Document Type : Research Paper
School of Chemical Engineering, Yeungnam University, Gyeongsan 712–749, Republic of Korea.
Department of applied Chemistry and Chemical Technology, University of Karachi, Pakistan.
Sustainable Development Study Center, Government College University, Lahore 54000, Pakistan.
Deep eutectic solvents (DESs) comprise ChCl/urea, in combination with water, have been considered in removing acid gases (CO2 and H2S) from biogas. The evaluation of DES for biogas upgrading at relatively high pressure (i.e., >8.0 bar) has not been reported before. The aqueous DES performance has also not been analyzed compared to conventional amines-based solvent (MEA) and ionic liquid (IL). To the best of our knowledge, this is the first study that presents the integration of DES-based biogas upgrading with a mixed refrigerant liquefaction process to facilitate the safe and economical transportation of biomethane over long distances. The biogas considered in this study consisted of 60% CH4, 39% CO2, and 1% H2S. The aqueous ChCl/urea (70 wt%) results in biomethane with ≥99.0 wt% purity and ≥97.0 wt% recovery. Then, this biomethane was liquefied with ≥90% liquefaction rate. Based on the results obtained herein, overall capital, operating, and total annualized cost savings of 2.8%, 25.82%, and 14.26% were achieved using the 70% DES-based integrated process in comparison with the MEA-based integrated process. Whereas 1.41%, 16.85%, and 8.71% capital, operating, and total annualized costs could be saved in comparison with the IL (i.e., [Bmim][PF6])-based integrated process. It could be deduced that the overall cost of the biomethane value chain can be reduced using the proposed approach.
- Biogas upgrading integrated with biomethane liquefaction was investigated.
- ChCl/urea was evaluated for biogas upgrading at relatively high pressure.
- The 70% DES led to biomethane with ≥99.0 wt% purity and ≥97.0 wt% recovery.
- The upgraded biomethane was liquefied through a single mixed refrigerant process.
- Biomethane liquefaction process consumed 0.43 kW/kg-biomethane.