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1
Lau, Wai Ngar. "Zeolite membrane microreactor for fine chemical production /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CENG%202006%20LAUW.
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Yasmin, Samina. "Engineering of P450cam for fine chemical synthesis." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497160.
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Asmatulu, Ramazan. "Advanced Chemical-Mechanical Dewatering of Fine Particles." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26604.
Texte intégralRésumé :
In the present work, novel dewatering aids and a novel centrifuge configuration were developed and applied for the purpose of dewatering fine particles. Three different types dewatering reagents were tested in different filtration and centrifugation units. These chemicals included low-HLB surfactants, naturally occurring lipids, and modified lipids. Most of these reagents are insoluble in water; therefore, they were used in solutions of appropriate solvents, such as light hydrocarbon oils and short-chain alcohols. The role of these reagents was to increase the hydrophobicity of the coal and selected mineral particles (chalcopyrite, sphalerite, galena, talc, clay, phosphate, PCC and silica) for the dewatering. In the presence of these reagents, the water contact angles on the coal samples were increased up to 90o. According to the Laplace equation, an increase in contact angle with the surfactant addition should decrease the capillary pressure in a filter cake, which should in turn increase the rate of dewatering and help reduce the cake moisture. The use of the novel dewatering aids causes a decrease in the surface tension of water and an increase in the porosity of the cake, both of which also contribute to improved dewatering.
A series of batch-scale dewatering tests were conducted on a variety of the coal and mineral samples using the novel dewatering aids. The results obtained with a Buchner funnel and air pressure filters showed that cake moistures could be reduced substantially, the extent of which depends on the particle size, cake thickness, drying time, reagent dosage, conditioning time, reagent type, sample aging, water chemistry, etc. It was determined that use of the novel dewatering aids could reduce the cake formation time by a significant degree due to the increased kinetics of dewatering. At the same time, the use of the dewatering aids reduced the cake moistures by allowing the water trapped in smaller capillaries of the filter cake. It was found that final cake moistures could be reduced by 50% of what can be normally achieved without using the reagents. However, the moisture reduction becomes difficult with increasing cake thickness. This problem can be minimized by applying a mechanical vibration to the cake, spraying a short-chain alcohol on the cake and by adding a small amount of an appropriate coagulant, such as alum and CaCl2 to the coal and mineral slurries.
The novel dewatering aids were also tested using several different continuous filters, including a drum filter, disc filter and horizontal belt filter (HBF). The results obtained with these continuous filtration devices were consistent with those obtained from the batch filters. Depending on the coal and mineral samples and the type of the reagent, 40 to 60% reductions in moisture were readily achieved.
When using vacuum disc filters, the cake thickness increased substantially in the presence of the novel dewatering aids, which could be attributed to the increased kinetics of dewatering. A dual vacuum system was developed in the present work in order to be able to control the cake thickness, which was necessary to achieve lower cake moistures. It was based on using a lower vacuum pressure during the cake formation time, while a full vacuum pressure was used during the drying cycle time. Thus, use of the dual vacuum system allowed the disc filter to be used in conjunction with the novel dewatering aids. Its performance was similar to that of HBF, which is designed to control cake thickness and cake formation time independently.
The effectiveness of using the novel dewatering aids were also tested in a full-continuous pilot plant, in which coal samples were cleaned by a flotation column before the flotation product was subjected to the disc filter. The tests were conducted with and without using novel dewatering aids. These results were consistent with those obtained from the laboratory and batch-scale tests.
The novel centrifuge developed in the present work was a unit, which combined a gravity force and air pressure. The new centrifuge was based on increasing the pressure drop across the filter cake formed on the surface of the medium (centrifuge wall). This provision made it possible to take advantage of Darcy s law and improve the removal of capillary water, which should help lower the cake moisture. A series of tests were conducted on several fine coal and mineral particles and obtained more than 50% moisture reduction even at very fine particle size (2 mm x 0).
Based on the test results obtained in the present work, two proof-of-concept (POC) plants have been designed. The first was for the recovery of cyclone overflows that are currently being discarded in Virginia, and the other was for the recovery of fines from a pond in southern West Virginia. The former was designed based on the results of the plant tests conducted in the present work. Cost vs. benefit analyses were conducted on the two POC plants. The results showed very favorable internal rates of return when using the novel dewatering aids.
Surface chemistry studies were conducted on the coal samples based on the results obtained in the present investigation. These consisted mainly of the surface characterization of the coal samples (surface mineral composition, surface area, zeta potential, x-ray photoelectron microscopy (XPS)), acid-base interactions of the solids and liquids, dewatering kinetic tests, contact angle measurements of the coal samples and surface force measurements using AFM. In addition, carbon coating on a silica plate using palsed laser deposition (PLD) and Langmuir-Blodgett (LB) film deposition tests were conducted on the sample to better understand the surfactant adsorption and dewatering processes. The test results showed that the moisture reductions on the fine particles agree well with the surface chemistry results.<br>Ph. D.
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Msutu, Ath'enkosi. "New CO₂ chemistry for fine chemical synthesis." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/13102.
Texte intégralRésumé :
Includes abstract.~Includes bibliographical references (leaves 89-96).<br>There is a great need in the chemical industry for developing CO2 as a C1 building block as an important step towards "green chemistry". CO2 is also attractive as a chemical feedstock because it is readily available, inexpensive, nontoxic and it can replace toxic building blocks such as phosgene and CO. Industrially, megatons of CO2 are used each year for the production of urea, inorganic carbonates, salicylic acid, and polycarbonates, yet this is still miniscule compared to the immense potential that is still yet to be harnessed in using this versatile building block. This thesis discusses how a novel methodology was developed for synthesising a benzotriazole (Bt) urea directly from CO2 in a two-step, one-pot synthesis. The procedure involves trapping CO2 with a primary or secondary amine in the presence of DBU, and reaction of the resultant carbamate salt with triphenylphosphine and chlorobenzotriazole (BtCl) to produce Bt ureas in moderate to high yields. The Bt group may serve as a leaving group in nucleophilic substitution reactions, therefore it is also shown here how the Bt urea presents itself as a precursor for an array of useful organic intermediates. These intermediates include ureas, amides, S-thiocarbamates and sulfonylureas.
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Elmekawy, Ahmed. "Bifunctional supported catalysts for fine chemical synthesis." Thesis, University of Huddersfield, 2014. http://eprints.hud.ac.uk/id/eprint/23325/.
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The objective was to prepare and optimise solid acid and solid base catalysts for liquid phase reactions. The approach has been to functionalize porous silica support materials with acid and base catalytic groups. Solid acid, solid base and bifunctional solid acid/base catalysts were studied. Evidence for acid-base cooperative catalytic mechanisms was found, suggesting that these bifunctional catalysts could show significant advantages over singly functionalized materials of mixtures thereof. Silicas functionalized with tethered aminopropyl groups were prepared by both a grafting method and a sol–gel method. The solids were fully characterized and were tested in the nitroaldol condensation between nitromethane and benzaldehyde to afford nitrostyrene and the aldol reaction between 4-nitrobenzaldehyde and acetone to afford 4-(4-nitrophenyl)-4-hydroxy-2-butanone. The catalytic activities of these materials were found to be dependent on the dispersion and accessibilities of the active sites which, in turn, depend on the methods utilized for the catalyst preparation. Solid acid catalysts were prepared by grafting silica with mercaptopropyl-trimethoxysilane (MPTS) followed by oxidation. The influence of the oxidation procedure on the acidity of the catalyst is described. The use of concentrated HNO3 optimizes the oxidation process and increases the concentration of active sites in comparison to H2O2. The activities of these catalysts were tested in the deacetalization of benzaldehyde dimethyl acetal to benzaldehyde. The use of solid acid and solid base catalysts in the same system was examined, in a two-stage acid-catalyzed deacetalization and base-catalyzed Henry reaction. Solid bifunctional acid-base catalysts were prepared by grafting on amorphous silica in two ways: 1) by grafting propylsulfonic acid and aminopropyl groups to the silica surface (NH2-SiO2-SO3H) and 2) by grafting aminopropyl groups and then partially neutralizing with phosphotungstic acid, relying on the H2PW12O40- ion for surface acidity (NH2-SiO2-NH3+[H2PW12O40-]. These two bifunctional catalysts were compared with each other and with the singly functionalised catalysts described above. Surface acidities and basicities were characterized by adsorption calorimetry, using SO2 as a probe for surface basicity and NH3 for surface acidity. Catalytic activities were measured in the tandem deacetalization/Henry reaction described above, and in an aldol reaction in which a cooperative acid-base catalytic mechanism is thought to be effective. Overall NH2-SiO2-SO3H catalysts showed higher concentrations and strengths of both acid and base sites, and higher activities. Both catalysts showed evidence of cooperative acid-base catalytic sites. Even in the deacetalization/Henry reaction, the bifunctional catalysts exhibited a catalytic advantage over physical mixtures of singly functionalized catalysts. A further bifunctional acid-base catalyst was prepared and studied by tethering proline to silica. In this case, the catalyst was chiral and was tested in the asymmetric aldol reaction between acetone and 4-nitrobenzaldehyde. Grafting methods with and without protecting groups for the active sites on proline were investigated. Remarkably the optimised supported proline catalysts showed higher activities and higher enantioselectivities than proline in homogeneous solution, and showed minimal loss in activity with time. Both activity and enantioselectivity depended strongly on the nature of the reaction solvent.
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de, Albuquerque Fragoso Danielle Munick. "Lignin conversion to fine chemicals." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/30847/.
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The large availability of Kraft lignin as an industrial by-product and its polyaromatic characteristic, is ideal to consider the potential for recycling it into fine chemicals. To depolymerise lignin, solvolysis and hydrogenolysis experiments were performed. This research considered whether the low yields of products (fine chemicals) were related to the low content of β-O-4 bonds or if it was also associated to the dissolution of lignin in the solvent solution employed in the reactions. The type of solvents chosen to check the dissolution effect were those with low cost and were more sustainable than traditional solvents. Water, ethanol, isopropanol (IPA) and acetone were used. The water mixtures were applied in the tests in various proportions (25:75, 50:50, 75:25 solvent/water v:v). Due to their ability to break C-C and C-O bonds in lignin model compounds [1][2], the efficiency of platinum and rhodium in these reactions supported on alumina was also studied. It was found that the non-catalysed (solvolysis) and catalysed reactions showed different selectivities but similar overall yields ~ 10 % wt of monomeric phenols. The difficulty in increasing yields was mainly associated with the highly condensed character of Kraft lignin and re-polymerisation issues. To achieve an understanding of Kraft lignin depolymerisation, isotopic labelling reactions were completed in the presence of deuterated solvents as well as deuterium gas. This gave information on how Kraft lignin depolymerises, the influence of solvent to products formation and the involvement of hydrogen in the rate determining steps in the reactions. These results have led to an initial mechanistic understanding on how this complex molecule may yield alky-phenolic compounds. It was revealed that the solvent was directly involved in the products’ formation and that they were not generated by simple thermolysis. In addition, the presence of catalysts and hydrogen influenced product formation. The compounds showed different kinetic isotopic values, suggesting that each of these molecules came from individual mechanisms, highlighting the complexity of their formation. This was a relevant study as most of lignin depolymerisation mechanistic insights are based on model compounds and not on lignin itself. It was of interest to this project to explore not only different catalysts and their relationship to lignin depolymerisation, but also different lignin types. A simple pre-treatment for lignin extraction using sawdust (from oak and birch wood) in a Parr autoclave reactor in the presence of hydrogen, solvent and high temperature was developed. The lignins obtained after the pre-treatment were named parr-lignin and successfully resulted in polyaromatic molecules with less condensed character compared to lignins from Soda or Kraft pulping. Reactions were carried out with these lignins and a sugar-cane lignin. 4 5 Different catalytic systems with these lignins were investigated and how depolymerisation was affected by the metal and support used. The catalysts involved in the reactions included platinum, rhodium, nickel and iron. Various supports such as alumina, zirconia and carbon were tested along with the metals described. It was found that the supports were not inert in these experiments presenting catalytic activity. Materials with low surface area (zirconium catalysts) gave a poor performance compared to the others. In addition, nickel, a non-noble metal, showed as good a catalytic effect in the depolymerisation of these lignins as Pt and Rh. The components in the system influenced the reactions to different extents, especially product distribution. The catalysts had different selectivities and the solvents were not only dissolving lignin but also influencing the results. GPC analysis was performed to give an overview of the condensed level of these lignins and degrees of depolymerisation compared to the original material. GC-MS enabled the identification and quantification of 18 monomeric compounds. The post reaction characterisation of selected alumina catalysts (Pt/Al2O3, Ni/Al2O3 and Al2O3) was performed using XRD, BET, CHN, TPO and Raman Analysis to study the nature of the carbonaceous layer deposited on these materials. The work showed that after reaction the catalysts turned black in colour and the carbon laydown consisted of not only one simple type of carbon, and included graphitic species. The amount of carbon deposited depended on the type of lignin. Oak and birch parr-lignins had the highest and lowest amount of carbon over the catalysts respectively. No obvious trend relating to the type of catalyst, lignin and solvent used to the carbon nature was identified. This work showed that lignins with less condensed nature were less susceptible to solvolysis and more to hydrogenolysis. For example, sugar-cane lignin gave 3.9% of phenolic compounds in the solvolysis while reaction with Rh/Al2O3 gave 12.9% of products. This indicated that more selective cleavage of bonds were promoted by heterogenous catalysts. The results suggested that some compounds were mainly generated via dealkylation and hydrodeoxygenation, allowing a future possibility to generate target molecules. These results were mainly due to the presence of more labile bonds, vulnerable to hydrogenolysis. Highlighting that prior to depolymerisation, the pre-treatment used to extract lignin must be appropriate to avoid depletion of the alkyl-aryl ether bonds (β-O-4 bonds, especially) relevant for fine chemicals generation.
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McLoughlin, C. M. "Microwave drying of pharmaceutical and fine chemical molecules." Thesis, Queen's University Belfast, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273046.
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Chan, Chun Wong Aaron. "Ultraselective nanocatalysts in fine chemical and pharmaceutical synthesis." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:866296af-5296-4d2e-8e52-6499dacaef0f.
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Surface catalysed reactions play an important role in chemical productions. Developments of catalyst requiring high activity whilst improving on product selectivity can potentially have a profound effect in the chemical industry. Traditional catalyst modifications were focused on tuning the size, shape and foreign metal doping to form well defined metal nanoparticles of unique functionalities. Here, we show new approach to engineering of metal nanocatalysts via a subsurface approach can modify the chemisorption strength of adsorbates on the surface. Carbon modified nanoparticles were synthesised using glucose to stabilise Pd nanoparticles at a molecular level. Upon heat treatment, the carbonised glucose encapsulated the Pd nanoparticles with carbon atoms take residence in the octahedral holes (15 at.%). These materials were tested in liquid phase stereoselective hydrogenations of 3-hexyn-1-ol and 4-octyne. The former has importance in the fragrance industry towards the production of leaf fragrance alcohol. It was shown for the first time that the geometrically and electronically modified Pd with interstitial carbon atoms reduced the adsorption energy of alkenes, ultimately leading to higher reaction selectivity. Boron modified Pd nanoparticles was synthesised using BH<sub>3</sub>.THF in the liquid phase. The material possess high B interstitial saturation (20 at.%), which can be synthesised for the first time below 100°C. These materials were tested in the liquid phase selective hydrogenation of various alkynes and 2-chloronitrobenzene, of which the latter has importance in the pesticides industry. Kinetic modelling on the hydrogenation of 4-octyne suggests these subsurface occupied B does play a pivotal role on increasing the reaction selectivity, as removal of these species lead to decreased selectivity. Au nanoparticles were synthesised and characterised using H<sup>13</sup>COOH NMR. The new liquid NMR characterisation method is successfully applied to examine the chemisorption strength of metal nanoparticles. An attempt to synthesise PVP capped B modified Pd nanoparticles with the above NMR characterisation was investigated. It is believed the examples of subsurface atom modifications as shown here may offer future catalyst developments in this area.
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Burmenko, Irina. "Brownian dynamics simulations of fine-scale molecular models." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32330.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005.<br>Includes bibliographical references (leaves 105-111).<br>One of the biggest challenges in non-Newtonian fluid mechanics is calculating the polymer contribution to the stress tensor, which is needed to calculate velocity and pressure fields as well as other quantities of interest. In the case of a Newtonian fluid, the stress tensor is linearly proportional to the velocity gradient and is given by the Newton's law of viscosity, but no such unique constitutive equation exists for non-Newtonian fluids. In order to predict accurately a polymer's rheological properties, it is important to have a good understanding of the molecular configurations in various flow situations. To obtain this information about molecular configurations and orientations, a micromechanical representation of a polymer molecule must be proposed. A micromechanical model may be fine scale, such as the Kramers chain model, which accurately predicts a real polymer's heological properties, but at the same time possesses too many degrees of freedom to be used in complex flow simulations, or it may be a coarse-grained model, such as the Hookean or the FENE dumbbell models, which can be used in complex flow analysis, but have too few degrees of freedom to adequately describe the rheology. The Adaptive Length Scale (ALS) model proposed by Ghosh et al. is only marginally more complicated than the FENE dumbbell model, yet it is able to capture the rapid stress growth in the start-up of uniaxial elongational flow, which is not predicted correctly by the simple dumbbell models. The ALS model is optimized in order to have its simulation time as close as possible to that of the FENE dumbbell.<br>(cont.) Subsequently, the ALS model is simulated in the start-up of the uniaxial elongational and shear flows as well as in steady extensional and shear flows, and the results are compared to those obtained with other competing rheological models such as the Kramers chain, FENE chain, and FENE dumbbell. While a 5-spring FENE chain predicts results that are in very good agreement with the Kramers chain, the required simulation time clearly makes it impossible to use this model in complex flow simulations. The ALS model agrees better with the Kramers chain than does the FENE dumbbell in the start-up of shear and elongational flows. However, the ALS model takes too long to achieve steady state, which is something that needs to be explored further before the model is used in complex flow calculations. Understanding of this phenomena may explain why the stress-birefringence hysteresis loop predicted by the ALS model is unexpectedly small. In general, if polymer stress is to be calculated using Brownian dynamics simulations, a large number of stochastic trajectories must be simulated in order to predict accurately the macroscopic quantities of interest, which makes the problem computationally expensive. However, recent technological advances as well as a new simulation algorithm called Brownian configuration fields make such problems much more tractable. The operation count in order to assess the feasibility of using the ALS model in complex flow situations yields very promising results if parallel computing is used to calculate polymer contribution to stress. In an attempt to capture polydispersity of real polymer solutions, the use of multi-mode models is explored.<br>(cont.) The model is fit to the linear viscoelastic spectrum to obtain relaxation times and individual modes' contributions to polymer viscosity. Then, data-fitting to the dimensionless extensional viscosity in the startup of the uniaxial elongational flow is performed for the ALS and the FENE dumbbell models to obtain the molecule's contour length, bmax. It is found that the results from the single-mode and the four-mode ALS models agree much better with the experimental data than do the corresponding single-mode and four-mode FENE dumbbell models. However, all four models resulted in a poor fit to the steady shear data, which may be explained by the fact that the zero-shear-rate viscosity obtained via a fit to the dynamic data by Rothstein and McKinley and used in present simulations, tends to be somewhat lower than the steady-state shear viscosity at very low shear rates, which may have caused a mismatch between the value of ... used in the simulation and the true ... of the polymer solution. As a motivation for using the ALS model in complex flow calculations, the results by Phillips, who simulated the closed-form version of the model in the benchmark 4:1:4 contraction- expansion problem are presented and compared to the experimental results by Rothstein and McKinley [49]. While the experimental observations show that there exists a large extra pres- sure drop, which increases monotonically with increasing De above the value observed for a Newtonian fluid subjected to the same flow conditions, the simulation results with a closed-form version of the FENE dumbbell model, called FENE-CR, exhibit the opposite trend.<br>(cont.) The ALS-C model, on the other hand, is able to predict the trend correctly. The use of the ALS-C model in another benchmark problem, namely the flow around an array of cylinders confined between two parallel plates, also shows very promising results, which are in much better agreement with experimental data by Liu as compared to the Oldroyd-B model. The simulation results for the ALS-C and the Oldroyd-B models are due to Joo, et al. [28] and Smith et al. [50], respectively. Overall, it is concluded that the ALS model is superior to the commonly used FENE dumb- bell model, although more work is needed to understand why it takes significantly longer than the FENE dumbbell to achieve steady state in uniaxial elongational flows, and why the stress birefringence hysteresis loop predicted by the ALS model is much smaller than that of the other rheological models.<br>by Irina Burmenko.<br>S.M.
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Breed, Ashley Wayne. "Beneficiation of fine coal using the air-sparged hydrocyclone." Master's thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/21831.
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Bibliography: pages 173-185.<br>The Air-Sparged Hydrocyclone (ASH) is a high capacity flotation device which is alleged to be more efficient for the flotation of fine particles than conventional flotation equipment. The principal aims of this thesis were to investigate the use of an ASH in the flotation of South African coal ultrafines (-150 micron), and to determine the effect of various design and operating parameters on the performance of the process, in terms of the product yields and grades obtainable. The testwork was carried out on a typical Witbank coal, from the Kleinkopje Colliery, with an ash content of 23.7 %. The coal was characterised by means of size, ash-by-size and float-and-sink analyses. Batch flotation experiments were carried out to provide a benchmark against which the ASH could be compared. Preliminary ASH work was carried out to determine the required collector and frother dosages and the optimal slurry feed rate.
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Farrell, E. "Microwave-assisted drying of regulated pharmaceutical and fine chemical compounds." Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431608.
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Mullan, E. "Use of a rotating disc reactor for fine chemical synthesis." Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432520.
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Mosavat, Nasim. "Electrokinetic Treatment of Fine-grained Soils with Chemical Enhancement Solutions." Thesis, Griffith University, 2014. http://hdl.handle.net/10072/367245.
Texte intégralRésumé :
The electrokinetic (EK) soil treatment method is a comparatively new technology. It is being investigated in some parts of the world as a feasible and practical in-situ soil remediation and treatment method. When the application of traditional ground improvement techniques (e.g. surcharge, preloading, etc) is not practical for a particular situation, innovative approaches such as EK technique can be considered. The principles of the EK treatment method involve applying a low direct current (DC) or a low potential gradient to arrays of electrodes inserted in the low permeable soils that cannot readily drained. The EK method is applicable to fine- grained soils such as clays, silty clays and clayey silts, possessing specific mineralogical properties, which are electrically and chemically active.
When a DC electric potential is applied to the soil, it simulates migration of electricity, pore water, ions and charged particles across the soil, creating several complex mechanisms such as electrolysis, electro-osmosis, electromigration and electrophoresis, respectively. This technique can also be incorporated/ enhanced by introducing desirable non-toxic chemical stabilisers such as lime or saline solutions to the soil at the appropriate electrode. The combined effects of these processes together with various geochemical reactions alter the chemical composition of the soil porous medium and hence modify the physicochemical, mechanical and engineering properties of the soil. Although the EK technology has been proven to be applicable in many laboratory bench scale experiments and field tests, some complicated features such as electrochemical reactions and changes in soil properties are not fully understood. Therefore, there is a need to conduct this research for a better understanding of the improvements in problematic soils and the efficiency of this technology.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>Griffith School of Engineering<br>Science, Environment, Engineering and Technology<br>Full Text
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Zavahir, Fathima Sifani. "Development of visible light photocatalysts for organic fine chemical production." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/96049/1/Fathima%20Sifani_Zavahir_Thesis.pdf.
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Devising new photocatalysts that can harvest light energy to drive chemical processes is in the forefront of chemical research. It aims at limiting the use of depleting fossil fuel energy, better understanding optical properties of materials and developing green chemical synthesis processes. During this doctoral work, three different types of photocatalysts, based on titanium dioxide, gold nanoparticles and vanadium clusters, have been designed and evaluated for synthetically important organic chemical reactions under visible light irradiation at near ambient conditions.
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Lam, Cheun U. You Van. "Solids motion in fluidised beds of fine particles." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/809/.
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Although there has been ongoing research on fluidised beds for the past 70 years, the interaction between particles and rising bubbles and the general solids motion in bubbling fluidised beds are still not fully understood. The work presented in this thesis uses the method known as Positron Emission Particle Tracking (PEPT) to track the motion of a single radioactively labelled particle inside a fluidised bed. Recent developments in PEPT include new ways of labelling micron sized tracer particles that can be as small as 60 μm and the new mobile camera system also known as the Modular PEPT camera that can follow particle trajectories in equipment of various sizes and geometries. So far, PEPT has only been used to investigate fluidised beds of Geldart group B and D particles due to the previous limitation in the size of tracer particles. The results outlined in the thesis include group A particles (aluminium oxide) fluidised at atmospheric pressure in an 8 cm internal diameter bed and at elevated pressure in a 15 cm internal diameter bed and group B particles (sand) fluidised at atmospheric pressure in a 15 cm internal diameter column. The three areas that have been investigated are the use of particle trajectories to measure the properties of rising bubbles and the dispersion and general solids motion together with solids circulation as a measure of particle mixing. The protocols required to process the PEPT data used in the thesis were originally set by Stein (1999) but modified and improved versions are proposed and used. The PEPT results are in general agreement with existing models and results published by other researchers. A set of Matlab programs to analyse the results of PEPT experiments and which can be readily used by other users is presented.
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Muszalski, Piotr. "The role of ultrafine particles in oil sands fine tailings reduction." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/9700.
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Fine tailings exhibit extremely poor dewatering characteristics. The research presented here deals with two closely related projects. The first project concentrated on finding an efficient treatment method for already existing fine tailings. The second project was to evaluate process modifications aimed at fine tailings reduction and to develop an understanding of the effect of electrolyte in the process water of the characteristics of fine tailings. The behavior of ultrafines separated from fine tailings was further investigated. A $\sp2$H NMR technique was applied to determine the gelation rates for ultrafines at different electrolyte concentrations. The gelation concentration was determined using ultrafines suspensions diluted with salt solutions. Results indicate, that while gelation time varies from minutes to weeks, the gelation concentration is always about 3-4 wt%, even at an extremely high salt concentrations further floc densification (dewatering) is impossible. Although adequate floc densification could not be achieved using chemical treatment, dewatering was increased markedly using freeze-thaw (a physical method). To evaluate process modifications, samples of different process streams produced during comparison pilot plant runs performed at Syncrude Canada Ltd. were investigated. The aggregation state and distribution of ultrafines were determined in all stream samples. In conjunction with the characteristics of parent oil sand ores, results prove that the settling rate was different only up to the point where the gelation onset concentration of the ultrafines fraction was reached, regardless of the ionic composition of water. Modifications to the extraction process resulted only in marginal differences in the characteristics of the discharge streams. The final volume of fine tailings depends on the ultrafine content in the oil sand ore, and not on the type and concentration of the electrolyte in th process water. Although modified extraction processes resulted in faster settling, the modification produced "dirtier" (containing more clay) secondary froths, thus bringing about other process problems.
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Mwale, Adolph Ntaja. "A mathematical model for predicting classification performance in wet fine screens." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/20122.
Texte intégralRésumé :
Screening is a well-known classification process in the minerals processing industry. The process involves separation of fine particles from coarse particles based on size and is applicable to both dry and fine screening. Fine screening is normally carried out wet. Until recently, fine wet screening had been limited to relatively low throughput applications. Developments in the recent past have seen the evolution of fine screening to high capacity applications. It has found application in operations such as closed circuits with a mill in place of hydrocyclones. However, even though developments are increasing, there has been a process model developmental lag. A fine wet screen model that can be used for unit simulation purposes to predict screen performance outcomes or integration into other models to simulate and predict process performance is necessary. Most existing screen models are for dry and coarse screening applications. This thesis is aimed at developing a fine wet screen process model for predicting wet screening performance in the 45 - 150 μm range. Pilot plant testwork was conducted using a UG2-Chrome ore blend as feed.
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Bunt, John Reginald. "Development of a fine coal beneficiation circuit for the Twistdraai Colliery." Master's thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/20196.
Texte intégralRésumé :
Bibliography: p. 167-178.<br>The principal aim of this thesis was to develop a fine coal beneficiation circuit for the Twistdraai Colliery capable of achieving.a saleable 10.0% ash (28 MJ/kg CV) product. Gravity circuit testing involved a comparative study of a conventional double-stage Spiral circuit and a Stokes upward-current washer when treating Twistdraai <850J.1m x 106J.1m fine coal. In addition, froth flotation technologies, in the form of the Microcel column and the Jameson cell were also tested in order to ascertain whether they can be suitably applied · to the Twistdraai naturally fine coal to produce a 10.0% ash steam coal export product. In this investigation, the Twistdraai fine coal surface was characterised by size as well as by density. Functional group determination included the measurement of the coals hydroxyl, carboxylic and total acid groups, since these exert the most important influence on the properties of the coal surface. These are supported by contact angle measurements, petrographic analysis and washability measurements in orde:r to determine the oil wettability of the coal fractions prior to flotation testing. The results described and discussed in this thesis show that it was possible to recover the desired quality of product by employing split-stream processing of the (850J.1m x 0) Twistdraai fine coal circuit feed. This was achieved by application of both gravity concentration and froth flotation technologies treating specific particle size ranges.
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Stonestreet, Paul. "Reverse flotation : a novel process for the beneficiation of fine coal." Doctoral thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/21990.
Texte intégralRésumé :
Bibliography: pages 157-162.<br>The beneficiation of ultrafine coal by froth flotation is a widely used process, and its importance for the treatment of -0.1 mm coal has been appreciated of late in South African coal washing plants. A number of problems adversely affect the efficiency of this process, such as poor liberation, poor floatability, gangue entraiment/entrapment, and high mass recovery which can lead to throughput limitations in coal flotation equipment. Reverse coal flotation is a novel process which has been proposed to address three problems occurring in the conventional, "forward flotation" of coal, namely: high mass recovery, gangue entrainment and the variability of floatability of South African coals. In this process, the entire gangue fraction in the coal would. be floated in a single step process, with the clean coal product reporting as the tailings. To the author's knowledge, no_ such process has been investigated previously for coal flotation. In this thesis, a reverse flotation process for ultrafine coal beneficiation was developed from first principles. In order to obtain a clear understanding and interpretation of experimental flotation results, artificial feed mixtures consisting of blends of "pure" gangue and "pure" coal were used for a large section of the experimental testwork. Having established the technical viability of the process on these artificial mixtures, the flotation work was extended to four South African run-of-mine coals. The study comprised the selection of suitable reagents for reverse flotation and the evaluation of these reagents experimentally. Experimental testwork comprised batch adsorption tests, and flotation tests in a conventional, sub-aeration laboratory batch cell and in a laboratory column flotation cell. The process was evaluated in terms of coal recovery into the product and gangue removal in the waste stream, and its metallurgical performance was compared to conventional flotation using both the artificial feeds and r.o.m. coals.
20
Roldan-Villasana, Edgardo Javier. "Modelling and simulation of hydrocyclone networks for fine particle processing." Thesis, University of Manchester, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264312.
Texte intégral
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Spillmann, Adrian. "Flowability modification of fine powders by plasma enhanced chemical vapor deposition /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17927.
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Moser, Matthew A. "Micro-and pulsed-plasmas fine tuning plasma energies for chemical analysis /." Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2534.
Texte intégralRésumé :
Thesis (Ph. D.)--West Virginia University, 2002.<br>Title from document title page. Document formatted into pages; contains ix, 99 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
23
Lancaster, Thomas M. (Thomas Michael) 1977. "Silica mesocellular foam and carbon nanofoam for fine chemical synthesis and separation." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29373.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2004.<br>Includes bibliographical references.<br>In chromatography, the selective separation for large molecules, polymers, and proteins is of particular interest. To achieve quality separations, the stationary phase should exhibit pore diameters greater than 10 nm to facilitate the diffusion of large analytes throughout the stationary phase. In packed-bed applications, narrow particle and pore size distributions and uniform particle shape would lead to improved separations. Thus, spherical stationary phase particles are often preferred, but the challenge has been to combine spherical particle morphologies, high surface areas, large mesopores, and narrow pore size distributions. We have successfully created a new three-step synthesis of spherical MCF (S- MCF) particles utilizing sodium fluoride as a condensation catalyst. The approach allowed for independent control over S-MCF particle and pore size, and was extended to other non-ordered porous silicas. The S-MCF particles were engineered into a reverse- phase chromatographic column and achieved good separation ability for a mixture of aryl ketones. By relating chromatographic performance to S-MCF surface silanol chemistry, an improved S-MCF chromatographic support was realized, which rivaled the separation capability of a commercially available chromatographic support. The asymmetric Diels-Alder (ADA) reaction is very useful in building complex chiral molecules through the formation of chiral carbon ring structures, and it presents an excellent route for generating new therapeutic molecules. Although these compounds are of great importance, homogeneous ADA catalysts exhibit moderate activities and are not readily recovered and reused. This has prevented the ADA reaction from being widely practiced in the pharmaceutical industry.<br>(cont.) To create more attractive catalysts, MCF was used to anchor chiral bisoxazoline-copper(II) complexes for the ADA reaction. We have examined the effect of catalyst environment on activity and selectivity through the use of different catalyst ligands, linker groups, and silanol capping agents. The MCF-immobilized catalysts showed enhanced activity compared to their homogeneous counterparts, and the phenomenon was correlated to bisoxazoline ligand loading on the MCF surface. Batch recycling experiments and continuous ADA reactor trials showed that the MCF-anchored catalysts were reusable and stable. Catalytic performance was measured through in situ infrared spectroscopy, and a Michaelis-Menten kinetic model with product inhibition was applied to determine relevant kinetic parameters for the best heterogenized catalyst. The Heck reaction is a powerful synthetic tool in organic chemistry for C-C bond formation through a liquid-phase reaction between aryl halides and alkenes. It has great industrial potential, but the Heck coupling reaction catalysts have traditionally suffered from low oxygen tolerance and poor reusability due to palladium cluster growth, agglomeration and oxidation. In this work, a new mesoporous and crystalline carbon, carbon nanofoam (CNF), was examined as a Pd cluster support for the coupling of 4-bromoacetophenone and n- butyl acrylate. Using CNF as a support, we successfully synthesized Pd/CNF catalysts using a vapor grafting approach and demonstrated high activities for the Heck coupling at 140⁰C. The Pd/CNF catalysts showed remarkable performance enhancements compared to Pd/activated ...<br>by Thomas M. Lancaster.<br>Ph.D.
24
Deglon, David Alan. "A hydrodynamic investigation of fine particle flotation in a batch flotation cell." Doctoral thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/5375.
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Loponov, Konstantin Nikolayevich. "Development of a scalable photochemical reactor for syntheses of fine chemicals." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/35523/.
Texte intégralRésumé :
This study is in the area of sustainable chemical technology and is ultimately aimed at developing a novel generic approach towards efficient, clean, safe and scalable synthesis of important intermediates for pharmaceutical applications and catalysis using nonthermal activation of chemical bonds. Current study is focused on molecular activation by light, specifically addressing the class of singlet oxygen reactions. A laboratory-scale annular recirculating photoreactor and a scalable microreactor unit were designed, assembled and tested in oxygenation of α-pinene and stereoselective oxygenation of homoallylic alcohols by the photogenerated singlet oxygen. Efficiencies of light utilization and the quantum yields of the reactions for different sources of light in various lamp-reactor geometries were quantified using actinometry. It was shown that optimal thickness of the reaction layer, high intensity of light and elevated oxygen pressures in continuous gas-liquid segmented flow are crucial for both safe and efficient oxygenation. This study proved the viability of a novel concept of compact reactors with embedded light emitting diodes. Finally, a methodology of efficient oxyfunctionalization of allylic compounds was developed. Following the developed methodology, the applicability of functional nanomaterials based on pure and dye-modified porous silicon as heterogeneous photosensitizers of singlet oxygen was studied in detail. It was demonstrated that the photosensitizing efficiency of all the samples is much lower than that of conventional dye photosensitizers. Low activity of the novel photosensitizers was attributed to quenching of the photogenerated singlet oxygen by the surface quenching groups of porous silicon, low quantum yield of photoluminescence in the case of pure porous silicon and to thermodynamically favorable quenching of the photoexcited porphyrin states due to energy/electron transfer to silicon nanocrystals in the case of dye modified porous silicon.
26
Yalamaç, Emre Akkurt Sedat. "Preparation of Fine Spinel and Cordierite Ceramic Powders By Mechano-chemical Techniques/." [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000434.pdf.
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Jeong, Sueng Won. "Influence of physico-chemical characteristics of fine-grained sediments on their rheological behavior." Thesis, Université Laval, 2006. http://www.theses.ulaval.ca/2006/24116/24116.pdf.
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Chatterjee, Sourav. "Design of a radiofrequency heated micro trickle bed reactor for fine chemical synthesis." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.695300.
Texte intégralRésumé :
Multi phase catalytic reactions such as hydrogenations, oxidations etc. are frequently encountered in the pharma and fine chemical industries. Multiphase reactor systems generally used in such processes were targeted for improvement in this research. This research project begins by analysing the benefits of process intensification by scaling down of conventional reactor systems. A brief survey on different microreactor technologies were carried out in the first chapter, which was then followed by chapter 2, describing different experimental methods adopted in this research. In the first part of the research, multi phase microreactor in the form of a micro-trick1e bed was designed. The reactor was heated from inside out by coupling it with the phenomenon of non-contact induction heating. Such reactor design was further extended in the second part of the research to create dual isothermal temperature zones inside a single reactor, where two different catalyst beds were placed in a cascade configuration. This led to the realization of a novel catalyst and temperature compartmentalized reactor system. Cascade catalytic reaction of citronellal to menthol was chosen as a model reaction. The high heat transfer rates obtained in the radio-frequency heated micro trickle bed reactor was further exploited in generating periodic temperature oscillations of the catalyst bed and this led to the design of a transient reactor system. It was observed that selectivity toward the semi-hydrogenated product increases around 10 to 12% for periodic temperature oscillation of the reactor bed when compared with the reactor maintained at a steady temperature. Finally the existing design of the micro-trickle bed reactor (MTBR) was scaled-up to a six times scale up factor. The selective hydrogenation of acetylene alcohol was chosen as a model reaction for testing the reactor performance. A conceptual design of a pilot plant, involving such scaled-up MTBRs for a target production of 1 kg/day was also proposed.
29
CODAZZI, VERA. "Breaking phylogenetic barriers for fine and bulk chemical products in engineered Saccharomyces cerevisiae." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/19692.
Texte intégralRésumé :
Industrial biotechnologies allow today to obtain both fine and
bulk chemicals and yeasts as cell factories can produce many
products belonging to both field (Branduardi et al., 2008, Porro
and Branduardi, 2009). Among yeasts, Saccharomyces cerevisiae
still represents the microorganism of election to develop such cell
factories. As regard bioethanol production, yeasts utilization is well
established for its natural fermentation ability, but new generation
biofuels require the development of strain more and more robust,
able to face conditions imposed by the process that should be as
cheaper and more profitable as possible. In this direction, processes
that use lignocellulosic feedstock for bioethanol production (the so
called second generation biofuels) are still in development (NEMO
project-Novel high performance Enzymes and Micro-Organisms for
conversion of lignocellulosic biomass to ethanol, seventh framework
program). This means that the cell factory has to be deeper and
deeper investigated in structures and pathways trying to find good
targets for improving the robustness. Among the many different
functions, cell cytoplasmic membrane plays a key role in cell
homeostasis and is deeply involved in facing and reacting to stressing
conditions, so it can represent a good target for direct improvements
of laboratory as well as industrial strains. Fishing in Arabidopsis
thaliana genome, a potentially interesting gene was found,
codifying for a Temperature Induced Lipocalin, named TIL. As it
has positive effects in plants in unfavourable situations (Charron
et al., 2008), TIL was expressed in S. cerevisiae and the
recombinant strains compared with the parental counterpart
under some of the stresses typical of industrial processes. The
recombinant yeasts show an increased tolerance towards heat shock
and to the presence of hydrogen peroxide and organic acids.
In detail TIL expressing strain generate lower levels of ROS and
accumulate less amounts of reactive electrophile species generated
after membrane lipids fragmentation.
Another industrial field that is gaining more and more importance
is represented by bioplastics not coming from petrochemical
sources. Vegetable oils derived fatty acids are interesting as bulk
compounds for the synthesis of biopolymers, even if they have to
be previously modified to possess two chemically reactive groups
at molecules extremities. High catalytic activity and stability
together with high versatility in reaction of performed by bacteria
cytochromes answered to this need.
The heterologous expressed B. subtilis cytochrome CYP102A2 in S.
cerevisiae showed some activity, measured in terms of NADPH
consumption towards fatty acids of different chain length,
interestingly also towards short chain fatty acids. However as CYP is
able to catalyze different type of reaction involving NADPH
consumption (hydroxylation, oxidation and epooxidation as
example), the products will be further characterized to
understand what kind of modifications are carried out on the
tested substrates. Considering the valuable reactions that
cytochromes P450 are able to catalyze on a vast variety of substrates
(fatty acids, steroids and a multitude of non natural compounds such
as drugs, organic solvents and hydrocarbon products), their
successful expression in yeast could open the possibility to develop
sustainable processes in alternative to classical chemical synthesis.
Because of the nice and positive results, S. cereviasiae potential as
cell factory was deeper exploited for the expression of a whole plant
biosynthetic pathway. In detail, yeast was engineered to express the
pathway leadind to the formation of glucobrassicin, a nutraceutical
indicated as a potential cancer chemoprotective agent. In this work
we describe the construction of a recombinant S. cerevisiae strain
able to produce glucobrassicin. Despite some investigation about
possible strain optimization through the employment of
multicopy plasmids, the final producer will exploit only
integrative vectors and the described findings and the process of
production were deposited as patent application [Mauro Magnani, E.
Bartolucci, Danilo Porro, Paola Branduardi, Vera Codazzi, Umberto
Benatti, Gianluca Damonte, Giovanni Schippa e Stefano Bianchini
Sviluppo di una cell factory ricombinante per la produzione di
Glucobrassicina]. Specific analysis on biosynthetic intermediates
suggest steps on which focusing the attention to further improve the
glucobrassicin production levels.
Despite the number of biotechnological processes based on
engineered microorganisms for the production of metabolites is still
limited in comparison with the potentiality expressed at lab scale, the
studies about strain robustness and heterologous pathway
optimization are going to change that situation very soon.
30
Scott, Angelique J. "Source apportionment and chemical characterisation of airborne fine particulate matter in Christchurch, New Zealand." Thesis, University of Canterbury. Environmental Science, 2005. http://hdl.handle.net/10092/7576.
Texte intégralRésumé :
Environment Canterbury has a proposed plan to address elevated wintertime particle concentrations in Christchurch and other Canterbury towns. The proposed plan sets out air quality objectives for Canterbury and specifically targets the main source of wintertime particles, residential heating. Environment Canterbury is reliant on the plan strategies to meet the targets specified, and to meet the recently established National Environmental Standard for PM₁₀. The contribution of residential heating, relative to other sources, has been quantified by emission inventory (coupled with a box model). The appropriateness of measures contained in the proposed plan is debated by some, who are sceptical of the inventory results. Progress in air quality management in Christchurch would be facilitated by improving the understanding of PM ₂.₅ and its sources by undertaking an alternative approach to source attribution.
A source apportionment study was therefore conducted during 2001/2002 to address these issues. This aimed to determine the chemical composition of fine particles (PM ₂.₅) in Christchurch, investigate and trial a receptor model, identify the main sources contributing to PM ₂.₅ and estimate relative source contributions with a view to using the technique to monitor plan strategy effectiveness. This is the first time that the Positive Matrix Factorisation (PMF) receptor model has been applied to seasonal PM ₂.₅ data in New Zealand.
PM ₂.₅ samples were collected at St Albans, Christchurch during 2001 and 2002. The filters were analysed for gravimetric mass, elemental species and inorganic ions (24-hour averages). Organic and elemental carbon were measured using an automatic carbon analyser. The final dataset comprised 159 observations and 15 chemical species. PM ₂.₅concentrations were seasonally distributed with maximum concentrations occurring in winter. Major elemental constituents were organic and elemental carbon, sulphate, nitrate, sodium, chlorine and sulphur. Combustion-related species were highest in winter and those derived from natural sources (e.g. marine aerosol) predominant in summer. Five factors were resolved using the PMF receptor model: these were identified as wood combustion, marine aerosol, motor vehicles, secondary particulate and aged aerosol. On average, 92% of PM ₂.₅mass was explained by the resolved factors. The most important source of PM ₂.₅, on average, during summer was aged aerosol and in winter was wood combustion. The results were evaluated against inventory-derived data; both methods clearly identified wood combustion as being the predominant source of peak wintertime PM ₂.₅ (92% and 89%, respectively). These results provide independent verification that residential heating is the greatest contributor to wintertime particles, adding to the "weight of evidence" required to justify strategies adopted in Environment Canterbury's proposed plan. Further use of receptor models was recommended as they provide source information unavailable from emission inventories/including contributions from natural sources and secondary particulate, and may be used to track effectiveness of policy implementation.
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Björk, Elisabeth. "Production and application of fine fractions made of chemical pulp for enhanced paperboard strength." Licentiate thesis, Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-40246.
Texte intégralRésumé :
For all kinds of paperboard packages, the bending stiffness of the paperboard is a crucial property. In multi-ply folding boxboard (FBB) grades, this is obtained by placing different stocks in the outer and centre plies of the board. In the outer plies, a stock with a high tensile stiffness is used, typically made from refined kraft pulp fibres. In the middle ply/plies a stock with more bulky properties is placed, typically comprising of a high proportion of CTMP (chemi-thermomechanical pulp). CTMP fibres are stiffer and more inflexible with poor bonding abilities resulting in low strength properties. To increase the bonding strength in the middle ply, broke, containing chemical pulp is added, and sometimes refined chemical kraft pulp as well. Both fibres and fines, i.e. smaller fibre fragments, in a pulp have a significant contribution to the properties of the product. Fines produced during refining of chemical pulp are especially beneficial for increasing the strength. To achieve pulp fraction with higher fines content the pulp can be fractionated with a micro-perforated screen basket; a fine fraction produced from a screen with very small holes will contain a large proportion of fines. By adding such a fine fraction to a middle ply stock, the bulk properties of the main pulp, for example a CTMP, can be conserved as less refining of this pulp is required to achieve the targeted strength properties. However, a drawback is that the fine fraction usually has a very low mass concentration after the screening process as a lot of water pass through the screen together with the fines and fibre fragments. The excess water must be removed to maintain the water balance of the papermaking process. Further, the larger volumes require extra pumping capacity. A resource-efficient production of a fine fraction must target a high fine fraction mass concentration and a high content of fines and short fibre fragments in order to be implemented industrially. The focus of the present work was on separation efficiency (i.e. the difference in fibre length distribution caused by screening) and process efficiency (i.e. the concentration of the fine fraction) for production of a fine fraction of chemical pulp by screening, and the utilisation of the fine fraction as strength agent. Pilot-scale fractionation trials with a pressure screen with different microperforated screen baskets were performed in order to evaluate how the separation efficiency and process efficiency were affected by parameters such as feed concentration, pulp type (hardwood or softwood kraft pulp), hole size of the screen, and refining treatment prior to screening. The trials were evaluated using fibre length distributions, flow rates and concentrations of viii the feed flow and the fractions. Here, two complementary quantitative measures, Proportion in fine fraction (for process efficiency) and Fine fraction enrichment (for separation efficiency), were developed. To evaluate the strength enhancing effect of the obtained fine fraction, a lab scale study was performed where the fine fraction of a highly refined pulp was compared with the highly refined pulp as strength agent for a CTMP. The results of this study were verified in a pilot paper machine trial. In a second pilot paper machine trial, sheets with different CTMP proportions in the middle ply were studied in order to find out if the bulk could be increased while maintaining strength, by using a fine fraction made from refined chemical pulp. Regarding process efficiency, it was found that the most important parameter to obtain a high fine fraction concentration was a high feed concentration. Further, a higher fine fraction concentration for a given screening process was also obtained when using hardwood pulp and refining the pulp prior to the screening process. A higher feed concentration also had a positive effect on the separation efficiency. Small holes and a smooth surface of the screen basket were also important to improve the separation efficiency. It was shown that, when used as a strength agent in a CTMP pulp, the fine fraction of highly refined kraft pulp was twice as efficient as the highly refined kraft pulp, when added at equal mass proportion. However, both in the lab and pilot trial the strength increase was accompanied by a decreased bulk. This was expected, and to avoid this the proportion of the bulky CTMP had to be increased. The pilot paper machine trial with an increased CTMP proportion in the middle ply and a fine fraction of refined kraft pulp as strength agent demonstrated that it was possible to produce sheets with an increased bulk and maintained z-strength.<br>Böjstyvheten är en viktig egenskap för alla sorters hårda förpackningar. I flerskiktskartong får man böjstyvhet genom att ha ytterskikt med hög dragstyvhet tillverkade av fibrer från kemisk massa och ett mittskikt med hög bulk från styva fibrer, ofta med en stor andel CTMP (kemitermomekanisk massa). CTMP-fibrer är styva men ger lägre styrka i arket. För att öka styrkan i mittskiktet tillsätter man utskott (kasserad kartong) som delvis innehåller kemisk massa, och ibland även ren högmald kemisk massa. Både fibrer och finmaterial (fines) har stor betydelse för slutproduktens egenskaper. Fines som skapas vid malning av kemisk massa är särskilt effektiva för att öka styrkan. Genom att fraktionera massa med en mikroperforerad sil kan man få en finfraktion med högt finesinnehåll. Mikroperforerade silar är effektiva för längdfraktionering av massa; fines anrikas i den fraktionen som passerar silen medan långa fibrer stannar i den andra fraktionen. Genom att använda en sådan finfraktion i mittskiktet kan man få tillräcklig styrka och samtidigt behålla mer av bulken från CTMP:n genom att man inte behöver mala den för att få styrka. En nackdel är att finfraktionen vanligtvis har väldigt låg masskoncentration eftersom mycket vatten passerar silen tillsammans med fines och fiberfragment. Detta extra vatten måste tas bort för att vattenbalansen i papperstillverkningsprocessen ska bibehållas. Dessutom kräver den större volymen ökad pumpkapacitet. För att kunna använda en finfraktion industriellt behövs en effektiv produktion med hög koncentration och högt finesinnehåll. Fokus i det här arbetet lades på separationseffektivitet (skillnaden i fiberlängdsfördelning som resultat av silningen) och processeffektivitet (koncentrationen i finfraktionen) för tillverkning av en finfraktion av kemisk massa genom silning samt dess utnyttjande som styrkehöjande tillsats i ett mittskikt av kartong. För att utvärdera hur separationseffektiviteten och processeffektiviteten påverkas av parametrar som koncentrationen i flödet in till silen, typ av kemisk massa (gjord av lövved eller barrved), hålstorlek i silen samt malningen av massan, gjordes fraktioneringsförsök i pilotskala med en trycksil med olika mikroperforerade silkorgar. Resultatet av fraktioneringen utvärderades med hjälp av fiberlängdsfördelningar, flöden och koncentrationer i flödet till silen och de två fraktionerna efter silen. För utvärderingen togs två olika utvärderingsmetoder fram: Proportion i finfraktionen (för processeffektivitet) och Finfraktionsanrikning (för x separationseffektivitet). För att utvärdera hur effektiv en finfraktion av kemisk massa var som styrkeadditiv i ett CTMP-ark gjordes labbförsök där tillsats av högmald kemisk massa jämfördes med tillsats av enbart en finfraktion av den högmalda kemiska massan. Resultaten verifierades med ett försök på en pilotpappersmaskin. I ett följande försök på pilotpappersmaskinen tillverkades ark med ökat CTMP-innehåll för att öka bulken, och med en tillsats av en finfraktion av kemisk massa som styrkeadditiv. När det gäller processeffektivitet var hög koncentration i flödet till silen den viktigaste parametern för att få hög koncentration på finfraktionen. Detta var också positivt för separationseffektiviteten, färre av de längre partiklarna hamnade i finfraktionen. Vidare blev finfraktionens koncentration högre för lövvedsmassa. En finfraktion som ska användas som styrkeadditiv ska vara tillverkad av mald massa, malning av massan var också fördelaktigt för finfraktionens koncentration. Små hål och en slät yta på silkorgen var också positivt för separationseffektiviteten. Som styrkeadditiv i CTMP var finfraktionen av högmald kemisk massa dubbelt så effektiv som den högmalda kemiska massan vid lika stor tillsats. Men i både labbförsök och pilotförsök minskade bulken när styrkan ökade. Det var väntat eftersom att ersätta en del av originalmassan som har hög bulk, med en finfraktion eller högmald massa, som båda har mycket lägre bulk, alltid minskar bulken på arket. För att undvika en bulkförlust måste massasammansättningen i arket ändras. Försöket på pilotpappersmaskinen med ökat CTMP innehåll och en finfraktion av mald kemisk massa som styrkeadditiv visade att det är möjligt att tillverka ett ark med högre bulk och bibehållen styrka.
32
Crilley, Leigh R. "Investigations of the physical and chemical properties of ambient fine particles in urban schools." Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/65336/1/Leigh_Crilley_Thesis.pdf.
Texte intégralRésumé :
This thesis reports a comprehensive study on the physical and chemical properties of airborne particles in Brisbane, especially around schools. The sources and potential toxicity of the particles were identified, enabling an assessment of the contributing factors to children's exposure at school. The results from this thesis give a quantitative estimate of the range of airborne particles that children are exposed to at urban schools with different traffic conditions.
33
Mabote, Seipati. "Development of a wet fine screen model integrating the effect of operating and design variables on screening performance." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20419.
Texte intégralRésumé :
Mineral processing is the process that involves liberation and beneficiation of valuable constituents of an ore. Several physical beneficiation processes exist and one such process is classification. Screens are classification devices sometimes used in the classification stage of closed grinding circuits to separate mill product into different size classes. Poor classification of particles results in reduced throughput, high power consumption and over - grinding. Most of the research on screening has been done in scalping applications or classification at relatively large cut sizes. There is limited work done on screening at feed sizes of minus 150 μm and there are no robust models for wet fine screening application for use in circuit simulation studies. The effect of feed flow rate, solids concentration and aperture size on wet fine screening performance was evaluated in this study. The range of values of the factors investigated were the feed rate (9, 13, 19, 25, 30 and 35 t/h), screen aperture size (45, 75, 106 and 150 μm) and solids content (30, 40, 50 and 60%). A pilot Derrick screen plant at Mintek in Johannesburg was used for the experiments on a UG2 and chromite ore blend. Screen undersize and oversize samples were collected for particle size distribution analysis and mass balance calculations. The samples collected were filtered, de - lumped and split down to masses ranging between 200 and 300 grams for wet screening using the Malvern MasterSizer particle analyser. The results were used to analyse the effect of the investigated factors on the wet fine screening performance. These results were used to develop a wet fine screening model. Results indicate that increased feed flow rate and solids concentration lead to finer cut sizes, reduced sharpness of separation and higher water recoveries to the oversize. An increase in aperture size increased the sharpness of separation and decreased the water recoveries to the oversize. The solids concentration appeared to have a higher effect on cut size than the feed flow rate. The highest cut size and sharpness of separation and lowest water recovery to oversize were attained at the lowest feed rate. The lowest solids concentration produced the best performance with regards to all partition curve properties. The cut size approached the aperture size at the lowest throughput and solids concentration for all aperture sizes. All the efficiency curves exhibited fish hooks at fine particle sizes with the fish hooks becoming more pronounced at higher feed flow rates and solids concentration and smaller aperture sizes. A wet fine screen model that includes multi component ores as well as changes in operating conditions was developed using the 2 - parameter Whiten screen model as a basis. The dimensional analysis approach was applied in developing the sub - models that relate the operating and design parameters to the Whiten model parameters. The dimensional analysis approach was further applied to develop the model that describes the fish hook effect for subsequent incorporation into the overall modified fine screen model. Generally, the modified model is capable of predicting the performance of the wet fine screen reasonably well with minor errors and accommodates for the data that exhibits the fish hook. The model also reduces the fitting process required in the original Whiten model.
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Little, Lucy. "The development and demonstration of a practical methodology for fine particle shape characterisation in minerals processing." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22741.
Texte intégralRésumé :
Due to continually declining ore grades, increasing mineralogical complexity, and increasing metal demand, models for the design and optimisation of minerals processing operations are of critical importance. These models do not currently incorporate particle shape, which, although rarely quantified, is known to affect numerous unit operations. Automated Scanning Electron Microscopy (Auto-SEM-EDS) is a widely used tool for mineralogical analysis. It also provides an opportunity for simple, quantitative and mineral-specific shape characterisation. Existing mineralogical databases could therefore become useful resources to facilitate the incorporation of shape effects in minerals processing models. A robust Auto-SEM-EDS shape characterisation methodology is required to ensure that the particle shape information in these databases is interpreted appropriately. For this work, a novel methodology for Auto-SEM-EDS shape characterisation was developed that is suitable for the analysis of fine particles (<75 μm). This involved testing the response of various shape descriptors to image resolution, and measurement with different devices and image processing routines. The most widely used shape descriptor in minerals processing, circularity, was found to be highly dependent on both image resolution and image processing settings, making it a poor choice for shape characterisation of fine particles. Roundness and aspect ratio were found to be more robust descriptors. However, in the interest of being able to compare particulate shape measurements across different studies, the precise definition of aspect ratio is important as variation in 'length' and 'width' definitions can significantly impact aspect ratio measurements. The possibility that preferential orientation of particles would introduce bias to the 2-D cross-sectional measurements was also addressed through comparison of roundness distributions measured from orthogonal cross-sections of a particulate sample mounted within a block of resin. The excellent repeatability of these measurements indicated that the particles were randomly orientated, and thus it can be inferred that 2-D measurements of a sufficient number of particles will be directly related to the particulate sample's 3-D properties. Roundness and aspect ratio were then used in conjunction to produce surface frequency distributions that allow for distinction between non-rounded particles that were smooth and elongated and non-rounded particles that were neither elongated nor smooth. Three applications of the shape characterisation methodology developed were then demonstrated, which highlighted some of the potential contributions that this methodology can make towards minerals processing. The applications were all based on a case study of the Upper Group 2 (UG2) Chromitite, a platinum group mineral (PGM) ore of key economic significance to South Africa.
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Muketekelwa, Saliya L. "Investigating the potential of using hydrocyclone-fine screen hybrid systems to improve the performance of classification circuits." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/27538.
Texte intégralRésumé :
Classification is an integral part of comminution operations that controls the performance of the circuit. Hydrocyclones are normally used to perform the classification function. They offer numerous advantages that include, the ability to handle high throughputs, low floor space occupation and relatively low capital and running costs. Despite these advantages, hydrocyclones are inherently inefficient classifiers as they are predominantly dependent on hydrodynamics to effect separation. This effect is more prominent in operations handling complex ores such as a dual-density ore, where the heavy fine particles are misplaced to the underflow and the lighter middling particles report to the overflow. Several attempts have been made to improve the separation efficiency of cyclones either by modification of the cyclone or use of multi-stage cycloning. Most of the results obtained from experimental and simulation studies have shown considerable improvements. Even though some have not yet found wide application in the minerals industry due to practical limitations related to control and unstable operations. More recently, fine screening has gained recognition in the classification role. This development has allowed the use of fine screens in closed-circuit grinding operations resulting in significant metallurgical and economic benefits. Screens provide a sharper cut at the desired size and reduce the fraction of fines bypassing classification compared to hydrocyclones but have capacity limitations at smaller apertures. In an effort to mitigate the classification challenges of both the hydrocyclone and fine screen, this study investigated the potential of combining the high throughput performance of the hydrocyclone operation and the high precision classification characteristics of fine screening to result in a hybrid classification circuit Plant scale tests were conducted using five different classification circuit configurations at an operational Base Metal Concentrator treating a polymetallic ore. The classification circuit configurations considered included (i) a two-stage hydrocyclone with primary underflow reclassification (ii) an inclined hydrocyclone, (iii) a fine screen and (iv) selected permutations of hybrid circuit designs that included a hydrocyclone-fine screen (2 stage) and two hydrocyclones-fine screen (3 stage) variants of the hybridised configurations. The efficiency curves and their respective key performance indicators were used to assess the performance of the circuit configurations tested. The results showed that classification circuits that included fine screens exhibited higher sharpness of separation compared to circuit configurations comprised of hydrocyclones. The fine screen configuration showed the sharpest separation while the hydrocyclone-fine screen hybrid configurations gave relatively higher separation efficiencies than the configurations with hydrocyclones only. The overall sharpness of separation values obtained for the two stage and three-stage hybrid circuits were 3.0 and 2.4, respectively. The two-stage hydrocyclone and inclined hydrocyclone circuits had sharpness of separation values of 1.7 and 0.5, respectively. The inclined hydrocyclone circuit configuration performed the poorest. Furthermore, the two-stage hybrid circuit showed a higher degree of separation compared to the three-stage hybrid configuration. However, it was observed that a finer corrected cut size was realised for the three-stage hybrid circuit design. The fishhook effect was seen at particle sizes less than 38μm for the configurations incorporating a fine screen and an inclined hydrocyclone. Notably, the effect appeared to be more pronounced in configurations involving a fine screen stage. The results have shown that application of hybrid classification configurations can improve the performance of classification circuits. In addition, reclassification of hydrocyclone underflow on fine screens will results in a sharper classification while reclassifying the overflow stream on fine screens will provide a clean circuit final product. An evaluation of the capital and operating costs associated with fine screens should be done to determine the economic feasibility of incorporating the units in conventional milling circuits.
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Groen, Heidi. "On-line monitoring and control of supersaturation in batch crystallisers for organic fine chemical products using ATR FTIR spectroscopy." Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/1180.
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Aristizabal, Felipe. "Modelling of the generation of ultra fine aluminum particles from the quench of superheated vapour in turbulent flow by Felipe Aristizabal." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33954.
Texte intégralRésumé :
This work reports on a Low Reynolds Number (LRN) turbulent model to simulate such systems for the production of pure metal powders. Aluminium has been chosen as an example.<br>The fluid flow in the turbulent regime was simulated using the LRN model by Jones and Launder (1973); while the dynamic behaviour of the particulate system was modeled in terms of the leading moments of the particle size distribution. The shape of the aerosol size distribution was approximated by a unimodal lognormal function.<br>The set of governing equations were solved numerically using the Finite Volume formulation, while the SIMPLER algorithm (Patankar 1980) was used to solve the momentum equations coupled with the continuity equation. The effect of different process parameters on the characteristics of the product was investigated. The model presented can be used to assist the understanding and scale up of such ultra fine particle generators. (Abstract shortened by UMI.)
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Swaraj, Sufal. "Surface chemical characterization of plasma-chemically deposited polymer films by X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure." [S.l.] : [s.n.], 2005. http://www.diss.fu-berlin.de/2005/273/index.html.
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Halan, Babu [Verfasser]. "Biofilms as living catalysts for fine chemical synthesis: analysis, process design and scale-up / Babu Halan." Aachen : Shaker, 2013. http://d-nb.info/1051574633/34.
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Koopmeiners, Julia Verfasser], and Anett [Akademischer Betreuer] [Schallmey. "Characterization of novel halohydrin dehalogenases for application in fine chemical synthesis / Julia Koopmeiners ; Betreuer: Anett Schallmey." Braunschweig : Technische Universität Braunschweig, 2017. http://d-nb.info/1175816906/34.
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Gill, Christopher Stephen. "Novel hybrid organic/inorganic single-sited catalysts and supports for fine chemical and pharmaceutical intermediate synthesis." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28218.
Texte intégralRésumé :
Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Jones, Christopher; Committee Member: Agrawal, Pradeep; Committee Member: Teja, Amyn; Committee Member: Weck, Marcus; Committee Member: Zhang, John.
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Gander, Nathan. "Assessing Particulate and Chemical Emissions from Additive Manufacturing Processes." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1595848332301779.
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Pederzoli, Anna. "The application of an Eulerian chemical and transport model (CMAQ) at fine scale resolution to the UK." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/3127.
Texte intégralRésumé :
Present-day numerical air quality models are considered essential tools for predicting future air pollutant concentrations and depositions, contributing to the development of new effective strategies for the control and the reduction of pollutant emissions. They simulate concentrations and depositions of pollutants on a wide range of scales (global, national, urban scale) and they are used for identifying critical areas, integrating measurements and achieving a deeper scientific understanding of the physical and chemical processes involving air pollutants in the atmosphere. The use of comprehensive air quality models started in the late 1970s and since then their development has increased rapidly, hand in hand with the rapid increase in computational resources. Today more and more complex and computationally expensive numerical models are available to the scientific community. One of these tools is the Community Multi-Scale Air Quality System (CMAQ), developed in the 1990s by the US Environmental Protection Agency (EPA) and currently widely applied across the world for air pollution studies. This work focuses on the application of CMAQ to the United Kingdom, for estimating concentrations and depositions of acidifying pollutants (NOX, NHX, SOX) on a national scale. The work is divided into seven chapters, the first one describing the main issues related to the emission and dispersion in the atmosphere of acidifying species. It also includes a brief overview of the main international policies signed in the last thirty years in order to reduce the problem of acidification in Europe, as well as a brief description of some models mentioned in this thesis. The second one describes the main features of CMAQ and addresses some issues such as the use of a nesting process for achieving temporally and spatially resolved boundary concentrations, and the implementation of the model on parallel machines, essential for reducing the simulation computing time. It also describes how this study is part of a wider context, which includes the application of CMAQ in the United Kingdom by other users with different scientific purposes (aerosols processes, air quality in the urban area of London, contribution of UK power stations to concentrations and depositions etc.). The third part of the thesis focuses on the application and evaluation over the United Kingdom of the 5th Generation Mesoscale Model MM5, used for providing 3D meteorological input fields to CMAQ. This study was performed assuming that an accurate representation of depositions and concentrations of chemical species cannot be achieved without a good estimate of the meteorological parameters involved in most of the atmospheric processes (transport, photochemistry, aerosol processes, cloud processes etc.). The fourth part of the thesis describes the preliminary implementation of the Sparse Matrix Operational Kernel Emission System (SMOKE) in the United Kingdom. The processor provides input emissions to CMAQ. The use of SMOKE is usually avoided in CMAQ applications of outside America, and CMAQ input emission files are prepared by the application of other software. The reason is that the model requires radical changes for being applied outside Northern and Central America. Some of these changes have been made in this study such as the adaptation of the European emission inventory EMEP and the UK National Inventory NAEI to the modelling system for point and area sources, the introduction of new European emission temporal profiles in substitution of the American ones and the introduction of new geographical references for the spatial allocation of emissions. In the fifth chapter the results of CMAQ application over the UK are discussed. The study focuses on NOX, SO2, NH3 and + 4 NH . Maps of concentration are presented and modelled data are compared to measurements from two different air quality networks in the UK. An analysis of the performance of CMAQ over the UK is also performed. In the final chapter an annual inter-comparison between CMAQ and the Lagrangian transport model FRAME is carried out. Maps of annual wet deposition fluxes of NHX, NOY and SOX for year 1999 are presented. The results of both models are compared to one another and they are also compared to values from the UK official data set CBED. Finally, the last chapter suggests the work that has to be done in the future with CMAQ and it summarizes the conclusions.
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Grover, Brett D. "Measurement, characterization, and source apportionment of the major chemical components of fine particulate material, including semi-volatile species /." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1174.pdf.
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Marchand, Jérémy. "Combining NMR and MS fingerprinting for fine characterization of lipid profiles. : Application to a chemical food safety issue." Thesis, Nantes, Ecole nationale vétérinaire, 2018. http://www.theses.fr/2018ONIR120F/document.
Texte intégralRésumé :
Pour garantir au consommateur des aliments sûrs, l'emploi d'anabolisants chez les animaux de production est prohibée au sein de l'Union Européenne depuis la fin des années 1980. Bien que performantes, les méthodes de contrôle classiques ciblées font face à de nouveaux défis auxquels des stratégies alternatives (non ciblées),visant à identifier des biomarqueurs métaboliques caractéristiques de l'effet associé à ces pratiques, offrent des solutions innovantes. Le lipidome en particulier constitue une fraction d'intérêt pour l'étude des effets liés aux agents de répartition. La Spectrométrie de Masse (SdM) et la Résonance Magnétique Nucléaire (RMN) sont alors classiquement utilisées, indépendamment. Ce travail propose d'évaluer leur combinaison, bénéficiant des niveaux d'information différents associés, et les conséquences en termes de gain de prédiction ou d'identification des biomarqueurs. Comme modèle d'étude, des échantillons sanguins provenant d'animaux traités avec un agent de répartition connu pour perturber les profils lipidiques,ont été caractérisés. L'analyse du lipidome sérique par SdM a impliqué trois plateformes offrant des angles de vue différents afin de fournir une couverture étendue; l'étude de leur cohérence et complémentarité constituant l'un des objectifs de cette thèse. En parallèle, l'analyse par RMN a requis le développement d'une procédure complète, de l'optimisation des conditions de préparation d'échantillon aux paramètres d'acquisition, incluant des approches de RMN 2D rapides récentes. Enfin, le verrou associé à l'analyse des données issues des différentes sources a permis d'évaluer des approches statistiques innovantes, notamment multibloc<br>Ln order to ensure safe food products for the consumer, the use of growth promoters in livestock farming has been prohibited in European Union since the end of the 80s. Although efficient, the conventional targeted control methods face new challenges to which alternative strategies (untargeted), aiming at identifying metabolic biomarkers characteristic of the effects induced by such practices, provide innovative solutions. In particular, the lipidome is an area of interest to investigate the effects associated with repartition agents. Mass Spectrometry (MS) and Nuclear Magnetic Resonance (NMR) are then classically used independently. This PhD work intends to evaluate their combination benefiting from the different levels of associated information and the consequences in terms of enhanced prediction or biomarker identification. As a study model, blood samples from animals treated with a repartition agent known to disrupt lipid profiles were characterized. The investigation of the serum lipidome with MS involved three distinct platforms providing different outlooks in order ta generate extended coverage; the study of their consistency and complementarity constituting one of the objectives of this PhD. In parallel, the analysis with NMR prompted the development of a complete workflow, from the optimization of the sample preparation conditions to acquisition parameters -including recent fast 2D NMR approaches. Finally, the challenge associated with the analysis of data from multiple sources allowed ta evaluate innovative statistical approaches such as multiblock analysis
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Grover, Brett D. "Measurement, Characterization, and Source Apportionment of the Major Chemical Components of Fine Particulate Material, Including Semi-Volatile Species." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/359.
Texte intégralRésumé :
The promulgation of revised standards for atmospheric fine particles (PM2.5) by the US EPA has sparked renewed interest in the ability to accurately measure and characterize suspended atmospheric particulate matter. Semi-volatile material (SVM), consisting of ammonium nitrate and semi-volatile organic material (SVOM), is not accurately measured by EPA accepted methods such as the Federal reference method (FRM) or Tapered Element Oscillating Microbalance (TEOM). However, SVM is often a major fraction of urban aerosols. Recent advances in atmospheric sampling instrumentation allowed for the semi-continuous characterization of urban PM2.5, including SVM. The Filter Dynamic Measurement System (FDMS) was shown to measure total PM2.5 mass including semi-volatile species. Validation of the FDMS was performed by comparison with the particle concentrator-Brigham Young University organic sampling system (PC-BOSS) and the real-time total ambient mass sampler (RAMS). Semi-continuous ambient particulate concentrations of sulfate, nitrate and ammonium ion were measured by a newly developed Dionex instrument which was field tested and validated for the first time in Fresno, CA. Either a modified Sunset Laboratory carbon monitor, collocated with a conventional Sunset carbon monitor employing a common inlet, or the newly developed dual-oven Sunset monitor allowed for the semi-continuous determination of both nonvolatile and semi-volatile organic material. This was the first attempt to characterize both nonvolatile and semi-volatile fractions of an urban aerosol in a semi-continuous manner using all semi-continuous instruments. A suite of instruments for semi-continuous PM2.5 monitoring was recommended including, an R&P FDMS for the measurement of PM2.5 mass, a dual-oven Sunset monitor for the measurement of nonvolatile and semi-volatile carbonaceous species, and a Dionex GP-IC for the measurement of inorganic species. A TEOM monitor is also recommended to measure nonvolatile PM2.5 mass. Using these instruments, semi-continuous mass closure was obtained for the first time during a study conducted in Riverside, CA. The advantage of using semi-continuous sampler data in the application of source apportionment was elucidated. Local aerosols are often impacted by short-term pollution episodes that cannot be temporally resolved using integrated samplers. One-h averaged data applied to source apportionment models was shown to increase the power of the model to predict sources, both primary and secondary, that exhibit diurnal short-term episodes.
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Yang, Yang. "A study of fine particle grinding in vertically stirred media mills via positron emission particle tracking technology and the discrete element method." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8162/.
Texte intégralRésumé :
This study provides a comprehensive understanding of the fine particle grinding process in stirred media mills. Calcium carbonate was chosen as the feed material. The experiments were firstly conducted in a laboratory scale vertically stirred media mill under various grinding conditions. The operating variables including specific energy, rotational speed, solids concentration, grinding media type, chemical additives (dispersant) were investigated. Then, the process was scaled up to a pilot scale mill. The performance of the pilot scale mill was compared to the laboratory scale mill regarding the product size (e.g. d80 ) and instantaneous power draw. Positron Emission Particle Tracking technology (PEPT) was used as a tool to study the motion of the grinding media in the laboratory scale stirred media mill. Some new stirrers were proposed and analysed. The PEPT results obtained under different operating conditions were demonstrated and analysed. The Discrete Element Method (DEM) based on the Hertz-Mindlin contact model was implemented to simulate the motion of the grinding media in both laboratory scale and pilot scale mills. A new type of stirrer is accepted by Imerys and used to produce the calcium carbonate in the industrial scale of grinding process. The energy saving is obtained up to 3 %compared to the standard stirrer currently used.
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Hesham, Ahmed H. [Verfasser]. "Treatment and improvement of the geotechnical properties of different soft fine-grained soils using chemical stabilization / Ahmed H Hesham." Aachen : Shaker, 2006. http://d-nb.info/1166513483/34.
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Li, Ying. "Assessing Public Health Burden Associated with Exposure to Fine Particulate Matter and Its Chemical Components in the United States." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/21.
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Xie, Ying. "Testing ozone sensitivities using process analysis, chemical indicators, and very fine scale modeling with CMAQ in the Pacific Northwest." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Dissertations/Fall2008/y_xie_120508.pdf.
Texte intégralRésumé :
Thesis (Ph. D.)--Washington State University, December 2008.<br>Title from PDF title page (viewed on June 30, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references.