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Řehulková, Blanka. "Studium titrace molekulárního kyslíku do dohasínajícího dusíkového plazmatu." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-316191.
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A huge number of experiments were carried out in the field of nitrogen post-discharges during the last 50 or 60 years and they were supported by many published theoretical works. Some papers were focused also on the nitrogen active discharge, post-discharge itself, or they focused mainly on the kinetic processes running during the post-discharge period. This experimental work shows how oxygen titration into post-discharge will influence nitrogen flowing post-discharge. Experimental data were obtained by optical emission spectrometry, Spectra were measured in the range 300 - 700 nm at laboratory temperature of 300K. Discharge current was kept constant at the value of 120 mA relating to the total discharge power of 145 W. Pressure was kept constant, too, at the value of 1000 Pa. The nitrogen of 99.9999 % purity (further purified by Oxiclear column) flow was adjusted at 0.8 l/min. Flow of oxygen (99.95 % purity) through he titration capillary introduced to post-discharge from down stream direction, was kept at 4 ml/min. Both gas flows were controlled by mass flow controllers. The optical emission spectrometer Jobin Yvon TRIAX 550 with 300 gr/mm grating equipped by liquid nitrogen cooled CCD detector was used for the spectra acquisition. The integration time of 1 s was used at all experiments. The position of titration tube end introduced into post discharge from the down stream side was set from 5 to 25 cm with respect to the end of the active discharge; the step of 1 cm was used. The optical emission spectra were measured at positions from 3 to 29 cm with respect to the active discharge end. The following nitrogen spectral systems were identified in the spectra: 1st positive, 1st negative and 2nd positive. Besides them, some bands of NO-beta system were found. The intensity profiles along the post discharge were obtained for selected vibrational spectral bands of these spectral systems and changes in the vibrational distributions of upper electronic states of these spectral systems were determined.
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Mazánková, Věra. "Spektroskopické studium dohasínajících výbojů v dusíku a jeho směsích." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2009. http://www.nusl.cz/ntk/nusl-233291.
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Presented thesis gives results obtained during the spectroscopic observations of post –discharges of the pure nitrogen plasma with small oxygen admixture and in the nitrogen – argon mixture and the effect of the pink afterglow in it. The DC discharge in the flowing regime has been used for the plasma generation. The decaying plasma was study by optical emission spectroscopy, mainly in the range of 300–800 nm. The first positive, second positive, first negative nitrogen spectral system and NO spectral systems were observed in measured spectra. The band head intensities of these bands have been studied in the dependencies on experimental conditions. Simultaneously, the relative vibrational populations on the given nitrogen states have been calculated. Two discharge tubes made from different materials (PYREX glass and QUARTZ glass) were used in the case of nitrogen plasma containing low oxygen traces (up to 0.2 %). These experiments have been carried out at two wall temperatures for the determination of the temperature effect on the post-discharge. The discharge tube around the observation point was kept at the ambient temperature (300 K) or it was cooled down to 77 K by liquid nitrogen vapor. The total gas pressure of 1 000 Pa and the discharge current of 200 mA were conserved for all these experiments. The relative populations of electronic states were calculated in the dependence on the post-discharge time. The dependencies on oxygen concentration were given, too. The results showed no simple dependence of vibrational populations on oxygen concentration. Generally, slight increase of neutral nitrogen states populations was observed with the increase of oxygen concentration. These observations were well visible due to the intensity of nitrogen pink afterglow effect that was well visible at all oxygen concentrations. The pink afterglow maximal intensity was reached at about 5–10 ms at the wall temperature of 300 K in the PYREX tube. The molecular ion emission was strongly quenched by the oxygen and as this was dominant process for the pink afterglow emission the pink afterglow effect disappears at oxygen concentration of about 2000 ppm. The temperature and wall material influences were observed, too. The post-discharge in nitrogen argon mixtures was studied only in the PYREX tube at the ambient wall temperature of 300 K. The power dissipated in an active discharge was constant of 290 kW. The experimental studies had two new parameters – total gas pressure (500 Pa – 5 000 Pa) and the argon concentrations that were varied in the range of 0–83 %. Also in this case the dependencies of relative intensities of the bands given above were obtained and further the relative populations of electronic states as a function of decay time, total gas pressure and on argon concentration were obtained. The pink afterglow effect was observed at all applied discharge powers and total gas pressures. At the highest argon concentrations, especially at lower pressure, the pink afterglow effect disappeared. The presented experimental work is one of the hugest sets of experiments in the nitrogen with oxygen traces and in nitrogen-argon mixtures. These data can be used as a very good fundament for the further studies using wide numeric modeling of the post-discharge kinetic processes.
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Olga, Govedarica. "Određivanje optimalnih uslova izvođenja procesa epoksidovanja biljnih ulja persirćetnom kiselinom." Phd thesis, Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, 2017. http://www.cris.uns.ac.rs/record.jsf?recordId=104159&source=NDLTD&language=en.
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Hemijskim transformacijama se iz biljnih ulja dobijaju vredni derivati, poput epoksidovanih biljnih ulja, koji sekoriste u hemijskoj i polimernoj industriji. Kvalitet, patime i primena epoksidovanih biljnih ulja, zavise odsadržaja epoksidnih grupa u derivatizovanom ulju, koji bitrebalo da je što veći. Kako epoksidne grupe nastajuoksidacijom dvostrukih veza u trigliceridima kaodominantnoj grupi jedinjenja u biljnim uljima, pogodnasirovina za epoksidovanje su visoko nezasićena ulja,kakvo je laneno.Proizvodnja epoksidovanih biljnih ulja zahteva izbortakvih procesnih uslova pri kojima bi se postigli štopotpunija konverzija dvostrukih veza i što većaselektivnost procesa u odnosu na epoksidnu grupu. Zato jekao cilj ove doktorske disertacije postavljeno određivanjeoptimalnih vrednosti procesnih uslova epoksidovanjalanenog ulja persirćetnom kiselinom formiranom in situ izsirćetne kiseline i 30% vodenog rastvora vodonikperoksida u prisustvu jonoizmenjivačke smole kaokatalizatora. Određivanje je izvedeno primenommetodologije odzivne površine, kao i korišćenjem u ovojdisertaciji predloženih kinetičkih modela ispitivanogreakcionog sistema, u oba slučaja sa maksimumomrelativnog prinosa epoksida kao funkcijom cilja.Ispitivanje uticaja procesnih uslova, i to temperature,molskog odnosa reaktanata, količine katalizatora i brzinemešanja, na tok procesa epoksidovanja je bilo osnov zadefinisanje graničnih vrednosti procesnih uslova unutarkojih je tražen maksimum prinosa epoksida. Oblast dugihvremena reagovanja, koja nije od interesa za industriju, jeizbegnuta adekvatnim izborom temperature.Pri optimalnim vrednostima procesnih uslovaepoksidovanja lanenog ulja, određenim primenommetodologije odzivne površine, postignuto je dobroslaganje očekivane i eksperimentalno određene vrednostimaksimalnog relativnog prinosa epoksida, sa odstupanjemod 3,28%.Za potrebe određivanja optimalnih uslova izvođenjaprocesa epoksidovanja biljnih ulja korišćenjem kinetičkihmodela, razvijena su tri pseudohomogena modelaispitivanog trofaznog multireakcionog sistema. Poredkinetike osnovnih reakcija formiranja persirćetne kiseline i reakcije epoksidovanja dvostrukih veza triglicerida biljnog ulja, kao i kinetike sporedne reakcije otvaranja epoksidnegrupe sa sirćetnom kiselinom, u predloženim modelima jeuzeta u obzir i raspodela sirćetne i persirćetne kiselineizmeđu uljne i vodene faze sistema. Opisan je i uticajmasno-kiselinskog sastava ulja, odnosno broja dvostrukihveza u masno-kiselinskim lancima triglicerida, na kinetikureakcija. Za koeficijent raspodele sirćetne kiseline izmeđutečnih faza reakcionog sistema predložena je empirijskakorelacija koja je dala dobro slaganje izračunatihvrednosti sa eksperimentalnim podacima. Kinetičkiparametri modela su određeni fitovanjemeksperimentalnih podataka o promenama količinadvostruke veze i epoksidne grupe sa vremenom izvođenjaprocesa epoksidovanja. Na osnovu statističkih pokazateljauspešnosti fitovanja eksperimentalnih podataka, potvrđenaje prepostavka da je pseudohomogeni model publikovan uliteraturi unapređen uzimanjem u obzir pomenutihfenomena raspodele komponenata reakcione smeše imasno-kiselinskog sastava sirovine pri modelovanjureakcionog sistema epoksidovanja biljnih uljapersirćetnom kiselinom.Korišćenjem predloženih pseudohomogenih modelareakcionog sistema za određivanje optimalnih uslovaizvođenja procesa epoksidovanja lanenog ulja in situformiranom persirćetnom kiselinom u prisustvujonoizmenjivačke smole, dobijeno je odstupanje od 5,51%očekivane od eksperimentalno određene vrednostirelativnog prinosa epoksida.Bolje slaganje predviđene sa eksperimentalno određenomvrednošću relativnog prinosa epoksida u kontrolnomeksperimentu je dobijeno primenom metodologije odzivnepovršine u poređenju sa korišćenjem kinetičkih modela priodređivanju optimalnih vrednosti procesnih uslova. To je iočekivano, s obzirom da regresiona jednačina korišćena uokviru metodologije odzivne površine bolje fituje relativniprinos epoksida. Standardna devijacija relativnog prinosepoksida za regresionu jednačinu je 8,9 puta niža od oneizračunate za kinetički model koji najbolje predviđaoptimalne procesne uslove epoksidovanja lanenog uljapersirćetnom kiselinom.Vegetable oils can be transformed into added valueproducts by various chemical modifications, such asepoxidation. The epoxidized vegetable oils have awide range of applications in the chemical andpolymer industry. The quality, and consequently theapplication, of epoxidized vegetable oil is influencedby the epoxy group content. Since the epoxy groupsare formed by the oxidation of double bonds intriglycerides, the main constituent of vegetable oils,highly unsaturated vegetable oils, such as linseedoil, are desirable raw materials.The manufacturing of epoxidized vegetable oilsrequires the optimization of the process conditionsin order to achieve complete conversion of doublebonds and high selectivity of the process in respectto the epoxy groups. Therefore, the aim of thisdoctoral thesis is to determine the optimal processconditions for the epoxidation of linseed oil withperacetic acid, formed in situ from acetic acid and30% hydrogen peroxide in the presence of an ionexchange resin as the catalyst. The optimal processconditions were determined by response surfacemethodology, as well as by using developed pseudohomogeneouskinetic models that describe theinvestigated reaction system. For both optimizationmethods, the relative epoxy yield was selected as anobjective function to be maximized.The effects of process conditions, such astemperature, molar ratio of reactants, catalystamount and steering speed, on the kinetics of theepoxidation were studied in order to defineconstraints for the optimization. To avoid longreaction times, which are not of interest inmanufacturing, an adequate temperature range wasselected. Under the optimized process conditions for theepoxidation of linseed oil, which were determinedby response surface methodology, good agreementbetween the calculated and experimentallydetermined relative epoxy yields was achievedwithin 3.28%.Three models describing the three-phase multireactionsystem of vegetable oil epoxidation withperacetic acid were developed and further used forthe optimization. The models are pseudohomogeneouswith respect to the catalyst. Besidesthe kinetics of the main reactions of peracetic acidand epoxy group formation, the models take intoaccount the side reaction of the epoxy group openingwith acetic acid. The partitioning of the acetic acidand peracetic acid between the oil and aqueousphases is considered. In two proposed models, theeffect of fatty acid composition on the kinetics of theprocess is also described by considering the numberof double bonds in the fatty acid chains. Thedeveloped empirical correlation for the partitioncoefficient for acetic acid between the liquid phasesshows good agreement between the calculated andexperimental data. The kinetic parameters of theproposed pseudo-homogeneous models weredetermined by fitting the experimentally determinedchanges of the double bond and epoxy groupamounts with reaction time of the epoxidation.Statistical values of the models` parametersdetermination confirmed the hypothesis that thepseudo-homogeneous model proposed in theliterature can be improved by considering thepartitioning phenomena and the effect of the oil fattyacid composition on the kinetics of the vegetableoils epoxidation with peracetic acid.Under the optimized process conditions for theepoxidation of linseed oil with peracetic acid formedin situ in the presence of the ion exchange resin,which were determined by using proposed pseudohomogeneousmodels, the experimentallydetermined relative epoxy yield was 5.51% lowerthan the calculated.Better agreement between the calculated andexperimentally determined values for the relativeepoxy yield, achieved under the optimal processconditions, is obtained when the response surfacemethodology (RSM) was applied as opposed towhen the kinetic models were used for thedetermination of the optimal process conditions.This is in accordance with better fitting of therelative epoxy yield by RSM regression equationthan by kinetics models. Standard deviation of therelative epoxy yield for RSM regression equation is 8.9 times lower than the standard deviation for themost successful kinetic model used for prediction ofthe optimal process conditions for the epoxidation ofthe linseed oil by peracetic acid.
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Voldánová, Michaela. "Studium kinetiky samouspořádávacího procesu kolagenu I." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2016. http://www.nusl.cz/ntk/nusl-240522.
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Collagen, the most abundant protein of connective tissues, in various forms has a wide applications due to their diverse biological and chemical properties. One of the forms are collagen hydrogels, which are considered very suitable material for applications in tissue engineering, because they are able to provide biodegradable scaffolds that its properties correspond with living tissues. These systems are used for example as scaffold for targeted drug delivery with controlled release, in combination with cells can be used for the regeneration and reconstruction of tissues and organs. Heating the aqueous solution of collagen leads to spontaneous self-assembly process to variously distributed fibrillar structures, which are at a later stage of fibrillogenesis prerequisite for creating a three-dimensional supporting network, which is the basic building block of the gel. The resulting properties of the hydrogel depend not only on its structure, but also on the conditions which cause self-assembly process. Hydrogels were performed at 37 ° C and physiological pH. Studied structural variable was the concentration of collagen. So far, for the research of self-assembly were used spectrometric methods, which only provide information about kinetics of morphogenesis. In this work to study the kinetics of collagen I self-assembly were used rheological methods, which additionally give information about viscoelastic properties of the resulting material. The obtained experimental data confirmed two-step process of collagen I fibrillogenesis consisting of nucleation and growth process. Rheological hydrogels collagen behaved as a nonlinear yield-pseudoplastic. An attempt was made to molecular interpretation of the results. Using two-parametric Avrami equation was determined the rate of self-assembly for each concentration of collagen and the value of Avrami exponent determining the shape of produced units. The prepared hydrogels were subjected to increasing shear stresses (strain amplitude, shear rate). Larger amplitudes leads to collapse of the hydrogel structure, which is able to again partially regenerated.
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Musabyimana, Martin. "Deammonification Process Kinetics and Inhibition Evaluation." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29364.
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A number of innovative nitrogen removal technologies have been developed to address the treatment challenges caused by stringent regulations and increasing chemical and energy cost. A major contributing factor to these challenges is the liquid stream originating from the process of dewatering anaerobically digested solids. This liquid, also knows as centrate, reject water or sludge liquor, can cause an increase of up to 25% in ammonia loading. The recently discovered anaerobic ammonia oxidation (anammox) process is a major breakthrough for treatment of these streams as it has the potential to remove up to 85% of nitrogen load without external carbon source addition. The anammox process is combined with another process that oxidizes half of the ammonia to nitrite (nitritation) in a separate reactor such as in the SHARON process, or in the same reactor such as in the DEaMmONification (DEMON) process. Despite intensive laboratory research for the last 10 years to fully understand these processes, there is still a high level of skepticism surrounding the implementation of full-scale systems. The reason for this skepticism could be due to frequent failures observed in the lab scale systems as well as reported slow bacterial growth. We think that this technology might be used more effectively in the future if process kinetics, inhibition and toxicity can be better understood.
This work focused on the DEMON process with a goal to understand the kinetics and inhibition of the system as a whole and the anammox process in particular. A DEMON pilot study was undertaken at the Alexandria Sanitation Authority (ASA) and had several study participants, including ASA, the District of Columbia Water and Sewer Authority (DCWASA), CH2M Hill Inc., Envirosim Ltd, the University of Innsbruck and Virginia Tech. We investigated the growth rate of anammox bacteria within a quasi-optimal environment. Laboratory-scale experiments were conducted to assess anaerobic ammonia oxidation inhibition by nitrite as well as aerobic ammonia oxidation inhibition by compounds present in the DEMON reactor feed, such as a defoaming agent, a sludge conditioning polymer, and residual iron from phosphorus removal practices.
The study revealed that the DEMON process can be efficiently controlled to limit nitrite accumulation capable of causing process inhibition. The target ammonium loading rate of 0.5 kg/m3/d was reached, and no upset was noticed for a loading up to 0.80 kg/m3/d with an HRT of 1.7 days. The ammonia removal efficiency reached an average of 76% while total nitrogen removal efficiency had an average of 52%. Most of the process upsets were caused by aerobic ammonia oxidation failure rather than anammox inhibition. Failure in ammonia oxidation affected pH control, a variable which is at the center of the DEMON process control logic. The pilot study is summarized in Chapter 3 of this Dissertation.
The low anammox maximum specific growth rate (µmax,An) as well as nitrite inhibition are historically reported to be the major process challenges according to the literature, but the degree to which each contributes to process problems differs widely in the literature. In this study, we estimated µmax,An by using the high F:M protocol commonly used for nitrifying populations. We also studied the effect of both short term and sustained nitrite exposure on anammox activity. In this study, µmax,An was estimated to be 0.017 h-1. The study results also suggest that anammox bacteria can tolerate a spike of nitrite-N at concentrations as high as 400 mg/L as long as this concentration is not sustained. Sustained concentrations above 50 mg/L caused a gradual loss of activity over the long term.
Finally, the inhibition of aerobic ammonia oxidizing bacteria (AerAOB) observed in the DEMON reactor was investigated using laboratory experiments and is reported in Chapter 6. AerAOB inhibition was, in most cases, the main reason for process upset. Compounds that were suspected to be the cause of the inhibition were tested. The study noticed that a defoaming agent, polymer and ferrous iron had some inhibiting properties at the concentrations tested.Ph. D.
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Davies, Matthew Lloyd. "Exploiting nonlinear kinetics to enhance process operability." Thesis, University of Leeds, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270897.
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Soural, Ivo. "Studium procesů v dohasínajícím plazmatu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2011. http://www.nusl.cz/ntk/nusl-233321.
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The decaying plasma was studied by the optical emission spectroscopy. DC discharge created at 45 – 200 mA in Pyrex and Quartz tubes in flowing regime was used. The emission of three nitrogen spectral systems (1st and 2nd positive and 1st negative) were studied in time evolution for pressures of 500 – 5 000 Pa at two wall temperatures – ambient and liquid nitrogen (150 K inside the decaying plasma). Results showed that all three nitrogen systems (respectively N2(B, v), N2(C, v) and N2+(B, v) states as their origins) had their population maxima called pink-afterglow in the afterglow part. These maxima decreased with the increase of pressure for all systems, and moved to the later decay time. Maxima increased with discharge current (respectively power) and moved to shorter time. Populations at temperature of 150 K were measured due to the experimental arrangement from 17 ms, only, and thus pink aftergow maximum wasn’t observed (only at 5 000 Pa some maximum was recognized). Populations were smaller at 150 K that populations measured at laboratory temperature at the middle decay time (50-100 ms). At the late time, the populations were higher at lower temperature at lower pressure. Higher shifts (in intensity and decaytime) of pink afterglow maxima were observed in Quartz tube in comparison with their values in Pyrex tube. Besides the populations, rotational temperatures of selected bands of three observed spetral systems (for 1st negative 0-0 band, 1st positive 2-0 band and for 2nd positive 0-2 band) were measured. Rotational temperatures were monitored from presumption that this kind of temperature is equal to temperature of neutral gas (at local thermodynamic equilibrium). Results from 1st negative and 1st positive system showed strong decreasing of rotational temperatures up to about 10 ms at post-discharge begin, then temperatures were constant up to 20 ms of decay time and after that they grew up. Temperatures increased with the increase of current. The part with decreased temperature correlated with pink-afterglow part of post-discharge. Unfortunately, rotational temperatures of 2nd positive system had bad reproducibility and the time profile shape was opposite. Experimental results were compared with numerical kinetic model created by group of prof. Vasco Guerra at Instituto Supetior Técnico in Portugal. Several sets of conditions for simulation at 500 and 1 000 K in active discharge were applicable for the calculation corresponding to the experiment. Comparison of numerical simulation and experimental data done for N2(B) state demonstrated that maxima populations in pink afterglow are depended on the temperature difference between active discharge and post discharge. Maxima populations were supposed in pink afterglow disappeared if the same temperatures in active and post discharges were supposed. Temperature in active discharge is higher at higher apllied power, as it was showed from rotational temperatures observation. The results clearly showed that real temperature profile must be included into the kinetic model.
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Abraham, Thomas Kannankara. "Kinetic bounds on attainability in the reactor synthesis problem." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1126791863.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xvi, 190 p.; also includes graphics (some col.). Includes bibliographical references (p. 182-190). Available online via OhioLINK's ETD Center
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Srđan, Rončević. "Karakterizacija bioremedijacionih procesa u zemljištu i podzemnim vodama zagađenim naftom i derivatima na lokalitetu Ratno ostrvo." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2007. https://www.cris.uns.ac.rs/record.jsf?recordId=16637&source=NDLTD&language=en.
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Predmet izučavanja ove disertacije je pasivna bioremedijacija naftom i derivatima nafte zagađenih podzemnih voda na lokalitetu Ratno ostrvo i pospešivanje procesa bioremedijacije zemljišta i podzemne vode zagađenih naftom i derivatima nafte na laboratorijskom postrojenju u ciljusanacije ugroženog lokaliteta.Praćenjem podzemnih voda granične zone izvorišta Ratno ostrvo i Rafinerije nafte utvrđeno je da je u podzemnoj vodi granične zone izvorišta Ratno ostrvo i Rafinerije nafte Novi Sad prisutan proces pasivnebioremedijacije, odnosno, da na pojavu ugljovodoničnog zagađenja u vodi sredina odgovara povećanjem brojnosti, pre svega, ugljovodonik-osidujućih i lipolitskih bakterija i bakterijske enzimatske aktivnosti, i dolazi do transformacije mineralnih ulja u polarna jedinjenja. U vodi većine praćenih objekata uočene su eksponencijalne i linearne funkcionalne zavisnosti bakterijske brojnosti i fosfatazne aktivnosti od koncentracije ugljovodoničnog zagađenja za koncentracije ukupnih ugljovodonika < 400 µg/l (najčešće < 200 µg/l). Visok nivo podzemnih voda i prisustvo dela zagađenja u gornjim slojevima zemljišta ukazuje nam na mogućnost primene fitoremedijacije navedenog područja, jer je deo zagađenja dostupan korenskom sistemu.Ispitivanjem tehničke bioremedijacije zemljišta i podzemne vode zagađenih naftom i derivatima nafte na laboratorijskom postrojenju utvrđeno je da dolazi do opadanja koncentracije ukupnih ugljovodonika u zemljištu sa 38,2 na 14,6 g/kg i mineralnih ulja sa 27,0 na 10,2 g/kg (62%), što se može definisati jednačinom C=C0e-kt, gde je konstanta brzine degradacije ugljovodonika k=0,0082 dan-1. U vodi je prisutan veliki broj karboksilnih kiselinanastalih oksidacijom alkana (C10-19), kao i aromata (benzoeva kiselina, kao i benzaldehid), što ukazuje na proces biooksidacije ugljovodonika. Proces rastvaranja i emulgovanja nafte se pospešuje uvođenjem recirkulacije vode: određena je jednačina zavisnosti koncentracije ugljovodonika u vodenoj fazi od koncentracije u čvrstoj fazi, zavisno od brzine proticanja: Cvoda=(f*v+K0)Czemlja, gde je koeficijent ispiranja f=1400 s/m, a difuzioni koeficijent K0=6*10-4. Proces ispiranja nafte i derivata sa zemlje značajno utiče na aktivnost mikroorganizama i razgradnju zagađenja. Sa porastom koncentracije ugljovodonika generalno opadaju brojnosti svih ispitivanih grupa bakterija i fosfatazna aktivnost i određene su granične vrednosti tolerancije. Proces ispiranja se mora voditi tako da koncentracija mineralnih ulja u vodenoj fazi netreba da pređe 15-35 mg/l, a kad se postignu koncentracije ugljovodonika manje od 400 µg/l treba prepustiti pasivnoj bioremedijaciji da ukloni zagađenje.This dissertation investigates the passivebioremediation of groundwater from Ratno Ostrvo contaminated by oil and oil derivatives, and a bench-scale experiment to improve the soil and groundwater bioremediation processes, with the goal of sanatising the effected area.During groundwater monitoring of the zone between the Ratno Ostrvo spring and the Novi Sad oil refinery, a passive bioremediation process was observed, whereby, in the hydrocarbons-contaminated water, increased counts of hydrocarbon-oxidising and lipolytic bacteria and increasing bacterial enzyme activity were found, along with the transformation of mineral oils to polar compounds. In water, the majority of the monitoring points displayed either exponential or linear functionalal dependence between bacterial count or phosphatase activity and hydrocarbon concentration, for total hydrocarbon concentrations < 400 µg/l (most often < 200 µg/l). The high groundwater level and the presence of contamination inthe upper soil layers makes possible the application of phytoremediation at the site, as part of the contamination is in the rhyzosphere.The bench-scale investigation of bioremediation in soil and groundwater contaminated by oil and oil derivatives yielded decreasing concentrations of total hydrocarbons in the soil from 38.2 to 14.6 g/kg and mineral oils from 27.0 to 10.2 g/kg (62%), which can be described by C=C0e-kt, where the rate constant of hydrocarbon degradation is k=0.0082 day-1.In water, a large number of carboxylic acids were present, from the oxidation of alkanes (C10-19) and aromatics (benzoic acid, and also benzaldehyde), which indicates a hydrocarbon biooxidation process. The process of dissolving and emulgating the oil is enhanced by recirculating the water: the linear relation between the concentration of hydrocarbons in the liquid and solid phases was found to be dependent on the flow rate: Cwater=(f*v+K0)Csoil, where the rinsing coefficient f=1400 s/m, and the diffusion coefficient K0=6 x 10-4. The process of rinsing the oil and oil derivatives from the soil significantly influences the microbial activity and the degradation of contaminants. With increasing hydrocarbon concentrations, there was generally decreasing bacterial counts and phosphatase activity, and an upper limit for hydrocarbon tolerance was determined. The rinsing process must becontrolled to ensure the mineral oil concentration in water does not exceed 15-35 mg/l, and once the concentration of hydrocarbons becomes less than 400µg/l, passive bioremediation may be left to complete the degradation.
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Křečková, Magdaléna. "Kinetika heterogenních procesů v technologii silikátů - dehydroxylace a rozpouštění jílových minerálů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2012. http://www.nusl.cz/ntk/nusl-233360.
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The first part of the thesis discuss general characterization of heterogeneous processes in silicates. This part is focused on kinetics of heterogeneous processes and mathematical description of reactions time behavior. The other part describes important technologies in silicate industry such as sintering, solid matter decomposition, transition modification, etc. Another chapter deals mineralogy, structure and properties of eminent silicate raw materials. Emphases is given to characterization of clay minerals and their utilising. The experimental part handle the analytic techniques used for investigation of thermal decompostion, dehydroxylation, crystalization of Al-Si spinel phase and sintering process of washed kaolin Sedlec Ia from the region Carlsbad (Czech Republic). Concluding chapter reports on results of experimental work.
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Sotelo-Boyas, Rogelio. "Fundamental kinetic modeling of the catalytic reforming process." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4670.
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In this work, a fundamental kinetic model for the catalytic reforming process has been
developed. The complex network of elementary steps and molecular reactions occurring in
catalytic reforming has been generated through a computer algorithm characterizing the
various species by vectors and Boolean relation matrices. The algorithm is based on the
fundamental chemistry occurring on both acid and metal sites of the catalyst.
Rates are expressed for each of the elementary steps involved in the transformation of the
intermediates. The Hougen-Watson approach is used to express the rates of the molecular
reactions occurring on the metal sites of the catalyst. The single event approach is used to
account for the effect of structure of reactant and activated complex on the rate coefficients
of the elementary steps occurring on the acid sites. This approach recognizes that even if
the number of elementary steps is very large they belong to a very limited number of types,
and therefore it is possible to express the kinetics of elementary steps by a reduced number
of parameters. In addition, the single event approach leads to rate coefficients that are
independent of the feedstock, due to their fundamental chemical nature. The total number
of parameters at isothermal conditions is 45. To estimate these parameters, an objective
function based upon the sum of squares of the residuals was minimized through the
Marquardt algorithm. Intraparticle mass transport limitations and deactivation of the catalyst by coke formation
are considered in the model. Both the Wilke and the Stefan-Maxwell approaches were used
to calculate the concentration gradients inside of the particle. The heterogeneous kinetic
model was applied in the simulation of the process for typical industrial conditions for both
axial and radial flow fixed bed reactors. The influence of the main process variables on the
octane number and reformate volume was investigated and optimal conditions were
obtained. Additional aspects studied with the kinetic model are the reduction of aromatics,
mainly benzene. The results from the simulations agree with the typical performance found
in the industrial process.
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Girard, Russell Douglas. "Kinetic study of an ethanol-water pulping process." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0027/NQ38347.pdf.
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Porter, Richard Thomas James. "Kinetic mechanism reduction for chemical process hazard application." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441227.
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Li, Huayu. "Process measurements and kinetics of unseeded batch cooling crystallization." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53503.
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This thesis describes the development of an empirical model of focus beam reflectance measurements (FBRM) and the application of the model to monitoring batch cooling crystallization and extracting information on crystallization kinetics.
Batch crystallization is widely used in the fine chemical and pharmaceutical industries to purify and separate solid products. The crystal size distribution (CSD) of the final product greatly influences the product characteristics, such as purity, stability, and bioavailability. It also has a great effect on downstream processing. To achieve a desired CSD of the final product, batch crystallization processes need to be monitored, understood, and controlled.
FBRM is a promising technique for in situ determination of the CSD. It is based on scattering of laser light and provides a chord-length distribution (CLD), which is a complex function of crystal geometry. In this thesis, an empirical correlation between CSDs and CLDs is established and applied in place of existing first-principles FBRM models. Built from experimental data, the empirical mapping of CSD and CLD is advantageous in representing some effects that are difficult to quantify by mathematical and physical expressions. The developed model enables computation of the CSD from measured CLDs, which can be followed during the evolution of the crystal population during batch cooling crystallization processes.
Paracetamol, a common drug product also known as acetaminophen, is selected as the model compound in this thesis study. The empirical model was first established and verified in a paracetamol-nonsolvent (toluene) slurry, and later applied to the paracetamol-ethanol crystallization system. Complementary to the FBRM measurements, solute concentrations in the liquid phase were determined by in situ infrared spectra, and they were jointly implemented to monitor the crystallization process.
The framework of measuring the CSD and the solute concentration allows the estimation of crystallization kinetics, including those for primary nucleation, secondary nucleation, and crystal growth. These parameters were determined simultaneously by fitting the full population balance model to process measurements obtained from multiple unseeded paracetamol-ethanol crystallization runs.
The major contributions of this thesis study are (1) providing a novel methodology for using FBRM measurements to estimate CSD; (2) development of an experimental protocol that provided data sets rich in information on crystal growth and primary and secondary nucleation; (3) interpretation of kinetics so that appropriate model parameters could be extracted from fitting population balances to experimental data; (4) identification of the potential importance of secondary nucleation relative to primary nucleation. The protocol and methods developed in this study can be applied to other systems for evaluating and improving batch crystallization processes.
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Arant, Charles. "Kinetic Problem Solving." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6997.
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Government leaders stand to benefit from improved program management capabilities within their organizations. Often, they are faced with crisis situations that require a rapid-fire, precise, effective problem solving process. Some of these programs are more severe or complex than others. With time and certainty of the solution as constraints, efficient program management supporting the Defense Acquisition Life Cycle remains an enigma for organizations at best and a hazard at worst.
Program management dealing with crisis problem solving, which is characterized by critical events and high cost, is a real-time process where requirements are identified and resolved to achieve a desired goal, with the path to the goal blocked by known or unknown obstacles. Program management that deals with crisis problem solving situations are plagued by several issues. The crisis situation is likely one not previously encountered; therefore, solutions from past experiences cannot be drawn upon to solve the problem (Heichal, 1992). An individual not experienced or trained often feels the situation is too complex, information is incomplete, time is short, and failure consequences are extreme (Hockey, 1986). Managers who face these dilemmas must have responsive, failure-proof processes in place.
This dissertation explores program management as it deals with problem solving processes in time-critical contexts, including task consolidation and resource selection, with the critical objective of improving crisis event management. The intent is to focus on processes that can be improved in crisis problem solving, specifically time needed to execute current problem solving processes, and introduce a kinetic problem solving approach to increase the momentum of implementing the solutions during crisis situations. This flexibility is facilitated by the researcher’s genuine desire to improve the organizational situation (rather than merely study it) and a client’s willingness to share the details of how they will use the technology and lessons learned.
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Göksu, Sermin Aktaş Ahmet Hakan. "Siyanisitler içeren gümüş cevherlerinin siyanür liçinde siyanisit-çözünme kinetiği ilişkisi ve gümüş çözünme veriminin artırılması /." Isparta : SDÜ Fen Bilimleri Enstitüsü, 2008. http://tez.sdu.edu.tr/Tezler/TF01135.pdf.
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Brad, Robert Boyd. "Reduced kinetic mechanisms for chemical and process engineering applications." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421444.
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Patel, Vinodkumar H. "Chemical kinetic investigation of a commercial batch reactor process." Thesis, Aston University, 1987. http://publications.aston.ac.uk/10185/.
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The aim of this investigation was to study the chemical reactions occurring during the batchwise production of a butylated melamine-formaldehyde resin, in order to optimise the efficiency and economics of the batch processes. The batch process models are largely empirical in nature as the reaction mechanism is unknown. The process chemistry and the commercial manufacturing method are described. A small scale system was established in glass and the ability to produce laboratory resins with the required quality was demonstrated, simulating the full scale plant. During further experiments the chemical reactions of methylolation, condensation and butylation were studied. The important process stages were identified and studied separately. The effects of variation of certain process parameters on the chemical reactions were also studied. A published model of methylolation was modified and used to simulate the methylolation stage. A major result of this project was the development of an indirect method for studying the condensation and butylation reactions occurring during the dehydration and acid reaction stages, as direct quantitative methods were not available. A mass balance method was devised for this purpose and used to collect experimental data. The reaction scheme was verified using this data. The reactions stages were simulated using an empirical model. This has revealed new information regarding the mechanism and kinetics of the reactions. Laboratory results were shown to be comparable with plant scale results. This work has improved the understanding of the batch process, which can be used to improve product consistency. Future work has been identified and recommended to produce an optimum process and plant design to reduce the batch time.
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Manhique, A. J. (Arao Joao). "Optimisation of alkali-fusion process for zircon sands: A kinetic study of the process." Diss., University of Pretoria, 2003. http://hdl.handle.net/2263/27817.
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Snežana, Maletić. "Karakterizacija biodegradabilnosti naftnih ugljovodonika u zemljištu i bioremedijacionih procesa u toku tretmana biogomilama i površinskom obradom." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2010. https://www.cris.uns.ac.rs/record.jsf?recordId=73221&source=NDLTD&language=en.
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U okviru ovog istraživanja ispitani su: (1) Procesi koji se odvijaju prilikom bioremedijacije zemljišta zagađenog naftom i derivatima nafte, koje je bilo izloženo spontanim abiotičkim i biotičkim procesima degradacije u toku 8 godina, tehnikama biogomila i površinske obrade na poluindustrijskoj (pilot) skali uz optimizaciju tehnoloških parametara sa ciljem povećanja efikasnosti i efektivnosti biodegradacije ugljovodonika; (2) Uticaj starenja, koncentracije, biodsotupnosti i strukture zagađujućih materija na procese biodegradacije i biotransformacije u kontrolisanim laboratorijskim uslovima. Tokom dve godine bioremedijacionog tretmana sadržaj mineralnih ulja opao je za 52% (od 27,8 g/kg do 13,2 g/kg) i 53% (od 23,2 g/kg do 10,8 g/kg), dok je sadržaj ukupnih ugljovodonika opao za 43% (od 41,4 g/kg do 23,4 g/kg) i 27% (od 35,3 g/kg do 25,8 g/kg) u biogomili i površinskoj obradi respektivno. Efikasnost uklanjanja mineralnih ulja iz zemljišta u dva posmatrana bioremedijaciona tretmana je praktično ista. Međutim, u pogledu sadržaja ukupnih ugljovodonika u biogomili uklonjeno je dva puta više ukupnih ugljovodonika (gledajući apsolutnu količinu ukupno uklonjenih ugljovodonika). Kinetika biodegradacije mineralnih ulja i ukupnih ugljovodonika u toku tretmana u biogomili u saglasnosti je sa kinetičkim modelima lnC=lnC0-kt i lnC=lnC0-kt0,5. Kinetika biodegradacije mineralnih ulja u toku površinske obrade relativno se dobro može opisati sa dva pomenuta kinetička modela, međutim, znatno bolju korelaciju pokazao je linearni model (C=C0-kt) primenjen na prvih 92 i poslednjih 200 dana eksperimenta. Promena sadržaja ukupnih ugljovodonika u toku površinske obrade zagađenog zemljišta relativno je u dobroj korelaciji samo sa kinetičkim modelom lnC=lnC0-kt0,5. Laboratorijska ispitivanja pokazala su da biodegradabilnost i sudbina ugljovodonika u životnoj sredini jako zavise od tipa, starosti i koncentracije zagađujućih materija. Naime, u slučaju zemljišta sveže kontaminiranog dizel uljem, već pri koncentracijama od 20 mg/g uočen toksičan efekat koji je prevaziđen nakon dve nedelje tretmana kao posledica smenjenja prekomerne koncentracije rastvorenih ugljovodonika biotičkim i abiotičkim putem i adaptacije prisutne mikroflore. U slučaju većih koncentracija ovaj efekat je bio još izraženiji. Kod zemljišta kontaminiranog sirovom naftom isti efekat se javlja tek pri koncentraciji od 35 mg/g, kao posledica toga da sirova nafta sadrži manju količinu lako rastvornih ugljovodonika. Za razliku od sveže kontaminiranog zemljišta, na biodegradaciju starog naftnog zagađanja u zemljištu koncentracija nije imala uticaj, u ovakvom zemljištu respiracija je bila na veoma niskom nivou pri svim ispitivanim koncentracijama, ali ne kao posledica toksičnosti, već kao posledica činjenice da se degradabilni deo zagađujućih materija degradirao tokom procesa starenja, tako da su u zemljištu zaostali visokomolekularni teško rastvorni ugljovodonici (smole, asfaltne komponente i dr.) sekvestrovani u zemljištu. Merenja biodostupnosti ugljovodonika (ekstrakcijom sa Tween80) pokazala su da je u zemljištu sveže kontaminiranom dizel uljem i sirovom naftom i starim naftnim zagađenjem oko 95%, 85% i 40% ugljovodonika biodostupno, respektivno. Koncentracija rezidualne frakcije mineralnih ulja i ukupnih ugljovodonika dobijena nakon 48 dana laboratorijskog tretmana u skoro svim probama je veća od predviđenih, što je posledica bifaznog ponašanja ugljovodonika u zemljištu, gde se jedan deo uklanja biodegradacijom, dok drugi deo difunduje u pore zemljišta i kompleksira se sa zemljišnom organskom materijom. Količina ugljovodonika iz starog naftnog zagađenja zemljišta koja može da pređe u vodenu fazu je mala reda veličine nekoliko mg/l, međutim, u prirodnim uslovima usled spiranja ugljovodonika sa zemljišta kišom, postoji verovatnoća da ovi ugljovodonici dospeju u podzemnu vodu iznad maksimalno dozvoljene koncentracije za vodu za piće (MDK = 10 μg/l) i na taj način degradiraju njen kvalitet. Zbog nemogućnosti daljag uklanjanja zagađenja bioremedijacijom, preostala količina zagađujućih materija koja može dospeti u vodenu fazu bi trebalo da se ukloni nekim drugim remedijacionim tehnikama pre njegovog konačnog bezbednog odlaganja u životnu sredinu.The aims of this study were to examine: (1) the processes that occur during bioremediation of soil contaminated by oil and oil derivatives, which was exposed to spontaneous abiotic and biotic degradation processes over 8 years, using pilot scale biopiles and landfarming techniques to optimise technological parameters with the aim of increasing the efficiency and effectiveness of hydrocarbons biodegradation. (2) the effect of contaminants weathering, concentration, bioavailability and structure on the biodegradation and biotransformation process under controlled laboratory conditions. Over the two years of bioremediation treatment by biopiles and landfarming, the mineral oil content decreased by 52% (from 27.8 g/kg to 13.2 g/kg) and 53% (from 23.2 g/kg to 10.8 g/kg), and the total hydrocarbon content decreased by 43% (from 41.4 g/kg to 23.4 g/kg) and 27% (from 35.3 g/kg to 25.8 g/kg), respectively. The efficiency of mineral oil removal from soil in these two applied bioremediation treatments was practically the same. However, in terms ofthe absolute amount of total hydrocarbons, twice as many total hydrocarbons were removed in the biopile. The mineral oil and total hydrocarbons biodegradation kinetics in the biopile were in good agreement with the kinetic models lnC = lnC0-kt and lnC = lnC0-kt0.5. The mineral oil biodegradation kinetics during the landfarming treatment is relatively well described with those two kinetic models, however, significantly better correlation is obtained by the linear model (C = C0-kt) applied to the first 92 and last 200 days of the experiment. The change in total hydrocarbons content during the landfarming treatment is in relatively good correlation only with the kinetic model lnC = lnC-kt0.5. The laboratory biodegradation investigation showed that hydrocarbon biodegradability and its fate in the environment strongly depend upon the structure, concentration and weathering of the hydrocarbons. Thus, in the case of diesel contaminated soil, as a consequence of its structure, i.e. the presence in a higher concentration of the soluble and toxic midrange n-alkanes, a toxic effect is detected at a diesel oil concentration of 20 mg/g, although this effect is overcome after two weeks, as a consequence of the decreasing concentration of soluble hydrocarbons in biotic and abiotic processes and microbial adaptation. This effect was more pronounced in the case of the soil withthe highest diesel oil concentration. In crude oil contaminated soil, a toxic effect was observed at a much higher hydrocarbon concentration (35 mg/g) than in the diesel oil contaminated soil, which corresponds to the fact that crude oil contains significantly less soluble hydrocarbon. In contrast to these two freshly contaminated soils, the weathered contaminated soil contaminant concentration did not have an effect on hydrocarbon biodegradation, with biodegradation in this soil actually at a low level at all concentrations, not as a consequence of toxicity, but because the degradable part of the contaminant was already degraded during the weathering process, leaving behind only highly condensed hydrophobic organic contaminants (asphaltenes, resins, etc.) sequestered in the soil. The data obtained for hydrocarbons bioavailability (by Tween80 extraction) showed that the bioavailable hydrocarbon fraction from soils freshly contaminated with diesel oil and crude and weathered oil contamination were approximately 95%, 85% and 40%, respectively. The concentration of residual mineral oil fractions and total hydrocarbons obtained after 48 days of laboratory biodegradability treatment in almost all batches was greater than predicted, as a result of the biphasic behaviour of hydrocarbons in the soil, where some were degraded or lost from the soil and some transformed into the recalcitrant fraction. The amount of hydrocarbons from the weathered soil contamination that can be transferred into the water phase is small, of the order of a few mg/l in magnitude, however, under natural conditions, due to hydrocarbons leaching by rainfall, it is possible that these hydrocarbons infiltrate groundwater above the maximum permissible concentration for drinking water (MAC = 10 μg/l) and thus degrade its quality. As it is not possible to achieve further contamination degradation by bioremediation, the remaining amount of pollutants which can be transferred into the water phase should be removed by some other remediation techniques before its final safe disposal in the environment.
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Haubrock, Jens. "The process of dimethyl carbonate to diphenyl carbonate: thermodynamics, reaction kinetics and conceptual process design." Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/58404.
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Tang, Yanyan. "Stereolithography Cure Process Modeling." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7235.
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Although stereolithography (SL) is a remarkable improvement over conventional prototyping production, it is being pushed aggressively for improvements in both speed and resolution. However, it is not clear currently how these two features can be improved simultaneously and what the limits are for such optimization.
In order to address this issue a quantitative SL cure process model is developed which takes into account all the sub-processes involved in SL: exposure, photoinitiation, photopolymerizaion, mass and heat transfer. To parameterize the model, the thermal and physical properties of a model compound system, ethoxylated (4) pentaerythritol tetraacrylate (E4PETeA) with 2,2-dimethoxy-2-phenylacetophenone (DMPA) as initiator, are determined. The free radical photopolymerization kinetics is also characterized by differential photocalorimetry (DPC) and a comprehensive kinetic model parameterized for the model material. The SL process model is then solved using the finite element method in the software package, FEMLAB, and validated by the capability of predicting fabricated part dimensions.
The SL cure process model, also referred to as the degree of cure (DOC) threshold model, simulates the cure behavior during the SL fabrication process, and provides insight into the part building mechanisms. It predicts the cured part dimension within 25% error, while the prediction error of the exposure threshold model currently utilized in SL industry is up to 50%. The DOC threshold model has been used to investigate the effects of material and process parameters on the SL performance properties, such as resolution, speed, maximum temperature rise in the resin bath, and maximum DOC of the green part. The effective factors are identified and parameter optimization is performed, which also provides guidelines for SL material development as well as process and laser improvement.
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Vitta, Pranciškus. "Frequency-resolved spectroscopy of relaxation proceses in optoelectronic materials and devices." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20101022_095125-06954.
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The thesis is devoted to the frequency-resolved investigation of the relaxation processes in optoelectronic materials and devices. Conventional fluorescence decay time measurement technique in the frequency domain was adapted for the use with light-emitting diode (LED) excitation and signal registration by a lock-in amplifier. Inorganic phosphors synthesized by aqueous sol-gel combustion method for using as wavelength converters in white LEDs as well as advanced organic semiconducting materials were investigated by photoluminescence decay time and quantum yield measurement techniques. The photoluminescence decay time measurement technique with extremely low quasi-continuous UV LED excitation was applied for the carrier dynamics research in GaN epitaxial layers. The investigation under such a low excitation conditions revealed the contribution of donor-acceptor recombination in the yellow luminescence of GaN. The techniques for in-situ thermal characterization of encapsulated LEDs, including the measurements of phosphors converter temperature and heat relaxation time constants inside a LED, were developed and demonstrated for the investigation of commercial low- and high- power LEDs.Disertacija yra skirta relaksacijos procesų, vykstančių optoelektronikos medžiagose ir prietaisuose, tyrimui dažninės skyros metodu. Įprastas fluorescencijos gesimo trukmės tyrimo metodas, veikiantis harmoniškai moduliuoto žadinimo režimu, buvo adaptuotas žadinimui puslaidininkiniais šviestukais ir signalų registravimui radijo dažnių faziniu detektoriumi. Neorganiniai vandeniniu zolių-gelių metodu susintetinti fosforai, skirti baltų puslaidininkinių šviestukų gamybai, ir modernios organinės optoelektronikos medžiagos buvo ištirtos fotoliuminescencijos gesimo dėsnio ir kvantinės išeigos matavimo metodikomis, siekiant nustatyti krūvininkų rekombinacijos savybes ir optimizuoti sintezės parametrus. Realizuotas GaN epitaksinių sluoksnių liuminescencijos kinetikos tyrimas labai žemo kvazitolydinio sužadinimo atveju patvirtino rekombinacijos per priemaišas svarbą šio tipo medžiagose. Buvo sukurtos naujos prekinių šviestukų šiluminių savybių in-situ tyrimo metodikos, veikiančios dažninės skyros režimu. Bangos ilgio keitiklių temperatūra baltuose šviestukuose ir šilumos relaksacijos konstantos įvairaus tipo šviestukų konstrukciniuose elementuose buvo išmatuotos esant vardiniam šviestukų veikimo režimui.
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Paul, Samuel John. "Kinetic friction of lubricated contacts in the deep drawing process." Thesis, University of Ulster, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388878.
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Gershon, Daniel. "Kinetics of Autocausticization Using Borates in a Black Liquor Gasification Process." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4762.
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The path of research in the pulp and paper industry is heading towards the elimination of the lime cycle, which requires large amounts of energy, and changing the conventional recovery boiler system to a gasification process that will reduce the possibility of smelt water explosions while meeting future environmental regulations. Research has been carried out on both gasification processes and on causticizing processes that can replace or complement the lime cycle, however very little research has gone into the actual kinetics of causticization using black liquor in gasification processes. This research project fills in some of the missing knowledge in the area of kinetics of autocausticization reactions, which entails the use of borates as the autocausticizing agent. A temperature dependent kinetic model coupled with a mass transfer coefficient has been developed and compared to experimental data.
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Leksawasdi, Noppol Biotechnology & Biomolecular Sciences (BABS) UNSW. "Kinetics and modelling of enzymatic process for R-phenylacetylcarbinol (PAC) production." Awarded by:University of New South Wales. Biotechnology and Biomolecular Sciences (BABS), 2004. http://handle.unsw.edu.au/1959.4/20846.
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R-phenylacetylcarbinol (PAC) is used as a precursor for production of ephedrine and pseudoephedrine, which are anti-asthmatics and nasal decongestants. PAC is produced from benzaldehyde and pyruvate mediated by pyruvate decarboxylase (PDC). A strain of Rhizopus javanicus was evaluated for its production of PDC. The morphology of R. javanicus was influenced by the degree of aeration/agitation. A relatively high specific PDC activity (328 U decarboxylase g-1 mycelium) was achieved when aeration/agitation were reduced significantly in the latter stages of cultivation. The stability of partially purified PDC and crude extract from R. javanicus were evaluated by examining the enzyme deactivation kinetic in various conditions. R. javanicus PDC was less stable than Candida utilis PDC currently used in our group. A kinetic model for the deactivation of partially purified PDC extracted from C. utilis by benzaldehyde (0?00 mM) in 2.5 M MOPS buffer has been developed. An initial lag period prior to deactivation was found to occur, with first order dependencies of PDC deactivation on exposure time and on benzaldehyde concentration. A mathematical model for the enzymatic biotransformation of PAC and its associated by-products has been developed using a schematic method devised by King and Altman (1956) for deriving the rate equations. The rate equations for substrates, product and by-products have been derived from the patterns for yeast PDC and combined with a deactivation model for PDC from C. utilis. Initial rate and biotransformation studies were applied to refine and validate a mathematical model for PAC production. The rate of PAC formation was directly proportional to the enzyme activity level up to 5.0 U carboligase ml-1. Michaelis-Menten kinetics were determined for the effect of pyruvate concentration on the reaction rate. The effect of benzaldehyde on the rate of PAC production followed the sigmoidal shape of the Monod-Wyman-Changeux (MWC) model. The biotransformation model, which also included a term for PDC inactivation by benzaldehyde, was used to determine the overall rate constants for the formation of PAC, acetaldehyde and acetoin. Implementation of digital pH control for PAC production in a well-stirred organic-aqueous two-phase biotransformation system with 20 mM MOPS and 2.5 M dipropylene glycol (DPG) in aqueous phase resulted in similar level of PAC production [1.01 M (151 g l-1) in an organic phase and 115 mM (17.2 g l-1) in an aqueous phase after 47 h] to the system with a more expensive 2.5 M MOPS buffer.
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Mason, Ian George. "A study of power, kinetics, and modelling in the composting process." Thesis, University of Canterbury. Civil Engineering, 2007. http://hdl.handle.net/10092/1214.
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This thesis explores the roles of physical and mathematical modelling in the prediction of temperature profiles in the composting process. A literature-based evaluation of the performance of laboratory- and pilot scale composting reactors, showed that physical models used in composting research frequently do not properly simulate the full-scale composting environment, and may therefore produce results which are not applicable at full scale. In particular, self-heating, laboratory-scale, reactors typically involve significant convective/conductive/radiative losses, even with insulation present. This problem can be overcome by using controlled temperature difference or controlled heat flux laboratory reactors, which allow convective/conductive/radiative heat fluxes to be controlled to levels close to those occurring in full-scale systems. A new method of assessing the simulation performance of composting systems is presented. This utilises the areas bounded by the temperature-time profile and reference temperatures of 40 and 55 ℃ (A₄₀ and A₅₅), the times for which these temperatures are exceeded (t₄₀ and t₅₅), and times to peak temperature. An evaluation of published temperature profiles showed a marked difference in these parameters when comparing many laboratory- and full-scale reactors. The impact of aeration is illustrated, and laboratory- and pilot-scale reactors able to provide good temperature profile simulation, both qualitatively and quantitatively, are identified. Mathematical models of the composting process are reviewed and their ability to predict temperature profiles assessed. The most successful models in predicting temperature profiles have incorporated either empirical kinetic expressions, or utilised a first-order model, with empirical corrections for temperature and moisture. However, no temperature models have been able to predict maximum, average and peak temperatures to within 5, 2 and 2 ℃ respectively, or to predict the times to reach peak temperatures to within 8 h, although many models were able to successfully predict temperature profile shape characteristics. An evaluation of published constant-temperature and varying-temperature substrate degradation profiles revealed very limited evidence to support the application of single exponential, double exponential or non-logarithmic Gompertz functions in modelling substrate degradation kinetics, and this was identified as a potential weakness in the temperature prediction model. A new procedure for correcting substrate degradation profiles generated at varying temperature to a constant temperature of 40 ℃ was developed and applied in this analysis, and on experimental data generated in the present work. A new approach to the estimation of substrate degradation profiles in the composting process, based on a re-arrangement of the heat balance around a reactor, was developed, and implemented with both a simulated data set, and data from composting experiments conducted in a laboratory-scale constant temperature difference (CTD) reactor. A new simulated composting feedstock for use in these experiments was prepared from ostrich feed pellets, office paper, finished compost and woodchips. The new modelling approach successfully predicted the generic shape of experimental substrate degradation profiles obtained from CO2 measurements, but under the conditions and assumptions of the experiment, the profiles were quantitatively different. Both measured CO2-carbon (CO2-C) and predicted biodegradable volatile solids carbon (BVS-C) profiles were moderately to well fitted by single exponential functions with similar rate coefficients. When corrected to a constant temperature of 40 ℃, these profiles gave either multi-phase or double exponential profiles, depending upon the cardinal temperatures used in the temperature correction procedure. If it is assumed that the double exponential model generated is correct, this work provides strong evidence that a substrate degradation curve generated under appropriate laboratory conditions at 40 ℃ would, given the correct cardinal temperatures, generate a correct substrate degradation profile under varying temperature conditions, and that this in turn would enable an accurate and precise prediction of the temperature profile using a heat and mass balance approach. This finding opens the door for the development of a simple laboratory test for composting raw material characterisation, but underlines the need for accurate estimates of the physical cardinal temperatures. Experimental factors appear to be the likely cause of the dysfunction between previously reported substrate degradation patterns and existing substrate degradation models, and suggestions for further research are provided in order to more precisely and accurately quantify these factors.
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Thomas, Wesley Allan. "Evaluation Of Nitrification Kinetics For A 2.0 MGD IFAS Process Demonstration." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/31588.
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The James River Treatment Plant (JRTP) operated a 2 MGD Integrated Fixed Film Activated Sludge (IFAS) demonstration process from November 2007 to April 2009 to explore IFAS performance and investigate IFAS technology as an option for a full scale plant upgrade in response to stricter nutrient discharge limits in the James River Basin. During the study, nitrification kinetics for both ammonia and nitrite oxidizing bacteria and plastic biofilm carrier biomass content were monitored on a near-weekly basis comparing the IFAS media, the IFAS process mixed liquor, and mixed liquor from the full-scale activated sludge process. Carrier biomass content is variable with respect to temperature and process SRT and relates to the localization of nitrification activity in the IFAS basin. Similar to trends observed for carrier biomass content (Regmi, 2008), ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) activity also shifted from the fixed film to the suspended phase as water temperatures increased and vice versa as the temperature decreased. The data suggest that AOB activity occurs on the surface of the biofilm carriers, while NOB activity remains deeper in the biofilm. During the highest temperatures observed in the IFAS tank, AOB activity on the media contributed as little as 30% of the total nitrification activity in the basin, and after temperatures dropped below 20 °C, AOB activity in the fixed film phase made up 75% of the total activity in the IFAS basin. During the warmest period of the summer, the media still retained more than 60% of the total NOB activity, and more than 90% of the total NOB activity during the period of coldest water temperature. This trend also points out that some AOB and NOB activity remained in the mixed liquor, even during the coldest periods. The retention of nitrification activity in the mixed liquor indicates that the constant sloughing of biomass off of the carriers allowed for autotrophic activity, even during washout conditions. Carrier biomass content and nitrification rates on the IFAS media remained constant along the length of the basin, indicating that the IFAS tank is will mixed with respect to biomass growth, although there was a concentration gradient for soluble species (NH4-N, NO2-N, NO3-N). In addition to the weekly nitrification rate measurements, experiments were also conducted to determine how operational inputs such as dissolved oxygen (DO) and mixing affect the nitrification rates. Mixing intensity had a clear impact on nitrification rates by increasing the velocity gradient in the bulk liquid and decreasing the mass transfer boundary layer mass transfer resistance. At higher mixing intensities, advection through the mass transfer boundary layer increased making substrate more available to the biofilm. The affect of mixing was much more profound at low DO, whereas increased mixing had less effect on nitrification rates at higher bulk liquid DO. DO also affected nitrification rates, such that as DO increased it penetrated deeper into the biofilm increasing the nitrification rate in a linear fashion until the biofilm became saturated. Another aspect of the research was modeling effective half saturation effects for AOB and NOB activity in the fixed film phase. The modeling work demonstrated that KS for AOB activity on the media was similar to accepted suspended growth KS values, while KS for NOB activity on the media was considerably higher than suspended growth KS. This trend indicates that nitrite was not as bioavailable in the biofilm and resists diffusion into the deeper part of the biofilm where NOB activity takes place. KO for both AOB and NOB activity in the biofilm was higher than typical suspended growth values because of boundary layer and biofilm diffusion resistances. In addition, the presence of readily degradable organics did not significantly affect nitrification rates on the media, but did reduce nitrification rates in the mixed liquor. That, combined with low chemical oxygen demand (COD) uptake rates indicates that little heterotrophic activity is occurring on the media.Master of Science
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Lucas, Bruce. "Fundamental Modeling of Solid-State Polymerization Process Systems for Polyesters and Polyamides." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29378.
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The dissertation describes and assembles the building blocks for sound and accurate models for solid-state polymerization process systems of condensation polymers, particularly poly(ethylene terephthalate) and nylon-6. The work centers on an approach for modeling commercial-scale, as opposed to laboratory-scale, systems. The focus is not solely on coupled polymerization and diffusion, but extends to crystallization, physical properties, and phase equilibrium, which all enhance the robustness of the complete model.
There are three applications demonstrating the utility of the model for a variety of real, industrial plant operations. One of the validated simulation models is for commercial production of three different grades of solid-state PET. There are also validated simulation models for the industrial leaching and solid-state polymerization of nylon-6 covering a range of operating conditions. The results of these studies justify our mixing-cell modeling approach as well as the inclusion of all relevant fundamental concepts.
The first several chapters discuss in detail the engineering fundamentals that we must consider for modeling these polymerization process systems. These include physical properties, phase equilibrium, crystallization, diffusion, polymerization, and additional modeling considerations. The last two chapters cover the modeling applications.Ph. D.
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Taylor, Mary Anne. "A kinetic study of bacterial cellulose production by a batch process." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0020/MQ58094.pdf.
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Redzwan, Ghufran. "Kinetic studies on readily biodegradable substrates by the anaerobic digestion process." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395356.
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Ito, Kenji. "Kinetic Study on Single-Electron Transfer Process from Trivalent Phosphorus Compounds." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149545.
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Patchigolla, Kumar. "Particle process measurements : shape and size with crystal growth and nucleation kinetics." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/2088.
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To deduce particle size information, the majority of particle sizing techniques assume that the particles are spheres. For industrial materials, particles are rarely spherical. Non-sphericity causes discrepancies in different measurement technologies so results vary from the real characteristics of the sample. Applications like crystallisation require .shape information in addition to the size of the particles. The majority of this thesis describes results that have demonstrated that particle shape has a strong influence on particle size distribution measured by different techniques. The effect of shape on measured particle size distribution was investigated by ultrasonic attenuation spectroscopy (VAS) compared with other widely used techniques such as laser diffraction spectroscopy (LDS), microscopic image analysis (MIA) and focused beam reflectance measurement (FBRM). A strategy was applied using different chemical systems to monitor the importance of shape to measured size distribution using different techniques; fragile and non-fragile, .sp-pericaC'crystalline and irregular materials were tested. The measurements were successfully applied to laboratory crystallisation processes of different organic and inorganic chemicals In-situ monitoring of particle size evolution during crystallisation using FBRM has aroused much interest. Therefore it was important to demonstrate the dependence of measured particle size on different operating conditions and more particularly on the hydrodynamic conditions, solvent, temperature and other physical and chemical , properties of the system. In-situ measurement of maximum supersaturation during batch crystallisation and dissolution processes of different chemical systems is presented, through which nucleation kinetics of the crystallisation was retrieved. This was clemonstrated for different organic and inorganic chemical systems using FBRM as a process analytical technique (PAT). Based on crystallisation behaviour and with process analytical techniques, notably FBRM to retrieve the nucleation kinetics, the growth kinetics of different chemical systems are presented based on seeded batch cooling crystallisation. Finally future developments within this area of research are presented.
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Visuri, V. V. (Ville-Valtteri). "Mathematical modelling of chemical kinetics and rate phenomena in the AOD Process." Doctoral thesis, Oulun yliopisto, 2017. http://urn.fi/urn:isbn:9789526216713.
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Abstract Argon-oxygen decarburisation (AOD) is the most common unit process for refining stainless steel. The AOD process consists of multiple stages, in which the rate of processing is determined by complex reaction mechanisms. The main objective of this work was to study the chemical rate phenomena in selected process stages. For this purpose, an extensive literature review was conducted to clarify the main assumptions of the existing reaction models. Based on the literature review, a new categorisation of the models was proposed. In addition, a literature review was conducted to identify the main phenomena that affect the reaction kinetics in the AOD process. In this work, based on the law of mass action, a novel kinetic approach and its application for modelling of parallel mass transfer controlled reactions were studied. The developed approach enables the simultaneous solution of the chemical equilibrium and mass transfer rate which controls it. A simplified reaction model was employed for studying the effect of mass transfer rates and residual affinity on the constrained equilibrium at the reaction interface. An earlier-proposed AOD model was extended with two phenomenon-based sub-models. The top-blowing model is based on the assumption that reactions take place simultaneously at the surface of the cavity formed by the momentum of the gas jet and on the surface of the metal droplets caused by the shear force of the gas jet. The reduction model describes the reactions during the reduction stage of the AOD process by assuming that all reactions take place between the metal bath and emulsified slag droplets. The results obtained with the models were in good agreement with the measurement data collected from a steel plant. Owing to their phenomenon-based structure, the developed models are well-suited for the analysis of both existing and new production practicesTiivistelmä Argon-happimellotus (AOD) on yleisin ruostumattoman teräksen valmistamiseen käytettävä yksikköprosessi. AOD-prosessi koostuu useista vaiheista, joissa prosessointinopeutta määrittävät monimutkaiset reaktiomekanismit. Tutkimuksen päätavoitteena oli tutkia kemiallisia nopeusilmiöitä valituissa prosessivaiheissa. Tähän liittyen tehtiin kattava kirjallisuuskatsaus, jonka tavoitteena oli tunnistaa olemassa olevien reaktiomallien pääoletukset. Kirjallisuuskatsauksen pohjalta esitettiin uusi mallien kategorisointi. Lisäksi tehtiin kirjallisuuskatsaus, jonka tavoitteena oli tunnistaa tärkeimmät reaktiokinetiikkaan vaikuttavat ilmiöt AOD-prosessissa. Tässä työssä tutkittiin uudenlaista massavaikutuksen lakiin perustuvaa lähestymistapaa sekä sen soveltamista rinnakkaisten aineensiirron rajoittamien reaktioiden mallinnukseen. Kehitetty lähestymistapa mahdollistaa kemiallisen tasapainotilan sekä sitä rajoittavan aineensiirron samanaikaisen ratkaisun. Aineensiirtonopeuksien ja jäännösaffiniteetin vaikutusta reaktiopinnalla vallitsevaan rajoitettuun tasapainotilaan tutkittiin käyttämällä yksinkertaistettua reaktiomallia. Aiemmin kehitettyä AOD-mallia laajennettiin kahdella ilmiöpohjaisella alimallilla. Lanssipuhallusmalli perustuu oletukseen, että reaktiot tapahtuvat samanaikaisesti kaasusuihkun liikemäärän muodostaman tunkeuman ja kaasusuihkun leikkausvoiman aiheuttamien metallipisaroiden pinnalla. Pelkistysmalli kuvaa AOD-prosessin pelkistysvaiheen aikana tapahtuvia reaktioita olettaen, että kaikki reaktiot tapahtuvat terässulan ja emulgoituneiden kuonapisaroiden välillä. Malleilla saadut tulokset vastasivat hyvin terästehtaalta kerättyä mittausaineistoa. Ilmiöpohjaisen rakenteensa ansiosta kehitetyt mallit soveltuvat hyvin sekä olemassa olevien että uusien tuotantopraktiikoiden analysoimiseen
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Smith, Sheryl Dianna. "The Influence of Water Quality on Arsenic Sorption and Treatment Process Performance." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33581.
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A new regulation has been proposed that would lower the acceptable level of arsenic in drinking water from the current standard of 50 ppb. Therefore, research into effective arsenic removal treatment is important, especially for hard to treat waters with high concentrations of silica.
The first phase of research was designed to determine if sand ballasted coagulation is a viable means of removing arsenic from drinking water, and if so, to identify the water qualities in which the technology performs best. A jar test protocol was developed and tested on a wide range of waters to compare microsand ballasted coagulation and other coagulation based treatment processes in terms of arsenic removal. Secondary impacts of the microsand process such as residual turbidity, iron, post-treatment membrane filter run length, and TOC removal were also considered as part of this evaluation. Microsand ballasted coagulation provided promising results for many of the simulated groundwater test conditions in which more than 80% of the arsenic regulation costs will be incurred. However, like conventional coagulation/sedimentation, microsand ballasted coagulation performed poorly in waters with high silica and high pH.
Thereafter, a second phase of research more closely examined the kinetic behavior of arsenic sorption to amorphous and granular oxides in the presence of silica and calcium. At pH 8.5, calcium dramatically improved arsenic sorption to amorphous iron hydroxide in the presence of silica over short reaction times, but had no long-term advantage. This result could have considerable applications for treatment in that it suggests water quality controls the required reaction times. Additionally, batch tests indicated that activated alumina granular media was more sensitive to water quality than granular ferric hydroxide; however, calcium eliminated silica interference to arsenic sorption onto activated alumina.Master of Science
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Khoo, Ji Yi. "Thermodynamic stability and kinetic analysis of pharmaceutical channel hydrate during dehydration process." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/5702.
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This thesis presents a detailed study into the thermodynamic stability and dehydration kinetics of a model pharmaceutical channel hydrate: carbamazepine dihydrate. The model compound of different crystal habits and particle size distributions was prepared via solventmediated crystallisation technique and agitated hydration method. The causal relationship between key drying process parameters (i.e. temperature, pressure, relative humidity and organic solvent partial pressure) and dehydration behaviour of this model compound was established using Dynamic Vapour Sorption instruments. Solid state phase transformation mechanisms under these drying conditions were elucidated through the evolution of crystal structural determined by X-ray Powder Diffraction technique. Dehydration kinetics of carbamazepine dihydrate were found to be markedly influenced by increasing temperature, reducing pressure, low humidity and higher organic solvent partial pressure, providing that the drying environment stays below the critical humidity and partial pressure for the dihydrate and acetone solvate formations. Activation energy determined from the kinetic study allows differentiation between the physically bound water in the bulk and water of crystallisation. Agglomerated dihydrate however possessed a high free water retention capacity when it exceeded a certain particle size distribution. This type of agglomerate exhibited distinct closed structure characteristics, leading to a relatively more stable form of carbamazepine dihydrate, than those without inclusion of unbound water. The agglomeration effect can thus be potentially controlled and exploited to expand the environmental stability envelope of the desired hydrated forms during manufacturing processes. Subtle changes in the drying environment were able to induce polymorphic anhydrates of different stabilities. The solid state phase transformation pathway of carbamazepine dihydrate to the four polymorphic anhydrates and an amorphous form was strongly correlated to types of dehydration mechanism, and specifically to the accessibility of and interaction with surrounding solvent vapours (i.e. hydrogen bonding propensity). Alkanol solvent vapourmediated dehydration process was found to facilitate the formation of the thermodynamically stable anhydrate, without any loss in product crystallinity. Dipolar aprotic solvents however induced the (intermediate) formation of least metastable anhydrate, depending on the local chemical environment of solute-solvent system. In conclusion, the surrounding solvent vapour plays a crucial role in drying strategies for a channel type hydrate, as it provides potential to predict and tailor the polymorphism of the desired forms which could have profound implications on the quality and performance of the final product.
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Pugliese, Sebastian C. "Kinetics and mass transfer in the chlorination of draft pulp fibers." Available online, Georgia Institute of Technology, 2005, 1988. http://etd.gatech.edu/theses/available/ipstetd-1040/.
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Clayton, John Andrew. "Denitrification kinetics in biological nitrogen and phosphorus removal activated sludge systems." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/21139.
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In order to size the anoxic reactors in nutrient (N and P) removal activated sludge plants, it is essential to know the denitrification kinetics that are operative in such systems. To date, denitrification kinetics have been accurately defined only for systems that remove N alone; little research has been performed on denitrification in N and P removal plants.
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Martinis, Coll Jorge Maximiliano. "Single event kinetic modeling of solid acid alkylation of isobutane with butenes over proton-exchanged Y-Zeolites." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/3232.
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Complex reaction kinetics of the solid acid alkylation of isobutane with butenes over a proton-exchanged Y-zeolite has been modeled at the elementary step level. Starting with a computer algorithm that generated the reaction network based on the fundamentals of the carbenium ion chemistry, the formation of over 100+ product species has been modeled in order to gain understanding of the underlying phenomena leading to rapid catalyst deactivation and product selectivity shifts observed in experimental runs. An experimental investigation of the solid acid alkylation process was carried out in a fixed bed catalytic reactor operating with an excess of isobutane under isothermal conditions at moderate temperatures (353-393 K) in liquid phase. Experimental data varying with run-time for a set of butene space-times and reaction temperatures were collected for parameter estimation purposes. A kinetic model was formulated in terms of rate expressions at the elementary step level including a rigorous modeling of deactivation through site coverage. The single event concept was applied to each rate coefficient at the elementary step level to achieve a significant reduction in the number of model parameters. Based on the identification of structural changes leading to the creation or destruction of symmetry axes and chiral centers in an elementary step, formulae have been developed for the calculation of the number of single events. The Evans-Polanyi relationship and the concept of stabilization energy were introduced to account for energy levels in surface-bonded carbenium ions. A novel functional dependency of the stabilization energy with the nature of the carbenium ion and the carbon number was proposed to account for energy effects from the acid sites on the catalyst. Further reductions in the number of parameters and simplification of the equations for the transient pseudohomogeneous one-dimensional plug-flow model of the reactor were achieved by means of thermodynamic constraints. Altogether, the single event concept, the Evans-Polanyi relationship, the stabilization energy approach and the thermodynamic constraints led to a set of 14 parameters necessary for a complete description of solid acid alkylation at the elementary step level.
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Parkes, Amanda Jane. "Phrases of the kinetic : dynamic physicality as a dimension of the design process." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51661.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2009.Includes bibliographical references (p. 161-167).
At its core, the concept of Tangible Interfaces leverages the idea of using the movement of the body as an inherent part of the human side of a human-computer interaction, assuming that bodily engagement and tactile manipulation can facilitate deeper understanding and more intuitive experiences. However, as an interaction principle in our era of digital design, motion construction and control has been underutilized and little examined as a design tool, leaving open the possibilities of motion's natural ability to draw our attention, provide physical feedback, and convey information through physical change. This dissertation postulates that the ability to experiment, prototype, and model with programmable kinetic forms is becoming increasingly important as digital technology becomes more readily embedded in our objects and environments and need for tools and systems with which to create, manipulate and finesse motion in response to computational and material input remains an under-developed design area. This thesis aims to establish principles of kinetic design through the exploration of two approaches to motion construction and manipulation: motion prototyping as a methodology for design thinking, learning and communication and physically dynamic state memory as a methodology for organic form finding and transformation in the design process.
(cont.) To demonstrate these aims, I present three interface systems: Topobo, a system for motion construction and dynamics physics education with children; Kinetic Sketchup, a system for motion construction and prototyping in architecture and product design; and Bosu, an augmented textile interface offering an experimental approach to digitally augmented organic form finding in fashion and product design.
Amanda Jane Parkes.
Ph.D.
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Sabzevari, Seyed Mostafa. "Cure kinetics and process modeling of a carbon-fiber thermoplastic-toughened epoxy resin prepreg." Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3326.
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It is well known that the mechanical performance and fracture behavior of a thermosetting composite is inherently determined by the properties and characteristics of its constituents. However, the performance and behavior is also drastically influenced by the viscoelastic properties and status of the material during the cure process. This brings about a need to possess knowledge of the cure history of any composite product. Such knowledge is attainable by monitoring the material response to temperature and pressure cycles throughout the cure process. Nevertheless, changes to the cure and, equivalently, the manufacturing process influences the final cost of a composite product, thus, making it crucial to select an optimum cure profile conducive to both the desired thermo-mechanical properties as well as minimum cost.
The present work investigates the cure kinetics and process behavior of a commercial carbon-fiber thermoplastic-toughened epoxy resin prepreg, IM7/977-2 UD. Experimental data and theoretical models are mostly demonstrated in the form of cure time and temperature functions, f(t,T). A comprehensive cure map is constructed based on this data in order to provide all the necessary information for design of an optimum cure profile.
Material properties are measured over a broad range of isothermal cure profiles using advanced analytical techniques such as shear rheometry and Differential Scanning Calorimetry (DSC). Shear rheometry is utilized to quantify some important viscoelastic properties, such as complex viscosity (η*), shear storage modulus (G′), and shear loss modulus (G″), as well as to identify important cure transitions like gelation and vitrification. Thermal properties are obtained using DSC. These include heat flow (dH/dt), glass transition temperature (Tg), and degree of conversion (α). Before performing DSC experiments it is necessary to know a material’s
decomposition temperature, and this is obtained through the use of Thermogravimetric Analysis (TGA).
Since the material studied in this work is a thermoplastic-toughened epoxy prepreg, a variety of discrepancies in comparison to the kinetics of neat epoxies are observed. These inconsistencies invariably show up as variations in the values of Tg, ultimate heat of reaction (HU), and rate of reaction (dα/dt). For the 977-2 material, it is concluded that the addition of the thermoplastic agent to the epoxy significantly affects the progress of chemical reactions in addition to imparting a step transition in the progress of Tg at elevated isothermal cure temperatures (Tcure ≥ 180 °C). Furthermore, it is concluded that the existence of fibers among the polymer monomers alter the flow-ability of resin molecules throughout the cure process, resulting in early vitrification and lower HU over the entire range of Tcure. The variations observed in the values of HU at various Tcure may result in either under- or overestimation of α regardless of the relationship utilized to calculate it. In addition, a unique one-to-one relationship is established between Tg and α. Regarding the uncertainties present in the calculation of α, it is concluded that Tg is a better estimate of the state of the material at every desired stage of cure.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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Gu, Xiangyu. "Molten-salt Catalytic Pyrolysis (MSCP): A Single-pot Process for Fuels from Biomass." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-theses/504.
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A novel process for single-pot conversion of biomass to biofuels was developed called the molten salt catalytic pyrolysis (MSCP) method. The proposed single-pot MSCP process proved to be an inherently more efficient and cost-effective methodology for converting lignocellulosic biomass. In this study, several parameters that affect yield of bio-oil were investigated including carrier gas flow rate; pyrolysis temperature; feed particle size; varying types of molten salt and catalysts. Use of molten salt as the reaction medium offered higher liquid yield and experiments containing ZnCl2 showed higher yield than other chloride salts. The highest yield of bio-oil was up to 66% obtained in a ZnCl2-KCl-LiCl ternary molten salt system compared with 32.2% at the same condition without molten salts. In addition, the effect of molten salt on the composition of bio-oil was also studied. It was observed that molten salt narrowed the product distribution of bio-oil with furfural and acetic acid as the only two main components in the liquid with the exception of water. Finally, a thermogravimetric kinetic study on the pyrolysis of biomass in MSCP was conducted.
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Tan, Bing. "CONTROLLED SYNTHESIS AND FUNCTIONALIZATION OF NANOPOROUS SOLGEL SILICA PARTICLES AND GELS." UKnowledge, 2005. http://uknowledge.uky.edu/gradschool_diss/305.
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This dissertation addresses three research areas in the sol-gel synthesis of functionalmaterials. The first is the kinetics of hydrolysis and condensation of variousorganoalkoxysilanes. Two mathematical models are developed for the sol-gel reaction inbasic conditions with and without nearest-neighbor effects. Effects on reactivity aremeasured with systematic changes in the organic group structure. Replacing onemethoxy group on the precursor with a methyl group decelerates hydrolysis under basicconditions, but accelerates condensation under acidic conditions. Replacing two methylfunctionalprecursors with one ethylene-bridged precursor accelerates hydrolysis in base,but decelerates condensation in acid. Replacing an ethylene bridge with a hexylenebridge always decelerates the sol-gel reactions. Adding an amine into the hexylenebridge always accelerates the sol-gel reactions. These trends show inductive effectsplaying a role only under basic conditions, while steric effects play a role at all pHvalues. The second topic of this thesis is the synthesis of organic-inorganic materialswith bridging or non-bridging organics. The structure of the organic-inorganic hybrids ispartially correlated with the kinetics of the precursors, but the trends indicate anadditional structural role of siloxane cyclization. The third topic of this thesis is thesynthesis of surfactant-templated nanoporous particles. The key to preparing orderedhybrid materials is found to be encouraging aggregation with a surfactant whilediscouraging random condensation of silanes independent of the surfactants. Ahomologous series of cationic pyridinium chloride fluorinated surfactants with varyingchain length are used as pore templates. Typical pore structures such as hexagonal closepackedcylinders are synthesized, as well as new pore structures including random meshphase pores and vesicular silica particles with bilayer or multilayer shells.Fluorosurfactants enable the formation of unusually small pores (1.6 nm) and poresformed from discs or bilayers. In the presence of ethanol, spherical particles with radiallyoriented pores are shown by TEM to form by precipitation of disordered silica-surfactantparticles followed by assembly into organized structures. High-capacity hollow particleswith ordered mesoporous shells are prepared by dual latex / surfactant templating.Finally, we load amine-functionalized mesoporous silica with highly dispersedsuperparamagnetic iron oxide nanoparticles.
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Khan, Maazullah. "Modeling of extrusion cooking of full-fat soybean in a single screw extruder /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9821347.
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Engblom, Stefan. "Numerical Solution Methods in Stochastic Chemical Kinetics." Doctoral thesis, Uppsala universitet, Avdelningen för teknisk databehandling, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9342.
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This study is concerned with the numerical solution of certain stochastic models of chemical reactions. Such descriptions have been shown to be useful tools when studying biochemical processes inside living cells where classical deterministic rate equations fail to reproduce actual behavior. The main contribution of this thesis lies in its theoretical and practical investigation of different methods for obtaining numerical solutions to such descriptions. In a preliminary study, a simple but often quite effective approach to the moment closure problem is examined. A more advanced program is then developed for obtaining a consistent representation of the high dimensional probability density of the solution. The proposed method gains efficiency by utilizing a rapidly converging representation of certain functions defined over the semi-infinite integer lattice. Another contribution of this study, where the focus instead is on the spatially distributed case, is a suggestion for how to obtain a consistent stochastic reaction-diffusion model over an unstructured grid. Here it is also shown how to efficiently collect samples from the resulting model by making use of a hybrid method. In a final study, a time-parallel stochastic simulation algorithm is suggested and analyzed. Efficiency is here achieved by moving parts of the solution phase into the deterministic regime given that a parallel architecture is available. Necessary background material is developed in three chapters in this summary. An introductory chapter on an accessible level motivates the purpose of considering stochastic models in applied physics. In a second chapter the actual stochastic models considered are developed in a multi-faceted way. Finally, the current state-of-the-art in numerical solution methods is summarized and commented upon.
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YANG, ZHAOHUI. "HIGH TEMPERATURE OXYGEN SORPTION PROCESS FOR AIR SEPARATION AND OXYGEN REMOVAL." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1028824899.
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Hong, Yifeng. "Processing of expandable thermoplastic/thermoset syntactic foam." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53895.
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While hollow glass microspheres are commonly used in syntactic foam, their abrasive and brittle properties usually result in poor processability and have adverse effects on the foam performance. Therefore, a number of attempts have been made in the industry to replace hollow glass microspheres with polymeric foamed microspheres. Among many choices, expandable thermoplastic (ETP) microspheres filled syntactic foam has shown its high potential to become a novel class of engineering materials, especially for lightweight structural applications. However, conventional processing techniques for syntactic foam usually experience difficulties such as high processing viscosity, low loading of foam fillers, and ineffective microsphere expansion.
To address these emerging issues, a microwave expansion process to produce thermoset-matrix syntactic foam containing thermoplastic foam beads was developed in this thesis work. In this process, unexpanded ETP microspheres were directly foamed in uncured thermoset matrix via microwave heating. Expandable polystyrene (EPS) microspheres and epoxy resin were chosen as a model material system. The resin viscosity and specific microwave energy are found to be the two primary control parameters determining the process window. Mechanical characterization showed that the syntactic foam can outweigh neat polymer in lightweight structural applications and was effectively toughened by foamed EPS.
Furthermore, the microwave expansion process was found to be capable of molding syntactic foam parts of relatively sophisticated geometry with smooth surfaces.
In order to broaden its impact, the microwave expansion process was extended to produce composite EPS foam. This process converts an expandable suspension into a composite foam with a honeycomb-like barrier structure. The suspension viscosity was found to highly influence the foam morphology. Results from mechanical tests showed that the existence of the barrier structure can considerably improve the mechanical performance of the composite foam. Fire-retardation tests demonstrated that the barrier structure can effectively stop the fire path into the foam, suppress toxic smoke generation, and maintain foam structure integrity.
A general formulation was developed to model the EPS expansion to optimize the microwave expansion process. A semi-analytical solution was first obtained based on the case of a single bubble expansion in an infinite matrix. The dimensionless bubble radius and pressure are defined and found to be as exponential functions of dimensionless expansion time. The semi-analytical solution can qualitatively predict the radial expansion of EPS microsphere observed in a real-time experiment. To have an accurate prediction, a numerical solution was obtained to the model that couples the nucleation and expansion of multiple bubbles in a finite matrix. The results show that the numerical solution can quantitatively predict the radial expansion of EPS. A parameter sensitivity study was performed to examine the effect of each parameter over the expansion process.
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Evans, James Michael Burgess. "Structuro-kinetic process assessment of the batch crystallization of phenoxyacetic acid : a molecular perspective." Thesis, Heriot-Watt University, 2003. http://hdl.handle.net/10399/277.
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Kazi, Rafiq Akhtar. "A high pressure kinetic study of the in-situ combustion process for oil recovery." Thesis, University of Salford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261611.
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Araujo, Leandro Goulart de. "Photo-oxidative degradation of bisphenol A by H2O2/UV: process study and kinetic modelling." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-17072018-111837/.
Full textAbstract:
Bisphenol A (BPA) is widely used in the production of plastics, epoxy resins and polycarbonates. It is a toxic, endocrine disruptor compound. Different studies have shown the presence of BPA in several environmental systems, classifying it as a worldwide persistent pollutant which may act synergistically with other pollutants. In this context, advanced oxidation processes (AOP) have received great attention due to their ability to degrade pollutants with such characteristics, through their transformation into less hazardous compounds or even their mineralization. Although there are investigations on the use of AOPs for BPA degradation, systematic studies on the effects of process variables, coupled with the statistical interpretation of the results are virtually non-existent. Furthermore, to the best of our knowledge, a rigorous kinetic model has not yet been proposed for the degradation of this pollutant by the H2O2/UV process. The objective of this work was to evaluate BPA degradation by the H2O2/UV process, investigating the effects of the initial H2O2 concentration and the specific rate of photons emission (EP,0) by means of a Doehlert experimental design, combined with the response surface methodology. The experiments were performed in a photochemical tubular reactor equipped with a 254-nm UV lamp, for [H2O2]0 and EP,0 in the ranges 1.6-9.6 mmol L-1 and 0.87 × 1018-3.6 × 1018 photons L-1 s-1, respectively. Total BPA degradation was achieved after 60 min of irradiation in all experiments. The best conditions were [H2O2]0 = 7.6 mmol L-1 and EP,0 = 3.6 × 1018 photons L-1 s-1, for which the best performance was obtained regarding the BPA degradation rate, BPA degradation after 15 min, and the second highest TOC removal after 180 min. However, in most experiments less than 75% TOC removal was observed, with 95% mineralization obtained only for the superior [H2O2]0 and EP,0. A mathematical model was developed, considering the reactor characteristics and the radiation field, based on the line source with parallel emission (LSPP) approach, in combination with the radiative transfer equation (RTE), mass balances, and a detailed kinetic model of the H2O2/UV process. The steady-state approximation was applied for all radical species. In the estimation of unknown kinetic constants, the non-linear least squares method was employed. The model was able to satisfactorily fit experimental BPA and H2O2 concentrations as a function of time. This work shows that the H2O2/UV process is a good alternative for BPA removal from aqueous streams, with total degradation of the target compound and adequate percent mineralization under optimal operating conditions. Such conditions may serve as first guidelines for pilot-plant and industrial processes operation. In addition, simulations using the proposed kinetic model may provide useful information for the design and scale-up of pre- or post-treatment of effluents containing this pollutant.O bisfenol A (BPA) é amplamente utilizado na fabricação de plásticos, resinas epóxi e policarbonatos. Trata-se de um composto tóxico e um desregulador endócrino. Diferentes estudos evidenciam a presença do BPA em diversos compartimentos ambientais em todo planeta, identificando-o como um poluente persistente e resistente à degradação biológica, que apresenta efeitos sinergéticos com outros poluentes. Nesse contexto, os processos oxidativos avançados (POA) têm recebido atenção devido a sua capacidade em degradar poluentes com tais características, transformando-os em compostos menos perigosos ou até mesmo mineralizando-os totalmente. Apesar de haver trabalhos na literatura acerca da utilização de POA para degradação de BPA, estudos sistemáticos dos efeitos de variáveis de processo junto com a interpretação estatística dos resultados são virtualmente inexistentes. Além disso, até onde se sabe um modelo cinético rigoroso ainda não foi proposto para a degradação desse poluente por meio do processo H2O2/UV. Este trabalho teve por objetivo avaliar a degradação do BPA pelo processo H2O2/UV, investigando os efeitos da concentração inicial de H2O2 e da taxa específica de emissão de fótons (EP,0) por meio de um projeto experimental Doehlert, combinado com a análise de superfície de resposta. Os experimentos foram realizados em um reator tubular fotoquímico equipado com uma lâmpada UV de 254 nm, para [H2O2]0 e EP,0 entre 1,6-9,6 mmol L-1 e 0,87 × 1018 - 3,6 × 1018 fótons L-1 s-1, respectivamente. Todos os experimentos sob H2O2/UV resultaram em total degradação do BPA após 60 min de irradiação. Nesse caso, as melhores condições foram [H2O2]0 = 7,6 mmol L-1 e EP,0 = 3,6 × 1018 fótons L-1 s-1, para as quais se obteve o melhor desempenho quanto à taxa de degradação de BPA e à remoção após 15 min, e a segunda maior remoção de COT após 180 min. Entretanto, na maioria dos experimentos menos de 75% de remoção de COT foram observados, com 95% de mineralização obtida apenas para os maiores [H2O2]0 e EP,0. Elaborou-se um modelo matemático que considera as características do reator utilizado e o campo de radiação, baseado no modelo de fonte linear de emissão em planos paralelos (LSPP), combinado à equação de transferência radiativa (RTE), aos balanços materiais e a um modelo cinético detalhado do processo H2O2/UV. Foi empregada a aproximação de estado estacionário para todas as espécies radicalares. Na estimativa das constantes cinéticas desconhecidas, utilizou-se o método de mínimos quadrados não linear. Esse modelo foi capaz de ajustar satisfatoriamente as concentrações experimentais de BPA e de H2O2 em função do tempo. Este trabalho mostra que o processo H2O2/UV constitui uma alternativa conveniente para a degradação de BPA em matrizes aquosas, com total degradação do composto alvo e porcentagem de mineralização adequada nas condições ótimas de operação. Tais condições podem servir como diretrizes iniciais de processamento em escalas piloto e industrial. Por sua vez, simulações empregando o modelo matemático proposto permitem gerar informações úteis para projeto e aumento de escala de processos de pré- ou pós-tratamento de efluentes contendo esse poluente.