论文总字数：19466字

摘 要

某烯烃厂2#乙烯裂解炉共6台废锅（TLE），在运行半年左右的时间内，先后5次有3台废锅高温端7根列管因泄漏堵管检修，且废锅管板出现减薄鼓包开裂问题，为了分析裂解炉废锅换热管开裂原因，防止事故再次发生，对开裂原因进行了分析评价。其主要研究内容和结论如下：

（1）2#乙烯BA1105裂解炉废锅下管板鼓包泄漏发生在管板中间部位，主要是该型号废锅从两侧进锅炉给水，致使中间部位的流速降低，为氧侵蚀的产生提供了外部的条件。锅炉水在运行中不断受热气化，锅炉水内溶解氧不断浓缩。滞流区所在位置与废锅高温裂解气间接接触，加速了溶解氧的腐蚀。同时下管板选取15Mo3材质的抗拉强度略低，不能满足相关材质要求，上述原因导致高温段管板发生腐蚀穿孔。建议加强水质管理，确保水的溶解氧的量值符合标准。

（2）内换热管发生泄漏的原因是内换热管与下管板之间的角焊缝处沿45°熔合线发生开裂。主要原因是最顶层焊道产生淬硬M组织，其显微硬度远大于母材，造成焊缝与母材组织结构上的差异；同时，在熔合线旁颗粒尺寸大，组成分极不均匀；该区的焊接残余拉应力可达到15Mo3的屈服强度，同时该废锅从高温段两侧进锅炉给水，致使中间换热管受到较大的拉应力。上诉原因综合效应，致使内换热管与管板沿熔合线发生开裂。

关键词：乙烯裂解 废热锅炉 焊缝 裂纹 腐蚀

ABSTRACT

Six gas tube boilors of ethylene cracking furnace in one olefin plant were leakage for about half a year, and root tubes in high temperature end of waste heat boiler was plugged during inspection for 5 times. Meanwhile, the tube plate of waste heat boiler emerged cracks due to thinning bulging. In order to prevent accidents from happening again, the reason of heat exchanger tube cracking were analyzed and evaluated. The main research contents and conclusions are as follows:

(1) 2# BA1105 furnace boiler plate drum package leakage occurred in the tube plate 's middle part, due to the type of waste heat boiler from both sides of the boiler feed water, reducing the flow rate into the tube waste cracking ethylene, providing external conditions for oxygen erosion. In operation, boiler water is continuously heated and gasified, the dissolved oxygen also concentrated continuously. The stagnation region location get in touch with waste heat boiler 's high temperature pyrolyzed gas, accelerating the dissolved oxygen corrosion. At the same time, the tensile strength of tube plate which selecting 15Mo3 as material is slightly low, which cannot meet the quality requirements, that causes high temperature tube plate corrosion perforation. Suggestions about strengthen quality management is to ensure that the water dissolved oxygen values are consistent with the standard.

(2) The reasons for the leakage of internal heat exchange tubes are the cracking of the fillet weld between the inner heat exchange pipe and the lower pipe plate. The main reason is the top bead formation hardening of M , the micro hardness far outweigh the parent material, resulting in differences in the weld metal and the parent metal structure ; At the same time, besides the fusion line the size of particles is very large and composition is very inhomogeneous. The welding residual tensile stress in this area can reach the yield strength of 15Mo3, and the waste heat boiler from both sides of the high temperature section into the boiler feed water, resulting in the middle heat exchange tube is subjected to large tensile stress . The comprehensive effect of the cause of the appeal, the internal heat transfer tube and the tube plate cracking along the fusion line.

Keywords: Ethylene cracking ;Gas tube boilor ;Welding joint ;Cracking ;Corrosion

目录

摘 要 I

ABSTRACT I

第一章 绪论 1

1.1 课题研究的意义及背景 1

1.2 废锅下管板焊缝腐蚀海内外研究近况 2

1.3 废热锅炉腐蚀保护方式研究近况 3

1.4 废锅下管板焊缝泄露主要原因的研究 4

1.5 课题研究内容及技术路线 6

第二章 高温段管板焊缝泄露原因初步分析 7

2.1 情况简介 7

2.2 检查情况 9

2.3 故障类型及泄漏部位 10

2.4 垢样情况分析 11

2.5 泄露原因分析 15

2.6 结构设计原因 16

2.7日常操作原因 6

第三章 内换热管试样高温段进口部位开裂分析及修复改进措施 17

3.1 试样一（泄漏部位1） 17

3.2 试样二（泄露部位2） 26

3.3 修复及改进措施 27

第四章 结论 31

参考文献 32

致 谢 34

第一章 绪论

1.1 课题研究的意义及背景

腐蚀是指材料在外界的环境影响下，所产生的破损或者变质。依据主要工业发展较好国家的考察，每一年由于腐蚀侵蚀等产生的经济上的亏损占到了GDP的百分之2-4^[1]。特别在石化行里面，会经常发笙歌种装备的腐蚀泄露状况，甚至是失火、爆炸等事故也时常发生。因此，有必要研究设备和管线的腐蚀状况。炼油厂、化工厂中，甚至可能占到总投入的百分之十几^[2] ；换热器的投资约占总投资的40%～35%。90%的换热器是由腐蚀引起的。其中，易产生侵蚀部分包括换热管、管板、换热管与管板结合处。因此，探究废热锅炉的侵蚀并制定出保护的方案是必须实行的 。

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