Development of a Novel Fine Coal Cleaning and Dewatering Technology

Abstract

The cleaning and dewatering of ultrafine (minus 44 micron) coal slurries is one of the biggest challenges faced by coal industry. Existing commercial technologies cannot produce sellable products from these ultrafine streams; therefore, the industry is forced to discard this potential energy resource to waste impoundments. This practice also has the potential to create an environmental hazard associated with blackwater pollution. To address these issues, researchers at Virginia Tech have worked over the past decade to develop a novel separation process that simultaneously removes both mineral matter and surface moisture from fine coal particles. The first stage of the process uses immiscible non-polar liquids, such as straight chain hydrocarbons, to selectively agglomerate fine coal particles in an aqueous medium. The agglomerates are then passed second stage of processing where mild agitation is used to disperse and fully engulf hydrophobic coal particles into the non-polar liquid and to simultaneously reject any residual water and associated hydrophillic minerals entrapped in the agglomerates. The non-polar liquid, which has a low heat of evaporation, is then recovered by evaporation/condensation and recycled back through the process. The research work described in this document focused on the engineering development of this innovative process using batch laboratory and continuous bench-scale systems. The resulting data was used to design a proof-of-concept (POC) pilot-scale plant that was constructed and successfully demonstrated using a variety of fine coal feedstocks.