Page 107 - Gas Purification 5E

Alkanolamines for Hjidrogen Sulfide and Carbon Dioxide Removal 97

Temperature. OC
Figure 2-61. Vapor pressure of MDEA solutions as a function of temperature and
concentration. (Union Carbide, 1985)

H2S in MDEA solutions for T = 80 to 260°F, PHzs = 12.6 to 162.6 psia, and w = 20 and 50
wt% MDEA (Oscarson and Izatt, 1990):

H (Btuflb H2S) = -1.24 w - 0.831 1 T -307
(range of H: -350 to -573 Btu/ lb H2S) (2-19)

In equations 2-15 through 2-19, H is the enthalpy of sc-hon (Btu/lb acid gas), w is the
weight percent amine in the solution, T is the temperature (OF), M is the molarity of the
amine solution, and P is the partial pressure of acid gas (psia). The enthalpies are actually
integral values representing all heat released in bringing the solution acid gas content from
zero to the final loading (moles acid gas per mole amine). However, since the enthalpies of
solution were found to be constant with loading for conditions covered by the previous equa-
tions, differential and integd values are the same in this case. The negative enthalpy values