Vertical Slurry Pipelines 6

[ECD40]

We are planning to pump solids in a slurry form from a deep underground mine. The slurry particles will have a top size of 4.5 mm and a bottom size of -300 mesh. A laboratory test will be restricted to using a 2 inch diameter vertical pipe and centrifugal pump with a maximum lift of 50 feet. The fluid will be saturated brine and the solids will be a mineral that would dissolve in water, but not in the brine. A full scale plant would be using an 8" or 10" diameter pipe to convey the slurry vertically. The vertical lift height for the production plant will be 1,000 meters using positive displacement pumps for the high pressures involved. The specific gravity of the slurry will be 1.64.
Does anyone have any knowledge of scaling up from the laboratory to a full scale plant in a vertical lift hydraulic application? I've looked for empirical relations for scaling-up, but find none. As far as I can tell, this pumping application has not been done before.

 

[Artisi]

Pierre, an excellent reference book, I actually worked with the guys that put it all together and refined it into something useful.
However, for this particular posting, the OP, is talking about transporting slurry vertically, this is a different approach to transport horizontally, plus the SG advised would seem to indicate it could be verging on plug flow, again a different approach.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[pierreick]

Hi Artisi,
Agree about your comments, my point was about the characterization of slurry and behavior in pipe .
In other words I don't think this project (1000 m underground) can happen with this type of technology .
Cheers,
Pierre

 

[Nutzman]

Good day all,
There is certainly a lot of good input here. I have done many slurry tailings projects in my day. But all typically "rising main" Horizontal.
1000m vertical. with water is 100 bar. Then add in the SG? There's a couple "triplex" type PD pumps that could entertain those pressures. In a 8 inch line at 2 m/s and a 55% efficiency pump, you going to need 1868 kW. You going to need some serious cable going down the shaft to feed that motor. Is this going to be a duty standby unit?
What I have done in the past in vertical lift type situations is to pump up to "old worked out levels". At those levels you build a wall and pump the slurry behind the wall. The next lot of pumps at that level, then pick up the slurry and pump it up to the next level. That way you have staged pumping and able to clear piping in the event of blockages. Agreed more pumps, but smaller motors. I don't know if the mine is a 1000m one drop to the "ore body".
I know a company in Cape Town South Africa that specialise in slurry transportation. They have branches all over, so may be close to site and able to offer some "closer" assistance.

 

[LittleInch]

ECD40,

Looks like you're going to have to try it and see.

I still like the air lift idea, but you may need to step the diameters up as you go up.

But have you reached out to any local or national universities or colleges doing mining courses? They can often provide good test facilities, sharp minds and sometimes free labour to do the testing.

I do struggle to see 1000m on one pipe and one lift, but you never know.

At 4.5mm largest grain size, you might not have the issue over clogging that you think. Maybe this is also where you can run a second line with either water injection to dilute it or add a bit of gas to break it up when it stops flowing.

Be sure to let us know what happens - respect the input you've received, even if it wasn't what you wanted....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ECD40]

Hello All,
Firstly, let me assure MM and everyone, that I had nothing to do with any deleted postings. I am appreciating all of the comments and replying as best that I can. This project is moving forward, albeit slowly as there is much at stake and its complicated.
The 1,000 meter lift cannot be broken up into stages as there are no intermediate levels in the mine. A small scale test at a lab is being bypassed, as the mine already has an operating processing plant and much is known about the behavior of the slurry in small pipes (like 2" diameter). The next step will be to go to a pilot plant using a 4" diameter vertical pipe, which the labs cannot provide, so it will be constructed at the minesite. There are 3 major suppliers of PD pumps, all of which claim to be able to pump a slurry 1,000 m with an SG of 1.64 with no problem.
So I come back to the original issue of scaling up from one size of equipment to a larger size of equipment with confidence. Maybe it's all a matter of trial and error (try it and see), but the stakes are very high. The CAPEX for a production size slurry handling plant will be about $500 million.
I welcome all comments, but it may take several days before I respond.
Thanks to you all,
ECD40

 

[PersonalProfile]

I cannot directly assist, though the following may be of interest:

Underground mineral processing – Gekko Systems modular Python

https://papers.acg.uwa.edu.au/p/1710_51_Bell/

 

[LittleInch]

A long time ago I looked at pumping a peat slurry / mix and ran into similar problems of it not being done before and issues over compaction etc

One thing you could try and experiment with is an idea which has been used before apparently where you inject in several small nozzles around the pipe a continuous "ring" or outer column of water to lubricate the passage of the slurry.

Also look carefully at the inner joint on your pipe to remove any weld burrs - might be difficult on a small pipe, but maybe insert a PE liner?

Lots of options to study in your experimental set up.

Also maybe look at inserting plugs of water / brine every approx 100m of slurry insert a plug of 10m of brine?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[miningman]

Ah here we go again.!!! The underground mining industry was playing with air lift systems about 80 years ago , with rather mixed results I might add. To put this into context, imagine a column of clean water , 3000 feet in height. A column of water only 100 feet high has a pressure at the base of 41.666 psi. So a column 3000 feet has a pressure of 1250 psi, and this totally ignores any necessary extra frictional losses when pumping due to a SG in excess of unity. So this represents the minimum air pressure required to achieve airflow in the correct direction......anything less results in water flowing backwards into the compressed air system. Some of my old engineering text books go into this in some depth......no pun intended........ and from memory , the optimum location for air injection is represented at a degree of submergence of 60%.

Way early in my career , a so called experienced mine manager decided to overcome a local pumping problem by introducing compressed air into the discharge line approx 300 feet below the discharge elevation. He failed to do the necessary calculation and / or ensure that the compressor discharge pressure was in excess of 125 psi. End result was a totally frozen discharge line. Remember your basic thermodynamics that when allowed to expand , a compressed gas will drop in temperature due to adiabatic flow conditions.

I cant do the necessary theoretical calculations , but imagine 1250 psi compressed air expanding under similiar adiabatic conditions