Re: Pneumatic Conveying Of Bopp "Fluff"
Dear Mr. Bob,
A SLR of 0.6 indicates that the pressure drop is not determined by the presence of material.
(SLR too low to be significant)
Increasing the fan rpm by 10% has the effect:
10% flow increase
21% pressure increase
(fan laws)
Estimating the pressure drop for air only results in:
dynamic pressure drop = 401 mmWC
pipeline pressure drop = 12 mmWC
Bends pressure drop = 120 mmWC
Total line pressure drop = approx. 532 mmWC
Material intake pressure drop = ????
Filter pressure drop = ???
The very light product in combination with an air velocity of approx. 20m/sec indicates a (very) dilute phase pneumatic conveying installation.
Increasing the air flow in a dilute phase installation causes a higher pressure drop, although the effect in your case should be minimum because of the low SLR.
Check:
pressure in surge bin
surge bin filter pressure drop.
pressure increase over fan
pressure at material intake
Pressure/volume curve of fan.
I’m convinced that we are over feeding the pipe line and/or have insufficient material to air separation in our surge bins
Do not overfeed the pipe.
For proper material to air separation, check the can velocity.
(A too high can velocity result in a too high filter pressure drop (or even blocked filter)
Success
Teus ■
Teus
Pneumatic Conveying of BOPP "fluff"
“I assumed that the rotary valve is injecting the material AFTER the fan.
It requires extra calculations, when the material is injected in the inlet of the fan, because then there is also a part vacuum conveying and depending on the fan design, the material is accelerated in the impeller, consuming extra energy.
The advice is to inject after the fan, unless this not possible due to other considerations.
A centrifugal fan curve is in pneumatic conveying not the best solution, as the conveying pressure influences the displaced air volume, which can lead to instable conveying or choking.
Keep in mind that these calculated results are based on assumptions and (educated) guesses.
Take care
Teus”
Hi:
I was reading another informative thread on Pneumatic Conveying when I bumped into this statement by Teus Tuinenburg, from here:
https://forum.bulk-online.com/showthread.php?25595
Centrifugal fans are the way we transport BOPP “fluff” throughout or site. And we do have nuisance blockages.
Allow me to present our process and hopefully I could get some guidance.
1.Biaxially oriented Polypropylene film at approx 0.001” or 100 gage.
2.Scrap film is ground through a 5/16” dia hole screen, creating “fluff” which is 2-20 lb/ft3
3.This material is stored in bunkers which meter the fluff to the process via a trough auger into the negative side of a conveying line, which has a backward incline centrifugal fan
4.The material runs through the fan scroll and is delivered via positive pressure to a surge bin with bin vent or drum filter.
5.The fan is rated at 815 cfm at 32” w.c. SP
6.Line size is 6” sch10S pipe.
7.Altitude is 10 ft above sea level
8.A typical ripe run consists of 115 ft horizontal, 25 ft vertical, (8) 45 deg elbows, (6) 90 deg elbows
9.Pickup velocity 3,886 fpm
10.Desired capacity 2,000 lb/hr
11.Material to air ratio 0.61:1
We have tried to increase fan RPM by 10% and had to back off due to increasing blockages.
I’m convinced that we are over feeding the pipe line and/or have insufficient material to air separation in our surge bins
Any suggestions?
Thanks,
Bob ■