Study of Main Solutes on Evaporation and Crystallization Processes of the Desulfurization Wastewater Droplet

Abstract

In this study, the evaporation and crystallization processes of the desulfurization wastewater droplet with different concentrations of main solutes were analyzed by TGA and DSC methods. The drying crystals were scanned by a scanning electron microscope. The supersolubilities were measured by the laser intensity detecting method. A mathematic model was built to investigate the relationship between the evaporation and crystallization rates and the species and concentrations of the solutes. The results show that, comparing SO4 2– with Cl–, the higher concentration of SO4 2– gives higher evaporation rate (4.75 min of 0.006 mol NaCl, 4.5 min 0.003 mol Na2SO4) and lower crystallization rate (2.2 min of 0.006 mol NaCl, 2.5 min of 0.003 mol Na2SO4). This is because the vapor pressure is higher and the supersolubility is lower when the concentration of SO4 2– is higher. Comparing Mg2+ with Na+, the changing concentration hardly affects the evaporation rate because of similar vapor pressure. The higher concentration of Mg2+ leads to higher crystallization rate (2.1 min of 0.003 mol MgCl2, 2.2 min of 0.006 mol NaCl) due to the lower supersolubility. In the measurements of Ca2+, Mg2+, and Na+, the evaporation durations (around 4.45 min) and crystallization durations (2–2.05 min) are almost the same because of the low concentration solutes. According to the SEM results, the crystallization rate order when adding different ions is Mg2+ > Ca2+ > Na+.

Solubility and Activity Coefficients of Three Triazine-Type Compounds in Various Low Ionic Strength Aqueous Solutions

“…Ionic interaction models can be used to calculate the properties of electrolyte components and better predict the solubilities of ionic mixtures. Pitzer and many other researchers − have used a single set of equations to describe the osmotic and activity coefficients of the components of single salts and mixtures with common ions. By using virial expansion expressions to account for the ionic strength, the dependence of the short-range forces in binary and ternary ion interactions can be modeled by Pitzer’s model or the extended Debye–Hückel method.…”

Current Status of Zero Liquid Discharge Technology for Desulfurization Wastewater

“…It is to be noted that, in Ca 2+ , Mg 2+ , and Na + measurements, evaporation time and crystallization time were almost the same due to low solute concentration. When different ions were added, the crystallization rate was in the order of Mg 2+ > Ca 2+ > Na + [27]. In general, the traditional evaporation process has a high investment and energy consumption, and the contact efficiency between flue gas and liquid droplets is low, which cannot control costs.…”

Review of Migration, Transformation, and Control of Volatile Components during Desulfurization Wastewater Evaporation: Advances and Perspectives

“…Recently, several studies have been conducted on the evaporation process of desulfurization wastewater in recent years. − However, a systematic and comprehensive review of the topic is still lacking. This paper reviews the emission characteristics of chlorine, trace elements, and ammonia nitrogen during the evaporation process, discusses the problems and related research progress, and analyzes the control technologies with potential application values, all of which will provide valuable guidance for the further development and application of hot flue gas evaporation technology.…”