Introduction

Post combustion CO2 capture using aqueous amine based solvents is considered to be the most widely used technology in large scale carbon capture and storage (CCS) demonstration projects. An important environmental issue with respect to post-combustion capture is the generation of considerable amounts of degraded amine waste that has to be mitigated or disposed of properly. Amine based solvents for CO2 absorption can degrade due to the presence of gaseous species present in the flue gas such as CO2, SOx, NOx, O2, halogenated compounds and other impurities. Degradation products formed by amine based solvents can include heat stable salts (HSS), non-volatile organic compounds and suspended solids. 

Another degradation compound nitrosamine will be formed by the absorption of NO2 as a nitrite. This nitrite can react with secondary amine e.g. Pz and form carcinogenic nitrosamines e.g. MNPz. MnPz is thermally unstable and will decompose rapidly at stripper conditions. Other containments present in the flue gas such as mercury, selenium, arsenic and other metals will be also present in the amine based solvent.

Key Messages

• For amine based solvents such as: monoethanolamine (MEA), piperazine (PZ), and methyldiethanolamine/piperazine (MDEA/PZ), oxidative degradation contributes more to solvent loss than thermal degradation or volatile losses.

• For coal based power plants, thermal reclaiming may be the preferred option whereas for natural gas based power plants an ion exchange and electrodialysis solvent reclaiming process is the preferred option.

• Based on US regulations the coal-fired thermal reclaimer waste is likely to be classified as hazardous due to the presence of metals, whereas thermal reclaimer waste from NGCC will be classified as non-hazardous.

• Under US regulations waste streams from the ion exchange and electrodialysis reclaiming process will not be classified as hazardous.

• In EU all type of reclaimer waste will be categorized as hazardous.

• There are sustainable ways available to dispose of reclaimer waste such as: by landfilling, combustion in a waste incinerator, firing in a cement kiln, co-firing at the power plant and handing in the waste water treatment plant.