An initial study on feasible treatment of Serbian lignite through utilization of low-rank coal upgrading technologies

Despite benefiting from vast fuel reserves, combustion of low-rank coals is commonly characterized by low thermal efficiency and high pollutant emissions, partly due to high moisture content of the coals in question. Thus, removal of moisture from low-rank coals is deemed an important quality upgrading method. The paper provides an overview of the current status of low-rank coal upgrading technologies, particularly with respect to utilization of drying and dewatering procedures. In order to examine the influence of relevant parameters on the moisture removal process, a model of convective coal drying in a packed, as well as in a fluid bed combustion arrangement, is developed and presented. Product-specific data (intraparticle mass transfer, gas-solid moisture equilibrium) related to the coal variety addressed herein (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 packed bed. Similar two-phase fluidization model has been validated for different types of biomaterials. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved