1. Comparison of the new refrigerant R1336mzz(E) with R1234ze(E) as an alternative to R134a for use in heat pumpsJan Drofenik, Danijela Urbancl, Darko Goričanec, 2022, original scientific article Abstract: R134a is currently the most widely used refrigerant, whose problem is the high value of the
global warming potential, and which will have to be replaced in the near future. Thus far, R1234ze(E)
has proven to be the most suitable alternative, but it is slightly flammable. Recently, R1336mzz(E) has
emerged as a possible alternative. During the research, the mentioned refrigerants were compared
with simulations using the Aspen Plus software package in the case of using groundwater as a heat
source. It was found that R1336mzz(E) could be a suitable alternative to R134a since the highest
value of coefficient of performance was obtained using it. However, it must be superheated with an
internal heat exchanger. The problem with using an internal heat exchanger is that the superheating
of the refrigerant vapors affects the isentropic efficiency of the heat pump compressor negatively and,
consequently, lowers the COP value of the heat pump. It has been shown that a one percent decrease
in isentropic efficiency results in a one percent decrease in the COP value.
Keywords: heat pump, internal heat exchanger, HFO, HFC alternative, GWP
Published in DKUM: 15.05.2025; Views: 0; Downloads: 0
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2. Thermogravimetric, kinetic and thermodynamic behaviour of raw and hydrothermally pretreated oil cakes during pyrolysis and TG-FTIR analysis of the gaseous productsAleksandra Petrovič, Sabina Vohl, Sven Gruber, Klemen Rola, Tjaša Cenčič, Lidija Čuček, Danijela Urbancl, 2025, original scientific article 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: 7
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3. Improving lignocellulosic and non-lignocellulosic biomass characteristics through torrefaction processMaja Ivanovski, Danijela Urbancl, Aleksandra Petrovič, Janja Stergar, Darko Goričanec, Marjana Simonič, 2022, original scientific article Abstract: 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.
Keywords: lignocellulosic biomass, sewage sludge, torrefication, thermogravimetry, TSI
Published in DKUM: 10.04.2025; Views: 0; Downloads: 9
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4. Ocena potenciala medsektorske integracije v Sloveniji s poudarkom vključevanja prometnega sektorja : zaključno poročiloAndreja Nemet, Miloš Bogataj, David Hvalec, Franco Krog, Klemen Rola, Sven Gruber, Jurij Avsec, Danijela Urbancl, Darko Goričanec, Zdravko Kravanja, 2025, final research report Keywords: medsektorska integracija, prometni sektor
Published in DKUM: 03.04.2025; Views: 0; Downloads: 5
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5. Cu(II) and Ni(II) adsorption on torrefied wood waste biomassMarjana Simonič, Darko Goričanec, Aleksandra Petrovič, Ilda Silić, Danijela Urbancl, 2025, original scientific article Abstract: 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.
Keywords: adsorption, torrefication, nitrogen atmosphere, metals
Published in DKUM: 12.03.2025; Views: 0; Downloads: 5
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6. Advancing energy recovery: evaluating torrefaction temperature effects on food waste properties from fruit and vegetable processingAndreja Škorjanc, Sven Gruber, Klemen Rola, Darko Goričanec, Danijela Urbancl, 2025, original scientific article 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: 16
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7. Sustainable hydrothermal co-carbonization of residues from the vegetable oil industry and sewage sludge : hydrochar production and liquid fraction valorisationAleksandra Petrovič, Tjaša Cenčič, Jelena Parlov Vuković, Tomislav Jednačak, Silvo Hribernik, Sabina Vohl, Danijela Urbancl, Marina Tišma, Lidija Čuček, 2024, original scientific article Abstract: In this study, the hydrothermal co-carbonization (co-HTC) of residues from the vegetable oil industry (pumpkin oil cake– PC, hemp oil cake– HC) and sewage sludge (SS) was investigated for the first time. The co-HTC was performed at 250 C and atreatment time of 5 h. The effects of the mass ratio of the feedstocks (1:1, 1:3 and 3:1) on the properties of the HTC products were investigated using various analytical methods (NMR, XRD, 3D-EEM, FTIR, etc.). The co-HTC of SS with oil cakes resulted in improved fuel properties of the hydrochar and an increase in C content from 36.9 to 53.7 wt%, and an increase in the higher heating value (HHV) from 14.8 to 23.6 MJ/kg. The combination with HC gave hydrochars with a higher HHV and higher C content than the combination with PC. The hydrochar yield varied in the range of 39.4–55.3 wt%. NMR analysis revealed a higher proportion of aliphatic (~60 %) than aromatic compounds (~35 %) in the hydrochars, as well as a high content of orthophosphate and unsaturated fatty acids. The liquid fractions were rich in nutrients and organic compounds, but toxic to aquatic organisms. The hydrochars and liquid fractions performed well in the germination test with plant species.
Keywords: hydrothermal co-carbonization, sewage sludge, vegetable oil industry residues, hydrochar, liquid fraction, valorisation
Published in DKUM: 17.01.2025; Views: 0; Downloads: 10
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8. Primerjava lastnosti produktov pridobljenih s hidrotermalno karbonizacijo in torefikacijo : diplomsko delo univerzitetnega študijskega programa I. stopnjeMatej Zazijal, 2023, undergraduate thesis Abstract: V diplomskem delu smo želeli primerjati postopka hidrotermalne karbonizacije in torefikacije ter lastnosti končnih produktov. Surovini, ki smo ju toplotno obdelali, sta bili papirni in biološki mulj iz papirne industrije. Preverili smo tudi, kakšen je efekt predhodne obdelave mulja z alkoholnim kisom. Hidrotermalno karbonizacijo smo izvedli pri 250 °C z različnima reakcijskima časoma, in sicer 2 h in 4 h. Torefikacijo smo izvedli v atmosferi z dušikom in atmosferi z ogljikovim dioksidom, pri čemer smo vzorce enkrat segreli do 250 °C, drugič pa do 350 °C.
Analiza plinov, ki so se sproščali med torefikacijo, je pokazala, da je ogljikov dioksid tisti plin, ki nastaja v največji meri. Iz elementne analize je razvidno, da se delež ogljika v toplotno obdelanih vzorcih poveča, razmerje H/C in O/C pa se zmanjša. Razmerje goriva je dosti večje pri vzorcih, obdelanih s torefikacijo. Toplotna obdelava zviša kurilno vrednost. Nakisani vzorci so imeli po večini višjo kurilno vrednost. Z višjo temperaturo in daljšim časom obdelave praviloma dobimo oglje, ki ima višjo kurilno vrednost in energijsko gostoto. Največje masne in energijske izkoristke smo dobili pri torefikaciji na 250 °C, na izkoristek pa sta najbolj vplivala temperatura torefikacije in vrsta obdelovanega materiala. Glede na FTIR-spektre sklepamo, da so se celuloza, hemiceluloza in lignin med toplotno obdelavo v večini razgradili. Izmerili smo tudi vrednost pH in prevodnost ter določili vsebnost nutrientov v procesnih tekočinah, ki smo jih dobili s hidrotermalno karbonizacijo.
Keywords: termična obdelava, torefikacija, hidrotermalna karbonizacija, odpadki papirne industrije, analiza plinov, gorivne lastnosti
Published in DKUM: 15.01.2025; Views: 0; Downloads: 44
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9. Obdelava odpadnih procesnih tokov farmacevtskega obrata : magistrsko deloNeža Šantl, 2024, master's thesis Abstract: Magistrsko delom obravnava obdelavo odpadnih procesnih tokov farmacevtskega obrata z naslednjimi metodami obdelave: mikrofiltracija, centrifugiranje, centrifugiranjem z dodatkom kisline in termično obdelavo (hidrotermalna karbonizacija in torefikacija). Za mikrofiltracijo odpadnega micelija so določeni optimalni pogoji pri tlaku 2 bara in pretoku permeata 1,2 m3/h. Centrifugiranje kot metoda obdelave odpadnega micelija zahteva predolg obratovalni čas. Centrifugiranje z dodatkom kisline daje bolj perspektivne rezultate kot metoda predobdelave. Najvišji izkoristek termične obdelave s torefikacijo je 51,42 %, za hidrotermalno karbonizacijo pa 52,27 %. Oba navedena izkoristka sta dosežena pri eksperimentu z dodatkom klorovodikove kisline. Za hidrooglje z dodatkom prej omenjene kisline dosegamo vrednost HHV 31,06 MJ/kg. Trdni produkti so karakterizirani z metodama TGA in FTIR. Tekoči produkti pa z določitvijo karakterizacijskih parametrov (skupen dušik, skupni fosfati, KPK, N-NH4 , fosfatov in sulfatov) in florescenco. Metode dokazujejo visoko vsebnost huimskim kislinam podobnih komponent in aromtskih beljakovin.
Keywords: mikrofiltracija, termični odpadki, farmacevtskih odpadni procesni tokovi, hidrotermalna karbonizacija torefikacija
Published in DKUM: 15.10.2024; Views: 0; Downloads: 42
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10. Analiza in uporaba odpadnega blata iz mesnopredelovalne industrije : diplomsko delo visokošolskega strokovnega študijskega programa I. stopnjeBorut Solina, 2024, master's thesis Abstract: V magistrskem delu smo raziskovali možnosti trajnostne uporabe odpadnega blata, ki nastaja v mesnopredelovalni industriji. Namen našega dela je preučiti alternativne metode ravnanja z odpadnim blatom, s posebnim poudarkom na procesu torefikacije, ki omogoča izboljšanje kurilne vrednosti in zmanjšanje vsebnosti vlage v materialu.
V teoretičnem delu smo opisali delovanje čistilne naprave, iz katere smo pridobili vzorce, in proces torefikacije. Eksperimentalni del je vključeval termično obdelavo vzorcev pri različnih temperaturah in analizo njihovih fizikalnih ter kemijskih lastnosti. Ugotovili smo, da torefikacija znatno povečuje kurilno vrednost obeh vzorcev, "Sito" in "Flotat", pri čemer je toreficirano sito pri 350 °C doseglo najvišjo vrednost, toreficiran flotat pa pri 300 °C. Ugotovili smo tudi, da so toreficirani vzorci sita imeli višji masni delež fiksnega ogljika, medtem ko so toreficirani vzorci flotata imeli višji masni delež pepela, kar pojasni zakaj je imelo nižjo kurilno vrednost kot tudi razmerje goriv. Vsi dokazi strmijo k temu, da so toreficirani vzorci sita bolj primerni za kurjenje in za proizvodnjo energije kot toreficirani vzorci flotata. Glede adsorpcijskih sposobnosti pa smo ugotovili, da je material neprimeren za adsorpcijo fosfata, ker vzorci že vsebujejo fosfatne spojine, medtem ko je za adsorpcijo bakra je primeren. Iz vseh dobljenih rezultatov lahko z gotovostjo trdimo, da kot material za gorivo ter kot adsorbent za razne snovi, je sito toreficirano pri 350 °C, najbolj primerno za uporabo. Za flotat pa je najbolj primeren, ko je toreficiran pri 300 °C.
Rezultati so pokazali, da toreficirano blato predstavlja obetaven vir energije in učinkovit adsorbent za onesnaževala, kot je baker. Raziskava prispeva k razvoju trajnostnih praks v mesnopredelovalni industriji in odpira možnosti za nadaljnje raziskave o uporabi odpadnega blata v različnih aplikacijah. S tem delom smo potrdili, da je učinkovito ravnanje z odpadnim blatom ključno za zmanjšanje okoljskega vpliva in povečanje energetske učinkovitosti.
Keywords: Trajnost, torefikacija, adsorpcija, odpadno blato, čistilna naprava
Published in DKUM: 25.09.2024; Views: 0; Downloads: 16
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