Particle tracking
Several kinds of particles are tried.
Steel particle : Rho = 8030 kg/m3, dp = 1 micron

Wood particle : Rho = 700 kg/m3, dp = 1 micron

Argon particle : Rho =  1.62 kg/m3, dp = 1 micron

Results for little particles (1 micron) are similar whichever particle mass it is.  Particle are used as a marker that follows the path lines. They are so light that they are considered as having no mass.
On the other hand, it do not deal with two-phase flow. So collisions are not taken into account. So the flow of particles is not physical.

Influence of the diameter
Steel particle : rho = 8030 kg/m3   dp= 10 microns

Steel particle : rho = 8030 kg/m3   dp= 100 microns

Steel particle : rho = 8030 kg/m3   dp= 1 mm

One single steel particle: dp = 1mm

Diameter has a dominant aspect. But as soon as the diameter increases, the flow is less realistic because of the non simulations of collisions.

A aspect that is a peculiarity of FLUENT is the fact that boundary conditions for the particle can be chosen among 3 types: reflection, escape or trap. Here a condition of reflection was chosen. The condition of reflection is quiet simple because the wall reflects the particles with the same angle. But what is disappointing is that symmetry condition is the same as a wall giving regards to the particle.