Selection of heat exchanger material
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The design pressure for the shell side of the heat exchanger is 2.4 MPa, with the fluid being superheated steam at 360 degrees Celsius. The design pressure for the tube side is 3.63 MPa, and the fluids involved are light benzene, H2, and H2S at a temperature of 200 degrees Celsius. May I ask, experts: can Q345R be used as the material for the shell side, Q345R for the tube side, and 20-grade steel for the heat exchange tubes? Or would it be better to choose some other material sheet?
At such high temperatures, and in the presence of H2, it is not recommended to use 20# steel for the heat exchange tubes; instead, hydrogen-resistant steel should be used as the material for the tube side
Using Q345R for the shell side should be fine, but more considerations are needed for the tube side: for light benzene, a material rated for high hazard conditions is recommended; for hydrogen, hydrogen-resistant steel is advised; and for hydrogen sulfide, the issue of corrosion caused by wet hydrogen sulfide must be taken into account
Section 7.8.2 of HG/T20581-2011 stipulates that a chemical container is in a wet H2S stress corrosion environment when the medium it comes into contact with meets all of the following conditions: 1. The temperature is less than or equal to (60+2×D)℃； P is pressure (MPa). 2. The partial pressure of H2S is greater than or equal to 0.00035 MPA. 3. The medium contains liquid water or is at a temperature below the dew point of water. 4. PH < 7 or cyanide (HCN) is present. I think only the second option could apply; can it not be classified as a wet H2S stress corrosion environment?
It should be (60+2P) degrees Celsius in the previous reply