This paper presents results of the solid concentration changes and shear zone analysis in cohesionless bulk solids during granular flow in a rectangular silo using X-ray technique during continuous exposure. The analysis of 1D cross-sectional plots and 2D images based on X-ray radiographs present the evolutions of solid concentrations and formation of shear zones in dry sand during silo discharge. Experiments were carried out with different initial packing densities of sand and silo wall roughness. The obtained 1D and 2D results carried out in the bin section of the silo were compared with the ones obtained on the same silo model using Electrical Capacitance Tomography. This comparison, besides the gravitational flow analysis, is an essential element of the research, which aims at a better interpretation of the measuring signal from ECT in the case of monitoring and diagnostic of solid flow. (C) 2012 Elsevier B.V. All rights reserved.