Effect of Moisture Content on Fluidization of Wet Brown Coal Particle with Wide Particle Size Distribution

The world's coal resources amount to around 900 billion tons, but half of this is sub-bituminous coal and brown coal. Brown coal often contains more than 50% (wet basis) moisture, which reduces the generating efficiency of brown coal-fired power plants. Therefore, pre-drying in large quantity with low energy consumption is a key technology for its efficient utilization. A fluidized bed dryer using superheated steam for fluidizing gas is suitable for this purpose, because this technology can simultaneously attain higher heat transfer coefficient, larger capacity of dryer, higher safety (absence of oxygen in the fluidizing gas) and more effective heat recovery by using evaporated steam as a heat source after compression. However, high-moisture coal is cohesive and it is important to know the influence of moisture content on its fluidization characteristics. In this research, experiments were carried out to evaluate the effect of moisture content on fluidization by visualization using cold fluidized bed test equipment. As a result, a quantitative relationship between moisture content and fluidizing characteristics was obtained by introducing angle of repose as an index of cohesiveness.