Stability Study of an Air Dense Medium Fluidized Bed Separator for Beneficiation of High-Ash Indian Coal

Author： Sahu A. K. Tripathy Alok Biswal S. K. Parida A.

ISSN： 1939-2699

Source： International Journal of Coal Preparation and Utilization, Vol.31, Iss.3-4, 2011-05, pp. : 127-148

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Abstract

Indian high ash noncoking coal contains a substantial quantity of near-gravity materials (NGM). The presence of NGM needs beneficiation in dense medium separation process. Air dense medium fluidized bed separator (ADMFBS) uses the magnetite medium to improve the separation efficiency of beneficiation of high NGM coal. Stability of the particulate fluidized bed in this system is the essential prerequisite for the separation of heavy and light particles. In this study, the characterization of medium and particulate fluidized bed was assessed to maintain the nonbubbling condition. Stability of the fluidized bed was characterized by different expressions like fluidization index, particulate expansion function, Froude number of particle, Reynolds number of particle, and pressure drop ratio using the minimum fluidization velocity, minimum bubbling velocity, pressure drop of distributor and bed, bed porosity, air viscosity, aspect ratio, density of air, and density of medium. It was found that the fluidization indexes of this system for different experimental runs are around 1 to 2. The system was scaled up from laboratory to pilot scale, having a feed throughput capacity of 600 kg/hr. Indian high ash noncoking coal at particular size (-25 + 6 mm) was used in continuous operation. The partition number was calculated based on washability data of product and reject. The Ep and imperfection value for the pilot-scale ADMFBS was found to be 0.12 and 0.071, respectively.