Analysis Of Coal Mine Underground Corrosion Environment And Research Of Pipeline Metal

The development degree of coal mining industry directly reflects a country’s science and technology,economy and status.However,with the excavation and development of coal mine Wells,it is found that when the pipeline is used in the coal mine environment,the pH value and ions in the coal mine environment cause serious corrosion damage,which greatly limits the development of coal mining industry.Due to the formation of pipeline corrosion is very complex,many influencing factors,and the feasibility,economy,reliability,in corrosion prevention measures is difficult to once and for all,need to combine the specific situation,multi-angle analysis,so as to choose the right pipe material,adjust measures to local conditions to take measures,therefore,the pipeline in the harsh coal mine environment of corrosion damage mechanism and provide the corresponding material principle,is to promote the key of the coal mining industry to the direction of high efficiency,safety,environmental protection and energy saving.This thesis investigates the physical and chemical properties and corrosion forms of corrosion media in different blocks:collect the mine water,coal dust and coal quality and other media from 25 different blocks,analyze the physical and chemical properties of mine water in different blocks,evaluate the morphology and composition of coal dust and coal quality,evaluate the corrosion properties,divide the corrosion grades of different mine environment,and study the selection of pipeline metal materials according to the corrosion properties and economy of different coal mines.For 16 mine corrosion environment and mining conditions,the material corrosion behavior and law,using electrochemical dynamics method of carbon steel and stainless steel pipe,hydraulic support（mainly for piston rod,live column surface coating）and other metal materials in different blocks of mine water,coal dust,coal medium and corrosion rate parameters,corrosion morphology,corrosion product characteristics,the carbon steel and stainless steel pipe,hydraulic support piston rod,live column surface coating material evaluation.In underground coal mine,the corrosion degree of carbon steel and low alloy steel depends on the mine water ion content,pH value and sulfur content of coal slime/coal,through the field of the mine water and coal/coal slime physical and chemical properties of detection can be seen that the mine water are different degrees of alkaline,pH value between 7 and 9,coal mine medium pH value is10.71,strong alkaline,however,the pH value is greater than 10,on the steel surface will form hydroxide barrier layer,separate steel surface and solution,corrosion rate decreased obviously,so the corrosion of coal in mine is weak.In Daliuta mine,the medium has the highest salt content,reaching 2517.87mg/L,and the presence of salt will increase the conductivity of mine water,thus accelerating corrosion.In addition,the corrosive anions Cl^-,HCO₃^-,SO₄^2-and CO₃^2-were detected in all the mineral medium,Cl^-and SO₄^2-as strongly invasive ions more strongly affect the corrosive properties of the solution,Cl^-with its small radius,strong penetrating ability,More easier to adsorb on the passivation film,Combined with the cations on the blunt membrane to form a soluble chloride,Formation of small corrosion pits on the surface of the exposed matrix,And cause corrosion to the matrix,While the amount of sulfate was increased,The pH value of the mine water drops,The corresponding H⁺equilibrium potential moves positively,Increasing the trend of corrosion thermodynamics,Increasing the corrosion,Among them,the highest Cl^-content in the Jiao Mei was 49.04 mg/L,The highest content of SO₄^2-in the Luliang was 4800.00 mg/L,Therefore,it can be seen that the Jiao Mei water samples and Luliang water samples are also highly corrosive.It can be seen from the physical and chemical properties of the mine coal/coal slime that the dust diameter in the total return air roadway of the mine is between 20μm and 50μm,and the slime diameter in the return air roadway of the coal mining face is small,most of which is from 10μm to 30μm.Pulverized coal/coal slime is mainly composed of a large number of C element O elements,which has the highest sulfur content in the medium coal mine,and it is the most corrosive.The results show that carbon steel plus high molecular coating can be applied to most mine environments,but the later maintenance cost should be considered according to the coating performance,and the coating system with excellent performance should be selected according to the field environment.For stainless steel in some strongly corrosive coal mine environment,409L is selected as pipe material,more Cr elements in 409L,which is easy to generate passivation film in the matrix,and in the alkaline environment,430 materials Cr and Mo have high content.Mo can significantly increase the aggregation of Cr in the passivation layer,and make the passivation film is stable;in the strong alkaline environment,Cr elements in 439,439 have more Cr elements to form passivation film,a small amount of Ni elements are added to improve the passivation performance,and the passivation film is more stable.