Study On The Promoting Mechanism Of Inorganic Salt-surfactants On The Flotation Of Oxidized Coal Slurry

With the increase of coal mechanization and the change of coal seam,the slime is more and more difficult to float due to the formation of hydrophilic oxygen-containing functional groups and the formation of hydrogen bonds with water molecules.In recent years,many scholars have studied the flotation chemicals of slime and found that the use of certain surfactants can not only increase the hydrophilicity of the surface of the slime,but also produce the emulsifying effect on the collector and promote the surface adsorption to enhance the collection of collector,thereby enhancing the flotation efficiency and clean coal production.The flotation coal slime of this project used the hydrogen peroxide to oxidize of Tunlan Coal at room temperature.Flotation test before and after oxidation combustible recovery rate decrease by 13.63%,which indicates that the slime is oxidized and the hydrophobicity is deteriorated.Before and after the oxidation the FTIR of the slime showed that the absorption peak area of the-OH and-COOH increased from 3300cm-1 to 3650cm-1;the absorption peak area of C = C from 3010cm-1 to 3040cm-1 and benzene C-H from 3000cm-1 to 3100cm-1 decrease;the absorption peak area of the C=O from 1684 cm-1 to 1724cm-1 appear in the oxidized slime.The wetting heat of the slime before oxidation is 0.234Jg-1,after oxidation is 0.657Jg-1,indicating that the oxidized coal is more hydrophilic and is not conducive to flotation.Cationic?CTAB and DTAC?,anionic?SDS and SDBS?and nonionic?FM,TWEEN20,TWEEN80,OP-4,OP-13,PEG400 DO,ODEA and SPAN80?were selected from three different types of surfactants.The flotation test of Tunlan artificial oxidized slime was carried out,and the mechanism was analyzed by FTIR and wetting heat.The results showed that the anion-type SDBS had the best effect.When the dosage of SDBS was 300 g/t,the combustible recovery rate was increased by 14.56%,the clean coal ash was 9.13%,the tail ash was 31.53%;When the dosage of SDS was 300 g/t,the combustible recovery rate was increased by 12.99%,the clean coal ash was 9.19% and the tail ash was 26.67%.They can improve the clean coal yield and tail ash,with good selectivity to the oxidized coal,and enhance the flotation efficiency.Cationic CTAB and DTAC promoted the coal flotation obviously,second only to the anionic type.Nonionic surfactants have promoting effect.But when the dosage of OP-4 was 350 g/t,the combustible recovery rate was reduced by 38.16%,the clean coal ash was 7.67%,and the tail ash of coal was 11.23%,which restrained the flotation of the oxidized coal.SDBS,SDS,CTAB and DTAC were adsorbed on the surface of the slime,and the alkane chain increased the hydrophobicity of the slime surface.Nonionic surfactants?FM,SPAN80,ODEA?have emulsification,so that kerosene in the solution dispersed into small droplets,enhanced kerosene dispersion and collectable,improve the flotation effect.The wetting heat indicates that the promotion effect of the three types of surfactants was anionic> cationic> nonionic.MgSO₄,FeCl₃ and CaCl₂ were added to the flotation process of oxidized coal to study the effect of inorganic cation on the flotation of oxidized coal.The results showed that when the dosage of MgSO₄ was 500 g/t,the recovery of combustible was increased by 8.37%;When the dosage of CaCl₂ was 250 g/t,the recovery rate of combustible was increased by 3.89%;When the dosage of FeCl₃ was 50g/t,the recovery rate of combustible was increased by 4.60%.Therefore,the promotion effect of three ions is Mg²⁺> Fe³⁺> Ca²⁺.After adding Mg²⁺,the wetting heat was reduced by 0.114 Jg-1;After adding Fe³⁺,the wetting heat was reduced by 0.09 Jg-1;After adding Ca²⁺,the wetting heat was reduced by 0.028 Jg-1,and the three inorganic ions can reduce the hydrophilicity of oxidized coal,and their hydrophobicity effect of oxidized coal was Mg²⁺> Fe³⁺> Ca²⁺.Finally,inorganic cation and surfactants were added in the process of oxidizing coal flotation to study the common effect of inorganic salt-surfactant on flotation of oxidized coal.The flotation results showed that the flotation efficiency of SDBS and SDS was decreased when the three inorganic salts of MgSO₄,CaCl₂ and FeCl₃ were added;PEG400DO and TWEEN80 can promote the flotation of oxidized coal;The restraining effect of OP-4 on the oxidation coal is stronger.Addition of magnesium sulfate,the FTIR results showed that the oxygen-containing functional groups of SDBS and SDS were increased,and the hydrophobicity was weakened.The oxygen-containing functional groups of PEG400 DO and TWEEN80 were reduced and the hydrophobicity was enhanced.The hydrophilicity of OP-4 was enhanced.The wetting heat of SDBS and SDS was increased,the wetting heat of PEG400 DO and TWEEN80 was decreased,and the wetting heat of OP-4 was increased,which was consistent with the flotation tests.