KSEF R&D Excellence: Combining Enhanced Gravitation and Surface Forces for Improved Energy Recovery

The fine particle size fraction in coal typically contains the greatest amount of energy per unit mass. However, the processes used to recover this valuable energy source are generally the least efficient compared to those used to treat the coarser fractions. During the 1990's, significant effort was directed toward the development of gravity-based separators that have the ability to efficiently concentrate minerals having a particle size as small as 25 microns. These concentrators, known as enhanced gravity separators (EGS), generally incorporate an enhanced gravity field of up to 300 times the natural gravitational force by a mechanically applied spinning action. It is proposed to enhance the efficiency of treating fine coal by utilizing an EGS unit that employs teeter-bed principles. Commercially known as the Knelson CVD concentrator, the unit has been recently designed to provide a variable centrifugal field up to 200 times then natural gravitation force while simplifying the concentration zones. A detail experimental program will be performed to evaluate and optimize the parametric values to ensure the realization of the ultimate performance. Models will be developed that will describe the separation density and the probable error as a function of particle size and the parametric values. To enhance the upper particle size limit, it is proposed to inject air bubbles into the system through the fluidization water and/or directly into the feed stream. The resulting bubble-coarse coal particle aggregates will have a density that is likely less than water and thus will report to the clean coal stream. The air injection method and ultimate effect will be technically and economically evaluated. Using optimum test data, specific applications will be identified and integrated into coal cleaning flow sheet. The resulting gains in energy recovery will be quantified and reported in widely distributed publications and presentations.