Models for H2 Semipermeation

In the presence of water vapor, which is the case for precombustion CO2 cap-tiu-e apphcations, the equilibrium defect reaction for water (Eq. (14.40)), also known as Wagner hydration, can also apply, which is characterized by the equi-hbriimi constant Kqh [36]  

Unlike pure O2 permeation, H2 permeation can involve the simultaneous mass transfer of H2 and O2 within the membrane depending on the experimental conditions. In the presence of O2/H2O atmospheres, proton conduction is usually dominant at lower temperatures ( 600 °C), while oxygen ion conduction dominates at higher temperatures ( 700 °C) [37]. The following expressions can be proposed from Eq. (14.18) accounting for H2 and O2 permeation [38]  

Alternatively, recalling the equilibrium relation between water, H2, and O2, that is, H2-I- 1/202 OH20 with the equilibrium constant /Ceq.HjO = Phjo/ (phjP ) Eqs. (14.42) and (14.43) can be rewritten as a function of the water partial pres- 

The simplest equation for H2 permeation can be obtained from Eq. (14.42) by implementing the equilibrium condition described by Eq. (14.41) and by assuming that the total conductivity depends neither on the H2 nor on the O2 pressure. In such a situation, if we admit that the ionic mass transfer is essentially attributed to ions, a Wagner-type equation can be deduced for H2 permeation  

If we assume a low vacancy concentration and a much lower fraction of OH centers compared with lattice oxygen ions (i.e.. By 60 and Ooh Bo), Eq. (14.46) can be simplified to Eq. (14.47)  

---

Models for H2 Semipermeation within Supported Ni/Perovskite DPMs... 

---