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

Abstract

BACKGROUND: This paper presents a physicochemical comparison of the solid products obtained from two alternative processes that recycle waste sodium carbonate (Na2CO3) solution, which is produced following the absorption of CO2 in a biogas upgrading unit. Chemical regeneration processes offer an attractive alternative to the energetically demanding standard physical methods. In the first process, sodium hydroxide (NaOH) is regenerated as a precipitate from the chemical reaction of Na2CO3 with calcium hydroxide (Ca(OH)2). The second process shows a path to obtain a valuable sodium chloride (NaCl) and calcium carbonate (CaCO3) rich brine from calcium chloride (CaCl2) acting as a precipitant agent. In both processes, precipitated calcium carbonate (PCC) is obtained as the most valuable by-product, but with varying properties owing to the different origin. RESULTS: The purpose of this work is to analyze physicochemically both variations of PCCs obtained and examine the differences between these solid samples in order to determine which method produces more desirable characteristics in the final product. To this end, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed as characterization methods. The results reflect that both PCCs have a calcite crystal structure, or morph, being as both PCC products originate from CaCl2 that is more similar to commercial calcium carbonate calcite. CONCLUSION: These results confirmed that a pure CaCO3 valuable by-product can be obtained from a biogas upgrading unit with several industrial applications. © 2019 Society of Chemical Industry.