Experimental Study On The Effect Of The Hydrophilicity Of Dust Particles On Their Removal Efficiency In A Gas Cyclone With Atomized Water Vapor

The newly released“National Air Quality Status in 2017”shows that the air quality in the country has been effectively improved,but atmospheric fine particulate matter pollution is still serious in some areas,especially in the industrial fields represented by petrochemicals,steel,and cement.However,there is a considerable lack of efficient and economical processing technologies for industrial PM_2.5.The technology combined electro-acoustic transducer ultrasonic atomization and cyclone is a new type of dust removal technology.Micron-sized droplets and dust particles continuously collide and agglomerate in the disturbed flow field to form larger dust-containing droplets.The particle size of the fine particles continuously increases,and the fine particles with the increased particle size are efficiently removed under the effect of high gravity.In this paper,the effect of hydrophilicity of dust particles on their removal efficiency in a gas cyclone with atomized water vapor was studied by experiments.The water vapor was generated by electro-acoustic transducing ultrasonic atomization technique.Several kinds of industrial dust with different hydrophilicities were injected in the cyclone and their removal efficiencies were measured and compared.In addition,the effects of two important operating parameters,inlet flow rate and inlet concentration,on removal efficiency were experimentally studied.The results showed generally the removal efficiency will increase with water vapor added to the cyclone.Such increase will be more significant for more hydrophilic dust particles.Typically,the removal efficiency of the talcum powder increased from 76.9%to 90.1%by 13.2%when 4 g/m³ vapor was added.However,for the S-zorb desulfurization catalyst with poorer hydrophilicity,the increase was only 8.0%with the same amount of vapor.The effect of hydrophilicity was especially manifested in fine particles with diameter about 2.5?m.The highest increase of the removal efficiency of the talcum powder appeared at particle size 2?m,which was from 31.5%to 72.8%with4 g/m³ vapor added,while the highest increase of that of the S-zorb desulfurization catalyst was only from 43.9%to 61.6%at particle size 2.3?m.Moreover,the dust particles before and after the cyclone were examined by scanning electron microscopy?SEM?images,and the results confirmed the hydrophilicity has a significant impact on the agglomeration and growth of particles,which should be responsible for the difference in the removal efficiency of different particles.In addition,the inlet flow rate and the inlet concentration all have an important influence on the atomization-centrifugal removal efficiency.The increase of the inlet flow rate within a certain range will increase the removal efficiency.Adding the mist can make the removal efficiency still have a high growth rate at a high inlet flow rate,and the hydrophilicity of the dust particles is better and the increase speed is greater.Simultaneously,the more hydrophilic particles can reduce the pressure drop at high inlet flow rates and reduce energy consumption.The increase of the inlet concentration within a certain limit is conducive to the improvement of the removal efficiency,and is particularly advantageous for the improvement of the removal efficiency of fine particles in the vicinity of 2.5?m.However,when the inlet concentration exceeds a critical value,the removal efficiency decreases as the inlet concentration increases.The performance is that the removal efficiency is approaching when there is no fog,and the hydrophilic particles with better hydrophilicity have a slower approach speed.In addition,the pressure drop decreases significantly with the increase of the inlet concentration.The dust particles will reduce the cyclone intensity inside the cyclone dust collector and also form a particle layer on the inner wall of the cyclone dust collector,which are beneficial to reduce the energy loss.These studies could help optimize and improve the cloud-air-purifying?CAP?technology that combines gas cyclone with atomized water vapor technologies,and extend its versatility to industrial applications for decreasing the emission of PM_2.5.