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

In dry flue gas treatment systems, gas–solid interactions are modulated by the reagent's molecular composition and physical attributes. In the present investigation, sodium- and calcium-based sorbents were screened for structural and compositional variations for subsequent application in sulphur dioxide capture. Mined sodium bicarbonate (NaHCO₃) in an unprocessed form and commercial-grade hydrated lime (Ca(OH)₂) were subjected to morphological analysis 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 used for surface elemental chemical assessment. Pursuant to the BET report, Ca(OH)₂ presented a larger specific surface area (4.2360 m²/g) compared with 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 stems from larger particle sizes. The FTIR spectrum indicated a greater carbonate concentration in the NaHCO₃ sorbent material_, which also determines the pore morphology of the reagent. These findings offer critical information that is pertinent to the intricate dry flue gas desulphurisation process. The generated data will be the basis of fixed-bed experiments in a subsequent study.