https://doi.org/10.3390/en12132504
Vaper–liquid equilibrium (VLE) data is vital to the study of absorption and desorption processes, which determines the performance of the CO2 removal effect. Many studies have measured the VLE data of MEA solution at different temperatures and pressures. This study, according to the empirical model from [68], used a ternary aqueous solution to manifest the isothermal equilibrium curves of 30 wt% MEA solution. The equilibrium partial pressure of CO2 correlates with the temperature and CO2 loading, given by Equation (1):
where T is the temperature in K; P is the CO2 partial pressure in Pa; and α is the CO2 loading in mol (CO2)/mol (MEA). This empirical equation could be applied for such a state, where the temperature was between 313.15 and 423.15 K. The partial pressure of water in the stripping process was estimated by the Antoine equation corresponding to the water saturated vapor pressure, as shown in Equation (2) [69]:
where P∗H2O is the saturated vapor pressure in Pa; xH2O is the molar fraction of 30 wt% MEA solution; and T is the temperature in K.
In the heating process, the most relevant parameter is the specific heat capacity, Cp, in kJ/kg°C. Cp is a function of the temperature shown in Equation (3), obtained from the Aspen Plus V 8.8 software, and using the E-NRTL model to calculate:
The heat of absorption accounts for the greatest part of energy consumption in the regeneration process. When it comes to the energy consumption, there is an assumption that the value of absorption heat equals desorption. ΔHabs (kJ/mol CO2) varies greatly with the CO2 loading change and is a correlation given by Equation (4) in [68]: