| Coal dust pollutes air in the process of coal collection,loading and unloading,transportation,processing and use.When the dust concentration reaches a certain amount,it will cause serious coal dust explosion accidents,accelerate the wear of equipment and cause pneumoconiosis of coal miners.Therefore,the comprehensive prevention and control of underground dust and the reduction of various damages caused by coal dust are the key issues for scientific research workers.Among them,surfactant solution wetting coal dust is an important way of underground dust removal.However,the current wetting agents still have some shortcomings such as low dust removal efficiency,high cost and small application range,and lack of research on the mechanism of surfactant solution wetting coal dust.This paper conducts further research on the basis of previous studies,and the main research contents and conclusions are as follows:1.Three reagents,Primary Alcobol Ethoxylate(AEO9),sodium lauryl sulfate(SDS)and emulsifier(NP-10),with better wettability,were screened out from nine common surfactants by the improved sedimentation test method and the critical concentrations were screened out.On this basis,the three reagents were mixed experiments,and the critical concentrations of different proportions were screened out.Finally,it was found that the rate of SDS settlement experiment was the fastest with the mass fraction of 0.6%,followed by 0.4%AEO9 and 3:1 AEO9:NP-10solution with the mass fraction of 0.8%.In consideration of economy,0.4%AEO9 surfactant solution can be used as the optimal formulation of wetting dust suppressor.2.The surface tension of dodecyl trimethylammonium bromide(DTAB),sodium dodecyl benzene sulfonate(SDBS),lao-30 ammonium oxide(LAO-30)and AEO9 solution with mass fraction of 0.8%was measured.The equilibrium surface tension of the four reagents was as following:SDBS<AEO9<LAO-30<DTAB.The dynamic surface tension of four surfactant solutions was measured,and the modified Rosen formula was used to fit the dynamic surface tension.According to the fitting parameters,the order of the diffusion velocity of the four reagents from the bulk solution to the subsurface layer was DTAB<LAO-30<SDBS<AEO9.The rate of adsorption of surfactant molecules from subsurface to solution surface was DTAB<LAO-30<SDBS<AEO9.The diffusion of the four reagents is controlled by mixing kinetics.The order of the modified diffusion coefficient Da is:DTAB<LAO-30<SDBS<AEO9,which indicates that when the four surfactant solutions wet the coal dust,each molecule is combined with the coal dust previously,the movement speed of moving from the bulk phase to the subsurface layer in the aqueous solution,and then adsorbed from the subsurface layer to the surface layer of the solution was:AEO9 was the fastest,SDBS was the second,LAO-30 was slower,and DTAB was the slowest.3.The dynamic contact angles of DTAB,SDBS,LAO-30 and AEO9 solutions with mass fraction of 0.8%on the coal surface were measured,and the change rate constants of the contact angles were calculated.It was found that the change rate constants of the contact angles were consistent with the settling rate.4.The interaction forces between AEO9 surfactant solution and coal surface with concentrations of 5×10-5mol/L,8×10-5mol/L and 1.5×10-4mol/L were measured.It was found that the maximum repulsive force and the maximum gravitational force had obvious regularities,and the order of the maximum repulsive force and the maximum gravitational force was as follows:5×10-5mol/L>8×10-5mol/L>1.5×10-4mol/L.The equilibrium surface tension and the contact Angle between the droplet and the coal at the maximum repulsive force were also measured.The results show that with the increase of the solution concentration,the surface tension and contact Angle decrease,and the maximum repulsive force also decreases,indicating that the ability of the droplet to wetting coal dust is enhanced.At the same time,with the increase of AEO9 surfactant solution concentration,the surface tension decreases,which leads to the decrease of the droplet Laplace pressure,which makes the droplet more easily to be broken.In practical application,when the concentration of AEO9 solution increases,the dispersion of droplets also increases,thus increasing the probability of combining with coal dust particles and improving the efficiency of dust removal.In addition,the interaction between the droplets of AEO7,AEO9 and AEO12 solution with the concentration of 1.5×10-4 mol/L and the coal surface was measured,and the maximum repulsive force was AEO9<AEO7<AEO12,and the performance relationship of the three reagents for wetting coal dust was AEO9>AEO7>AEO12.However,the relationship between the surface tension of the three is AEO7<AEO9<AEO12,which is inconsistent with the relationship between the maximum repulsive force.However,the relationship between the measured contact Angle and the maximum repulsive force is consistent.This suggests that the contact Angle has a greater effect on the maximum repulsive force than the surface tension.The relationship of maximum gravity is:AEO9<AEO7<AEO12,then AEO9 is most easily dispersed into small droplets and combined with coal dust,so as to achieve a higher dust removal efficiency. |
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