Drying of wet particles during spray evaporation of desulfurization wastewater

In flue gas evaporation systems to treat desulfurization wastewater, interactions between wastewater droplets and fly ash could result in the formation of wet particles. Drying of these wet particles could become the bottleneck of the overall drying efficiency, while the drying of these wet particles is rarely explored. This study examined drying characteristics of mixtures of practical desulfurization wastewater and fly ash under hot-air drying conditions. Drying kinetics were modeled by classical diffusion-based and data-driven models. Results show the addition of fly ash impeded the drying rate, increased the sample temperature, and prolonged the following drying. This impact was more prominent in situations with low temperatures and high salinity. The fitting results suggested Page model was the most accurate (R-2 > 0.996) among classical models. SVR and MLP achieved R-2 values of 0.992 and 0.998 on average. The models' validity was tested by additional experiments, and the optimized Page model and MLP model provided more precise predictions. The effective moisture diffusivity ranged from 1.58 x 10(-8) m(2)/s to 1.72 x 10(-7) m(2)/s, and the activation energy was 36.36 kJ/Mol. Orthogonal experiments revealed higher temperatures accelerated drying, whereas increased salinity and reduced particle sizes obstructed pore structures and thus extended drying time