埋地金属管道的管外阴极保护数值模拟研究
发布时间：2018-08-21 11:59
【摘要】：埋地金属管道被广泛应用于石油、化工、天然气工业的油气储运,同时也大量使用在生活以及消防用水的输送当中。由于土壤对埋地金属的腐蚀作用,通常采用阴极保护技术来对埋地管道进行腐蚀防护,避免因腐蚀而发生泄漏,从而延长管道的使用寿命。埋地管道的阴极保护电位分布是影响其保护效果的重要因素,搞清楚其电位分布的规律对于提高阴极保护的效果有着重要的意义。首先通过对金属在土壤中的电化学腐蚀原理及其腐蚀类型进行综述,整理得到了埋地管道腐蚀防护的措施,进而引出电化学保护方法中的阴极保护技术,综述了该技术的内容以及研究现状,指出传统方法的不足,提出采用了数值模拟的方法来对埋地金属管道的管外阴极保护电位分布进行研究。然后通过理论推导,以拉普拉斯方程为基础,结合电化学极化的特征得到了阴极保护电位分布的数学模型。通过20#钢在土壤中的电化学实验得到了其在不同含水率的土壤中的极化特性,它同时也作为了数学模型的边界条件。通过有限元方法求解了一个阴极保护系统的电位分布,逻辑分析了其模拟结果,验证了方法的可行性。并以此方法分别研究了采取分布式阳极地床、柔性阳极地床以及深井阳极地床时的电位分布规律,发现分布阳极需要以阳极数量和位置的调整来使电位分布均匀,靠近阳极的管道电位较低;柔性阳极电位分布最均匀;深井阳极形成的电位呈漏斗型。还通过数值方法对三种地床形式下的土壤电阻率,阳极数量以及位置的电位影响因素进行了研究,发现分布式阳极地床在土壤电阻变大时电位变的均匀,增加阳极数量可达到同样的效果;柔性阳极对影响因素的变化很敏感,阴极保护系统稳定性差;深井阳极处于电阻率小的土层时能获得更好的电位分布,中间土层对电位分布影响较小,阳极数量对电位分布较大。将数值模拟方法应用于阴极保护的设计当中,针对一输水埋地管道的阴极保护分别采用传统方法和数值方法进行计算。分析了各自的特点,得到了数值模拟离不开传统方法的结论,它们是相辅相成,互相紧密联系的。通过将两种方法的结合,对提高阴极保护的质量,降低设计失误的机率有着重要的价值和意义。
[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.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE988.2
本文编号：2195648
[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.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE988.2
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