Concentration of desulfurization wastewater using low-temperature flue gas and associated corrosion risk

The low-temperature flue gas concentration is an effective pretreatment strategy to realize the zero discharge of desulfurization wastewater. However, the water quality changes during concentration and potential risks are not transparent. In this work, the concentration process is conducted on a lab-scale platform. The results show that the ion concentrations of wastewater does not increase linearly straightforwardly during the experiment, mainly due to the complex interaction between ions. Besides, the average size of precipitated products increases from 8.73 to 23.19 μm, which could be ascribed to the aggregation effect. The microscopic and spectroscopic characterization analysis further confirms this effect. In addition, the potential risk of corrosion is investigated. The decreased pH and the increasing corrosive ions concentration intensified the pitting effect on metals. The concentrated desulfurization wastewater exhibited a strong pitting effect on 20# carbon steel (corrosion rate of 1.2113 mm·a^-1.), while 316 stainless steel shows excellent corrosion resistance (corrosion rate of 0.0994 mm·a^-1.). This work provides a reference for the low-temperature flue gas concentration technology and would serve as an essential guideline for practical engineering.