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Alhnolamines for Hvdrogen Surfide and Carbon Dioxide Removal 129

Figure 2-90. Plant data showing how stripping steam rate affects residual HzS content
in lean MEA solutions at various feed gas HZS/COz ratios. (Rtzgemld and Richadson,
W&l, B). Reprinted with permission from Oil & Gas Journal, Copyright Pennwell
Publishing Go.

Figure 2-92 shows the lean amine C02 loading as a function of the feed gas H2S/C02
ratio and the amount of stripping steam. At feed gas H2S/C02 ratios above 1.0, the lean
MEA solution C02 loading is a strong function of the feed gas H2S/C02 ratio while, for a
given stripping steam rate, the lean MEA solution COz loading approaches an asymptotic
limit for H,S/C02 ratios less than 1. The residual C02 loadings are based on a fixed regener-
ator operating temperature of 252"F, which corresponds to a regenerator bottoms pressure of
about 15 psig (Fitzgerald and Richardson, 1966B). These data can be approxiritely correct-
ed for different regenerator operating pressures by use of the data of Reed and Wood (1941 j
as presented in Figure 2-88. The Reed and Wood chart shows stripping to about 0.1 mole
C02/mole MEA (643 grains/gallon) at 252"F, which is consistent with Figure 2-92 at a
steam rate of slightly over 1.1 lb/gallon.
Figure 2-91 indicates that the MEA solution residual HIS content decreases by a factor of
ten or more as the feed gas H2S/C02 ratio decreases from 10 to 0.1 at a constant stripping