Preparation of high concentration coal water slurry of lignite based on surface modification using the second fluid and the second particle

Abstract

Lignite is difficult to be used in the preparation of high concentration coal water slurry. To improve its slurryability, two methods based on surface modification were investigated. In method I, the second fluid which is immiscible with the continuous phase of the suspension was added to the dried lignite particles to form a thin hydrophobic membrane. And in method II, the second particle which has a good hydrophobicity was dispersed in the second fluid and added to the lignite. Apparent viscosity of CWS of lignite decreased obviously by method I, and it had a further decreased by method II. And the results of contact angle showed that there was an obvious increase in hydrophobicity of lignite particles, which were corresponding to the decrease of apparent viscosity of CWS of lignite. Microscopically, the structure image obtained by the confocallaser scanningmicroscope showed the existence form of the second fluid in CWS of lignite, which revealed the causes of the decrease of apparent viscosity on the particle scale. In this study, the maximum slurry concentration (MSC) of lignite prepared by method II increased from 53.4 wt% to 56.3 wt%, and the slurry had a good fluidity.