Hi!
I am trying to select the Pipeline and vessel material for a project with 1800PPM H2S and with CO2 Content 1.7 mol%
This is for a compressor package therefore the Pressures will vary across the process.
I've done the following calculations:
Case-1 (Suction): Partial Pressure of H2S @ 95 psig Pressure = 1.36 kPa
Case-2 (Interstage): Partial Pressure pf H2S @ 235 psig Pressure = 3.06 kPa
Case-3 (Discharge): Partial Pressure pf H2S @ 410 psig Pressure = 5.27 kPa
Case-2 (Interstage): Partial Pressure pf (H2S + CO2) @ 235 psig Pressure = 32.37 kPa
Case-3 (Discharge): Partial Pressure pf (H2S + CO2) @ 410 psig Pressure = 55.05 kPa
I've also calculated the pH values for each case using the Annexure D on NACE MR0175:
pH Case-1: 4.5
pH Case-2: 4.5
pH Case-3: 4.5
We usually use the widely used A106 grB as the piping material and SA516gr70 when we are dealing with sweet gas.
NACE MR0175 recommends using table A-2 for selection of materials that fall under region-2.