Iskanje po katalogu digitalne knjižnice

Opis: 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
Ključne besede: oilseed cake, hydrochar, pyrolysis, thermogravimetric analysis, kinetic analysis, gas emissions
Objavljeno v DKUM: 25.04.2025; Ogledov: 0; Prenosov: 2
Celotno besedilo (9,44 MB)

Opis: 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.
Ključne besede: torrefaction, food waste, energy from waste, higher heating value, energy potential
Objavljeno v DKUM: 07.02.2025; Ogledov: 0; Prenosov: 15
Celotno besedilo (3,55 MB)

Opis: 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.
Ključne besede: bioethanol, distillation, lignocellulosic biomass, azeotrope, Aspen Plus
Objavljeno v DKUM: 14.08.2024; Ogledov: 99; Prenosov: 6
Celotno besedilo (3,14 MB)

Ključne besede: power-to-methane, P2M, synthetic methane, CO2 methanation, Aspen Plus, Aspen Adsorption
Objavljeno v DKUM: 18.04.2024; Ogledov: 203; Prenosov: 13
Celotno besedilo (5,00 MB)
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Opis: Toplotne črpalke so naprave, ki izrabljajo nizkotemperaturne vire za visokotemperaturno gretje, navadno sanitarne vode. V diplomskem delu smo s pomočjo računalniškega paketa Aspen Plus V10 primerjali subkritične in transkritične toplotne črpalke s štirimi različnimi naravnimi hladilnimi sredstvi: ogljikov dioksid, amonijak, propan in izobutan. Simulacije so bile izvedene pri izstopnih temperaturah hladilnega sredstva iz kondenzatorja oz. plinskega hladilnika med 15 °C in 30 °C in temperaturah uparjanja od -30 °C do 10 °C. Za cilj smo si zastavili gretje konstantnega toka vode na temperaturo med 40 °C in 60 °C, s koraki po 10 °C. Namen diplomske naloge je bil poiskati najučinkovitejše naravno hladilno sredstvo, ki bi predstavljalo ekonomsko ugodno rešitev in hkrati okolju prijazno alternativo trenutno uporabljenim toksičnim in okolju škodljivim hladilnim sredstvom. Najvišje vrednosti COP smo zasledili pri temperaturi uparjanja 10 °C, temperaturi hladilnega sredstva po kondenzaciji 15 °C in najnižji tarčni izstopni temperaturi vode 40 °C. V transkritičnem ciklu je najučinkovitejše hladilno sredstvo ogljikov dioksid, v subkritičnem se pa je amonijak izkazal boljše od ostalih. Slednji je skupno boljši od transkritičnega ogljikovega dioksida, vendar ima določene slabe lastnosti kot so toksičnost v višjih koncentracijah, vnetljivost in nekompatibilnost z bakrom.
Ključne besede: toplotne črpalke, subkritičen cikel, transkritičen cikel, COP, naravna hladilna sredstva
Objavljeno v DKUM: 08.09.2021; Ogledov: 941; Prenosov: 119
Celotno besedilo (2,91 MB)