Study Of Benefication And Purification On Hard Kaolin From Coal Tailings

Coal-series kaolin is a kind of particular kaolin mineral resource in China,thekaolin usually disseminates in coal measures parting and coexists with it.During coalmining and processing,coal gangue was abandoned and piling as tailings,which notonly ruined the environment but also was a huge waste of non-metal mineralresource.Coal-series kaolin generally own carbon、iron and titanium impurities more orless,calcinations、flotation、classification and maganetic separation are the mostcommon-used processing techniques.Because calcined coal-series kaolin productpossesses more single mineral composition,purer chemical components,better fireresistance,dispersion, chemical stability and insulating performance, it can be appliedin much more widely industrial fields than washed kaolin.The chemical composition and crystal structure of coal series kaolin of InnerMongolia has been analyzed by means of X-ray diffraction, X-ray fluorescencespectrum, polarizing microscope, and reflective microscope in this paper. Resultsshow that the main mineral is kaolinite, and the main impurities are silicates,iron-bearing minerals, titanium-bearing minerals and organic carbon. Mineralprocessing mainly aims to improve the aluminum content, and remove the silicate,iron-bearing minerals, titanium-bearing minerals and organic carbon, hoping to gethigh quality kaolin products finally.Aiming at explore a specific flow to get high quality kaolin products in view ofthe properties of the impurities and purpose mineral. By using classification methodwe suppose to remove the hard grinding siliceous mineral in kaolin. Iron and titaniummagnetic minerals were removed through magnetic separation. Iron sulfide wasremoved by floatation, which achieve a better result during the removal of iron. Theorganic carbon can also been removed by flotation. The experiments resultsconfirmed that through ore grinding, castigation, flotation, magnetic separation andcalcinations we can satisfy the requirement of high whiteness of the kadoliniteproduct. Through the grinding particle size analysis, we concluded that the best flotationseparation grinding fineness is-0.074mm90.03%,-0.045mm83.57%The bestreagent regime for flotation is as following (1)carborn removing stage: kerosene600g/t, terpilenol oil150g/t,sodium silicate2500g/t;(2)iron removing stage: xanthate120g/t,terpilenol oil120g/t.The best calcination regime is as following:1)calcinationtime:4h；2)atmosphere: reducing；3) calcination temperature:950℃；4) the dosageof NaCl:2%by weight.The original kaolin ores possess Al2O327.90%, Fe2O30.94%, TiO20.90%,calcination product whiteness69%. Through the beneficiation tests we can get kaolinconcentrate with Al2O334.65%, Fe2O30.58%, TiO20.53%, Al2O3recovery65.60%and the calcinations product whiteness84.20%. These results meet the nationalstandard of enamel industry, rubber and plastic industry.Analyses suggest that carbon impurities contained in the kaolin ore samples,mostly as coal particles.Kerosene distributied in the ore pulp as oil drop, co-adhesionwith coal particles and floating as oil group; Xanthate collects pyrite during flotationmainly adsorping as bixanthate and metal-xanthate.Molecue adsorption and chemicaladsorption both exists, but which of them is dominant is the responsibility of the pulpenvironment; Sodium chloride (NaCl) whitening effect mostly contributed to chloridegas(Cl2). On the one hand, Cl2recated with Fe2O3and TiO2and generated low boilingpoint resultant (FeCl2, FeCl3and TiCl4). Such low boiling point resultant volatiled inhigh-temperature atomosphere, which largely reduced impurities content.On the otherhand, melting Sodium chloride coated on the surfaces of kaolinite, shielding thecolouring ions and increasing its whiteness.