What Is an Air Lift Pump?

An Air Lift Pump is a type of pump that uses compressed air to move fluids, typically water or slurry, from one location to another. It operates by injecting air into a vertical pipe submerged in the fluid, creating a mixture of air and liquid. The introduction of air reduces the density of the fluid in the pipe, causing it to rise due to the buoyant force.

Air lift pumps are simple, have no moving mechanical parts submerged in the fluid, and are commonly used in applications such as wastewater treatment, aquaculture, and mining. They are especially useful in situations where clogging and wear from solid particles could be a concern for other pump types.

Parts of Air Lift Pump:

An air lift pump consists of several key parts, each playing a crucial role in its operation:

1. Air Compressor: Supplies compressed air to the system, which is injected into the riser pipe to create the air-liquid mixture.
2. Air Injection Pipe: A pipe through which compressed air is introduced into the system, typically near the bottom of the riser pipe.
3. Riser Pipe (Lift Pipe): A vertical pipe through which the air-liquid mixture rises. The reduction in fluid density in the riser pipe causes the fluid to lift upward.
4. Fluid Inlet (Suction Pipe): Located at the bottom of the riser pipe, this allows the liquid (e.g., water or slurry) to enter the system and mix with the injected air.
5. Discharge Outlet: The point at the top of the riser pipe where the lifted fluid exits after being pumped upward by the air pressure.
6. Air-Water Separator: An optional component used to separate the air from the lifted liquid before discharging it.

Working Principle of Air Lift Pump:

The working principle of an air lift pump is based on the buoyancy effect created by the introduction of compressed air into a column of fluid, causing the fluid to rise. Here's how it works:

1. Compressed Air Injection: Compressed air is introduced into the bottom of a vertical riser pipe that is submerged in the fluid to be pumped.
2. Formation of Air-Liquid Mixture: The air mixes with the fluid, forming air bubbles. This mixture of air and fluid has a lower density than the surrounding fluid.
3. Reduction in Density: The reduced density inside the riser pipe creates a buoyant force, causing the air-liquid mixture to rise through the pipe.
4. Lifting of the Fluid: As the air bubbles rise, they carry the surrounding fluid with them, effectively "lifting" the fluid up the riser pipe.
5. Discharge: Once the fluid reaches the top of the riser pipe, it is discharged through the outlet, while the air bubbles escape or are separated from the fluid.