Key Parameters of Fly Ashes Generated from the Industrial Energy Sector Decisive for Their Pro-ecological Applications
Paweł RybowiczMichał MochnaczewskiMarcin KoziełŁukasz UruskiArtur ŁagoszMarek MichalíkLucjan ChmielarzAndrzej Adamski
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Abstract:
Fly ashes belong to important byproducts, accompanying industrial energy production based on combustion technologies. Dependent upon the nature and characteristics of the used fuels as well as combustion technologies and their conditions, fly ashes may exhibit different physicochemical properties, limiting their potential applications as raw materials. A burned hard coal, lignite, biomass, or heavy fuel oil may generate fly ashes of various chemical, mineral, and phase characteristics. Both process conditions and humidity can, in turn, strongly influence final textural properties of such materials. Exhaust gas cleaning technologies also cannot be neglected as important factors potentially affecting textural and functional properties of the fly ashes. For example, denitrification processes, where NH3 is used as a reducer, can result in the so-called ammonia slip, when excessive, unreacted ammonia undergoes sorption on ash grains, forming the corresponding ammonia salts. Such undesired effects can be problematic for the consecutive use of fly ashes as raw materials or components. The current work was focused on an in-depth analysis of chemical, mineral, and phase compositions of fly ashes of various origin. Their structural, textural, and functional characterizations have been performed by means of X-ray fluorescence, X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller method, Raman and diffuse reflectance infrared Fourier transform spectroscopies. The concentration of NH3(aq) in aqueous effluents was determined by ultraviolet–visible spectrophotometry. On the basis of the obtained results, a hierarchical algorithm for selecting the most important parameters for industrial-scale pro-ecological applications was proposed. The ratio of Si/Al, the main constitutive elements of fly ashes, both content and speciation of iron and/or other transition metals, occurrence of alkali components and carbonaceous residuals, content of ammonia, mineral and phase compositions, grain diameters and morphology, and sorptive affinity of water to surfaces of ashes were selected as crucial parameters, remaining decisive for the successful exploitation of ashes as raw materials.Cite
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As electricity increases every year in our country,the emissions from coal-fired power plants fly ash also increase and the environmental problem of fly ash is increasingly serious. Due to the use of fly ash much less than the total emissions,new areas of development and utilization of fly ash become a research hotspot. This paper analyzed the composition and morphology of fly ash. And the main application of fly ash were also discussed. The fly ash as adsorbent were used to remove SO2,CO2 and Hg in flue gas. This paper emphasized the present situation of the SCR denitration catalyst,the removal effect of NOxwith fly ash loading with transition metals as low-temperature SCR denitration catalyst and the preparation method of catalyst. Fly ash has been proved to have good removal effect of SO2,CO2,Hg and NOxin many studies. Because of good application of fly ash in flue gas treatment,the future development direction of fly ash to control pollution was propoesd.
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