Fired Heater tube corrosion 1

[DonT]

A Fired Heater with a hydrocarbon process gas containing 1 mol% H2S and tubes of ASTM 106 Gr B suffered rapid internal corrosion at the tube outlets ie 4mm in 1.5 years. Process gas outlet conditions are 295 degC at 65 barg and the gas is dry. The scale is a mixture of iron oxides and sulfides.

Is this an expected result with this material selection and conditions, or is there another factor at work?

 

[ggordonstewart]

You are basically making iron sulphide. This is normal under these conditions. You should probably change materials. G. Gordon Stewart, P.Eng.
Gas & Oil Process Engineering Consultant

http://www.ggordonstewart.com/

ggstewar@telusplanet.net

 

[dcasto]

The H2S is also breaking down into H+ ions and there is hydrogen impingment too.

 

You must assess the type of corrosion. I mean if is external, internal or both. If it is only internal, reason maybe some contaminants from the stream as our partner said. If there is some external, you should take into account the tube metal temperature. For killed carbon steel tube as A106, the oxidation due to fire cause tube thining when it is over 500-530 C.