Dry Deshaling of Thermal Coals in India

by Nikhil Gupta

Institution: Virginia Tech
Department: Mining and Minerals Engineering
Degree: MS
Year: 2011
Keywords: density separation; coal deshaling; air-tables; DEM modeling
Record ID: 1915354
Full text PDF: http://scholar.lib.vt.edu/theses/available/etd-11082011-160220/


Beneficiation of thermal coal in India is a relatively new development. For the year 2006, India produced 380 million metric tons of thermal coal, of which only 17 million metric tons were beneficiated coals. One potentially attractive method for upgrading Indiaâs coal feed stocks is the air table dry deshaling technology. Dry deshaling offers significant advantages over wet cleaning operations, including reduced surface moisture, enhanced heating value, elimination of processing water and waste slurries, and reduced transportation of large amounts of ash-forming minerals. To evaluate this potential, a pilot-scale air table deshaling unit was tested at three locations in India for the specific purpose of upgrading thermal coals. The field testing confirmed that the separation performance for Indian coals is similar to that which has been achieved at sites in the United States for material in the 50 x 6 mm size range. The data indicate that material with 80% ash and higher can be rejected by the dry deshaler unit with a combustible recovery of more than 90%. Furthermore, a discreet elemental model was developed using PFC3D to understand the process of segregation on a dry density based vibratory table. Analysis was done to show the effect of different forces on the process efficiency. Also, operating parameters and particle properties such as frequency of vibrations, amplitude of velocity, bed depth, particle size and specific gravity were analyzed in the model. The model results were compared with field testing results of dry deshaling air table and All-Air Jig separator.