Browsing by Author "Pathirage, SS"

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item: Conference Full-text
Processing vein quartz in Badulla area to suit manufacturing chemically reinforced glasses
Pathirage, SS; Hemalal, PVA; Rohitha, LPS; Siriwardhana, YPS; Ratnayake, NP; Abeysinghe, AMKB; Dassanayake, ABN; Elakneswaran, Y
Chemically reinforced glass, commercially known as tempered glass has a high global demand with the rapid increase in the usage of touch-screen type mobile phones and tablets. To maintain a high quality and to enable improvements of these devices the resolution, clarity and durability of tempered glass has to be improved and therefore, the selection of quality raw silica for tempered glass has become critical. Sri Lanka is one of the main exporters of silica to the world market and currently, Sri Lankan supplies mainly consist of crushed and powdered bulk unprocessed raw material. In this background, it would be prudent to export semiprocessed quartz as raw material for chemically reinforced glass. The requirements for chemically reinforced glass is a minimum value of 99.8 %, SiO2 and the maximum impurity levels of 9 ppm of Fe2O3 and 350 ppm of Al2O3 with the size requirement being 75-300 microns. In this study, sources for the production of raw material for the production of chemically reinforced glass was investigated using various types of vein quartz originating from quarries situated at Badulla in Sri Lanka. Milky, Smokey, Transparent, Rose, Mica associated and Feldspar associated quartz obtained from 7 quarries were investigated. Samples were analyzed using Atomic Absorption Spectrophotometer (AAS) and Inductively Coupled Plasma (ICP) techniques for trace elements. Results of the chemical analysis showed a markedly low iron content with less than 15 ppm in transparent quartz, less than 25 ppm in milky quartz, less than 30 ppm in smokey quartz, less than 35 ppm in rose quartz, less than 30 ppm in mica associated quartz and less than 300 ppm in feldspar associated quartz. More than 700ppm of Al2O3 content was observed in feldspar associated quartz. Cr content in rose quartz was more than 700 ppb and more than 800 ppb in mica associated quartz. Smokey quartz showed a high Ni and Al2O3 contents. Milky and transparent quartz in the observed quarries showed the lowest trace element contents and their natural quality close to the requirements of chemically reinforced glass and SiO2 levels are higher than 99.8%. Further results obtained using an industrial scale pilot plant show a significant reduction of Fe content, less than 5 ppm occurring in milky quartz with size reduction carried out followed by magnetic separation and removal of fraction less than 75 micron. Processed transparent quartz and milky quartz in Badulla area can directly be exported as raw material for chemically reinforced glass.
item: Thesis-Full-text
Value addition to local vein quartz in producing industrial grade silica
Pathirage, SS; Rohitha, LPS; Ratnayake, NP
Applications of high-purity quartz as a raw material in high-tech industry are numerous. A few of them includes semiconductors, microchips, industrial integrated circuits, high temperature lamp tubing, optical fibers, chemically reinforced glass and solar silicon cells. Sri Lanka is rich in quartz mineralization with an abundance of major vein quartz deposits with purity levels over 99.5% of SiO2. Developing high-tech products requires considerable capital investment, expertise and advance processing technologies which are lacking in developing countries like Sri Lanka. Thus leading to export raw quartz with enforced size reduction of run-of quarry quartz in grit and powder forms to industrialized countries without further value addition. Therefore, an alternative approach is evaluated and recommended to achieve a higher level of value addition by exporting semi-processed and processed industry specific quartz raw material. Chemical composition of major types of vein quartz and mining activities of 7 vein quartz deposits and mass scale quartz processing at a plant located in Badulla district of Uva Province, Sri Lanka have been subjected to study. Critical step evaluation of the process in mining, transport and processing activities was carried out with reference to critical trace elements by using isodynamic magnetic separator, inductively coupled plasma optical emission spectroscopy and atomic absorption spectrophotometer. Results show that colourless quartz contains the lowest trace elements concentration while feldspar-associated quartz has the highest. Lowest Fe, Al, Cr, Mn and Ni levels were observed in colourless and milky quartz in selected deposits. Manual chipping of Fe stains reduce Fe levels of 300 ppm while soil contamination increase Fe levels by 375 ppm. Transportation in iron lined trailer has a possibility to increase Fe levels up to 150 ppm due to contact with rust layer. In processing, Fe levels can be reduced by more than 20 ppm by removing the finer size fraction in each crushing step. Further reduction can be obtained to a level below 9 ppm by dry magnetic separation with 10,000 gauss 24 trays magnetic separators. Through selective mining and exercising quality control in mining, transportation and processing activities, industry specific quartz raw material can be produced.