The influence of binders for the pelletization of fly ash zeolites on sulfur dioxide sorption properties

Fly ash zeolites are economically and ecologically attractive alternatives to synthetic and natural zeolites. Their use as sulfur dioxide sorbents is one of the possible applications of these materials. During the process of fly ash zeolite synthesis, a light powder is formed, which is not acceptable in practical applications due to technical problems, such as a marked drop in pressure, diffusion limits, hydraulic resistance, clogging in the packed beds and the possibility of losing a bed. It is therefore necessary to perform a pelletization process. Thickening of the material during pelletization influences sorption capacity negatively due to diffusing limitations, while the lack of an additional binder may result in a material of low mechanical durability. In this study, pressure pelletization experiments with fly ash zeolite were performed. Binders were selected on the basis of economic considerations as well as their potential to exert a positive influence on the sorption properties of the produced pellets. Cyclic sorption experiments were conducted (on sulfur dioxide) in which one zeolite powder sample was subjected to pelletization without a binder and another sample was subjected to the process with selected binders added. The results of the experiments were then analysed to ascertain the influence of the pelletization process on sulfur dioxide sorption capacity.

Processing of high-grade zeolite nanocomposites from solid fuel combustion by-products as critical raw materials substitutes

High-grade zeolite nanocomposites are synthesized utilizing solid by-products from combustion of coal for energy production in Thermal Power Plants applying alkaline aging, hydrothermal and fusion-hydrothermal activation procedures. The obtained coal ash zeolites were studied with respect to their chemical and phase composition, morphology, surface parameters and thermal properties. It was found that they are distinguished in nanocrystalline morphology and significant content of iron oxide nanoparticles (γ-Fe2O3, α-Fe2O3, γ-Fe3O4) and doping elements (Cu, Co, Mn, V, W, etc.) transferred from the raw coal ash, and therefore they are assumed as nanocomposites. Coal fly ash zeolite nanocomposites are characterized by a mixed micro-mesoporous texture, significant concentration of acidic Brønsted centers due to their high surface insaturation, high chemical and thermal stabilty. This unique combination of compositional and textural properties predetermines the application of these materials as catalysts for thermal oxidation processes, anticorrosion barrier coatings, carbon capture adsorbents, matrices for hosting functional groups, detergents etc. Examples for coal fly ash zeolite applications for substitution of critical raw materials in practice are provided.