Investigations on Performance Characteristics of a Centrifugal Slurry Pump Handling Water and Ash

Abstract

Power generation in India is primarily coal based in the present scenario. Coal used in our thermal power plants produces a large amount of ash. Currently, bottom ash is being transported hydraulically from thermal power plant to ash ponds through pipelines at low solid concentration. The operation of ash disposal pipelines is therefore highly uneconomical due to requirement of large quantity of water and increase in power consumption for pumping water. The basic parameters for the design of any slurry transportation system are hydraulic parameters, which include properties of carrier fluid, particle size, solid concentration, slurry rheology, specific gravity of the solids etc. The fly ash and bottom ash from different power plants differ greatly in their characteristics and hence the design of ash disposal system needs to take in to account these variations. It is therefore necessary to have knowledge of the properties of fly ash, bottom ash and their slurries. Pump is the heart of any ash disposal system. Coal ash is generally transported to the ash pond using slurry pumps and pipelines in the thermal power plant. Bottom ash particles are coarser without much fine particles. The Indian coal ash having higher specific gravity and also content large amount of non-combustible matter. Further, these also differ widely in their physical and chemical characteristics depending on the coal mines. Therefore in order to optimize the hydraulic design procedure for transporting bottom ash (B.A.) at higher concentrations, it is essential to carry out basic investigation using bench scale tests and pilot plant loop to develop the required technology. As rheology of the slurry plays a major role in flow, the rheological characteristics of the bottom ash in the concentration range of 10-50% (by weight) with and without the addition of fly ash has been studied to facilitate conveying of bottom ash slurry at higher concentrations.