化工进展 ›› 2021, Vol. 40 ›› Issue (S1): 32-42.DOI: 10.16085/j.issn.1000-6613.2019-2024

• 化工过程与装备 • 上一篇    下一篇

环氧乙烷装置T形三通管件故障原因分析与改进

亢嘉妮(), 何立东(), 范文强, 杨扬   

  1. 北京化工大学化工安全教育部工程研究中心,北京 100029
  • 收稿日期:2019-12-18 修回日期:2021-06-08 出版日期:2021-10-25 发布日期:2021-11-09
  • 通讯作者: 何立东
  • 作者简介:亢嘉妮(1994—),女,硕士研究生,研究方向为流体动力学、机械动力学。E-mail:nmkangjiani@sina.com
  • 基金资助:
    2015年北京市共建-科研与研究生培养项目

Cause analysis and improvement of T-shaped tee fittings in ethylene oxide plant

KANG Jiani(), HE Lidong(), FAN Wenqiang, YANG Yang   

  1. Engineering Research Center of Chemical Safety Education Department, Beijing University of Chemical Technology, Beijing 100029, China
  • Received:2019-12-18 Revised:2021-06-08 Online:2021-10-25 Published:2021-11-09
  • Contact: HE Lidong

摘要:

环氧乙烷(EO)是重要的石化产品,该产品易燃易爆,同时也是一种有毒的致癌物质。山东某化工厂EO生产装置T形三通管件材料与焊缝质量合格、管内介质无腐蚀性,但是频繁出现裂纹故障导致介质泄漏。T形三通裂纹故障原因不明导致该厂几乎半年更换一次T形三通管件,造成了严重的经济损失。为了解决该厂T形三通频繁失效问题,必须准确查明T形三通故障原因,分析T形三通故障机理成为解决问题的关键。本文运用流场分析软件,结合T形三通管线现场故障情况,分析该厂T形三通内部流场特性及故障机理:T形三通管件内部流场存在两个对称的漩涡,导致T形三通流场速度、压力分布不稳定,形成了大范围低于汽化压力的低压区,液体汽化形成了大量气泡,气泡在三通内壁破裂产生巨大的压力冲击,导致汽蚀破坏,使贫水管线T形三通产生裂纹。基于T形三通故障机理,本文提出了3种改进建议,使用Y形三通、圆弧形三通和球形三通3种三通结构代替T形三通结构,并分析这3种三通结构流场特性。数值计算结果表明:提出的3种三通结构能减小三通管件汽蚀破坏,其中Y形三通有微弱的流体漩涡产生,产生低压区体积最小,但管道入口方向需要改变;圆弧形三通结构不改变原来入口方向,流场压力、速度分布更稳定;球形三通流场绝对压力高于Y形和圆弧形,其结构出口及下游流场压力最稳定。本文为解决T形三通裂纹故障提供了新思路,为保障化工厂三通管件的安全提供了技术支撑。

关键词: 裂纹, 三通管件, 计算流体力学, 汽化, 汽蚀

Abstract:

Ethylene oxide (EO) is an important petrochemical product. This product is flammable and explosive, and it is also a toxic carcinogen. In Shandong province, a chemical plant's EO production equipment has qualified T-shaped piping materials and welds, and the medium in the pipe is non-corrosive, but frequent cracks cause the medium to leak. The reason for the failure of the T-shaped tee crack is unknown, causing the plant to replace the T-shaped tee almost every six months pipe fittings caused serious economic losses to the plant. In order to solve the frequently failure of the T-shaped tee at the plant, the cause of the T-shaped tee failure must be accurately identified. Therefore, identifying the failure mechanism of the T-shaped tee becomes the key to solving the problem. This paper uses flow field analysis software, combined with the on-site fault condition of the three-way pipeline, to analyze the internal flow field characteristics and the failure mechanism of the T-shaped three-way device. There are two symmetrical vortices in the internal flow field of the T-shaped three-way device, which results in unstable flow velocity and pressure distribution of the T-shaped three-way flow field. A low-pressure zone with a large range below the vaporization pressure is formed. The liquid vaporizes to form a large number of bubbles, and the bubbles rupture on the inner wall of the tee creates a huge pressure shock, causing cavitation corrosion and damage, and causing the T-shaped tee of the lean water pipeline to crack. Therefore, three improvement schemes are proposed, use Y-shaped tee, arc tee and arc-shaped shaped tee structure instead of T-shaped tee structure, and analyze the flow field characteristics of three tee structures. Numerical calculation results show that the proposed three-way structure can greatly reduce the cavitation damage of the three-way pipe. Among them, the Y-shaped tee has a weak fluid vortex, which produces the smallest volume in the low pressure zone, but the inlet direction changes, not easy to transform; The arc-shaped three-way structure does not change the original inlet direction, the flow field pressure and velocity distribution are more stable, and the flow field characteristics are better than the Y-shaped three-way; Although the absolute pressure of the spherical three-way flow field is higher than that of the Y-shaped and the arc-shaped shaped, the structural outlet and the downstream flow field pressure are the most stable. This article provides a new idea for solving T-shaped tee crack failure and provides guarantee for the safe and effective operation of tee fittings in chemical plants.

Key words: crack, tee-fitting, computational fluid dynamics(CFD), vaporization, cavitation

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