Influence of Chemical Reagents on Rheological Properties of Fly Ash-Water Slurry at Varying Temperature Environment

Abstract

About 70% of total electrical energy is generated from thermal power plants in India which in turn release about 160 Mt of fly ash as solid waste annually. Transportation and disposal of such a huge amount of fly ash is a major problem faced by the power plants. Presently fly ash is transported as lean slurry in pipe lines requiring about 80 to 85% of water with high energy input. A major impediment in high volume transportation of fly ash is its high specific gravity as compared to that of water. The objective of the present study was to evaluate the rheological characteristics of high concentration fly ash slurry with and without a chemical reagent at varying temperature environment to facilitate smooth flow of materials in the pipelines. Six different composition of fly ash slurry samples were considered for investigation. The main constituents of the slurry were fly ash, water, a cationic surfactant, and a counter-ion. Detailed rheological properties were determined using a cylindrical coaxial rotational rheometer at shear rates varying from 25s 21 to 1000s 21 for 40% solid concentration (by weight). Temperature was varied from 20uC to 40uC for all the shear rates investigated. Test results showed that all the slurries exhibited shearthinning behaviour in the presence of the surfactant. The influence of cationic tenside on drag reduction of fly ash slurry was also studied. The distinctive reduction of surface tension on colloidal dispersion characteristics of the fly ash slurry was observed in the presence of the tenside. It revealed that the slurry developed in the above manner has a potential to be transported through pipelines with minimal energy consumption.

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

“…The addition of the cationic and the counter ions reduces the surface tension with the aim of enhancing the suspension strength in particulates. An increase in the wetting and spreading properties is found which results in low power/water requirements [10]. Senapati et al [11] investigated the fly/bottom ash slurries to predict the effects of friction on the concentrated slurry.…”

Experimental study on the rheological behaviour of coal ash slurries

“…Naik et al (2009aNaik et al ( , 2009bNaik et al ( , 2011 studied the effects of addition of Cetyl Trimethyl Ammonium Bromide and Sodium Salicylate on the rheological Properties of FA-water suspensions for 20% to 40% concentration at temperature ranging from 20 to 40 0 C and found that the viscosity and shear stress decreased for all the cases with increase in temperature and the slurry without additive showed shear thickening behaviour but exhibited almost Newtonian pattern with a zero yield stress when the concentration of the additive solution increased gradually with an incremental value of 0.1% by mass. According to their investigation the effective additive concentration range was found to be from 0.2% to 0.3% by mass.…”

The Effect of Selective Additives on the Rheological Behavior of Power Plant Ash Slurry

“…The polymer Separan AP-302 was injected into pipeline (up to 60 wppm) and observed increasing of concentration and pipeline load capacity represented 22% drag reduction effect. The effect of addition of chemical reagents on rheological flow behavior of ash slurry was studied by some researchers (Vlasak and Chara, 2007;Seshadri et al 2008;Naik et al 2011;Senapati et al 2012;Singh and Lal, 2012). It was indicated that the additive modified the rheological behavior of the ash slurry at high solids concentration and the ash slurry viscosity got reduced with improved flow behavior.…”