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Abstract: V diplomskem delu obravnavamo možnost trajnostne proizvodnje sintetičnega metanola iz ogljikovega dioksida in vodika, pridobljenega z elektrolizo vode z uporabo obnovljivih virov energije. Cilj naloge je bil s pomočjo programskega paketa Aspen Plus razviti računalniški model procesa sinteze metanola ter analizirati vpliv ključnih obratovalnih parametrov na učinkovitost procesa. V teoretičnem delu so predstavljeni viri in metode pridobivanja vodika, možnost zajemanja CO2 ter lastnosti, proizvodnja, uporaba in shranjevanje metanola kot alternativnega goriva in nosilca energije. V eksperimentalnem delu smo zasnovali procesno shemo, ki vključuje kompresijo reaktantov, sintezo produktov v reaktorju, fazno ločevanje ter čiščenje končnega produkta. Rezultati računalniške simulacije kažejo vpliv temperature in tlaka na konverzijo CO2 in selektivnost do metanola. Občutljivostna analiza je potrdila, da je vrednost refluksnega razmerja in tlaka ključnega pomena za izboljšanje izkoristka in čistosti končnega produkta. Ugotovili smo, da je računalniška simulacija uporabno orodje za predhodno vrednotenje rezultatov trajnostnih kemijskih procesov ter da je proizvodnja metanola iz obnovljivih virov energetsko in okoljsko smiselna alternativa klasični proizvodnji. Proizvodnja metanola iz obnovljivih virov energije predstavlja pomemben korak k zmanjšanju emisij toplogrednih plinov in razogljičenju industrije. Takšni procesi omogočajo učinkovito izrabo presežkov električne energije iz obnovljivih virov in prispevajo k razvoju krožnega gospodarstva ter energetski neodvisnosti.
Keywords: obnovljivi viri energije, sinteza metanola, hidrogeniranje CO2, Aspen Plus, energetska učinkovitost
Published in DKUM: 15.07.2025; Views: 0; Downloads: 36
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Abstract: The pyrolysis of raw and hydrothermally (HTC) pretreated pumpkin (PC) and hemp (HC) oilseed cakes was investigated for the first time using thermogravimetric, kinetic and thermodynamic analyses. The influence of the HTC pretreatment and the type of reaction liquid (whey or water) on the pyrolysis was investigated and the pyrolysis gases were analysed. The HTC pretreatment increases the biochar yield with values of up to 44 wt.% compared to raw oil cakes (∼27 wt.%). The HTC pretreatment with whey resulted in a higher energy and biochar yield and better biochar properties than the pretreatment with water. The tested oil cakes provided comparable energy yields, although HC provided higher biochar yields, while PC biochar showed higher hydrophobicity. The kinetic modelling shows that the activation energies () for the pyrolysis of the raw oil cakes varied between 93.6 and 529.9 kJ/mol for PC and between 71.3 and 669.9 kJ/mol for the HC sample. HTC pretreatment in water media increased the values, while the use of whey led to a decrease in the values. TG-FTIR analysis of the emitted gases showed that the HTC treatment affected the release of CO2 and hydrocarbons as well as the pyrolysis mechanism and reaction pathways
Keywords: oilseed cake, hydrochar, pyrolysis, thermogravimetric analysis, kinetic analysis, gas emissions
Published in DKUM: 25.04.2025; Views: 0; Downloads: 15
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Abstract: Most organic waste from food production is still not used for energy production. From the perspective of energy production, one option is to valorise the properties of organic waste. The fruit juice industry is growing rapidly and generates large amounts of waste. One of the main wastes in food and fruit juice processing is peach pits and apple peels. The aim of this study was to analyse the influence of torrefaction temperature on the properties of food waste, namely apple peels, peach pits and pea shells, in order to improve their energy value and determine their potential for further use and valorisation as a renewable energy source. The aim was to analyse the influence of different torrefaction temperatures on the heating value (HHV), mass yield (MY) and energy yield (EY) in order to better understand the behavior of the thermal properties of individual selected samples. The torrefaction process was carried out at temperatures of 250 ◦C, 350 ◦C and 450 ◦C. The obtained biomass was compared with dried biomass. For apple peels, HHV after torrefaction was (28 kJ/kg), MY decreased by (66–34%), while EY fell by (97–83%). Peach pits, despite a higher HHV after torrefaction (18 kJ/kg), achieved low MY (38–89%) and EY (59–99%), which reduces their efficiency in biochar production. Pea peels had EY (82–97%) and a lower HHV after torrefaction (11 kJ/kg), but their high ash content limits their wider use. The results confirm that, with increasing temperature, MY and EY for all selected biomasses decrease, which is a consequence of the degradation of hemicellulose and cellulose and the loss of volatile compounds. In most cases, increasing the torrefaction temperature improved the resistance to moisture adsorption, as this is related to the thermal process that causes structural changes. The results showed that the torrefaction process improved the hydrophobic properties of the biomass samples. Temperature was seen to have a great impact on mass energy efficiency. Apple peels generally had the highest mass and energy yield.
Keywords: torrefaction, food waste, energy from waste, higher heating value, energy potential
Published in DKUM: 07.02.2025; Views: 0; Downloads: 20
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Abstract: Synthetically produced biofuels play a critical role in the energy transition away from fossil fuels. Biofuels could effectively lower greenhouse gas (GHG) emissions and contribute to better air quality. One of these biofuels is bioethanol, which could act as a gasoline replacement. For this purpose, a simulation of bioethanol production through lignocellulosic biomass fermentation, focused on distillation, was carried out in simulation software Aspen Plus. Since the possibility of absolute ethanol production through distillation is limited by the ethanol–water azeotrope, pressure swing distillation (PSD) was used to obtain fuel-grade ethanol (EtOH) with a fraction of 99.60 wt.%. The flowsheet was optimised with NQ analysis, which is a simple optimisation method for distillation columns. We found that the PSD has the potential to concentrate the EtOH to a desired value, while simultaneously removing other unwanted impurities whose presence is a consequence of pretreatment and fermentation processes.
Keywords: bioethanol, distillation, lignocellulosic biomass, azeotrope, Aspen Plus
Published in DKUM: 14.08.2024; Views: 99; Downloads: 31
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Keywords: power-to-methane, P2M, synthetic methane, CO2 methanation, Aspen Plus, Aspen Adsorption
Published in DKUM: 18.04.2024; Views: 203; Downloads: 15
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