Browsing by Author "Rohitha, L.P.S."

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    Enhancing the Graphite Froth Flotation Yield
    (Uva Wellassa University of Sri Lanka, 2012) Kumara, M.G.S.W.; Rohitha, L.P.S.
    The vein graphite deposits of Sri Lanka are located in a Precambrian high grade metamorphic terrain dominated by granulite facies rocks. In Sri Lanka Graphite is mainly extracted through underground mining located at Bogala, Kahatagaha and Kolongaha. At the Bogala graphite mine, the Graphite veins are mix with rocks of the granulite and almandine amphibolite metamorphic facies (Cooray, 1984). Graphite has been categorized in industry according to the amount of graphite carbon content. During the present study, graphite having a 82-85% C of Tub-dust, with a low market, has been upgraded to carbon 99+% grade by using flotation that is one such method widely used in the graphite industry. Therefore, high quality graphite is made by the froth flotation process in industrially. The flotation process has been used in the world widely coal, Graphite, Sulpher, Nickel, iron ore, platinum ore, gold industries to upgrade and extract the minerals. Basically, Froth flotation process is physico-chemical separation method (Barry and Napier-Munn, 1989) However, the purity of ore part has been decreased with time of mining in the word. Because of that, mineral consumption is very higher in the world. Hence, the low grade minerals like nonsulfide metallic minerals, industrial minerals, Coal and Graphite want upgrade and separate as high grade minerals in industrially (Kelly and Spottiswood, 1989). Efficiency of Froth Flotation process should be increased by changingits effective parameters and different physical properties of particles of various minerals for the modern mining and processing industry to produce economically profitable products. In this research, we have made use of local graphite having 85% C grade as the starting point. Air fl ow rate control the correct float time, particle size and RPM value, pH, right flotation time are some of the identified variables and effective flow sheet for Graphite flotation plant used in this research
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    Increasing the Purity of Graphite Samples Taken from the Under Flow of the Froth Flotation Process Using a Gravity Separation Method
    (Uva Wellassa University of Sri Lanka, 2018) Ulukkulama, G.V.B.; Jaliya, R.C.G.; Rohitha, L.P.S.
    Graphite is the one of the main exporting mineral commodities in Sri Lanka which is found as flake graphite, vein graphite and, amorphous graphite. Kahatagaha, Bogala and Ragedara mines produce world's best quality graphite with a Carbon grade over 90%. Quartz, pyrite, chalcopyrite, feldspar, calcite etc. are the associated trace minerals with the graphite. Froth flotation is one of physio-chemical separation technique. Nevertheless, it cannot be considered as an eco-friendly and a cost-effective method, since chemicals used for froth flotation of graphite are toxic and expensive. Moreover, froth flotation does not provide the optimum separation and about 37% of graphite get mixed with the underflow. In this research Humphrey Spiral was used as the gravity separation technique to process the under flow taken from froth flotation. Flow rates, splitter distances and particle sizes were taken as the parameters. Particle size of the sample tested were from 50-500 pm. The results concluded that under the flow, graphite can be processed up to 80% or higher grade from an initial grade of 37.89% with flow rate of 888 ml splitter distance at position 3 and for particle size between 300-500 pm. To obtain the optimum grade, particle size distribution, percentages of mineral in relation to the particular particle size should be studied and suitable flow rate chose accordingly. Further, splitter distance should be narrowed down the area of tailing conduit to attain an optimum grade. Keywords: Graphite, Graphite Processing, Gravity Separation, Spiral
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    Removal of Iron Impurity from Vein Quartz by Acid Leaching
    (Uva Wellassa University of Sri Lanka, 2018) Wijerathne, A.G.N.C.S.; Jaliya, R.G.C.; Rohitha, L.P.S.
    Vein quartz is the major source of silicon for manufacturing of solar cells, computer chips, and silicon carbide. Nevertheless, high-tech applications of vein quartz do not apply in industries due to iron impurities that is the major problem in the quartz processing industries in Sri Lanka. The aim of the investigation was to enhance the purity of exporting semi processed vein quartz by acid leaching. Particle size reduction processes crushing, grinding and milling increase the amount of iron in the quartz and this secondary iron concentration needs to be removed to produce more purified quartz. Thus, in this research quartz was obtained using raw quartz near Badulla area. Raw quartz was processed using primary and secondary crushers and then it was separated into four size fractions (125 rtm, 500 rim, 1 mm, and 8 mm). The acid leaching was employed for iron removal. Atomic Absorption Spectrophotometer (AAS) was used to measure iron content before and after the leaching. As preliminary studies, Hydrochloric acid and Nitric acids were employed for the leaching and Liquid-Solid ratio was 5:1. According to the results which were observed as preliminary study, HCl was chosen for the leaching and effect of the HC1 for the removal of iron was examined. The particle size of the quartz, leaching time, concentration of the reagents were used as parameters. Leaching was done under normal atmospheric conditions (25 °C, 1 atm). The acid leaching of vein quartz resulted in a reduction of 60 — 65% Iron from the original natural state. Since iron dissolution is a photochemical reaction experiment was conducted in controlled conditions (250 — 500 lux). A progressive amount of leaching (60 — 65%) of iron from quartz was obtained under following conditions, a higher concentration of HC1 (5M), smallest size fraction (0-125 rtm), and 60 hrs. leaching time. Under these conditions, a higher purity of quartz powder can be achieved. Key Words: Quartz, Leaching, Quartz impurity removal