The Enhancement on Rheology, Flowability, and Stability of Coal Water Slurry Prepared by Multipeak Gradation Technology

Multipeaking gradation technology is an essential method for improving the slurry ability of coal particles. In this study, the coarse (150–300 μm), fine (54–74 μm), and micro (1–10 μm) coal particles with different ratios were applied to prepare coal water slurry (CWS). The ratio of coarse, fine, and micro particles in bimodal CWS, interval bimodal CWS, and triple-peak CWS was 60:40:0, 60:0:40, and 60:24:16, respectively. The effects of multipeaking technology on stability, flowability, and rheological behaviors of CWS were investigated systematically. The results indicated that the interval bimodal CWS had the best stability and flowability followed by the triple-peak CWS, and the bimodal CWS was the worst. It was demonstrated that the stability and flowability of CWS were enhanced with the increment of microparticles in slurry. Nevertheless, each slurry's maximum solid content was 68% for bimodal CWS, 65% for interval bimodal CWS, and 70% for triple-peak CWS. It could be attributed to two effects of microparticles on the apparent viscosity of CWS, i.e., filling particle clearance and binding water. If the effect of filling particle clearance was dominant, then apparent viscosity was decreased, and it was beneficial to prepare CWS with high solid content like triple-peak CWS. However, when the effect of binding water was dominant, apparent viscosity was increased, and it was unfavorable for CWS preparation corresponding to interval bimodal CWS. It was worth noting that microparticles play a double side role in preparing highly concentrated CWS.