Preparation of high concentration coal water slurry with good fluidity based on preferentially modified ultrafine particle under three-peak grading

Coal water slurry (CWS) with high solid content and good fluidity is critical to efficient gasification and pipeline transport. The large number of oxygen-containing functional groups on the surface of the coal particles allow a large amount of water to be bound to the surface, resulting in a decrease in free water and an increase in apparent viscosity. Surface modification using the suspension of the second fluid and the second particle can reduce the viscosity and improve fluidity, since the oil film layer on the surface of the particles can cover the oxygen-containing functional groups and improve the hydrophobicity. Three-peak grading reduces viscosity by increasing the accumulation efficiency of particles. Preferentially modified the ultrafine particles under three-peak grading was found to result in the greatest decrease in viscosity and the most significant increase in fluidity. It not only helps to improve the accumulation efficiency, but the elastic oil film layer on the surface like an “air cushion” to reduce the frictional resistance between the particles, which effectively improved the fluidity of CWS. Ultimately, preferentially modified ultrafine particles under three-peak grading increased the slurry concentration from 62.0 wt% to 69.0 wt%, and it still had good fluidity with fluidity grade A + .