Research Of Water Injection Dust Inhibitor For Coalescent Protolith In Open Pit Mine In Fire Area

The productive dust pollution in open-pit coal mines is generally serious,which seriously endangers the health of production personnel,accelerates the wear and tear of mining machinery,and poses potential hazards to mine safety and production efficiency.Most of the Dananhu open pit coal mines in Xinjiang,China are located in the distribution area of igneous rocks.The rocks in the vertical direction show a layered occurrence structure,and the physical and chemical properties of each layer are quite different.Water injection pre wetting with dust inhibitor is an effective method to control dust in the working face of open-pit coal mine.The lithology difference between different rock strata brings practical difficulties to the selection of dust inhibitor.Based on the method of pre wetting and dust reduction by water injection in the original rock,and taking the improvement of the physical and chemical properties of the original rock as the starting point,this paper studies the applicable water injection dust inhibitor for the stratified original rock of the open-pit mine in the burning area.The physical and chemical properties such as chemical group,micro morphology and contact angle of layered protolith samples are measured respectively,and the main factors affecting the wettability of rock samples are analyzed;Fifteen kinds of surfactants were selected,and four kinds of monomer surfactants were selected as single components of water injection dust suppression agent with contact angle,surface tension and penetration time as test indexes;The orthogonal test method is adopted for compounding.Taking the contact angle of water injection dust inhibitor on the surface of rock sample,the surface tension of water injection dust inhibitor and the penetration time in rock sample as test indexes,the best formula of water injection dust inhibitor is finally determined;The software FLUENT is used to carry out the numerical simulation of borehole dust inhibitor water injection pre wetting on the stratified original rock,and finally determine the best process parameters of dust inhibitor water injection such as flow rate and pressure.The measurement results of monomer surfactant properties show that surfactant can effectively improve the wettability of rock dust.Due to the amphiphilic nature of surfactant,it can reduce the contact surface between solution and air,reduce the surface tension of solution and improve the wettability of rock dust.According to the significant color difference of stratified protoliths in the working face of No.2 coal mine in Dananhu,Xinjiang,the six layered protoliths are studied.The FTIR test results show that the four protolith samples have obvious characteristic peaks at 1520cm^-1 and792cm^-1 respectively,indicating that they all contain hydrophobic substances such as aromatic rings and aromatic hydrocarbons,which proves the necessity of adding wettable dust inhibitor for protolith water injection.SEM microscopic observation shows that the particle size on the surface of rock dust is uneven,the shape is irregular and the surface morphology is rough,resulting in poor wettability of rock dust and difficult water injection diffusion.The results of single component screening experiment of water injection dust inhibitor showed that the critical micelle concentration（CMC）of 15 surfactants was concentrated in 0.05%-0.15%;The wetting speed of the same surfactant on different rock samples has the same trend,but the wetting ability is not the same;Anionic fast infiltration T,non-ionic OP emulsifier,amphoteric lad-40 and LAB-35 are preferred as composite components;At the same time,it is found that surfactant can effectively improve the wettability of rock dust.The main reason is that it has amphiphilic,which can reduce the contact surface between solution and air,reduce the surface tension of solution and improve the wettability of rock dust.Taking the contact angle,surface tension and penetration time as the indexes,the optimal formula of water injection dust inhibitor is determined as 0.15%OP emulsifier,0.10%rapid penetration T,0.15%LAD-40 and 0.10%LAB-35.In the water injection simulation experiment of stratified original rock,the effects of using water injection dust inhibitor and water,changing water injection speed and water injection pressure are simulated respectively.The results show that the performance of water injection dust inhibitor is better than that of water.With the increase of water injection speed and pressure,the water injection time required for the rated permeability range can be effectively shortened;The numerical simulation finally determines that the optimal water injection speed is6m/s and the optimal water injection pressure is 4MPa.