Switching solvents Based on the corrosion challenges affecting the amine unit in this discussion, evaluating a potential solvent change from MEA to N-methyldiethanolamine (MDEA) for lowering corrosion was necessary. MDEA removes some CO₂; however, it must be formulated with addi - tional ingredients such as piperazine (PZ), for example, to enhance CO₂ removal. This combination has been found to be much less corrosive compared to MEA solvent and has to some extent comparable H₂S and CO₂ removal capability. A commercially available amine unit process simulator was used to determine if the MDEA/PZ solvent combination would treat the feed gas in the amine unit to specifications. Figure 3 shows a process flow used for the simulation. Many data points were used in the simulation. A gas analysis was used to determine if the formulated MDEA/ PZ would meet specifications treating the feed gas with 100-150 ppm H2S and 1.0-1.6 mol% CO2. To meet spec - ifications, the treated gas would need to reach less than 1.0 mol% CO2 and 4 ppm H2S. A base case was simulated using the current MEA solvent along with MDEA and for- mulated MDEA cases (2 wt% piperazine) to determine effects of switching solvents. Results from the simulation are shown in Table 1 . Results The results indicate that the formulated MDEA with pip - erazine and MEA will allow treating at the lower pressure
Recycle-1
20
2
Control-1
18 19 CB
15
Treated gas
16
14
T-518
AC-532
Solution pump
1
9 11
Inlet hydro- carbon
Acid gas
Flash vapour
10
3
5
6
17
13
V-530
Filter pressure drop
8
4
E-518
7
E-531
12
Figure 3 Amine unit process flow
of the facility inlet feed gas. The piperazine predominantly removes CO₂, so its levels can be adjusted as needed. The reboiler duty from MEA to MDEA usually decreases by about 20%, so the original reboiler should have some over - capacity remaining. This is shown in Table 1 as the BTU/ gal is reduced by 23% using formulated MDEA. Due to the lower rich amine temperature achieved with the pipera- zine-formulated MDEA, a higher heat duty will be required from the lean/rich heat exchanger. This should be further evaluated to determine if energy transfer is sufficient for the MDEA solvent change. Using MEA formulated into MDEA for improved CO₂
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PTQ Q4 2025
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