages and disadvantages

Advantages

Disadvantages

Design improvements

A recent (2007) variant called the "geyser pump" can pump with greater suction and less air. It also pumps proportionally to the air flow, permitting use in processes that require varying controlled flows. It arranges to store up the air, and release it in large bubbles that seal to the lift pipe, raising slugs of fluid.

[A geyser pump, an improved airlift pump, powered by compressed air, raises fluid by forcing rising bubbles to displace fluid.

50. air supply
51. air inlet port
52. liquid supply 60,62. air supply lines
53. upper end of air tank 86 66,82. air ports
54. upper air inlet of u-shaped elbow 74 76 air outlet
55. fluid intake
56. riser tube
57. displaced liquid
58. pump outlet L: liquid, usually wastewater LL: liquid level VVV: vessel G: gravel or solids | upload.wikimedia.org/wikipedia/commons/f/f1/geyserpump.PNG]

Sources

Gaslift