Pilot demonstration of advanced process configurations for CO₂ capture in biogasupgrading

Upgraded biogas is a replacement to fossil fuels to mitigate greenhouse gas emissions and securing an energy supply in European countries. The amine scrubbing technology for the purpose of biogas upgrading is a mature process capable of simultaneous production of high purity methane (CH4) and carbon dioxide (CO2). The technology is, however, limited by various operational problems and especially the high energy demand for regeneration of the amine solvent. The energy demand for solvent regeneration can be reduced selection of a suitable solvent for biogas upgrading, and by advanced process configurations to integrate heat or enhance the absorption of CO₂.

This thesis includes the demonstration of the amine scrubbing technology for biogas upgrading utilizing a mobile pilot plant at two industrial biogas producers. Various solvents are investigated to reduce the energy demand, or more specifically the specific reboiler duty (SRD), for the amine scrubbing process. These solvents include mature solvent formulations such as 30 wt% monoethanolamine (MEA) and 45 wt% piperazine (PZ) promoted methyldiethanolamine (MDEA) solvents. However, less mature water-lean solvents such as 30 wt% MEA + 15 wt% urea and 30 wt% MEA + 15 wt% ethyleneglycol (MEG) are also investigated. Advanced process configurations are utilized to reduce the SRD further. This includes intercooled absorber (ICA) and rich solvent recycle (RSR), cold solvent splitting (CSS), and lean vapor compression (LVC). The thesis is structured as the following:

Chapter 1 states the motivation and objectives of the research presented in this Ph.D. thesis.
Chapter 2 includes a literature review of biogas upgrading technologies, especially the amine scrubbing technology for biogas upgrading and the implementation of advanced process configurations.
The methodology is presented in Chapter 3 stating the principle for optimization of the amine scrubbing process. The mobile pilot plant and experimental protocol are described, and limitations to the experimental planning of pilot experiments are discussed. Finally, the analytical framework for analyzing the results from the pilot plant is presented.
Chapter 4: This Ph.D. thesis includes 1 accepted paper, 2 submitted manuscripts and 2 manuscripts in preparation. The manuscripts are summarized and discussed according to fulfilling the objectives of the thesis. Finally, the conclusion that it is possible to reduce operational costs is presented (chapter 5) and future works (chapter 6) are suggested. Appendix includes all written papers referenced in Chapter 4.