EFFECT OF BIMODAL / TRIMODAL SIZE DISTRIBUTION ON FLOW CHARACTERISTICS OF COAL-WATER MIXTURES (CWM).

1Mining & Petroleum Eng. Dept., Faculty of Engineering, Al Azhar University

2 Mineral processing, Mining & Petroleum Eng. Dept., Faculty of Engineering, Al Azhar University.

3 Mineral processing, Mining & Petroleum Eng. Dept., Faculty of Engineering, Al Azhar University

4 Hydraulics, Civil Eng. Dept., Faculty of Engineering, Al Azhar University

The apparent viscosity and the non-Newtonian properties based on power-law model were

investigated. Mixing of coarse and fine coal particles (bimodal size distribution) was found to

be very effective in obtaining slurries characterized by high solid contents and low viscosity.

CWS viscosity was the lowest when the blending ratio of coarse to fine particle size fractions

was approximately as 80 to 20% irrespective of the main particle size ratios. A further

reduction in slurry viscosity was achieved by adding a second coarse coal size fraction to the

optimum bimodal size distribution i.e, with trimodal size distribution. The better blending

ratio of optimum bimodal to second coarse fraction was found as 60 to 40% respectively.

Hence, it could be concluded that by careful controlling of the particle size distribution, it is

possible to prepare an optimum coal-water slurry which has a low viscosity and at the same

time has high solid concentration.