【摘要】：埋地金屬管道被廣泛應(yīng)用于石油、化工、天然氣工業(yè)的油氣儲運,同時也大量使用在生活以及消防用水的輸送當(dāng)中。由于土壤對埋地金屬的腐蝕作用,通常采用陰極保護(hù)技術(shù)來對埋地管道進(jìn)行腐蝕防護(hù),避免因腐蝕而發(fā)生泄漏,從而延長管道的使用壽命。埋地管道的陰極保護(hù)電位分布是影響其保護(hù)效果的重要因素,搞清楚其電位分布的規(guī)律對于提高陰極保護(hù)的效果有著重要的意義。首先通過對金屬在土壤中的電化學(xué)腐蝕原理及其腐蝕類型進(jìn)行綜述,整理得到了埋地管道腐蝕防護(hù)的措施,進(jìn)而引出電化學(xué)保護(hù)方法中的陰極保護(hù)技術(shù),綜述了該技術(shù)的內(nèi)容以及研究現(xiàn)狀,指出傳統(tǒng)方法的不足,提出采用了數(shù)值模擬的方法來對埋地金屬管道的管外陰極保護(hù)電位分布進(jìn)行研究。然后通過理論推導(dǎo),以拉普拉斯方程為基礎(chǔ),結(jié)合電化學(xué)極化的特征得到了陰極保護(hù)電位分布的數(shù)學(xué)模型。通過20#鋼在土壤中的電化學(xué)實驗得到了其在不同含水率的土壤中的極化特性,它同時也作為了數(shù)學(xué)模型的邊界條件。通過有限元方法求解了一個陰極保護(hù)系統(tǒng)的電位分布,邏輯分析了其模擬結(jié)果,驗證了方法的可行性。并以此方法分別研究了采取分布式陽極地床、柔性陽極地床以及深井陽極地床時的電位分布規(guī)律,發(fā)現(xiàn)分布陽極需要以陽極數(shù)量和位置的調(diào)整來使電位分布均勻,靠近陽極的管道電位較低;柔性陽極電位分布最均勻;深井陽極形成的電位呈漏斗型。還通過數(shù)值方法對三種地床形式下的土壤電阻率,陽極數(shù)量以及位置的電位影響因素進(jìn)行了研究,發(fā)現(xiàn)分布式陽極地床在土壤電阻變大時電位變的均勻,增加陽極數(shù)量可達(dá)到同樣的效果;柔性陽極對影響因素的變化很敏感,陰極保護(hù)系統(tǒng)穩(wěn)定性差;深井陽極處于電阻率小的土層時能獲得更好的電位分布,中間土層對電位分布影響較小,陽極數(shù)量對電位分布較大。將數(shù)值模擬方法應(yīng)用于陰極保護(hù)的設(shè)計當(dāng)中,針對一輸水埋地管道的陰極保護(hù)分別采用傳統(tǒng)方法和數(shù)值方法進(jìn)行計算。分析了各自的特點,得到了數(shù)值模擬離不開傳統(tǒng)方法的結(jié)論,它們是相輔相成,互相緊密聯(lián)系的。通過將兩種方法的結(jié)合,對提高陰極保護(hù)的質(zhì)量,降低設(shè)計失誤的機(jī)率有著重要的價值和意義。
[Abstract]:Buried metal pipelines are widely used in oil and gas storage and transportation in petroleum, chemical and natural gas industries, as well as in the transportation of domestic and fire water. Because of the corrosion effect of soil to buried metal, cathodic protection technology is usually used to protect buried pipeline from leakage due to corrosion, thus prolonging the service life of pipeline. The distribution of cathodic protection potential of buried pipeline is an important factor affecting its protective effect. It is of great significance to find out the law of potential distribution in order to improve the effect of cathodic protection. Firstly, the principles and types of electrochemical corrosion of metals in soil were summarized, and the corrosion protection measures of buried pipeline were obtained, and then the cathodic protection technology of electrochemical protection method was introduced. This paper summarizes the content and research status of this technology, points out the shortcomings of traditional methods, and puts forward a numerical simulation method to study the potential distribution of cathodic protection outside the tube of buried metal pipeline. Then the mathematical model of cathodic protection potential distribution is obtained based on Laplace equation and the characteristics of electrochemical polarization. The polarization characteristics of 20 # steel in soil with different moisture content were obtained by electrochemical experiments in soil. It also served as the boundary condition of the mathematical model. The potential distribution of a cathodic protection system is solved by finite element method. The simulation results are analyzed logically and the feasibility of the method is verified. The potential distribution of distributed anode bed, flexible anode bed and deep well anode ground bed is studied by this method. It is found that the distribution anode needs to adjust the number and position of anode to make the potential distribution uniform. The potential of the pipeline near the anode is lower, the distribution of the flexible anode is the most uniform, and the potential of the anode in the deep well is funnel-shaped. The influence factors of soil resistivity, the number of anodes and the potential of position were also studied by numerical method. It was found that the potential of the distributed anodic bed changed uniformly when the soil resistance increased. The same effect can be achieved by increasing the number of anodes, the flexible anode is sensitive to the change of influencing factors, the stability of cathodic protection system is poor, and the potential distribution of deep well anode is better when it is in the soil layer with low resistivity. The intermediate soil layer has little effect on the potential distribution, and the number of anode has a great effect on the potential distribution. The numerical simulation method is applied to the design of cathodic protection. The traditional method and numerical method are used to calculate the cathodic protection of a buried pipeline. The characteristics of each method are analyzed and the conclusion that the numerical simulation can not be separated from the traditional methods is concluded that they complement each other and are closely related to each other. By combining the two methods, it is of great value and significance to improve the quality of cathodic protection and reduce the probability of design error.
【學(xué)位授予單位】：西安石油大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TE988.2

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