Fundamental Study On The Application Of Nonionic Compound Collectors In The Flotation Of Low-rank Coal Slime

A large amount of primary and secondary inferior slime are produced in the process of mechanical large-scale mining,washing and upgrading of low-rank coal,which has the characteristics of fine particle size,high moisture,high ash content and high viscosity,so it is very difficult to dispose.Flotation is the most economical and effective way to improve the quality of fine slime.However,when traditional hydrocarbon oil is used as a collector,on the one hand,it is difficult to effectively improve the floatability of coal particles on the surface of low-rank coal particles.On the other hand,in the flotation process,there is a high proportion of fine high-ash ore material entrainment with water into the clean coal products,resulting in poor separation effect.The engineering practice shows that the collector is the core technical bottleneck restricting the flotation quality improvement and classification utilization of low-rank slime,and the development of high-efficiency collector suitable for low-rank slime flotation is an urgent technical problem to be solved in the current research on comprehensive utilization of low-rank slime.This paper takes the compound nonionic collector as the focus,and takes the artificial mixed low-rank coal slime(Shendong low-rank ultra-pure coal + nonexpansive kaolinite,Shendong low-rank ultra-pure coal + expansive montmorillonite)as the research object.The effects of compound nonionic collectors on clean coal yield,ash and combustible recovery were studied,and the entrainment behavior of two kinds of clay minerals under different compound collectors were investigated.The mechanism of the interaction between the compound nonionic collector and low-rank coal particles was discussed by testing and analyzing the dispersion of the reagent,the interfacial tension of the reagent,the wetting heat of the reaction between the reagent and the coal sample and the change of the contact angle of the coal sample after treatment.The internal causes of different entrainment behaviors of two kinds of clay minerals were analyzed by entrainment theory calculation and image method.The coal samples used in this test are artificially mixed low-rank coal slime,which is prepared by mixing Shendong low-rank ultra-pure coal,pure kaolinite minerals and pure montmorillonite minerals according to the mass ratio of 2:1.The content of loworder ultra-pure coal ash is 2.41%.The particle fraction of-74 ? m accounts for 73.12%of the total particle size.The surface is rich in oxygen-containing groups,and the hydrophobicity is poor.The purity of kaolinite is 98% and the content of-20 ? m mahogany is 78.95%.The purity of montmorillonite is 96% and the content of-20 ?m of montmorillonite is 78.52%.The ash content of kaolinite mixed coal sample is 34%,and that of montmorillonite mixed coal sample is 32%.The results of the tests on the dispersibility of collector in water,interfacial tension of collector,wetting heat after the action of collector and coal sample,and contact angle after the collector modified coal sample are analyzed.It is found that the dispersion of the compound collector is better,the interfacial tension is lower,the wetting heat value after the action with coal sample is larger,and the contact angle increases more obviously after modification,It is shown that the compound collector can effectively improve the hydrophobicity of the surface of low-rank coal,increase the chance of contact with the coal sample surface,and is more conducive to the adsorption of the collector droplets on the coal surface,and the higher the degree of action with the coal surface,and is more conducive to the flotation test.The mechanism of the compound collector on the surface of low-rank coal verifies the effect of the collector on the combustible recovery of flotation clean coal.Under the same reagent condition,the flotation cleaned coal ash content of the compound collector is lower than that of kerosene,and the cleaned coal ash content decreases with the increase of the concentration of active agent in the collector.The comprehensive results show that the cleaned coal ash is determined by the recovery amount of combustible and gangue entrained.The three reagents all make more gangue entrainments into the cleaned coal.However,under the action of reagents,the recovery amount of combustible increases more significantly,accounting for a larger proportion in the cleaned coal,so the ash content of cleaned coal decreases as a whole.In the process of flotation,the two kinds of clay minerals show different gangue entrainment behavior.Under the same reagent condition,the gangue entrainment recovery and gangue entrainment rate of flotation kaolinite mixed slime are higher than that of montmorillonite mixed slime.For kaolinite mixed slime,the recovery rate of gangue entrainment is the highest,that of compound OP-4 is the second,and that of compound ODEA is the lowest.For montmorillonite mixed slime,the entrained recovery of montmorillonite showed different regularity under the low,medium and high dosage of different compound agents.In addition,the difference of entrainment behavior between the two types of clay minerals is related to their own properties.In the flotation system,there is no structural connection between clay mineral particles and low-rank coal particles,and the entrainment degree of kaolinite is high,while the entrainment degree of montmorillonite is low.There are 50 figures,7 tables and 97 references in this paper.