Table 3
Henry’s law constants in anaerobic digesters
Substances
name
T (◦C) Henry’s law constants References
(mol/l atm) (atm l/mol) log(KH
i−W)
H2 25 1164.224 0.000858 3.066 [25]
O2 25 716.764 0.0014 2.855 [25]
CO2 25 21.82 0.0458 1.338 [26]
CH4 25 640.0 0.0016 2.806 [27]
C2H4O2 25 0.0012 850.0 −2.920 [26]
equilibrium corresponds Raoult’s law for pure ideal solvent
(water).
KHW
= fW
aWf
◦W
∼=
Psat
W (6)
where the fugacity of water (fW) in gas phase becomes saturated
water pressure (Psat
W ).
2.2.2. Electrolyte ionisation equilibrium
The equilibrium relation is described by the ion association,
in which the chemical potential (μi) of component (i) equals
the summation of chemical ion potentials (μ
+
j andμ
−
k ) of its
constituent ions (j) and (k) for the component (i).
viμi = vjμ
+
j
+ vkμ
−
k (7)
The electrolyte ionisation equilibrium in anaerobic digesters
is characterised by dissociation constants (Ka) for reactions of
the ion composites. The dissociation constants are expressed by
Eqs. (2) and (7).
Ka = exp
viμ
◦
i
− vjμ
◦+
j
− vkμ
◦−
k
RT
=
(a
+
j )vj (a
−
k )vk
ai
vi
(8)