The particle dispersion mechanisms of rice husk in a fuel-rich/lean burner with an impact-type concentrator were investigated by both digital imaging technique and sampling method. In the experiments, a model burner with a scale ratio of 1/2.708 was studied employing an optical measurement system which consisted of a charge-coupled device (abbreviated as CCD) camera and a laser sheet for illumination. Effects of different impact block heights and inflow particle concentrations on the distribution of rice husk were studied. The distribution of husk particles was obtained by measuring local particle appearance frequency ratio (abbreviated as AFR) within the field of view. Then the size distributions and mass ratios of particles collected from the solid-rich and solid-lean sides were obtained by sampling methods. Increasing the impact block height resulted in a great increase of the rich/lean ratio of particle appearance frequency (abbreviated as RL) at the exit of the burner, as the ratio of 1.66, 5.21 and 9.55 for the block height of 40 mm, 50 mm and 60 mm. Similar tendency was observed when increasing the inflow particle concentration (9.55, 10.57 and 11.87 for 0.1, 0.2 and 0.3 kg/kg). The mean size of particles on solid-rich side was always larger as compared with that on the solid-lean side. (C) 2015 Elsevier Ltd. All rights reserved.