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Hydraulic Conveying

Analysis of Settling Characteristics of Fly Ash Slurry in a High Concentration Slurry Disposal System ...

In developing a reliable High Concentration Slurry Disposal (HCSD) system, an extensive study is needed on the rheological parameters of the slurry. In this paper an analytical study has been conducted to examine the settling characteristics of ash slurries with high solid concentration.
Results indicate that with an increase in slurry concentration, the settling tendency of ash particles reduces in the hindered settling zone and at about 60 % concentration the slurry becomes non-settling due to its finite yield stress. This has also been tested in a laboratory experiment. The experimental observations are found to be in accord with the analytical results.
High Concentration Slurry Disposal (HCSD) technique is emerging in recent years as an economic and environmentally acceptable method for disposal of ash from coal fired thermal power plants. An HCSD system essentially involves ash-water slurry transportation at high solid concentration of 50 % to 65 % on weight basis (in contrast to lean slurry of 10 % to 20 % concentration) to a disposal area where the slurry gets solidified to a soft rock structure. As it is a rather new concept, the HCSD system has lot of unexplored areas and requires extensive research to select system design parameters and equipments suitable to
the requirements.
The aim of this paper is to analyse whether the ash particles of the high concentration ash slurry will settle down at still condition of the slurry in the pipeline, which happens due to the intermittent requirement of slurry pumping and due to some unforeseen circumstances like power cut or pump tripping, as well as to determine the degree of settling tendency of the ash particles in terms of settling velocity, in case the slurry is within the settling range.