https://doi.org/10.1016/j.ijggc.2022.103597
“Figure 2 shows the regeneration energy as a function of L/G for the simulated fresh and degraded amine solutions. As shown in Fig. 2, for both fresh and degraded solutions, the regeneration energy can be minimized by varying L/G; the minimum regeneration energy occurred at L/G≈0.88. Despite a 10% decrease of free amine, the minimum regeneration energy for the simulated degraded solution only increased 1.23% relative to the simulated fresh solution.
Fig. 2. Regeneration energy as a function of L/G for simulated fresh and degraded solutions.
As shown in Eq. (21), the regeneration energy (qreb) can be described as the sum of the sensible heat (qsens), the heat of water vaporization (qvap), and the heat of CO2 desorption (qdes). Eq. (21) can be rewritten by Eq. (22) following Oexmann and Kather (2010) where cp is the specific heat capacity, ΔTRLHX is the liquid temperature difference at the stripper inlet and outlet, Mi is the molecular weight of species i, Δα is the CO2 loading capacity, wamine is the mass fraction of amine, Pi is the partial pressure of species i, Δhvap,H2O is the heat of vaporization of water, and Δhabs,CO2 is the heat of CO2 absorption. Figure 3 and Table 7 show the allocation of regeneration energy and other process performance indices at the optimal L/G condition, respectively. As shown in Fig. 3, qsens was roughly maintained, and qvap and qdes were slightly increased. As shown in Table 7, for the simulated degraded solution compared to the fresh solution, cp and ΔTRLHX were almost the same, and PH2O/PCO2 was slightly increased. To elucidate the reasons for these results, the relationship between solution properties and process performance indices and the effects of HSS on solution properties are discussed in the following sections. The term ‘CO2 loading range’ in Table 7 is defined as the range between the CO2 loading of the lean solution and the CO2 loading of the rich solution. In contrast to CO2 loading range, a similar term ‘loading capacity’ expresses a delta between the CO2 loading of the lean solution and the CO2 loading of the rich solution.(21)qreb=qsens+qvap+qdes(22)qreb≅cpΔTRLHXΔαMamineMCO21wamine+Δhvap,H2OPH2OPCO21MCO2+Δhabs,CO2MCO2
Fig. 3. Allocation of regeneration energy for simulated fresh and degraded solutions at the optimal L/G condition.
Table 7. Process performance indices related to the regeneration energy at the optimal L/G condition.
| Empty Cell | Empty Cell | Fresh solution | Degraded solution |
|---|---|---|---|
| CO2 loading range lean-rich | mol-CO2/mol-amine | 0.216–0.576 | 0.163–0.521 |
| Δα | mol-CO2/mol-amine | 0.361 | 0.358 |
| cp of lean solution at stripper outlet | kJ∙kg−1∙K−1 | 3.759 | 3.709 |
| Liquid temperature at stripper inlet | °C | 108.7 | 108.6 |
| Liquid temperature at stripper outlet | °C | 120.0 | 120.0 |
| ΔTRLHX between stripper inlet and outlet | °C | 11.3 | 11.4 |
| PH2O at top of the stripper | kPa | 111.5 | 108.6 |
| PCO2 at top of the stripper | kPa | 105.6 | 101.8 |
| PH2O/PCO2 at top of the stripper | – | 1.056 | 1.067 |
“