Browsing by Author "Rathilal, Sudesh."

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Investigation of the effects of the process and equipment parameters on the separation efficiency of a vibrating plate extractor.
(2012) Naidoo, Pavanisha.; Carsky, Milan.; Rathilal, Sudesh.
In the industrial world where many different types of separation processes are available, liquid-liquid extraction is gaining increasing attention, since it offers many advantages over distillation especially for heat sensitive and azeotropic compounds. Liquid-liquid extraction is an essential separation method that applies to the chemical, petroleum, metallurgy, biotechnology, nuclear and waste management related industries. This separation technique also offers potential means of saving energy, thus making extraction a more economical separation process. The effectiveness of a vibrating plate extractor was previously investigated however limited research was conducted on the effect of tray spacing, solvent-to-feed ratio and agitation level on a vibrating plate extraction column. These parameters affect the hydrodynamics and mass transfer in a vibrating plate extraction column therefore the determination of the optimum process parameters is important in achieving the highest efficiency for the column and this is sought after for a vibrating plate extractor. A toluene-acetone-water system was selected for experimental work to be conducted on the vibrating plate extraction column. This test system for liquid-liquid extraction is a standard system proposed by the European Federation of Chemical Engineering. The research aimed at testing the effect of tray spacing, agitation level (product of amplitude and frequency of vibration), and the ratio of flow rates of the phases on the number of stages in order to optimise the efficiency of a vibrating plate extraction column. For the hydrodynamic experiments the dispersed phase holdup, drop size distribution and Sauter mean diameter were evaluated for varying parameters. For the mass transfer experiments the percentage acetone extracted, number of equilibrium stages, mass transfer coefficient and overall efficiency were determined as well as the dispersed phase holdup, drop size distribution and the Sauter mean diameter for varying parameters. A decrease in the holdup occurred for an increase in the solvent-to-feed ratio and an increase in the agitation level resulted in a decrease in the Sauter mean diameter. Results indicated that lower tray spacing resulted in a higher extraction of acetone. Backmixing in the dispersed phase resulted in higher number of stages.
Modelling of a vibrating-plate extraction column.
(2010) Rathilal, Sudesh.; Carsky, Milan.
Liquid extraction, sometimes called solvent extraction, is the separation of the constituents of a liquid solution by contact with another insoluble liquid. It belongs to the class of countercurrent diffusional separation processes, where it ranks second in importance to distillation. There are many different types of columns that are available for liquid-liquid extraction and the reciprocating column (RPC) and vibrating plate column (VPE) are two types of mechanically aided columns. This research aims at developing a mathematical model for the prediction of NTUIHETS and the mass transfer coefficient, k-ox for the VPE based on the agitation level of the plates (af- the product of frequency and amplitude of the plate motion), the plate spacing and the flow rates which will allow for the simplification in the design of this type of column. There is a lot of research that has gone into the development of mechanically aided extraction columns but it is limited when it comes to the RPC and VPE and most of this research is devoted to the RPC. The system chosen is the acetone-toluene-water system with the acetone in toluene forming the feed that is dispersed in the column as it moves upward while the water moves as a continuous phase down the column. Experiments were conducted to evaluate the hydrodynamics of the droplets moving up the column (in terms of drop sizes, size distribution and dispersed phase holdup) and to evaluate the mass transfer that occurs (in order to evaluate NTU, HTU and k-ox) as well as the effect of mass transfer on the hydrodynamics of the system while varying the agitation levels and spacing of the plates in the column. Successful models were developed using some of the experimental data and these correlations were verified with additional data.
The study of the mechanism of magnetic water treatment for the prevention of scale and corrosion.
(2004) Rathilal, Sudesh.; Carsky, Milan.; Dunlevey, John N.
Scaling and corrosion cost industries all over the world millions of rands each year. Chemical treatment of water to prevent scale is expensive and can be hazardous. As a result industry is always looking for new, cheaper alternate methods of reducing scale. One such method is magnetic water treatment. Magnetic water treatment involves passing hard water (the main cause of scale) through a magnetic field. This method favors the precipitation of calcium carbonate in the form of aragonite instead of calcite. Aragonite is a softer, less tenacious material that does not adhere to the walls of pipes or heating surfaces. These particles remain in suspension and may settle out somewhere along the system where the velocity of the water has been reduced. A simple bench-top heating system was set up to determine whether magnetic treatment works and, if it does, to determine the optimum conditions under which it operates. A saturated solution of calcium carbonate was circulated through the heating system with, and without the magnets, so that comparisons could be made. The precipitate was analysed (via X-ray diffraction) to calculate the proportions of calcite and aragonite, while atomic absorption was used to test the hardness of the filtrate. This gave an indication of the effectiveness of the magnetic system. pH graphs and absorption graphs were plotted to compare the rates of precipitation. The precipitate was also observed under the electron microscope in order to view the different structures of calcite and aragonite. Experiments were carried out at different temperatures and different flow rates in order to test the effect of these parameters on the magnetic system. Results showed that the magnetic field increased the rate of precipitation and caused aragonite rather than calcite to be formed. This was in contradiction with most literature surveyed, which stated that magnetism increased the dissolution of calcium carbonate. Results indicated that the higher the temperature, the greater was the rate of precipitation and as a result, the greater the amount of aragonite formed, even without the magnets. Increased flow rate also increased the amount of aragonite formed. As a result hereof, conclusive results could not be obtained at high temperatures and high flow rates.