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 + .

高固含量且具备优异流动性的水煤浆（Coal Water Slurry，简称CWS）对高效气化与管道输送至关重要。煤颗粒表面存在大量含氧官能团，可结合大量水分于颗粒表面，导致自由水含量下降、表观黏度升高。采用第二流体与第二颗粒的悬浮液进行表面改性，可降低表观黏度并改善流动性——这是由于颗粒表面形成的油膜层能够覆盖含氧官能团，提升颗粒疏水性。三峰级配可通过提升颗粒堆积效率来降低黏度。研究表明，在三峰级配体系下优先对超细颗粒实施表面改性，可实现黏度的最大幅度降低与流动性的最显著提升。该策略不仅有助于提升颗粒堆积效率，其颗粒表面形成的弹性油膜层更可如同“空气垫”一般降低颗粒间的摩擦阻力，有效改善了水煤浆的流动性。最终，经三峰级配下优先改性超细颗粒的工艺处理后，浆体浓度从62.0 wt%提升至69.0 wt%，且仍可保持优异流动性，达到A+级等级。