Experimental Study On Wetting Characteristics Of Coal Dust And Efficiency Of Spray Dustfall

With the improvement of coal mining technology and the deepening of mechanization in China,the problem of coal dust is becoming more and more serious.Coal mine dust is not only explosive,but also the main cause of pneumoconiosis.In China's coal mines,spray dust control technology has been used to control dust.Some achievements have been made,but the dust concentration of most working flour is still very bad.In order to reduce the dust concentration of coal face,reduce the probability of accidents and ensure the life and health of coal mine workers,the wettability and spray dust control technology of coal are studied.The paper mainly studies the influence of coal quality,coal particle size and surfactant on coal wettability,and applies the research results to spray dustfall,and discusses its relationship with the efficiency of dustfall.The following conclusions are drawn:(1)Coals of different coal qualities have similar chemical structures,but their composition proportion is different,and the surface functional groups are different;the oxygen functional groups on the surface of coal dust decrease gradually with the increase of coal metamorphism,and the surface of coal is gradually smooth with the increase of coal quality;when anthracite is ignored,the wettability of coal dust can be determined by the content of oxygen functional groups on the surface of coal dust.The less oxygen functional groups,the stronger the wettability.The contact angle of coal dust is inversely proportional to the moisture absorption of coal.Therefore,the method of reverse osmosis moisture absorption is credible.Under limited conditions,this simple method can be used to measure the wettability of coal dust.(2)The particle size of coal dust has great influence on the oxygen-containing functional groups,specific surface area and average pore size of coal.With the decrease of particle size of coal dust,the average pore size of coal dust increases gradually,while the average pore size of coal dust decreases continuously.The content of hydrophilic oxygen-containing functional groups on the surface of coal dust decreases continuously.Anthracite has very few oxygen-containing functional groups on its surface due to long-term geological action.Therefore,with the change of particle size of coal dust,its oxygen-containing functional groups are very small.The wettability of coal dust decreases with the decrease of particle size of coal dust.(3)Surfactants can effectively improve the surface tension of the solution,and when the concentration exceeds its critical binding concentration,the surface tension will not decrease;anionic electrolytes can effectively improve the wettability of anionic surfactants,but have no beneficial effect on non-ionic surfactants;surfactants have different wettability for coal of different coal qualities,and the worse the wettability of coal is.The better the wetting effect is,the worse it is anyway.The wetting ability of surfactants to different particle sizes of coal dust is basically the same,and there is no sudden change with the particle size of coal dust.(4)the efficiency of spray dustfall is related to the degree of metamorphism of coal.When the degree of metamorphism of coal is low,the efficiency of dust removal is higher.With the increase of metamorphism,the efficiency of dust reduction gradually decreases,and when the coal quality is increased to anthracite,the efficiency of dust removal is increased.The contact angle is negatively correlated with the efficiency of dust fall.The larger the contact angle and the lower the efficiency of dust fall,we can analyze it according to the size of contact angle.The efficiency of dust reduction is not affected by increasing water supply pressure for coal with better wettability,but it can be improved by increasing water supply pressure for coal with worse wettability.However,with the further increase of water supply pressure,the change of dust reduction efficiency is not obvious after the change of fog droplets is not obvious.(5)the efficiency of spray dustfall is closely related to the wetting performance of coal dust.When the particle size of the dust particles is equal and the spray condition is constant,the efficiency of the spray dust reduction is higher.When the coal quality and spray condition are certain,the efficiency of the spray dust is determined by the wetting property of the coal dust and delta D50.With the increase of the particle size of the coal dust,the efficiency of the spray dust reduction is the first.In order to improve the efficiency of spray dustfall,the water supply pressure is adjusted according to the particle size distribution of the dust.(6)by reducing the surface tension of the solution,the surfactant can make the solution easier to be refined into smaller droplets and increase the probability of droplets catching the dust.However,due to the factors influencing the dust removal efficiency,the efficiency of the surfactant is limited.When the concentration of surfactant solution reaches cmc value,increasing the concentration is not conducive to improving the ability of spray dust suppression.It is suggested that when the surfactant is used for spray dustfall,the concentration below CMC should be selected to achieve the best dustfall efficiency.