https://doi.org/10.1016/j.ijggc.2013.12.005
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4.2.1. Justification for case study
Increased lean MEA concentration leads to higher capture level and greater tendency for equipment corrosion. Good understanding of this relationship is needed to determine the needed concentration that gives best capture level with less consequence on corrosion.
4.2.2. Setup of the case study
To implement this case study, 1000 rpm rotor speed and 0.66 kg/s lean-MEA flow rate were used. The operating conditions are as shown in Table 5. MEA concentration was varied from 55 wt%, 65 wt% to 75 wt% at two lean MEA temperature conditions, 39.5 °C and 20.9 °C.
Table 5. Process conditions for MEA concentration studies.
Variable | 20.9 °C lean temperature | 39.5 °C lean temperature | ||||
---|---|---|---|---|---|---|
Empty Cell | Run 1 | Run 2 | Run 3 | Run 1 | Run 2 | Run 3 |
Rotor speed (RPM) | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 |
Lean pressure (atm.) | 1 | 1 | 1 | 1 | 1 | 1 |
Flue gas flow rate (kmol/h) | 2.87 | 2.87 | 2.87 | 2.87 | 2.87 | 2.87 |
CO2 composition in flue gas (vol%) | 4.35 | 4.35 | 4.35 | 4.35 | 4.35 | 4.35 |
Lean-MEA flow rate (kg/s) | 0.66 | 0.66 | 0.66 | 0.66 | 0.66 | 0.66 |
Lean-MEA composition (wt%) | ||||||
H2O | 41.39 | 33.22 | 22.96 | 41.39 | 33.22 | 22.96 |
CO2 | 3.61 | 0.178 | 2.04 | 3.61 | 0.178 | 2.04 |
MEA | 55.00 | 65.00 | 75.00 | 55.00 | 65.00 | 75.00 |
4.2.3. Results and discussion
Fig. 6 shows the effect of MEA concentration on CO2 capture level at the input conditions shown in Table 5. Capture level increases with increase in MEA concentration at 39.5 °C and also at 20.9 °C lean-MEA temperature. The behaviour reflects increase in hydroxide ions per unit volume resulting in higher degree of CO2 absorption in the lean solvent. This agrees with the findings of Freguia and Rochelle (2003) which showed that the rate coefficient of pseudo-first-order reaction is a function of MEA concentration, meaning that higher concentration of MEA contributes to higher reaction rate. At different temperatures, CO2 capture level shows similar behaviour with MEA concentration though actual capture level is higher at 39.5 °C lean-MEA temperature than at 20.9 °C lean-MEA temperature. Effect of lean-MEA temperature will be discussed further in Section 4.3.
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