1. The effect of pH on flotation has been shown. 2. The establishment of a good colourimetric analysis for the collector has been achieved. 3. The amount of adsorption of the collector has been shown. 4. The absence of Bromide on the silica surface has been shown which seems to indicate a metathetic reaction has occurred. 5. A very approximate calculation of the adsorption of T. M. C. A. B. per square cm. has been given. / Science, Faculty of / Chemistry, Department of / Graduate

M.Ing. ( Civil Engineering) / The use of dissolved-air flotation has shown a marked increase in the past decade. The practise is however still relatively unknown, and plants are still being constructed using empirical guidelines. Probably the most important aspect that should be highlighted, is the successful generating of microbubbles in the flotation tank. The microbubbles are generated when the saturator water pressure is released via a reduction nozzle. These bubbles should be homogeneous, and in the region of 100 /Lm in diameter. If these bubbles are too big, they will rise too fast, and disturb the float layer. If they rise too slowly, the retention time would be too long. The purpose of this work was to try to refine nozzle design to such a level that microbubbles can be generated with chosen size and size.distribution. Very little is however done at this stage to understand the design of nozzles. The result of this lack of knowledge, is that many flotation plants fail because of ineffective nozzles and nozzle design. Before experimenting could be started, it was necessary to acquire a better understanding of the fundamental behaviour of bubbles. A large amount of literature is available on this subject, but very little is specifically for dissolved-air flotation. It was attempted to give an overview of all the relevant literature regarding bubbles and their behaviour. Further insight is also given regarding the generation of bubbles in relation to physical parameters such as temperature and pressure. A short summary is also given of all the most commonly used commercially available nozzles, together with simple section drawings. The bubble size constitutes the most important parameter in this study, and therefore a purpose made flotation column was set up, that would simulate real life situations. Photographs were taken with different nozzle configurations, chosen such that they would contribute meaningfully to the experimental results. The complete experimental setup and procedures are discussed extensively in the document. The results of the study led to the formulation a bubble growth model to explain the behaviour of bubbles resulting from these nozzles. The use of this model, together with a couple of other assumptions, spread new light on the generation of microbubbles. This newly found information could lead to the development of a rational design procedure for injection nozzles for the production of microbubbles.

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Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

Thesis (Ph.D.) - University of Queensland, 2006. / Includes bibliography.

Expert systems technology is a discipline of artificial intelligence that has recently emerged from the research environment and is currently making significant inroads into business and industry. The proponents of expert systems make many attractive claims. Two of the claims are that expert systems can capture the knowledge of the experts and can be programmed by non-programmers. To date, most uses of this technology in the process industry are in off-line applications, that is, applications that are not directly tied to operating environments. Moreover, those that are used in on-line environments are used as advisors and only suggest changes, human operators are required to close-the-loop to the process. This technology should be applicable to operating environments and should the claims of its proponents be valid, then it should also be better than existing tools currently in use. In an operating environment it could use the knowledge of experienced operators as an intelligent controller and apply it directly to a process without the intervention of human operators. In this thesis the prospect of using an expert system as an intelligent controller is investigated. The thesis offers background to expert systems, how expert systems are related to artificial intelligence and what the generic components of an expert system are. As a test of the technology an expert system was developed as an intelligent controller in a mineral processing application. The prototype expert system was developed as a supervisory controller in the copper flotation circuit in the concentrator at Brenda Mines Ltd.. The expert system operated on-line and controlled the process in real-time. It read sensor data and using the operating experience of Brenda's flotation operators, manipulated regulatory controller setpoints as deemed necessary. The expert system was able to manipulate directly reagent flowrates and process air flowrates. Also, it suggested changes to other process variables not directly under its control. The manipulated variables were collector and frother reagent flowrates, the air flowrate to a bank of scavenger flotation cells and the air flowrate to four flotation columns. The operators were allowed to, and sometimes required to, intervene in instances of large process upsets. Results of a month long trial period in the flotation circuit indicated the success of the application. The expert system was indeed able to maintain metallurgical performance at a level approximating that of the operating experts, however, no direct comparison between the performance of the circuit under expert system control, versus performance under operator control, was possible. A rudimentary comparison was made between the circuit's performance under expert system control and its historic performance. The results were favourable. A less tangible measure, though as important, were the attitudes of the operators toward the system. Almost unanimously, the operators felt the system eased the task of circuit operation and was responsible for better circuit performance. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

A new processing technique, centrifugal flotation, has been developed in recent research projects to overcome the large residence times and fine particle limitations of traditional flotation technologies. The major innovation in the area of centrifugal flotation is the Air Sparged Hydrocyclone (ASH), which has proven capabilities in achieving quality products at specific capacities greater than traditional flotation methods. However, the ASH technology ultimately suffers from sparger plugging problems. Therefore, three unique flotation cyclone designs were developed utilizing external sparging systems and control features to float fine coal. The objective of each design was to create a system that mimics the behavior of the ASH technology, while providing advantages in bubble generation and retention time requirements. The evaluation of the three designs provided evidence towards the development of an efficient centrifugal flotation technique. Evaluation of a flotation cyclone with an external Cavitation Tube yielded a single-stage product with an ash content of 4.41% and a 45% recovery rate in a retention time of 0.66 seconds. However, the system required 16 minutes to meet comparable flotation yields and recoveries. The third design achieved a multiple-stage product of 11.32% ash at a 55% recovery in 20 minutes. These two designs provided low yield, high grade products, but rejected a high percentage of hydrophobic particles and required high retention times to meet typical flotation standards. In addition, these designs suffered by requiring high frother concentrations and recovery could not be increased through increased aeration due to design limitations. / Master of Science

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