State Key Laboratory of Clean Energy Utilization, National Environmental Protection Coal-fired Air Pollution Control Engineering Technology Center, Zhejiang University, Hangzhou, 310027, China.
Environ Sci Pollut Res Int. 2019 Feb;26(5):4791-4800. doi: 10.1007/s11356-018-3816-y. Epub 2018 Dec 18.
Wastewater from a limestone-gypsum wet desulfurization system cannot be directly reused or discharged due to its high suspended matter content and complex water composition. Desulfurization wastewater evaporation in flue gas is an effective way to dispose wastewater. Multicomponent soluble chlorine salts exist in the desulfurization wastewater. During the evaporation, chlorine enters into the flue gas due to volatilization, which accelerates the enrichment rate of the Cl concentration in the desulfurization slurry and leads to an increase in wastewater production. This study explored the chlorine migration of various chlorine salt solutions and typical desulfurization wastewater at high temperature during the evaporation process of concentrated wastewater by a laboratory-scale tube furnace and a pilot-scale system. Results showed that when NaCl-evaporated substance was heated, the chlorine ion hardly volatilized. For the evaporated substances of CaCl and MgCl solutions, some of the crystal water was lost, and hydrolysis occurred to generate gaseous HCl. NHCl was easily sublimed, and the decomposition temperature was lowest. A pilot study on spray evaporation of desulfurization wastewater in flue gas showed that the particle size of the evaporated product increased and the main particle size was within 2.5-10 μm with increasing flue gas temperature. Increasing the mass ratio of gas to liquid significantly reduced the particle size of the atomized particles, thereby reducing the average particle size of the evaporated particles. The HCl concentration increased with increasing flue gas temperature. When the flue gas temperature was 350 °C, the concentration of HCl was 40 ppm, and the escape rate of chlorine in the desulfurization wastewater was approximately 30% using typical wastewater from a limestone-gypsum wet desulfurization system.
由于石灰石-石膏湿法脱硫系统废水悬浮物含量高、水质成分复杂，不能直接回用或排放。将脱硫废水进行烟道蒸发是处理废水的有效方法。脱硫废水中存在多种可溶性氯盐。在蒸发过程中，由于挥发，氯进入烟道气，导致脱硫浆液中 Cl 浓度的富集速度加快，废水产生量增加。本研究采用实验室管式炉和中试系统，探讨了浓缩废水蒸发过程中各种氯盐溶液和典型脱硫废水的氯迁移特性。结果表明，当 NaCl 蒸发物质受热时，氯离子几乎不挥发。对于 CaCl 和 MgCl 溶液的蒸发物质，部分结晶水丢失，并发生水解生成气态 HCl。NHCl 易升华，分解温度最低。烟道气脱硫废水喷雾蒸发中试研究表明，随着烟气温度的升高，蒸发产物的粒径增大，主要粒径在 2.5-10μm 之间。增加气液质量比显著减小了雾化颗粒的粒径，从而降低了蒸发颗粒的平均粒径。HCl 浓度随烟气温度的升高而增加。当烟气温度为 350℃时，HCl 浓度为 40ppm，采用典型的石灰石-石膏湿法脱硫系统废水，脱硫废水中的氯逸出率约为 30%。
