CO₂ capture pilot campaign: Understanding solvent degradation of CESAR1 in cement plant operations

CESAR1 is regarded as the new benchmark solvent for amine-based CO₂ capture, yet limited data exists on its degradation using flue gas with a CO₂ concentration of 18 vol%. This study evaluated CESAR1 degradation over 3900 h using a pilot plant capturing 1 ton of CO₂ per day from Aalborg Portland cement plant flue gas. In this work, the CESAR1 was composed of 26 wt% 2-amino-2-methyl-1-propanol and 6 wt% piperazine to avoid precipitation in the pilot.

Solvent degradation was evident as the solvent color shifted from clear to orange, indicating the formation of degradation products such as heat-stable salts (HSS) and possibly iron. Analyses identified byproducts like glycolic acid, formate, acetate, and oxalate. Glycolic acid stabilized after initial accumulation, while oxalate continued to increase, suggesting it as a final degradation product.

Flue gas impurities contributed to the accumulation of anions like nitrate, nitrite, sulfate, and phosphate. Nitrate increased significantly due to high NOx levels, with nitrite largely oxidized to nitrate. Sulfate levels, initially low, rose over time, while phosphate concentrations remained minor but gradually increased.

Cations such as calcium, iron, sodium, ammonium, and magnesium were also tracked. Calcium, due to low solubility, was not detected, and iron and magnesium trends were unclear, likely due to precipitation. Sodium and ammonium varied with flue gas composition and operations. Overall, cation build-up was less pronounced than that of anions.

These findings offer valuable insights into CESAR1 degradation and impurity dynamics, aiding plant operators in maintaining solvent health. Understanding flue gas impurities can help identify and remove harmful components pre-capture, accelerating full-scale implementation of carbon capture technology in cement production. It is the first time CESAR1 has been tested on flue gas originating from cement production.