Ultrasonic-enhanced phosphorus sludge excited O3 coupled red mud simultaneous desulfurization and denitrification

Abstract

The SO2/NOX pollution in the flue gas of non-ferrous smelting is increasingly serious. At the same time, the accumulation of red mud (RM) in the aluminum industry and phosphorus sludge (PS) in the yellow phosphorus industry has caused serious harm to the environment. To remove SO2 and NOX from the non-ferrous smelting flue gas and realize the resource utilization of the above two solid wastes, an ultrasonic field was used in this study to strengthen the PS excited O3 process and RM wet desulfurization and denitrification process. In the process of O3 excitation, the response surface method (RSM) is used to obtain the optimal O3 excitation concentration, and the optimal reaction conditions are designed based on the response surface optimization model: T is 53.226 °C, power density is 0.4 W/cm2, PS concentration is 51.433 g/L, O3 formation concentration up to 250 ppm or more, which provides a theoretical basis for subsequent desulfurization and denitrification steps. It is proved that this study can replace the expensive traditional O3 generator and provide a basis for NOX removal in the following process. In addition, the optimum experimental conditions of ultrasonic enhanced RM desulfurization and denitrification process were also explored. Under ultrasonic frequency of 28 kHz, ultrasonic power density of 0.4 W/cm2, T of 50 °C, RM concentration of 15 g/L, and stirring intensity of 1000 rpm, the desulfurization efficiency of the reaction system can be maintained above 95 % within 250 min, and the denitrification efficiency can be maintained above 90 % within 250 min. The effect of desulfurization and denitrification in this study is much better than that of traditional methods. Finally, the reaction mechanism of ultrasonic enhanced O3 excitation and RM wet desulfurization and nitrogen removal was discussed by combining adsorption thermodynamics, isotherm, and kinetics. The results showed that the OH· free radicals generated by ultrasonic cavitation and the physical effects brought by emulsification had significant promoting effects.

Keywords

• Red mud
• Ultrasonic
• Phosphorus sludge
• O3 excitation
• Desulfurization and denitration