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Zmiana właściwości wytrzymałościowych popiołu z biomasy i węgla w trakcie procesu spiekania

Król Karol, Nowak-Woźny Dorota

Zeszyty Energetyczne

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2020

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T. 7

213-222

PL

W artykule przedstawiono badania wytrzymałości mechanicznej próbek popiołu z biomasy (słoma pszenna) i węgla kamiennego w trakcie procesu spiekania. Celem pracy była obserwacja zmian właściwości mechanicznych – wartości naprężeń niszczących – sprasowanych próbek popiołu z wybranych paliw stałych o różnym pochodzeniu i różnym składzie chemicznym oraz wyjaśnienie mechanizmu odpowiedzialnego za obserwowane zmiany. Próbki z biomasy i węgla kamiennego spiekano w odpowiednio szerokim zakresie temperatur. Badanie naprężeń niszczących uzupełniono o badania chemiczne (analiza techniczna, elementarna i tlenkowa), ciśnieniowe (test ciśnieniowy) oraz termiczne (test Leitza). Na podstawie analizy otrzymanych rezultatów stwierdzono, że obserwowana gwałtowna zmiana wytrzymałości mechanicznej spiekanego popiołu jest wywołana zmianami gęstości popiołu na skutek zmian mikrostrukturalnych, wywołanych topnieniem powierzchni pojedynczych ziaren popiołu i tworzeniem się większych aglomeratów. Wyniki pomiarowe oraz wyniki analiz wykonane dla biomasy są analogiczne jak dla węgla.

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Sequential leaching analysis to investigate the sintering process of coal, cereal pellets and wood pellets Ash

Szydełko Arkadiusz, Nowak-Woźny Dorota, Urbanek Bartosz, González-Valdés Laura, Rybak Wiesław

Chemical and Process Engineering

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2019

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Vol. 40, nr 2

189–-199

EN

The presence of inorganic elements in solid fuels is not only considered a direct source of problems in the furnace but is also connected with the release of pollutants into air during combustion. This article focuses on the sintering characteristics of biomass and coal ashes, in particular on the leaching processes, and their impact on the tendency to sinter ash. Biomass and coal ash with high alkali metal concentration can deposit in boiler sections and cause severe operating problems such as slagging, fouling and corrosion of boiler and heat exchanger surface, limiting heat transfer. Two biomass types and one coal ash with different origin and different chemical compositions were investigated. A sequential leaching analysis was employed in this study to elucidate the modes of occurrence of metals that can transform into fuel extract. Sequential leaching analysis was conducted as a two-step process: using distilled water in the first step and acetic acid in the second step. The chemical composition of ashes, before and after each step of the leaching processwas studied using ICP-OES method. The standard Ash Fusion Temperature (AFTs) technique was also employed to assess the sintering tendency of the tested samples. It was observed that the presence of key elements such as sodium, potassium, magnesium and sulphur (elucidated in the leaching process) plays a significant role in sintering process. The sintering tendency enhances when the concentration of these elements increases.

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Dielectric properties of coal ash

González Valdes Laura, Friis Aage Valentin, Nowak-Woźny Dorota

Zeszyty Energetyczne

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2018

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T. 5

51--60

EN

Mineral matter of coal causes serious operational problems related to ash de- position in coal fired power plants such slagging and fouling, and so it has become the main subject of study in terms of current utilization. Moreover, the standardized tests currently used as the preferred predictive tools for slagging properties of coal sources have been lately reproved in the literature and un- certainties arrive due to the poor repeatability and reproducibility. That is why, methods for determining the sintering temperatures are being extensively investigated across the industry. This study focuses on the electrical properties of coal ash and its relation to the ash sintering process, where physical and chemical processes take part inside the material. The following methodology is based upon the continuous registration of the changes of resistance measured as an AC and DC property. The proposed laboratory stand allows measuring ‘in situ’ a coal ash sample being heated to analyse its electrical properties. It was found that the values measured are temperature dependent and could reflect the chemico-physical changes in the material, which may directly suggest the transformation of the intrinsic properties, giving insight into the sintering process.