Commercial and many advanced coal cleaning processes produce coal fines (14 mesh or finer) either as byproducts of normal processing or as deliberately planned, essential steps in the coal cleaning process. These coal fines are generally recovered as aqueous coal slurries, which can be dewatered mechanically (e.g., filtration or centrifugation) to reduce the residual water content to about 20 to 40%. Further drying requires a second step wherein heat is added to evaporate the residual moisture. The drawbacks of commercially available thermal coal dryers include excessive elutriation of fines, coal attrition, low thermal efficiency, and high capital and operating costs. Vibrated bed dryers with embedded heat transfer surfaces offer improvements in all of these areas with very compact, economic designs. During Phase I of this project, vibrated bed operation is being characterized in cold flow testing, followed by limited hot flow tests to demonstrate potential thermal drying performance. Successful completion of Phase I will demonstrate the technical feasibility of such devices for thermally drying fine coal. Vibrated bed dryers should significantly improve the environmental performance of thermal coal drying and would facilitate economic recovery of coal fines that might otherwise be discarded.Anticipated Results/Potential Commercial Applications as described by the awardee:Vibrated bed dryers should greatly reduce the cost of thermally drying fine coal relative to existing fluidized bed and fixed bed thermal drying methods. Applications also exist in advanced coal cleaning processes where fine grinding is required. Vibrated bed drying utilizing embedded heat exchange surfaces is an emerging unit operation applicable to the chemical, mineral, pharmaceutical, food, and other industries.
