Study On Desulfurization Of Coal By Ultrasonic Electrochemical Flotation Under Acidic Conditions

China is rich in coal reserves,of which Xinjiang occupies about 40%,ranking first in China.Therefore,it is necessary to exploit and utilize Xinjiang coal.In this paper,the coal in various regions of Xinjiang is taken as the research object,and the phase screening and correlation analysis of coal samples are carried out,Ultrasonic and electrochemical technology is applied to coal flotation desulfurization technology.The main research contents and results of this paper are as follows:（1）The removal of sulfur and other harmful elements in coal is enhanced by flotation through ultrasonic cleaning,cavitation and electrochemical REDOX.Firstly,the single factor method was used to investigate the influence of sulfuric acid concentration,electrolytic temperature,current intensity,electrolytic time and other factors on the desulfurization effect of coal sample.Further,through the orthogonal experiment of four factors and three levels,the optimal combination of each factor on the desulfurization of coal sample was determined.The optimal condition is:Sulfuric acid concentration 5.5×10^-3mol/L,electrolytic temperature 30℃,current intensity 78×10^-3A/cm²,electrolytic time 30 min.The highest cleaned coal yield of 90.98%,desulfurization rate of 65.97%,pyrite sulfur reduced by 95.91%,sulfate sulfur reduced by90.0%,organic sulfur reduced by 37.50%,Hg reduced by 80.0%,Pb reduced by 20.0%,ash reduced by32.75%,ash K₂O reduced by 14.89%.Na₂O in ash decreased by 27.78%.Moisture decreased by 20.53%,volatile content increased by 3.65%,calorific value increased by 5.12%,C decreased by 0.22%,H increased by 9.55%.Infrared,morphological sulfur and X-ray diffraction analysis show that ultrasonic electrochemical enhanced flotation can effectively increase the surface contact Angle and improve the yield of cleaned coal.Electrochemical oxidation removes pyrite sulfur and organic sulfur,H replacement,electrochemical reduction removes mercury and lead,and flotation removes inorganic sulfur,ash,K₂O and Na₂O in ash.（2）The desulfurization effect of coal with different particle sizes is different.Under the optimal conditions of different granular coal desulfurization and ash experiments,the morphological sulfur and ash content of different granular coal samples before and after ultrasonic electrochemical flotation were determined.The results show that the smaller the coal sample size,the higher the flotation refined coal yield,the more significant the desulfurization and deashing effect.The coal sample with<0.075 mm has the best desulfurization and deashing effect.The flotation yield can reach 93.05%,the total desulfurization rate is72.97%,the pyrite sulfur is reduced by 89.12%,the sulfate sulfur is reduced by 64.23%,the organic sulfur is reduced by 59.11%,and the deashing rate is 41.17%.Infrared（FT-IR）,X-ray diffraction（XRD）and morphological sulfur analysis show that ultrasonic electrochemical treatment can improve the surface properties of coal samples,increase the contact Angle,improve the flotation refined coal yield and remove various forms of sulfur and hydrophilic minerals easy to become ash in coal.（3）Different electrolytes have different effects on sulfur and ash in coal.Ultrasonic and electrochemical enhanced flotation methods are used to explore the gradient removal effect of sulfur and ash in coal under different electrolytes.Under the best conditions,the flotation kinetics experiment on the coal sample was carried out.The results showed that the ultrasonic electrochemical treatment could reduce the flotation time and improve the flotation yield,that is,obtain more cleaned coal in a small flotation time.Gradient ultrasonic electrolysis was carried out on coal samples with sulfuric acid,hydrogen peroxide and sodium hydroxide to explore the effect of different electrolytes on the removal of sulfur and ash in coal samples at different stages of ultrasonic electrolysis.The results show that different electrolytes can remove sulfur from coal,but only sulfuric acid electrolytes can remove ash from coal,and other electrolytes have little effect on ash removal.In addition,Kuqa bituminous coal,Kuqa cleaned coal and Jundetu raw coal are selected to explore the ultrasonic electrochemical flotation desulfurization and deashing effects of different coals.The experimental results show that Kuqa bituminous coal has the best yield,desulfurization and deashing effect,with yield of 82.98%,desulfurization rate of 85.17%and deashing rate of 65.35%.（4）Different coals have different desulfurization effects under the influence of different factors.Through orthogonal experiments of ultrasonic electrochemical flotation of different coals,the optimal conditions for desulfurization of different coals are explored.The results are as follows:the optimal desulfurization conditions for Kuka bituminous coal are sulfuric acid concentration:5.5×10^-3mol/L,ultrasonic electrolysis temperature:30℃,current density:78×10^-3A/cm²ultrasonic electrolysis time:35 min,the desulfurization rate is 85.71%,clean coal yield is 87.91%.The optimal desulfurization conditions for Kuche cleaned coal are as follows:sulfuric acid concentration:3.7×10^-3mol/L,ultrasonic electrolysis temperature:40℃,current density:78×10^-3A/cm²,ultrasonic electrolysis time:30 min.Under these conditions,the desulfurization rate is 71.43%,and the cleaned coal yield is 67.66%.The optimal desulfurization conditions of Junde Tu raw coal are as follows:sulfuric acid concentration:3.7×10^-3mol/L,ultrasonic electrolysis temperature:30℃,current density:58×10^-3A/cm²,ultrasonic electrolysis time:40 min.Under these conditions,the desulfurization rate is 25.34%,and the cleaned coal yield is 70.55%.At the same time,through the ultrasonic electrochemical desulfurization kinetics experiment of Kuqa bituminous coal,it is found that the desulfurization rate has an exponential relationship with time,and the longer the time,the lower the desulfurization rate until the sulfur in coal no longer changes.Under acidic conditions,ultrasonic wave and electrochemistry have a great influence on the flotation,desulfurization and desaylation of coal,which can not only improve the surface properties of coal samples and improve the flotation efficiency,but also optimize the particle size composition of coal samples to strengthen the effect of coal desulfurization and desaygation.