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Title:Dewatering Ultrafine Slurries
Author(s):Salih, Hafiz; Patel, Vinod; Rajagopalan, Nandakishore
Coal mining -- Environmental aspects
Wastewater treatment
Osmotic dewatering
Abstract:Dewatering has been a technical and economical barrier to the stabilization of coal tailings and the utilization of ultrafine coal particles from coal preparation. While substantial progress continues to be made in conventional dewatering technologies, a non-conventional approach to dewatering utilizing an osmotic gradient was investigated as a simple, robust, and low-cost alternative. At its core, the technology relies on the directed transport of water from the coal or waste slurry to an osmotic agent, effectively achieving dewatering – in essence, a passive dewatering technology. Under this approach, dewatering is achieved by inducing an osmotic pressure difference as opposed to using mechanical pressure. Potential advantages include the use of low-pressure equipment, saline brines, and low-grade heat for dewatering. Experiments support the idea that osmotic dewatering of ultrafine coal and refuse slurry is both feasible and scalable. The dewatering performance followed expected trends with respect to factors such as slurry osmotic pressure, particle size, and dependence on properties such as sphericity. Manipulation of these factors allows for the possibility of doubling the productivity of the osmotic dewatering system. Finally, the membrane material was shown to withstand repeated use over a period of thirty trials without deterioration of performance. It is notable that the membrane was readily cleaned with water rinsing alone. A first-order economic calculation suggests that the operational cost of dewatering per ton of solids compares favorably with current costs of alternatives such as deep cone thickener, belt press, and filter press while achieving a higher degree of dewatering. The estimated cost of dewatering is sensitive to membrane life and still needs to be confirmed over longer periods of operation under real-world conditions. Further development of this dewatering technology could play an important role in reducing the volume of coal tailings currently disposed to holding ponds. Additionally, through fine coal froth flotation and subsequent dewatering, this technology could enable recovery of a significantly greater proportion of ultrafine (< 105 µm) coal (constituting as much as 6% of total coal production) currently wasted in Illinois on an annual basis. (Presented at the North American Membrane Society Meeting ; Boston, MA : June 1, 2015).
Issue Date:2015
Publisher:Champaign, IL : Illinois Sustainable Technology Center
Genre:Conference Poster
Date Available in IDEALS:2018-02-23

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