Performances of CO2 absorption from biogas and CO2 regeneration of solvents including monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), potassium glycinate (PG), potassium L-prolinate (PP), potassium sarcosinate (PS) and potassium L-ornithinate (PO) were investigated in this study by using a bubbling CO2 absorption and regeneration reactor. The results showed that when the solvents were saturated with CO2 under 35°C coming from the typical biogas atmosphere which consists of 40 vol.% CO2 and 60 vol.% CH4 at the ambient pressure, the equilibrium CO2 loadings of solvents after CO2 absorption were ranked from high to low value: PO (1.412 mol·mol-1), PA (1.262 mol·mol-1), PS (0.710 mol·mol-1), DEA (0.701 mol·mol-1), PP (0.674 mol·mol-1), PG (0.610 mol·mol-1), MEA (0.555 mol·mol-1), TEA (0.391 mol·mol-1). In addition, each solvent studied has a special CO2 loading range within which CO2 absorption rate can be maintained at a plateau with higher value. But once the CO2 loading exceeds it, CO2 absorption rate will drop sharply. And this special CO2 loading range of MEA is narrow than that of amino acid salts experimented in this study. After regeneration of CO2-rich solvents at 75°C formed in the CO2 absorption process by using pure CH4 to act as stripping gas, results showed that TEA can be regenerated to obtain the lowest lean CO2 loading, which is lowest than that of these solvents mainly forming carbamate ions during CO2 absorption. And the stability of carbamate ions can give an order from weak to strong: DEA, MEA, PG, PS, PP, PO, PA. Finally, the comprehensive absorption-desorption performance showed that all the amino acid salts have the greater affinity towards CO2 and PG, PO and PS show outstanding CO2 absorption-desorption comprehensive performance, which is superior to MEA and other amino acid slats tested, implying that it can be considered as the most promising alternatives to replace MEA used in CO2 removal from biogas.
|Journal||Tongji Daxue Xuebao/Journal of Tongji University|
|Publication status||Published - Dec 2012|
- Amino acid salt
- Biogas upgrading
- CO removal