PNEUMATIC POLYETHILENE PELLETS CONVEYING

[schola]

Dear friends:

Pneumatic polyethilene pellet conveying companies often use "Diluted Phase System".

Do you know if "Dense Phase" conveying system is a sound alternative?

Thanks,
schola

 

[quark]

I am not an expert at it but after going through various threads at

http://www.bulk-online.com

I think this is possible. The main problem with dilute phase conveying of PE(as far as I grabbed from above site) is angel hairs and this can be minimized by scoring pipe internal surface. You may get better advise at pneumatic conveying forum of the above site.

 

[DesignerMike]

I am also not an expert, but I have been in a couple plants that use both.

They used dense phase to unload the trucks and move the product to the tops of the silos. I don't think their was any specific gases present in the dense phase system. The product was then dried and "cured" in our equipment under vacuum, and it was discharged into a dilute phase system (which was 100% nitrogen) to move the chips to another storage area and wait for extruding.

quark is correct with the production of "hair" or stringers in the dilute phase system. There is some tweaking required to get proper velocity and proper chips to air ratio in the pipes. You need enough velocity to overcome gravity, but excessive speed causes friction between the chips and piping, which in turn causes them to melt/stick to the piping and "grow hair" while flying through the pipe. One trick as quark mentioned is to score the inside of the pipe especially on elbows (where inertia adds to the friction). This causes the chips to tumble instead of slide...which may in turn cause the corners of the chips to break off and create "dust".

I know much less about the dense phase system. I believe that dense phase can handle a much more vertical run than dilute phase, but I'm not sure.