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. 2019 Nov 13;9(11):152.
doi: 10.3390/membranes9110152.

Effect of Carbon Dioxide Loading on Removal of Heat Stable Salts from Amine Solvent by Electrodialysis

Evgeniia Grushevenko  1 , Stepan Bazhenov  1 , Vladimir Vasilevsky  1 , Eduard Novitsky  1 , Maxim Shalygin  1 , Alexey Volkov  1
Affiliations

Effect of Carbon Dioxide Loading on Removal of Heat Stable Salts from Amine Solvent by Electrodialysis

Evgeniia Grushevenko et al. Membranes (Basel). .

Abstract

Heat stable salts (HSS) formed and continuously accumulated in the amine-based solvents due to solvent degradation and impurities in the feed gas can dramatically change the efficiency of the amine scrubbing process. HSS can be removed by using different methods including membrane separation such as electrodialysis (ED). In this work, we studied the effect of CO2 loading of the lean 30 wt % monoethanolamine (MEA) solution on the efficiency of HSS removal and MEA loss. In the model MEA solution containing HSS on the level of 48 meq/L, the carbon dioxide concentration was varied from 0.2 down to 0 mole (CO2)/mole (MEA). The reclaiming of model MEA solution was carried out by lab-scale two-stage ED unit when the concentrate stream after the first stage was additionally treated using ED (second stage) that allowed reducing MEA loss. It was shown that the decrease of carbon dioxide content from 0.2 down to 0 mole (CO2)/mole (MEA) resulted in a substantial reduction of both parameters-the MEA loss and the specific power consumption with respect to extracted HSS (from 140 down 37 kJ per 1 g of recovered HSS anions). This can be explained by the drop in the total concentration of ions formed by the interaction of MEA solution with carbon dioxide. However, the change of CO2 loading is associated with additional power consumption towards further solvent regeneration in the column. Based on the preliminary estimations of power consumption required for additional CO2 stripping with the respect to the power consumption of ED stage, it seems that lean solvent CO2 loading of 0.1 mole/mole provides an optimum for the power input at 25.9 MJ/kg(solvent).

Keywords: carbon dioxide; electrodialysis; heat stable salts; monoethanolamine; reclaiming.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The principle of heat stable salts (HSS) removal from monoethanolamine solvent with electrodialysis (CEM—cation-exchange membrane, AEM—anion-exchange membrane).
Figure 2
Figure 2
Flow scheme of two-stage electrodialysis (ED) system. D1—first stage dilute, C1—first stage concentrate, D2—second stage dilute, C2—second stage concentrate, V1 and V1—buffer tanks.
Figure 3
Figure 3
Lab-scale ED setup flow scheme: V1—dilute (feed) tank, V2—pre-cathode tank, V3—pre-anode tank, V4—concentrate tank, P1–4—pump, ED—electrodialyzer, DC—power supply, C—conductometer.
Figure 4
Figure 4
The change of total HSS anions concentration in the feed in time with the respect to initial CO2 loading (ED I).
Figure 5
Figure 5
Kinetic of specific HSS anions recovery at different CO2-loading.
Figure 6
Figure 6
Kinetic of total HSS anions recovery during the second stage of ED reclaiming (ED II).
Figure 7
Figure 7
Monoethanolamine (MEA) loss at the first stage of ED reclaiming (ED I) of model MEA solution at the different solution CO2 loading.
Figure 8
Figure 8
CO2 loading of MEA solutions at the first stage of ED reclaiming (ED I) of model MEA solution.
Figure 9
Figure 9
The heat duty of reduction of CO2 loading from 0.2 mole/mole down to require level (1), ED reclaimer (2) and overall energy consumption (3) for combination of two units.
See this image and copyright information in PMC

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