文献翻译-精馏塔的故障诊断γ射线扫描技术

英文论文翻译 英文原文： Troubleshooting Distillation Column by Gamma Ray Scanning Technique Bao Xiaojun, Wei Weishen, Liu Yansheng, Shi Gang and Shen Fu The key laboratory of catalysis, China national petroleum co., university of petroleum, Beijing 102200, China 【 Abstract】 A digitally controlled three-dimensional gamma-scanning apparatus was developed and used to troubleshoot distillation column in the present investigation. In a 140mm (ID) model column, various malfunction phenomena, both rate and process related conditions and structural problems, which way be frequently encountered in the operation of tray and columns, were experimentally simulated and tested with the developed scanning system. The experimental results showed that the scanning spectra can fairly reflect the simulated phenomena. The salient feature of the scanning apparatus lies in that it integrates the so called grid scan and computer-assisted tomography scan in a single system. It was confirmed that the gamma-scanning technique can serve as an important on-line troubleshooting and maintenance tool. 【 Keywords】 gamma ray scanning , distillation, troubleshooting 1. Introduction It has been widely accepted that gamma-scanning or radiation scanning can play a key role in troubleshooting, predictive maintenance and optimization of distillation columns, although its application has been expanded to other chemical engineering equipment now. It was noted that gamma-scanning provides essential data to (1) optimize the performance of columns (and other vessels); (2) extend column runtime; (3) track the performance-deteriorating effects of fouling and solids deposition; and (4) identify maintenance requirements well in advance of scheduled turnarounds. Bao et al. showed that with elaborately designed scanning apparatus the quantitative information about the hydrodynamic behavior in both tray and packing distillation columns and the solid distribution and coke deposition in the fluid catalytic cracking(FCC) unit could be obtained. The success of these applications demands a better design of the scanning system in order to obtain more detailed description of the process to be evaluated. There are three techniques that use radioisotopes, i.e., grid scanning, tracing, and computer-assisted tomography (CAT) scanning. Their application areas and features had been summarized by Bowman. In the present contribution, a three dimensional digitally controlled scanning apparatus that integrates grid scanning and CAT scanning in a single system was developed and used for the detailed description of malfunction of distillations and structural problems. In addition to the description of the scanning apparatus, various spectra of density /count vs. position profiles and corresponding malfunction performances were presented and discussed. 2. Scanning apparatus For troubleshooting scan, a radiation source (Cs137, 40mCi) and a NaI scintillation detector are aligned on the opposite sides of a column or vessel. They are then synchronously elevated while intensity vs. height profiles are logged. The process change in the column due to its geometrical structure and the flowing media inside it can be distinguished by comparing the empty scan at reduced loadings with an actual troubleshooting scan. The simple scanning apparatus introduced by D. W. Jones and J. B. Jones can be fairly applied for this purpose. For fine process description such as the determination of the three-dimensional gas-solid density distribution in a FCC unit, however, a sophisticated design is demanded. In the present investigation, a patented three-dimensional scanning apparatus was constructed by implementing a rotary platform to the one-dimensional scanning apparatus previously developed to perform rotary and horizontal scan motion. This combination makes three-dimensional scan possible. The detailed configuration of the 3-D scanning system and controlling and logging system can be referred to the two patent applications cited above. 3. Application to distillation column 3.1 Application to tray column Using the one-dimensional scanning apparatus previously developed, various malfunctional phenomena such as complete tray falling, partial damage, tray hole plugging, flooding etc. are investigated. The typical results are illustrated in Figs.1,2 and 3. Fig.1 shows an empty scan for a new tray column of 140mm after installation. It can be seen that the peaks in the density profile are approximately same with the same tray plate geometry. Fig.2 shows a scan with the first tray removed, the third plugged with half of the holes, and the fourth drilled with 2 large rectangular holes. It can be easily concluded that the peak at the place where the first tray plate was originally installed is much lower than that in Fig.1,the peak of the tray 3 is little higher than that in Fig.2, and peak of plate 4 stands between those of the trays 2 and 3. When the column described by Fig.2 was operated with gas (air) and liquid (water) phases under normal conditions, the scan result is illustrated in Fig.3. It can be seen that no froth exists on the first tray and the fourth tray because of complete falling-off of the first tray and serious damage of the fourth tray, and the approach of the froth on the third tray to the second tray indicates obvious flooding. It also reveals that the froth height on the second tray is about 160mm and the normal operation holds. In addition to the results stated above, a series of experiments not quoted here were conducted to identify other malfunctional phenomena such as local flooding, excessive entrainment and weeping which are not so obvious as those mentioned above and to quantify the hydrodynamic characteristic such as the flow regime transition, clear liquid height, froth height, crest liquid height over exit weir, downcomer hydraulics and so on in the tray column, and satisfactory results were obtained. 3.2 Application to packed column For the packed-column application, a grid scan is essentially required. The grid scan should be performed under more precisely controlled conditions. For a packed column, a scan with at least 2 pairs of parallel scan lines which cross in the way as illustrated by Fig.4 is needed. Each of the four scan line orientations are equal distance from source to detector (equidistant chords) and each pair of parallel scan line straddle the center line at equal distance. By analyzing 4 density/count profiles obtained, the rate and process related malfunctional conditions (such as entrainment, weeping, foaming, fouling or plugging of packed bed and excessively heavy or light loading due to operating condition) and mechanical problems (such as crushed, settled, corroded or displaced packing, damaged or plugged distributors and collapsed packed beds) or a combination of both can be fairly identified and located. By the apparatus developed in the current investigation, a series of 22 grid scans were conducted in the laboratory scale Plexiglas packed column of ID 140mm and wall thickness 5mm operated with air and water. The packed bed consists of three parts, i.e., the structured packings made of stainless steel in the lower and upper section, and the -ring packings made of stainless steel in the middle section. On the top of the column is a cross-type liquid distributor. Between the upper structured packing and the distributor there is a vapor space. The empty scan is illustrated in Fig.5. Curves from source A and C in the figure stand higher than curves from B and D. When the liquid was fed into column at the place close to the column wall where scan lines A and C cross by inserting the inlet tube directly to the packed bed instead of feeding through the distributor, the scan is shown in Fig.6. Looking at the curves A and C in the figure, it is clear that they show a much more distinct decrease than curves B and D, indicating channeling in the column. The four curves previously scattered apart now approach to each other so close that they are difficult to be distinguished. When the bed collapses， some part of the bed will become densely packed and some loosely, and even cavities may exist. This situation was simulated experimentally by replacing some -rings with an iron block and some wood balls. The scan for this case is given in Fig.7. It is apparent that the data corresponding to the place where the iron block was lower in counts, or more dense, whereas the data in the place where the packing were replaced by wood balls show only slightly increase in counts. In this case, the scan data should be analyzed with caution. Fig.8 shows a scan for the well-packed column operating under flooding condition. Because flooding prevails in the whole column, all of the four scan curves demonstrate a strong decrease in counts due to liquid accumulation, especially in the vapor space in the column. 4. Conclusions A digitally controlled three-dimensional gamma-scanning system was developed on the basis of the one-dimensional scanning apparatus previously designed and used for the fine description of the malfunctional phenomena in both tray and packed distillation columns. The experimental results show that both the rate and process related conditions and mechanical problems can be fairly identified by the technique developed in the present investigation and this should lay a prospective basis for the application of radiation scanning to predictive maintenance and optimization of distillation column in addition to its troubleshooting use. The very recent application of this scanning system to industrial equipment such as FCC fractionator, sulfur-containing waste water stripper column and standing piper in FCC unit by the authors demonstrated that various malfunctional phenomena could be accurately detected by the technique. ACKNOWLEDGEMENTS The authors wish to thank Professor Chen Jiayong of the Institute of Processes Engineering (formerly Institute of Chemical Metallurgy), Chinese Academy of Sciences for his constant concerns and valuable advices on the current and many other research projects. REFERENCES 1. 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Feng, R.J., Huang, Z.X., Xu, X.M., Shen, F., “A numerical control scanning gamma ray attenuation technique for the investigation of two phase fluid characteristics on distillation trays”, J. Chem. Ind. Eng. (China),40(3), 379-382(1989). (in Chinese) 8. Yan, X.F., Wei, W.S., Bao, X.J., “Development of gamma-ray scanning technique for column failure diagnosis”, Petroleum Refinery Engineering (China), 30(8), 24-27(2000). (in Chinese) 9. Yan, X.F., Li, Z.Q., Zhou, L.G., Xiao, L.X., Wei, W.S., Bao, X.J., “Trouble inspection in column by gamma-ray scanning”, Petrochemical Technology (China), 8(1), 39-41(2001). (in Chinese) 译文 精馏塔的故障诊断射线扫描技术 鲍晓军，魏伟胜，刘艳升，石冈，沈复 重点实验室的催化 中国国家石油公司，中国石油大学，北京 102200 【摘要】 在目前的调查中，一种数控三维射线扫描仪已经被发展和用来检修精馏塔故障，在 140 毫米（直径）塔中，各种故障现象，在塔盘和塔的操作常常地遇到无论速度和进程的相关条件和结构性问题，解决这些问题的方法是用发达扫描系统实验模拟和测试。实验结果表明，扫描光谱可以完美地反映模拟现象。扫描仪器的显着特点在于它集成了所谓的网格扫描和电脑辅助断层扫描在一个系统中。据确认， -扫描技术可以作为一个重要的在线故障诊断和维护工具。 【关键词】 射线扫描；蒸馏；故障诊断。 1. 简介 伽玛扫描或辐射扫描被广泛地认为在查明故障、有预测性的分裂蒸馏塔的维护和优化可能扮演一个关键角色，虽然它的应用现在被扩展了到其他化学工程设备。有人指出，伽马射线扫描提供基本数据来 （ 1 ）优化性能的塔（及其他容器） ; （ 2 ）延长塔运行时间 ; （ 3 ）跟踪业绩恶化的影响污染和固体沉积 ;和（ 4 ）确定维持相当一段时间内要求提前预定逆转。鲍晓军等人证明，利用那精心设计和制作的扫描仪，那些关于流体力学行为的定量信息在塔盘和包装的分裂蒸馏塔和在坚实分布和焦炭可变的催化裂化 (FCC)单位可能获得。这些应用的成功，需要一个更好的设计的扫描系统，以获得更详细的说明的过程进行评估。 这里有三种技术，即使用放射性同位素，网格扫描、追踪，和电脑辅助断层扫描（ CAT ） 。他们的这些应用领域和功能已经被鲍曼概括过。 在目前的实践中，三维数字控制扫描仪，一种集成网格扫描和 CAT 扫描在一个单一的系统开发和使用的三维数控扫描仪已经被研发出来并应用来详细说明蒸馏中产生的故障和结构性问题。除了扫描仪的说明，并对各种谱密度 /伯爵与立场概况和相应的故障表现进行了介绍和讨论。 2. 扫描用具 为了查明故障扫瞄，一个辐射源 (Cs137,40mCi)和 NaI 闪烁探测器被排列在塔或容器的反面。当强度对高度外形被采伐时，他们同步然后被举起。在这个过程中，塔内部的变化它的几何结构和它内部的流动介质可以通过在减少的装货的空的扫瞄区别与实际查明故障扫瞄比较。这种由 D.W.琼斯和 J. B.琼斯介绍的简单的扫描用具最后可以为此而投入使用。精细过程的描述，如确定三维气固密度分布在催化裂化装置中，却要有老练的设计要求。 在当前调查中，获得专利的三维扫描仪实际上是通过对以前被发展的一维扫描仪的一个转台式平台修建进行转台式和水平的扫瞄行动。这个组合使三维扫瞄成为可能。三维扫描系统和控制和记录系统的详细的配置可以提到被援引的二个专利申请以上。 3. 在分裂蒸馏塔的应用 3.1 在塔盘的应用 使用以前开发了的一维扫描用仪，能调查各种各样的例如塔盘完全下跌的，部份损伤，塔盘孔塞住，充斥等故障现象。这些典型的结果在图 1， 2 和 3中展示出来了 。图 1 显示了一个新的直径 140 毫米的塔盘安装后的空扫描。显然在密度剖面图里的顶峰是大约有相同的塔盘几何学的同一事物。图 2 显示除去第一个塔盘的一次扫描， 第三个的洞的一半被堵塞，并且第四个