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

• Coal derived flue gas showed an inhibitory effect on nitrosamine formation.
• Presence of SO2 inhibits the formation of nitrosamines.
• Isoascorbic acid addition gave 86% nitrosomorpholine inhibition under test absorber conditions.
• Isoascorbic acid showed good stability and inhibition activity at stripper conditions.

The formation and any emission of nitrosamines in a post-combustion CO2 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 NO2 gas and flue gas. Laboratory experiments with 5 M morpholine with 100 ppm NO2 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 SO2 in the flue gas, experiments were conducted with diluted NO2 gas blended with SO2 gas in the feed stream. Formation of NSMO was inhibited by about 53.3% when equal concentrations of SO2 and NO2 existed compared with the same concentration of NO2 gas diluted with N2. The inhibitory effect of SO2 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 the best with 86% inhibition activity under the test conditions. Isoascorbic acid was further examined both under simulated CO2 scrubber and stripper conditions indicating good stability and inhibition performance.

Figure optionsDownload as PowerPoint slide