CARBON STEEL CORROSION - BYPASS TOWER

[ibf]

Hello !

Current Material - A 36 or A 515.

Environment - chlorides (~1.5%); SO2 ( ~ 0.13%) and coal (~ 1% S).

Mechanism : The gas entering the system will be around 1100 C, and will be quenched by fresh air down to about 350 C. Most of the chlorides and alkalis should condense on the dust. The gas / dust stream then will pass to the conditioning tower (bypass). NOTE: Basically, one of the the fuels the plant will use is a liquid waste from the manufacture of industrial chemicals, which leads to the high amount of chloride present in the fuel. The chloride will be in liquid phase from the storage tanks up to the burner pipe , after which point it will be a vapor. The vapor will condense to a solid coating in the cooler portions of the tower.

QUESTIONS :

1. Would a 50 % / 50 % Cr - Ni alloy be an overkill to avoid both pitting and general corrosion , as well as sulfidation ? Any alloy suggestions ? The current carbon steels in use are not lasting too long.

2. Regardless the alloy selected , would carbon steel thermal sprayed with the new selected alloy be an option ?

3. Have you ever heard about "FLUEGARD-425" as a coating option for gas conditioning towers ?

Any suggestions for the above questions would be greatly appreciated.

 

[Goahead]

If you have currently a system operating ("...not lasting too long") you could run a set of tests by placing several coated panels along the gas way, in places with different temperatures where different corrosion mechanisms may occur.
Besides the coating options you quoted, you might test also SermeTel W from

http://www.sermatech.com

and thermal sprayed panels coated with aluminum or Ni-Cr alloys like Metco 43C-NS from

http://www.sulzermetco.com

Coating manufacturers could be contacted for getting their recommendations.

Regards,

http://www.welding-advisers.com/

 

[EdStainless]

The chlorides will stay with the water, your steam will be Cl saturated. Where ever you get condenstation in the system you will have Cl loaded acid. No wonder you are having issues.

You need to look at your system and divide inot areas based on severity of corrosion. In less severe sections a coating is a good option.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[ibf]

Thanks to both of your suggestions and comments.

EdStainless: Any alloy suugestions for the condensation zone saturated in Cl ?

 

[rolledalloy]

Out of curiousity how thick is the mild steel currently in service and has it perforated. How long did this take? This will help indicate the severity of the problem. In most air pollution control ducting we will see materials like 317L, Duplex 2205, AL-6XN (6%Mo), or C-276 used depending on the level of corrosion resistance needed. The temperature of 350C would rule out duplex 2205 which is limited to service below 316C.

In power plants carbon steel ducts have been lined with alloy sheets (wallpapered) as a means to retrofit the existing duct rather than completely replacing it. 16ga or 14ga sheet is typically used.

 

[ibf]

Thickness is ~ 1 inch , and severe corrosion was noticed after 1 year in operation.

Would you please indicate who supplies "wallpaper" ?

 

[CharlesStepanek]

FlueGard-425 is perfectly suited for this environment, it can withstand gases with concentrations of SOx, NOx, and HCL at elevated temps to 425C.

Review the Penta Industrial Website at

http://www.pentaindustrial.com.