Sour Water Stripper Internals 1

[petrotrinsmerv]

We have plans to revamp a Sour Water Stripper using 316L stainless steel internals. However, we anticipate that at times there may be high Chloride content in the sour water due to leakage on seawater condensers, of which we have a few. This may be more for a metallurgist, but if anyone has looked at a sour water stripper recently I would appreciate any info you may have.
Generally I know that 300 stainless steels and high Chlorides don't go together. However, you should not get more than 275 degF or so in this column. Does that make a difference?

 

[robsalv]

Hi Petro...

Our guidelines in simplified terms state that <65DegC and <50ppm will keep the risk of SCC at a minimum.

If you add any H2S, pH changes, stress etc then all bets are off.

Quite simply, in terms of pressure containment, if there's a risk of chlorides mixing with S/S then the best course is to remove either the chloride or the material. Try duplex. Open literature is overflowing with the cautions against austenitic SS and chlorides.

Limited time of exposure is not a justified arguement either. One taste could set off SCC.

On the other hand, you might not care if non pressure containing kit develops some SCC. I'm not sure if I would care providing I had a shortish inspection interval.

What's the stripper made of?? Are internals made of the same material feasible?

Cheers

Rob

 

[25362]

Some comments:

1. Seawater presence from leakages may oblige the use of titanium grade 2, and probably preclude the use of stripped water in the desalters, until the leaks are stopped.

2. When using overhead condensers steam tracing and insulation of overhead piping as well as water washes are effective in removing plugs from salt (plugging) deposits formed below the minimum recommended temperature of 180^oF.

3. When treating cyanide-containing sour water (as from FCC units) overhead condensers require titanium to prevent corrosion under deposits.

4. Modern sour water stripper cooling systems are based on pump-arounds rather than overhead condensers. There is less corrosion and no sublimating (ammonium) salt deposits because these are liquid-filled systems.

 

[petrotrinsmerv]

Thanks to both of you (robslav & 25362) for the information. I suspected there would be a problem. The stripper is Carbon Steel with a cement-type lining. We will be processing FCCU water but we use a pumparound. To my knowledge, this may well be the first use of this material for trays in our refinery, but I believe the case will be pretty strong. I will be forwarding this thread to the engineers responsible for preparing the BEP.

 

[vict6]

One comments.

I think you'll need to have a look at the NACE MR 0175 which gives guidelines to materials selection for Sour Service and gives limits for Temperature, Cl concentration e H2S contents.
This standard is more concerning Oil and Gas production, but i think can give you an idea of the application limits for AISI 300 class.

Hope will help.