Reboiler Corrosion 1

[paulspoon]

We are currently experiencing severe corrosion in our reboiler. Two main chemical streams pass through the reboiler at differnet times but never together. These are Water & Acetone and the other is Methanol, DMAc and Water.
Can anyone tell me what is the most likely cause/reaction of the corrosion and how I might go about eliminating/slowing it down?

Thanks
Paul

 

[unclesyd]

Come back with the materials of construction and the operating conditions. In addition to the above can you give description of and where the corrosion is showing up?

 

[paulspoon]

The reboiler is completely manufactured from 316 stainless. The most corrosion was seen on the bottom half of both tube plates where it was so bad in some areas that it could not be re-welded.The reboiler is mounted horizontally.
The two streams that go through the reboiler separtately are:
A)Acetone(35%) & Water(65%)
and
B)DMAc(10%),Methanol(60%) & Water(30%)
Generally, the steam supply to the reboiler is 1.5bar(g).
Hope that this is enough info for you.
Thanks

 

[john19james]

water and methanol combination can also have organic acids. We found a reboiler to a methanol tower that the inlet nozzles took the brunt of the corrosion but the return line to the methanol tower which was MS was wiped continualy by the vapour and did not form a rust film had excelerated corrosion. We also found that the 904L at the top of the tower was good. The reboiler is now changed to incaloy so suspect the 316 is still too "soft" for your application and needs a higher Mo content.

 

[john19james]

Forgot to mention that the Ph of our water was low and we had to use an inhibitor to raise the ph to 7-8.