Dissertations / Theses on the topic 'Ball mills'
To see the other types of publications on this topic, follow the link: Ball mills.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Ball mills.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Zhang, ZhengXi. "Immobilisation of metal in quartz sands by ball milling a thesis submitted to Auckland University of Technology in fulfilment of the requirements for the degree of Master of Philosophy (MPhil), 2008." Click here to access this resource online, 2008. http://hdl.handle.net/10292/458.
Full text
2
Chieng, Heng Liang Norman, and n/a. "Amorphous drug preparation using ball milling." University of Otago. School of Pharmacy, 2008. http://adt.otago.ac.nz./public/adt-NZDU20081209.162001.
Full textAbstract:
Polymorphism and crystallinity are now recognised as important issues in drug development. This is shown by the increased amount of research in this area over recent years. In pharmaceutical development milling is an important unit operation for size reduction to improve powder handling, processing and dissolution rate. The aim of this thesis was to investigate the effect of ball milling (and cryo-milling) on the solid state properties, including amorphous drug formation, of pharmaceutical solids.
Milling was carried out using an oscillatory ball mill (Mixer Mill MM301, Retsch GmbH & Co., Germany). In cryo-milling the milling jars were immersed in liquid nitrogen for three min before milling. XRPD was used as the main technique to evaluate the milled samples. Ranitidine hydrochloride (RAN) and indomethacin (INDO) were the model drugs used in this study.
It was found that upon milling, RAN form 1 converts to RAN form 2 via an amorphous phase. A faster amorphization rate was observed when the crystalline samples were cryo-milled. Amorphous ranitidine hydrochloride was characterized to have a glass transition (T[g]) range of 13 to 30 �C and a crystallization exotherm (T[c]) between 30 and 65 �C. Conversion was found to occur faster when the temperature of the solid powder was greater than the T[c]. Under various storage conditions, similarly, crystallization of the amorphous phase mainly led to RAN form 2. However, some form 1 and amorphous phase was also detected on the XRPD diffractograms. Using partial least squares regression, the amount of solid form components in the ternary RAN mixtures were successfully quantified. RAN form 2 did not convert to form 1 under any milling (including cryo-milling) or storage conditions used in this study. Overall, RAN form 2 was found to be the thermodynamically stable form and the two (RAN) polymorphs are likely to be a monotropic pair.
In a co-milling study of INDO and RAN, the two crystalline drugs were successfully converted into a single amorphous phase after 60 min of co-milling in a cold room (4 �C). The T[g] range (26-44 �C) was also characterized for these mixtures. DRIFTS spectra of the co-milled amorphous samples indicated an interaction had occurred between the carboxylic acid carbonyl (HO-C=O) and benzonyl amide (NC=O) of the INDO molecule with the aci-nitro (C=NO₂) of RAN. Depending on the ratio of INDO to RAN, in general, the amorphous mixtures were stable at 4 �C after 30 days of storage. Crystallization was faster when the binary mixtures were stored at higher temperature or contained higher amounts of RAN in the mixture. Although XRPD and DRIFTS suggested an interaction between the two drugs, co-crystal formation was not observed between INDO and RAN.
Ball milling can be used to produce amorphous drug. The rate and extent of amorphization is dependent on the milling conditions. A faster rate of amorphization was observed when the crystalline drugs were cryo-milled. Amorphous drug formation can be made either alone or in combination with another crystalline drug. Amorphization could offer a significant improvement on the dissolution profile and the bioavailability of the poorly water soluble drug - indomethacin. Furthermore, ball milling can also be used to produce a homogenous mix between solids. The �goodmix� effect can be used for seed-induced crystallization or, when the XRPD or Raman data were combined with partial least squares regression, to create a reliable calibration model for quantitative analysis.
3
Chenje, Tapiwanashe W. "Development and validation of a model for steel grinding media wear in tumbling mills." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103372.
Full textAbstract:
Concern regarding grinding media wear is as old as the invention of the tumbling mill itself. Over the years many techniques have been tried in an attempt to minimize costs associated with grinding. These have included experimentation with different metals, non-metals and different shapes. Through all this, steel grinding balls have proved the most effective media for comminution in tumbling mills.As old as the tumbling mill is, no accurate technique for estimating the wear of the ball charge has been developed. The mining industry still utilizes the Bond Abrasion test that was developed in the early 1960s. This test which is based solely on the ore properties is inadequate giving a standard deviation in excess of 100%. This can results in high degree of error which for greenfield applications can indicate profitability for non-profitable operations and vice versa.
Peter Radziszewski proposed a decoupled total grinding media wear model that could be used to predict grinding media instead of using the Bond abrasion test. This new model had a standard deviation of 56%, which was a great improvement over the bond abrasion wear estimates. This new model also allowed for the first time, the three wear modes, abrasion, corrosion and impact, responsible for grinding media wear to be quantified. This was an important development as the ability to identify the dominant wear mode in any given operation gives operators a chance to target reduction of wear. The current mining trend is towards exploitation of lower grade ores as the higher grades become depleted. These low-grade ores require finer grinding for the liberation of the value minerals. This in turn means higher ball consumption and higher beneficiation costs. The reduction of ball wear to minimise the overall cost of ore processing operation is going to be a primary concern for all concentrators.
The objective of the research that forms the basis of this thesis was to improve the accuracy of the decoupled grinding media wear model. This was achieved by refining the tests and methodologies used to determine the wear components that make up the decoupled grinding media wear model, performing fundamental testwork to determine a more accurate structure of the decoupled model, and validating this new model.
The new model termed the "modified decoupled grinding media wear model", gives better accuracy in predicting grinding media wear than both the Bond abrasion test and the original decoupled model.
4
Freitag, Karl P. "Two-Axis Force Feedback Deflection Compensation of Miniature Ball End Mills." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-10012004-185454/.
Full textAbstract:
The primary objective of this research is to improve dimensional tolerances and reduce total manufacturing time of precision milling operations through the implementation of force-feedback machining. Force-feedback machining consists of using real-time cutting force measurement integrated with high bandwidth actuation to provide active error compensation of tool deflection. This research focuses on the development and implementation force-feedback machining using miniature (< 1 mm diameter) ball end mills. Due to the thin geometry of these tools, deflection of the tool during machining results in significant form error of the machined part. A piezoelectric two-axis force feedback actuator was designed and developed to measure and compensate for tool deflection errors of miniature ball end mills. Geometric form error was reduced by 75 % thru the application of force feedback machining.
5
Whidby, Jon Clark. "Precision machining of a turbine nozzle segment." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17306.
Full text
6
Nates, M. B. "An investigation into the parameters effecting the performance of tube mills : the behaviour of a single particle on the inside of a rotating cylinder." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/18799.
Full textAbstract:
This thesis is the first stage of a project to investigate the parameters effecting the performance of tube mills. The main topics that the project will cover are the motion of mill charge and the wear characteristics of the balls and the mill liners. A literature survey highlighted that no examination had been performed that investigated the motion of a particle with specific emphasis on the response to changes in the coefficient of friction between the particle and the liner. This thesis concentrates on the motion of a single particle moving on the inside of a smooth rotating cylinder. Three formulations are presented that model the motion of the particle. The first model assumes that the particle slides along the cylinder. To ensure that it slides, and does not roll, a block shaped particle is modelled. The second motion type assumes that a spherical shaped particle rolls along the cylinder. The assumption that is made, is that the point of contact between the ball and the cylinder does not slip or skid. This mode of rolling has been defined as Pure Rolling. A third model is proposed that is a combination of the sliding and rolling models. The formulation attempts to incorporate both actions, rolling and sliding. In this way the motion of the particle.is dependent on both the rolling and sliding interactions. The governing equations for the Sliding and Rolling models are solved numerically, using an Euler Forward Approximation. Both models are solved by a computer implementation of the resulting numerical equations. The Sliding program has been extended to animate the response of the block on the inside of the cylinder. The theoretical predictions from the two numerical solutions are presented and discussed.
7
Orumwense, Osawaru A. "The fundamentals of ultrafine grinding in vibro-energy and annular ball mills /." Luleå, 1990. http://epubl.luth.se/avslutade/0348-8373/89/index.html.
Full text
8
Spero, Christos. "The influence of coal properties on the grinding and wear characteristics of ring-and-ball pulverisers." Thesis, Queensland University of Technology, 1989. https://eprints.qut.edu.au/36451/1/36451_Spero_1989.pdf.
Full textAbstract:
This research project was broadly aimed at defining the influence of
coal properties on the grinding and wear characteristics of
ring-and-ball pulverisers.
Work undertaken included a critical review of relevant literature
concerned with the grindability and abrasion characteristics of coal,
the characterisation of coals used in relation to the pulverisers
considered, and correlation of these properties with actual
pulveriser grinding performance and wear life.
Results presented demonstrate the applicability of several model
tests to the quantification of 'hard to grind' material and the
relative grinding-energy input required for a particular coal; the
influence of coal mineralogy and physical properties on abrasiveness;
and the effect of bulk mechanical properties and moisture content on
abrasive wear of grinding surfaces. The influence of several coal
properties on performance characteristics such as capacity and
throughput, product fineness and power consumption, and wear of
grinding elements, was quantified. In addition, a semi-empirical
model describing grinding ball wear rate in terms of pulveriser
tribo-mechanical characteristics, product output and coal
abrasiveness, was developed.
9
Donkor, Sarpong Bismark. "On-line sensors for measuring the total ball and charge level in tumbling mills." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13225.
Full textAbstract:
Includes bibliographical references.Tumbling mills are still the mostly used milling device in the mineral processing industry for both coarse and fine grinding applications. A number of factors affect the performance of tumbling mill. One of these factors is volumetric filling which is the volume of charge in the mill expressed as a fraction of the total volume available. The volumetric filling controls the mill throughput, power draw and product size. The common method of measuring volumetric filling is by taking in situ measurements when the mill is stationary. This method is disruptive to production due to the mill downtime involved. The use of on-line sensors for measuring the volumetric filling using acoustic, inductive proximity and conductive sensors are the new technologies attempting to monitor volumetric filling in situ. The methods are non-intrusive and low cost approach for direct monitoring of dynamic volumetric filling conditions in the tumbling mill. The dynamic volumetric filling was assumed to be directly related to static mill filling conditions. In this study, the volumetric filling was calculated from the toe and shoulder angles estimated by the CSIRO monitor (acoustic) and the Magotteaux Sensomag (inductive proximity and conductive) sensors. The CSIRO acoustic sensor was installed on a run-of-mine (RoM) ball mill at Angloplatinum UG2 Concentrator at Rustenburg, South Africa. The toe and shoulder angles were obtained from the surface vibration caused by the impact of the charge on the mill shell. The industrial scale experiments were performed at varied mill feed rate at constant ball load of 28%. In the pilot scale experiments, the Magotteaux ball mill at Frank Concentrator was equipped with a Sensomag sensor for measuring the toe and shoulder angles of the slurry and ball load based on the principle of conductance and induction, respectively. The mill was configured to operate as a RoM ball mill. The experiments were conducted at varying mill speeds (75%-85% critical speed), feed rate (1200-2800kg/hr) and ball loads (15-26%). The static mill filling was determined from physical measurements after crash stopping the mill.
10
Becze, Charles Edward Elbestawi M. A. "A thermo-mechanical force model for machining hardened steel /." *McMaster only, 2002.
Find full text
11
Rojas, Hector E. "The effect of ball mill operating parameters on mineral liberation." Thesis, Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/50084.
Full textAbstract:
In previous studies, the analysis of ball mill operating parameters and their effects on breakage phenomena has been limited to homogeneous materials. Though these studies have proven to be an asset in predictions of product size distributions and mill scale-up, they have not addressed the primary role of grinding, i.e. liberation.
The present investigation analyzes the effect of ball mill operating parameters on the breakage rates of both liberated and composite material. The operating parameters studied include mill rotational speed, ball size, mill charge, and wet versus dry grinding. Breakage rates have been determined experimentally utilizing a SEM-IPS image analyzer. The mineral sample used was acquired from ASARCO's Young Mine which is located in Jefferson City Tennessee. It was a binary ore consisting of sphalerite and dolomite.
Batch grinding experiments were conducted to provide breakage rates for the various composition classes. Breakage rates were then normalized with respect to energy to see if the changes in breakage rates associated with mill operating parameters were due to changes in breakage kinetics, or simply a function of energy input.
The energy normalized data indicates that the free dolomite breakage rates tend to normalize with respect to energy in the case of varying interstitial fillings. Furthermore, changes in mill rotational speed tend to provide energy normalizable breakage rates for both free dolomite and sphalerite. In all other cases, analysis of the breakage rates and energy-specific breakage rates indicate that a change in breakage kinetics may be occurring.
In general, particles containing a high proportion of sphalerite are more apt to break under impact conditions. On the other hand, particles containing a large proportion of dolomite were found to prefer attrition breakage conditions.Master of Science
incomplete_metadata
12
Xiao, Zhixian 1970. "Characterizing the gravity recoverable platinum group minerals." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115859.
Full textAbstract:
Modeling gravity recovery of platinum group minerals (PGMs) in the grinding circuit is based on three components: Ore characterization of gravity recoverable platinum group minerals (GRPGM), their behavior in grinding mills and hydrocyclones, and the performance of the gravity recovery units. This thesis focuses on the first two components.A laboratory methodology to characterize gravity-recoverable platinum group minerals (GRPGMs) in an ore with four incremental liberation and recovery stages was developed. It was applied to quantify GRPGM content of four ore samples from Canada. To measure the behavior of GRPGMs in the grinding circuit, a methodology to characterize the already liberated (or available) GRPGMs in the circuit streams was developed. The availability of GRPGM in streams, such as ball mill discharge, was used to model the behavior of the GRPGMs in the ball mills and hydrocyclones. Combining with the potential GRPGM in an ore, they can be used for design and/or optimization of platinum group mineral recovery circuit.
The GRPGM content measured by this methodology varied from 5 to 81% depending on the ore. The GRPGM size distribution varied from fine (most GRPGM below 37mum) to coarse (significant content above 212 mum). The stage size-by-size recovery and the total GRPGM content indicate that the methodology can quantify the GRPGM content of ores.
Based on the measurement of the availability of GRPGM in process streams, the behavior of PGMs in ball mills and hydrocyclones is characterized in terms of the less common cumulative selection functions and conventional classification efficiency curves. Mineralogical analysis indicates that sperrylite (PtAs 2) is the dominant platinum mineral at the Clarabelle mill. Its classification efficiency is similar to that of gold, despite its lower density, while grinding rate is significantly higher than gold. The cumulative selection function of platinum and palladium is 1.3 times higher than the ore for size classes above 212 mum and 50 to 70% of the ore below 212 mum.
As a result, sperrylite accumulates in finer sizes than native gold in the grinding circuit. The cumulative selection function of the platinum group minerals was calculated for the Clarabelle grinding circuit based on the survey data and the GRPGM contents in the ball mill discharge, cyclone underflow, and overflow.
The methodology of characterizing the content of GRPGMs in an ore also offers a way to concentrate the minerals for mineralogical study. The use of secondary electron microscopy (SEM), variable pressure SEM and QEM*SEM for qualitative analysis of platinum group mineral mineralogy is presented and discussed. Most of the GRPGMs recovered are well liberated. Qualitative mineralogical analysis of the GRPGM and its associations in ore samples are also discussed.
13
Del, Villar René. "Modelling and simulation of Brunswick mining grinding circuit." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72758.
Full text
14
Silva, Daniel Nagano da. "Análise de criticalidade de defeitos em munhões de moinhos de bolas usados em plantas de mineração." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-26082014-093342/.
Full textAbstract:
Os moinhos de bolas são equipamentos presentes em plantas de mineração, sendo uma máquina importante no circuito de cominuição de minérios. Em função de inúmeros fatores como, por exemplo, projeto, fabricação, sobrecarga no equipamento, falta de manutenção e procedimentos de operação inadequados, são desenvolvidas descontinuidades nos componentes estruturais desse equipamento. Os componentes estruturais dos moinhos, basicamente, corpo, tampas e munhões, além do custo elevado, possuem prazos de fabricação que podem variar de dois a três anos dependendo da demanda do mercado. Portanto é cada vez mais necessário que as descontinuidades detectadas nesses componentes sejam corretamente avaliadas. Neste trabalho analisaram-se pela mecânica da fratura a criticalidade de descontinuidades, tais como trincas constatadas em um munhão de um moinho de bolas e compararam-se os valores teóricos de taxa de propagação (crescimento) dessas descontinuidades com valores reais obtidos por meio de inspeções periódicas realizadas neste componente. A nucleação das trincas foi causada por falta de lubrificação nos mancais do moinho, gerando esforços térmicos circunferenciais no munhão, em que a temperatura estimada do contato munhão e bucha atingiu a faixa de 100 °C a 150 °C. No período analisado, os resultados obtidos por meio da norma BS7910 mostraram-se mais próximos dos valores reais do que a norma ASME Seção XI, Apêndice A. O tamanho da trinca mais crítica foi aceito pelos critérios da norma BS7910 e aprovado apenas na condição de emergência da norma ASME Seção XI, Apêndice A.The grinding ball mills are equipments present in mining plants, being important in the ore comminution circuits. Depending on numerous factors, such as, for example, design, manufacturing, overloads, poor maintenance and inadequate operating procedures, flaws are developed in the structural components of this equipment. The structural components of a mill, basically, shell, heads and trunnions, besides high costs, have lead times that might vary from two to three years, according to market demand. Therefore, it becomes increasingly necessary that any flaws in those components to be properly evaluated. This paper analyzed the fracture mechanics of the criticality of flaws, such as cracks observed in a ball mill trunnion and compared the theoretical values of growth rate of these defects with actual values obtained through periodic inspections performed in this component. The cracks nucleation was caused by lack of lubrication in the trunnion bearings, generating circumferential thermal stresses, thus the estimated temperature of the trunnion and bushing contact achieved the range 100 °C to 150 °C. During the analyzed period, the results obtained by the standard BS7910 proved to be closest to the actual values than the standard ASME, Section XI, Appendix A. The most critical crack size was accepted by the criteria of the BS7910 and approved only on emergency condition of ASME Section XI, Appendix A.
15
Yeboue, Kouadio Yves. "Peptide Synthesis by Mechanochemistry : From Fundamental studies to Scale-Up." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS077.
Full textAbstract:
Compte tenu du durcissement des politiques environnementales vis-à-vis des polluants produits par l’industrie chimique et de la demande croissante de la part des consommateurs et des citoyens, il est impératif de trouver des méthodes alternatives aux procédés utilisant des quantités importantes de solvants et réactifs nocifs pour la santé et l’environnement. Les méthodes classiques de synthèse de peptides en font partie et nécessitent impérativement des améliorations. Ce manuscrit décrit les récents développements des procédés mécanochimiques en synthèse peptidique, procédés qui permettent un changement de paradigme par rapport aux procédés classiques utilisant des solvants. Ces procédés mécanochimiques sont utilisés au cours de cette thèse pour solutionner des problèmes d’épimérisation de peptides fréquemment rencontrés lors de l’emploi de la stratégie de couplage par fragment en solution. La preuve de faisabilité du couplage peptidique par ligation chimique native par broyage à billes a également été apportée au cours de cette thèse. L’approche de synthèse peptidique par mécanochimie a enfin été utilisée pour mettre au point des conditions efficaces permettant de monter en échelle la synthèse de peptides en utilisant le procédé d’extrusion réactive, ouvrant les portes à un transfert de la synthèse à l’échelle industrielle. L’ensemble de ces conditions mécanochimiques se sont avérées particulièrement efficaces quant à la synthèse de peptides avec des temps de réaction très faibles, d’excellents rendements, des taux d’épimérisation très faibles, un faible impact environnemental et une grande productivitéDue to the restriction of the environmental policies regarding the pollutants, it is urgent to find alternative methods to the processes that used large amount of highly toxic solvents and chemicals. Because of their negative environmental impact, conventional peptide synthesis methods require improvements. The use of mechanochemical processes allow to efficiently reduce the environmental impact by eliminating or replacing toxic solvents and chemicals. During this work, mechanochemical methods have been used to solve the peptide epimerization issues, frequently encountered during peptide fragment coupling strategy in solution. Additionally, by using these methods, peptide synthesis through native chemical ligation was also demonstrated. Furthermore, the use of the reactive extrusion process has enabled to efficiently work on large scale, thereby opening the boulevard to implement the peptide mechanosynthesis in industries. Finally, these methods have led to the desired peptides with noteworthy isolated yields, very short reaction times, low epimerization rate, low environmental impact and high productivity
16
Wang, Chengtie. "Comparison of HPGR - ball mill and HPGR - stirred mill circuits to the existing AG/SAG mill - ball mill circuits." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/43896.
Full textAbstract:
In the past 20 years, the energy-efficient comminution technologies, including high pressure grinding rolls (HPGR) and high speed stirred mill, have been developed and adopted in the hard-rock mining operation in order to reduce the energy consumption and improve the process performance. The combination of HPGR and stirred mill in a single flowsheet without tumbling mills has been demonstrated to be technically feasible. This research focused on the energy and cost comparisons of the existing AG/SAG ball mill circuits with two proposed comminution circuits, including an HPGR - ball mill circuit and a novel HPGR - stirred mill circuit.
The main objective of this research was to advance the understanding of the potential benefits of the proposed HPGR stirred mill-based comminution circuits for low-grade, high -tonnage base metal operation. Samples and operating data were collected directly from the existing SAB/AGBC/SABC circuits to establish a base case for comparison. To support the base case, the existing circuits were fitted and simulated using a JK SimMet® model. Specific energy requirements for the proposed HPGR - ball mill circuit and HPGR - stirred mill circuit were determined from a pilot-scale HPGR and stirred mill test, in association with a JK SimMet® simulation.
Results obtained from the research showed that the HPGR - ball mill circuit and HPGR - stirred mill circuit achieved a substantial reduction in energy, with considerable cost advantage over the existing SAB/AGBC/SABC circuits.
17
Orozco, Luisa. "Modélisation numérique et rhéologie des milieux granulaires à particules fragmentables en vue d’application aux broyeurs à boulets." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS101.
Full textAbstract:
Une étape cruciale de la fabrication des combustibles nucléaires est le co-broyage des oxydes d’uranium et de plutonium pour obtenir une taille ciblée et un mélange homogène de particules. Cependant, le changement de l’échelle du laboratoire à celle de la production reste essentiellement empirique. Le but de cette thèse de doctorat est de modéliser et caractériser les écoulements granulaires dans des tambours rotatifs et d’élucider les mécanismes de broyage de l’échelle des particules à celle du procédé. A l’aide de simulations granulaires, et d’un critère de décohésion dynamique basé sur la mécanique de la rupture, on étudie la fragmentation de partic- ules sous impact. La dissociation de ces particules se fait au niveau d’une tessellation en cellules sous-jacentes fragmentables. Les analyses développées portent notamment sur : les propriétés d’écoulements granulaires dans le régime de cascade en fonction des paramètres du système; l’effet de la taille et du nombre de corps broyants sur le processus de broyage; l’évolution de la frag- mentation dans les écoulements en tambour rotatif. Nos simulations révèlent plusieurs relations bien définies entre différentes variables caractérisant l’écoulement (profil de surface, épaisseur d’écoulement, fluctuations de force, glissement aux parois), l’évolution de la taille des particules et les paramètres du système (vitesse de rotation, taille du tambour, taux de remplissage). Ces travaux conduisent à la définition d’un paramètre sans dimension qui peut être utilisé pour la mise à l’échelle des écoulements dans les tambours tournants et les broyeurs à bouletsA crucial step of nuclear fuel manufacture is the co-milling of uranium and plutonium oxides to obtain a targeted particle size and excellent mixing. However, the scale-up from the laboratory to plant production is still mainly empirical. The goal of this doctoral thesis is to model and characterize granular flows in rotating drums and to elucidate the mechanisms of particle grinding across scales. By means of particle dynamics simulations and a particle breaking model involving the tessellation of breakable particles into cells and a dynamic debonding criterion based on fracture mechanics, we investigate single- particle impacts, the properties of granular flows in the cascading regime in a rotating drum as a function of system parameters, the effect of the size and amount of grinding media on the grinding process, and the evolution of particle breakage in granular flows of breakable particles. Our simulations reveal several well- defined relationships between flow variables such as surface profile, flowing thickness, force fluctuations and wall slip, as well as with system parameters such as rotation speed, drum size and filling degree, and with particle fracture during flow. We identify a dimensionless parameter that can be used for the scale-up of rotating drums
18
Yesilay, Yasemin Ayse. "A Computer Simulator For Ball Mill Grinding." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605350/index.pdf.
Full textAbstract:
Ball mill grinding is an important operation in the processing of most minerals, in that it may be used to produce particles of the required size and shape, to liberate minerals from each other for concentration purposes, and to increase the powder surface area. Grinding of minerals is probably the most energy consuming task and optimization of this operation has vital importance in processing plant operations to achieve the lowest operating costs. Predicting the complete product size distribution, mill specifications and power draw are important parameters of this optimization.
In this study, a computer simulation program is developed in MATLAB environment to simulate grinding operations using the kinetic model in which comminution is considered as a process continuous in time. This type of model is commonly and successfully used for tumbling grinding mills having strongly varying residence time as a function of feed rate.
The program developed, GRINDSIM, is capable of simulating a ball mill for a specified set of model parameters, estimating grinding kinetic parameters from experimental batch grinding data and calculating continuous open and closed-circuit grinding behavior with mill power input. The user interacts with the program through graphical user interfaces (GUI&rsquos).
19
Denlinger, Kendra L. "Polymers in the High-speed Ball Mill." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin149156005684791.
Full text
20
Hopgood, Heather M. "Substitution Reactions in the High Speed Ball Mill." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479816113315302.
Full text
21
Keshav, Pratish. "Optimisation of an industrial scale ball mill using an online pulp and ball load sensor." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/16463.
Full textAbstract:
The secondary milling circuit at Waterval UG2 Concentrator had undergone a circuit change with the commissioning of the IsaMill, a horizontally stirred mill, in parallel with the secondary ball mill. The operation treats the PGM bearing UG2 ore type and produces a final concentrate enriched with PGM's. The concept was to treat the finer silicate rich fraction in the IsaMill and the coarser chromite rich fraction through the ball mill. This circuit is typical of a UG2 plant in which maximum silicate with minimal chromite breakage is targeted. As a result of the circuit change an opportunity for optimisation around the industrial scale ball mill was considered for this study. Of concern in this study were new operating conditions for the mill in the changed circuit at which improved performance could be obtained. Another objective was to investigate if a difference in breakage response for the silicate and chromite fractions could be identified for different operating conditions in the ball mill. The secondary mill at Waterval UG2 Concentrator was already fitted with an online ball and pulp load sensor, the Sensomag. The information obtained from the sensor is in the form of shoulder and toe positions for the ball and pulp filling in the rotating ball mill. The mill was surveyed at various ball filling and mill % solids conditions and information from the online sensor was used to understand the mill performance, particularly with regards to mill load behaviour. Hence a final objective was to demonstrate that the information obtained from the online sensor could be related to mill operating conditions. The sensor output was envisioned to eventually form part of the mill control philosophy. Samples were taken of the mill feed and discharge streams at the different operating conditions and analysed for grind as well as PGM and Cr₂O₃ content. The majority of the PGM's in the UG2 ore are in the silicates and thus the PGM distribution results would indicate the amount of breakage in the silicate fraction. Cr₂O₃ is used as an indicator of the chromite content in UG2 ore. In order to identify optimum mill performance the results were analysed using different measures which include general grind, particle and species distributions, reduction ratios, sieve efficiencies and specific energy. By comparing the results the differences and limitations of certain techniques were identified. It was found that the mill performance varied at different operating conditions. The optimum ball filling was found to be around 30%, which is similar to site operational target. The optimal % solids for this mill however seems to be higher than what the mill is typically operated at. No peak in % solids for mill performance was obtained. Scope exists to determine how far from the investigated maximum of 75% solids (by mass) does the optimum in-mill density lie for this mill. Thus new optimum conditions in terms of % solids do exist for the mill in the modified circuit. Results also showed that the size reduction of the silicates increased with an increase in mill % solids and ball filling degree. For chromite, the mill % solids did not appear to have any effect at low ball fillings, but a slight shift was observed at the higher ball fillings tested. The trend suggests that the size reduction of both silicates and chromite increased with an increase in ball filling, albeit at different rates. Finally, the test work has demonstrated that the online sensor outputs can be related to mill performance. Differences in shoulder and toe positions for the ball and pulp loads were distinct between operating conditions. Improved grind performance was observed at conditions that resulted in lower free pulp angles. Thus the sensor could be used as a control tool to identify and maintain optimum mill operational conditions. The Sensomag should be incorporated into a mill controller that looks at more than just mill ball filling. Conditions that result in optimum mill efficiency can be identified and the mill may be controlled using the sensor data. It is recommended that the mill continue to be run at 30% ball filling and at higher mill % solids than the maximum reached in this work.
22
Kendrick, Allen E. "Defect characterization in cast steel ball mill ring gears." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66196.
Full text
23
Haley, Rebecca. "Nickel Mediated Reactions in a High-speed Ball Mill." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535635347164016.
Full text
24
Zachariades, Paschalis. "Development of a Tube Ball mill mathematical model for mill condition and safety monitoring." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5723/.
Full textAbstract:
The PhD research project is to examine if it is possible to minimize the mill faults and fires in the Tube Ball mill operation by using a model based approach. The research outcome proves that the risks of mill fault can be monitored and alerted by implementing the model based on-line condition monitoring software that developed through the PhD project. Coal fired power stations nowadays regularly use coal with higher volatile contents and Biomass materials to satisfy the government regulations on sustainable and renewable energy. This greatly increases the risks of explosions or fires in milling plants. However, there are no acceptable measurement methods available at the present and it is difficult to identify if there will be a fire in the mill. Therefore, the project is carried out from the study mill mathematical model to mill condition monitoring. Monitoring the mill operation conditions only based on currently available on-site measurement without requiring any extra hardware is a cost effective solution and will pose a great challenge. A mathematical model of coal mills is developed using computational intelligent algorithms for prediction of potential mill faults.
25
Geng, Lei 1971. "Design and development of a cam-driven laboratory ball mill." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82488.
Full textAbstract:
In mineral processing industries, grinding processes can be defined as the particles reduced in size by a combination of impact and abrasion. It is performed in tumbling mills that describe a class of mills delimited by a cylindrical chamber filled with balls and/or rock that rotate around its longitudinal axis. Tumbling mills, whether they are autogenous, semi-autogenous, ball or rod, are classed according to the nature of the discharge as centre peripheral discharge mills, end peripheral discharge mills, overflow mills, and grate discharge mills. These mills are used in at least three industries: mining, cement and metal powders industries to grind different materials (ore, clinker and metal powder) to desired quality specifications as principally described by a size distribution. These tumbling mills range in size from small 0.3 m diameter lab mills to a 16 m diameter semi-autogenous industrial mill and are driven by chain and sprocket (lab mills), gear and pinion (pilot and industrial scale mills) and gearless drives in very large diameter mill (8 to 12 m dia.). All of these mill drives present advantages and limitations.In this thesis, we focus on the design and development of a cam-driven laboratory ball mill. An alternative drive system is presented that uses a newly patented speed-o-cam technology and applies it to a 5 ft diameter lab mill. We introduce polynomials to modify the cam profile around both the cusp and the blunt point of the profile to improve pressure angle and shock impact. We build models of mechanical systems, simulate the full-motion behavior of the models, and analyze multiple design variations. We integrate the theoretical, virtual and experimental analyses in order to design an optimal mechanical system. Moreover, the analysis of static and dynamic forces of cam mechanism is reported in the thesis.
26
Ajaal, Tawfik Taher. "The development and characterization of a ball mill for mechanical alloying." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0001/MQ45271.pdf.
Full text
27
Ravalico, Francesco. "Derivatisation of nucleosides, nucleotides and their analogues in a ball mill." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602942.
Full textAbstract:
Vibrating ball mill enabled chemoselective acylation of primary amines (including nucleoside analogues) within ten minutes using avoiding undesirable solvents which are typically employed for such reactions (e.g., DMF). A model reaction between propargylamine and the N-hydroxysuccinimidyl ester of p-phenylazobenzoic acid was optimised with respect to the milling frequency, equivalents of propargylamine, and the equivalents and strength of additional base / catalyst. Under optimised conditions, synthesis of amides in the presence of primary and a secondary alcohol functions was achieved in high to excellent yields (65 - 94%). The addition of ethyl acetate was found to both significantly accelerate reaction rates using solid substrates and enhance chemoselectivity. Overall, the optimised methods demonstrated to have significant practical advantages over conventional solvent- approach including greater yields; higher chemoselectivity and easier product separation. Atom-efficient pyrophosphate coupling between adenosine 5'-phosphoromorpholidate and 5'- riboside mono-, di-, or tri-phosphates was achieved using liquid-assisted grinding in a ball mill. This methodology avoided the use of anhydrous pyridine, dmf or formamide and thereby enabled the use of commercially-available donors and acceptors (as their alkali or alkaline earth metal salts) without extensive pre-reaction processing to generate organic-soluble materials. A dramatic reduction in reaction times (to 90 minutes) did not prejudice the yields (50 - 87% HPLC yield) a rapid purification using reversed-phase HPLC was facilitated.
28
Khonthu, Tsepang. "Investigation of the flotation behaviour of ball mill and IsaMill products." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10979.
Full textAbstract:
Includes bibliographical references.Valuable minerals that are used in various aspects of everyday life are buried in fossilised storages below the ground in the earth's crust. These minerals are mined as rocks which then have to be crushed in order to liberate these minerals of value. The liberated valuable minerals have to be winnowed from the rock powder. Flotation is the main process which is used in mineral processing to recover valuable minerals. This process uses the differences in surface properties of particles to separate hydrophobic particles from hydrophilic ones. The strong relationship between the method of crushing the rocks and the amount of valuable minerals which can be reclaimed from the crushed rock has long been realized in mineral processing. The type of mineral, the size to which the rock must be reduced to and the amount of energy needed for this size reduction are among the most important factors which guide the decision on the type of device to be used in pulverising mineral rocks. Physical properties, with the exception of particle size, of mill products have not been investigated as thoroughly as the chemical properties. Physical properties include surface roughness and particle shape. The differences in shape, between particles produced by different mills, with respect to these properties, have been attributed to differences in the breakage mechanisms in the mills used to grind the particles. There is contradicting literature on the breakage mechanisms that dominate in various mills. This confusion is exacerbated by the fact that different breakage mechanisms occur simultaneously in any one mill. The definition and determination of particle shape are also difficult. Subsequently, the effect of particle shape on flotation is a subject that is rife with contradictions which add to the complexity of the subject.
29
Cook, Teresa L. "Developing Green One-Step Organic Reactions in the High Speed Ball Mill." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1397736534.
Full text
30
Andersen, Joel M. "Understanding the Mechanochemical Energetics of a SPEX 8000M Mixer/mill." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563273418808903.
Full text
31
Acar, Cemil. "Investigation Of Particle Breakage Parameters In Locked-cycle Ball Milling." Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615427/index.pdf.
Full textAbstract:
Size reduction processes, particularly fine grinding systems, in mineral processing and cement
production plants constitute a great portion of energy consumption and operating costs. Therefore, the
grinding systems should be designed properly and operated under optimum conditions to achieve
productive and cost effective operations. The use of simulation based on kinetic mathematical models
of grinding has proven useful in this respect. The kinetic models contain two essential parameters,
namely, breakage rate and breakage distribution functions, that are to be determined experimentally,
and preferably in laboratory, or by back-calculation from the mill product size distribution for a given
feed size distribution.
Experimental determination of the breakage parameters has been mostly carried out in laboratory
batch mills using one-size-fraction material. The breakage rate parameter is obtained from the
disappearance rate of this one-size-fraction material, while the breakage distribution parameters are
estimated from the short-time grinding of the same material. Such laboratory methods using one-size
fraction material, however, are not truly representative of industrial continuous mill operations where
the mill contents have a distribution of particle sizes. There is evidence in the literature that the size
distribution of the mill contents affects the breakage parameters.
This thesis study was undertaken with the main purpose of investigating the effect of the size
distribution of the mill hold-up on the brekage parameters of quartz and calcite minerals in lockedcycle
dry grinding experiments. The locked-cycle and one-size-fraction experiments were performed
in the Bond ball mill instrumented with a torque-measuring device. Different closing screen sizes
were used in the locked-cycle work to produce different size distributions of the mill hold-up, and the
operating conditions were changed in the one-size-fraction experiments to obtain different power
draws. Particle breakage parameters were assessed for these changing conditions.
Prior to the experiments related to the main purpose of the study, preliminary experiments were
conducted for two reasons: (i) to find the power draw of the Bond mill in relation to the operating
conditions with the intention of eliminating the use of costly torque-measuring devices by othersand (ii) to find the most accurate estimation method of breakage distribution functions among the three existing methods, namely, the &ldquo
zero-order production of fines&rdquo
method, the BII method, and the G-H method. The G-H method was found to be more appropriate for the current study. The locked-cycle grinding experiments revealed that the breakage rate function of coarse fractions increased with increasing proportion of fines in the mill hold-up. Breakage distribution functions were found to be environment-dependent and non-normalizable by size in one-size-fraction and locked cycle grinding experiments. It was concluded that the cumulative basis breakage rate function could sufficiently represent the breakage characteristics of the two studied materials in a wide range of operating conditions. Therefore, it would be more appropriate to evaluate the breakage characteristics of materials ground in ball mills by linearized form of the size-discretized batch grinding equation using single parameter instead of dealing with two parameters which may not be independent of each other.
32
Avşar, Hakan Doymaz Fuat. "Control, Optimization And Monitoring Of Portland Cement (Pc 42.5) Quality At The Ball Mill/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/kimyamuh/T000365.pdf.
Full text
33
Johansson, Anna. "Correlation between process parameters and milling efficiency." Thesis, Uppsala universitet, Oorganisk kemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-179625.
Full textAbstract:
An experimental ball-milling study was performed to compare the deagglomeration behavior and the evolution of the particle size distribution with increasing milling time of two relatively coarse WC powders used for the production of cemented carbide cutting tools. The WC-powders were found to have distinctly different particle size distributions and particle morphologies prior to milling. Lab-scale WC samples were made using a range of different process parameters and milling times. These were then analysed by means of microscopy, laser light scattering, gas adsorption BET analysis and X-ray powder diffraction, XRD, to attain particle size distribution, specific surface area and a mean crystal size, respectively. The results suggested a linear relation between log(particle size) and log(milling time) between 10 and 80 hours milling. The viscosity was shown to have a minor effect on the milling efficiency. Both the number of collisions of milling balls per unit time as well as the kinetic energy of the milling ball affected the size reduction; more collisions or higher energy resulted in a higher milling efficiency. The evaluation of the effect of the process parameters on milling efficiency was facilitated by the use of simple scaling factors. For example, all milling curves for samples with different WC amounts coincided when rescaling the milling time using a scaling factor based on the weight of the WC and milling balls. The same scaling factor could be used with success for rescaling the results from different trials obtained with laser light scattering, gas adsorption and XRD. The results of this work are useful for future work on modeling of the milling process which should lead to more accurate predictions of the outcome of milling unit operations.
34
Prado, Guilherme Cervi. "Study of reaction parameters in ball mill in the Synthesis of aryl(heteroaryl)-1h-pyrazoles." Universidade Federal de Santa Maria, 2012. http://repositorio.ufsm.br/handle/1/10505.
Full textAbstract:
Conselho Nacional de Desenvolvimento Científico e TecnológicoIn order to eliminate the problems related to deficient intake of vitamins folate class, many food products are being subjected to the enrichment process. Among them, all types of wheat flour must be enriched with folic acid. Therefore, it is evident the need of analytical methods for routine able to effectively determine the levels of folic acid in enriched matrix. The objective of this work was the development and validation of a rapid method for determination of folic acid added to wheat flour, using the technique of high performance liquid chromatography with UV detection. Folic acid was separated using a C8 column. Was used for elution gradient mobile phase with water acidified with glacial acetic acid (pH 2.8) and acetonitrile. Detection was performed with a diode array detector employing a wavelength of 290 nm. External standard was used for quantification. Vitamin matrix was extracted with aqueous potassium hydroxide, 0.1 mol L-1 and aqueous sodium tetraborate 0.04 mol L-1 pH 8.5, followed by cleaning step of the extract of the sample through SPE using SAX cartridges. The method was efficient, with recovery values between 96 and 99%, RSD from 1.3 to 3.8% and LOD and LOQ of 0.28 and 0.937 mg kg-1, respectively. In the analysis of real samples of five brands tested, only one brand presented concentration of folic acid above the minimum required by law.
Com o objetivo de suprimir os problemas relacionados à deficiência de ingesta de vitaminas da classe dos folatos, muitos produtos alimentícios estão sendo submetidos ao processo de enriquecimento. Entre eles, todos tipos de farinha de trigo devem ser enriquecidos com ácido fólico. Portanto, fica evidenciada a necessidade de métodos analíticos para a rotina capazes de determinar com eficácia os níveis de ácido fólico na matriz enriquecida. O objetivo deste trabalho foi o desenvolvimento e validação de um método rápido para determinação de ácido fólico adicionado a farinha de trigo, através da técnica de cromatografia líquida de alta eficiência com detector espectrofotométrico. O ácido fólico foi separado utilizando-se coluna de C8. Utilizou-se eluição por gradiente na fase móvel, com água acidificada com ácido acético glacial (pH 2,8) e acetonitrila. A detecção foi efetuada com detector por arranjo de diodos empregando o comprimento de onda de 290 nm. Foi utilizada padronização externa para quantificação. A vitamina foi extraída da matriz com solução aquosa de hidróxido de potássio 0,1 mol L-1 e solução aquosa de tetraborato de sódio 0,04 mol L-1 de pH 8,5; seguida por etapa de limpeza do extrato da amostra através de SPE, utilizando cartuchos de SAX. O método mostrou-se eficiente, com valores de recuperação entre 96 e 99%, RSD de 1,3 a 3,8% e LOD e LOQ de 0,28 e 0,937 mg kg-1, respectivamente. Nas análises das amostras reais, das cinco marcas analisadas, somente uma marca apresentou concentração de ácido fólico acima do mínimo exigido pela legislação.
35
Sabau, Melania. "Analysis and modeling of an integrated sag-rod-ball mill ore comminution process using JKSimMet Simulator." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ31466.pdf.
Full text
36
Borchardt, Lars, and Sven Grätz. "Mechanochemical polymerization – controlling a polycondensation reaction between a diamine and a dialdehyde in a ball mill." Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A30231.
Full textAbstract:
The mechanochemical polycondensation between a diamine and a dialdehyde constitutes a sustainable alternative to classical solvent-based polymerization reactions. This process not only allows for a higher conversion and a shorter reaction time as compared to standard solvent-based syntheses of this conjugated polymer, but the reaction can also be adjusted by the energy introduced via the ball mill.
37
Borchardt, Lars, and Sven Grätz. "Mechanochemical polymerization – controlling a polycondensation reaction between a diamine and a dialdehyde in a ball mill." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-221833.
Full textAbstract:
The mechanochemical polycondensation between a diamine and a dialdehyde constitutes a sustainable alternative to classical solvent-based polymerization reactions. This process not only allows for a higher conversion and a shorter reaction time as compared to standard solvent-based syntheses of this conjugated polymer, but the reaction can also be adjusted by the energy introduced via the ball mill.
38
Yang, Jian. "Thermoelectric Properties of CoSb3-Based Skutterudites." Thesis, Boston College, 2010. http://hdl.handle.net/2345/1418.
Full textAbstract:
Thesis advisor: Zhifeng RenSolid state cooling and power generation based on thermoelectric principles are regarded as one of the technologies with the potential of solving the current energy crisis. Thermoelectric devices could be widely used in waste heat recovery, small scale power generation and refrigeration. It has no moving parts and is environmental friendly. The limitation to its application is due to its low efficiency. Most of the current commercialized thermoelectric materials have figure of merit (ZT) around 1. To be comparable with kitchen refrigerator, ZT is required at room temperature. Skutterudites have emerged as member of the novel materials, which potentially have a higher ZT. In the dissertation, my investigation will be focused on the optimization of CoSb3 &ndash based skutterudites. Starting with Co and Sb elements, CoSb3 will form through a high energy ball mill. Unfortunately, even after 20 hours, only a small percentage of the powders have transformed in into CoSb3. Then the powders will be compacted into bulk samples by DC-controlled hot press. CoSb3 single phase will form after press. Characterization of the structure and thermoelectric properties will be presented with details. The effects of synthesis conditions on thermoelectric properties of skutterudites were studied and discussed. Several possible methods of improving the ZT of N type skutterudites were applied. The highest obtained ZT thus far is about 1.2 from Yb doped CoSb3. For a group of samples with nominal composition YbxCo4Sb12, the increased Yb concentration in our samples not only enhanced the power factor due to electron doping effect but also decreased the thermal conductivity due to a stronger rattling effect. In addition, the increased grain boundary density per unit volume due to the small grains in our bulk skutterudite materials may have also helped to enhance the phonon scattering and thus to reduce the thermal conductivity. Single and double doping methods with different combinations were also tried. So far, none of them have surpassed ZT of 1.2. Mixing different materials with Yb0.35Co4Sb12 so far to increase the phonon scattering was also performed. No dramatic thermal conductivity reduction was observed. Small amounts of Fe/Mn substitution on Co sites will decrease the power factor to undesired degrees. Some results with Nd filled P type sample will be briefly introduced. P type samples are also obtained through substitution on Sb site. Preliminary work on preparing the electrode for CoSb3 will be presented in the dissertation. CoSi2 has low resistivity, and a similar coefficient of thermal expansion (CTE) as of doped CoSb3. It is good electrode candidate. DC controlled hot press is used to make the contact. Thermal stability of the contact was tested. Small cracks will form in the contact area, further improvement is necessary. Finally, my previous work on ZnO nanowire growth is briefly introduced. Large throughput of ZnO nanowire could be obtained with NaCl as the support to promote the conversion of Zn powder to ZnO
Thesis (PhD) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
39
Solomon, Nomonde. "Effect of HPGR on platinum bearing ores and the flotation response as compared to the conventional ball mill." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11277.
Full textAbstract:
Includes abstract.Includes bibliographical references.
This thesis focuses on the application of the high pressure grinding rolls (HPGR) on platinum bearing ores Merensky, UG2 and Platreef. Conventional tumbling mills such as the ball mill that are typically applied on these ore types are highly energy intensive with a small percentage of the input energy being used for actual breakage. Rapidly increasing energy costs have contributed to the rising interest of the HPGR in the platinum industry, particularly in plants processing UG2 and Platreef ores. Therefore, this thesis seeks to determine if the HPGR can be used as an alternative to the ball mill. Key aspects of interest are throughput, energy efficiency, PGE grade and recovery and PGM liberation.
40
Caiti, Massimiliano. "Mechanochemistry: a new approach to depolymerize cellulose via solid-solid reaction." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14434/.
Full textAbstract:
Cellulose is both insoluble in water and resistant against hydrolysis. These features pose major problems for its conversion into platform chemicals, first of all glucose. Herein, is demonstrated that the combination of mechanical forces and the presence of solid acid catalysts leads to the full conversion of cellulose into oligosaccharides. In this way mechanochemistry results an available route to depolymerize cellulose via solid-solid reaction. In this work is described the whole developed methodology which permits to obtain a quantifiable final products from the milling of a cellulosic substrate. Furthermore is reported the analytic method constructed thanks to which it is possible to determine the cellulose conversion and thus compare the performances of various solid acids tested. This study has moreover allowed to understand important catalyst features that enhance the depolymerization rate, such as the distribution of the acid sites on a inert support. Amberlyst 15, producing 100% of oligosaccharides in 15 hours of milling at 500rpm, is resulted the more active catalysts among those studied. Thanks to its high activity were performed performances comparison of the different ball mills employed.
41
Machover, Sarah B. "Understanding the Solvent-free Nucleophilic Substitution Reaction Performed in the High Speed Ball Mill (HSBM): Reactions of Secondary Alkyl Halides and Alkali Metal-Halogen Salts." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307043848.
Full text
42
Camalan, Mahmut. "Size-by-size Analysis Of Breakage Parameters Of Cement Clinker Feed And Product Samples Of An Industrial Roller Press." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614594/index.pdf.
Full textAbstract:
The main objective in this study is to compare breakage parameters of narrow size fractions of cement clinker taken from the product end and feed end of industrial-scale high pressure grinding rolls (HPGR) in order to assess whether the breakage parameters of clinker broken in HPGR are improved or not. For this purpose, drop weight tests were applied to six narrow size fractions above 3.35 mm, and batch grinding tests were applied to three narrow size fractions below 3.35 mm. It was found that the breakage probabilities of coarse sizes and breakage rates in fine sizes were higher in the HPGR product. This indicated that clinker broken by HPGR contained weaker particles due to cracks and damage imparted. However, no significant weakening was observed for the -19.0+12.7 mm HPGR product. Although HPGR product was found to be weaker than HPGR feed, fragment size distribution of HPGR product did not seem to be finer than that of the HPGR feed at a given loading condition in either the drop weight test or batch grinding test. Also, drop weight tests on HPGR product and HPGR feed showed that the breakage distribution functions of coarse sizes depended on particle size and impact energy (J).
Batch grinding tests showed that the specific breakage rates of HPGR product and HPGR feed were non-linear which could be represented with a fast initial breakage rate and a subsequent slow breakage rate. The fast breakage rates of each size fraction of HPGR product were higher than HPGR feed due to cracks induced in clinker by HPGR. However, subsequent slow breakage rates of HPGR product were close to those of HPGR feed due to elimination of cracks and disappearance of weaker particles. Besides, the variation in breakage rates of HPGR product and HPGR feed with ball size and particle size also showed an abnormal breakage zone where ball sizes were insufficient to effectively fracture the coarse particles. Breakage distribution functions of fine sizes of HPGR product and HPGR feed were non-normalizable and depended on particle size to be ground. However, batch grinding of -2.36+1.7 mm and -1.7+1.18 mm HPGR feed yielded the same breakage pattern.
43
Mestres, Ricard Sola. "Greener approaches for chemical synthesis : ball mill and microwave assisted synthesis of fluoxetine and duloxetine and enantioselective catalysed addition of organometallic reagents to aldehydes." Thesis, Manchester Metropolitan University, 2017. http://e-space.mmu.ac.uk/618791/.
Full textAbstract:
This PhD thesis focuses on the development of “greener” synthetic methodologies in organic synthesis. Turning chemical production into a more sustainable industry - by reducing the waste generated and the electricity consumption - is highly desired in a world with limited resources and increasing population. This thesis, in particular, focuses on three of the ‘12 Principles of Green Chemistry’, reducing the amount of solvent and energy consumption in a chemical process, and the use of catalytic reagents instead of stoichiometric. In the first chapter of this thesis, a greener synthetic route for the preparation of the antidepressant fluoxetine (Prozac) was developed. The use of ball milling allowed a decrease of the solvent used in the process, furthermore, microwave assisted heating provided a more efficient method compared to the traditional heating using an oil bath. Fluoxetine was synthesised with 47% yield through two different synthetic routes (3 and 4 steps respectively). In addition, the scope of the developed methodologies was tested by the attempted synthesis of the antidepressant duloxetine. The second chapter of this thesis focuses on the catalytic enantioselective synthesis of chiral alcohols. More specifically, two different methodologies for the catalytic enantioselective addition of organolithium reagents to aldehydes were successfully developed, achieving excellent yields and enantioselectivities. Furthermore, a new methodology for the use of organozirconium reagents as nucleophiles in the catalytic enantioselective 1,2-addition of alkenes to aldehydes was also developed. Last, the implementation of a catalytic enantioselective step to the previous syntheses of fluoxetine was attempted.
44
ZOU, YU. "USE OF PYROLYZED SOYBEAN HULLS AS ECO-FRIENDLY REINFORCEMENTFILLER IN STYRENE BUTADIENE RUBBER." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1563924572380389.
Full text
45
Brancaz, Maud-Virginie. "Analyse cellulaire et moléculaire de la mutation "bald Mill Hill" (hr rhbmh) au cours du développement chez la souris." Université Joseph Fourier (Grenoble), 2004. http://www.theses.fr/2004GRE10097.
Full textAbstract:
Le gène hairless de la souris est la cible de nombreuses mutations alléliques, qui se traduisent par la désintégration des follicules pileux aboutisant à une perte progressive et définitive des poils 2 à 3 semaines après la naissance. Les lignées mutantes de souris hairless ont été intensément utilisées pour étudier divers aspects de la physiologie de la peau et l'effet de médicaments sur les structures tégumentaires. Cependant le gène hairless lui-même n'a été cloné qu'en 1994 et le domaine de recherche sur ses différents variants alléliques est devenu particulièrement dynamique depuis l'homologue de ce gène a été identifié chez l'Homme. Ce travail de thèse avait pour objectif d'analyser les mécanismes cellulaires et moléculaires d'une nouvelle mutation du gène hairless-hairless rhino bald mill hill (hrrhbmh) afin d'élucider le rôle de la protéine Hairless comme un corépresseur des récepteurs nucléaires d'hormone et d'aborder la signification de la localisation cellulaire de la protéine. Au cours de cette analyse, nous avons essayé d'identifier des interactions précoces du gêne hairless avec des gènes sélecteurs de la famille Hox, des membres des grandes voies de signalisation intercellulaire ou encore avec des facteurs de transcription impliqués dans les étapes initiales de la formation des primordia folliculairesIt is well documented that the mammalian hairless gene plays a critical role in the maintenance of hair growth. The hairless mutant ph enotype is characterised by a progressive and definitive hair loss. Although the hr gene has been known for many years, the biochemical function of the encoded Hairless (Hr) remains unclear. Hr encodes a putative zinc finger protein of approximately 127 kDa acting as a corepressor of nuclear hormone receptors. It interacts with histone deacetylases (HDACs) and is localized in the nuclear Matrix-Associated Deacetylase (MAD) bodies. Allelic mutations in the murine hairless gene, which arose spontaneoulsy in a colony at the National Institute for Medical research (NIMR), Mill Hill, London in early 1998. The gene symbol hr rhbmh mice revealed a substantial deletion at the 3'-end of the gen. Our results indicate that the transcription of the gene is surprisingly unaffected by the deletion. Instead it results in ablation of the determination codon leading to a new protein. This protein encompasses a 117 amino acids extension at its C-terminal part and presents an abnormal cellular localization. In an attempt to identify partners and targets of the hairless gene, we have analysed a series of markers of hair follicle and epidermal development in these mutant mice
46
Sun, Weicheng. "Use of Torrefied Sorghum as Eco-friendly Filler in Styrene Butadiene Rubber." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1527786418607651.
Full text
47
Folco, Eric. "Analyse de la régulation du gène hairless et identification des voies de signalisation affectées chez les mutants « Bald Mill Hill »." Grenoble 1, 2008. http://www.theses.fr/2008GRE10013.
Full textAbstract:
Le gène hairless (Hr) des Mammifères code pour un facteur nucléaire qui est fortement exprimé dans la peau et qui semble contrôler le cycle de renouvellement du follicule pileux. En l'absence de la protéine Hairless (HR) normale et fonctionnelle, le bulbe du poil subit une apoptose précoce liée à la perte totale et irréversible de pelage. Le phénotype hairless serait donc associé à une prolifération défectueuse des cellules souches dl follicule pileux et leur incapacité à migrer et répondre aux multiples signalisations qui régissent leur destinée. La protéine HR est localisée dans le noyau, étroitement liée à la matrice nucléaire et par son association aux facteurs de remodelage de la chromatine, fonctionne comme un corépresseur de récepteurs nucléaires d'hormones. Dans la peau, mais probablement dans d'autres organes, le répresseur HR est responsable de la dynamique dans la différenciation des cellules de la couche basale de l'épiderme et de l'identité des cellules souches du tégument. A l'heure actuelle, la régulation de l'expression gène Hr dans l'espace et dans le temps n'est pas élucidée et les partenaires de la protéine HR restent élusifs. Les objectifs majeurs de cette thèse étaient de mieux comprendre aussi bien les bases moléculaires de la régulation du gène Hr que la façon dont la protéine HR serait impliquée dans les grandes voies de signalisation qui gouvernent l'homéostasie de la peau et du follicule pileux. La première partie de cette thèse est ainsi centrée sur l'identification des éléments en cis qui gouvernent la régulation et la fonction du promoteur basal du gène Hr de la souris. Le site précis d'initiation de la transcription a été déterminé et un nouvel élément en cis de 1,1 kl (RE1) capable d'activer la transcription dans des lignées cellulaires d'origine neurale et cutanée, a été identifié. Grâce à une analyse par délétion et exploration fonctionnelle, il a été montré que le rôle de ce fragment est lié à la présence de sites de fixation de TR (TRE) et VDR (VDRE). De plus, un nouveau motif régulateur de 60 pb (UE60), capable d'interagir avec TRE et VDRE a été défini. Ces données suggèrent l'existence d'un réseau moléculaire complexe qui pourrait lier plusieurs voies de signalisation, responsables de la formation du follicule pileux et mettent en relief l'importance de l'organisation des modules régulateurs au niveau du locus hairless des Mammifères. Une grande partie du travail de thèse aété consacrée au décryptage des voies de signalisation qui impliquent la protéine HR dans le contrôle du cycle pilaire. La lignéE de souris mutantes bald Mill Hill (bmh), récemment décrite a été utilisé comme modèle pour aborder la signalisation par la vitamine D. Il a été montré que la protéine mutante HR bmh, localisée de façon aberrante dans le cytoplasme, pouvait interagir avec VDR, mais était incapable de réprimer l'activation de la transcription assurée par l'intermédiaire de VDR. Des analyses par immunofluorescence ont également montré que la protéine HR bmh présentait une localisation cytoplasmique anormale pas seulement en transfection transitoire, mais aussi dans l'épiderme et le follicule pileux des souris mutantes bmh. Enfin, les profils de localisation extra-nucléaire de la protéine HR bmh ont été abordés. Il a été établi que dans le cytoplasme HR bmh co-localise spécifiquement avec HDAC6 et est capable, de se lier physiquement à cette protéine. L'association de HR bmh avec une composante des complexes à ubiquitine, ainsi que sa localisation dans des endosomes tardifs et des Iysosmes suggèrent que la voie endosomale et la dégradation protéique par le protéasome pourraient moduler le phénotype cutané du mutant bmhLn Mammals, the gene hairless (Hr) encodes a nuclear factor strongly expressed in skin and crucial in controlling hair follicle integrity and cycling. Ln the absence of a normal and functional Hairless protein, the hai bulb undergoes premature apoptosis linked to complete and irreversible loss of hair follicles. The hairless phenotype is caused by defective proliferation and migration of the hair follicle stem cells, apparently unable t, respond to various signalling molecules. The HR protein is localised in cell nuclei, tightly bound to nuclear matrix and functions as a corepressor for nuclear hormone receptors by its association to chromatin remodelling factors. At least in the skin, but probably in other organs, the HR repressor seems to be responsible for the timing of epithelial cells differentiation and tegument stem cells identity. The spatial and temporal Hr gene regulation is still poorly understood and the partners of HR protein await to be identified. Th, main objectives of the thesis were therefore to shed more light on the molecular basis underlying Hr gene function as weil as on the HR protein implication in signalling pathways responsible for skin and hair follicle homeostasis. The first part of this thesis is thus focused on the fine mapping of cis-elements governing Hr gene basal promoter function and regulation. The precise transcriptional initiation start site of the mouse Hr gene was determined and a new 1,1 kb cis-control element (RE1) able to drive reporter expression in skin an brain derived celllines was identified. A deletion analysis and functional exploration have shown that the role of this upstream region is linked to the presence of TR and VDR binding sites. Ln addition, a novel cis¬ reaulatorv motif UE60, likelv to interact with both TRE and VDRE was defined. Taken together these findings reveal a complex molecular network that potentially links several signalling pathways in hair follicle formation and stress the importance of the organisation of the regulatory modules at the Hr locus in Mammals. A substantial part of the thesis work is dedicated to unravelling the signalling pathways where the Hr gene and the HR protein play a crucial role to control the hair cycle itself. A recently described mouse mutation-hairless rhino bald Mill Hill, (H('1bmh), was used here as a model system to approach interactions with the vitamin 0 signalling. It was demonstrated that the mutant HR bmh protein, although abnormally localised in the cytoplasm, is able to interact with the vitamin 0 receptor, but is not able to repress VDR-mediated transactivation. Immunofluorescence analysis revealed that HRbmh protein displays an abnormal cellular localization in transfected ceillines, as weil as in the epidermis and hair follicle of bmh mutant mice. Finally, the patterns of HRbmh protein extra-nuclear localization were analysed in cell transfection experiments. It wa established that HR bmh co-Iocalizes specifically with the protein HDAC6, in the cytoplasm and is able to physically interact with il. The association of HR bmh with this Ub-binding protein as weil as its localisation in late endosomes and lysosomes suggest that endosomal processing and/or proteasome related pathways miaht be able to shaoe and modulate the soecific skin ohenotvoe of bmh mouse hairless mutants
48
ALBERA, FABIEN. "La modelisation du broyage en mineralurgie : inventaire des modeles developpes, confrontation avec les performances d'installations reelles, criteres de selection." Orléans, 1987. http://www.theses.fr/1987ORLE2023.
Full text
49
Al-Salloum, Mohammed Y. "Use of Pyrolyzed Soybean Hulls as Filler in Polyamide-6." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1626793395861062.
Full text
50
Dvořáček, Jan. "Analýza silového zatížení řezného nástroje při pětiosém frézování." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228829.
Full textAbstract:
The diploma thesis is focused on machining using the ball-end shank mill. Content of the preliminary part of the work is a shank mill characteristic and a consequent part shows a splitting of ball-end milling cutters, its application, the cutting tool geometry and a characteristic signs of machining. The cutting force model of the ball-end mill is presented as well. A part of proposed model is the conversion of the resultant force too. Practical part is aimed at cutting force analysis of the ball-end mill and the main purpose of this part is a quantification of the cutting force for different work piece tilt angles while milling is performed.