Air lift pump in Cement plants
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Principle of air-lift pump (mammoth pump)
Pressures on the tube inlet must be the same (outside – WW, inside – mixture):
where HMIX = HTRANSPORT and pressure (head) loss DpPLMIX can be
included in HTRANSPORT it is for ex. in H´TRANSPORT
For given HWW, rWW, rSLUDGE, H´TRAN and MMIX or MSLUDGE we can set rMIX and from it needed amount of air MAIR or VAIR (see example below).
Given data: MSLUDGE = 2000 kg/h, rSLUDGE = 1200 kg/m3, rWW = 1000 kg/m3,
rAIR = 1,2 kg/m3, HWW = 3 m and H´TRAN = 6 m.
rMIX = (HWW*rWW) / (H´TRAN) = 3*1000 / 6 = 500 kg/m3 VSLUDGE = MSL / rSL
rMIX = (VSLUDGE*rSLUDGE + VAIR*rAIR) / (VSLUDGE + VAIR) VSLUDGE =2000/1200
rMIX = (2000 + VAIR*1,2) / (1,67 + VAIR) = 500 VSLUDGE = 1,67 m3/h
From the equation we can set: VAIR = 2,34 m3/h or MAIR = 2,81 kg/h.
Tube diameter (mixture speed) depends on settling velocity of sludge or sand particles.
An air lift pump is a simple pump used to pump water by mean of compressed air.
This pump is considered to be invented by the German engineer Carl E. Loescher, who lived in the second part of the eighteenth century. He discovered the airlift pump in1797.
The only energy required is 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. It usually bubbles into another larger diameter pipe. By gravitation the air, which has a lower density than the liquid, rises quickly. By inertia, 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 under the physics of two way flow.
Airlift pump technology is superb due to its simple structure but along with its simple structure it has some problems along with simplicity. It has a weak structure its flow is also slow, irregular and disturbed its suction is also weak. It can be used for low lifts only due to weak suction.
The following paragraph exposes the advantages and disadvantages of the airlift pump compared to other pumping techniques.
the very simple principle is a clear advantage. Only air with a higher pressure than the liquid is required.
the liquid is not in contact with any mechanical elements. Therefore, neither the pump can be abraded (which is important for sandwater wells), neither the contents in the pipe can be abraded (which is important for archeological research in the see)
cost: while in some specific case the operational cost can be interesting, most of the time, the quantity of air to compress is high compared to the liquid flow required.
This pumping system is suitable only if the head is relatively low. If you want to obtain a high head, you have to chose a conventional pumping system.
Because of the principle, a lot of air reminds in the liquid. In certain case, this can be problematic, as, for example, in a waste water treatment plant, before an anaerobic basin.
Nowadays geyser pumps are also used along with these pumps.