This paper reports the results of an experimental investigation into the transport of fluids composed of water and polypropylene particles, in order to study the transport of floating particles. The determination of the pressure drop and the delivered concentration, for a wide combination of flow rates (0-0.5 kg s À1), solid loads (0-25 %vol) and particles mean sizes (341-756 lm), enabled the transport efficiency for this kind of slurry in a circular horizontal pipe (30 mm diameter) to be measured. The results are displayed in relation to flow patterns; they show that the size of the particles has a little impact on the transport efficiency. On the contrary, the flow rate and the volumetric concentration have a strong impact on efficiency, because of their large contribution to the flow pattern. The best operating conditions are obtained close to the limit deposition velocity, when the fully suspended pattern is reached. The solids are then well transported with no waste of energy due to a too high velocity. The optimum concentrations, for a wide range of high efficiency are around 20-25 %vol.