Quantitative phase analysis and rietveld texture determination of minerals in ash deposits in a 11.2 MW moving grate boiler

Abstract

Some ash deposits were sampled from a 11.2 MW moving grate boiler to study the mineral transformation, ash deposition and mineral texture evolution behavior, which were determined by different analytical methods. Rietveld refinement was applied to determine the mineralogy, refine the crystallographic structures of minerals, and characterize texture heterogeneity of minerals in ash deposits. The results presented that the major mineral phases in ash deposits were identified as silicates, oxides, sulphates, sulfides and carbonates. The phase transformation between minerals during combustion was proposed. The variation of the diffraction peak intensities indicated the existence of the weak and strong textures. The texture indexes were larger than one mrd2 for most minerals, implying strong preferred orientation distributions, while the texture indexes of some other minerals were approaching one mrd2, indicating the existence of weak and random textures. Some pole figures showed strong texture features with a high degree of texture disorder in these minerals, while other minerals displayed weak textures with low volume diffractions of preferred orientations in these mineral phases. Owing to the diffraction peak overlapping of different minerals, different texture components with fibre-like or biaxial-like characteristics were found in ash deposits.