Experimental Study And Mechanism Analysis Of Compound Coal Dust Wetting Agent

Coal dust is one of the main hazards in the process of coal mine production,which seriously affects the production of coal mine and the health of coal miners.Water spray is the main way of coal mine dust removal at present.Surfactant is often used as water spray additive to improve the wetting ability of water.However,single surfactant has limited wetting ability and its added concentration is high.To improve the effect of surfactant wetting coal dust and reduce its addition cost,in this paper,on the basis of the surfactant influence on wettability of coal dust,from the change of water surface tension and the influence of coal surface hydrophobicity two aspects to study the compounding of wetting property between surfactant,inorganic salt and surfactant wetting properties,has a synergistic effect or promotion effect for the preparation of wetting agent,comprehensive experimental results and theoretical analysis the surfactant compound with collaborative wetting mechanism of coal dust and inorganic salt on the mechanism of surfactant wetting effect of coal dust.The effects of surfactants on the surface tension of water and the surface hydrophobicity of coal dust were investigated by means of interfacial shear rheometer and X-ray photoelectron spectroscopy（XPS）.The surface tension of surfactant solution decreases exponentially with increasing concentration.The critical micelle concentration（CMC）of surfactant is analyzed according to the first derivative curve of surface tension with respect to concentration.The peak fitting results of XPS C1s spectrum showed that the relative content of hydrophobic functional groups and the hydrophobicity of coal dust treated with surfactant decreased compared with that of water treated coal dust.The wetting properties of surfactants were studied by surface tension and other parameters.The results show that the compound of anionic surfactants mainly has wetting antagonism.The combination of anionic surfactant and nonionic surfactant has strong synergistic wetting effect.The combination of nonionic surfactants has weak synergistic wetting effect.A wetting agent（wetting agent C）was prepared according to the synergistic wetting properties of the surfactant,and its concentration was optimized based on the surface tension and contact angle.At the same concentration,the surface tension of wetting agent C was lower than that of its monomers,and the CMC was decreased by 0.4wt%,1.9wt%and 0.1wt%,respectively.The wettability of wetting agent C was significantly improved.The monomer surfactants of wetting agent C have synergistic effects on reducing the surface tension of solution,reducing the CMC of compound solution system and reducing the hydrophobicity of coal surface.The effects of inorganic salts on the wetting properties of surfactants and the wetting properties of their compounds were studied.When mixed with anionic surfactants,Na Cl,Na₂SO₄ and Mg Cl₂ all showed wettability synergistic effect,while Al Cl₃ only showed wettability reduction effect.When mixed with nonionic surfactants,inorganic salts had wetting synergistic effect on JFC（primary alcobol ethoxylate）,but showed weak wetting reducing effect on PEG800（ethylene glycol polyoxyethylene ether）.According to the synergistic effect of inorganic salts,Mg Cl₂-SDDS（sodium dodecyl sulfonate）and Na Cl-JFC were optimized.The synergistic effect of wetting of inorganic salts was firstly increased and then stabilized with the increase of inorganic salts concentration,and gradually decreased with the increase of surfactant concentration.The surface tension of 0.05wt%Mg Cl₂ in 0.05wt%SDDS solution decreased by 21.53%,which was denoted as wetting agent D.The surface tension of 0.4wt%Na Cl in 0.05wt%JFC solution decreased by 33.78%,which was denoted as wetting agent E.The results of XPS C1s spectrum peak fitting show that the compound wetting agent reduces the hydrophobicity of coal dust surface.According to the experimental results and related theories,the wetting mechanism of inorganic salts for anionic surfactants and nonionic surfactants was explained by ionic atmosphere compression and“salting-out”,respectively.The application performance of the compound wetting agent was analyzed from three aspects:atomization dust removal rate,water retention and additive cost.The results show that under the same atomizing condition,the dust removal rates of wetting agent C,wetting agent D and wetting agent E are increased by 14.65%,14.92%and 13.73%,respectively,compared with water,and the dust removal performance is significantly improved.The three wetting agents have certain water-retaining effect on lignite,bituminous coal and anthracite.The economic efficiency of the wetting agent was analyzed by the cost of adding water per ton.The economic efficiency of the wetting agent was from high to low as the wetting agent D>Wetting agent C>Wetting agent E.