Problems in wet H2S stress corrosion environments
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Section 6.7.2 of HG 20581-1998 states: “A H2S partial pressure of 0.00035 MPa or higher is equivalent to a H2S solubility in water at normal temperature of 10 ppm or higher.””； Section 7.8.2 of HG/T 20581-2011 states: “The H2S partial pressure is greater than or equal to 0.00035 MPa, which is equivalent to a H2S solubility in water at room temperature of greater than or equal to 7.7 mg/L.” What is the relationship between this partial pressure and the solubility of hydrogen sulfide in water at room temperature? According to the new standard, this value has decreased; so how exactly is one value converted into the other? Thank you!
“ppm” stands for “one part per million”; it is a dimensionless value, and can represent either a volume ratio or a mass ratio. “\"mg/L\" is a mass/volume ratio and has units. By converting the volume value to mass, a comparison can be made; that is, \"L * nkg/L = nkg\", which leads to the following conversion formula: mg/L = mg/nkg = mg/n1000 * 1000mg = 1/n10^6 = (1/n) * (1/10^6) = (1/n) ppm. If the solution density is “1 kg/L”, then “1 ppm = 1 mg/L”.
Thank you so much! One more question: in the above standards, it can be simplified by assuming that the density of water at room temperature is 1000 kg/m3. Why is there such a large difference between these two values? Second question: What is the conversion factor between partial pressure and concentration?
Is this question a bit outside the scope of my field? ! But I think this issue is actually quite important, as it relates to certain selection criteria in device design.