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ANA-MARIA CORMOS, JOZSEF GASPAR, ANAMARIA PADUREAN
the reaction rate (r), can be defined in function of the molar concentration of
reactants, as follows: r=k*CA*CB [5], where k is the reaction rate constant The
temperature dependence of the reaction rate constant is presented bellow [3]:
8 ⎝
k = 4.
4⋅10
⋅e
⎛ 5400⎞
⎜−
⎟
T ⎠
3
m / mol⋅
s
The model equations include both partial differential equations and
algebraic equations. The model contains basically mass and heat conservation
equations presented below [3,6,7]. A list of abbreviations used is presented
at the end of the paper.
The mass balance for liquid phase is described by the equations of
consuming both reactants (mono-ethanolamine and carbon dioxide):
∂C
∂t
∂C
∂t
A
B
∂CA
= −vL
⋅ −k
⋅CA
⋅CB
+ E⋅K
G ⋅au
⋅
∂z
∂CB
= −vG
⋅ −b⋅k
⋅CA
⋅CB
∂z
( C −H
⋅C
)
The heat balance equation for the gas phase is presented in the
following equation:
40
AG
CO2
A
(1)
(2, 3)
The effect of a chemical reaction is given by the enhancement factor, E,
defined as the ratio of the absorption rate of a gas into a reacting liquid to that if
there was no reaction [7]. The enhancement factor can be approximated [6,7]:
2 , k ⋅ DCO G ⋅CB
E = (4)
k
The heat balance equation for the liquid phase is presented in the
following equation (the chemical reaction between carbon dioxide and monoethanolamine
is exothermic):
∂T
∂t
∂T
L
Δ H ⋅ k ⋅ C ⋅C
h ⋅ a
( T − )
L L R
A B
u
= −vL
⋅ −
+ ⋅ G TL
∂z
ρsol
⋅ cp
ρsol
⋅ c
sol
psol
The heat transfer coefficient in the gas phase was found by using the
Chilton-Colburn analogy. The value of the heat transfer coefficient depends
of the gas density, diffusivity, heat capacity and thermal conductivity.
The mass balance for gas phase is described by the equation of
consuming carbon dioxide:
∂C
∂t
∂C
∂z
( C − H ⋅ )
AG AG = −vG
⋅ − E ⋅ KG
⋅ au
⋅ AG CO C 2 A
(5)
(6)