I concurr-

I ALSO TRIED THIS WITH SPONGE IRON PELLETS 1/2 INCH AND LESS, PARTICLE DENSITY 3.4 AND IRON ORE PELLETS .

15,30 45 DEGREES INCLINATION.

dON'T DO IT IF YO CAN , IF THERE IS ANY 0,90 ALTERNATIVE ROUTE USE THAT.

MARCO ■

It is a general rule of thumb for lean phase conveying to stick

to horizontal or vertical routes. In inclined pipes the particle

wall collisions increase substantially which lowers the

particle velocity and the particles doesn’t get a chance to

reaccelerate. If the inclines is not very long then it works but

at higher pressure drops (not recommended though). If the inclined

is long then the particle velocity does fall below the chocking

velocity in vertical sections and blockages occurs.

The gravitational effect is on the pressure drop which increases

in the vertical sections between 2-6 times depending on the

suspension density, velocity and material properties. ■

The minimum conveying air velocity for vertically upward flow is lower than that for horizontal conveying, and this will help reduce the pressure gradient for vertically up flow, if you can make use of the fact. The minimum conveying air velocity for a vertically upward sloping line, however, is higher than that for horizontal flow, and so the pressure drop for an upward slope can be greater than that for a vertically upward line. You need to work out the velocity profile throughout the length of your total pipeline, particularly if you step the pipeline to a larger diameter part way along. ■

Dear cacing,

Keeping pneumatic conveying lines as straight as possible is correct, as bends cause a product velocity drop and thereby pressure drop for reacceleration.

The theory that slope conveying is to be avoided is based on the fact that particles are dropping out of the flow and fall down the slope (more or less fluidized) underneath the air flow.

In a vertical air flow, this is not possible.

Particles leaving the main air flow to the wall, will be introduced to the air flow, while falling down. (At cost of reacceleration pressure drop)

If a layer of particles is existing along the pipe wall (due to a too low air velocity), thismass has to be kept afloat and will also cost energy.

The remaining active area (smaller than the pipe area) will cause a higher air velocity until the air velocity is high enough to create full conveying.

In horizontal flow the particles that fall out of the main flow will stay at the bottom of the pipe line, causing a smaller flow area until the air velocity is high enough again to create full conveying.

In case of dilute or lean phase conveying, the velocity profile in the pipe (horizontal, vertical or INCLINED) must be capable of keeping the particles in suspension and create the circumstances for full pneumatic conveying.

(Wall velocity a factor above the local suspension velocity)

Under such circumstances, slope conveying is OK or even better.

(Pipe length is shorter and one bend less)

About 12 years ago, I was involved in a cement conveying line of 12” – 400 meters, with a 30 degr. inclined section, half way, of about 40 meters, which performed without any noticeable difference to a horizontal or vertical pipeline.

all for now

teus ■