The paper presents an experimental study of gas-solid flow in an ironmaking blast furnace under various conditions to address a few important issues: two-dimensional (2D) slot model vs full three-dimensional (3D) model, normal vs abnormal operations, and spherical vs non-spherical particles. The quantitative comparisons made between the 2D slot and the full 3D models under comparable conditions reveal that whilst the key solid flow features are similar in both models, the relative sizes of the different flow zones in a model furnace differ considerably. The effects of operational parameters on the flow behaviour are examined in both 2D and 3D models, including gas and solid flow rates, material properties such as particle roughness and shape, and abnormal conditions such as asymmetric charging and scabs. It reveals that the stagnant zone is significantly affected by gas and solid flow rates in the 2D slot model. but not in the 3D model. Particles with angular shapes and a high internal angle of friction produce steep profiles of the stagnant zone. The solid flow behaviour with layers of different materials and a homogeneous mix of materials are similar. Studies in asymmetric flow experiments reveal that the flow behaviour on one side is largely independent of the flow on the other side in the 2D slot model. The presence of scabs causes retardation of the flow on the wall, and the layer orientation changing from horizontal to vertical. The results are useful not only in developing further understanding of solid flow in a BF but also in verifying different mathematical models, particularly the discrete particle simulation which has been increasingly used in the literature. (C) 2010 Elsevier B.V. All rights reserved.