Spray drying of desulfurization wastewater: Drying characteristics, product analysis and potential risk assessment

Abstract The Wastewater Evaporation System (WES) was a reliable and economical way to treat desulfurization wastewater. However, the evaporation mechanism was not clear, and the evaporation product properties were lack of awareness. In this study, the evaporation and product properties were revealed by the single droplet drying (SDD) method and spray drying system. It was found that the evaporation process of wastewater involved the constant rate and falling rate period. The component of the evaporation product from the SDD and spray drying method were similar, mainly consisted of MgCl2, CaCl2, NaCl and CaSO4. Besides, the potential risks of WES were assessed. After wastewater evaporation, the Electrostatic Precipitator (ESP) removal efficiency was enhanced due to the aggregation of fine particles and the enhanced specific resistance. For the influence of WES on comprehensive fly ash utilization, the chloride mass fraction in the final product was lower than 0.06% and could meet strict regulations.