Senapati, S.Mohanty, A.2026-02-042022Journal of The Institution of Engineers (India): Series C, 2022, 103, 4, pp. 949-95522500545https://doi.org/10.1007/s40032-022-00822-yhttps://idr.nitk.ac.in/handle/123456789/22486During 2019–20, Indian coal-based thermal power plants produced 226.13 million tonnes of coal ash (fly ash + bottom ash) which urged for safe disposal from an environmental point of view. Though as per the Ministry of Environment and Forests (MoEF) and Climate Change (CC) notification dated 3rd November 2009, 100% disposal of fly ash has to be effected in dry form for gainful utilisation within 5 years of the notification, as per the report available in 2020, 83% utilisation has been effected so far. In spite of such notification, thermal power plants always prefer to provide emergency disposal of fly ash through slurry mode to take care of the eventuality of failure for disposal of fly ash in dry form. Therefore, emergency disposal through slurry is done usually in high-concentration form for which the flow behaviour of the suspension mixture requires a thorough investigation prior to its transportation. The present study aims at evaluating the flow behaviour of the concentrated fly ash–water slurry by adding small dosages of eucalyptus leaf extract as a natural drag reducing agent (DRA). The flow behaviour of the ash–water slurry was found to be non-Newtonian in nature and was quite well described by a Bingham plastic model in the slurry concentration range of 55–65% by weight. Further, it was observed that the said bio-additive dosages (0.3–1.5%, v/v) modified the flow behaviour of ash–water slurry and was able to reduce the yield stress and viscosity quite considerably with a clear indication that the pumping power requirement and hence the specific energy consumption (SEC) could be reduced substantially while transporting these huge wastes through a slurry pipeline at high solids concentration. © 2022, The Institution of Engineers (India).Ash handlingAshesClimate changeCoalCoal ashDrag reductionEnergy utilizationNon Newtonian flowPipelinesSuspensions (fluids)Thermoelectric power plantsYield stress'Dry' [Ash–water slurryDrag reducing agentsEmergency disposalsFlow behavioursHigh solid concentrationPipe-line transportationsPumping powerSpecific energy consumptionWater slurryFly ash