Application of the Reflux Classifier for coal macerals separation

摘要

As a water based device, the Reflux Classifier that contains a fluidized bed with a system of parallel inclined plates above was previously designed for separating mineral and coal particles on the basis of density and particle size. Light particles with small size are removed as overflow while heavy particles with large size are refluxed back to the fluidized bed. Therefore, larger particles with higher densities are obtained at higher water flow rates. The objectives of this work are to separate vitrinite rich and inertinite rich coal maceral concentrates based on their differences in densities, and evaluate the thermo-swelling properties of these concentrates to examine the feasibility of applying the Reflux Classifier to separate coal macerals. Firstly, coal slurry for a single coal with particle size less than 212 μm was fed in the Reflux Classifier device, a range of maceral concentrates with vitrinite contents varying from 81.8% to 29.0% were obtained. Secondly, another coal with particle size cuts was applied in the Reflux Classifier. Coal macerals were produced with the vitrinite content varying from 91.2% to 26.1% for 106-212 μm particle size fraction and 96.0% to 38.2% for 212-500 μm particle size fraction. The vitrinite rich concentrates showed lower densities and ash contents, and larger volumetric swelling and reaction heat between 400 and 600 °C during pyrolysis than the inertinite rich concentrates. For size cuts of maceral concentrates from the second coal, the high vitrinite concentrates such as those contain more than 63.0% vitrinite, the measured maximum swelling increased with vitrinite content and was independent of particle size due to the high thermoplasticity. However, this conclusion did not apply to maceral concentrates that did not show high thermoplasticity, such as the maceral concentrates contain less than 63% vitrinite. Therefore, the Reflux Classifier can be successfully employed for separating coal maceral concentrates, and the obtained coal maceral concentrates showed distinct difference in thermo-swelling behaviour.