4. Conclusion
In this study, a general model is proposed to calculate carbon dioxide
solubility in amine solutions, which will be used for predicting the
properties of the system using the CPA equation of state and TEA and
pyrazine water soluble absorbents. The reason for the use of piperazine
is that TEA has barriers and disadvantages due to its limited loading
capacity and absorption capacity. In recent years, the study has focused
on the use of new and optimal materials to absorb acidic gas from
natural gas, according to the results and reports of research sources of
piperazine, as a trusted enhancer and additive.
The deviation of the predicted values from the experimental data by
the simulated model at three operating temperatures of 313, 333, and 353
K were 6.3%, 6.7% and 7.3%, respectively, indicating a lower error
reported at the lower temperature due to less complexity of the
assumptions and also the modeling conditions are at lower temperatures.
By increasing temperature, the amount of carbon dioxide absorbed in the
adsorbent solution decreases due to the increased carbon dioxide
incidence in the gas phase at higher temperatures. Increasing the
temperature reduces the absorption efficiency, and the reason is that
the absorption of carbon dioxide by thermally absorbing the ammonia
absorbent. With increasing temperature, the gradient of absorption is
more lenient and the slower absorption at very high temperatures can be
due to the structural changes in the amine absorbent solution or the
breakdown of adsorption bonds formed in the adsorption process at higher
temperatures. The deviation of the model is also 2.9%, 5.9%, and
7.4%, in comparison with the literature data, at operating pressures of
15, 60 and 110 kPa, which indicates that although high pressure for the
reasons above mentioned it improves the absorption conditions, but due
to the lower complexity of modeling conditions and assumptions, the
reported deviation is lower in lower and moderate pressures. Also, by
increasing the concentration of piperazine in the amine absorbent
solution, the amount of carbon dioxide absorption increases due to the
increased reaction rate of amine solution with carbon dioxide in the
presence of piperazine. But in higher concentrations, the increasing
trend of absorption of carbon dioxide in the adsorbent solution is due
to the increased viscosity of the adsorbent solution due to the
excessive increase in the adsorption potential of the piperazine, and
the absorption rate will be less incremental due to this. The review and
comparison of the model results with available experimental data
suggests that the results show good accuracy and proximity to
experimental data. So, the simulated model can be used as a reliable
model for predicting carbon capture absorption results in a variety of
conditions, with less experimental data.