Date of Graduation
Statler College of Engineering and Mineral Resources
Although froth flotation methods are the major processes being used in treating ultrafine coal in coal preparation plant, the processes might require large quantities of frother and collectors. The usage of reagents not only might increase the operating costs, but also cause environment concerns. 4+3 short turns two-staged spiral concentrator has been developed, applied in ultrafine coal cleaning circuit, and operated at a lower flowrate than that of spiral used in fine coal cleaning circuit. Ultrafine spiral concentrator is a specific gravity-based separator. It might be gradually accepted in ultrafine coal cleaning circuit as an alternative to froth flotation methods in ultrafine coal cleaning circuit of coal preparation.;To evaluate the ultrafine spiral in-plant separation performance, in-plant coal samples are collected from an ultrafine coal cleaning circuit in a coal preparation plant processing medium volatile bituminous coal in West Virginia. Detailed wet particle sizing and float-sink analysis using Lithium Metatungstate heavy liquid, are conducted at various particle size intervals. The particle size effects on the separation performance of ultrafine spiral to produce clean coal, and clean coal+middlings products were are evaluated. The characteristic parameters for the performance distribution curves, include the values of probable error, Ep, specific gravity separation, SG50, and the coefficient of variation, CV are derived by curvefitting to in-plant separation performance data. Those parameters have the values of Ep∼0.47- 0.12, SG50∼2.1-1.5, and CV∼0.162-0.04 for clean coal, and Ep∼0.44-0.12, SG50∼2.50 -1.52, and CV∼0.24-0.15 for coal+middlings. A narrow size interval would be desired for optimum separating efficiency because the better separation occurred to the different particle size intervals with different operation conditions. This study also finds that the ash contents of spiral clean coal, and clean coal+middlings products are affected by the misplaced particles of plus 150mum and minus 45mum introduced by the inefficiency of ultrafine spiral feed classifying cyclone. To maintain the high quality of products, desliming the product using clean coal classifying cyclone becomes necessary to remove high clay particles in minus 45mum size interval.
Yang, Meng, "Evaluation of ultrafine spiral concentrators for coal cleaning" (2010). Graduate Theses, Dissertations, and Problem Reports. 2126.