The Influence Factors Of Coal Surface Wettability

18 kinds of coal from different regions with different coal seam,different ash,and different degree of coalification were adopted to investigate the contact angle by JC2000C1 contact angle dynamic measuring instrument in this paper.The contact angle was used to characterize the wettability of coal and the changes of contact angle of coal were analyzed from two aspects,which were intrinsic factors(basic characteristics of coal)and external factors(surface active agent).Firstly,the influence of internal factors on contact angle of coal was investigated.The proximate analysis,ultimate analysis,vitrinite reflectance,infrared spectroscopy,laser particle size analyzer and other means were used to characterize the metamorphic degree,chemical composition,oxygen containing functional groups,fractal dimension,surface area and other properties of the prepared experimental coal sample,respectively.Then it analyzes the correlation between the basic characteristics and the contact angle of coal.The results showed that:(1)The chemical composition of coal has a great influence on its wettability.Ash content,moisture content and oxygen content are negatively correlated with the contact angle.While fixed carbon,carbon content and hydrogen content are positively correlated with contact angle.(2)With the increase of coal rank,the contact angle becomes larger and the hydrophilicity decreases.(3)The oxygen containing functional groups of coal have a great influence on surface wettability.The 910-940cm-1 hydroxyl deformation vibration and 3400-3450 cm-1 aromatic hydroxyl stretching are measured as mainly hydrophilic groups,and the hydrophilicity of coal increases with the increase of the total peak area of the oxygen functional groups.(4)The distributions of coal particle size exhibit typical fractal characteristics.With the decreases of coal particle size D10,D50,D90,the fractal dimension increases,the contact angle becomes larger,and the wetting property becomes poor.The contact angle increases with the increase of the surface area,while the wetting property becomes poor.Based on the research and analysis above,the characteristic parameters and contact angle of coal were analyzed by multiple stepwise regression analysis.The best regression equation: =44.001+0.281[w(C)]+3.449[Romax].Then the effect of external factors on the contact angle of coal was studied.The contact angle and surface tension of different kinds of surfactant,different concentrations of surfactant,surfactant remixed with salt as well as surfacetant remixed were measured to investigate the wettability.It was found that:(1)Surfactant agent modified solution can improve wettability in great extent.In the same concentration of surface active agent,the wetting ability follows the sequence of A > B > C > SDS > Tween80 > JFC.(2)For the same surface active agent,the greater the concentration,the smaller the contact angle.(3)For the anion active agent(A,C)remixed with NaCl,the contact angle becomes smaller and the wettability is improved.The variation of contact angle of nonionic surfactant(JFC,Tween80,SDS,B)remixed with NaCl is not obvious or larger.(4)The effect of the compound after combination is not necessarily better than the effect before the combination of different nonionic surfactant and anionic surfactant...