Abstract: Spray evaporation experiments were carried out on the pilot rotary spray drying platform for desulfurization wastewater. The morphology, composition and flowability of the spray-dried products were characterized. The effects of desulfurization wastewater rotary spray evaporation on the operation of the electrostatic precipitator(ESP) and the resource utilization of fly ash were also discussed. Results show that the salt precipitated from wastewater evaporation forms mostly large flaky structure. Some fly ash particles appear obvious agglomeration through the crystal bridge connection. The drying products mainly contain crystalline salts including MgSO₄, CaSO₄·0.5H₂O, SiO₂ and NaCl, etc. The wastewater spray evaporation has a certain agglomeration effect on the fly ash particles, which is conducive to improving the ESP's capture efficiency of fine particles. The flowability of the evaporated products at the bottom of the tower is intermediate between the flowable powder and the cohesive powder. With the increase of the water content in the evaporated products, the flowability of drying products deteriorates. In the experimental conditions, about 90% of the chlorine in the desulfurization wastewater is transferred into the evaporated products and enters into the main flue. The mass concentration of the chlorine in the main flue fly ash increases slightly, but it can still meet the national and industrial standards related to the resource utilization of fly ash.