Preparation of high concentration coal water slurry with good fluidity based on only modified fine particles under bimodal distribution using the second fluid and the second particle

Coal water slurry (CWS) is the clean and efficient liquid coal-based fuel. CWS with the high solid content, low viscosity and good fluidity is conducive to efficient gasification and pipeline transport. Surface modification of particle has been demonstrated to contribute to improving the rheology of slurry. In this study, the slurry preparation method of selective particle modification was proposed, which focuses on the effect of modified particle size. Three different methods of surface modification with the kerosene suspension containing ultrafine particles were studied and compared. In method Ⅰ, the suspension was direct added to the mixture of coarse and fine particles. In method Ⅱ and method III, the suspension only modified the coarse and fine particles respectively, then mixing the composite particles with another particle. The apparent viscosity, fluidity and the hydrophobicity of the particle surface were researched. Method III was found to be optimum for reducing apparent viscosity and improving fluidity. The thin hydrophobic oil membrane that coats the surface of the fine particles like an “air cushion”, which can effectively reduce the friction between the particles. The concentration of CWS prepared by method III can increase from 62.7 wt% to 67.0 wt%, and the slurry still has a good fluidity.