Geotextile dewatering of flocculated, fiber reinforced fly-ash slurry

Abstract

Coal-based thermal power plants are a principal source of power generation in many industrialized countries. Consequently, fly ash and other coal combustion residuals are produced in significant quantities and must be appropriately managed, most commonly using wet-storage impoundments. Concurrent with diminishing impoundment capacity and increasing beneficial reuse of coal residuals worldwide, legislation is proposed in the US to close or liner retrofit all existing impoundments. Each of these progressions necessitates an increase in the dredging, dewatering, and transport of wet-disposal ash sludge. In recent years, geotextile tubes have increasingly been used to efficiently and economically dewater a number of low percent-solids sediments, by-products, and wastes. A laboratory investigation was conducted for studying the efficacy of geotextile tubes for dewatering hydraulically transported fly ash slurry. The dewatering behavior of unmodified fly ash was compared with that of specimens reinforced with randomly dispersed flexible PVA fibers and/or flocculated with optimized polyacrylamide. Results indicate that geotextile tubes can be effectively used for dewatering flocculated fly ash slurries and that the strength of retained fly ash can be significantly improved by adding reinforcement fibers at 1% of dry solids mass.