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

Abstract

Desulfurization wastewater evaporation technology has, over time, been adopted by coal-fired power plants in recent years to achieve zero discharge of wastewater. However, the volatile components of chlorine, trace elements (Hg, As, and Se), and ammonia nitrogen in wastewater are released in gaseous form. It potentially leads to the risk of their cyclic enrichment in wastewater from desulfurization. This review summarizes volatile components' migration and transformation behavior during evaporation. As the evaporation process proceeds, Cl would be released as HCl. Due to the volatility of Hg, As, and Se, the evaporation process would be coupled with the migration and transformation of gaseous components such as Hg 0 , SeO 2 , and As 2 O 5 . The ammonia and ammonium present in the wastewater would release during evaporation, and its release rate depends greatly on the pH value of the wastewater. In addition, the released gaseous and particulate volatile components can further interact with the flue gas components, such as those from thermal decomposition and conversion, adsorption, and condensation on the solid particulate matter from wastewater evaporation. Moreover, several control strategies are proposed in this work to avoid the adverse effects of wastewater evaporation technology. The zero valent iron method offers suitable potential applications with high removal efficiency and the ability to remove multiple pollutants simultaneously. Developing new adsorbents, which may significantly reduce risks associated with the release of volatile components, should also be the focus of future research.