Structural Comparison of Raw Sodium Bicarbonate and Hydrated Lime for Dry SO2 Removal †

Abstract

In dry flue gas treatment systems, gas–solid interactions are modulated by the reagent molecular composition and physical attributes. In the present investigation, sodium- and calcium-based sorbents were screened for structural and compositional variations for their subsequent application in sulphur dioxide capture. Mined sodium bicarbonate (NaHCO3) in its unprocessed form and commercial-grade hydrated lime (Ca(OH)2) were subjected to morphological analyses, employing scanning electron microscopy (SEM), particle size distribution (PSD), Brunauer–Emmett–Teller surface area evaluation, and Barrett–Joyner–Halenda (BJH) pore structure classification. Fourier Transform Infrared Spectroscopy (FTIR) was leveraged for a surface elemental chemical assessment. Pursuant to the BET report, Ca(OH)2 presented a larger specific surface area (4.2360 m2/g) as opposed to NaHCO3 (0.2303 m2/g), which was supported by the weighted mean value (D43) from the PSD analysis. Although Ca(OH)2 had a higher pore volume (0.089822 cm3/g), the totality of the NaHCO3 pore size (117.312 Å) was classified as mesoporous. The SEM assessment suggested that the lower NaHCO3 surface area stemmed from larger particle sizes. The FTIR spectrum indicated a greater carbonate concentration in the NaHCO3 sorbent material, which also structures the pore morphology of the reagent. These findings offer critical information pertinent to the intricate dry flue gas desulphurisation process. The data generated will help us to design fixed bed experiments in a subsequent study.