Study On The Flowability Of Pulverized Coal Based On The Microscopic Features

Pulverized coal storage and transportation are the very important links in the thermal power plants.The phenomena such as the blockage of the pulverized coal,the arch of the pulverized coal,etc. often appear in the thermal power plants,which have an important influence on the safety and economy of the thermal power plants.Therefore,it is very important to study the factors that affect the flowability of the pulverized coal.Currently,the studies of factors affecting the flowability of the pulverized coal mainly take the macro factors into consideration,but the microstructures of pulverized coal have a significant impact on the flowability of the pulverized coal.In this thesis,the six pulverized coals are used as the objects.The parameters as repose angle,cohesive force,flow function,etc. have been measured to represent the flowability of pulverized coal by using a repose angle metering devise and a Jenike shear test device.On this basis,the influence of particle size on the flowability has been studied by taking the samples with different particle sizes as the objects.In order to study the influence of the microstructures of pulverized coal(pore volume,specific surface area and surface morphology)on the flowability,all of the samples have been tested by nitrogen adsorption and electron microscope scanning.Different pulverized coals have different surface morphologies, pore structures.It has been found that the pulverized coal with a high metamorphic grade has an excellent flowability.The repose angle,cohesive force and the flow function for Yangcheng coal with the higher metamorphic grade were 48.89o,6.383 k Pa and 7.619 respectively.For the lower metamorphic Luan coal,the repose angle,cohesive force and the flow function were 53.20o,9.643 k Pa and 5.156 respectively.When the cohesive force and the flow function are used to represent the flowability,the cohesive force and the flow function of Liulin coal and Fugu coal were 8.196 k Pa,5.969 and 8.334 k Pa,5.896.Thus the flowability of Liulin coal is better than Fugu coal.But the flowability of Liulin coal with the different particle sizes is lower than Fugu coal in addition to the particle size between 88μm and 98μm.Particle sizes have an important influence on the flowability of pulverized coal.With the increase of particle size,the repose angle,cohesive force,internal friction angle,yield pressure,flow function of Fugu coal and Liulin coal vary from 50.34o,8.334 k Pa,33.703o,29.002 k Pa,5.896 to 40.023o,3.288 k Pa,29.336o,12.986 k Pa,12.652 and from 50.39o,8.196 k Pa,32.700o,22.998 k Pa,5.968 to 42.031o,5.538 k Pa,30.456o,19.365 k Pa,9.287 respectively,thus the flowability become better.The difference of the flowability is caused by the different microstructures of pulverized coal.With the increase of the pore volumes,the specific surface area and the surface roughness,the force between coal particles increases which makes the flowability become worse.