Ivana Perná

Investigation of polycyclic aromatic hydrocarbon content in fly ash and bottom ash of biomass incineration plants in relation to the operating temperature and unburned carbon content

PURPOSE The use of biomass fuels in incineration power plants is increasing worldwide. The produced ashes may pose a serious threat to the environment due to the presence of polycyclic aromatic hydrocarbons (PAHs), because some PAHs are potent carcinogens, mutagens and teratogens. The objective of this study was to investigate the content of total and individual PAHs in fly and bottom ash derived from incineration of phytomass and dendromass, because the data on PAH content in biomass ashes is limited. Various operating temperatures of incineration were examined and the relationship between total PAH content and unburned carbon in ashes was also considered. METHODS The analysis of PAHs was carried out in fly and bottom ash samples collected from various biomass incineration plants. PAH determination was performed using gas chromatography coupled with mass spectrometry. The correlations between the low, medium and high molecular weight PAHs and each other in ashes were conducted. The relationship between PAH content and unburned carbon, determined as a loss on ignition (L.O.I.) in biomass ashes, was performed using regression analysis. RESULTS AND DISCUSSION The PAH content in biomass ashes varied from 41.1±1.8 to 53,800.9±13,818.4ng/g dw. This variation may be explained by the differences in boiler operating conditions and biomass fuel composition. The correlation coefficients for PAHs in ash ranged from 0.8025 to 0.9790. The regression models were designed and the coefficients of determination varied from 0.908 to 0.980. CONCLUSIONS The PAH content in ash varied widely with fuel type and the effect of operating temperature on PAH content in ash was evident. Fly ashes contained higher amounts of PAHs than bottom ashes. The low molecular weight PAHs prevailed in tested ashes. The exponential relationship between the PAH content and L.O.I. for fly ashes and the linear for bottom ashes was observed.

Variability of total and mobile element contents in ash derived from biomass combustion

Seven samples of the ash derived from biomass, representing both fly and bottom ash, were analysed for a wide spectrum of total and mobile contents of nutrient and potentially risk elements. Several techniques, X-ray fluorescence (XRF) spectrometry, instrumental neutron activation analysis (INAA), proton-induced gamma-ray emission (PIGE) and proton induced X-ray emission (PIXE), inductively coupled plasma-atomic emission spectrometry (ICP-OES), and flame atomic absorption spectrometry (F-AAS) were compared. The results showed fairly good agreement between the XRF and INAA results, where the correlation coefficients (r) varied between 0.96 and 0.98. Lower contents documenting insufficient dissolution of the ash samples in the applied acid mixture were observed for both ICP-OES and AAS. In this case, weaker correlation with the INAA results not exceeding r = 0.7 were obtained. Therefore, the sample decomposition step is a bottleneck of the accurate analysis of this type of materials. For the assessment of plant-available portions of the elements in the ash samples, the Mehlich III extraction procedure and the extraction with a 0.11 mol L−1 solution of CH3COOH were applied. The results showed relatively low mobility of the elements (especially micronutrients) in the ash samples regardless of their source and composition, suggesting limited immediate effect of direct ash application as a fertilizer.

The Manufacture of the Grinding Wheels Based on the Ca–K Geopolymer Matrix

This article describes the successful manufacture of new grinding wheels based on a binding agent from a clay substance and blast-furnace slag (the Ca–K geopolymer matrix) on industrial presses. Trained factory staff of the company Best – Business, a.s. tested the pressing process for the manufacture of geopolymer-bonded wheels and verified their quality by factory control equipment (Grindo Sonic and Zeiss-Mackensen methods, test of the safe peripheral speed). The results have shown that the Ca–K geopolymer matrix is suitable for grinding-tool preparation and the grinding-wheel properties are comparable with similar products based on the fired ceramic binding agent.

Determination of Plant-Available Nutrients in Two Wood Ashes: The Influence of Combustion Conditions

ABSTRACT Wood ashes were traditionally used as a fertilizing agent from the very beginning of working land but the fertilizing quality varies according to the combusted biomass and also the industrial burning equipment. The differences between wood ash originated from fluid and classic boiler were investigated by X-ray powder diffraction (XRD), X-ray fluorescence spectrometry (XRF), differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), and Mehlich 3 and deionized water extraction procedures in relation to extraction time. The results, especially of the SEM and chemical extractions, have demonstrated that the type of burning boiler determines the portions of the leachable nutrient elements. The silica and alumina ash content conducted by the elevated temperature transforms the main proportion of calcium and potassium into the insoluble feldspars. Due to this effect only a small amount of nutrients could be released and served as a fertilizing matter.

27Al Magic Angle Spinning–Nuclear Magnetic Resonance (MAS-NMR) Analyses Applied to Historical Mortars

In addition to a calcium-containing substance, medieval mortars usually contain alumina-silicates in various forms, such as the remnants of weathered rocks, clays, and crushed ceramics. As researchers have long ignored the role of alumina-silicates in historical mortars, this study focused on the aluminum coordination in mortars performed by 27Al magic angle spinning–nuclear magnetic resonance (MAS-NMR) in the solid state. The identification of aluminum coordination with oxygen helps to explain the thermal treatment of clayed substances in calcareous rock the common knowledge of the addition of ceramic shards to calcareous matrices. The specific behavior of the thermal transformation of aluminum ions at temperatures <1000° C results in its hydration in alkali aqueous conditions during the lime slaking process. Alumina and silica in common 4-fold coordinated positions form polycondensed chains where negative charge of 4-fold coordinated aluminum ion is balanced by calcium.

The Influence of Temperature and Composition on Modeled Mortars

The study presents the results of modeled mortars prepared from the combination of lime and thermally treated clay as a substitute for the fragmented ceramics used in the past. The influence of the temperature of lime burning and ceramic firing is decisive for the products of their thermal treatment. The results of the final products of the prepared mortar matrices influenced by low temperature of treatment were compared with ancient mortar using modern analytical methods. The study was focused on alumina-silicates in calcareous surroundings and on the identification of the bonds between all components. The principle seems to be the coordination of aluminum ions to oxygen and its behavior of netting with silicon in aqueous alkali conditions.

Application of a clay-slag geopolymer matrix for repairing damaged concrete: Laboratory and industrial-scale experiments

Abstract Blast-furnace slag, a remnant of the old iron production, was used for a preparation of a clay-slag geopolymer which was applied to old concrete surface. An interface investigation by scan electron microscopy (SEM) confirmed the hypothesis that a clay-slag geopolymer can be used for repairing concrete. Based on the laboratory experiments, a highly damaged and contaminated old concrete floor with potholes ranging from 2 mm to 20 cm, located in metal manufacturing industrial plant, has been repaired overnight by a clay-slag geopolymer matrix (ratio of 1 : 0.5) filled with sand and pebbles (the total content of 70 wt.-%). This industrial-scale experiment has proven that geopolymers are suitable for damaged concrete repair and the daily rush in heavy industrial conditions has confirmed the resistance and surface hardness of the geopolymer mixture used. The article documents the original state of the floor, its state after eight hours and also two and four years later.