Contact Electrification and Electrostatic Separation of Ashforming Minerals from High Ash Non-coking Coal Using Novel Fluidised Bed Tribo-charging System
The electrostatic beneficiation of coal is based on tribocharging characteristics of ash forming minerals and coal particles.The tribocharging of quartz,pyrite and coal particles contacted with various metals and polymeric materials have been measured and the charge acquisition is assessed through surface energy calculations from liquid contact angle data.The contact angles,before and after tribocharging of solids,are measured using Krüss tensiometer and Washbums method where the sample holders in tensiometer are specially constructed with tribocharger materials.The charge polarity and amount of charge acquired by quartz,pyrite and carbon with metal tribochargers were found in good agreement with the reported work functions of the contacting surfaces.The charge results with polymer materials differed from the work function values,presumably caused by surface contamination.The surface energy of quartz calculated by all the theoretical approaches in the literature showed that the tribocharging increases the surface energy.Both polar and non-polar components computed from Fowkes and Owens-Wendt-Rabel-Kaelble approaches display that both these components increased after triboelectrification.However,the polar component divided into acid and base components,as in van Oss approach,manifest decreasing acid part and increasing base part.Since quartz charged negatively during tribocharging with metal surfaces and therefore accepted electrons,the determined acid and base surface energy components are consistent with charge transfer process.The results also elucidate an explicit correlation between the charges generated by powders and the surface acceptor (acid) and donor (base) electronic states and thereby the work functions.A novel fluidized bed tribo-charger was designed and developed with internal baffle system for efficient contact electrification of mineral and maceral to produce high differential charging for efficient separation.The results achieved on coal with 45% ash content are presented and discussed.
Coal preparation Tribo-electrostatic separation Triboelectrification Fluidised bed tribocharger Contact angle Surface energy
R.K.Dwari K.Hanumantha Rao
Division of Mineral Processing,Lule(a) University of Technology,Sweden
国际会议
XXIV International Mineral Processing Congress(第24届国际矿物加工大会)
北京
英文
3540-3550
2008-09-24（万方平台首次上网日期，不代表论文的发表时间）