Page 221 - Gas Purification 5E

Mechanical Design and Operation of Alkanolarnine Plants 207

Acid Gas

Rich Aminez-

Steam

Lean Amine
Figure 3-8. Use of amine regenerator overhead temperature to control amine stripping.

The ferrous sulfide film is sufficiently adherent and nonporous to prevent further corro-
sion as long as erosion-corrosion is prevented by good mechanical design, and impurities
which remove the protective sulfide film, such as cyanide, are not present. The lack of corro-
sion at high HzS/C02 ratios has been exploited in the SNPA-DEA process where acid gas
loadings of 0.77 to 1.0 moles of acid gas per mole of amine have been achieved (Wendt and
Dailey, 1967). High acid gas loadings might also be achieved with other amines at high
HzS/COz ratios; however, no confirming data have been published. In the absence of better
data, it is recommended that the guidelines of Dupart et al. (1993B) as summarized in Table
3-3 for maximum rich solution loadings be followed even though they ignore the effect of
the H2S/CO2 ratio.
Several studies have been published on the effect of the H2S/CO2 ratio on the corrosion of
carbon steel by amine solutions (Froning and Jones, 1958; MacNab and Treseder, 1971;
Lang and Mason, 1958; Dow, 1962). The results of corrosion tests reported by Froning and
Jones (1958) are summarized in Figures 3-10 and 3-11. Both charts show the rate of com-
sion of carbon steel in boiling MEA solutions with nitrogen gas containing COz and/or H2S