Beneficiation of difficult-to-wash Indian low volatile coking coal fines by Falcon concentrator

Abstract

The fast depleting reserves of high-grade Indian coking coal and its resultant dependence on import makes the emerging situation a fit case for exploring innovative and high efficacy techniques such as non-conventional gravity-based systems for clean coal recovery viz., advanced centrifugal gravity separators like Falcon concentrators for fine and ultra-fine coal particles processing using enhanced gravitational force. The above methodology has been adopted for low volatile coking (LVC) coal due to the high ash content associated washability characteristics and high near gravity material content. Attempt was made using laboratory Falcon SB40 concentrator for cleaning the LVC coals assaying 32.6% ash. Considering the physical properties, coal petrography and washability studies, as received coal was ground to three size fractions of –500 μm, –250 μm and –150 μm and subjected to separation in Falcon separator. Experiments were conducted using Design Expert software to evaluate the effects of four significant process variables such as feed size, pulp density, gravitational force value and water pressure. The relationship between the response functions (ash content, combustible recovery and separation efficiency) and process variables is presented as empirical model equations. Under the optimum operating conditions, LVC coal was cleaned to 18.4% ash content with 57.8% combustible recovery using Falcon concentrator.