Energy-efficient fluidized bed drying of low-rank coal

An energy-saving and economical process was developed for drying low-rank coal using steam as the drying medium. Based on simulation tests, the energy consumption of the process was found to be nearly 30% lower than that of vapor recompression drying. The proposed process involves the removal of the freezable water in the coal in an exergy recuperative module, while the non-freezable water is removed in a heat integration module. During the removal of the freezable water, the evaporated water is compressed to a low pressure and recycled to the fluidized bed dryer for heat exchange with the incoming coal to minimize exergy destruction. Conversely, medium pressure steam extracted from a steam turbine is used as the heat source for the removal of the non-freezable water. No compressor was used in the process which significantly reduced the capital cost. Moreover, technical feasibility has been verified through investigating the fluidization performance of the low-rank coal particles in the fluidized bed dryer during the proposed process, particularly to determine the effect of the increased heat exchange tubes on the fluidization performance. (C) 2016 Elsevier B.V. All rights reserved.