The effect of solid particles on the evaporation and crystallization processes of the desulfurization wastewater droplet

Abstract

In this study, the thermogravimetric analyzer and the differential scanning calorimetry measurements of the evaporation and crystallization rates of the desulfurization wastewater droplet were conducted. During the measurements, the surface of the droplet was adding different mass of fly ash and adding different species of solid particles, and the volume of the droplet is changing when adding fixed mass of fly ash. The surface of the crystals after evaporation was observed by a scanning electron microscope. A theoretical model analyzing each specific parameter, like the heterogeneous nucleation adsorption sites of density and the radius of the droplet, of the Peclet number was built. The change of the Pe number has the same trend with the experimental results. The experimental results showed that the evaporation rate almost kept in the same level with or without particles. From 1.5 to 3.5 mg fly ash added, higher mass of fly ash on the surface of the 2.0 µL droplet could decrease the crystallization period from 1.2 to 0.95 min and improve the porosity of the crystals, but there was a top limit (crystallization period 0.95 min for fly ash 2.5 mg) for the controlling volume droplet. Particles of SiO2, CaCO3, Fe2O3, Fe3O4 and fly ash could increase the crystallization rate, but Al2O3 could inhibit the nucleation process and increased the crystallization time from 1.2 min (pure wastewater) to 1.25 min. When the volume of the droplet is changing from 0.5 to 2.5 µL, the adding of fly ash dominated the change of the Pe number. The crystallization period increased from 0.9 to 1.15 min and the porosity also increased dramatically.