Understanding the influence of the alkaline cation K + or Na + in the regeneration efficiency of a biogas upgrading unit

Abstract

This paper reveals a regeneration method for a carbonate compound after carbon dioxide (CO 2 ) absorption in a biogas upgrading unit run with caustic mixtures, obtaining precipitated calcium carbonate (PCC) as valuable by-product. This process arises as an alternative to physical regeneration, which is highly energy intensive. This work provides novel insights on the regeneration efficiency of carbonates to hydroxides while also studying the influence of K + or Na + in the caustic CO 2 -trapping solution. The compared parameters were the reaction time, temperature, and molar ratio. Moreover, psychochemical characterization of solids was obtained by means of Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray powder diffraction (XRD), and scanning electron microscopy (SEM) images. The results indicate that regeneration efficiencies are slightly lower when potassium is used instead of sodium, but quite acceptable for both of them. The chemical characterization experiments showed the predominance of calcium carbonate. Overall, the results obtained in this study proved that this process is feasible to upgrade biogas through PCC precipitation, which appears to be a promising economically viable process to synergize carbon capture and storage (CCS) and carbon capture and utilization (CCU).