Floating Powder
The rate of accent of a powder in a 4 in diameter pipe full of liquid is likely to be low and the bouyancy effect small to support a protruding bed of wet powder that will probably resist collapse, so the process seems prone to have various operating hazards. A UHMDPE pipe, or one lined with PTFE, would tend to prevent surface adhesion, but it would seem necessary to have a clearing mechanism for the scum to be taken away from the top of the pipe to avoid the formation of a deep layer and the consequent pressure gradient resistance to push up a deep plug by means of a small density differential. ■
Re: Problems With Wall Powder Interactions
Fluid and powder are rather vague descriptions of the constituents. We need a lot more information. ■
Problems with Wall Powder Interactions
powder floating on fluid & problems with wall powder interactions
We have a situation where a powder is injected at the bottom of a 4" pipe, this pipe is filled with a fluid, the powder flows up to the top of the pipe.
Our objective is to inject more powder at the bottom of the system, for it to float upwards and to eventually discharge at the top of the system.
As powder flows up it eventually accumulates on the top of the 4" pipe.
As the thickness level of the powder increases it starts attaching itself to the walls of the pipe and it starts behaving like a solid.
As more powder is injected at the bottom of the system the pressure of the system is increased and the fluid tries to push up the - solid behaving - powder.
This powder now behaves as a solid and the powder wall interactions prevent this new (semi) solid from moving.
The pressure from the fluid increases until the fluid finds crevices on the powder and the fluid flow from the crevices all the way to the top of the pipe where it spills out.
How do we prevent the powder from attaching itself to the pipe?
1) We could make the pipe walls so slippery that the powder cannot find a way to attach itself to the wall and thus it would flow up and down with the ebb and flow of the fluid. Is it possible to do this by creating a mirror finish on the pipe wall and by coating it with some kind of very slippery compound?
2) Could we also vibrate the entire apparatus in order to make the solid powder behave like a fluid?
3) Any other options?
I would appreciate your comments. ■