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Abstract: Cilj diplomske naloge je obravnava procesa torefikacije odpadne biomase in karakterizacija nastalih produktov. Za predstavnike odpadne biomase so bili izbrani tri različni vzroci, in sicer miskantus, mešan les ter hmelj. Cilj naloge je proizvesti trdno biogorivo z višjo kurilno vrednostjo v primerjavi s surovo biomaso. Proces torefikacije je potekal eno uro pri treh različnih temperaturah, 250 °C, 350 °C in 450 °C. Produkte smo nato kemijsko karakterizirali. Karakterizacijo smo izvedli na trdnih in tekočih produktih torefikacije ter tudi na surovih vzorcih posameznih biomas. Ovrednotili smo masne izgube, masne izkoristke, energijsko učinkovitost, doprinos energije glede na maso, kurilne vrednosti, vsebnost hlapnih snovi, vlage in pepela. S Fourierjevo transformacijo (FTIR) je bila določena struktura vzorcev, s termogravimetrično analizo (TGA) pa termična razgradnja surove in toreficirane biomase. Z naraščanjem temperature torefikacije se kurilne vrednosti trdnih produktov višajo, nižje pa so vrednosti masnih izkoristkov, energetske učinkovitosti ter delež hlapnih komponent. FTIR analiza prikazuje razgradnjo celuloze, ki jo zaznamo z zmanjšanimi vrhovi, z eliminacijo manjših vrhov pa opazimo delno ragradnjo hemiceluloze in lignina. Zvišanje temperature je povzročilo zmanjšanje moči karboksilnih in -OH skupin. V surovi biomasi zaznamo prisotnost aromatskih spojin, simetrične alifatske skupine ter CO-C funkcionalne skupine, ki jih v primerjavi s toreficirano biomaso več ne zaznamo. TGA analiza je bila izvedena v kisikovi atmosferi pri konstantni hitrosti segrevanja v temperaturnem območju 30-900 °C. Ob višjih temperaturah je pokazala oksidacijo fiksnega ogljika, izhlapevanje težko hlapnih snovi ter razgradnjo anorganskih materialov. Glede na rezultate analiz je razvidno, da so trdni produkti primerni za uporabo kot biogorivo, medtem ko je v tekočih produktih delež vode previsok.
Keywords: obnovljivi viri energije, odpadna biomasa, hmelj, torefikacija, kurilna vrednost, termogravimetrična analiza, miskantus, les
Published in DKUM: 09.09.2024; Views: 18; Downloads: 3
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Abstract: The presented paper addresses two significant issues of the present time. In general, the studies of the effect of synthetic fuels on cavitation formation and cavitation erosion prediction in the nozzle tip of common-rail diesel injectors were addressed. The first problem is plastic waste, which can have a significant negative environmental impact if not treated properly. Most plastic waste has high energy value, so it represents valuable material that can be used in resource recovery to produce various materials. One possible product is synthetic fuel, which can be produced using thermal and catalytic pyrolysis processes. The first issue addressed in the presented paper is the determination of fuel properties since they highly influence the fuel injection process, spray development, combustion, etc. The second is the prediction of cavitation development and cavitation erosion in a common-rail diesel injector when using pyrolytic oils from waste plastic. At first, pyrolytic oils from waste high- and low-density polyethylene were obtained using thermal and catalytic pyrolysis processes. Then, the obtained oils were further characterised. Finally, the properties of the obtained oils were implemented in the ANSYS FLUENT computational program and used in the study of the cavitation phenomena inside an injection nozzle hole. The cavitating flow in FLUENT was calculated using the Mixture Model and Zwart-Gerber-Belamri cavitation model. For the modelling of turbulence, a realisable k–ε model with Enhanced Wall Treatment was used, and an erosion risk indicator was chosen to compare predicted locations of cavitation erosion. The results indicate that the properties of the obtained pyrolytic oils have slightly lower density, surface tension and kinematic viscosity compared to conventional diesel fuel, but these minor differences influence the cavitation phenomenon inside the injection hole. The occurrence of cavitation is advanced when pyrolytic oils are used, and the length of cavitation structures is greater. This further influences the shift of the area of cavitation erosion prediction closer to the nozzle exit and increases its magnitude up to 26% compared to diesel fuel. All these differences have the potential to further influence the spray break-up process, combustion process and emission formation inside the combustion chamber.
Keywords: plastic waste, synthetic fuels, pyrolytic oils, common-rail, cavitation, erosion, transient simulation
Published in DKUM: 18.03.2024; Views: 280; Downloads: 14
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Abstract: The 3D unsteady, cavitating, particle-laden flow through a radial divergent test section was simulated with the homogeneous mixture model and Discrete Phase Model (DPM) within the commercial CFD code ANSYS Fluent. For turbulence, a RANS approach was adopted with the Reboud’s correction of turbulent viscosity in the k-ω SST model. Cavitation erosion was predicted with the Schenke-Melissaris-Terwisga (SMT) model, while particle erosion was predicted with the Det Norske Veritas (DNV) model. Two distinct erosion zones were identified, one for pure cavitation erosion and one for pure particle erosion. The occurrence of the pure particle erosion zone downstream of the cavitation erosion zone was analysed. By observing the streamlines downstream of the cavitation structures, it was found that vortices form in the flow and redirect the particles towards the wall, causing a pure particle erosion zone on the wall. Particles under consideration in this study were not found to alter the flow to the extent that the cavitation erosion zone would be significantly altered compared with the results without solid particles which are reported in the literature.
Keywords: cavitation, Particles ANSYS Fluent, erosion, CFD, modelling, DPM
Published in DKUM: 30.10.2023; Views: 282; Downloads: 8
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Abstract: V okviru diplomskega dela se je izvedla katalitična piroliza LDPE – polietilena nizke gostote – v eksperimentalnem šaržnem reaktorju, v šaržah po 100 g. Izvedene so bile tri meritve brez dodatka katalizatorja, tri meritve z dodatkom 5 g katalizatorja in tri meritve z dodatkom 10 g katalizatorja. Kot katalizator se je uporabljal zeolit ZAP USY. Dodatek katalizatorja je pričakovano povišal delež plinskega produkta. Prav tako se je znižala temperatura ob prvih kapljicah kondezata. Pirolizno olje se je zbiralo v frakcijah po 9 g, saj smo želeli ugotoviti vpliv časa zadrževanja. Pri pirolizi brez katalizatorja so najtežje frakcije nastale ob najdaljših zadrževalnih časih. Ob dodatku katalizatorja pa so bile najtežje prve frakcije
Keywords: katalitična piroliza, zeolit ZAP USY
Published in DKUM: 09.10.2023; Views: 440; Downloads: 33
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Abstract: V diplomski nalogi je zajet izračun tehnoloških strojnih instalacij, potrebnih za delovanje tiskarskega stroja. Izveden je izračun hladilne vode, plinske instalacije, izkoriščanje odpadne toplote, odvod dimnih plinov, mehke tehnološke vode, komprimiranega zraka in odsesavanja papirnih in prašnih delcev. Preverjeno je tudi obstoječe prezračevanje hale, predvsem zaradi zračne bilance. Na podlagi izračunov narisane so ustrezno dimenzionirane vse potrebne strojne instalacije. Rezultat pravilne analize zahtev tiskarskega stroja je predstavljen skozi obratovanje brez velikih izgub, minimalni stroški in visoka stopnja učinkovitosti.
Keywords: tehnološke instalacije, izračun tehnoloških instalacij, tiskarski stroj
Published in DKUM: 05.10.2023; Views: 373; Downloads: 29
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