The Research Of The Preparation Of Highly Concentrated Suspension Of Solid Particles Based On The Interface Modification

In this research, based on the gasification technology of coal-water slurry, high concentration and low viscosity suspension of solid particles was prepared through adding the secondary fluid. Based on this method, oily sludge was co-slurried with Shenfu coal and high-sulfur-petroleum coke as substitutes for coal-water slurry in entrained-flow gasifiers. This process can realize the resource utilization of hazardous organic waste and also solve the problem of enviromental pollution. The detailed contents and conclusions of this study are summarized as follows:(1) Different suspensions have been prepared using hollow glass bead, polyvinyl chloride (PVC), Shenfu coal and Brown coal, combined with the secondary fluid which immiscible with the primary fluid. The results show that addition of small amounts of a secondary fluid to a suspension could dramatically change the rheology properties of suspension. The secondary fluid could form a thin hydrophobic membrane around particle surface and the hydrophobicity of particle is improved. As a consequence, the amount of free water may be increased and the viscosity and yield stress of suspension would be reduced dramatically. To enhance the surface hydrophobicity, hydrophobic nanoparticles (nano-CaCO3) were added to the hydrophobic membrane of particles to improve the surface roughness, and to generate composite particles having a hierarchical structure similar to the micromorphology of lotus leaf. This composite particle has a higher contact angle, and the suspension of composite particles has a lower viscosity and a lower yield stress.(2) The laser scanning confocal microscope was used to observe the morphology of particles in suspensions. The results show that, for the state of kerosene preferentially wetting the particles, the red circular outlines are clearly visible, indicating that the secondary fluid is attached to the surface of particles to form hydrophobic membranes, and that pendular bridges are not formed. For the other state that kerosene not preferentially wetting the particles, kerosene is dispersed in the suspension as globular drops. So the addition of secondary fluid does not modify the particle’s surface. The secondary fluid has great influence on the contact angles of particles. For the particles modified by kerosene, the modified particle has a higher contact angle for water, the residence time of water droplet is increased from about30s to5min. For the particles modified by kerosene and nanoparticles, the contact angle of composite particle is further increased, and the water is able to maintain in droplet state for10h on the slice surface. Besides, the addition of secondary fluid could dramatically increase the Zeta potential of suspension.(3) Based on the above method, oily sludge was added to coal-water slurry in different ways to prepare desirable coal-oily-sludge slurry. The slurryability and rheological characteristics of coal-oily-sludge slurry were investigated and compared to coal-water slurry. The viscosity and yield stress of coal-oily-sludge slurry sharply decrease with increasing the addition of oily sludge that preferentially wets coal particles. Microscopic structure and surface functional groups examination proved that oil droplets present in oily sludge could form a thin hydrophobic membrane on coal particle surface and modify its surface properties. Because of the high hydrophobicity of petroleum coke, the slurry of oily sludge and high-sulfur-petroleum coke made by above method has the opposite properties with coal-oily-sludge slurry, and the modification mechanism of the secondary fluid was directly validated.