Pumping wood chips suspended in water

Question

Pumping wood chips suspended in water

Patrick LaPointe (Mechanical)

(OP)

1 Apr 23 15:00

Looking to communicate directly or through this forum with individuals with experience in pumping wood chips suspended in water. In order for the wood chips to "move along" would not the wood chips need to develop a shear force between the wood chips and the water. Is this the transport mechanism? I am told that the present "system" is pumping wood chips in a 6" diameter pipe flowing mostly vertically up to feed a continuous digester in a pulp mill, I am also told that the present piping configuration is experiencing broad band vibration. I would expect such broad band vibration. Is the solution to provide adequately stiff pipe supports?

Thank you,

Pat (in eastern Canada)

1503-44 (Petroleum) · Answer 1 · 2023-04-01 16:49:49

Both differential pressure on the face of the wood chips and shear force across those same faces.

Excessive constant Vibration of pipe is mostly caused by the wrong distances between usually adequately firm supports. It's more to do with the natural dynamic frequency of the pipe span distance somehow matching some excitation force, from pressure pulses coming from the pump, or maybe it could be the wind. What vibration frequency do you have? Is it all along the pipe, or only between some supports. Are those supports at unusual distances apart?

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

EdStainless (Materials) · Answer 2 · 2023-04-01 20:11:14

The combination of pipe stiffness, support locations, and support stiffness are all part of this.
I have seen cases where people 'stiffened' the supports and proceeded to break the pipe.
The energy has to go somewhere.
Supports tend to be placed are uniform intervals.
If this is anywhere near the natural frequency of the pipe you are in for a lot of trouble.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

Artisi (Mechanical) · Answer 3 · 2023-04-02 02:43:27

Just for thinking, why not blow the chips rather than pumping?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

pierreick (Chemical) · Answer 4 · 2023-04-02 05:08:46

Hi ,
You may want to check whether this technology is suitable for your application.
https://www.yamadapump.com/powder-pumps-applicatio...
Pierre

LittleInch (Petroleum) · Answer 5 · 2023-04-02 06:22:22

To me this is a form of slurry pumping in which the wood chips - that's a very ill defined term - are suspended in the waste and simply flow along with the water.

How big are these "chips"? Like sawdust or much bigger? What is the wood to water ratio?

Usually the key in slurry pumping is to move for continuously and at a decent velocity (> 1m/sec) such that the mixture doesn't stratify or start to create "clumps" of material.

Could this mixture be creating such clumps?

If this is a common practice in word Mills then it's likely someone has done some study work on it.

Has this piping got a lot of bends?

Slurry piping needs to have a few as possible.

A bit more information would help....

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Pumping wood chips suspended in water