Air Flow for Dense Phase Conveying System

[Wizard74]

Hi,

I have 2 pellet lines utilizing dense phase positive-pressure conveying systems. Both lines have the same conveying distance.

Line 1:
Products: 95% are surface lubricated
Conveying line geometry: after exiting from RV, the 4" pipeline travels horizontally for 10 metres before making a vertical upward 90deg turn (approx 1m radius)

An approx plan view is below: "O" means out of paper

(RV)xxxxxxO

Air flow rate: 100 m3/hr to maintain conveying pressure of about 1 bar at the air supply side

Line 2:
Products: 50% are surface lubricated
Conveying line geometry: after exiting from RV, the 4" pipeline travels horizontally for 8 metres, then makes a horizontal 90deg turn (approx 1m radius), then travels approx 30cm before making a vertical upward 90deg turn (approx 1m radius). The downstream thereafter is the same as Line 1.

An approx plan view is below: "O" means out of paper

(RV)xxxx
x
x
x
x
O

Air flow rate: 150~200 m3/hr to maintain conveying pressure of about 1 bar at the air supply

My question is: Given the same pellet loading, why does Line 2 need more air flow than Line 1?

I'm trying to rationalize along the factors of
a) Product mix (only 50% surface lubricated in Line 2)
b) Conveying line geometry.

Is this correct and/or are there any other factors that I should look into?
Many thanks.

 

[m777182]

Assuming that the pellets size, shape, bulk density and the smoothness of both pipelines (are they of the same age?)are equal I would look at the dammage of the pellets at the exit side: if there is more dust in the exit air and more crushed pellets in the case of less lubricated material, then the pressure is spent for the comminution work. It is likely that the surface of more lubricated material is more smooth therefore the coefficient of internal friction as well as coefficient of friction between particles and the wall of the pipe is smaller.Inspect the inside of pipes- maybe one is more abraised or even sticky because of a layer of dust.
The additional 90deg turn itself should hardly increase the pressure drop to such extent, but there could be large scales there due to some local back flow in it.
m777182