Effects of piperazine concentration and operating conditions on the solubility of CO₂ in AMP solution at low CO₂ partial pressure

ABSTRACT

In this study, new equilibrium solubility data for carbon dioxide in aqueous solutions of 2-amino-2-methyl-1-propanol and piperazine (PZ) are provided. The two famous Deshmukh–Mather and Kent Eisenberg thermodynamic models are utilized to predict the CO₂ absorption. The experimental data show that the solubility of CO₂ decreases as the temperature increases. Our data suggest that the addition of PZ has different effects on CO₂ absorption under different partial pressure of the CO₂ in the gas stream. For high partial pressure, the addition of PZ promotes the absorption performance. However, at low CO₂ partial pressure, PZ addition results in less saturated CO₂ loading. The Deshmukh–Mather model can provide an accurate prediction of the experimental data at high partial pressure of CO₂ (i.e. AAD = 3.4%) whereas the modified Kent–Eisenberg model can capture the inverse effects of the PZ at low partial pressure and provides a relatively good approximation of experimental data at low partial pressure (i.e. AAD = 10%).

KEYWORDS:

• CO₂ absorption
• absorption capacity
• vapor-liquid equilibrium
• AMP and PZ
• Deshmukh–Mather model
• modified Kent–Eisenberg model

Nomenclature

AMP 2-Amino-2-methyl-1-propanol

PZ Piperazine

MEA Monoethanolamine

MDEA Methyldiethanolamine

a_i Adjustable parameter

b_i Adjustable parameter

c_i Adjustable parameter

d_i Adjustable parameter

H_CO2 Henry’s law constant for CO₂ in water

K Rate constant

K_i Equilibrium constant of reaction i

K_i′ Equilibrium constant deviation parameter of reaction i

n_i Amount of substance i

n Number of data points

P Total pressure

P_CO2 Partial pressure of CO₂

T Temperature

I Ionic strength

Z_i Electrical charges

m_j Concentrations of the species

V_g Molar volume of gas

Greek letters

β_ij Interaction parameter between species i and species j

γ_i Activity coefficient of species i

α CO₂ loading

Superscripts

i,j Species i,j

cal Calculated

exp Experimental