Lignite drying and dewatering technologies

With a high water content, lignite has a low efficiency for direct combustion power generation. The lignite drying and dewatering technology can effectively lower the water content of lignite and enhance its competitive power. On this basis, the authors studied and analyzed the principles of the following technologies, namely, flue gas drying technology, steam drying technology (tube type drying and fluidized bed steam drying), hydrothermal dewatering technology, mechanical thermal dehydration (MTE) technology and upgraded brown coal (UBC) technology. Moreover, they also contrasted and analyzed the pressure, temperature, removing state, dewatering effectiveness, pore structure and re-absorption characteristics of various drying and dewatering technologies. The mechanical thermal dehydration technology can change the pore structure of brown coal and prevent from re-absorption, thus achieving a relatively high dewatering efficiency with a low energy consumption rate. It is of major significance for China to develop novel drying and dewatering technologies with due consideration of the brown coal distribution features of China to lower the water content of coal from its source, realize an economic transportation of coal and enhance the power generation efficiency of power plants.