Thèses sur le sujet « Roller milling »

Wheat is the most popularly grown cereal in the world. Over 400 million tonnes of wheat is milled to flour annually for inclusion in baked products. Flour milling has evolved into an efficient operation; however, process modelling, simulation and optimisation can make significant improvements to the operation. One such improvement is the use of more informative quality testing procedures to supply information about milling potential of a sample. Breakage matrices were used to describe the breakage function that relates the inlet and outlet particle size distributions over 151 Break. Successful prediction of the milled stock particle size distribution for the native (unsegregated) wheat sample showed that wheat grains milled independently during roller milling; this was confirmed using high-speed video. The milling ratio (roll gap over grain thickness) was identified as the parameter determining breakage and enabled a range of roll gaps and inlet particle sizes to be considered simultaneously. The variation in cumulative undersize, P(x), with milling ratio was described by a quadratic function whose coefficients varied in a quadratic manner with particle size (x). Nine breakage coefficients were used to describe the breakage of a wheat variety over a range of roll gaps and inlet particle thickness. The particle size distribution was predicted using the breakage equation and shown to be linear in the range 250-2000 Ilm for 21 different wheats. The slope of the particle size distribution was related to wheat hardness and varied with milling ratio. This variation was shown to indicate the sensitivity of the variety to changes in the milling ratio. Flour millers generally prefer varieties with a high sensitivity to changes in milling ratio. Rank Hovis, sponsors of this project, mill approximately 1.6 million tonnes of wheat per year. The results of this study provide the foundation for savings in milling efficiency (through increased flour extraction), wheat substitution (using lower priced wheat in place of high priced wheat). It is estimated that these measures could save over £1m per annum.

Blending nutrient-rich pulses into cereal-based convenience foods could benefit consumers and the cereal and pulse industries but first requires appropriate milling of raw pulses, for which there is no standardized method. Roller milling is the standard method for wheat flour production, but hammer milling is simpler and more cost-effective. Literature documenting pulse flour quality from either system is limited. The goals of this research were to evaluate (1) the effects of hammer mill setup and seed moisture on quality and flowability and (2) the differences between hammer- and roller-milled quality for yellow split pea. For (1), yellow split pea samples at 9 and 11 % moisture were hammer-milled at two rotor speeds (34 and 102 m/s) and with nine mill screen apertures (0.84 to 9.53 mm) and physicochemical properties and flow properties on 6 surfaces were evaluated. For (2), yellow split pea at 11 % moisture was hammer-milled at 102 m/s through a 0.84 mm screen or roller-milled using a two-pass setup, then sieved through a 150 ?m screen and evaluated for physicochemical and functional quality. Hammer mill settings had no practical impact on proximate composition, small impact on damaged starch content, and considerable impact on particle size distribution, pasting properties, and flowability. Particle size parameters impacted color, bulk density, pasting properties, and flowability. Flowability was highest on aluminum and lowest on high-density polyethylene. Hammer milling at 102 m/s rotor speed with 0.84 mm screen aperture produced particle sizes closest to that of flour (D10, D50, and D90 of 12, 98, and 348 ?m, respectively). Small differences were observed in the D10, starch damage, moisture, peak and final viscosities, and oil binding capacities of hammer- and roller-milled split pea flours. Data from this research supported the viability of hammer milling to produce split pea flour and provided systematic data to support milling, product development, conveying, and storage operations involving split pea and other pulses.
Northern Pulse Growers Association
U.S. Dry Pea and Lentil Council

The particle size distribution produced from first break roller milling of wheat determines the flows through the rest of the mill and hence the quality of the final flour, and is affected by debranning and by the operation of the roller mill. The Double Normalised Kumaraswamy Breakage function (DNKBF) gives a quantitative basis to describe breakage during first break milling of wheat and to interpret effects. Previous work developed and extended the breakage equation in order to understand and predict wheat breakage based on distributions of the grain characteristics and the operating parameters of the mill. However, broken particles vary in composition as well as size; therefore the primary objective of the current work was to extend the DNKBF during first break milling to include particle composition, using fingerprints of pericarp, aleurone, endosperm and germ. Meanwhile, debranning is a technology that has enhanced flour milling in recent years, leading to improvements in quality that are not well understood but that start with the effect on milling. A second objective of the current work was therefore to apply the DNKBF to describe and interpret the effects of debranning on wheat breakage and, in so doing, to clarify the physical significance of the DNKBF parameters. Samples of Mallacca (hard wheat) and Consort (soft wheat) were debranned for nine different times, at three roll gaps and under S-S and D-D dispositions. The DNKBF successfully described the normalised particle size distribution at different debranning times. The DNKBF describes wheat breakage in terms of Type 1 and Type 2 breakage, where Type 1 describes a relatively narrow distribution of mid-sized particles, whilst Type 2 describes a wide size range of predominantly small particles extending to very large particles. The proportion of Type 1 breakage increased at longer debranning times, while Type 2 breakage decreased, for both wheats under both dispositions. S-S milling tended to produce more Type 1 breakage than D-D. A mechanism of wheat breakage is proposed to explain the co-production of very large and small particles via Type 2 breakage, and hence the effect of debranning. The proposed mechanism is that small particles of endosperm arise from scraping of large flat particles of wheat bran under the differential action of the rolls; removal of the bran reduces the production of the large bran particles and thus reduces the opportunity for the scraping mechanism that produces the very small particles. The composition of broken particles can be characterised considering the four major wheat components, pericarp, aleurone, endosperm and germ. Kernels of Mallacca and Consort wheats were manually dissected to isolate these components. FTIR spectroscopy was able to distinguish the different components in milled fractions. However, attempts to quantify the relative contribution of each wheat component in milled fractions (by measuring specific peak heights and by Partial Least Squares, PLS) were compromised by technical limitations. An alternative approach aimed to fingerprint the components using sugar analysis by HPLC, with some success; however the technique was too complex and limited by the detection limit of HPLC, in particular for arabinose and xylose. Instead, the botanical distributions within eight milled fractions of Mallacca and Consort wheats milled under S-S and D-D dispositions were analyzed by PLS models developed by Barron (2011). The concentration functions were then found by applying the DNKBF to the particle size distributions and to the compositional distributions, the ratio of the DNKBFs giving the concentration function. The DNKBF was able to describe the data well for the four botanical components studied in both wheats: pericarp, aleurone, intermediate layer and starchy endosperm. The analysis clarified the nature of the particles produced on breakage, showing that for Mallacca wheat, the pericarp and aleurone layer compositions mostly varied with particle size in similar ways. Intermediate layer showed broadly similar results to those for pericarp and aleurone in the Mallacca wheat despite being the least accurate component predicted. However, for Consort wheat, the intermediate layer behaved differently from pericarp and aleurone, suggesting a different breakage mechanism, perhaps associated with how the wheat hardness affects breakage of the bran and the production of large flat bran particles. Creation of pericarp/intermediate layer/aleurone dust during milling was notable, in particular for Mallacca wheat. The relative uniformity of the Mallacca compositions in relation to pericarp, intermediate layer and aleurone, which varied in consistent ways with particle size, was also notable. By contrast, for Consort wheat, the relative proportions of these three components appear to vary substantially in particles of different size, pointing to very different breakage origins. It seems that in the hard wheat, the breakage patterns are dominated by the endosperm physical properties, while for the soft wheat, the behaviour of the large bran particles produced is dictated much more by the properties and structure of the bran layers than by the hardness of the endosperm. The approach presented is practical to describe, quantify and interpret the effects of breakage on component distributions, in order to understand the fate of kernel components during milling and hence the origins of flour quality.

This diploma thesis includes research in the structural parts of milling machines and designs of a console adjustable. This diploma thesis includes necessary calculations, adjustable worktable assembly drawing, selected drawing documentation, 3D model and model in an immersive virtual reality.

U radu je proučavana mogućnost racionalizacije tehnološkog postupkamlevenja pšenice primenom osmovaljne stolice u fazi mlevenja griza iosevaka. Na svim ispitivanim prolazištima mlevenja griza i osevaka, pri istomrazmaku između valjaka i istoj veličini otvora sejnog tkiva za odsejavanjebrašna, ukupan prinos brašna u postupku sa osmovaljnom stolicom manji jenego u klasičnom postupku. Pomenuta razlika varira u zavisnosti od uzorka iprolazišta mlevenja, ali je uvek statistički značajna. Nižim vođenjem valjaka upostupku sa osmovaljnom stolicom, u poređenju sa razmacima između valjakau klasičnom postupku, u zavisnosti od uzorka i prolazišta mlevenja sesmanjuje razlika, dostiže ili prevazilazi prinos brašna u odnosu na klasičnipostupak. Povećanjem veličine otvora sejnog tkiva za odsejavanje brašnaznačajno se povećava prinos brašna u postupku sa osmovaljnom stolicom, pričemu se pri odabiru sejnog tkiva u obzir mora uzeti i veličina svetlog otvora.Odabirom odgovarajuće veličine otvora sejnog tkiva može se i prevazićiprinos brašna u klasičnom postupku. Niže vođenje valjaka i/ili povećanjeveličine otvora sejnog tkiva za odsejavanje brašna, pri primeni osmovaljnestolice, nema za posledicu pogoršanje kvaliteta brašna (po pitanju sadržajapepela) u odnosu na klasični postupak. Specifični utrošak energije zausitnjavanje po jedinici mase brašna, pri istom vođenju valjaka i istoj veličiniotvora sejnog tkiva za odsejavanje brašna, veći je u postupku sa osmovaljnomstolicom nego u klasičnom postupku. Povećanjem izvoda brašna u postupku saosmovaljnom stolicom, značajno se smanjuje specifični utrošak energije zausitnjavanje. Mogućnost ostvarenja bliskih efekata usitnjavanja u fazimlevenja griza i osevaka, u klasičnom i postupku sa osmovaljnom stolicom,ukazuje da je za dalju racionalizaciju savremenog tehnološkog postupkamlevenja pšenice neophodno uključivanje osmovaljne stolice.
Rationalization of the wheat flour milling process using the eight-roller mill inthe reduction system has been investigated. At the same roll gaps and samesieving conditions, a lower flour yield has been obtained using an eight-rollermill compared to a conventional one. The difference is statistically significantregardless the passage. By decreasing the roll gap in the process with theeight-roller mill, compared to the roll gap in the conventional process, it ispossible to decrease the difference, obtain a similar or even exceed the flourrelease in the conventional system. Increasing the size of the screen aperturefor sifting flour, while percent open area of the screen also needs to beobserved, results in significant increase of flour yield (in some casesexceeding the flour yield in the conventional system). Adjustments of the rollgap and sieving conditions in the process with the eight-roller mill are notfollowed by deterioration of flour quality. At the same roll gaps and samesieving conditions, energy requirements for grinding are higher in the processwith the eight-roller mill compared to a conventional system. With theincrease of the flour release in process using the eight-roller mill, these energyrequirements can be significantly reduced. The possibility of achieving similarmilling results to those obtained in the conventional system, while theinvestment costs and overall energy requirements are significantly lower,justifies the use of the eight-roller mill in the reduction system of the wheatflour milling process.

This work deal with different variants of the turning milling heads for CNC machines.The report depicts actual design solution of the turning milling head formilling machine, including technical report and economical conclusions.

This diploma project is in 2 parts. The first part is a program for a so called segregated area where the focus is on acting now, and trying to combine working with social mobilization with an architect's role. The second part is my design proposal, which is a part of this program. Anticipating 2020 is a program for projects spanning over 6 years in Hovsjö, Södertälje that I curate. 5 architects are invited to do one project each. The task is to build a structure or an event, temporary or not, that can inform, spark fantasy, discuss and in other ways be a part of a planning process as well as instant- and future change in Hovsjö. Its purpose is to discuss the existing and possible urban life in relation to planning and upgrading sptially segregated areas in general and the city area Hovsjö in particular. Once a year one architect will do one project or event. I will do the first project in the program, Installation 2014. The program focuses on the role of the architect and architecture in spatially segregated areas, the public spaces that were the outcome and consequence of the functionalist/modernist urban planning, the notion of temporality and events in relation to architecture and vague spaces and creative loopholes.  For whom, by whom and with whom are cities planned? The intention with my design proposal, the Installation 2014, is to create a diversity of public room types and scales in Hovsjö. To be able to keep a big open space open but at the same time being able to have smaller rooms within the big area. To work with a geometrical element - the spehere - trying to describe outdoor public rooms rahter then enclosing them by building walls.
Detta examensarbete är i två delar. Den första delen är ett program för ett så kallat segregerat område där fokus ligger på att agera nu, samt att försöka kombinera, reflektera och diskutera arkitektens roll i arbete med social mobilisering.  Den andra delen är ett designförslag, vilket är en del av nämnda program. I väntan på 2020 är ett program jag kurerar där projekt spänner över 6 år i Hovsjö, Södertälje. 5 arkitekter bjuds in för att göra ett projekt var. Uppgiften är att bygga en struktur eller ett event, temporärt eller ej, som kan informera, väcka fantasi, diskutera och på andra sätt vara en del av en pågående planeringsprocess likväl som del av en direkt förändring av Hovsjö. Programmets syfte är att diskutera det existerande och möjliga urbana livet i relation till planering och så kallad uppgradering av rumsligt segregerade områden generellt, och Hovsjö specifikt. En gång varje år kommer en arkitekt genomföra ett projekt eller ett event. Jag gör första projektet i programmet, Installation 2014. Programmet fokuserar på arkitektens- och arkitekturens roll vid arbete med rumsligt segregerade områden, de publika platserna som var resultatet av, och en konsekvens av, den funktionalistiska/modernistiska stadsplaneringen, begreppet temporalitet och event i relation till arkitektur, vaga platser samt kreativa kryphål. För vem, av vem och med vem planeras städer? Ambition med mitt designförslag, Installation 2014, är att skapa en diversitet av typer av publika rum och skalor på dessa. Att behålla en stor öppen yta öppen men samtidigt möjliggöra för mindre rum inom detta område. Att arbeta med ett geometriskt element - sfären - och försöka beskriva exteriöra publika rum snarare än att bygga in dem.

This diploma thesis designs a small vertical CNC milling machine. The thesis includes selection of suitable structural design of the machine based on market analysis and requirements. The listed components, constructional calculations and 3D model are chosen in order to minimize the costs.

O Vírus da Imunodeficiência Humana (HIV) é o agente etiológico da Síndrome da Imunodeficiência Adquirida (AIDS). A AIDS é uma doença de distribuição mundial, e estima-se que existam atualmente pelo menos 36,9 milhões de pessoas infectadas com o vírus. Durante o seu ciclo replicativo, o HIV promove diversas alterações na fisiologia da célula hospedeira a fim de promover sua sobrevivência e potencializar a replicação. A rápida progressão da infecção pelo HIV-1 em humanos e em modelos animais está intimamente ligada à função da proteína acessória Nef. Dentre as diversas ações de Nef está a regulação negativa de proteínas importantes na resposta imunológica, como o receptor CD4. Sabe-se que esta ação resulta da indução da degradação de CD4 em lisossomos, mas os mecanismos moleculares envolvidos ainda são totalmente elucidados. Nef forma um complexo tripartite com a cauda citosólica de CD4 e a proteína adaptadora 2 (AP-2), em vesículas revestidas por clatrina nascentes, induzindo a internalização e degradação lisossomal de CD4. Pesquisas anteriores demonstraram que o direcionamento de CD4 aos lisossomos por Nef envolve a entrada do receptor na via dos corpos multivesiculares (MVBs), por um mecanismo atípico, pois, embora não necessite da ubiquitinação de carga, depende da ação de proteínas que compõem os ESCRTs (Endosomal Sorting Complexes Required for Transport) e da ação de Alix, uma proteína acessória da maquinaria ESCRT. Já foi reportado que Nef interage com subunidades dos complexos AP-1, AP-2, AP-3 e Nef não parece interagir com subunidades de AP-4 e AP-5. Entretanto, o papel da interação de Nef com AP-1 e AP-3 na regulação negativa de CD4 ainda não está totalmente elucidado. Ademais, AP-1, AP-2 e AP-3 são potencialmente heterogêneos devido à existência de isoformas múltiplas das subunidades codificadas por diferentes genes. Todavia, existem poucos estudos para demonstrar se as diferentes combinações de isoformas dos APs são formadas e se possuem propriedades funcionais distintas. O presente trabalho procurou identificar e caracterizar fatores celulares envolvidos na regulação do tráfego intracelular de proteínas no processo de regulação negativa de CD4 induzido por Nef. Mais especificamente, este estudo buscou caracterizar a participação do complexo AP-1 na modulação negativa de CD4 por Nef de HIV-1, através do estudo funcional das duas isoformas de ?-adaptina, subunidades de AP-1. Utilizando a técnica de Pull-down demonstramos que Nef é capaz de interagir com ?2. Além disso, nossos dados de Imunoblot indicaram que a proteína ?2-adaptina, e não ?1-adaptina, é necessária no processo de degradação lisossomal de CD4 por Nef e que esta participação é conservada para degradação de CD4 por Nef de diferentes cepas virais. Ademais, por citometria de fluxo, o silenciamento de ?2, e não de ?1, compromete a diminuição dos níveis de CD4 por Nef da membrana plasmática. A análise por imunofluorêsncia indireta também revelou que a diminuição dos níveis de ?2 impede a redistribuição de CD4 por Nef para regiões perinucleares, acarretando no acúmulo de CD4, retirados por Nef da membrana plasmática, em endossomos primários. A depleção de ?1A, outra subunidade de AP-1, acarretou na diminuição dos níveis celulares de ?2 e ?1, bem como, no comprometimento da eficiente degradação de CD4 por Nef. Além disso, foi possível observar que, ao perturbar a maquinaria ESCRT via super-expressão de HRS (uma subunidade do complexo ESCRT-0), ocorreu um acumulo de ?2 em endossomos dilatados contendo HRS-GFP, nos quais também detectou-se CD4 que foi internalizado por Nef. Em conjunto, os resultados indicam que ?2-adaptina é uma importante molécula para o direcionamento de CD4 por Nef para a via ESCRT/MVB, mostrando ser uma proteína relevante no sistema endo-lisossomal. Ademais, os resultados indicaram que as isoformas ?-adaptinas não só possuem funções distintas, mas também parecem compor complexos AP-1 com diferentes funções celulares, já que apenas a variante AP-1 contendo ?2, mas não ?1, participa da regulação negativa de CD4 por Nef. Estes estudos contribuem para o melhor entendimento dos mecanismos moleculares envolvidos na atividade de Nef, que poderão também ajudar na melhor compreensão da patogênese do HIV e da síndrome relacionada. Em adição, este trabalho contribui para o entendimento de processos fundamentais da regulação do tráfego de proteínas transmembrana no sistema endo-lisossomal.
The Human Immunodeficiency Virus (HIV) is the etiologic agent of Acquired Immunodeficiency Syndrome (AIDS). AIDS is a disease which has a global distribution, and it is estimated that there are currently at least 36.9 million people infected with the virus. During the replication cycle, HIV promotes several changes in the physiology of the host cell to promote their survival and enhance replication. The fast progression of HIV-1 in humans and animal models is closely linked to the function of an accessory protein Nef. Among several actions of Nef, one is the most important is the down-regulation of proteins from the immune response, such as the CD4 receptor. It is known that this action causes CD4 degradation in lysosome, but the molecular mechanisms are still incompletely understood. Nef forms a tripartite complex with the cytosolic tail of the CD4 and adapter protein 2 (AP-2) in clathrin-coated vesicles, inducing CD4 internalization and lysosome degradation. Previous research has demonstrated that CD4 target to lysosomes by Nef involves targeting of this receptor to multivesicular bodies (MVBs) pathway by an atypical mechanism because, although not need charging ubiquitination, depends on the proteins from ESCRTs (Endosomal Sorting Complexes Required for Transport) machinery and the action of Alix, an accessory protein ESCRT machinery. It has been reported that Nef interacts with subunits of AP- 1, AP-2, AP-3 complexes and Nef does not appear to interact with AP-4 and AP-5 subunits. However, the role of Nef interaction with AP-1 or AP-3 in CD4 down-regulation is poorly understood. Furthermore, AP-1, AP-2 and AP-3 are potentially heterogeneous due to the existence of multiple subunits isoforms encoded by different genes. However, there are few studies to demonstrate if the different combinations of APs isoforms are form and if they have distinct functional properties. This study aim to identify and characterize cellular factors involved on CD4 down-modulation induced by Nef from HIV-1. More specifically, this study aimed to characterize the involvement of AP-1 complex in the down-regulation of CD4 by Nef HIV-1 through the functional study of the two isoforms of ?-adaptins, AP-1 subunits. By pull-down technique, we showed that Nef is able to interact with ?2. In addition, our data from immunoblots indicated that ?2- adaptin, not ?1-adaptin, is required in Nef-mediated targeting of CD4 to lysosomes and the ?2 participation in this process is conserved by Nef from different viral strains. Furthermore, by flow cytometry assay, ?2 depletion, but not ?1 depletion, compromises the reduction of surface CD4 levels induced by Nef. Immunofluorescence microscopy analysis also revealed that ?2 depletion impairs the redistribution of CD4 by Nef to juxtanuclear region, resulting in CD4 accumulation in primary endosomes. Knockdown of ?1A, another subunit of AP-1, resulted in decreased cellular levels of ?1 and ?2 and, compromising the efficient CD4 degradation by Nef. Moreover, upon artificially stabilizing ESCRT-I in early endosomes, via overexpression of HRS, internalized CD4 accumulates in enlarged HRS-GFP positive endosomes, where co-localize with ?2. Together, the results indicate that ?2-adaptin is a molecule that is essential for CD4 targeting by Nef to ESCRT/MVB pathway, being an important protein in the endo-lysosomal system. Furthermore, the results indicate that ?-adaptins isoforms not only have different functions, but also seem to compose AP-1 complex with distinct cell functions, and only the AP-1 variant comprising ?2, but not ?1, acts in the CD4 down-regulation induced by Nef. These studies contribute to a better understanding on the molecular mechanisms involved in Nef activities, which may also help to improve the understanding of the HIV pathogenesis and the related syndrome. In addition, this work contributes with the understanding of primordial process regulation on intracellular trafficking of transmembrane proteins.

A dissertation submitted to the Faculty of Engineering and the Built Environment University of the Witwatersrand, in fulfillment of the requirements for the Degree of Master of Science in Engineering, 2020
Stringent SO2 emission regulations have placed immense pressure on coal-fired power plants to desulfurize exhaust flue gas. Wet Flue Gas Desulfurization (WFGD), using limestone with forced oxidation (LSFO), is a common FGD process where limestone reacts with SO2 to produce gypsum (CaSO4.2H2O). Eskom’s Kusile Power Station (Kusile) receives high-grade limestone (96% CaCO3) from Idwala Lime’s Danielskuil mine site at a top size of 19 mm and work index of 12 kWh/t. The limestone is stockpiled and conveyed to a feed preparation area where conventional wet ball milling (in closed circuit with a classifier cyclone cluster) is used to reduce the limestone particle size to 95% passing 45 μm. The Kusile ball mill specific energy is26.5 kWh/t. The dry vertical roller mill (VRM) is a novel grinding technology that dries, grinds and classifies ore within a single unit. Testwork was conducted using a pilot-scale Loesche VRM to determine the energy consumption required to grind100 t/h of the Danielskuil limestone to 85% and 95% passing 45 μm. The specific energy for these two conditions is13.7 kWh/t and 16.1 kWh/t, respectively. A wet ball mill locked cycle test was conducted at Mintek to grind the limestone to 85% passing 45 μmand resulted in a circuit specific energy of 15.4 kWh/t (compared to 13.7 kWh/t from the dry Loesche VRM testwork). The testwork data and information received from Kusile were used to set up flow diagrams and generate mass balances for equipment sizing. Various suppliers provided budgetary quotations for the different milling technologies and ancillary equipment. The total installed power for the wet ball mill circuit (including ancillary equipment) is 3,802 kW compared to 1,893 kW for the dry Loesche VRM circuit. The absorbed power for the wet and dry circuit is 2,734 kW and 1,703 kW, respectively. The mechanical cost of the wet ball milling circuit is R48,328,000 compared to R59,185,000 for the dry Loesche VRM circuit (increase of 22.5%). The different components of the capital expenditure (CAPEX) were calculated as a percentage of the mechanical cost. The CAPEX for the wet ball milling circuit and dry Loesche VRM circuit(including ancillary equipment) is R239,960,400 and R265,042,900, respectively (10.5% increase). A hot gas generator (HGG) is required in the dry Loesche VRM circuit if the moisture content of the limestone feed is higher than 6.0%. Data provided by Kusile indicated that the feed moisture content is less than 1.0%. Therefore, the HGG was not included in the main cost comparison. The stockpile and conveying areas at Kusile are large enough so that the maximum rainfall in Delmas (where Kusile is situated) should not increase the moisture content of the limestone feed to more than 6%. With the HGG included, the CAPEX of the dry Loesche VRM circuit is R286,283,200, which is 8.0% more expensive than the drycircuit without the HGG, and 19.3% more expensive than the wet ball milling circuit. No water saving is realized for this application (even though the dry Loesche VRM circuit does not require water) because a 30% solids concentration limestone slurry is required for the FGD process to be sprayed into the scrubber. The operating factor for both milling circuits is 89.8%, because the limestone consumption is dependent on the SO2 concentration in the flue gas. Therefore, the annual raw material (limestone cost) and water cost are the same for both circuits. The annual operating cost for the wet ball milling circuit and dry Loesche VRM circuit is R254,819,200and R238,890,700, respectively. The reduced OPEX is as a result of the reduced power consumption (decrease of 37.8%) and no grinding media used for the Loesche VRM. Revenue from gypsum sales (R267/t) is estimated to be R361,304,200 for both circuits. The net present value (NPV) of the wet ball mill circuit is R348,407,000 based on an assumed 20-year plant life, 12% interest rate, and 35% corporate income tax. The corresponding interest rate of return (IRR) is 20.2% with a discounted payback period (DPBP) of 4.1 years. The return on investment (ROI) is 39.9%. In comparison, the NPV of the dry Loesche VRM circuit is R408,573,000 which is 17.3% higher than for the wet ball mill circuit. An increased IRR of 21.3% is observed with a slightly reduced DPBP of 3.8 years. The ROI is 8.6% higher at 48.5%.An alternative option is for the limestone to be milled off-site (dry VRM circuit at the limestone mine) so that the dry, milled limestone is delivered to site without further grinding and/or processing required. This could result in a significantly reduced CAPEX and OPEX for the FGD process at any coal-fired power plant. It should be noted that the results obtained from this study are specific to this project and characteristics of the Danielskuil limestone ore. The aim of the study is to compare the different circuits, and not to provide an accurate overall project cost estimate. A detailed engineering study is required to increase the accuracy of the cost estimate
CK2021

The main focus of this thesis is the characterization of defects and microstructure in high-energy ball milled magnesium hydride powder and magnesium-based multilayered composites. Enhancement in kinetics of hydrogen cycling in magnesium can be achieved by applying severe plastic deformation. A literature survey reveals that, due to extreme instability of -MgH2 in transmission electron microscope (TEM), the physical parameters that researchers have studied are limited to particle size and grain size. By utilizing a cryogenic TEM sample holder, we extended the stability time of the hydride phase during TEM characterization. Milling for only 30 minutes resulted in a significant enhancement in desorption kinetics. A subsequent annealing cycle under pressurized hydrogen reverted the kinetics to its initial sluggish state. Cryo-TEM analysis of the milled hydride revealed that mechanical milling induces deformation twinning in the hydride microstructure. Milling did not alter the thermodynamics of desorption. Twins can enhance the kinetics by acting as preferential locations for the heterogeneous nucleation of metallic magnesium. We also looked at the phase transformation characteristics of desorption in MgH2. By using energy-filtered TEM, we investigated the morphology of the phases in a partially desorbed state. Our observations prove that desorption phase transformation in MgH2 is of nucleation and growth type, with a substantial energy barrier for nucleation. This is contrary to the generally assumed core-shell structure in most of the simulation models for this system. We also tested the hydrogen storage cycling behavior of bulk centimeter-scale Mg-Ti and Mg-SS multilayer composites synthesized by accumulative roll-bonding. Addition of either phase (Ti or SS) allows the reversible hydrogen sorption at 350C, whereas identically roll-bonded pure magnesium cannot be absorbed. In the composites the first cycle of absorption (also called activation) kinetics improve with increased number of fold and roll (FR) operations. With increasing FR operations the distribution of the Ti phase is progressively refined, and the shape of the absorption curve no longer remains sigmoidal. Up to a point, increasing the loading amount of the second phase also accelerates the kinetics. Microscopy analysis performed on 1-2 wt.% hydrogen absorbed composites demonstrates that MgH2 formed exclusively on various heterogeneous nucleation sites. During activation, MgH2 nucleation occurred at the Mg-hard phase interfaces. On the subsequent absorption cycles, heterogeneous nucleation primarily occurred in the vicinity of internal free surfaces such as cracks.
Materials Engineering

碩士
國立臺灣師範大學
環境教育研究所
102
“The Year of Forests” has been dated by the United Nations during 2011. Internationally, the project of “Country-driven Million Forests” have been organized to plant one million trees in 100 cities worldwide. This is an international plan to plant trees, meanwhile this is also representing one of the world’s famous tree planting activities to promote environmental education, ecological &; cultural tours, appreciation, greenery, anti-desertification, and civilization protecting works. Mongolia, located in Asia, is the world’s second-largest landlocked country with low forest cover, water scarcity, representing one of the world’s attention by her ecological strategic locations in this study. The purpose of this study is to understand“Millions Forest Plan - Planting Trees in Mongolia” to promote environmental education implications based on functional analysis of the role of environmental education participants. Qualitative research methods have been adopted by WHO-IDEA associated by depth interviews, document analysis, and participant observation, etc. This study has been carried out by cross-check the correctness of focus targets based on rigorous academic approaches to drive the methodology to boost Mongolia toward sustainable environmental education and restoration. The results show that“Millions Forest Plan - Planting Trees in Mongolia” was intended to promote environmental education meanings are indicated as follows: (1) caring for the environment awareness and environmental action can strengthen sustainable concepts while planting in young kids; (2) a planting trees action is turned as a long way to act to implement plans; (3) promoting to enhance the knowledge of environmental literacy, planting seeds from young age with appropriate place at right time by concerning the value of native species, while taking care of trees by 4-6 years, which should be respected for their life and reflected their living environment; (4) concerning the right culture of caring for the environmental attitude with the capability to focus on disaster analysis of environmental damage, and concerning for the local environment to take appropriate actions; (5) learning the skills to protect the environment, knowing the economic value of trees planted (aspects of production), supporting them made into commodities, increasing marketing profits to improve people's lives (aspects of life), while continuous planting and caring of trees to protect the water, taking care of the environment by sustainability (aspects of ecological dimension). The role in this analysis showed that the participants, experts, and scholars have been represented as objective stances. In addition, ecologists of environmental education played a dual role as scholars. An involving participant in this environmental education acted as my role-playing, then played the roles as one of the providers with intermediary functions. My research role occurred in the transfer to build in supporting for the social impacts where the key factor was that experts and scholars developed the concept of guidance, knowledge transfer, value clarification, as well as the resource providers in functions. The researcher, presenting role as the President of the Environmental Protection Association in Taoyuan County, was turned in the present study as intermediaries and recipients. The results of the follow-up experiences after this participatory action research could be continuously promoted the case of the Shimen Reservoir in Taoyuan County, retaining water catchment afforestation campaign, hoping to generate production, living and ecological benefits of the three aspects of environmental education in the country.