Study Of Wetting Characteristics Of Coal Body Active Agent Based On Surface Roughness

The wetting performance of coal is very important for wet dust removal.The factors that affect the wetting effect of water on coal include the hydrophilicity(composition,moisture content,etc.)of the coal itself,the microstructure of the coal surface(roughness,etc.),and surfactants.Among them,the hydrophilicity of coal itself cannot be changed during the wetting process of the coal body.Only by changing the microstructure of the coal surface and adding a surfactant in water,the wetting performance is affected.Therefore,this article starts with the roughness of coal surface,and takes Hami lignite,Anyang coking coal and Zhaogu Second Mine anthracite as research objects,analyzes the contact angle of pure water and surfactant-containing solution under different roughness,and then analyzes the change of wetting performance.characteristic.Firstly,the roughness of the fracture surface and the sandpaper treatment of 120,240,320,600,and 1000 mesh were analyzed.The results show that the roughness is related to the degree of coal deterioration and the firmness coefficient.Among them,Hami lignite has a low degree of metamorphism,a complex surface structure,and a large roughness,with a value of about 8.54 μm.The value is about 4.52 μm;coking coal is in between,and the value is 6.14 μm.After processing coal samples with sandpaper,the roughness of each coal sample decreases with the increase in the number of sandpaper meshes.When the sandpaper mesh number is 120-320,the difference in roughness of the three coal samples is large,and when the sandpaper mesh number is 600-1000,the difference decreases,but the overall roughness is lignite> coking coal> anthracite.Secondly,wetting tests and surface energy analysis were performed on coal surfaces with different roughness.Hami lignite and Zhaogu No.2 anthracite are hydrophilic,and the contact angle gradually decreases with increasing roughness,while Anyang coking coal is hydrophobic,and the contact angle gradually increases with increasing roughness,which belongs to the fully wetted Wenzel model.Using two liquids,deionized water and glycerol,the surface energy of three coal samples was calculated by the OWRK method.Among them,the lignite coal has the largest surface energy,followed by anthracite,and the coking coal has the smallest.At the same time,the surface energy of each coal sample varies with roughness The law is consistent with the wetting change law in the Wenzel model,which confirms the influence of roughness on wetting from the perspective of energy.Using COMSOL Multiphysics version 5.3a,wetting conditions of wetted surfaces with different hydrophilicities under the influence of roughness,the simulation results also conform to the Wenzel model,but the values are different,the difference is caused by the hysteresis of the contact angle.The hydrophilic value is good,and the hysteresis is small,so the simulation value is larger than the experimental value;the hydrophobic value is good,and the hysteresis is large,so the simulated value is smaller than the experimental value.Finally,6 kinds of surfactants were selected: AOS,SDS,CTAC,1227,OP-10 and AEO-3,which were respectively configured into three concentrations of 0.1wt%,0.2wt%,and 0.3wt%.The surfactant-containing solution was used for experiments.Wetting of three coal samples with different roughness surfaces showed that the best effect on Hami lignite is anionic surfactant SDS with a concentration of 0.2wt%;the best effect on anyang coking coal and Zhaogu Second Anthracite is non-ionic surface Active agent OP-10,concentration 0.3wt%;the wetting condition of each coal sample still conforms to Wenzel’s theoretical model,but the solution containing surfactant does not respond well to the roughness of pure water.The difference is only in the range of 10 °,so it is considered that the effect of roughness on wetting is weakened in the case of containing a surfactant.At the same time,the wetting of the surfactant-containing droplets was simulated.The simulation results showed that the change in surface tension did not affect the wetting of hydrophilic and hydrophobic surfaces under different roughness without considering the interaction between the surfactant and the coal surface.The rule is that the contact angle of Hami lignite still decreases with the increase of roughness under the condition of changing droplet properties,and the contact angle of Anyang coking coal still increases with the increase of roughness.The trend is the same.The contact angle of the three coal samples and the surface tension under the action of different concentrations of surfactants have the same trend.The larger the surface tension,the larger the contact angle.Among them,the surfactant AEO-3 has the most obvious decrease in surface tension of pure water,so the contact angle is also minimal.