tinuous thickener from batch sedimentation experiments. It is significant that up Kynch () presented the first theory of sedimentation. In spite of the fact that. Points are experimental data, continuous curves Derived from Kynch theory (see text). Figure 5 Two Interface Description of Sedimentation. Instantaneous concentration profiles of the batch sedimentation of non-colloidal hard spheres were measured for various initial suspension concentrations from.
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UBC Theses and Dissertations. An understanding of sedimentation and consolidation of tailings provides a solid foundation for the management of tailings. Kynch theory, the first mathematical formulation of sedimentation theory, is widely used as a tool in the analysis of batch sedimentation.
However, due to various idealized assumptions within Kynch theory, the application of this theory to describe and analyze tailings sedimentation in the laboratory setting has not been well developed. For the purpose of this research, a new apparatus was designed and constructed to carry out column settling tests and to remove and collect samples of water and suspensions in thin layers.
Tests conducted with this apparatus aim at investigating the settling behavior and the internal changes in the suspension during the process of sedimentation. Solid content and particle size were selected as the main parameters. Benchmark tests were first conducted to determine the general range of the two parameters. The experimental data collected from these tests was analyzed with Kynch theory. Total copper tailings, with a large range of particle sizes could not satisfy the assumptions of Kynch theory on particle size, and failed to conform to Kynch theory.
In the tests of fines from copper tailings, the influence of segregation decreased as the coarse particles in the copper tailings were removed. Based on Kynch theory and some laboratory data, a prediction curve was iii developed and compared with the results of the column settling tests.
Changes in the internal attractive force, and the influence of compaction settling were found to be reasons why kyncb prediction curve was unable to kyncch match the experimental data. The design of the special made apparatus for the column settling test with sample collection was done primarily by myself. Experimental Apparatus and Methodology Features sedimentstion apparatus are labeled: Your input on my research has been of the greatest value.
I also want to express my sincere gratitude to Professor Dobroslav Znidarcic, University of Colorado, Boulder for his suggestions on the design of the experimental apparatus and Dr. Ali Hooshiar for his inspiration regarding the experimental methodology. I would like to thank Mathiew Estepho for his great help with my research. Their support played a significant role in both my research and for my graduate studies. I would also like to offer my gratitude to Aaron Hope, millwright of CMP laboratory, for his hard work on the construction of the experimental apparatus.
Wei He, Pius Lo, for their valuable suggestions on my research. Last but not least, I would like to thank my dear family and friends. Their love has helped and supported me during my time here at UBC. Copper ores typically contain 0. Over the last century, the production of tailings has rapidly increased as the demands for minerals and metals have grown and low-grade ores are increasingly being extracted.
Some mines are currently producing overtonnes of tailings per day. Tailings are generated during mineral processing in mills. Generally, tailings consist of ground rock, residual metal, water and chemical reagents that have been added during processing.
After tailings are produced, most of the tailings mass is normally discharged in a storage tailings pond known as a Tailings Management Facility TMF in the form of slurry Lottermoser, Tailings undergo sedimentation in or storage tailings pond. As shown in Figure 1. In addition to the formation of a sand beach and suspension, water is released as particles in the tailings settle, and it forms a layer of 2 supernatant water on top of the tailings. This can be discharged or recycled if the quality of the water meets a certain standard.
This liquid-solid separation is known as sedimentation. These properties include the solids content, void ratio, permeability, compressibility, and effective stress. After the sedimentation ends, the consolidation process begins, leading to a further change of solids content and an enhancement of the strength of the deposit. Thus, a better understanding of the sedimentation of tailings will benefit the management of tailings.
In order to gain further understanding regarding the process of sedimentation, column settling tests are employed in this research to learn about the settling behavior of tailings. This research consists of two components. The first involves an improved methodology through which to collect samples of sediment at different heights in the settling column during the settling test.
Kynch theory, the first mathematical formulation of sedimentation in history, is applied to give a theoretical evaluation of the results and analysis, and will serve as the second component of this research.
A new experiment apparatus was constructed to conduct column settling tests and column settling tests with sample collection. Kynch theory is analyzed and applied to predict various parameters of sedimentation. The following question was explored in this research: Some specific objectives of this research are: A brief summary for each chapter is provided as follows: In chapter 1, the general background for this research is presented.
Several objectives of this study are summarized. In chapter 2, a literature review of previous researches and studies related to the above topics is presented. Mechanism and types of sedimentation are discussed to provide a general idea of settling behavior, and some developments and applications of column settling tests are presented.
Kynch theory is discussed in detail. The continuity equation in Kynch theory and a calculation of the settling curve are all discussed in this chapter. Chapter 3 presents a description of the test samples of total tails and fines from copper tailings. The design and construction of a new experimental apparatus for column settling test with sample-collection endings is introduced. The new apparatus makes it possible for researchers to collect samples from the settling suspension at different heights.
Column settling tests on the total tails of copper tailings with different initial solids contents were conducted to determine the reasonable solids content for the latter test. Column settling tests and the column settling tests with sample-collection on copper tailings with different particle size ranges were conducted to investigate the influence of particle size on general settling behavior.
In chapter 4, results of column settling tests and the column settling tests with sample-collection are presented and analyzed to determine the applicability of Kynch theory for different materials. The results of particle size distribution analysis are discussed in order to investigate the 5 segregation phenomenon in column settling tests and the column settling tests with sample-collection. The calculation of the prediction settling curve was made based on Kynch theory and compared with the experimental data from column settling tests.
Tests were also conducted on fines of copper tailings with dispersant, kaolin and a mixture of kaolin and concrete sands. In chapter 5, the main achievements and important findings of this research are presented. Recommendations on how to improve the experimental apparatus and methodology, as well as recommendations for future studies are suggested. This phenomenon is widely observed in the formation of sedimentary rocks and associated ore deposits Chen, Settling of solids from the liquid phase is influences by various forces including gravity, electromagnetism, and centrifugal force, being applied to the particle Concha, The settling of particles from a suspension depends on both the characteristics and the concentration of the particles.
In low concentration suspensions, or dilute suspensions, the concentration of particles is too low to cause significant displacement of water as they settle. Based on these concepts, sedimentation can be classified into four types, which are shown in Table 2. Discrete particles in low concentration suspensions. Particles settle as individuals freely without significant interference from neighboring particles. Removes grit from wastewater 7 Type Description Application 3.
Acceleration of individual particles in water or other liquid stops when the drag forces on the particle is equal to the submerged weight. Particles forming flocs in low concentration suspensions.
Particles stick together in clumps while settling. Particle concentration is great enough that particles are so close and no longer settle individually 2. There is an upward flow of water or liquid. Water moves in space between particles. Occurs in secondary settling facilities Compression Settling 1. Compression settling occurs when Occurs in the lower 8 Type Description Application the concentration is very high and particles are actually in contact. It results in adjustment within the solid matrix.
Water or liquid is squeezed out of the mass. As mentioned above, particles in hindered settling do not settle individually. The settling velocity of a particle in hindered settling may be less than its final velocity in free settling conditions Richardson et al.
Course: I كلية الهندسة / الدراسة الصباحية / قسم الهندسة الكيمياوية/ المرحلة الرابعة / ظواهر انتقال
In kynfh settling, discrete settling and flocculent settling may also occur in addition to compaction settling Tchobanoglous et al. Coe and Clevenger identified the settling of an initially homogenous concentrated suspension with four well-distinguished settling zones by studying the sedimentation of metallurgical slimes.
The four zones are illustrated in Figure 2. Settling velocity can be measured directly in the settling column by column settling tests or can be estimated from the measurement of the particle size and density of the settling particles Wang et al. A conventional column settling test involves a column or a cylinder Palermo and Thackston, Settlement can be measured or observed directly inside the settling column or cylinder based on the time interval or the distance interval that the interface passes.
I كلية الهندسة / الدراسة الصباحية / قسم الهندسة الكيمياوية/ المرحلة الرابعة / ظواهر انتقال
The conventional column-settling test begins with a kyncn of the sample with solution to form suspension. After the sample has been fully dispersed, the suspension is decanted into the settling column or cylinder for sedimentation.
Hheory detailed procedure is introduced in chapter 3. However, more advanced apparatus were designed and built in order to learn about some of the internal physical characteristics of the behavior of sedimentation. Inat the University of Alberta Caughill,Caughill conducted a series of settling tests on some specially-made standpipes.
A theory of sedimentation – Transactions of the Faraday Society (RSC Publishing)
Most of the standpipe tests were carried out in PVC cylinders of 30 cm height. In addition, two settling tests were performed in two 2-m high standpipes. In the test, tailings mixed with other materials were allowed to settle undisturbed in the standpipes.