The system consists of a feed tank with two air supplies (for fluidization and transport), vertical transport pipe, and a receiving tank. The powder in the feed tank is fluidized to enhance the flowability of the air-solid mixture in the feeding zone. The transport air enters the bottom of the feed tank through a nozzle located below the inlet of the vertical transport pipe. The high velocity air stream entrains the solids and conveys them through the transport pipe into the receiving tank. In industrial applications, vertical air-lifts are typically operated in a continuous mode, with solids being continuously fed into the feed tank to maintain the hydrostatic pressure of the fluidized bed. The higher the hydrostatic pressure the higher the solids entrainment into the transport pipe and consequently, the higher the conveying capacity. Conveying capacities up to 800 tonnes per hour over vertical lifts of more than 100 meters have been achieved in industrial settings.

Some of the advantages of using a vertical air-lift are:

• Dust-free conditions
• Small space requirements
• Small number of moving parts
• Low maintenance
• Trouble-free operation

Equipment

A 4 m high vertical air-lift has been built in the Dept. of POSTEC for the purpose of testing and experimentation. The feed and the receiving tanks have a capacity of about 100 L and the diameter of the transport pipe is around 4 cm.

Research

Our research aims at improving the understanding of the phenomena taking place during the pneumatic transport of solid particles in a vertical air-lift. The effect of operating conditions (fluidization air flow rate, transport air flow rate, nozzle position ΔZ, and height of the fluidized bed) on the conveying capacity, particle velocity, and the pipeline pressure drop is investigated both experimentally and through numerical simulations (e.g., computational fluid dynamics). Different types of materials can be tested to estimate the effect of particle properties (size, density, shape) on their pneumatic conveying characteristics.

References

1. Mathiesen V, Solberg T. Laser-based flow measurements of dilute vertical pneumatic transport. Chem Eng Commun. 2004;191(3).
2. RELPOWFLO IV. Tromsø, Norway: Telemark Technological Research and Development Centre 2008:569-75.