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Structural Comparison of Sodium Bicarbonate and Hydrated Lime for Dry SO2 Removal.
* 1 , 1 , 1 , 2 , 3 , 4
1  Clean Technology and Applied Materials Research Group, Department of Chemical and Metallurgical Engineering, Vaal University of Technology, Private Bag X021, Vanderbijlpark 1900, Gauteng, South Africa.
2  Department of Industrial Engineering, Operation Management, and Mechanical Engineering, Vaal University of Technology, Andries Potgieter Blvd, Private Bag X021, Vanderbijlpark 1911, South Africa
3  Clean Technology and Applied Materials Research Group, Department of Chemical and Metallurgical Engineering, Vaal University of Technology, Private Bag X021, Vanderbijlpark, Gauteng, 1900, South Africa
4  Center for Nanoengineering and Advanced Materials (CeNAM), School of Mining, Metallurgy, and Chemical Engineering, University of Johannesburg, Doorfontein Campus, 2028, South Africa
Academic Editor: Juan Francisco García Martín

Abstract:

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.

Keywords: Calcium hydroxide;Emission mitigation;Sodium bicarbonate;Sulphation;Sorbent screening
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