Reasons for the tube penetration in the VCM converter
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Graphite cooling combined with acid capture is used for dehydrating the gas mixture； Recently, there have been many instances of the converter being used, both in the front-end and back-end systems~ Please, experts, help analyze the reasons!
I don’t know the exact size of the converter or the number of tubes. We have two main points. : 1. There are tiny gaps in the tube welds, invisible to the naked eye, which lead to perforations later on. 2. Excessive and impure HCl
By taking it apart for inspection, can one determine whether it is internal corrosion or external corrosion? Does the converter have a long service life? There are several possibilities: First, there may be an issue with the quality of the hot water; check the water quality ； II. The welding quality of the converter itself does not meet the requirements ； III. The dehydration achieved by the mixed dehydration system does not meet the requirements, as the mixed gas contains a high level of moisture.
1. The mixed dehydration effect is poor; the mixture contains high levels of water, which causes corrosion of the tubes； 2. The pH value of hot water is acidic, causing corrosion to the tubes ； 3. There is a problem with the quality of the converter itself.
Upon disassembly for inspection, it can be seen that there are many leakage points between the upper and lower tube sheets and the tubes； There were also a few units in which, after the leak-sealing was completed and they were put into use, abnormal acid leakage was detected. Upon disassembly, it was found that there were no leaks in the upper and lower plate assemblies either; instead, the issue lay with the tubes passing through them. Therefore, those tubes were removed and replaced! The employees who are constantly working on maintaining the converters are very tired, and the management also joins in with the maintenance tasks!
As a supplementary point, if the newly added catalyst has a high water content and is not dried, it is also very likely to cause leaks in the tubes
Reply to 6# mtkevingarnett: How many minutes is it usually necessary to dry a 3200 converter using nitrogen?
Reply to 7# caocheng: The climate differs between the north and the south. In the northwest region, it usually takes about 48 hours; in areas to the east or west, or where the catalyst contains a high level of moisture, it may take longer. This is related to the operations carried out by the personnel on site; sometimes, the access holes are not opened during on-site work, which results in a loss of two days’ time. Also, we don’t use nitrogen for blowing; circulating hot water from the converter is sufficient.
If the catalyst filling, activation, and drying processes proceed normally, it is necessary to examine the slow-release effect of the circulating hot water
Based on the owner’s description, it seems that the tubes inside the converter you use are joined by expansion bonding. Since the tubes and the tube sheet are not fully sealed during this process, small gaps remain, which create spaces where liquid can accumulate. This leads to corrosion and penetration of the tubes in those areas. It is recommended to use strength welding combined with expansion joining. The converters we produced have been in use by the manufacturer for 3 years without any leakage occurring.
Is it normal for acid to be added to newly installed converters? How long will it take to return to normal? If it has been in operation for a long time and acid suddenly appears, it must be due to corrosion!