Simulating Lean phase conveying of coal.

Damian -

yes, once you have run a fluid simulation based on the geometry and boundary conditions, you can insert a particle study. 

You define the density, particle size, particle mass feed rate, etc. and based on the velocity contours Flow will determine where the particles move.  Then you can either animate the flow or use simply cross-section plots to determine the movement.  Tracking the x,y,z components you can decide when there is little enough deviation from axial travel.