Experimental study on the rheological behaviour of coal ash slurries

Assefa, K. M.; Kaushal, D. R.

doi:10.1515/johh-2015-0029

Cited by 18 publications

(9 citation statements)

References 16 publications

(12 reference statements)

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“…Pani et al [18] studied the rheological behaviour of coal ash slurry and investigated the effects of chosen additives on it. Assefa and Kaushal [19] carried the experimental investigations on bottom/fly-ash slurry with/without additions of fly/bottom ash in order to evaluate its rheological behaviour. The extensive drop in the yield stress and the viscosity is observed with 30% mixing proportions to the fly ash slurry whereas the aforesaid parameters rapidly shoot up with 40% of mixing proportions at all solid concentrations.…”

Section: Introductionmentioning

confidence: 99%

Flow Characterization of Multi-Phase Particulate Slurry in Thermal Power Plants Using Computational Fluid Dynamics

Parkash¹

2020

Journal of Thermal Engineering

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The key issue associated with the thermal power plant is the disposal of ash-water slurry and the process of its transportation is accomplished using long length pipelines. The designing of such pipelines is a vital endeavor of researchers and designers globally. In this perspective, numerical simulation of 42 mm diameter three-dimensional slurry flow pipeline carrying high concentration of mono-dispersed fine ash particles has been carried out. The study is enunciated by employing Eulerian-Eulerian two-phase model with RNG k-ɛ turbulence model with the aim of visualizing and understanding the characteristics of the slurry flow behavior. The coal ash slurry concentration varies between 50% to 70% (by weight) for velocity ranges, 1-3 ms -1 . The modeling is done using Fluent commercial software with the intention of predicting the characteristics of flow for 300 µm particle size. It is observed that pressure drop upsurges non-linearly with solid concentrations and slurry velocity across pipeline. The obtained results of predetermined pressure drop are analytically compared with the experimental results. Moreover, the results are also compared with that of Eulerian-Langrange model using SST K-ω turbulence model and it is found that RNG k-ɛ turbulence model yields more accurate and desirable results.

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Section: Introductionmentioning

confidence: 99%

Flow Characterization of Multi-Phase Particulate Slurry in Thermal Power Plants Using Computational Fluid Dynamics

Parkash¹

2020

Journal of Thermal Engineering

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“…The flow behavior of fly ash slurry depends on different factors, for instance, shape of particles, particle size distribution, solid concentration in slurry, and slurry viscosity. 9 Viscosity and shear stress of slurry could be decreased by adding different additives, thereby enhancing the possibilities of a high percentage of solids in the slurry transportation. 10 Many investigators have examined the effects of various additives on the rheological behavior of fly ash slurry at high concentrations during pipeline transportation.…”

Section: Introductionmentioning

confidence: 99%

Stabilization and Rheological Behavior of Fly Ash–Water Slurry Using a Natural Dispersant in Pipeline Transportation

Das¹,

Pattanaik

Parhi

et al. 2019

ACS Omega

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Effective transportation of fly ash–water slurry through a pipeline from its generation site, a power plant, to a storage site by replacing commercial surfactants such as cetyl trimethyl ammonium bromide and sodium dodecyl sulfate by a natural dispersant extracted from Sapindus laurifolia was studied. The stability of fly ash slurry was determined from its rheological parameters, dispersant concentration, and stabilization mechanism. From surface tensiometric data, the critical micelle concentration of the dispersant was obtained to be 0.017 g/cc. The stabilization of high-concentration fly ash slurry has been studied through its rheological behavior by variation of temperature and dispersant and ash concentration. The rheological result obtained for fly ash concentrations in the range of 50–65% slurry was best justified by the Bingham plastic model. The wettability of fly ash particles is increased in the presence of dispersants, which is inferred from reduction of the surface tension value. The stabilization mechanism of the slurry is explained by a steric factor as indicated by the decrease in the zeta potential value. Air pollution is minimized at its destination site due to agglomeration of fly ash particles, which is confirmed from the SEM microphotograph.

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“…The flow behavior of the slurry in long distance pipeline is also influenced by pipeline design parameters such as diameter of pipe and pipe bends and these parameters can be optimized by using CFD modeling in FLUENT software (Kaushal and Tomita, 2002; Kaushal et al , 2005; Kaushal et al , 2012, 2013; Kumar et al , 2015). It was experimentally observed that fly ash samples at higher concentrations with finer particles also affect the viscosity of the sample (Assefa and Kaushal, 2015; Singh et al , 2015, 2016). Chemical additives also affect the rheological and flow properties of slurry.…”

Section: Literature Reviewmentioning

confidence: 99%

Pressure drop calculation for fly ash slurry using rheological model

Singh

Kumar

Kaushal

2019

WJE

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Purpose This paper aims to the transportation of high concentration slurry through pipelines that will require thorough understanding of physical and rheological properties of slurry, as well as its hydraulic flow behavior. In spite of several contributions by the previous researchers, there is still a need to enrich the current understanding of hydraulic conveying through pipeline at various flow parameters. The pilot plant loop tests, particularly at high concentrations, are tedious, time-consuming and complex in nature. Therefore, in the current research the prediction methodology for slurry pipeline design based on rheological model of the slurry is used for calculation of pressure drop and other design parameters. Design/methodology/approach It has been established that slurry rheology plays important role in the prediction of pressure drop for laminar and turbulent flow of commercial slurries through pipeline. In the current research fly ash slurry at high concentration is chosen for rheological analysis. The effect of particle size and solid concentration is experimentally tested over the rheological behavior of slurry and based on the rheological data a correlation is developed for calculation of pressure drop in slurry pipeline. Findings The present study strongly supports the analytical approach of pressure drop prediction based on the rheological parameters obtained from the bench scale tests. The rheological properties are strongly influenced by particle size distribution (PSD), shear rate and solid mass concentration of the slurry samples. Pressure drop along the pipeline is highly influenced by flow velocity and solid concentration. The presence of coarser particles in the slurry samples also leads to high pressure drop along the pipeline. As the concentration of solid increase the shear stress and shear viscosity increase cause higher pressure drop. Research limitations/implications The transportation of slurry in the pipeline is very complex as there are lot of factors that affect the flow behavior of slurry in pipelines. From the vast study of literature it is found that flow behavior of slurry changes with the change in parameters such as solids concentration, flow velocity, PSD, chemical additives and so on. Therefore, the accurate prediction of hydraulic parameter is very difficult. Different slurry samples behave differently depending upon their physical and rheological characteristics. So it is required to study each slurry samples individually that is time-consuming and costly. Practical implications Nowadays in the world, long distance slurry pipelines are used for the transportation of highly concentration slurries. Many researchers have carried out an experiment in the design aspects of hydraulic transportation system. Rheological characteristics of slurry also play crucial role in determining important parameters of hydraulic conveying such as head loss in commercial slurry pipeline. The current research is useful for the prediction of pressure drop based on rheological behavior of fly ash slurry at various solid concentrations. The current research is helpful for finding the effect of solid concentration and flow velocity on the flow behavior of slurry. Social implications Slurry pipeline transportation has advantages over rail and road transportation because of low energy consumption, economical, less maintenance and eco-friendly nature. Presently majority of the thermal power plants in India and other parts of the world dispose of coal ash at low concentration (20 per cent by weight) to ash ponds using the slurry pipeline. Transporting solids in slurry pipelines at higher concentrations will require a thorough knowledge of pressure drop. In the current research a rheological model is proposed for prediction of pressure drop in the slurry pipeline, which is useful for optimization of flow parameters. Originality/value All the experimental work is done on fly ash slurry samples collect from the Jharli thermal power plant from Haryana State of India. Bench scale tests are performed in the water resource laboratory of IIT Delhi for physical and rheological analysis of slurry. It has been shown in the results that up to solid concentration of 50 per cent by mass all the samples behave as non-Newtonian and follows a Herschel–Bulkley model with shear thickening behavior. In the present research all the result outcomes are unique and original and does not copied from anywhere.

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Experimental study on the rheological behaviour of coal ash slurries

Cited by 18 publications

References 16 publications

Flow Characterization of Multi-Phase Particulate Slurry in Thermal Power Plants Using Computational Fluid Dynamics

Flow Characterization of Multi-Phase Particulate Slurry in Thermal Power Plants Using Computational Fluid Dynamics

Stabilization and Rheological Behavior of Fly Ash–Water Slurry Using a Natural Dispersant in Pipeline Transportation

Pressure drop calculation for fly ash slurry using rheological model

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