Cleaning and upgrading of coal-series kaolin fines via decarbonization using triboelectric separation

As an important non-metallic mineral, cleaning and upgrading of coal-series kaolin is significantly important to the subsequent processing and utilization. In the work, the triboelectric separation was used to remove the organic carbon from coal-series kaolin, which is based on the differences of mineral conductivities. The effect of applied voltage, feed frequency, and airflow rate on the decarbonization was experimentally studied. The mineral and chemical compositions in coal-series kaolin were tested. The results indicated that the coal-series kaolin sample mainly contained kaolinite and some mineral impurities, such as quartz, dickite, and anatase. The impurities of raw sample consisted of large amounts of organic components and small amounts of impurity elements, such as Si, Fe, Ti, K, Ca, and Mg. Considering both the decarbonization efficiency and recovery efficiency of valuable components, the efficient purification and cleaning of coal-series kaolin can be achieved via the triboelectric separation with various operational factors of the applied voltage U of 28-36 kV, the feed frequency F of 5-10 Hz, and the airflow rate V of 20-30 cm(3)/s, respectively. In particular under the condition of U = 32 kV, F = 5 Hz, and V = 20 cm(3)/s, the optimal yield and ignition on loss of concentrates of 67.82% and 17.76% were achieved. Correspondingly, the satisfied decarbonization efficiency and recovery efficiency of valuable components were 27.78% and 73.95%, respectively. The results indicate that the efficient cleaning and upgrading of coal-series kaolin fines can be realized via the novel dry-based technology of triboelectric separation. (C) 2019 Elsevier Ltd. All rights reserved.