Repository of Faculty of Chemical Engineering and Technology University of Zagreb
Not a member yet
2768 research outputs found
Sort by
Development of soft sensors for monitoring the operation of process analyzers
No full textU ovom diplomskom radu predstavljen je razvoj dinamičkih modela softverskih senzora za praćenje rada online procesnog analizatora za mjerenje količine sumpora u proizvodu procesa hidrodesulfurizacije dizelskog goriva. Jedan od važnih koraka u razvoju softverskih senzora bio je odabir i statistička obrada kontinuirano mjerenih podataka dobivenih s postrojenja. Primjenom metoda identifikacije procesa razvijeni su dinamički polinomni linearni modeli: model konačnog impulsnog odziva, FIR (engl. finite impulse response), model temeljen na autoregresiji sa egzogenim ulazima, ARX (engl. autoregressive with exogenous inputs) te model izlazne pogreške, OE (engl. output error). Razvijeni su i dinamički nelinearni modeli: nelinearni model temeljen na autoregresiji s egzogenim ulazima, NARX (engl. nonlinear autoregressive with exogenous inputs) i Hammerstein-Wiener (HW) model. Različitim postupcima vrednovanja modela provjerena je valjanost razvijenih modela. Najmanja odstupanja modela od eksperimentalnih podataka pokazali su ARX i OE modeli te se oni mogu koristiti za kontinuiranu procjenu količine sumpora u proizvodu procesa hidrodesulfurizacije dizelskog goriva. Svrha razvijenih modela softverskih senzora je praćenje rada procesnih analizatora i potencijalno korištenje u svrhu zamjene procesnih analizatora prilikom njihovog održavanja ili dužeg kvara uređaja.This master’s thesis demonstrates the development of dynamic models of soft sensors to monitor the operation of on-line process analyzers for measuring the sulfur content in the product of the hydrodesulfurization process of diesel fuel. The most important steps in the development of soft sensors were the selection and preprocessing of continuously measured data collected from the plant. Using process identification methods, dynamic polynomial linear models were developed: finite impulse response (FIR), autoregressive with exogenous inputs (ARX) and output error (OE) models, as well as dynamic nonlinear models: nonlinear autoregressive with exogenous inputs (NARX) and Hammerstein-Wiener (HW).
The performances of the developed models were tested by various model evaluation procedures. The models ARX and OE showed the smallest deviations from the experimental data and can be used for continuous estimation of the sulfur content in the product of the diesel fuel hydrodesulfurization process. The purpose of the developed soft sensor models is to monitor the operation of process analyzer and potentially replace it during maintenance or equipment failures
Forced degradation study of emtricitabine and ribavirin
No full textRazvoj brojnih farmaceutika i njihova primjena u medicini imaju značajan utjecaj na poboljšanje kvalitete ljudskog života. Nažalost, tijekom proizvodnje ili uslijed korištenja, dio farmaceutika dospijeva u okoliš zbog čega je bitno poznavati ponašanje farmaceutika u različitim ekosustavima. Pokazalo se da farmaceutici, njihovi metaboliti i razgradni (nus)produkti, ukoliko su prisutni u većim količinama, imaju dugoročne negativne učinke na ekosustave. Ponekad su metaboliti i razgradni produkti toksičniji od inicijalne molekule farmaceutika zbog čega je također potrebno poznavati puteve njihove razgradnje. Cilj ovog rada je bio provesti testove prisilne razgradnje emtricitabina i ribavirina tekućinskom kromatografijom visoke djelotvornosti te tako dobiti predodžbu što se zbiva s navedenim spojevima u okolišu. Emtricitabin i ribavirin podvrgnuti su neutralnoj, lužnatoj i kiseloj hidrolizi, fotolizi, prisilnoj razgradnji s oksidansom te termičkoj razgradnji. Za oba farmaceutika su razvijene i validirane HPLC metode. Za razvijene metode utvrđena je linearnost uz koeficijent determinacije veći od 0,99 te analitički povrat u granicama 70-130%. Preciznosti metoda su veoma dobre uz relativna standardna odstupanja manja od 2%.The development of various pharmaceuticals and their active use in medicine greatly improve the quality of people's lives. However, the intensive use of pharmaceuticals also has a bad side. Unfortunately, the production or use of pharmaceuticals releases certain amounts of these chemicals into the environment, so it is important to know the behavior of pharmaceuticals in different ecosystems. Pharmaceuticals, their metabolites, and degradation (by) products have been shown to have long-term adverse effects on ecosystems. Sometimes the metabolites and degradation products themselves are more toxic than the original pharmaceutical, so it is necessary to know the degradation pathways. The aim of this work was to conduct the forced degradation study on emtricitabine and ribavirin to see what is potentially happening with the above compounds in the environment. Emtricitabine and ribavirin undergo neutral hydrolysis, alkaline hydrolysis, acid hydrolysis, photolysis, forced degradation with an oxidizing agent, and thermal degradation. The LC methods were developed and validated for each pharmaceutical. For both methods developed, linearity was confirmed with a coefficient of determination greater than 0.99, and analytical recoveries were within 70-130%. The precisions of the methods were very good with relative standard deviations of less than 2%
Use of hydrogen for vehicle propulsion
No full textSvrha ovog rada je cjelovito istražiti i proučiti različite aspekte korištenja vodika kao održivog i učinkovitog goriva za pogon vozila. Vodik se smatra gorivom budućnosti, a ovaj se rad bavi metodama njegove proizvodnje, skladištenja, prijevoza i primjene, prednostima i nedostacima njegove upotrebe, kao i projektima kojima je cilj komercijalizacija vodika u prometnom sektoru. Opisane su različite vrste gorivnih članaka koji proizvode električnu energiju i sastavni su dio vozila budućnosti, njihov utjecaj na okoliš te je predstavljen napredak koji su imali tijekom povijesti, od slučajnog otkrića do danas. Sustavi na vodik imaju potencijal značajno smanjiti emisiju stakleničkih plinova i smanjiti ljudsku ovisnost o fosilnim gorivima. Shodno tome, imaju pozitivan utjecaj na okoliš, što je glavni razlog želje za širenjem vodikove ekonomije. Cijena automobila na vodik i samog vodika viša je u odnosu na benzin, dizel i današnje automobile, ali se očekuje da će s vremenom i budućim ulaganjima cijena pasti i postati konkurentna na tržištu.The purpose of this paper is to comprehensively investigate and study various aspects of using hydrogen as a sustainable and efficient fuel for vehicle propulsion. Hydrogen is considered the fuel of the future, and this paper deals with the methods of its production, storage, transportation and application, the advantages and disadvantages of its use, as well as projects aimed at the commercialization of hydrogen in the transport sector. Different types of fuel cells that produce electricity and are an integral part of the vehicles of the future are described, as well as their impact on the environment, and the progress they have had throughout history, from accidental discovery to the present day. Hydrogen systems have the potential to significantly reduce greenhouse gas emissions and reduce human dependence on fossil fuels. Consequently, they have a positive impact on the environment, which is the main reason for the desire to expand the hydrogen economy. The price of hydrogen cars and hydrogen itself is higher compared to gasoline, diesel and today's cars, but it is expected that over time and with future investments the price will decrease and become competitive in the market
Application of adsorption in water purification
No full textAdsorpcija je separacijska metoda koja se temelji na privlačnim silama između adsorbensa i adsorbata koji je u plinovitom ili kapljevitom stanju. Ovaj proces se koristi za uklanjanje malenih koncentracija tvari iz određenog plina ili otopine tako da se nečistoće vežu na kruti adsorbens. Cilj ovog rada bilo je definiranje fizikalno-kemijskih svojstava procesa adsorpcije, povezati proces adsorpcije sa tehnologijama pročišćavanja voda, te navesti glavne prednosti i nedostatke adsorpcije u obradi voda.Adsorption is a separation method based on attractive forces between adsorbent and adsorbate that is in a gaseous or liquid state. This process removes small concentrations of substances from a particular gas or solution so that impurities are bound to a solid adsorbent. The purpose of this work was to define the physicochemical properties of the adsorption process, to connect the adsorption process with water purification technologies and to state the main advantages and disadvantages of adsorption in water treatment
Preparation and characterization of PLA biocomposites reinforced with olive waste (wood and leaves)
No full textU današnjem svijetu uloga ambalažnog materijala je sve izraženija, a samim time predstavlja svojevrstan problem uzimajući u obzir kako nepravilno skladištenje ambalažnog materijala u okolišu dovodi do ekoloških katastrofa koje posljedično utječu i na ljudski život. Najveći problem predstavlja ambalažni materijal proizveden na bazi fosilnih goriva. Upravo je to razlog razvitka biorazgradivih polimernih materijala koji bi se proizvodili iz obnovljivih izvora te nakon njihove upotrebe razgrađivali pod utjecajem bakterija i mikroorganizama. Izvrsna alternativa polimerima dobivenim iz nafte je biopolimer na bazi polilaktidne kiseline (PLA) koji se uglavnom koristi kao ambalaža. Međutim, PLA karakterizira visoka krtost, malo istezanje pri lomu što ograničava njegovu široku primjenu. Miješanje s fleksibilnim plastifikatorima, kao što su poli-(etilen oksid) (PEO), polietilen glikol (PEG), trietil citrat (TEC), tributil citrat (TBC), acetil-tributil citrat (TBAC), jedan je od najboljih načina za omekšivanje PLA. Cilj ovog rada je razvoj „zelenog“ polimernog materijala, odnosno biokompozitnog materijala od PLA/otpad masline koji bi se mogao primjenjivati kao ambalažni materijal. Ispitivanja su provedena na dvije skupine biokompozita bez i s i plastifikatorom. Toplinska svojstva ispitana su primjenom diferencijalne pretražne kalorimetrije (DSC), informacije o kemijskom sastavu i strukturi uzorka dobivene su FTIR-ATR spektroskopijom, mehanička ispitivanja provedena primjenom rasteznog ispitivanja. Dobiveni FTIR, DSC rezultati kao i dobivena mehanička svojstva pokazuju da se trietil citrat (TEC) pokazao kao dobar plastifikator za PLA/MAS biokompozite, povećao je fleksibilnost i smanjio krtost biokompozita što je dobro za primjenu ovih biokompozita kao ambalažnih materijala.In today's world, the role of packaging material is increasingly pronounced, and at the same time it represents a kind of a problem, considering how improper storage of packaging material in the environment can lead to environmental disasters that consequently affect human life. The biggest problem is packaging material produced based on fossil fuels. This is exactly the reason for the development of biodegradable polymer materials that would be produced from renewable sources and after their use they could easily be degraded under the influence of bacteria and microorganisms. An excellent alternative to petroleum-derived polymers is the polylactic acid (PLA) biopolymer, mostly used in the packaging industry. However, PLA exhibits high brittleness and low elongationat break that limit the wide application. Blending with flexible plasticizers such as poly- (ethylene oxide) (PEO), polyethylene glycol (PEG), triethyl citrate (TEC), tributyl citrate (TBC), acetyl-tributyl citrate (TBAC), is one of the best ways to toughen PLA.). The aim of this work is the development of a "green" polymer material, respectively a biocomposite material from PLA/olive waste that could be used as a packaging material. The investigations were conducted on two groups of biocomposites without and with plasticizer. Thermal properties were investigated using differential scanning calorimetry (DSC), information on the chemical composition and structure of the biocomposite was obtained by FTIR-ATR spectroscopy, mechanical properties were performed using tensile tests. The obtained FTIR, DSC results as well as mechanical properties show that triethyl citrate (TEC) can be a good plasticizer for PLA/OLIV biocomposites, it increased the flexibility and reduced the brittleness of biocomposites, which is good for the application of these biocomposites as packaging materials
Assessment of the condition of coatings on steel under controlled air humidity and temperature
No full textModeran svijet koji poznajemo ne bi imao istu vizuru da se u njemu ne nalaze ogromne metalne konstrukcije koje su najčešće građene od čelika. Kako bi se održala njihova dugovječnost za naredne generacije, čelične konstrukcije se štite premazima koji im osiguravaju zadovoljavajuću zaštitu od korozije koja je prisutna na svakom koraku djelovanjem kemijskih i fizikalnih čimbenika odnosno biološkim agensima. Neki od čimbenika koji utječu na brzinu korozije su: temperatura i relativna vlažnost zraka. U ovom radu opisan je eksperiment koji je proveden kako bi se odredila djelotvornost zaštitnog premaza na čeliku pod utjecajem kontrolirane temperature i vlažnosti zraka. Eksperiment je proveden u laboratoriju korištenjem metode elektrokemijske impedancijske spektroskopije na četiri različita premaza. ReCorr® QCQ uređajem pratio se modul impedancije u ovisnosti o faznom kutu i frekvenciji nakon kondicioniranja premaza pri odabranoj temperaturi i vlažnosti zraka. Na temelju izmjerene impedancije i dobre ponovljivosti metode može se donijeti zaključak o tome koji je premaz najkvalitetniji te pri kojim uvjetima će doći do oštećenja premaza.The modern world as we know it would not have the same vision if it did not contain huge metal structures, which are mostly made of steel. In order to maintain their longevity for future generations, steel structures are protected with coatings that provide them with satisfactory protection against corrosion, which is present at every step due to the action of chemical and physical factors, i.e. biological agents. Some of the factors that affect the rate of corrosion are: temperature and relative humidity. This paper describes an experiment that was carried out to determine the effectiveness of a protective coating on steel under the influence of controlled temperature and humidity. The experiment was carried out in the laboratory using the electrochemical impedance spectroscopy method on four different coatings. The ReCorr® QCQ device was used to monitor the impedance modulus as a function of phase angle and frequency after conditioning the coating at the selected temperature and air humidity. Based on the measured impedance and the good reproducibility of the method, a conclusion can be made about which coating is of the highest quality and under which conditions the coating will be damaged
Rheological properties of PVP/PEG blends
No full textPolimerni materijali i njihova primjena vrlo je važna - upotrebljavaju se kao materijali od kojih se izrađuje velik broj različitih proizvoda koji se svakodnevno koriste. Čisti polimeri često ne zadovoljavaju određena svojstva koja su potrebna za njihovo specifično područje primjene. Zbog toga se vrlo često dodaju različiti aditivi koji poboljšavaju njihova svojstva. Drugi način poboljšavanja svojstava polimera jest priprava polimernih mješavina, iz dviju ili više polimernih komponenata. U ovom radu pripravljene su mješavine dvaju polimera –
poli(etilen-glikola) (PEG) i poli(vinil-pirolidona) (PVP) različitih masenih udjela pojedinih komponenata. Mješavine su pripravljene na dva načina - zamiješavanjem u vodenoj otopini i zamiješavanjem u talini, korištenjem Brabender gnjetilice. Mješavinama pripravljenim u otopini ispitivana su reološka svojstva, te su uzorci analizirani diferencijalnom pretražnom kalorimetrijom i termogravimetrijskom analizom. Mješavine u talini su ispitivane diferencijalnom pretražnom kalorimetrijom i termogravimetrijskom analizom. Na temelju dobivenih rezultata, izvedeni su zaključci o reološkim svojstvima mješavina kao i o njihovim toplinskim svojstvima.Polymer materials and their application are very important - they are used as a material from which a large number of different products are made that are used every day. Polymer materials often do not meet the properties required for their specific application. For this reason, various additives are often added to them to improve their properties. Another way to improve polymer properties is to prepare polymer blends from two or more pure polymer components. In this work, blends of two polymers - poly(vinyl-pyrrolidone) and poly(ethylene glycol) - were prepared in different mass ratios. The blends were prepared in two ways – by mixing the polymers in a water solution and by mixing the polymers in a melt with a Brabender kneader. The rheological properties of the blends prepared in solution were tested, and the samples were analyzed by differential scanning calorimetry and thermogravimetric analysis. The mixtures prepared in the melt were studied by differential scanning calorimetry and thermogravimetric analysis. Based on the results obtained, conclusions were drawn about the rheological and thermal properties of the blends
The preparation of γ-Al2O3 supported Mn3O4 catalyst
No full textU ovom radu pripremljen je Mn3O4 katalizator na nosaču od γ-Al2O3 metodom sušenja s raspršivanjem (eng. spray drying) iz vodene otopine aluminijeva nitrata nonahidrata i manganova(II) nitrata tetrahidrata, uz limunsku kiselinu kao kompleksator i amonijevu lužinu kao pH modifikator. Tako dobiveni uzorci i termički obrađeni uzorci karakterizirani su rendgenskom difrakcijskom analizom (XRD), infracrvenom spektroskopijom s Fourierovom transformacijom (FTIR), pretražnom elektronskom mikroskopijom s energijski razlučujućom rendgenskom spektroskopijom (SEM-EDS), diferencijalnom toplinskom i termogravimetrijskom analizom (DTA-TGA) i fizisorpcijom N2. Katalitička aktivnost pripremljenih katalizatora ispitana je katalitičkom oksidacijom toluena. XRD analiza pokazala je prisutnost amonijeva nitrata kod termički neobrađenih uzoraka koju je potvrdila i FTIR analiza. Kod termički obrađenih uzoraka potvrđena je prisutnost γ-, odnosno α-alumine ovisno o temperaturi termičke obrade. SEM-EDS analiza pokazala je da su dobiveni porozni uzorci s homogenom raspodjelom elemenata. Najveću katalitičku aktivnost pokazao je uzorak s najvećim udjelom mangana.In this paper, γ-Al2O3 supported Mn3O4 catalyst was prepared using the spray drying method. The samples were prepared from an aqueous solution of aluminum nitrate nonahydrate and manganese (II) nitrate tetrahydrate with citric acid as complexing agent and ammonium hydroxide as pH modifier. The samples thus obtained and thermally treated samples were characterized by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), differential thermal and thermogravimetric analysis (DTA-TGA) and by N2 physisorption. The catalytic activity of the prepared catalysts was tested in catalytic oxidation of toluene. XRD analysis showed the presence of ammonium nitrate in thermally untreated samples, which was also confirmed by FTIR analysis. In heat-treated samples, the presence of γ- or α-alumina was confirmed depending on the heat treatment temperature. SEM-EDS analysis showed that porous samples with a homogeneous distribution of elements were obtained. The sample with the highest amount of manganese showed the highest catalytic activity
Application of convolutional neural networks for time series modeling
No full textVisoke koncentracije dušikova dioksida (NO2) u zraku mogu ozbiljno utjecati na ljudsko zdravlje. Dugotrajno izlaganje ovoj onečišćujućoj tvari može uzrokovati ili pogoršati respiratorne probleme, uzrokujući bolesti kao što su astma i bronhitis. U ovom radu razvijene su 1D konvolucijske neuronske mreže s ciljem predviđanja koncentracija NO2 na urbaniziranom području grada Graza u Austriji. Za izradu modela korišten je programski jezik Python te pripadajuće biblioteke (Pytorch, Pandas, Numpy, itd.). Podatci su prikupljeni s mjerne postaje Zapad u Grazu. U svrhu optimizacije modela za predviđanje koncentracija NO2 ispitivana je različita kombinacija hiperparametara modela kao što su veličina vremenskog prozora kod vremenskih nizova, stopa učenja i regularizacijski član lambda. Za razvoj modela koristile su se meteorološke, temporalne i lag značajke. Podskupovi podataka uzimani su u različitim vremenskim periodima: podskup za učenje (treniranje) modela, 1.1.2014 do 15.3.2018, podskup za validaciju, 15.3.2018 do 15.3.2019 te testni skup, 15.3.2019 do 15.3.2020. Razvijeni modeli pokazali su dobru sposobnost generalizacije, a najbolji rezultat modela konvolucijske neuronske mreže postignut je sa vremenskim prozorom 12, stopom učenja 0,0001 i regularizacijskim članom lambda 0,1 te postiže koeficijent determinacije R^2=0,62. Usporedno je razvijen i model slučajnih šuma (engl. Random Forest) koji postiže koeficijent determinacije R^2=0,65.High concentrations of nitrogen dioxide (NO2) in the air can seriously affect human health. Long-term exposure to this pollutant can cause or exacerbate respiratory problems such as asthma and bronchitis. In this study, 1D convolutional neural networks were developed with the aim of predicting NO2 concentrations in the urban area of Graz, Austria. The Python programming language and corresponding libraries (Pytorch, Pandas, Numpy, etc.) were used to create the model. The data were collected from the West monitoring station in Graz. A combination of various hyperparameters, such as the size of the time window, the learning rate, and the regularization term lambda, was used for the optimization of the NO2 concentration model. The features used for modeling included meteorological, temporal, and lag features. Subsets of data from different time periods were taken: the training subset from 1.1.2014 to 15.3.2018, the validation subset from 15.3.2018 to 15.3.2019, and the test subset from 15.3.2019 to 15.3.2020. These models showed good generalization ability, with the best result achieved with a time window of 12, a learning rate of 0.0001, and a regularization term lambda of 0.1, achieving a coefficient of determination R^2=0.62.
A Random Forest model was also developed in parallel, achieving a coefficient of determination R^2=0.65
Analysis of archaeological excavations using destructive and non-destructive methods
No full textArheološki artefakti su od neprocjenjive važnosti, zbog toga je prilikom njihovih analiza poželjno koristiti nedestruktivne metode kemijske analize. Ponekad to ipak nije dovoljno te pribjegavamo korištenju destruktivnih metoda, kako bismo dobili više podataka o analiziranom artefaktu. U ovom radu analizirana su dva konkretna uzorka, rimska narukvica i fibula koje su pronađene na devastiranom arheološkom nalazištu u okolici Zagreba. Cilj je potvrditi jesu li narukvica i fibula brončane te postoji li mogućnost da su izrađene od rude na samom nalazištu artefakata, a koja je nepoznatog sastava. Prilikom uzorkovanja arheoloških artefakata korištena je mikrodestruktivna metoda anodnog uzorkovanja, a za analizu rude korištene su destruktivne i nedestruktivne metode. Utvrđeno je kako su narukvica i fibula izrađene od bronce, a priložena ruda je po sastavu uglavnom željezo, međutim ne može se sa stopostotnom sigurnošću potvrditi da su pronađeni artefakti izrađeni od rude pronađene na tom nalazištu.Archaeological artifacts are of inestimable importance, that is why it is preferable to use nondestructive methods of chemical analysis when analyzing them. Sometimes this is still not enough, so we resort to using destructive methods in order to obtain more data about the analyzed artifact. This paper deals with two specific samples that were analyzed, a Roman bracelet and a fibula, which were found at a devastated archaeological site in the vicinity of Zagreb. The goal is to confirm whether the bracelet and the fibula are bronze, and whether there is a possibility that they were made from ore at the artifact site itself, which is of unknown composition. When sampling archaeological artifacts, the microdestructive method of anodic sampling was used, and destructive and non-destructive methods were used for the ore analysis. It was established that the bracelet and the fibula were made of bronze, and the ore was mostly iron in composition, however, it cannot be confirmed with a hundred percent certainty that the artifacts found were made from the ore found at that site