Browsing by Author "De Silva, IMBM"

Now showing 1 - 3 of 3

item: Conference-Full-text
Application of mebrane separation processes to the Sri Lankan industry
(2000) Amarasinghe, BMWPK; De Silva, IMBM
Membranes and membrane based separation techniques have developed rapidly over the last two decades with a considerable technical and commercial impact. The technology is now widely used for a range of applications including water treatment, wastewater treatment, separations in the Chemical and Process industries, food and biotechnological industries and in the medical field. Micro Filtration, Ultra Filtration, Reverse Osmosis, Electro Dialysis and Dialysis are the commonly used processes. Nano Filtration, Pervaporation, Osmotic Distillation and Membrane Distillation are now becoming popular with the development of novel membranes, which withstand a wide range of operating conditions. The Membrane Separation technique is attractive due to many reasons, such as suitability of the processes for heat sensitive materials, high product quality and possibilities of recovery and recycle of valuable materials. The survey shows very few applications of Membrane Processes in Sri Lankan industries. Normal Filtration and Ion Exchange are the widely used methods for water treatment. However, the application of a technique such as Reverse Osmosis or Ultra Filtration for water treatment in medical and pharmaceutical field, in drinking water production from high salinity level water and in food and beverage industries may largely help in improving the product quality. Wastewater is commonly treated using biological treatment and chemical treatment in combination with sedimentation. Approximately, 51% of the industries have the possibility of using Membrane Separation techniques not only to treat wastewater, but also to recover or recycle valuable materials, energy and water. Pulp and paper, Textile and Diary industries are the major uses of Membrane technology for wastewater treatment. Further, the novel separation techniques such as Pervaporation and Osmotic distillation can be experimented for the manufacture of range of new products. Application of Membrane Separation processes in Sri Lankan industry will be important in anticipation of future demands for high standards and minimal environmental impact.
item: Article-Full-text
Application of membrane separation processes to the Sri Lankan Industry
Amarasinghe, BMWPK; De Silva, IMBM
Membrane separation is a relatively new technology applicable for a range of separations. The technique is attractive due to its ability to produce high quality products, suitability for processing heat sensitive materials and possibility of recovering and recycling of valuables from waste streams. Current applications of membrane separations for liquid systems in the Sri Lankan industry and possibilities for future developments were investigated. The survey shows that only 5% of the industries considered for the survey currently use membrane separations. However, 51% have the possibility of using membrane separations either for water treatment, wastewater treatment or for separations in the manufacturing processes. Normal Filtration and Ion Exchange are the widely used techniques for water treatment. Reverse Osmosis and/or Ultra Filtration can be used for purification of water for medical and pharmaceutical applications, for preparing drinking water and boiler feed water from high salinity water or seawater. Pulp and paper, Textile and Diary industries have the possibilities of using MS for wastewater treatment and recovery and recycle of valuables. However, novel techniques such as PV can be used for removal of tracers of hazardous components. Further, Pervaporation, Osmotic Distillation etc. can be experimented for the manufacture of new range of products in food and biotechnological fields and for obtaining highly purified products. Despite the relatively high capital and maintenance cost and the problems of concentration polarisation and membrane fouling application of the technique for many Sri Lankan industries will be important in anticipation of future demands of high standards and minimal environmental impact.
item: Thesis-Abstract
Reverse flow cyclones for collection of tea dust
De Silva, IMBM; Amarasinghe, BMWPK
Reverse flow cyclones are used most extensively in the chemical process industries for gas - solid separation. Cyclones are often employed to collect large particles (>5Ilm) that can be used not only as an air pollution control device, but also for recover particulate matter and size separation of particles. Common features found in locally designed cyclones are ineffective and crudely designed. Design of cyclone is more towards realizing a shape of the cyclone than the performance. Customized design approach gives a cyclone with greater collection efficiency, smaller in size or with lower pressure drop that would be found for a conventional standard design. Since the customized design procedure requires trial and error calculations, this research focused on the importance of the development of a computer package: "CycDesign" . Using this package, a pilot scale reverse flow cyclone is designed and fabricated. This unit was used to examine the suitability of abating the air pollution caused due to dust generated from the fluidized bed dryers in tea industries. Trials were also done for sawdust, cement, quarry dust, talc powder and silica sand. Inlet and outlet particle size distributions were measured. Above 90% Overall collection efficiencies were attained for all the types of dust tested. For tea dust 99.2% collected experimentally which was predicted as 100% by the computer package. Also the computer package can be used to predict performance and dimensionless parameters for a cyclone design. It predicts that a continual decrease of Stokes number based on cut diameter, with increasing Reynolds number Re, for cyclones having different height to diameter ratio HID. According to predictions, collection efficiency increases with HID ratio of the cyclone. The declining patterns of fractional efficiency can be visualized with decreasing pressure drop across the cyelone and particle density. A decrease in fractional efficiency can be observed with the increasing of gas flow rate, gas temperature, and gas density..