Research On The Spatiotemporal Evolution Law Of Diffusion Distribution And Control Technology Of H₂S Gushing From Mining And Excavating Face

With the increase of the depth and scope of coal mining,many high-sulfur coal seams are gradually involved,and under geological conditions such as rock nodules and rock walls,the phenomenon of abnormal enrichment and gushing of H₂S gas is often accompanied.Hydrogen sulfide（H₂S）is a colorless,highly toxic acid active gas.As a strong neurotoxin,it will seriously affect the occupational health and orderly mining operations of working personnel.At present,in order to solve the problem of high-concentration H₂S gushing in the project,the pretreatment method of alkali injection inside the coal body and the control measures of spraying alkali mist in the roadway are usually used.The geological conditions of coal seams are usually treated by spraying alkali mist or alkaline foam covering the roadway.The roadway working face is the main place for workers to move.It is very important to clarify the diffusion and distribution rules of H₂S in the roadway during the mining process and the prevention and control measures.In this paper,numerical simulation,theoretical analysis research methods,and computational fluid dynamics（CFD）theory are used to solve the flow fields of mathematical models such as N-S equations,convection-diffusion equations,and the multi-field coupling of chemical transfer fields through COMSOL simulation numerical solver.The characteristics of the flow field at the working face and the spatiotemporal evolution and diffusion distribution of the gushing H₂S gas were studied in a dimension;the technical measures for the gas-liquid two-phase vortex alkali mist to control the gushing H₂S in the roadway were proposed,and the nozzles were studied by the methods of experimental research and theoretical analysis.The vortex characteristics,fluid atomization morphology and characteristics lay the foundation for further engineering applications.The conclusions are as follows:（1）The diffusion law of H₂S gushing from fully mechanized face shows three dynamic stages:desorption gushing,equivalent convection,and diffuse diffusion.The distribution law shows three areas of inertial convection high concentration area,transition diffusion low concentration area,and return wind vortex turbulence area.Characteristic area;the diffusion law of H₂S gushing from the fully mechanized excavation face presents three stages of convective dilution,eddy current dispersion,and diffusion and settlement,and the distribution law presents four characteristic areas of dilution domain,retention group,diffusion zone,and settlement area.（2）The distribution and variation characteristics of H₂S concentration in the return airway of the fully mechanized mining face:the wind flow vortex area will appear within 5～10 m of the return airway,and the H₂S gas backflow vortex will appear under the action of this flow field;In the direction of gas outflow in the roadway,the H₂S concentration gradually increases and then decreases slightly;the H₂S concentration in the inner side is higher than that in the outer side,and gradually transitions.The H₂S concentration in the upper and lower sides is high,and the concentration in the middle is low.At the same time,the concentration of the bottom plate is higher than that of the top plate;The H₂S concentration at the sampling point in the middle of the return air alley continued to increase with time,and the increase first increased and then decreased.（3）Distribution and variation characteristics of H₂S concentration in fully mechanized mining face:along the downwind of the shearer and in the two directions where the shearer transitions to the pedestrian side,the H₂S concentration distribution shows a gradually decreasing trend;H₂S gushing out The concentration spreads linearly with time.The diffusion speed of H₂S molecules is about 1.26 to 1.46 times that of the wind flow at the position 1.6 m away from the bottom of the floor.is large,the relationship between the maximum diffusion concentration C of H₂S on the pedestrian side and x satisfies the following formula:C=4.92e（x-5）/8.833-4.92Focus on the polluted area 20 meters away from the rear of the fuselage.For mines where H₂S gas is abnormally gushing out,several detection devices can be installed on the pedestrian side of the area.（4）Characteristics of wind flow field in fully mechanized excavation face:when the air duct outlet is far away from the coal wall of the working face,it presents a vortex area,a recirculation area,and a steady state area.Different characteristics of the vortex area;there is a"negative pressure area"between the air duct and the driving face,and this area gradually moves forward as the air duct air outlet approaches the coal wall of the driving face,and the positive and negative pressure difference will produce eddy currents,so the vortex will gradually approach the coal wall.（5）Distribution and variation characteristics of H₂S concentration on the fully mechanized excavation face:the H₂S concentration at the driver’s position on the side of the air duct shows a linear increasing trend with time;the H₂S concentration along the return air side shows a decreasing trend;The tuyere is 3 m away from the coal wall,which can promote the dilution of H₂S gas;according to the distribution characteristics,it is reasonable to install the H₂S concentration detection sensor on the coal wall opposite to the air duct.（6）Studies have shown that the atomizing vortex nozzle can generate a vortex dry mist characteristic fluid with an average diameter of 10～100μm of Sotel,and can produce a fluid of about 55°under the working conditions of water pressure of 0.24 MPa and air pressure of0.45 MPa.In the atomization range,the water consumption of a single nozzle is less than 1L/min,which can be used as an effective means for the prevention and control of H₂S in the working face;the particle size distribution of the droplets is as follows:with the continuous increase of the distance along the spray direction of the nozzle,the average diameter of Sotel gradually increases;Along the vertical direction from the bottom to the top,the droplet particle size first decreases and then increases,and the particle size of the corresponding point at the same distance in the positive and negative directions is asymmetrically distributed;The other characterizations of the particle size decrease depending on the elevated air pressure to varying degrees,and increase depending on the elevated water pressure to varying degrees.