Abnormal corrosion of the tower internals
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Our company has a distillation tower with a diameter of 2400, used for the dehydration of strong organic acids; due to the high corrosivity of these acids, 316L material was chosen for its construction. During a recent maintenance check, a strange phenomenon was observed: several trays in the dehydration section were severely corroded, but not all of them – the corrosion was concentrated on one side, covering about 1/5 of the area, with no signs of corrosion in other areas. The positions of the different layers at the corroded area remain the same above and below the tray. Also: The level has been measured, and there are no issues. I would be very grateful if a friend who understands the sea could provide an answer! This post was last edited by brainandrain on 2009-4-1 16:12]
Is it related to the levelness of the tray?
Is the corroded area located in the same structural part of the tray? It’s possible that the material used in other parts is of satisfactory quality, while the material used in this particular area is not of adequate quality. These several tray components were manufactured in the same batch, using the same defective material. This post was last edited by lxzzl on 2009-3-27 09:36.]
Send a photo of the corroded area and its location so I can take a look.
The level has been measured and meets the standards. The tower body, trays, liquid collection tanks, and internal components of the tower are made from plates of different thicknesses, so there is no risk of substandard materials being used.
Check whether there is a possibility of underscale corrosion in the area. Should the material be retested? This post was last edited by lxzzl on 2009-3-27 09:36.]
It’s definitely the material supplier of the tower internals who cut corners
It may be due to liquid skew flow on the tray, excessive tray flow velocity, a large liquid level gradient, high gas velocity, and erosion caused by these factors that exacerbates the corrosion of the material itself. This post was last edited by brainandrain on 2009-4-1 16:13]
““The corrosion occurs at different layers but the positions above and below the tray remain the same” means that the corrosion takes place in the arcuate area?
If there are no defects in the material of the plate, it is likely an installation issue that has caused the plate to not be level.
It is possible that the flow of the material across the trays is uneven; in areas where the flow velocity is low, strong acid tends to accumulate, corroding those sections of the trays. The cause of this phenomenon could be issues with the process calculations, or defects during the manufacturing or installation of the tower. This post was last edited by brainandrain on 2009-4-1 16:14.]
I suspect that during installation, this area may have been welded, or electrochemical corrosion occurred at the same location where the tray is supported due to differences in material
Agree with what was said on floor 8; it’s likely due to excessively high local flow speeds
Can you be sure? There won’t be any case of substandard materials?
Thank you to all fellow sailors! In addition to the arcuate area, the internal components of the tower as well as the tower itself are corroded, as we use new types of high-efficiency trays in this tower; the tower operates under high load, which increases the likelihood of erosion corrosion. Our two other identical towers use floating valve trays, and corrosion has occurred there as well; however, the corrosion is present on the same layer in all cases, without any bias to one side, and the degree of corrosion on the tower itself is quite mild.
It is difficult to ensure uniform flow patterns on the trays of a distillation column with a diameter of 2400; local accumulation of acidic materials may occur. The severe corrosion of several trays in the dehydration section is caused by electrochemical corrosion due to acid. With a high tower load, erosion and corrosion are certainly possible. The corrosion on the tower body is mild because there is no electrolyte remaining on it.
It’s probably not a problem related to level; could it be that when the packing accumulates, the porosity at the corroded end is greater than in other areas, resulting in higher fluid (gas) flow and thus erosion corrosion?
If the material is fine, then it’s a problem with installation