Iskanje po katalogu digitalne knjižnice

Opis: Particulate matter (PM10 and PM2.5) is a key contributor to urban air pollution and poses significant health risks, particularly in densely populated areas. While conventional air quality monitoring focuses on particle size and concentration, this study emphasizes the importance of understanding chemical composition and emission sources for effective air pollution management. PM samples were collected between 2019 and 2022 at two locations in the Republic of Slovenia: a traffic-dominated urban site and an industrial area. Annual average PM10 concentrations ranged from 14 to 34 μg/m3, and those of PM2.5 ranged from 9 to 22 μg/m3. In addition to decreasing annual concentrations, a notable reduction in exceedance days was observed between 2019 and 2022, indicating the effectiveness of recent air quality improvement measures. Meteorological data and statistical models were used to assess environmental influences on PM variability. Advanced SEM-EDS analysis revealed substantial seasonal and spatial differences in particle composition, with key elements such as silicon (4.3–28.4%), carbon (13.1–61.7%), and trace amounts of lead and zinc varying across sites and particle types. Mineral dust (Si, Al, Ca, Fe, Mg), originating from soil resuspension, construction, and Saharan dust, was dominant. Combustion-related particles containing C, Pb, Zn, and Fe oxides were associated with vehicle emissions, industrial processes, and biomass burning. Secondary aerosols, such as sulphates and nitrates, showed seasonal trends, with higher concentrations in summer and winter, respectively. The results confirm that PM levels are driven by complex interactions between local emissions, weather conditions, and seasonal dynamics. The study supports targeted policy measures, particularly regarding residential heating and traffic emissions, to improve air quality.
Ključne besede: air pollution, air quality, PM particles, SEM-EDS, Slovenia
Objavljeno v DKUM: 30.05.2025; Ogledov: 0; Prenosov: 1
Celotno besedilo (4,02 MB)

Opis: In this study, three locally available biomasses, namely miscanthus, hops, sewage sludge, and additionally, their mixtures, were subjected to the torrefaction process to improve their fuel properties. The torrefaction process was conducted at 250–350 ◦C and 10–60 min in a nitrogen (N2) environment. The torrefaction temperature and time were studied to evaluate the selected biomass materials; furthermore, heating values, mass and energy yields, enhancement factors, torrefaction severity indexes (TSI), and energy-mass co-benefit indexes (EMCI) were calculated. In addition, thermogravimetric (TGA) and Fourier transform infrared analyses (FTIR) were performed to characterize raw and torrefied biomass under the most stringent conditions (350 ◦C and 60 min). The results showed that with increasing torrefaction temperature and duration, mass and energy yields decreased, and heating values (HHVs) increased for all studied biomasses. The results of the TSI and EMCI indexes showed that the optimum torrefaction conditions were as follows: 260 ◦C and 10 min for pure miscanthus and hops, whilst this could not be confirmed for the sewage sludge. Furthermore, the combination of sewage sludge and the above-mentioned types of lignocellulosic biomass exhibited better fuel properties than sewage sludge alone.
Ključne besede: lignocellulosic biomass, sewage sludge, torrefication, thermogravimetry, TSI
Objavljeno v DKUM: 10.04.2025; Ogledov: 0; Prenosov: 14
Celotno besedilo (3,64 MB)
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Opis: The aim of the research was to study the torrefaction processes of wood biomass, compare the product characteristics at different torrefaction temperatures, and assess both moisture adsorption on raw and torrefied samples, as well as metal (Cu(II) and Ni(II)) adsorption on torrefied biomass. The novelty of the research was to investigate whether the presence of adsorbed metals in torrefied biomass significantly affects the energetic properties of the torrefied biomass, compared to torrefied biomass without metals. First, wood samples were torrefied at temperatures of 250 °C, 350 °C, and 400 °C. Following torrefaction, thermogravimetric analysis (TGA) was performed to evaluate mass loss and thermal stability. Next, changes in surface functional groups were examined, and higher heating values (HHV) were measured to assess the energy content. The results showed that torrefaction significantly increased the hydrophobicity of the biomass, leading to reduced moisture adsorption and enhanced material properties. Additionally, the adsorption of Cu(II) and Ni(II) ions on torrefied biomass was investigated. The results showed that the adsorption efficiency for Cu(II) was higher, reaching 62.4%, compared to Ni(II) at 21.2%. The adsorption process followed a pseudo-second-order kinetic model, which indicated that chemisorption was the dominant mechanism.
Ključne besede: adsorption, torrefication, nitrogen atmosphere, metals
Objavljeno v DKUM: 12.03.2025; Ogledov: 0; Prenosov: 6
Celotno besedilo (8,49 MB)

Opis: Onesnažen zrak je eden najbolj perečih problemov sodobnega časa, zato je kontrola koncentracije onesnažil ključna za doseganje želene kvalitete življenja. Nadzor kakovosti zraka v Sloveniji opravlja Javna agencija Republike Slovenije za okolje (ARSO) in podatke redno objavlja na svoji spletni strani. Namen diplomske naloge je bil primerjati vrednosti onesnažil PM10 in PM2,5 v zraku v določenem časovnem obdobju. Analiza je bila izvedena na podlagi javno dostopnih podatkov na dveh merilnih mestih v Sloveniji, ki se razlikujeta po gostoti poselitve, reliefu in meteoroloških parametrih. Prvo merilno mesto je bilo prometno in urbano središče, drugo pa se je nahajalo v bližini večjega termoenergetskega objekta. Ugotovljeno je bilo, da se onesnaženost zraka s PM10 in PM2,5 tekom let zmanjšuje in da je onesnaženost s PM10 in PM2,5 večja na merilnem mestu z večjo gostoto poselitve, večjo količino prometa in manj ugodnim reliefom, ki otežuje izločanje onesnažil iz ozračja. Poleg tega je bila koncentracija delcev na obeh merilnih mestih najvišja pozimi, zaradi uporabe kurilnih peči v gospodinjstvih, ki so glavni vir izpustov, in najnižja poleti. Pandemija COVID-19 na zmanjšanje emisij delcev ni imela večjega vpliva. Nazadnje je bila izvedena še SEM-EDS analiza filtrov. Najpogosteje zastopani elementi na obeh merilnih mestih so bili ogljik, kisik in silicij, pri čemer je bila koncentracija ogljika na prvem merilnem mestu več kot dvakrat večja, najbrž zaradi večje količine izpustov iz prometa. Ostali elementi so bili na obeh merilnih mestih zastopani v približno enakem razmerju in jih gre predpisati različnim naravnim in antropogenim procesom.
Ključne besede: zrak, onesnaženost, kakovost, PM delci, SEM
Objavljeno v DKUM: 19.09.2024; Ogledov: 0; Prenosov: 29
Celotno besedilo (2,27 MB)

Opis: Geothermal energy, derived from the Earth’s internal heat, can be harnessed due to the geothermal gradient between the Earth’s interior and its surface. This heat, sustained by radiogenic decay, varies across regions, and is highest near volcanic areas. In 2020, 108 countries utilised geothermal energy, with an installed capacity of 15,950 MWe for electricity and 107,727 MWt for direct use in 2019. Low-enthalpy sources require binary systems for power production. Open-loop systems face issues like scaling, difficult water treatment, and potential seismicity, while closed-loop systems, using abandoned petroleum or gas wells, reduce costs and environmental impacts greatly. The novel geothermal gravity heat pipe (GGHP) design eliminates parasitic power consumption by using hydrostatic pressure for fluid circulation. Implemented in an abandoned well in north-east (NE) Slovenia, the GGHP uses a numerical finite difference method to model heat flow. The system vaporises the working fluid in the borehole, condenses it at the surface, and uses gravitational flow for circulation, maintaining efficient heat extraction. The model predicts that continuous maximum capacity extraction depletes usable heat rapidly. Future work will explore sustainable heat extraction and potential discontinuous operation for improved efficiency.
Ključne besede: geothermal energy, geothermal gravity heat pipe, numerical modelling, single well closed-loop heat exchanger
Objavljeno v DKUM: 03.09.2024; Ogledov: 41; Prenosov: 15
Celotno besedilo (3,23 MB)