英文论文翻译英文原文：Troubleshooting Distillation Column by Gamma Ray ScanningTechniqueBao Xiaojun, Wei Weishen, Liu Yansheng, Shi Gang and Shen FuThe key laboratory of catalysis, China national petroleum co., university of petroleum, Beijing 102200, ChinaL 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, troubleshooting1. IntroductionIt 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 efleets 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 apparatusFor troubleshooting scan, a radiation source (Cs137, 40mCi) and a Nal 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 column3.1 Application to tray columnUsing 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丄2 and 3. Fig.l shows an empty scan for a new tray column of ① 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丄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)。