G'Day Lanre,

Conveyor Dynamics, Inc. (CDI) has analyzed a large number of colliding granular streams over the last 8 years using DEM modeling for: conveyor belt chutes, Crushers of many types, many forms of grinding mills, other mineral processing equipment, mining geo-physics and laboratory measurements of flow stream behavior, rock fracture, with gas dynamics coupled to granular flows.

I anticipate you are interested in the predictable resulting granular trajectories and maybe the shear and impact energy spectra of containment surfaces based on known initial flow conditions such as:

a) particle size distribution randomly distributed between streams

b) mass flow rate

c) particle size shapes

d) moisture content influencing interparticle collision

f) chute geometries

g) surface friction between particles and chute walls

I believe CDI can predict, to a reasonably accurate degree, all that you ask. There are elements of your question that have not been addressed. Chute geometries, conveyor specifications and

material properties may have special features not known to us. If you are willing to give it a try, we will oblige you, or tell you where we need further development.

What is the material, rate and size distribution?

Please view our website for an introduction to granular mechanics simulation and visualization:

www.conveyor-dynamics.com

Which Hatch office are you at? I will be in Brisbane the week of July 14 th. Drop me a note if you wish to get together.

Lawrence Nordell

Conveyor Dynamics, Inc.

Bellingham, Washington 98225

USA

ph: 360-671-2200

fx: 360-671-8450 ■

A SECOND NOTE from Nordell:

Hope you see the CDI address. We are located just 50 miles south of Vancouver B.C.

I will be in South Africa for Beltcon 12, presenting chute flow modeling on July 23-24.

Larry ■

Hello Lanre,

It seems you have situation when two conveyors coming from opposite direction are discharging into common spout / chute.

The engineering judgement suggests that if the two streams are impacting nearly along horizontal line (i.e. with opposite velocity), it will result into scattering of material, all around within the chute.

However, if you allow both the streams to fall for certain distance till their velocity is nearly at 60 / 65 degree to horizontal; then there would be less scattering, and also by that time chute cross section at merging point will be quite compact. Thereby, scattered material will not have scope / room for scattering, i.e. least adverse affect.

This is like two river fast streams merging at shallow angle where common stream is created smoothly.

The arrangement would need somewhat larger discharge spout (common).

Things also depend upon the type of material. If the material is very granular and non-abrasive, you can have a partition plate in common chute, from where both the streams will be diverted vertically downwards and then they can merge together without scattering. If such partition plate is used for lumpy and abrasive material, it will need replacement of liners more frequently. The arrangement of partition plate will reduce the size of spout i.e. two discharge pulleys will be somewhat closer, compared to earlier arrangement.

In case, your problem is different than what I have considered, then please clarify / describe.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyor.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■

Repy to Mr. Mulani:

Your are correct in the concept of a lower horizontal velocity component, achieved by the further fall distance, will reduce scattering.

Mr. Oshinowo did not reference the differences in velocity vectors. This could alter the trajectory track by the square of the velocities.

The stream merger may not be like two rivers due to the diversity of the rock size distribution. Large rock colliding with small rock is quite in favor of the large rock. Since mass is proportioned to the cube of the diffence in diameters, a rock with 1/10th the passing diameter will have about 1/1000 times the mass. It is unlikely the large particle coordination number, wrt to small particles, will come anywhere close to canceling the impact energy resultant force. Thus, there could be a significant diversity of flow streams, or scatter, due to velocities and mass gradients.

The initial question does not make clear the intent of the question and the use of the answer. Size of container, balance of forces, trajectories, et al can give a different purpose to the answer.

Lawrence Nordell

Conveyor Dynamics, Inc. ■