Valorization of industrial brine sludge waste for augmented spray dry scrubbing of SO₂ using hygroscopic additives

Abstract

• Spray dry desulphurization is a promising alternative to the mature wet FGD. • Industrial sludge waste has mineralogical components relevant to SO 2 capture. • Hygroscopic additives augment water retention properties of FGD reagents. Detailed experiments were conducted using a laboratory-scale spray dryer under controlled conditions to investigate the effects of highly hygroscopic additives on the performance of hydrated lime (Ca(OH) 2 ) in spray dry scrubbing (SDS) of sulfur dioxide (SO 2 ). The experiment involved the preparation of hydrated lime sorbent from industrial brine sludge waste (IBSW) as the starting material. The evaluated additives included sodium hydroxide, ammonium nitrate, ammonium chloride, sodium chloride, and urea. The additives were chosen based on their hygroscopicity, as it is understood that the degree of desulfurization and sorbent conversion in an SDS is significantly enhanced in the prolonged liquid phase. Experiments were conducted at a constant inlet flue gas temperature of 140°C, sorbent particle size of -45μm, while the calcium to sulfur (Ca:S) ratio was varied in the range of 1.0 - 2.5. Slurry with 10 wt.% Ca(OH) 2 was used while varying the additive concentration from 2 to 8 wt.%. The experimental findings revealed that all the investigated additives, except urea, promoted the removal efficiency of SO 2 above baseline. Sodium hydroxide was the best-performing additive achieving 92.06% SO 2 removal efficiency and a calcium conversion of 54.59%. Fourier-transform infrared spectroscopy (FTIR) analysis showed traces of additives present in the sulfation products. Similarly, X-Ray diffraction (XRD) analysis on the final product showed the presence of desulfurization products and the respective additive compounds. Scanning electron microscopy (SEM) depicted reaction products particles as course, irregular, and deformed.