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Air Lift Pumps

Air Lift Pumps

(OP)
I am designing an Air Lift Pump: a submerged pipe that has outside source of compressed air introduced in order to raise the working fluid using buoyancy and expansion effects. I have found some technical resources, which have been fairly useful but I was wondering if anyone had any practical experience or some tips for working with these devices.

I know that these devices may not be traditional 'pumps' but I thought this forum would be a good shot at getting opinions.

Thanks to all.

RE: Air Lift Pumps

Simple air-lift pumps have been used for years to provide flow to under-gravel filters.

RE: Air Lift Pumps

For aquariums

RE: Air Lift Pumps

for large size by water well drillers when surging a well
Hydrae

RE: Air Lift Pumps

The biggest application I'm aware is around 100 years old and was for sulfur production in Sulphur, Louisiana.  Here they had huge sulfur domes that were to deep to mine.  After several failed attempts to mine the sulfur, Mr. (Dr.?) Frasch came up with the idea to use steam to melt the sulfur and air to pump it to the surface.  This was a success, Frasch became rich, and plentiful supplies of sulfur were available for wide scale usage where previously it was too expensive.  As a result the United States was able to free itself of the European sulfur cartels and improve everyones standard of living.

RE: Air Lift Pumps

I believe air lifts are commonly used during subsea diving ops to excavate silt from around pipelines and other subsea structures.  A pipe or caisson is held vertically close to the excavation area and compressed air injected a couple of feet up from the pipe inlet. The silt travels up the pipe and is dispersed by the current when it exits the pipe.

RE: Air Lift Pumps

hydrae is correct about wells.
Some of the issues to consider:

The highest efficiency occurs when the total rise from the point of gas/air injection is at least 1 bar or more.  The reason is that as the gas rises its volume increases by a factor of two every 1 bar in depth.  Below 1 bar the amount of air required is quite high to move a little water/fluid.

If the total rise is high, say 3-4 bar, then the process becomes a very efficient, the speed and pressure produced at the top can be quite violent which is why the method is used to purge wells.

This is really a great device, some would consider it a poor man's huge pump.  A little air compressor with about 5 bar depth, and you would need $30,000 pump to equal it.

PUMPDESIGNER

RE: Air Lift Pumps

ChrisConley,

I've used this principle a couple of times, and I found the design and implementation to be "interesting" (and a bit of fun).  You can find much useful information in older editions of "Marks Mechanical Engineer's Handbooks."  The design parameters are best considered as being only very general guides.  Plan on some experimentation, and allow for flexibility in your design.

Best performance is realized when the initial bubble size is as small as practical.  Don't just let the air simply come out of the end of a pipe.  Install some provisions to assure that the air flows from many small ports in a manner that does not encourage the bubbles to merge together.

Be sure to include provisions to permit reasonably fine adjustment of the air flow rate.  For a specific operating condition, there will be an optimum air flow rate.  Increasing air flow beyond a particular rate will result in a decrease in the product flow rate.

RE: Air Lift Pumps

So is Sulphur LA named after Sulfur?

RE: Air Lift Pumps

Sulphur is how the English spell sulfur so probably.

RE: Air Lift Pumps

ChrisConley,

I'm working on a similar project now. Do you have any good references for finding suitable description of the technology in question? I'm thinking of design criteria for the air compressor, capacities, dimensioning etc.

RE: Air Lift Pumps

Hi All, I'm looking at these as well for slurry extraction from CIL tanks in a gold plant.

Anyone know of a anufacturer with experience in Australia I could talk to? Major problem is how much head these pumps will supply. I need to pump about 70-90m3/hr 4-6m vertical with a 3-4m submurged pipe ....

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RE: Air Lift Pumps

General Engineering Handbook, C.E. O'Rourke editor in chief, about 1940, has a good explanation of the principle.
Actually made a small one for a brine mix tank a couple of years ago, out of 2" pipe and some fittings. Worked pretty well until it got down near the air nozzle. Would have installed permanently except it put to much air in the brine. Siiigh.

RE: Air Lift Pumps

As with Chris, it is not the principle nor the equations which are my issue- I need practical experience in using these things to pump a high solids laden slurry, and what type of lift to submergence ratio I would need to pump 4-6m (That is 13.1-19.7ft for those of you living in the dark ages ;) )in the air.

What pitfalls / problems might I encounter? It seems a lot of people can point to the theory, but from reading a lot of references, I can't see much practical experience?

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RE: Air Lift Pumps

This principle has been used for many year in my industry (water well drilling) We use it to clean holes as they are drilled and to rehab wells.  The best reference with charts, tables, and submergence info is Gound water and wells by Driscoll.  I have personally used this for both reasons.  My only concern would be the I have only used this priciple with water with a high sand content and a specific of around 1.2.  I would be a little concerned about the weight of the slurry.  If you want the book you can order it at www.ngwa.org

RE: Air Lift Pumps

Air lift pumps are not recommended for pumping fluids with solids concentrations greater than 10% by weight and certainly are not advisable for horizontal runs. The minimum angle from horizontal is something like 60° but this is based on allot of things.  

Ideally, you want to pump straight up to a break pot.

Lift Height is the distance from the liquid level being pumped to the break pot, Submergence is the distance from the liquid level down to the air tap. An air lift works best when this ratio is 50%. The ratio can be increased by installing an air jet on the break pot to draw a siphon and increase the submergence.

Air lifts are used in areas of high contamination for sampling purposes and sometimes for liquid transfer. Areas where no moving parts are recommended. A 1/2 air lift will use about 1 scfm and pump 1 fps liquid. So don't get exited about doing this with solids which may have a minimum carrying velocity.

RE: Air Lift Pumps

Excellent, thanks thewellguy and mechprocess! The principle has been used before for similar slurries, however in this case, we are installing intertank carbon advance scvreens, which increases the height of the lift by about 2.5-3m. We are somewhat limited in hieght and depth we can submerge, so we are thinking this will probably be best left to an expert vendor to design.

Does anyone have any advice as to vendors who construct such airlifts in Australia?

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