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某石化公司裂解装置稀释蒸汽发生器E-3011/C 泄漏停工，检修检查时发现，稀释蒸汽发生器 据现场腐蚀调查及工艺了解，对稀释蒸汽发生器腐蚀机理进行探讨，并提出防护建议。 1 腐蚀形貌
医用手腕带
E-3011/C 管束腐蚀断裂泄漏部位及腐蚀形貌见图1。
图1 E-3011/C 管束腐蚀泄漏部位及腐蚀形貌
弹簧制作
从图1可以看出，泄漏部位主要集中在换热器中下部，也是汽液两相的交汇处；腐蚀未穿孔部位蚀坑呈凿沟状，蚀坑深约1～2 mm ；腐蚀环境温度170 ℃；凿沟状腐蚀形貌符合API 571所描述的碱腐蚀形貌（１）。腐蚀失效部位局部减薄严重。换热器管束内壁及管板外观情况见图2。
从图2可以看出，换热器管束内壁及管板焊缝光洁，无明显腐蚀迹象。因此，腐蚀主要是由
壳程工艺水介质引起的。
2 腐蚀机理2.1 工艺流程
E-3011是利用265 ℃（最高305 ℃）左右的中压蒸汽，将170 ℃左右的工艺水由液相加热到
汽相，给裂解炉系统提供稀释蒸汽。具体工艺原则流程如图
3所示。
从图3可以看出，工艺水来自工艺水汽提塔C-3001塔底，由P-3071加压后，先进入稀释蒸
图2 E-3011/C 管束内壁及管板处腐蚀形貌
收稿日期：
2018-12-13
作者简介：黄新泉，男，1993年毕业于成都理工学院工业分析专业，工学学士，主要从事炼油化工腐蚀防护、监测和研究工作，高级工程师。电话：0992-*******，E-mail: yjy_hxq@petrochina
裂解装置稀释蒸汽发生器泄漏原因分析
黄新泉
（中国石油天然气股份有限公司独山子石化分公司，新疆 独山子 833699）
摘 要：简要介绍了某石化公司裂解装置稀释蒸汽发生器管束腐蚀泄漏的腐蚀形貌、腐蚀机理、防范措施，从工艺流程，工艺参数，腐蚀形貌，腐蚀介质等方面，指出稀释蒸汽发生器腐蚀泄漏主要是由局部碱浓缩腐蚀引起。换热器工作环境尽管为汽液两相，但温度高达170 ℃以上，同时，pH 值为弱碱性，表明不存在湿硫化氢酸腐蚀环境。而腐蚀形貌为局部凿坑状，符合API 571关于碱腐蚀形貌的描述，能谱分析也表明失效部位存在Na 等碱金属离子。从腐蚀环境和腐蚀形貌两个方面表明，换热器失效部位存在碱腐蚀行为。另外，工艺条件要求此部位应液相远大于气相，汽液比应为1：7，以便于液相蒸汽及时带走换热时产生的沉积物。但由于换热器一直处于高负荷运行，汽液比远不能满足要求，导致碱浓缩腐蚀开裂。该分析方法可为类似腐蚀案例的判断提供借鉴。
关键词：裂解装置 稀释蒸汽 发生器 腐蚀机理
汽分离器V-3031，然后由罐底分别进入E-3011和E-3012，加热产生蒸汽后再返回罐顶。作为稀释蒸汽发生器的换热器E-3011/E-3012总计15台，其中以急冷油为热源的E-3012/A~L计12台，以中压蒸汽为
热源的E-3011/A~C计3台。主要的稀释蒸汽在E-3012A-L中，通过急冷油加热产生，剩余部分在稀释蒸汽发生器10-E-3011A-C 中，由中压蒸汽加热产生。
为防止结垢或结焦，工艺水循环泵10-P-3072A/B/S将大量的工艺水加压循环送往蒸发器E-3012/E-3011。为保证换热器内所有管束外壁能被连续冲刷，换热器出口的汽液比一般控制在1︰7，即保证有大量液相工艺水随蒸汽出来，这就要求严格控制好中压蒸汽或急冷油的温度，同时换热器选择U型管束，以实现工艺水的良好分布。
从流程图及上述描述中可以看出，如果稀释蒸汽换热器未能得到有效的连续冲刷，即换热器出口的汽液比过大或过小，因工艺水中有易结垢或易结焦物质，如工艺水注氨中和产生的盐类和工艺水中夹带的少量轻烃类物质，E-3011/E-3012极易结垢或结焦，从而影响换热器的换热效果。在某些特定情况下，这些成垢或结焦物质也可能会导致工艺水中酸或碱物质的浓缩，从而使换热器管束外壁发生酸或碱的浓缩腐蚀。
2.2 腐蚀机理说明
2.2.1 腐蚀介质
稀释蒸汽发生系统的腐蚀主要来自工艺水的少量酸性物质，多以硫化氢的形式存在；为防止工艺水的
酸腐蚀，一般采取在工艺水汽提塔进口处注氨或注碱的措施。但如果长时间注碱过量，在某些特定部位，如换热器管板和管束的胀结焊缝处，因稀释蒸汽换热器温度高达260 ℃左右，很可能导致较严重的碱浓缩腐蚀；2011年前后，在E-3011/B换热器管板与管束胀接处曾经发生过严重的碱浓缩腐蚀，导致管板与管束焊缝多处腐蚀穿孔。
此次E-3011/C腐蚀泄漏，管板表面与管束焊接焊缝完好，未见腐蚀（图2），但管束泄漏部位仍先发生在管板内侧与管束胀接处，管束具体腐蚀部位及形貌见图4
。
图4E-3011/C管束腐蚀部位及腐蚀形貌
从图4可以看出，泄漏管束多位于管板胀接处，下部管束有明显白沉积物，上部管束浮锈明显，但无大面积腐蚀。此次E-3011腐蚀未发生管板焊缝腐蚀穿孔，仅出现管束腐蚀断裂。管板焊缝未腐蚀穿孔表明：2011年后更换的换热器胀接焊缝质量明显提高，E-3011未发生焊缝处的缝隙腐蚀，但碱浓缩腐蚀依然严重，导致管束局部腐蚀断裂。
2.2.2 腐蚀环境
稀释蒸汽系统历来是腐蚀的多发部位，为此，车间建立了冷凝水监测、旁路釜腐蚀挂片监测、在线探针监测、高温测厚、腐蚀检查等多种腐蚀监测手段。但上述监测手段主要是监测工艺水系统的均匀腐蚀，对局部碱浓缩引起的腐蚀无法及时监测，只能从工艺水pH值的变化间接反映碱浓缩腐蚀可能发生的趋势。图5是工艺水塔底出口泵P-3071处工艺水近一年来的pH值变化情况。
从图5可以看出，自2017年10
月以来，工艺图3 稀释蒸汽系统工艺原则流程
水pH值大多控制在9.0以上，最高9.66，且呈上升趋势，工艺水系统盐类结垢趋势增加，碱浓缩可能性增大。工艺水中能带来腐蚀的只有硫化氢类的酸性物质和注碱产生的氢氧化钠和有机胺之类的碱性物质，pH值监测结果表明：不存在硫化氢
腐蚀的酸性环境，但存在碱浓缩腐蚀的碱性环境。图5 10-P-3071工艺水pH值变化趋势
2.2.3 能谱分析
能谱分析结果见表1。
组合式桥架表1
能谱分析结果
表1所示为腐蚀管束外壁腐蚀坑的能谱分析结果，可见主要含有O、Fe、S元素，其次还含有少量的Na、Al、Si等元素。
碱腐蚀机理本质上仍是氧的去极化腐蚀，能谱分析发现Na、O等元素，从微观上证明了碱腐蚀的发生。碱腐蚀反应方程式及过程如下：Fe+4OH-→FeO22-+2H2O+2e
O2+2H2O+4e→4OH-
工艺水中的轻烃类物质，注碱产生的盐类物质及过量的碱随工艺水进入稀释蒸汽发生系统，由于换热器温度控制不当，出口水汽比未达到操作规程要求的1:7，换热器管束外表面温度过高，导致轻烃类物
质在换热器管束外表面结焦，盐类物质在换热器外表面沉积；另外，由于水汽比不足，工艺水未能有效冲刷换热器内的结焦物质和盐类沉积物，换热器内工艺水含量相应减少，致使工艺水中的碱性物质在局部区域浓缩，在高温的环境下，对换热器管束外壁造成严重的碱腐蚀，最终使少量换热器管束腐蚀断裂失效。
另外，E-3011/C之所以要保持高温运行，主要是因为裂解炉加工大量轻烃，所需急冷油负荷减少，E-3012急冷油稀释蒸汽发生器系统无法产生足够的稀释蒸汽，只好靠提高E-3011系统中压蒸汽负荷来生产足量的稀释蒸汽，这是导致E-3011/C结焦、堵塞发生碱浓缩腐蚀的根本原因。
3 结论及建议
1）E-3011/C管束的腐蚀断裂失效是局部碱浓缩后的高温（170 ℃）碱腐蚀。
2）这种腐蚀带有普遍性，即相同部位E-3011/A/B管线也可能发生此类腐蚀，只是暂时还未腐蚀穿孔，应引起管理部门的足够重视。
3）腐蚀产生的原因主要有2个：一是工艺水汽提塔长期注碱或注氨偏高；二是换热器温度，尤其是中压蒸汽温度控制不当，未能控制好换热器出口的水汽比，即无法及时冲走沉积物，也加速了结焦和盐类沉积物的生成，碱在局部浓缩，在高温环境下，导致碱腐蚀发生。
4）建议从严控制工艺水汽提塔的注碱（氨）量及中压蒸汽温度（适当降低中压蒸汽温度），保证换热器出口水汽比，提高换热器内液相工艺水含量，一方面，使换热器管束外壁能得到及时冲洗，另一方面，可减少碱浓缩腐蚀发生的可能性。
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CONSEquENCE ASSESSMENT ON LEAkAGE ACCIDENT OF LIquID CHLORINE CYLINDER AND SAFETY COuNTERMEASuRES [17] Xiang Yanyan.(Yunshan Economic Development Zone Branch of Yongxiu County Security Bureau, Jiujiang, Jiangxi, 330300)
Abstract: Liquid chlorine is very important chemical raw material which plays a pivotal role in national econ-omy. However, liquid chlorine is a dangerous chemical with strong oxidization and corrosivity. Its main risk is poisoning and suffocation. Taking a water supply com-pany as an example, liquid chlorine is mainly used in disinfection process. And now through simulating the poisoning accident caused by the leakage of liquid chlo-rine cylinder; the accident consequences are calculated by the r
isk index method and accident analysis method and safety countermeasures are proposed. Through con-sequence assessment on liquid chlorine leakage acci-dent, technical guidance is provided for safety manage-ment of liquid chlorine cylinder, preparation of special emergency rescue plan and risk assessment.
key words: liquid chlorine cylinder; leakage; acci-dent consequence assessment; countermeasures APPLICATION OF HAZOP AND LOPA ANAL-YSIS TECHNOLOGY TO ATMOSPHERIC AND V ACuuM DISTILLATION uNIT[20]
Zheng Haitao.(SINOPEC Jinan Refining and Chemi-cal Company, Jinan, Shandong, 250101) Abstract: This paper introduces the application of the widely used HAZOP analysis method to risk analysis of atmospheric and decompression unit combining with LOPA analysis technology. The unit is divided into nodes according to the process flow, and each devia-tion is analyzed by HAZOP to identify the risks in the process of device operation systematically and compre-hensively. Taking the analysis results as the input basis and combining with LOPA analysis, the paper proposes preventive measures for risk control, which reduces the risk level and increases the stability of operation control effectively. This paper makes detailed analysis on the low liquid level in the bottom of the primary distilla-tion tower and the low oxygen content in the reduced pressure furnace. Then it puts forward c
迎宾机器人omprehensive protective measures and implementation plan, which is helpful to improve the prevention and control capacity of the atmospheric and vacuum distillation unit and en-sure the safe operation of the unit.
key words: hazard and operability study/HAZOP; lay-er of protection analysis/LOPA; atmospheric and vacu-um distillation unit; risk analysis; preventive measures APPLICATION OF HAZOP IN THE RETRO-FITTING PROJECT OF FEED/DISCHARGE HEAT ExCHANGER FOR REFORMING REAC-TION[27]
Wang Baiya, Li Yang.(Hualu Engineering & Technolo-gy Co., LTD., Xi’an, Shaanxi, 710065)
Abstract:The analysis object of hazard and operabili-ty analysis (HAZOP) in China is mostly complete pro-cess flow. This paper adopts HAZOP analysis method to analyze the process safety and operability of a retro-fitting project of feed/discharge heat exchanger for re-forming reaction in detail. Combining with the actual revamping of the plant, this design change has identi-fied the risk and operability from such aspects as the original production process, equipment manufacturing, construction, and so forth and puts forward opinions and suggestions on the more dangerous analysis items. Since the project does not change the production method and technical route of the o
电锅炉制造
riginal reformer during the revamp, this HAZOP analysis has carried out certain exploration in node division and analysis ideas, which can provide reference for HAZOP analy-sis work of similar technological revamp projects. key words: hazard and operability study/HAZOP; re-forming reaction; heat exchanger modification; deviation CAuSE ANALYSIS ON PRODuCTION SAFETY ACCIDENTS IN CONSTRuCTION ENTER-PRISES AND PREVENTION AND CONTROL COuNTERMEASuRES[33]
Zhou Dehong, Chen Huifang, Li Zuo, Xu Yuan, Wu Meng.(Xingfa School of Mining Engineering, Wuhan Institute of Technology, Wuhan, Hubei, 430074) Abstract: As a high-risk industry, industrial accidents happen in construction industry now and then. In or-der to prevent and control the occurrence of production safety accidents in construction enterprises effectively, the accident statistics and analysis method is adopted to analyze the larger or more serious production safety acci-dents occurred in 2016. The results show that there were 312 larger or more serious production safety acci-dents throughout the country in 2016. Among these ac-cidents, 42 occurred in construction business which was next only to transportation industry; collapses, falling and electric shock accidents were the main accident types in construction business; the causes of the accidents were mainly divided into construction site reasons and man-agement reasons. Based on the above attx2基板
nalysis results, corresponding control measures are put forward according to the relevant requirements of work safety standardization and the actual situation of the enterprises, which provides technical support for the work safety of enterprises.
key words: construction industry; production safety accident; work safety standardization construction; control measures
CAuSE ANALYSIS OF CORROSION LEAk-AGE OF DILuTION STEAM GENERATOR IN CRACkER[37]
Huang Xinquan.(PetroChina Dushanzi Petrochemical Company, Dushanzi, Xinjiang, 833699) Abstract: This paper briefly introduces the corrosion morphology and corrosion mechanism of tube bun-dle corrosion leakage in the dilution steam generator
of a cracking unit of a petrochemical company and preventive measures for such leakage. From analysis on process flow, process parameters, corrosion morphology and corrosion medium, it is pointed out that the corrosion leakage of dilution steam generator is mainly caused by local alkali condensate corrosion. Although the working environment of the heat exchanger is vapor-liquid two-phase, the temperature of the exchanger is above 170 °C. Meanwhile, the pH value is faintly alkaline,
which indicates that there is no corrosion environment of wet hydrogen sulfide acid. The corrosion morphology is par-tially chiseled, which conforms to the description of API 571 on alkali corrosion morphology. Energy spectrum analysis also shows that there are Na and other alkali metal ions in the failure part. The corrosion environment and corrosion morphology show that there is alkali corro-sion in the failure part of the heat exchanger. In addition, the process conditions require that liquid phase should be much larger than gas phase, and the vapor-liquid ratio should be 1:7 so that the liquid vapor can take away the sediments generated during heat transfer in time. How-ever, since the heat exchanger has been operating at high load, the vapor-liquid ratio cannot meet the requirements at all, resulting in alkali condensate corrosion cracking. This analysis method can provide reference for the judg-ment of similar corrosion cases.
key words: cracker; dilution steam; generator; cor-rosion mechanism
APPLICATION OF quANTITATIVE RISk AS-SESSMENT TECHNOLOGY AT OIL AND GAS CO-CONSTRuCTION STATION[40]
Wang Xin1, Lu Jiaqi2, Wang Zijian3, Han Xiaoming1, Zhang Huabing1 (1.PetroChina Pipeline Company, Langfang, Hebei, 065000; 2. PetroChina Southwest Pipeline Company, Chengdu, Sichuan, 610000; 3. PetroChina Pipeline Company, Shenyang, Liaoning, 110000)
Abstract: Quantitative risk assessment (QRA) can pro-vide important reference for the risk management of oil and gas co-construction station. By applying QRA at an oil and gas co-construction station, this paper calculates the failure consequences of different hazard scenarios. It analyzes the interaction between the leakage of crude oil process area and natural gas process area. Then the paper obtains the personal risk curve and social risk curve of the oil and gas co-construction station. It gives suggestions for the overall layout of the oil and gas pro-cess area of oil and gas co-construction station.
key words: quantitative risk analysis/QRA; oil and gas co-construction station; individual risk; social risk ExPLORATION ON THE kEY POINTS FOR RISk CONTROL OF REPAIR wELDING wITH PRESSuRE IN HYDROCARBON PIPELINE[44] Li Shaolin.(PetroChina Dushanzi Petrochemical Com-pany, Dushanzi, Xinjiang, 833699)
Abstract: Leakage of hydrocarbon pipelines requires on-line welding operations when energy isolation and release are impossible and the risk is controlla-ble. On-line welding of hydrocarbon pipelines is of great risk, therefore, a series of risk control mea-sures need to be implemented. Whether the pipeline has the conditions for on-line welding is certainly the key to prevent uncontrollable events during the operation, especially in the calculation of on-line welding pipelines p
ressure-resistance under actual wall thickness.
key words: hydrocarbon pipeline; repair welding with pressure; on-line welding; risk control TECHNICAL DISPOSAL AND SAFETY CON-TROL MEASuRES OF NAPHTHA TANk BOT-TOM RESIDuE CLEANING[47]
Zhang Lixin, Zhang Lei, Wang Yong, Zhou Yongxin, Sun Kaipeng.(PetroChina Dushanzi Petrochemical Compa-ny, Dushanzi, Xinjiang, 833699)
Abstract: The 20,000 m3 naphtha tank is not easy to be replaced. And the naphtha contains sulfur, resulting in safety problems such as self-combus-tion caused by ferrous sulfide in the tank. Aiming at the problems, the joint workshop of certain ethylene plant summarizes various professional opinions and improves the special program. Tak-ing advantage of the characteristics that naphtha and water are insoluble, combined measures are taken involving implementing water and recycling materials first, then maintaining the working envi-ronment with nitrogen blanket under micro posi-tive pressure and flushing with water. This helps to avoid the bottleneck problems of self-combustion of ferrous sulfide and thorough displacement of combustible hydrocarbon. Through solid process energy isolation and safety control measures, the identification plan and normal operation of naph-tha tank a
re completed on schedule, reaching the three goals of residual material recovery, safe and controllable operation and environmental friendli-ness.
key words: naphtha tank; residue cleaning; techni-cal disposal; safety control
BRIEF DISCuSSION OF THE PRACTICE OF LIGHTNING PROTECTION AND GROuNDING IN AROMATICS TECHNICAL TRANSFORMA-TION PROJECT[51]
Tan Jun, Zhang Qiang.(PetroChina Northeast Refining & Petrochemical Engineering Company Limited, Da-lian, Liaoning, 116023)
Abstract: In the process of production, processing, treatment, storage and transportation, petrochemi-cal plants are prone to produce explosive gases and dust. Most areas of the plant are in the dangerous environment of explosion. Once the explosive gas-es and dust meet with lightning or sparks, they will cause explosion, resulting in equipment damage,
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