CO_2输送管道腐蚀研究进展

Research Progress of Corrosion on CO_2 Pipeline Transportation

在碳捕获、利用与封存(CCUS)的研究中,CO_2管输中的腐蚀控制尤为重要。在CO_2管道腐蚀研究成果的基础上,归纳了CO_2输送管道的腐蚀速率、机理、过程及主要控制措施。研究显示H2O是产生腐蚀的主要因素,输送过程中水含量的均值不应超过0.038%(体积分数)。当存在SO2及O2时,管道的腐蚀速率将达到4.0 mm/a;当存在NO2时,管道的腐蚀速率将达到12 mm/a。O2含量较低时加速腐蚀,当O2含量大于0.057%(体积分数)时出现钝化现象,且腐蚀速率小于0.01 mm/a。CO_2腐蚀产物中的表层是Fe CO3等轴晶粒,中间为棒状晶粒且充满孔洞,最内层为致密的Fe CO3晶粒。形成过程为:钢材基体在最初溶解阶段形成Fe3C架构,Fe CO3晶粒沉积在表面,然后CO_22-和HCO3-向内扩散并与钢基体反应形成中间层和内层。工程中采用抗腐蚀管材、涂镀层管材、加注缓蚀剂以及阴极保护等措施克服腐蚀影响。

Corrosion control for CO2 pipeline is especially important in the study of carbon capture, utilization and storage （CCUS） project. Based on the research results, corrosion rate, mechanism, and process of CO2 pipeline were summarized in this paper. The results showed that H2O was the key factor for corrosion, and the content in pipeline transport was under 0.038% （volume fraction）. The corrosion rate was 4.0 mm/a when mixed with SO2 and O2, and even 12 mm/a when mixed with NO2. Corrosion was accelerated when O2 concentration was low. When it was higher than 0.057% （volume fraction）, passivation phenomenon appeared and the corrosion rate was below 0.01 mm/a. In CO2 corrosion products, there were three layers： equiaxed crystal FeCO3 in surface layer, clubbed crystal in middle layer and dense crystal particle FeCO3 in innermost layer. During the process of CO2 corrosion, steel pipeline dissolved to form Fe3C framework, and FeCO3 crystal particle deposited on its surface. Then, CO2^2- and HCO3^- diffused inward to form the middle and innermost layer. In engineering design, corro- sion-resistant tube, protective layer tube, corrosion inhibitor, and cathodic protection are used to solve corrosion problem.