Assessing the suitability of coarse pond ash and bottom ash as filter material

Abstract

Energy requirements for the developing countries like India in particular are met from coal-based thermal power plants. The ash generation has increased to about 131 million tonne during 2010-11and shall continue to grow. Huge amount of coal ash generation creates major problems for their disposal. Primarily, the coal ash is disposed off using either dry or wet disposal scheme. In wet disposal, the fly ash and bottom ash are transported as slurry through pipe and disposed off in pond ash. Main reason for failure of ash dyke is due to ineffective functioning of filter or internal drains. Natural river sand is used as the conventional filter material. However, the non-availability of required graded sand in and around construction site and in all seasons possesses problems to the construction of ash dykes. Coarse pond ash and bottom ash which are the waste products of thermal power plant and non-plastic in nature and available abundantly in thermal power plants may replace the conventional sand as a filtering material. In this present work coal ashes like bottom ash and course pond ash collected from NTPC, Kaniha. Coarse sand was collected from Brahmini River whereas fly ash was collected from RSP, Rourkela. Then for all the samples physical property, index properties, and geotechnical properties like grain size distribution, dry density, coefficient of permeability, crushing strength, strength parameters have been found out when samples were subjected to both dynamic and static compaction and also model test has been done to find out the filtering capabilities of these materials. It is found that coarse pond ash, bottom ash and sand used in the present study before and after meets the filter criteria as per Indian standard of practice.