Study of the MEA degradation in a CO2 capture process based on partial oxy-combustion approach

- The use of a more CO2 concentrated flue gas partially inhibited the oxidative degradation of MEA in semi-batch conditions.
- A 60%v/v CO2 flue gas reduces up to 50% the degradation of MEA compared to post-combustion conditions.
- NH3 emissions were reduced of about 75% at elevated CO2 concentrations above post-combustion case.
- Degradation compounds derived from thermal mechanisms were only identified at 70 °C.

Partial oxy-combustion is a novel approach for CO2 capture that can be applied to mitigate the CO2 emissions from stationary sources, particularly in fossil-fuels power plants. Some benefits have been identified related to the highly CO2 concentrated flue derived from the application of this technology. The hybrid process combining oxy-combustion with post-combustion approach can theoretically lead to around 25% decrease of the overall energy consumption compared with oxy-combustion process. Improvements of the overall CO2 capture process are mainly focused on CO2 chemical absorption stage. Therefore, the evaluation of the solvent behaviour under these new operating is required to verify the strengths of partial oxy-combustion as a promising CCS technology.In this work, the degradation of a conventional solvent - MEA 30 wt% - was studied under rich CO2 environments at typical operating conditions of CO2 absorption. The degradation tests were performed in a semi-batch rig. Variations on key absorption parameters such as temperature and O2 concentration in the flue gas were also studied. MEA losses were determined during the experiments and the most relevant degradation compounds were identified. In this respect, ammonia emissions from the exit gas were measured using a 0.1N sulphuric acid to recovery the ammonia leaving the semi-batch rig.Results from this work concluded that the use of a higher CO2 concentrated flue gas reduced the MEA degradation at absorber conditions. In particular, a 60%v/v CO2 the flue gas reduced up to 50% of MEA losses compared with post-combustion conditions (15%v/v CO2). However, the MEA losses reduction is limited at elevated temperatures. NH3 emissions were also reduced of about 75% when high CO2 concentration were used. This work concluded that partial oxy-combustion technology can substantially reduce the MEA degradation at absorption conditions and thereby this novel CCS approach may become competitive respect to post-combustion.

170The use of a hybrid partial oxy-combustion operations reduced up to 75% the NH3 emissions derived from MEA degradation at absorber conditions.