Fluidity of Ultra-fine Palverized Coal

Abstract

The internal friction of ultraifine coal was measured, and then the flow curve, the apparent viscosity and the yield value were measured too for both the fixed bed of ultra-fine coal and the fluidized bed.
The coefficient of internal friction and the cohesive force were from 0.6 to 0.7 and from 70 to 80 g/cm² respectively for the ultra-fine coal. These values were smaller than that of the wheat sold in the markets and larger than that of the standard sand. In case the ultra-fine coal becomes small in its size range, the internal friction of it decreases and the cohesive force of it increases.
The flow curve is obtained from the shearing stress and the shearing rate, and it was considered that the fixed bed of urtra-fine coal shows the dilatant flow curve and would be the rheological pseudoplastic.
The apparent viscosity for the ultra-fine coal increases in the case of increasing of the external force, and this becomes constant value in case of the external forcebe comes over the constant value. The fluidized bed shows the Newtonian flow because the viscosity of it is similar to that of water under the condition of the gas velocity of from 1 to 2 cm/sec.
The yield value of fixed bed is very large in comparison with the other fluid, and this value increases in case of the large size range. The yield value decreases remarkably for the fluidized bed, and this value becomes about zero under the condition of the gas velocity of some 0.3cm/sec.