Salt deposition problems in supercritical water oxidation

• This article presents a detailed analysis of salt deposition concerning its cause, harm, and control means in SCWO.
• The current research methods for salt deposition in recent years are objectively summarized.
• The mechanisms of salt deposition are preliminarily analyzed and summarized.
• Some reactor designs and control methods are proposed to avoid salt deposition for a given wastewater in SCWO.

Supercritical water oxidation (SCWO) is a promising technology that has been utilized to deal with refractory wastewater and sewage sludge at laboratory or commercial scale. However, its commercial application is postponed by corrosion and salt deposition problems in harsh SCWO environment. This work systematically and objectively reviews its current research status concerning salt deposition mainly including research methods, solubilities, deposition and separation performances, etc. and the mechanisms of salt deposition are preliminarily analyzed and summarized. Besides, several operation techniques and reactor configuration designs of either laboratory scale or commercial level used in SCWO processes are introduced to avoid reactor plugging induced by salt deposition. Finally, some subsequently alternative research ideas are proposed to reveal salt deposition mechanisms. A wise SCWO system is supposed to possess an appropriate reactor configuration and more than one control techniques to work together for a given wastewater.