Fluid Bed Drying as Upgrading Technology for Feasible Treatment of Kolubara Lignite
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An overview of the current status of low-rank coal upgrading technologies is presented in the paper, particularly with respect to drying and dewatering procedures. In order to calculate the significant parameters of the moisture removal process, a model of convective coal drying in a fluid bed, based on the two-phase (bubbling) fluidization model proposed by Kunii and Levenspiel, is developed and presented. Product-specific data (intraparticle mass transfer, gas-solid moisture equilibrium) related to the particular coal variety addressed here (Kolubara lignite) are obtained through preliminary investigations. Effective thermal conductivity of the packed bed as defined by Zehner/Bauer/Schlunder is used to define heat transfer mechanisms occurring in the suspension phase of the fluid bed. A completely new set of experimental data obtained has been successfully used to validate the model additionally.