HEAT EXCHANGER MATERIAL 1

[GabrieleB]

I have a "FLUE gas" plate heat exchanger. Temperature of Flue gas is 400 °C (inlet) 200°C (outlet). Is it enogh to use a common carbon steel like ASTM A 516 Gr.60? Or is better to use high temperature carbon steel like ASTM A 387 Gr.11/22etc.?

 

[metengr]

There is more to this than just "flue gas" temperature. What are the flue gas contents?

 

[GabrieleB]

CO2 8,7%,O2 2,48%,N2 72%, SOx <80ppm, FLUE gas minimum acid dew point temperature 130°C.

 

[metengr]

I would consider Cor-ten A (EN 10025) steel for the anticipated service temperature and flue gas.

 

[rmw]

I second metengr on his recommendation for Corten for this application.

I am puzzled by your post. Are you building a plate Hx or repairing one?

Be careful of the cold end where the air enters - that is to say inspect it often. It can get below dew point at that point on the flue gas side.

rmw

 

[SJones]

If the exchanger is being constructed as a pressure vessel, it is unlikely that a structural steel will be accepted for the pressure envelope. At 400 deg C, the material will be above the creep threshold of 371 deg C indicated in API RP 571.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[rmw]

The use of the terms Flue gas and plate Hx in the same sentence sent my mind to previous experience and connoted to me a device I have applied successfully in fairly high temp flue gas applications.

http://www.bdheat.com/bd/airpr/airpr.html

These normally work in the "inches of water" pressure range so B&PV or API codes don't normally apply.

Corten is commonly used when the materials are not SS.

rmw

 

[metengr]

Actually, for ASME B&PV construction ASME SA 36 can be used for pressure vessel parts with obvious limitations, review UCS-6.

 

[TomEun]

The corrosion of plain CS (No Cr/Mo/Ni/Cu) in the normal operation may not be big issue. However you may have to consider the upset or shut-down condition as well. These conditions may create severe corrosion in the condensate water pocket area in plate type H-EX unless it is successfully maintaining with inert gas or others. Also, the low strength of plain CS at high temperature can be a cause of deformation (distortion-going to leakage) of the thin plate H-EX due to high thermal gradient. Therefore I would not recommend use of plain CS. Corten-A, Cr-Mo steel, 304SS, 316 SS, or nickel alloys may be considered according to the maintenance plan and upset condition.

Thomas Eun