PET dense phase convey

Posted in: , on 10. Mar. 2003 - 10:11

I have some questions about PET pellet dense phase vonveying as following,I really appreciate your help.


1) The capacity of the conveying system is about 20ton/hr.

2) The horizontal distance is about 60m.

3) The vertical distance is about 30m.

4) The size of the pellet is ? X 4 mm, and normal temperature.

My question is:

1) For dense phase conveying of this pellets, what is the viable velocity?at the velocity,if there will be serious angel hair or bad fragmentation?

2) For dense phase conveying of this pellets,if there is a scope of the viable gas ratio?

If anybody has experience about these, please give me some advice or recommendation.Thanks a lot!

Re: Pet Dense Phase Convey

Posted on 10. Mar. 2003 - 07:43

You should use a pick up velocity in the range of 2 to 3 meters/sec and you should design the conveying line so that the terminal velocity is less than 8 meters/sec. This will almost eliminate fines and streamers.


Amrit Agarwal(Tim)

Pneumatic Conveying Consultants

Visit our web page if you need our help.

Dennis Hauch - Freeport, TX, USA
(not verified)

Pet Conveying

Posted on 11. Mar. 2003 - 04:49


PET pellets, when transferred pneumatically, tend to form streamers and threads which can pose significant processing and quality issues. This degradation phenomenon is influenced by the velocity of the transfer and it is here that dense-phase has a big advantage over dilute-phase.

Dense-phase is synonymous with slow-motion conveying. Comparing dense-phase with that of dilute-phase we are talking 2 – 3 m/s versus 20 m/s at pickup and and 6 – 8 m/s terminal versus 30+ m/s terminal, respectively. These velocities are stated as superficial gas velocities.

Degradation of the PET pellets is reduced an order of magnitude from, nominally, 300 PPM / 100 m in dilute-phase to, nominally, 30 PPM / 100 m in dense-phase. This is documented in the literature.

The solids loading in dense-phase is characteristically higher than that of dilute-phase, say 20 to 40 versus 4 to 6, respectively. The solids loading in either case will be influenced by the length of the system, i.e. the longer the system the lower the loading. The reduced conveying flow in dense-phase can be an advantage if the system is arranged for once-through nitrogen or if the conveying gas must be burned.

I trust this is helpful, please don’t hesitate should you have questions.

Best regards,

Dennis Hauch