脱硫废水热烟气蒸发过程中挥发性组分迁移转化特性研究进展

Progress on migration and transformation characteristics of volatile components in hot flue gas evaporation of desulfurization wastewater

脱硫废水中存在挥发性重金属、氨氮、挥发性有机物(VOCs)、氯等挥发性组分。在采用热烟气蒸发时,部分挥发性组分会以气态形式再释放进而导致有在脱硫废水中循环富集的潜在风险。本文基于脱硫废水中挥发性组分来源、赋存形态的分析,探讨了热烟气蒸发过程中挥发性组分的迁移转化行为。挥发性污染组分迁移转化是一个非均相物理化学过程。废水固液相中的挥发性组分可通过纯物理作用或与其他组分发生反应以气态或颗粒态形式析出进入烟气,并进一步与烟气组分发生热分解转化、吸附凝结等作用。当前研究仅认为少量氯会以HCl的形式析出,重金属普遍认为均以颗粒态形式析出,有机物、氨氮则未作关注。迄今还只局限于宏观现象的考察,相关的定量研究十分缺乏。文中指出,在当前不经或只经简单预处理的热烟气蒸发技术逐渐成为电厂脱硫废水零排放主流路线的背景下,脱硫废水蒸发过程中挥发性组分的迁移转化规律的研究显得尤为重要。

There are volatile heavy metals, ammonia nitrogen, VOCs, chlorine and other volatile components in desulfurization wastewater. In the application of hot flue gas evaporation, volatile components will be re-released in the gaseous form, leading to the potential risk of cyclic enrichment in desulfurization wastewater. Based on the analysis of the sources and forms of volatile components in desulfurization wastewater, the migration and transformation of volatile components in hot flue gas evaporation are discussed. The migration and transformation of volatile pollutants is a heterogeneous physicochemical process. The volatile components in the solid or liquid phase of waste water can be separated into flue gas in gaseous or granular form through pure physical action or reaction with other components. Then further pyrolysis conversion, adsorption and condensation with flue gas components will occur. Current researches have shown that only a small amount of chlorine can be precipitated in the form of HCl, while heavy metals are commonly thought to be precipitated in the form of particles.However, organic matters and ammonia nitrogen are not paid attention to. So far, it has only been limited to the investigation of macroscopic phenomena, and the relevant quantitative research is scarce. Under the background that the hot flue gas evaporation technology without or only with simple pretreatment has gradually become the mainstream route of zero discharge of desulfurization wastewater from power plants,the study on the migration and transformation of volatile components in the process of desulfurization wastewater evaporation is particularly important.