起伏管线内积液/固体颗粒流动及其冲刷腐蚀的实验研究

The internal corrosion of natural gas pipelines can cause serious accidents, including the leakage and explosion, which affects the safe operation of the pipeline system. The overall aim of the project is to understand the erosion-corrosion phenomena induced by the liquids and solid particles in the up-down wet natural gas pipelines, culminating in the characteristics and mechanism of the erosion corrosion in the gas-liquid-solid multi-dimensional coupling flows. This aim will be achieved via the following three specific objectives: a) To experimentally investigate the wet natural gas-liquids two phase flows and gas-liquids-solid particles multiphase flows in the up-down gas pipelines, respectively. The distribution state and migration law of the liquids and solid particles in these two conditions will be discussed to obtain the effect of the liquid and solid particle on the erosion corrosion phenomenon. b) To study the effects of the characteristic parameters on the erosion corrosion phenomena, including the pipeline state, fluid mechanics, and particle properties by means of the laboratory experiments. The corresponding relation between the characteristic parameters and erosion corrosion rate will be established for wet natural gas pipelines. c) To study the corrosion morphology of the internal surface of the pipelines induced by the liquids and solid particles, by employing the electrochemistry measuring method and surface analysis tools. The correlative mechanism of the erosion process on the corrosion pit morphology and the corrosion product distribution will be revealed in the various parameters. The research achievements will establish a theoretical and experimental foundation for the erosion corrosion mechanism induced by the liquids and solid particles in the up-down wet natural gas pipelines. The research is also very significant to the safe operation of the wet natural gas pipeline system.

天然气管线的内腐蚀会造成管线泄漏、爆炸等严重事故，影响管线安全运行。针对起伏湿气管线中积液/固体颗粒流动产生的冲刷腐蚀问题，本项目拟开展起伏管线中湿气-积液-固体颗粒多相流流动及其冲刷腐蚀的实验研究。内容包括：实验研究起伏管线中湿气-积液两相流、湿气-积液-固体颗粒多相流流动规律，获得两种流动条件下积液、固体颗粒的分布状态与运移规律，探明积液、固体颗粒对流动冲刷腐蚀的作用机制；研究管线起伏状态、流体力学参数、颗粒性质等对多相流流动及冲刷腐蚀特性的影响规律，建立多起伏湿气管线内多因素复杂耦合下的冲刷腐蚀作用区域模型；利用电化学测量和表面形态分析方法，分析遭受冲刷腐蚀管线内壁面的微观形貌特征，探明蚀坑形貌及产物分布与冲刷条件的关联机制，揭示多起伏湿气管线内积液/固体颗粒的冲刷腐蚀机理。研究成果为有效控制湿气管线内的冲刷腐蚀危害，保障管线的安全运行奠定理论基础。

环境污染及气候变化对能源的清洁利用提出了更高的要求，天然气作为一种相对清洁的能源，其在能源消费结构中的作用越来越重要。然而，天然气管道的腐蚀引起的管线破裂不仅会中断天然气的输送，造成巨大的经济损失，还会对人员安全和自然环境造成严重危害。本项目通过自主设计并搭建了适用于积液和固体颗粒流动及其冲刷腐蚀的实验装置，采用失重法、电化学分析及表面形貌测试等方法研究了积液及颗粒对管线钢的冲刷腐蚀行为，获得了积液/固体颗粒流动对管线刚的冲刷腐蚀机理。结果表明：当积液量相同时，随着管径及起伏角的增大，积液液面临界起塞速度越大，随着积液量h/D的增加，积液液面起塞的临界表观气速逐渐减小，对积液液面起塞临界气速起决定作用的是管道底部积液液位高度与管径之比h/D；管道入口表观气速越大，管道底部积液量越多，管道内形成液塞时，管内压降也越大，管道起伏角越大，液塞形成时，管道内的压降反而越小，对于管道压降起决定作用的是管道底部积液液位高度与管径之比h/D与入口表观气体流速；随pH值升高，管线钢冲刷腐蚀逐渐减弱，冲刷腐蚀由电化学活化控制转变为氧去极化控制，试样表面腐蚀坑数量减小，深度变浅；随温度升高，管线钢冲刷腐蚀逐渐增强，反应电阻减小，试样表面腐蚀坑数量减小深度变深；砂粒粒径的增大对冲刷腐蚀失重率及冲刷腐蚀的交互作用具有促进作用，且交互作用以腐蚀促进冲刷为主，提高流速对管线钢冲刷腐蚀总失重速率有促进作用，流速为0.5 - 1 m/s，粒径为37.5 - 50 μm时，腐蚀对冲刷起抑制作用；随咪唑啉缓蚀剂用量的增加，缓蚀效果呈先增强后减弱的趋势，当咪唑啉缓蚀剂用量为80 mg/L时，缓蚀效果达到最佳为39.47%；石墨烯光固化环氧丙烯酸树脂（G/EA）涂层对管线钢具有良好保护作用，并且随石墨烯浓度的增加，G/EA涂层的保护效果先增强后减弱，石墨烯浓度为0.3 %时，保护效果最佳为90.34%。本项目的研究成果为管线的安全运行及管理提供技术指导和理论支撑，对实现油气行业的节能减排具有重要的实际意义。