Investigation of high concentration slurry disposal through pipe bend

Abstract

The present investigation is carried out to investigate the head loss characteristics across 90and#730; pipe bends for the flow of concentrated coal and coal-ash slurries. Before head loss experiments, different bench-scale tests are carried out to analyze the physical and chemical characteristic of solid particles. The specific gravity of coal, fly and bottom ash sample is determined as 1.46±2%, 2.27±0.5% and 2.09±1.6%. The maximum settled concentration for coal, fly ash and bottom slurry is observed as in range 65.37-76.55%, 59.67-73.92% and 53.79-68.58% for a solid concentration range of 30-60% respectively. The pH of coal-water slurry varies in the range of 6.38-5.93 as solid concentration is increased from 10-60% (by weight). The pH value for fly and bottom ash suspensions are lies in the range of 7.62-7.42 and 7.68-7.45 respectively for the solid concentration range of 30-60%. Extensive rheological experimentation is performed to analyze flow characteristics of coal-water slurry with and without the use of the additive. The coal-water slurry exhibits Newtonian behaviour at a solid concentration of 30% (by weight). The coal-water slurry exhibits shear thinning behaviour at higher solid concentrations (i.e. above 30%) that show its pseudo-plastic nature. The addition of a small amount of sulphonic acid resulted in an improvement in the rheological properties of the coal-water slurry suspension. Similarly, the rheological experiments are carried out for fly and bottom ash slurry with and without the use of additive (sodium triphosphate). The fly ash slurry exhibits Newtonian behaviour for a solid concentration of 30%. Fly ash slurry shows Bingham plastic behaviour for a solid concentration range of 40-60% (by weight). The bottom ash slurry exhibits Newtonian behaviour for solid suspension up to a solid concentration of 30%. The bottom ash slurry shows Bingham flow behaviour above 40% solid concentration. The addition of sodium triphosphate results in a decrease in viscosity of bottom and fly ash slurry.