Can someboby give me a clue in selecting an adequate material for Sour Gas operating at 590°C and 0.400kg/cm2.

It will depend on the what kind of plant and process, that is, main process or flare system, also, it is subject to how much H2S is included and what kind of insulation(i.e. heat tracing or bare) you are going to use.

First of all, carbon steel is not applicable becuase of temperature. So, low alloy steel, or austenitic stainless steel, or high nickel alloy steel may be used. It seems that pressure may go to vacuum also.

Material selection is not only subject to design and process conditions but also material cost, maintenance, and construction cost, and ambient temperature.
For the optimized selection, you need to consider all factors.

Therefore; please let us know more detail conditions about your system.

Thanks for your kind attention Sun Wee,
The planta is a main process system and have te following data:
H2S = 12.24%
C02 = 23%
N2 = 42.22%
H2O = 12.56%
SO2 = 6.24%
S_ Vapor = 3.48%
Ambient temp. = 32°C
Please let me know if you need more information.
Rgds,
Sergio Antonio Rivera

Is this Sulfur plant ?
First of all, you do not need to worry about wet H2S at this high temperature. Low Alloy type steel(i.e.A335-P11) may not be applicable because corrosion rate will be too high at elevated temperature and allowable stress is too low at this temperature.
It seems that Type 321 and Type 347 austenitic stainless steel may be acceptable with stabilizing heat treatment in view of corrosion and temperature against the formation of sensitization when exposed to prolong operation temperature range of 425~870 deg. C. Also, Type 310(ASTM A409-310 for large size pipe) is recommended but I would not like to say it is the best choice because it is hard to find this material in the market, that means cost/delivery issues will be involved.
I am wondering if other Alloy(Alloy 6xx/8xx)must be used because of other reasons or Type 321 with stabilization is good enough.
So, please let me know;
1. what kind of project and process you are involved(from/to equipment).
2. pipe size range
3. vacuum condition ?

Thanks Sun Wee
1.- Yes this is Sulfur plant.
2.- From Waste Heat Recovery Unit to Catalytic Sulfur Reactor.
3.- The pipe size range is 12" diam.
4.- No vacuum condition.

If this Sulfur plant, I would like you to check if the operating temperature 590 deg. C or 590 deg. F because conventionally the outlet acid gas temperature of Waste Heat Boiler in 2 or 3 Stage Class Process is controlled about 600 deg. F (316 deg. C). Most outlet acid gas piping in the world are consisted of carbon steel(A106-B) without refractory lining but with heating coil and NACE MR0103 requirements (for SSC prevention).
What I experienced was 300 ~ 380 deg. C wit C.S or Type 321 SS in same process but I never experienced at 590 deg C for Sulfur plant.
Hot gas is channeled from the inter-pass channel of the waste heat boiler into the process piping ahead of the catalytic converters but the temperature of most case is below 600deg F~700 deg F.

If your temp. 590 deg. C is correct, the pipe material would be one of;
1) C.S with refractory lined(but it looks not feasible because pipe size is too small)
2) Type 310 with 3.0 mm C.A but you’d better consult it with material specialist
3) High Nickel Alloy

Anyway, please let me know if the temp. 590 deg C is correct.

If this Sulfur plant, I would like you to check if the operating temperature 590 deg. C or 590 deg. F because conventionally the outlet acid gas temperature of Waste Heat Boiler in 2 or 3 Stage Class Process is controlled about 600 deg. F (316 deg. C). Most outlet acid gas piping in the world are consisted of carbon steel(A106-B) without refractory lining but with heating coil and NACE MR0103 requirements (for SSC prevention).
What I experienced was 300 ~ 380 deg. C wit C.S or Type 321 SS in same process but I never experienced at 590 deg C for Sulfur plant.
Hot gas is channeled from the inter-pass channel of the waste heat boiler into the process piping ahead of the catalytic converters but the temperature of most case is below 600deg F~700 deg F.

If your temp. 590 deg. C is correct, the pipe material would be one of;
1)C.S with refractory lined(but it looks not feasible because pipe size is too small)
2)Type 310 with 3.0 mm C.A but you’d better consult it with material specialist
3)High Nickel Alloy

Anyway, please let me know if the temp. 590 deg C is correct.

I have a Process Department Flow Diagram and according to this, the fluid temperature is 590°C.
Thanks a lot for your recommendation and I will consult a material specialist and show what we discuss.