Slurryability and flowability of coal water slurry: Effect of particle size distribution

As a part of clean coal technology, the coal water slurry has a popular application in the conventional and new thermal power stations. The hydrotransport is now-a-days a preferred method, due to its low specific energy consumption and non-polluting nature. The lignites and high ash coals, available in abundance, show poor slurryability, thereby making the process unsustainable. This study proposes and demonstrates how a careful selection particle size distribution can help in the improvement of the slurry stability, rheology and flow characteristics. To achieve this objective, 3 different size ranges of pre-pulverized coal are considered and blended to get a total of 8 blended samples. The influx concentration of a given sample ranges in 10–60%. The influx velocity of mixture lies in the range of 0.25–1.25 m/s, through a pipeline of 100 mm diameter. The parameters viz. Settling characteristics, apparent viscosity, headloss and specific enthalpy consumption are evaluated to choose the best particle size distribution of the coal sample. The 30% fraction of >53 μm and <75 μm particles and 20% fraction of >75 μm and <106 μm are found to be optimum for high stability, low viscosity and specific enthalpy consumption. This study provides a simple solution to enhance the flow characteristics of a high ash Indian coal.