Possible ways to minimize nitrosation reactions during post-combustion CO2 capture process

Abstract

The formation and any emission of nitrosamines in a post-combustion CO capture process are of great interest over the past few years even though its concentration is quite low. In the present research, bench scale nitrosation experiments were conducted using morpholine, a representative of secondary amines, with NO 2 gas and flue gas. Laboratory experiments with 5 M morpholine with 100 ppm NO 2 gas resulted in 88 µg/g nitrosomorpholine (NSMO) in 6 h and 450 µg/g in 24 h. However, coal derived flue gas gave only about 7 µg/g NSMO in 24 h. To prove the inhibitory effect from SO 2 in the flue gas, experiments were conducted with diluted NO 2 gas blended with SO 2 gas in the feed stream. Formation of NSMO was inhibited by about 53.3% when equal concentrations of SO 2 and NO 2 existed compared with the same concentration of NO 2 gas diluted with N 2. The inhibitory effect of SO 2 gas was found to be linear with its concentration. Apart from that, the addition of various inhibitors to the amine solution was also evaluated and isoascorbic acid was found as the best with 86% inhibition activity under the test conditions. Isoascorbic acid was further examined both under simulated CO 2 scrubber and stripper conditions indicating good stability and inhibition performance.

Kinetics of CO2 Adsorption/Desorption of Polyethyleneimine‐Mesoporous Silica

“…However, in addition to having active primary and secondary amine groups, the PEI‐10k also contains the less‐active tertiary amine with the ratio of the primary/secondary/tertiary amines of 1:2:1, respectively. Tertiary amines are active for CO 2 adsorption under hydrous conditions only . Since the PEI‐423/MPS and PEI‐10k/MPS samples contain similar nitrogen contents, it is not surprising that, at the same temperature, the activity of PEI‐423/MPS towards CO 2 adsorption was about 1.25 times higher than the activity of PEI‐10k/MPS (Fig.…”

Selective Removal of Nitrosamines from a Model Amine Carbon-Capture Waterwash Using Low-Cost Activated-Carbon Sorbents

“…Nitrite scavenging has been examined to reduce nitrosamine formation in amine solvents. Previous work from our group showed that nitrite scavengers are effective at inhibiting the formation of nitrosomorpholine from morpholine by removing the key nitrite reactant after it is formed from NO x dissolving in the amine solvent . Several other additives, including ascorbic acid and cysteine, can be reasonably effective at reducing the formation of nitrosopiperazine (NPZ) in a PZ–AMP solvent …”

“…Nielsen et al also showed the thermal degradation of NPZ and formation of NPZ in the absorber yielded a steady-state concentration of near 1 mmol/kg . In contrast to these reports, nitrosamine formation from morpholine is enhanced at higher temperatures up to 145 °C . Therefore, the thermal degradation temperature may vary for a different of nitrosamines, and more research is likely necessary to tailor this approach for different solvents and solvent blends in which different nitrosamines are expected to form.…”

“…Previous work from our group showed that nitrite scavengers are effective at inhibiting the formation of nitrosomorpholine from morpholine by removing the key nitrite reactant after it is formed from NOx dissolving in the amine solvent. 25 Several other additives, including ascorbic acid and cysteine, can be reasonably effective at reducing the formation of nitrosopiperazine (NPZ) in a PZ− AMP solvent. 21 Destroying nitrosamines after they have formed is another mitigation strategy that has been explored.…”

Minimizing solvent degradation and corrosion using multifunctional additive

“…These nitrosamines are of major concern due to their environmental and health impacts. Some inhibitors have been recently reported by our group to prevent nitrosation reaction under post combustion CO 2 capture conditions [6].…”