| Dust is one of the major disasters faced by coal mining,which seriously threatens the physical and mental health of workers and the safe production of enterprises.As the most widely used dust control method in coal mines,water spray has the poor dust-reducing effect,especially for dust particles with small diameter size and strong hydrophobicity,of which dust control efficiency is difficult to meet the requirements of mine dust control.In order to improve the wet performance of the aqueous solution and prevent the dust in the coal mine,especially the respirable dus,based on the synergistic effect between the surfactant and magnetization on the wetting properties of the aqueous solution,this paper proposes a novel dust control technology using the surfactant-magnetized water.Meanwhile,for dust control mechanism and technology of the surfactant-magnetized water in underground coal mine,the paper adopted the combination method of theoretical analysis,experimental research and numerical simulation to systematically investigate on the synergistic effect between the surfactant and magnetization used to improve the solution wettability,the effective magnetization theory of surfactant-magnetized water,and the high-efficiency atomization and dust reduction methods in coal mines,etc.The following research results were shown as follow:From the molecular structure level,the synergistic mechanism between the surfactant and magnetization used to improve the solution wettability was revealed by the combination methods of kinetic simulation and experiment.Studies have shown that the magnetization can change the radial distribution function of water molecules and enhance the diffusion coefficient of water molecules,destroy the hydrogen bond structure between water molecules,while breaking the macromolecular clusters into more small molecular groups,which reduces the solution cohesion,and thus improves the aqueous solution wettability.In addition,the active additive(containing the anionic nonionic surfactant)greatly improves the wetting property of the aqueous solution by the active groups,and the isolation layer formed by the anionic nonionic surfactants on the surface of the aqueous solution is more compact under the effect of the magnetization.It reduces the critical micelle concentration of the active additive and also increases the solution wettability.The surfactant-magnetized water utilizes the organically combination between the active additive(chemical method)and magnetization(physical method)to greatly enhance the coagulation ability between dust particles and droplets.Based on the synergistic mechanism between the magnetization and surfactant in improving the wetting property of the solution,combined with the mechanism of synergistic effect between the anionic and nonionic surfactants,a highly effective active agent for preparing the surfactant-magnetized water was developed.Based on surface tension,contact angle and dust settling time,meanwhile,the solution spreading work,immersion work,foaming and wetting performance growth rate were also used as the auxiliary performance parameters,a novel evaluation system of the solution wetting performance was established.The system analyzed the effects of different monomers and compounding surfactants on the solution wetting properties,and the effects of magnetization on the performance of the compounding agent solution was studied.The results indicated that the wettability of the anionic surfactant solution is more easily improved than the nonionic surfactant under the effect of magnetization;under the same compounding conditions,the active additive(F+C)has the strongest wettability and the best synergistic effect with magnetization.Based on this,a low-cost surfactant-magnetized water additive which can well synergize with the magnetic field was developed.That is,when the nonionic surfactant F content is 15%,it is compounded with the anionic surfactant C,and the surfactant content controling coal dust in underground coal mines is only 0.03%.Using the small magnetization experimental system of active additive solution,the effects of magnetization mode,magnetic field strength,magnetic path and water flow velocity through a magnetic field on the wettability of the surfactant-magnetized water were investigated.The magnetization parameters used to generate the surfactant–magnetized water are confirmed,and an efficient magnetization method based on the coupling magnetization of pulsation cutting and spiral turbulence is proposed.The results show that the surfactant-magnetized water produced by the solution containing0.03%active additive passing through the coupling magnetization of pulsation cutting and spiral turbulence(magnetic path of 8 m)with a magnetic field strength of 300-350mT at a speed of 4 m/s,and its wettability is good,of which contact angle is reduced by 29.93%compared with the original active additive solution,reduced to 23.97°;at the same time,its surface tension has been further reduced,reaching 26.37 mN/m.On this basis,the internal structure of the magnetized device and the distribution method of the internal and external magnets required for the efficient preparation of the surfactant-magnetized water were studied and established,and the magnetized device used to generate the surfactant-magnetized water was successfully developed.The atomization and dust control characteristics of the surfactant-magnetized water under different experimental conditions were systematically investigated by the self-constructed experimental system.On this basis,the spray atomization technology system of the surfactant-magnetized water suitable for coal mine dust control was constructed.The results show that the atomization effect of the dust spray field formed by the nozzle with a diameter of 1.5 mm at the spray pressure of 5 MPa tends to be maximized;the relationship between the spray pressure and the dust control efficien of the surfactant-magnetized water is in accordance with the exponential function,while the fitting equation is:η=-151.51*exp(-P/1.24)+80.07.At the same time,the surfactant-magnetized water has the high dust-reducing efficiency for different particle size ranges.Compared with that of untreated water,the dust control efficiency of the surfactant-magnetized water was improved by 31.46%for coal dust with the particle size range of 0~2.5μm.In addition,based on the research on the relationship between different nozzle arrangement methods and atomization characteristics of the surfactant-magnetized water,a novel nozzle arrangement device was developed,significantly improving the coverage area of the fog field.Field application verified that the dust control technology using the surfactant--magnetized water can effectively suppress the suspended dust particles in underground coal mines,especially the respirable dust.The field application of 3109heading face in Zouzhuang Coal Mine showed that the dust reduction technology using the surfactant-magnetized water can effectively reduce the dust concentration in underground coal mines.The dust concentration of total dust and respirable dust is reduced to 11.94 mg/m~3 and 7.74 mg/m~3,respectively.At the same time,The application of coal mining face in the Luywa Coal Mine of Shandong Lutai Holding Group further showed that dust reduction technology using the surfactant-magnetized water can effectively capture the dust in the coal mining face,and the dust control efficiency of the total dust and respirable dust reached 89.1%and 87.6%,respectively,improved by 34%,46.29%respectively,compared with the water spray.In addition,the field application further verified the synergistic effect between the magnetization and surfactant solution.The paper contains 117 pictures,19 tables,and 217 references. |
