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ASSESSING THE SUITABILITY OF COARSE POND ASH AND BOTTOM ASH
12-25-2013, 10:34 PM
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Lightbulb ASSESSING THE SUITABILITY OF COARSE POND ASH AND BOTTOM ASH
This thesis-Project report is submitted as a part of M Tech in Civil Engineering.You can take help of this thesis to prepare your M Tech B Tech Final year project report.

Abstract:-

Energy requirements for the developing countries like India in particular are met from coal-based thermal power plants, where 75% of the total power obtained is from coal-based thermal power plants. The coal reserve of India is about 200 billion tonnes (bt) and its annual production reaches 250 million tonnes (mt) approximately. About 70% of this is used in the power sector. In India, unlike in most of the developed countries, ash content in the coal used for power generation is 30–40%. High ash coal means more generation of a large amount of fly ash. India ranks fourth in the world in the production of coal ash as by-product waste after USSR, USA and China, in that order. Huge amount of coal ash generation creates major problems for their disposal. Therefore large quantity coal ash has to be suitably disposed off.

Primarily, the coal ash is disposed off using either dry or wet disposal scheme. In dry disposal, the fly ash is transported by truck, chute, or conveyor at the site and disposed off by constructing a dry embankment (dyke). In wet disposal, the fly ash and bottom ash are transported as slurry through pipe and disposed off in pond ash. There are no well defined design guidelines and code practices available for construction and maintenance of ash dykes. So in past there are so many failures of ash dykes are observed. Main reason for failure of ash dyke is due to ineffective functioning of filter or internal drains. The purpose of filter in the case of ash dyke is to protect the fly ash against being carried away with seepage and at the same time it should have adequate permeability to take out the seepage water in order to keep the fly ash in a dry condition avoiding liquefaction due to any disturbance. 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. Non-availability of good sand during monsoon also affects the sustained and pre-planned construction of ash dykes in monsoon season. 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.
Limited work has been reported in the literature on evaluation of the geotechnical properties of coal ash and their utilisation in filter media in ash pond dykes. This present work aims to find out the geotechnical properties of coal ash subjected to different loading intensity and its filter criteria. For this purpose coal ashes like bottom ash and coarse pond ash samples used in this study were collected from hopper and ash pond of NTPC, Kaniha, Odisha respectively.

Coarse sand was collected from Brahmini River whereas fly ash was collected from RSP, Rourkela. Coal ashes, coarse pond ash and bottom ash and sand were subjected to both dynamic and static compaction. 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.

Based on the experimental findings the following conclusions are drawn. Specific gravity of pond ash and bottom ash are found to lower than that of conventional earth material. As the dynamic compaction energy and static stress increases, particles crushed. The gradation changes from uniformly graded to well grade. These samples show higher maximum dry density compare to virgin sample. After crushing due to both static and dynamic compaction, the coefficient of permeability of coal ash and sand samples decrease. Strength parameters of coal ashes and sand subjected higher compaction energy and static stress are found to be higher when tested at their minimum and maximum densities. At low load intensity crushing coefficient of coal ash is higher than sand but at very high load intensity crushing coefficient of sand is higher than coal ash. From the model test it was found that coefficient of permeability of all the virgin samples and layered samples decrease with increase in time due to settlement of fly ash slurry. After 60 min. values of coefficient of permeability of all samples are found to be same and do not change with time. So as per permeability criteria coarse pond ash and bottom ash can replace sand in filters. From the model test it was found that turbidity of all the virgin samples and layered samples decrease sharply with increase in time. It is found that coarse pond ash, bottom ash and sand used in the present study meets the filter criteria as per Indian standard of practice. After crushing in both static and dynamic compaction it is found that all three samples coarse pond ash, bottom ash and sand used in the present study meets the filter criteria as per Indian standard code of practice. Use of both coarse pond ash and bottom ash as a filter material also reduces the cost of construction of ash dyke. It is also an effective means of utilisation of thermal power plant waste.



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