KSEF RDE: Selective Clay Agglomerant to Enhance Fine Coal Cleaning Efficiency and Recovery

Coal is the major source of energy and approximately 53% electricity IS generated from combustion of more than one billion tons of coal in the U.S. The as-mined coal often contains more than 40% minerals that will become ash during combustion. These ash-forming minerals increase the transportation cost, reduce the heating value of coal, and impair the performance of burners. They are removed prior to combustion at the coal preparation plants using techniques such as heavy medium separation, gravity separation, froth flotation, etc. Froth flotation IS the most widely used and most effective separation process for cleaning fine coal particles of - 28 mesh (06 mm) or -100 mesh (0.15 mm) that amounts up to 30% of the total coal. More than 50 million tons of coal fines are produced annually in the U.S. coal industry and two billion tons of coal fines are contained in abandoned and active slurry impoundments. Froth flotation is a process that explores the difference in surface hydrophobicity of coal and mineral particles. Coal is naturally hydrophobic while ash forming minerals such as clay or pyrite are hydrophilic. During froth flotation air is dispersed in the pulp as bubbles which are stabilized by the presence of frother, a surfactant that reduces water-air interfacial tension. Coal particles are attached to ascending bubble and eventually report to the froth product whereas minerals remain in the pulp and are discharged as the tailing or reject It has been long known that the clay particles in coal severely impede the froth flotation process. This is mainly due to Its tiny size « 1mm In most cases) or huge specific surface area that results in the adsorption of large amounts of reagents such as frother or collector that is added to the pulp to enhance flotation separation. In addition, tiny clay particles are easily carried Into the clean coal product through a mechanism referred to as hydraulic entrainment, which further reduces the sharpness of the flotation separation. Use of clay binders is a promising approach for enhancing coal flotation performance by agglomerating clay particles to enlarge their apparent size, reduce their surface area and reagent adsorption, minimize the non -selective hydraulic entrainment.