Corrosion of tubes in triple-effect evaporators
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The counter-current triple-effect evaporators used in our company have experienced corrosion of their tubes (the medium inside the tubes is 12% sodium sulfate along with a small amount of sodium chloride); holes with a diameter of 1 cm have appeared in various locations along the tubes, and the areas surrounding these holes are very thin and appear blade-like. Let’s analyze the reasons.
The tube material should be stainless steel, as the medium contains sodium chloride; it is likely that chloride ions are responsible for destroying the passivation layer and causing pitting.
The poster should clarify the materials and operating conditions
Agree with the view from the 2nd floor; chloride ions are very harmful to stainless steel surfaces
With such a high amount of chloride ions, how is it possible not to experience corrosion?
It’s only been a month – isn’t that too short a time? What material do you suggest? Is 316L too expensive?
We recommend using graphite heat exchangers, as they can be used for a long time under boiling conditions at any concentration of this medium without suffering from corrosion.
Thank you all. The operating temperature is between 90–110°C, and the pressure ranges from nearly -0.06 MPa to 0.1 MPa. I’m using seamless steel pipes that comply with the 8163 national standard
Chloride stress corrosion is the main issue, with some intergranular corrosion present as well
It’s impossible not to cause corrosion with such a high concentration of chloride ions
The cost of poor material selection. Optional 316L, titanium
Chloride ions cause severe corrosion of steel materials; to prevent such corrosion, tube bundles with ceramic linings can be used, which are very effective
A more mature approach for situations like this is to replace the material in contact with the liquid mixture with titanium alloy
Under the operating conditions mentioned by the poster, using a graphite heat exchanger offers the best cost-performance ratio.