Acid gas removal denotes the capture of CO2 and H2S from natural gas. It is a key step in natural gas processing, and an absolute requirement before pipeline transport of the gas, where, typically, levels of 2 % CO2 and 50 ppm H2S should not be exceeded. If the gas is further processed in an LNG-plant, the limits are typically 100 ppm for CO2 and 4 ppm in H2S. Acid gas removal is carried out at many offshore installations. Examples on the Norwegian continental shelf are the Sleipner, Åsgard and Snøhvit fi elds. Technology for acid gas removal from natural gas is also of importance if CO2 is to be utilized in Enhanced Oil Recovery (EOR). This project is highly relevant to the OG21 goals set out in the “Gas Technologies” target area (TTA8). Acid gas removal by absorption in aqueous amine solutions is a well-established process. This process relies on the large scale use of chemicals which are known to have low biodegradability. Substances which do not biodegrade can accumulate in the environment and thus hav e an impact in the future. In order to avoid this situation, the Norwegian Pollution Control Authority (SFT) has established a system by which chemicals are colour coded according to their inherent properties. A ”green” chemical is regarded as environment ally friendly while a “red” chemical is regarded as environmentally unfriendly. All the commonly used amines for acid gas removal are classified as red. Both SFT and OSPAR require operators to replace ”red” chemicals with more environmentally friendly alt ernatives. For chemicals like the amines mentioned here this represents a real challenge: on the one hand they have to be very thermally stable in order to last as long as possible while in use in the absorber unit; on the other hand, once discharged into the environment they have to degrade as quickly as possible in order not to have a negative impact. It is not known if chemicals that could be considered as alternatives have the desired properties in terms of stability at process conditions combined wit h high degradability in the environment. Further research is required in order to understand the mechanisms involved in degradation. This will then enable the selection of alternative solvents with reduced impact to the environment.
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