Removal of SO₂ using ammonium bicarbonate aqueous solution as absorbent in a bubble column reactor

Abstract

In this work, the removal of SO₂ from gas mixture with air and SO₂ by ammonium bicarbonate aqueous solution as absorbent was investigated experimentally in a bubble column reactor. The effects of the concentration of ammonium bicarbonate, the SO₂ inlet concentration of gas phase and the gas flow rate on the removal rate of SO₂ were studied. The results showed that the higher the SO₂ inlet concentration and the gas flow rate, the shorter the lasting time of SO₂ completely removed in gas outlet, and then the faster the decrease in the removal rate of SO₂. The lasting time of SO₂ completely removed in gas outlet increased with increasing ammonium bicarbonate concentration. During the process of SO₂ absorption, there was a critical pH of solution. When the solution pH was less than the critical pH, it would sharply fall, resulting in a rapid decrease of the SO₂ removal rate. A theoretical model for predicting the SO₂ removal rate has been developed by taking the chemical enhancement and the sulfite concentration in the liquid phase into account simultaneously.

Keywords

SO₂ removal / bubble column reactor / removal rate / ammonium bicarbonate / absorbent

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Acknowledgements

The work was supported by the National Natural Science Foundation of China (Grant No. 21076139).

Nomenclature

a	Specific interfacial area per unit volume, m2·m-3
A	Liquid-phase concentration of A, mol·m-3
Ai	i = 1, 2, 3, 4, 5, 6 parameters in Eq. (16)
Ar	Debye-Hückel parameters in Eq. (15)
Br	Debye-Hückel parameters in Eq. (15)
CAL	Concentration of the component A in the liquid bulk, mol·L-1
CAG	Concentration of the component A in the gas phase, mg·m-3
db	Average gas bubble diameter, m
d0	Orifice diameter, m
dR	Bubble column reactor diameter, m
D	Diffusion coefficient, m2·s-1
E	Eenhancement factor
G	Gravitational constant, m·s-2
H	Henry’s law coefficient
Ha	Hatta number
I	Ionic strength, kmol·m–3
ki	i = 1, 2, 3, 4, 5, 6 reaction rate constant
kG	Gas side mass transfer coefficient, m·s-1
kL	Liquid side mass transfer coefficient, m·s-1
kmn	Reaction rate constant in Eq. (28)
Ki	i = 1, 2, 3, 4, 5, 6 equilibrium constant
KL	Total mass transfer coefficient of SO2, m·s-1
KC	Total mass transfer coefficient of CO2, m·s-1
Q	Volume flow rate of gas, L·min-1
Re0	The orifice Reynolds number
ub	Bubble rise velocity, m·s-1

Greek letter

ϵG	Gas hold-up
μG	Viscosity of gas phase, kg·m-1·s-1
μL	Viscosity of liquid phase, kg·m-1·s-1
ρG	Gas density, kg·m-3
ρL	Liquid density, kg·m-3
σL	Surface tension of liquid, N·m-1
\gamma	Activity coefficient

Subscripts

C	Carbon dioxide
G	Gas phase
L	Liquid phase
S	Sulfur dioxide

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