Modelling scour around submerged objects with TELEMAC3D - GAIA

Hydrodynamic

Online proceedings of the papers submitted to the 2020 TELEMAC-MASCARET User Conference October 2020

Hydrodynamic

Master of Science

thesisDespite their many uses, fine clay particles such as kaolinite are a nuisance in management of tailings in various industries such as the oil sands and phosphate processing industry. The effective flocculation, sedimentation, and consolidation of these fine particles are a major challenge. In industries, polymers are added to tailings suspension to facilitate formation and eventual sedimentation of flocs. The structure of floc and the water entrapped within the floc determine floc behavior and settling characteristics. The quantification of water entrapped within the kaolinite flocs has not been reported before. The information on kaolinite floc size and shape is also limited due to the challenges in experimental procedures for these delicate structures. In this thesis research, operating conditions for kaolinite flocculation were determined and a suitable polymer was chosen by settling experiments. Further investigation of the floc formed was done in suspended state as well as in sedimented state. The flocs were analyzed for their size, shape, water content, and microstructure. A pool of analytical techniques like the Particle Vision & Measurement (PVM), Dynamic Image Analysis (DIA), Scanning Electron Microscopy (SEM), High Resolution X-ray Microtomography (HRXMT), and image processing software like Fiji, Medical Image Processing Analysis & Visualization (MIPAV), and Drishti were used. The analysis of suspended flocs by PVM and DIA revealed a mean floc size of about 225 µm for high molecular weight, 5% anionic polyacrylamide-induced flocs. The low molecular weight, 70% cationic polymer-induced flocs were found to be smaller in size (145 µm). DIA was used to analyze the flocs at different solid concentration. It was found that the increase in solid concentration leads to increase in floc size. Floc circularity was also analyzed by using both these methods. Most flocs were irregular in shape with circularity ranging between 0.2-0.3. However, the circularity results from both these methods do not agree well due to the difference in methods of detection and different definitions used for circularity/sphericity. Major contribution of this thesis work includes development of a new technique for water content and size analysis of sedimented kaolinite flocs. The sediment bed was segmented into about 13 thousand individual flocs and each floc was analyzed for its size and water content. The results suggest a normal distribution of water content for these flocs, with mean water content of 53.9% and standard deviation of 11.8%. About 98% of the flocs have water content in the range 30-80%. The size analysis revealed that about 90% of the flocs are less than 1.5 mm in size. The water content was found to decrease with increase in size of the floc. The flocs were found to be fairly irregular, with sphericity values around 0.1. The floc shape analysis was also done but limited to 10 flocs. In addition to macroscopic analysis of individual flocs, flocs were also analyzed for their microstructure. Visualization of floc microstructure and polymer chain was done with the help of SEM. Microstructures of up to 10 µm in size were revealed along with the web formed by polymer chain

Green Low-Carbon Technology for Metalliferous Minerals

Metalliferous minerals play a central role in the global economy. They will continue to provide the raw materials we need for industrial processes. Significant challenges will likely emerge if the climate-driven green and low-carbon development transition of metalliferous mineral exploitation is not managed responsibly and sustainably. Green low-carbon technology is vital to promote the development of metalliferous mineral resources shifting from extensive and destructive mining to clean and energy-saving mining in future decades. Global mining scientists and engineers have conducted a lot of research in related fields, such as green mining, ecological mining, energy-saving mining, and mining solid waste recycling, and have achieved a great deal of innovative progress and achievements. This Special Issue intends to collect the latest developments in the green low-carbon mining field, written by well-known researchers who have contributed to the innovation of new technologies, process optimization methods, or energy-saving techniques in metalliferous minerals development

Dynamic simulation of red mud washers used in aluminum industries

Clarifier-Thickener equipment is used in a wide range of continuous sedimentation and sludge thickening processes where solid particles from continuous inflow mixtures are separated from the liquid. In this operation, the concentration of solids increases due to settling, so that the formation of a thicker bed is inevitable with time. Under optimal operating conditions, it is always possible to obtain two discharges from these vessels: a highly concentrated suspension at the bottom (underflow), and a clarified liquid stream at the top of the equipment (overflow or effluent). In the Bayer Process an insoluble sub-product is formed as a result of the digestion of the bauxite ore with caustic soda. This product is called “red mud” and it has to be continuously removed by settlers or thickeners/clarifiers. This project proposes the simulation of a continuous thickener/clarifier in order to predict the concentration profile and the height of the mud level (process controlled variable) as alternative to current measurement system, that contains long delay discrete sampling time(15 minutes each measurement). The simulation also, can provide an option of creating a knowledge base for off-line control. The project essentially involves two methods of simulation, namely mathematical modelling and neural networks. The model based applies a kinematic model to approximate the process behaviour using both, equipment and suspension characteristics. On the other hand, due to the large amount of historical data, neural network is proposed for system identification. The first method is based on the solution of a highly nonlinear model, based on kinematic modelling of sedimentation extended to flocculated suspensions. This approach uses a conservative finite difference scheme of the upwind type for solving an initial boundary value problem (IBVP). The successful simulation of the equipment and further validation of the mathematical model are then achieved once the properties of the suspensions have been determined. These properties are related to flux batch settling and solid stress functions, whose parameters can be obtained experimentally.On-site testing of the characteristics of red mud was conducted at the Rio Tinto Yarwum Alumina Refinery in Queensland. The settling properties of the suspension were determined via batch settling. For measurement of the rheology properties, the vane technique was used employing a Haake VT 550 rheometer. The results of the simulation showed that the concentration profile and height of the heavy mud level can be determined via a steady state model for a given underflow concentration. These results, however, were not in good agreement with measured data. The second method of simulation involved the use of Rio Tinto Yarwun historical data to develop a neural model in order to obtain a relationship between process variables. This approach has the advantage that no mathematical model is needed. With this method, historical data (continuous data) are obtained and analysed, and daily averages of the variables involved in the process are calculated. Different network architectures are tested according to the washer process. Ultimately, two networks were developed to describe washer dynamics.

Proceedings of the XXVIIIth TELEMAC User Conference 18-19 October 2022

Hydrodynamic

XVIII International Coal Preparation Congress

Changes in economic and market conditions of mineral raw materials in recent years have greatly increased demands on the ef fi ciency of mining production. This is certainly true of the coal industry. World coal consumption is growing faster than other types of fuel and in the past year it exceeded 7.6 billion tons. Coal extraction and processing technology are continuously evolving, becoming more economical and environmentally friendly. “ Clean coal ” technology is becoming increasingly popular. Coal chemistry, production of new materials and pharmacology are now added to the traditional use areas — power industry and metallurgy. The leading role in the development of new areas of coal use belongs to preparation technology and advanced coal processing. Hi-tech modern technology and the increasing interna- tional demand for its effectiveness and ef fi ciency put completely new goals for the University. Our main task is to develop a new generation of workforce capacity and research in line with global trends in the development of science and technology to address critical industry issues. Today Russia, like the rest of the world faces rapid and profound changes affecting all spheres of life. The de fi ning feature of modern era has been a rapid development of high technology, intellectual capital being its main asset and resource. The dynamics of scienti fi c and technological development requires acti- vation of University research activities. The University must be a generator of ideas to meet the needs of the economy and national development. Due to the high intellectual potential, University expert mission becomes more and more called for and is capable of providing professional assessment and building science-based predictions in various fi elds. Coal industry, as well as the whole fuel and energy sector of the global economy is growing fast. Global multinational energy companies are less likely to be under state in fl uence and will soon become the main mechanism for the rapid spread of technologies based on new knowledge. Mineral resources will have an even greater impact on the stability of the economies of many countries. Current progress in the technology of coal-based gas synthesis is not just a change in the traditional energy markets, but the emergence of new products of direct consumption, obtained from coal, such as synthetic fuels, chemicals and agrochemical products. All this requires a revision of the value of coal in the modern world economy

Development of Advanced Control for Paste Thickeners

A paste thickener produces underflow with a high solids concentration by removing water from a dilute suspension. Paste thickening technology has been gradually gaining acceptance in the mining industry. Some of the main challenges in thickening are the complex dynamics due to severe interactions between operating parameters and the existence of a large range of process time constants. Additionally, being a downstream process, paste thickeners suffer from fluctuating feed conditions from upstream processes. Furthermore, the operation of paste thickeners involves a tight operating window as the underflow properties are sensitive to small changes in concentration. The above challenges motivate this work to develop a systematic advanced control strategy, in particular, model predictive control (MPC) to effectively and efficiently regulate this complex, multivariable process. In this thesis, the sedimentation-consolidation model is adopted and analysed to identify important dynamical features and the key process parameter which will be considered in control system design. The model is then validated using industrial plant data. An extended Kalman filter is developed to estimate in real-time the key process parameter which affects thickening dynamics significantly. Through extensive simulation studies, it has been demonstrated that the proposed MPC approach can deliver a higher underflow solids concentration and a better regulated underflow removal rate. In addition to the basic MPC, several important extensions are developed based on three practical considerations. Firstly, it is illustrated that incorporating ``future'' time-varying constraints in the MPC can help deal with the control difficulty arising from the co-disposal of underflow and coarse reject, leading to improved control performance. Secondly, an MPC with a non-uniformly spaced optimisation horizon is proposed to deal with the timescale multiplicity of thickening. The proposed approach provides similar levels of performance as compared to a conventional MPC with the advantage of reduced computational complexity. A stability ensuring condition for the proposed MPC is also developed. Thirdly, an MPC is developed to control both underflow solids concentration and rake torque. The nonlinear rake torque control problem is converted into a linear MPC problem, reducing the computational complexity of the optimisation problem. Simulation studies have shown that the proposed approach can effectively control the underflow solids concentration while minimising the rake torque, potentially preventing serious operational problems such as underflow blockage