Effects Of Electrochemical Action On The Dispersion And Flocculation Flotation Of Coal Slurry

Flotation is the main method of fine coal processing in most coal preparation plants.The reduction of high-quality coal resources and the increase in the proportion of fine particles result in the deterioration of floatability.Thus,the flotation efficiency is greatly affected.However,dispersion-flocculation can reduce the coverage of fine slime on the surface of coal particles and mitigate the entrainment of impurities in flocs.Electrochemical pretreatment can improve the floatability of minerals and promote the performance of dispersant and flocculant.Therefore,the combination of electrochemical pretreatment,dispersion and flocculation method has practical significance on improving the flotation efficiency of fine low-rank coal.In this paper,the weakly caking coal produced in Pingshuo mining area was used.The basic properties of this coal sample were studied at beginning.Then,the effects of electrochemical pretreatment on the dispersion-flotation,flocculation-flotation and dispersion-flocculation-flotation were researched.Finally,indicators such as particle size,contact angle,zeta potential,viscosity of coal sample pretreated by electrochemical actions were measured to helpanalyze the mechanism of electrochemical pretreatment.The main conclusions obtained from this study are:1.In the dispersion-flotation test,flotation efficiency based on sodium hexametaphosphate,sodium pyrophosphate,sodium hydroxide,sodium fluoride and tannic acid at the dosage of 1100g/tdry slime are compared.Results show that the best flotation efficiency is obtained by using sodium hexametaphosphate as dispersant.The optimum pH value is 6.2.The results in electrochemical pretreatment dispersion flotation test show that dispersion-electrochemistry method is better than electrochemistrydispersion method.Flotation efficiency obtained by using NaCl as electrolyte in dispersion-electrochemistry flotation test is better than that obtained by using MgCl₂ or AlCl₃.For the case of NaCl,the clean coal yield,ash and flotation perfect index are 48.56%,10.68% and 33.32%,respectively.3.In the dispersion-flotation test,flotation efficiency based on anionic 6million PAM,anionic 12 million PAM,cationic 6 million PAM,cationic 12 million PAM,non-ionic 6 million PAM,and non-ionic 12 million are compared.The molecular weight of PAM is measured by viscosity method.Results show that the best flotation efficiency is obtained by using anionic 6 million PAM as flocculant.The optimum pH value is 8.4.The results in electrochemical pretreatment flocculation flotation test show that electrochemistry-flocculation method is better than flocculationelectrochemistry method.Flotation efficiency obtained by using AlCl₃ aselectrolyte in electrochemistry-flocculation flotation test is better than that obtained by using MgCl₂ or NaCl.For the case of AlCl₃,the clean coal yield,ash and flotation perfect index are 59.87%,13.30% and 32.14%,respectively.5.In the selective flocculation test,at the case of dosage of sodium hexametaphosphate 1100g/tdry slime and anionic 6 million PAM 30g/tdry slime,the optimum pH value is 8.6.The results in electrochemical pretreatment selective flocculation flotation test show that dispersion-electrochemistry-flocculation method is better than dispersion-flocculation-electrochemistry method.Flotation efficiency obtained by using NaCl as electrolyte in dispersion-electrochemistryflocculation test is better than that obtained by using MgCl₂ or AlCl₃.For the case of NaCl,the clean coal yield,ash and flotation perfect index are 56.98%?11.05% and 37.89% respectively.7.In conclusion,the flotation efficiency of electrochemistrydispersion-flocculation method is better than that of electrochemistry-dispersion and electrochemistry-flocculation method.At the case of dispersionelectrochemistry-flocculation method,indicators such as particle size,wettability and adsorptivity are improved.Therefore,the yield of clean coal increases,and the ash of clean coal decreases.