Abstract
This article presents a regeneration method of a sodium hydroxide (NaOH) solution from a biogas upgrading unit through calcium carbonate (CaCO3) precipitation as a valuable by-product, as an alternative to the elevated energy consumption employed via the physical regeneration process. The purpose of this work was to study the main parameters that may affect NaOH regeneration using an aqueous sodium carbonate (Na2CO3) solution and calcium hydroxide (Ca(OH)2) as reactive agent for regeneration and carbonate slurry production, in order to outperform the regeneration efficiencies reported in earlier works. Moreover, Raman spectroscopy and Scanning Electron Microscopy (SEM) were employed to characterize the solid obtained. The studied parameters were reaction time, reaction temperature, and molar ratio between Ca(OH)2 and Na2CO3. In addition, the influence of small quantities of NaOH at the beginning of the precipitation process was studied. The results indicate that regeneration efficiencies between 53%–97% can be obtained varying the main parameters mentioned above, and also both Raman spectroscopy and SEM images reveal the formation of a carbonate phase in the obtained solid. These results confirmed the technical feasibility of this biogas upgrading process through CaCO3 production.
Highlights
Climate change is one of the major problems that has plagued humanity in recent times, consisting of a significant and lasting modification of local and global patterns of climate on the planet
As it has been set previously, NaOH regenerated was determined by inductively coupled plasma spectroscopy, whileregenerated the maximum to be regenerated can be
The results obtained from this lab scale work have confirmed the technical feasibility of this biogas upgrading process through Precipitated Calcium Carbonate (PCC) production
Summary
Climate change is one of the major problems that has plagued humanity in recent times, consisting of a significant and lasting modification of local and global patterns of climate on the planet. According to the Intergovernmental Panel on Climate Change (IPCC) [1], the main origin is the anthropogenic emissions of so-called greenhouse gases (GHG), due to the use of fossil fuels such as coal, oil and natural gas for the production of electricity, transportation or industrial uses, CO2 being the most relevant among the greenhouse gases For this reason, the use of renewables energies which reduce CO2 emissions could be found as one of the fields most investigated in the last decade [3,4,5,6,7,8,9,10,11]. Biomethane must be submitted to a process called upgrading, which separates the undesired compounds (mainly CO2 ) and adapts its composition to the standards set by the legislation corresponding to that suitable for a fuel gas [15]
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