Evaluation of Flow Characteristics of Fly Ash Slurry at 40% Solid Concentration with and without an Additive

Abstract

In India, about 75% of total electrical energy is generated from thermal power plants which in turn release about 130 million tones 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 being transported as lean slurry in pipe lines requiring about 80 to 85% of water with more energy input. The objective of the present study was to evaluate the rheological characteristics of fly ash slurry with and without an additive at varying temperature environment to facilitate smooth flow of materials in the pipeline. To achieve the objectives, six number of fly ash slurry samples were prepared from the fly ash obtained from a power station situated in the southern part of India. 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 co-axial rotational rheometer at shear rates varying from 100 to 1000s-1 for 40% solid concentration. Temperature was varied from 200C to 400C for all the shear rates investigated. Test results showed that all the slurries exhibited Newtonian properties of shear-thinning behavior in the presence of an additive. The influence of cationic tenside on drag reduction of fly ash slurry was also studied. The distinctive reduction of surface tension on colloidal disperse characteristics of the slurry was observed in the presence of the tenside. The study revealed that the slurry developed in the above manner has a potential to be transported through pipelines with minimal energy consumption.