Slurry Gravity Flow Pipeline 3

[msii]

Hi Guys,

I'm new in pipe sizing and want to know what slope and diameter of pipeline I should use to avoid settling of slurries in pipeline. Top side of the line is connected to a tank with shallow height of slurry (no pressure is imposed) and the bottom line is going to a storage tank. I went through some papers and handbooks but they are a bit confusing for me.
According to Manning Equation Vf= 0.590* d^(2/3)* S^(1/2) /n which it is for full flow volume. How I can find my flow is full flow volume and not partially filled pipeline. If so, what formulation I should use and how I can calculate Hydraulic diameter?

Thanks so much in advance,

Regards

 

[LittleInch]

I'm sure there are man posts here but my starter would be that slurry design is defiantly more art than science.

"Slurry" is such a variable thing that you need to understand what is in your slurry, SG of the mix, particle sizes, water content, plasticity etc etc. slurry can everything from dirty water to something the consistency of toothpaste ~(with or without rocks in it).

At a very basic level to avoid settlement I would aim for a min of 1m/sec and possibly higher .

Once you know your volumetric flow then this gives you an approximate pipe size based on that flow rate.

Then you can estimate your pressure drop. If this is more than your height difference then you're into partial channel flow.

Needs some real details here to follow up.

https://www.eng-tips.com/viewthread.cfm?qid=129995

https://www.eng-tips.com/viewthread.cfm?qid=152275

https://www.eng-tips.com/viewthread.cfm?qid=142556

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

 

[MikeHalloran]

The only slurry system in which I have been involved had a recirculating loop (and a recirculating pump to drive the loop) everywhere it went, because that particular slurry would settle out very quickly on nearing zero velocity.

The energy and money 'wasted' by keeping the slurry always in motion, or of flushing the system when not in use, should be easily dwarfed by the cost of opening or disassembling parts of the system and manually rodding out the settled and accreted solids and restoring the system to operational status.

Based on other experiences disassembling clogged drain lines in a chemical plant in high latitude winter, I suggest at least using crosses and plugs instead of elbows, everywhere, despite a nominal higher pressure drop, just to avoid the expense of disassembling pipes from elbows for cleaning or de-clogging.



Mike Halloran
Stratford, CT, USA

 

[SandCounter]

I am not clear on your formula because the variables are not defined. I am also not clear on whether you have a full pipe or not. In general, the ability to move solids in slurry is based on velocity. If you know your D85 particle size and SG, you can use the nomograph on pdf page 18 of 38 of the below link to determine minimum carrying velocity.

https://ocw.tudelft.nl/wp-content/uploads/F._oe4625_Chapter04.pdf

From there, whether you're sluicing or running full pipe, you can adjust your inputs into your equation to get the velocity you need to move your slurry.

I used to count sand. Now I don't count at all.

 

[LittleInch]

That's a great link and nice document to have saved away. Thanks.

LI

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

 

[msii]

Hi SandCounter,

Thanks for the link. How can I find my flow is full pipe or not? How can I find with following data my slurry will flow through pipe full pipe with low speed or partially filled with higher speed. If speed is higher and partially filled pipe the sediments would be less.
S.G. of solid (limestone): 2.7
Concentration w/w: 70
Flow rate (m3/hr): 10
particle size P50: 150-500 microns
Pipe selected DN150 for gravity line.

Thanks
Mosi

 

[LittleInch]

Well that works out in full pipe to be 0.16m/sec

I suspect that is too slow so you will need to run at partial full in order to get the velocity up.

For speed required calculation you need to read and follow the excellent guide provided to you for free...

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

 

[SandCounter]

Sediment will deposit in the pipe until there is enough restriction to increase the velocity until it carries all particles. You can set it up as an equation but it is indeterminent. You can, however iterate to get close to the right answer. Figure out the required velocity for your D85. (Use D85 because if you use D50, half your material will fall out. At D85 85% of the material will help move the remaining 15%.) Figure out the area to match the velocity. Calculate the depth the pipe would fill to leave that area. Make sure the remaining open dimensions comfortably exceed the max particle diameter.

I used to count sand. Now I don't count at all.

 

[cvg]

this is a gravity system. you need to iterate to find the flow depth in the pipe. given the low flow rate it is likely that sediment deposition will fill the pipe, plug it and will cause overflow. you cannot increase the velocity easily in a gravity system. you would need more head and steeper pipe which may be difficult to achieve. tailings slurry is often designed to flow much faster to avoid settling and this generally requires pumping