Alkaline absorbents for SO2 and SO3 removal: A comprehensive review.

Injection of an alkaline absorbent into the flue gas can significantly reduce SO2 and SO3 emissions. The article presents alkaline absorbents employed in industrial processes to remove SO2 and SO3 from flue gases, detailing their characteristics and applications across various process conditions. It summarizes the mechanisms and influencing factors behind SO2 and SO3 removal, outlines the impact of multi-component gases, particularly SO2, on SO3 removal in actual flue gases, and elucidates this competitive phenomenon from a theoretical standpoint. The article compares the application scenarios and efficiencies of alkaline absorbents across different processes, identifies the optimal combinations of various absorbents and processes, and proposes a synergistic approach for the removal of SO2 and SO3. The findings demonstrate that by injecting calcium- or sodium-based absorbents into dry processes, SO2 and SO3 can be removed efficiently and cost-effectively, with process optimization and absorbent modifications further enhancing the SOx removal efficiency. In the future, by blending two or more absorbents and applying them to dry processes, a synergistic removal of SO2 and SO3 can be achieved.

O3 oxidation combined with semi-dry method for simultaneous desulfurization and denitrification of sintering/pelletizing flue gas.

With the vigorous development of China's iron and steel industry and the introduction of ultra-low emission policies, the emission of pollutants such as SO2 and NOx has received unprecedented attention. Considering the increase of the proportion of semi-dry desulfurization technology in the desulfurization process, several semi-dry desulphurization technologies such as flue gas circulating fluidized bed (CFB), dense flow absorber (DFA) and spray drying absorption (SDA) are briefly summarized. Moreover, a method for simultaneous treatment of SO2 and NOx in sintering/pelletizing flue gas by O3 oxidation combined with semi-dry method is introduced. Meantime, the effects of key parameters such as O3/NO molar ratio, CaSO3, SO2, reaction temperature, Ca/(S+2N) molar ratio, droplet size and approach to adiabatic saturation temperature (AAST) on denitrification and desulfurization are analyzed. Furthermore, the reaction mechanism of denitrification and desulfurization is further elucidated. Finally, the advantages and development prospects of the new technology are proposed.

Simultaneous removal of SO2 and NO using a spray dryer absorption (SDA) method combined with O3 oxidation for sintering/pelleting flue gas.

Based on the demand of sintering/pelleting flue gas ultra-low emission, a semi-dry method using a spray dryer absorber (SDA) combined with O3 oxidation was proposed for simultaneous removal of SO2 and NO. Effects of O3 injection site, O3/NO molar ratio, and spray tower temperature on the removal efficiencies were investigated. It was revealed that both desulfurization and denitrification efficiencies could reach to 85% under the conditions of setting O3 injection site inside of tower, O3/NO molar ratio 1.8, spray tower temperature 85°C, Ca/(S + 2 N) molar ratio 2.5 and slurry flow rate 300 mL/hr. CaSO3/Ca(OH)2 mixture slurry was used as absorbent to simulate operating conditions in iron and steel industry. The result shows that the addition of CaSO3 weakens both removal efficiencies. In addition, the reaction mechanism of simultaneous removal of SO2 and NO using SDA combined with O3 oxidation was proposed.

Effect of octenyl succinic anhydride starch ester by semi-dry method with vacuum-microwave assistant.

Corn starch was esterified with octenyl succinic anhydride (OSA), in which semidry method assisted with vacuum-microwave treatment was used under the alkalescent condition. The effect of vacuum treatment on esterification was studied. The products were characterized by Fourier transform infrared (FT-IR) spectroscopy, 1H nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and X-ray diffraction. And the emulsifying properties were investigated with the emulsifying capacity (EC), emulsion droplet size and confocal laser scanning microscopy (CLSM). The degree of substitution (DS) of OSA starch increased significantly (ρ < 0.05) assisted by the vacuum-microwave treatment with the same dosage of reactant compared with the microwave only. The results confirmed the formation of OSA starch prepared by the method, all reactions occurred mainly on the surface of granules, and had no significant effect on the starch crystallinity. The OSA starch was a good polymeric surfactant with good abilities both in hydrophilic and lipophilic. The emulsifying capacity, degree of substitution of the OSA starch prepared by the method attractively showed vast potential for scale production.