Airflow required to move frac sand

[zereko]

G,Day!

I would like to drop frac sand into a charged pipeline, via dropping into it by having a couple of "drops" using knife gate valves to create an airlock. I would like to move aproximately 40 tons per hour. What air flow (vol & psi) would be required to achive this? Frac sand has a bulk density of 95 - 100 lbs per ft3 Thanks! There is a 230 CFM @ 100 PSI compressor readily available...would this do the trick?

P.S. Pipeline length is 100 feet and elevation change of about 25 feet.

 

[Latexman]

I strongly suggest farming this out to someone that has experience in the art/science of solids handling.



Good luck,
Latexman

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[LittleInch]

The issue really is one of velocity from what I can see - You probaly need something in the region of 30 to 50 ft/sec to avoid getting a blockage and also something more like a screw feeding sand in continuously rather than just dumping it in "lumps" which is what you sound like you're thinking off. A very quick set of numbers based on sand to air volume ratio of 1:50 on the basis that you're blowing into a pipe with an open end at the far end and your 235 cfm is based on that volume flow at 100 psi, then you might be Ok, providing you size your pipe right - 8" to 10" sounds about right. You might need an eductor to get the required air flow. All pretty much stab in the dark stuff.

Clearly sand in air at that velocity is going to create a hell of an erosional issue (Prob need to use PE or UHMWPE) as the pipe or as a liner, and alos a lot of dust once some of the sand lands on the ground about 20m from the end of the pipe.

Are you just trying to create a hill of sand from a delivery point or is there more to this? Can't help feeling this isn't the right way to do it....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[ccfowler]

I agree with LittleInch! Dilute phase pneumatic conveying works very well, but it is most commonly chosen for reasons other than minimizing operating costs. Something beyond the conveying process usually controls the economics of the pneumatic conveying process. Compressed air is a very expensive energy form.

Dense phase pneumatic conveying may provide a much better option, but first, I would want to look carefully at other conventional options such as enclosed or partially enclosed belt conveying.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[zereko]

Thanks to all for the feedback! And yes Latexman, until I read that it was a no no to look to hire a hand on here as that was my original intention for coming.

CCFowler the reasoning is more portability, quick set-up (easier to run a hose than a conveyor in such temporary circumstances) and simple. The cost of air would not affect overall cost too much because of the short term that its used and the expensive trade off for time in mobility and set-up. This is being investigated by me to be used in conjunction with conventional conveyor that would load the hopper from a truck in the first place (Convey-all truck unloader : see [URL unfurl="true"]http://convey-all.com/wp-content/uploads/2012/11/Drive-Over-Conveyor-Dimensions.pdf[/url]) -the hopper and pipe/abrasive material hose set-up would go from there into silos and portable piping would make filing different hoppers a very fast change from one to another they are about 100 feet away from the truck unloading zone and 25 - 30 feet high (closed silos-filtered air to escape) Silo hodge podge positions make that long length conveyor difficult/time consume set-ups!

LittleInch I was thinking of necking down some after the gate valve so that the sand flows in more uniform than that of a "lump" and this is coupled with a vent for that area between the gate valves to exhaust the anticipated pressure in there after being emptied and connected to the "pressure pipe" while being emptied and also to perhaps help fill by venting when the top gate is open allowing the sand in. I am comsidering a rotary valve vs knife gates so any comments/knowledge about this would be greatly appreciated! A couple of these gate-valve/feed-pipes are envisoned perhaps 1- 1.5 cu/ft each.

I make the PV500 vacuum system (IVAC)see: industrialvacuumunit.com for info and videos and it works excellent in a large range of materials, rock, sand, gravel, sludge, water, but since we have gravity in this situation- the vacuum part isn't needed here.

In sludge the IVAC fills a 6 yard bucket in 5 mins. I am looking for advice on air required and possible different solutions for this new task..... LittleInch you believe that the 230 CFM is enough and wondering if there is a formula or way to tell us what flow that will generate? The air is not a show stopper because if more is needed so be it, but wondering if 230cfm will do it as that is readily available and makes things a bit easier! The reason for the 40 tph is that they don't want to tie up the truck too long when unloading itself so a few mins either way won't be a killer either. Due to this ideas simplicity one person (the truck driver) should be able to run the entire system by him/herself. (will trade air cost for that!)

Thanks again y'all as I truly appreciate your input!

 

[ccfowler]

zereko, your more fully described system proves my point that something outside the conveying process normally controls the choice to use dilute phase pneumatic conveying, and under the circumstances you describe, I would choose dilute phase pneumatic conveying almost certainly.

Due to the near certainty of clogging problems, I would avoid the slug feeding that you are considering. I would use a rotary feeder, but I would thoroughly investigate available options for materials and coatings to deal with the abrasiveness of the sand.

At the discharge end, I would first want to consider a combination of a centrifugal separator and bag filter to minimize dust problems.

Despite it's long successful history, dilute phase pneumatic conveying remains more art than science in its successful practical application. Equipment manufacturers may be able to be much more helpful if you can supply a good representative sample of the actual material that you will be handling. Also, depending on the material, humidity can play a surprisingly important role in variations of system performance due to changes in the flowing properties of the material due to agglomeration, bridging, etc. at differing humidity levels.

Adequate after-cooling and moisture removal from the air leaving your compressor system could play a very important role in the success of your system. I am not suggesting that fancy air drying will be needed, but all due practical minimizing of moisture in the compressed air supply will probably prove to be wise.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[LittleInch]

This is a common method of feed delivery on farms. Look up poderbulk.com or search pneumatic bulk bloeer delivery.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way