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

Abstract

Summary This paper reveals a regeneration method for a carbonate compound after carbon dioxide (CO2) 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 CO2‐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).

Promoting Sustainability: Wastewater Treatment Plants as a Source of Biomethane in Regions Far from a High-Pressure Grid. A Real Portuguese Case Study

“…Due to its benefits, biogas upgrading techniques for the production of biomethane are increasing in presence at industrial levels [23,24]. Indeed, many studies focused on making the process more affordable have recently been presented [25,26].…”

“…Due to its benefits, biogas upgrading techniques for the production of biomethane are increasing in presence at industrial levels [23,24]. Indeed, many studies focused on making the process more affordable have recently been presented [25,26]. The production of biomethane presents itself as a really interesting option for regions with no natural gas reserves and that are far from a high-pressure natural gas grid.…”

Photocatalytic membrane reactor for simultaneous separation and photoreduction of CO 2 to methanol

“…5 Currently, the most popular technologies for CO 2 separation from the gas mixture are adsorption, absorption, membrane separation, and so on. [6][7][8] Among these methods, membrane application in CO 2 separation has attracted considerable interest because of the advantages, including, easy scaling up and simple operating control. [9][10][11][12] Besides CO 2 separation from the gas mixture that improves the natural gas quality, conversion, or reutilization of the CO 2 content to valuable fuels is also considered to be interesting and feasible route.…”

“…Currently, the most popular technologies for CO 2 separation from the gas mixture are adsorption, absorption, membrane separation, and so on 6‐8 . Among these methods, membrane application in CO 2 separation has attracted considerable interest because of the advantages, including, easy scaling up and simple operating control 9‐12 .…”

Physicochemical comparison of precipitated calcium carbonate for different configurations of a biogas upgrading unit

“…NaOH does not present degradation as amines do, which can produce emissions with elevated toxicity. Moreover, the formation and harmful effects of nitrosamines and nitramines known as potential carcinogenic compounds is characteristic of amines, which does not occur with the use of caustic solvents . Furthermore, caustic solvents are cheaper and more abundant than MEA or PZ, but the main problem with caustic solvents compared with these traditional solvents is the high energy penalty in the regeneration stage via physical methods .…”