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Numerical simulation of pollutant dispersion from stationary industrial sources in urban environment
Get PDFTrend povećanja koncentracije onečišćujućih tvari u okolišu dovodi do negativnog utjecaja za zdravlje ljudi i organizme. Razvojem tehnologije čovjek je u mogućnosti smanjiti i pratiti koncentraciju onečišćujućih tvari u okolišu te time ujedno reducirati negativni utjecaj na prirodu čemu svakodnevno svjedočimo. Tema ovog rada odnosi se upravo na korištenje numeričkih metoda kako bi se mogli proučavati i rješavati problemi vezani za ekologiju u naseljenim mjestima.
U ovom radu se upotrebom računalne dinamike fluida proučava disperzija onečišćujućih tvari iz nepokretnih industrijskih izvora u urbanoj sredini grada Siska tijekom jednog karakterističnog dana. Podaci za ulazne emisije u domeni dobivene su za TE-TO Sisak i INA Rafineriju Sisak. Nadalje, u domeni je zadan i ulaz vjetra s bočnih strana čiji su podaci preuzeti iz numeričkog sustava za atmosferska istraživanja i prognoze vremena. Dobiveni rezultati simulacije prikazuju dimne perjanice i koncentracije na različitim visinama od tla za SO2 i NO. Na kraju valja istaknuti kako se tijekom niti jednog simuliranog sata ne premašuje granična vrijednost emisija za SO2 u naseljenom dijelu grada, čime se kakvoća zraka s obzirom na koncentracije SO2 ocjenjuje zadovoljavajućom.The trend of increasing concentrations of pollutants in the environment leads to a negative impact on human health and organisms.With the development of technology, people are able to reduce and monitor the concentration of pollutants in the environment, and at the same time reduce the negative impact on nature, which we witness daily.The topic of this thesis deals with application of numerical methods to study and solve environmental problems in populated areas.
In this thesis, computational fluid dynamics is used to study the dispersion of pollutants from stationary industrial sources in the urban environment of the city ofSisak during one characteristic day. Data for inlet domain emissions were obtained for TE-TO Sisak and INA RafinerijaSisak. Furthermore, the wind input at the domain sides is also prescribed, and the data were taken from the numerical system for atmospheric research and weather forecasts.The simulation results show smoke plumes and concentrations at different heights from the ground for SO2 and NO.Finally, it should be noted that during any simulated hour the emission limit for SO2 in the populated part of the city is not exceeded,makingthe air quality satisfactory with respect to SO2 concentrations
Effect of subsequent heating on the microstructure and mechanical properties of Nb microalloyed steel
No full textEffect of subsequent heating on the microstructure and mechanical properties of hot rolled niobium microalloyed steel was researched in this paper. Low carbon steel was microalloyed with 0.048 % niobium and it was heated at 1150 C followed by cooling in the air. Researches were performed on two types of samples: low carbon steel microalloyed with niobium and subsequently heated microalloyed steel in the rolling direction as well as in the direction perpendicular to the rolling direction. Mechanical properties of all samples were determined by the static tensile test at testing rate of 5 mm/min. After that their microstructure was observed by scanning electron microscope. Results have shown a significant effect of subsequent heating on the microstructure, i.e. grain size as well as on the mechanical properties
Synthesis of Ti-Zr alloy by powder metallurgy
Get PDFDue to good properties, which meet the requirements for use as biomaterials, titanium and titanium alloys have been increasingly used as dental implants. Until recently, dental titanium alloys were produced by casting. Since this process does not meet the terms of economy and efficiency, the production of titanium implants by powder metallurgy are very promising. Therefore, in this work titanium alloy with addition of 10 at. % zirconium is prepared by powder metallurgy with the goal of obtaining the best producing conditions, which would result in the titanium alloy of the adequate properties for use as dental implants. High values of green densities were achieved even only by uniaxial pressing. Further, sintering temperature of 1673 K resulted in the alloy of the highest sintered density and microhardness. The results of this investigation revealed the processing parameters applicable for the production of titanium-zirconium dental implants by powder metallurgy
Microstructure and properties of ductile iron alloyed with silicon and molybdenum
Get PDFU ovom diplomskom radu analizirana je mikrostruktura i ispitana su vlačna
svojstva, tvrdoća, žilavost i otpornost na oksidaciju na 850 °C nodularnih ljevova legiranih
sa 4,28, 4,49 i 4,81 mas. % Si i 0,6 mas. % Mo. Pored toga, ispitana je otpornost na
oksidaciju na 850 °C feritnog nodularnog lijeva sa 2,11 mas. % Si i od feritno-perlitnog
nodularnog lijeva sa 3 mas. % Si. U analiziranim SiMo nodularnim ljevovima grafitne
čestice imaju nodularni oblik. Metalna osnova sastoji se od ferita i malog udjela
globularnog perlita koji je izlučen po granicama feritnih zrna i okružuje karbide
molibdena. S porastom udjela silicija povećava se granica razvlačenja, vlačna čvrstoća,
omjer Rp0,2/Rm i tvrdoća, a smanjuje istezanje i žilavost SiMo nodularnih ljevova jer se
povećava intenzitet očvršćivanja ferita. Karbidi molibdena negativno utječu na istezanje i
žilavost SiMo nodularnog lijeva. Analizirani SiMo nodularni ljevovi imaju znatno bolju
otpornost na oksidaciju na 850 °C od feritnog nodularnog lijeva sa 2,11 mas. % Si i od
feritno-perlitnog nodularnog lijeva sa 3 mas. % Si. Otpornost na oksidaciju nodularnog
lijeva povećava se s porastom udjela silicija.This graduate thesis analyses the microstructure, tensile properties, hardness, toughness
and oxidation resistance at 850 ° C of ductile irons alloyed with 4.28, 4.49 and 4.81 wt. %
Si and 0.6 wt. % Mo. In addition, oxidation resistance at 850 ° C of ferritic ductile iron
containing 2.11 wt. % Si and ferritic-pearlitic ductile iron containing 3 wt. % Si was also
examined. In the analysed SiMo ductile irons, the graphite particles have a nodular shape.
The metallic matrix is composed of ferrite and a small share of globular pearlite which is
present on the grain boundaries of ferrite and surrounds the molybdenum carbides. With
the increase in silicon content, yield strength, tensile strength, ratio Rp0,2/Rm and hardness
increases, and the elongation and toughness of SiMo ductile irons decreases due to increase
in intensity of strengthening of ferrite. Molybdenum carbides negatively affect elongation
and toughness of SiMo ductile irons. Analysed SiMo ductile irons have a much better
oxidation resistance at 850 ° C than the ferritic ductile iron containing 2.11 wt. % Si and
from the ferritic-pearlitic ductile iron containing 3 wt. % Si. The oxidation resistance of
ductile iron increases with increasing silicon content
The effect of microwave drying on immobilization of photocatalyst on a carrier
Get PDFJedan od prioriteta zaštite okoliša je zaštita voda i vodenih tokova. Ovim problemom znanost se već dugo bavi, ali konstantno se pokušava inovativnim i poboljšanim metodama podići pročišćavanje voda na novu razinu. Pojava mikroonečišćujućih tvari u pročišćenim otpadnim vodama te vodama za piće pobudila je interes kod znanstvenika u pronalasku rješenja za njihovo uklanjanje. Primjer takvog procesa je fotokataliza kod koje dolazi do potpune razgradnje mikroonečišćivala odnosno nastajanja neopasnih razgradnih produkata. U tu svrhu koriste se fotokatalizatori kao što je titanijev dioksid (TiO2).
U radu je kao nosač za imobilizaciju TiO2 korištena staklena mrežica. Imobilizacija TiO2 na staklenu mrežicu je provedena sol-gel metodom uz dva različita načina sušenja; klasičnim i mikrovalnim sušenjem na različitim snagama. Provedena je karakterizacija dobivenih fotokatalizatora pretražnom elektronskom mikroskopijom (SEM), energijsko disperzivnom rendgenskom spektroskopijom (EDS) i rendgenskom difrakcijskom analizom (XRD). Dobiveni rezultati SEM/EDS analize ukazuju da je došlo do vezanja čestica koje su prilikom sušenja mikrovalovima većih dimenzija te da pripadaju TiO2. Iz XRD rezultata se može zaključiti da prisutnost amorfne faze silana smanjuje relativni udio anatasa i rutila te utječe na smanjenje specifične površine. Najbolji rezultati fotokatalitičke razgradnje salicilne kiseline dobiveni su korištenjem mrežice pripravljene klasičnim sušenjem što je i u korelaciji s navedenim rezultatima.One of the priorities of environmental protection is the protection of water and water flows. With this problem, science has long been involved, but it is constantly trying to innovate and improve methods to raise water cleaning to a new level. The emergence of micro-pollutants in cleaned wastewaters and drinking water inspired the interest of scientists in finding solutions of their removal. An example of such a process is photocatalysis, which results in complete decomposition of micro-pollutants or the formation of non-hazardous degradation products. Photocatalysts such as titanium dioxide (TiO2) are used for this purpose.
In this work a glass mesh was used as an immobilizer for TiO2. The immobilization of TiO2 on the glass mesh was carried out by the sol-gel method with two different drying methods; classic and microwave drying using different powers. Characterization of photocatalysts was obtained by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis (XRD). The results of the SEM/EDS analysis indicate that particles with big dimensions have been attached to glass mesh which is dried with microwaves and it belong to TiO2. From the XRD results it can be concluded that the presence of the amorphous silane phase reduces the relative proportion of anatase and rutile and affects the reduction of the specific surface. The best results of photocatalytic degradation of salicylic acid were obtained using a mesh prepared using classical drying, which is also correlated with results
Impact of multi wall carbon nanotubes of photocatalytic properties of TiO2
Get PDFSve veća uporaba lijekova, pesticida i drugih sliĉnih proizvoda utjeĉe na oneĉišćenje vode. Takvi proizvodi spadaju u mikrooneĉišćenja koja zahtijevaju posebne uvijete proĉišćavanja. Jedan od naĉina proĉišćavanja su napredni oksidacijski procesi u koje spada i fotokazaliza. Za proces fotokatalize potrebna je prisutnost fotokatalizatora, jedan od fotokatalizatora koji se koristi u fotokatalizi je TiO2. Za poboljšanje svojstava TiO2 mogu se koristiti razliĉiti elementi, spojevi i ugljikove nanocijevi.
U radu su pripremljeni fotokatlizatori TiO2 i TiO2/višestjene ugljikove nanocijevi s razliĉitim udjelima nanocijevi nanošenih sol-gel postupkom na staklenu mrežicu. Uspješno vezanje fotokatalizatora na staklenu mrežicu potvrĊeno je vizualno i SEM/EDS analizom. Ispitana su fotokatalitiĉka svojstva razgradnjom salicilne kiseline u reaktoru sa simuliranim sunĉevim zraĉenjem. UtvrĊeno je da udio od 5 % ugljikovih nanocijevi daje najbolje rezultate razgradnje salicilne kiseline fotokatalizom.The increasing use of medicines, pesticides and other similar products is affecting water pollution. Such products belong to microimpurities that require special purification conditions. One of the methods of purification is advance oxidation processes, which include photocatalysis. Photocatalysis requires the presence of photocatalysts, one of the photocatalysts used in photocatalysis is TiO2. Various elements, compounds and carbon nanotubes can be used to improve the properties of TiO2.
In this paper photocatalysts from TiO2 and TiO2/multi walled carbon nanotubes with different proportions of nanotubes deposited by sol-gel process on a glass mesh has been prepared. The successful bonding of the photocatalyst to the glass mesh was confirmed visually and by SEM/EDS analysis. The photocatalytic properties were examined by decomposing salicylic acid in reactor with a simulated solar radiation. It was established that 5 wt.% of carbon nanotubes gave the best results for the degradation of salicylic acid by photocatalysis
Energy effieciency of aluminium melting and holding furnaces
Get PDFU ovome radu analizirana je energijska uĉinkovitost peći za taljenje aluminija te mogućnost povećanja energijske uĉinkovitosti na peći za drţanje taline aluminija u talionici aluminija CIAL d.o.o. U teorijskom dijelu opisane su peći za taljenje aluminija te njihov naĉin rada. Detaljnije je opisana izmjena topline u peći tijekom taljenja, proces izgaranja te problematika peći uzimajući u obzir utjecaj tih procesa na energijsku uĉinkovitosti peći. U eksperimentalnom dijelu, u svrhu analize energijske uĉinkovitosti peći za taljenje aluminija, prikazan je utjecaj temperature izlaznih dimnih plinova i viška kisika na uĉinkovitost izgaranja, a u svrhu analize energijske uĉinkovitosti peći za drţanje taline aluminija analizirana je uĉinkovitost izgaranja u odnosu na temperaturu dimnih plinova za razliĉite sadrţaje kisika u zraku sa ili bez predgrijanja zraka. Za obje peći napravljena je i ekonomska analiza potrošnje energenata.This paper analyses the energy efficiency of aluminium melting furnace and the possibility of increasing the energy efficiency of aluminium holding furnace in an aluminium smelter CIAL d.o.o. Theoretical part describes the aluminium melting furnaces and their operation, as well as heat exchange in the furnace during melting, combustion process and furnace problems considering the impact of these processes on the energy efficiency of the furnace. In the experimental part the effect of the temperature of the exhaust flue gases and excess oxygen on the combustion efficiency is shown for the purpose of energy efficiency analysis of an aluminium melting furnace. Moreover, combustion efficiency in relation to the flue gas temperature for different oxygen contents in the air with or without air preheating was analysed for energy efficiency analysis of an aluminium holding furnace . Finally, an economic analysis of energy consumption was made for both furnaces
Study on strengthening during cold drawing of steel tubes
No full textStudy on strengthening during cold drawing was carried out on the samples taken from the steel tube before and after the cold drawing on drawing bench. Low carbon steel tubes were previously prepared and cold- drawn through the drawing dies with a different degree of reduction. During the process, the process is stopped and samples were taken in front of deformation zone, in the zone itself and behind the deformation zone. Detailed measurements on changes in the hardness and microstructure in the deformation zone were performed. The effect of the degree of deformation on the strengthening of the tested steel during the cold drawing was determined
Corrosion behavior of CuAlMn and CuAlMnNi alloy in 0.9% NaCl solution
Get PDFCorrosion behavior of CuAlMn and CuAlMnNi alloy ribbons, produced by melt spinning method, were investigated by electrochemical methods such as open circuit potential measurement, linear and potentiodynamic polarization method. Investigations were performed in deaerated 0.9% NaCl solution (T = 37 °C pH = 7.4). Results of electrochemical investigations have shown that CuAlMnNi alloy have higher values of polarization resistance and smaller values of corrosion current density, but in higher anodic potentials region anodic current density for CuAlMn is lower than for CuAlMnNi alloy which indicates higher dissolution of CuAlMnNi alloy. After polarization measurements CuAlMn and CuAlMnNi ribbon surfaces were investigated with light microscope and with SEM/EDS analysis and results have shown that CuAlMnNi alloy is prone to pitting corrosion, while the surface of CuAlMn alloy is partially covered with corrosion product without existence of pits
The effect of charge composition, casting section thickness and inoculation on gray cast iron microstructure
Get PDFU ovom diplomskom radu je analiziran utjecaj različitih sastava uloška za izradu
taline, debljine stijenke odljevka i cijepljenja na mikrostrukturu sivog lijeva. Izrađene su 3
taline sivog lijeva gotovo istog kemijskog sastava. Korišteni su sljedeći udjeli sirovog željeza
(SŽ), čeličnog otpada (ČO), povratnog sivog lijeva (PSL) i SiC u ulošku: talina 1 (39,4 % SŽ,
10 % ČO, 49,2 % PSL, 0,6 % SiC), talina 2 (9,9 % SŽ, 38,8 % ČO, 47,9 % PSL, 1,6 % SiC) i
talina 3 (0 % SŽ, 0 % ČO, 99,2 % PSL, 0,06 % SiC). Od svake taline odlivena su 2 stepenasta
odljevka sa stijenkama debljina 5, 10, 20, 45 i 65 mm, jedan necijepljen i jedan cijepljen
(dodatak cjepiva u mlaz taline tijekom ulijevanja u kalup iznosio je 0,23 mas. %). Dobiveni
rezultati pokazuju da tip, veličina i raspodjela grafitnih listića u analiziranim stijenkama nisu
u značajnijoj mjeri ovisili o sastavu uloška. Debljina stijenke imala je veliki utjecaj na tip,
veličinu i raspodjelu grafitnih listića, izlučivanje karbida te strukturu metalne osnove. S
povećanjem debljine stijenke mijenja se tip grafitnih listića od D i E preko B do A tipa.
Karbidi su pronađeni u rubnom dijelu stijenke debljine 5 mm. Udio ferita u metalnoj osnovi
povećavao se sa smanjenjem brzine hlađenja te sa povećanjem udjela grafitnih listića D i E
tipa. Cijepljenjem je značajno smanjen udio karbida u rubnom dijelu stijenke debljine 5 mm.
U sredini stijenke debljine 5 mm te stijenkama debljine 10 do 65 mm cijepljenjem je povećan
udio grafitnih listića A tipa te su eliminirani grafitni listići B, D i E tipa ili je njihov udio
značajno smanjen (učinak ovisi o debljini stijenke).The effect of different charge compositions for melt production, casting section
thickness and inoculation on the gray cast iron microstructure was analysed in this graduate
thesis. Three gray cast iron melts of almost the same chemical composition were made. The
following shares of pig iron (PI), steel scrap (SS), gray iron return (GIR) and SiC in charge
were used: melt 1 (39.4 % PI, 10 % SS, 49.2 % GIR, 0.6 % SiC), melt 2 (9.9 % PI, 38.8 %
SS, 47.9 % GIR, 1.6 % SiC) and melt 3 (0 % PI, 0 % SS, 99.2 % GIR, 0.06 % SiC). Two
stepped castings with walls thicknesses of 5, 10, 20, 45 and 65 mm are casted from each melt,
one uninoculated and one inoculated (the addition of inoculant in the melt stream during the
pouring in the mold was 0.23 wt.%). The obtained results show that the type, size and
distribution of graphite flakes in the analysed walls did not significantly depend on the
composition of the charge. The wall thickness had a great influence on the type, size and
distribution of graphite flakes, carbides precipitation and the structure of the metal matrix.
The type of graphite flakes is changed from D and E, over B to A type with increasing wall
thickness. Carbides were found in the edge part of the wall thickness of 5 mm. The percentage
of ferrite in the metal matrix increased with decreasing the cooling rate and with increasing
the proportion of graphite flakes D and E type. Inoculation significantly reduced the
proportion of carbides in the edge part of the wall thickness of 5 mm. In the middle of the
wall thickness of 5 mm and the walls thicknesses of 10 to 65 mm the inoculation resulted in
an increase in the proportion of graphite flakes A type. In addition, the graphite flakes B, D
and E types were eliminated or their proportion was significantly reduced (effect depends on
the wall thickness)