New technique for energy efficient CO2-separation through absorption with a sterically hindered amine

Sammanfattning: The degree project described in this report also acts as a deliverable for a research project. The research project focuses on a new technique for the upgrading of biogas. This new technology uses a sterically hindered amine to absorb carbon dioxide from the biogas to raise its energy value. The amine used for this method is 2-amino-2-methyl-1-propanol or AMP. When absorb-ing carbon dioxide with this amine and with an organic solvent, the chemically formed com-plex forms precipitate. The precipitate can then be separated from the solvent to enable regen-eration of the precipitate only and not all of the solvent as the methods used today. This will lower the heating demand. This separation and regeneration is what separates this method from the commercially available. The steric hindrance of the AMP weakens the bond with the carbon dioxide. This weaker bond is what makes it a promising candidate, since there is a pos-sibility that the AMP carbamate can be regenerated using low grade heat at 70-90°C, which makes it possible to use warm water instead of steam. The deliverable for the research project is to give a proof-of-concept. To do this, an experi-mental setup has been built. The setup was run with live conditions with a 25 % CO2 gas inlet, to mimic raw biogas. The solvent consisted of 10 Vol% AMP and the rest 1-Methyl-2-Pyrrolidinone or NMP at a liquid flow of 20.2 l/hr. CO2 was absorbed and regeneration was possible at temperatures at and be-low 90°C. These results proved the concept. More work is needed with the setup for future tests. The setup should be adapted with gauges for temperature measurements as well as flowmeters for the gas outlets. The rubber tubing needs to be replaced with more resistant tubing. Another separation unit needs to be found for better separation. More optimization of the conditions needs to be done for the setup to be run fully continuous.