When a two-phase, gas-solid suspen-sion undergoes a directional change, such as in a bend, the bend naturally acts as a segregator or separator of the two phases. Due to the centrifu-gal forces acting on the particles, they are concentrated along the outer wall of the bend. For instance, in the case of fine coal, an unusual phenomenon of “roping” (the formation of concen-trated strands) is observed. Depending on material properties, solids loading, gas velocity and pipe-wall interac-tions, the particles may have multiple impacts within the body of the bend.