利用飞灰中的磁珠和富钙灰联合控制烟气中砷、汞的研究

Arsenic and mercury pollution is an important environmental problem that threatens human health and ecological safety. Coal-firing is the primary anthropogenic emission source of arsenic and mercury, so it is imminent to effectively control the emissions of arsenic and mercury. Based on the iron and calcium components in fly ash possessing obvious effects of arsenic removal and mercury oxidation, and using the iron and calcium components in fly ash to control the arsenic and mercury emission having the great advantages of low price, no adverse impacts on fly ash utilization, no corrosion, etc, this proposal tries to isolate the ferrospheres and limes from the fly ash, and mainly studies the arsenic removal effect by them. Through simulation experiments of arsenic removal system, structure characterization and theoretical analysis, this proposal also investigates the influences on the arsenic removal performance by the components of flue gas, flue gas temperature and crystalline structure transition, and tries to reveal the microscopic mechanism of arsenic removal by the ferrospheres and limes, furthermore studies the collaborative mercury oxidation performance and the interaction mechanism. Through this research, it is expected to achieve new knowledge and progress in the removal method and the removal mechanism of arsenic and improve the understanding of migration and transformation of arsenic removal process. It is also expected to provide theory and application guides for cheaply and cooperatively control the variety of heavy metals in flue gas by using the fly ash and its useful components from the power plants.

砷、汞污染是威胁人类健康和生态安全的重要环境问题，燃煤是砷、汞首要的人为排放源，有效控制燃煤砷、汞排放迫在眉睫。本项目基于飞灰中铁、钙组分具有明显的脱砷和汞氧化效果，且利用飞灰中自有铁、钙组分控制烟气中砷、汞排放具有廉价、不影响飞灰资源化利用、无腐蚀、无次生污染等优势，因此构思从电厂飞灰中分离富集出其中高铁含量的磁珠和高钙含量的富钙灰，重点研究其脱除重金属元素砷的特性，通过脱砷系统模拟实验、结构表征和理论分析，考察烟气组分、尾部烟气温度和晶态结构转变对脱砷性能的影响，揭示磁珠和富钙灰脱砷的微观机理，同时考察其对汞的协同氧化性能和作用机制。通过本研究，有望在重金属元素砷的脱除方法和脱除微观机理上取得新的认识和进展，提高对脱砷过程砷的迁移和转化规律的认识，同时为利用电厂自有飞灰及其所含有用组分廉价、高效、一体化脱除烟气中多种重金属技术提供参考。

烟气重金属污染控制是环境科学与工程领域的难点，本项目基于飞灰中铁、钙组分具有明显的脱砷和脱汞效果，且利用飞灰控制烟气中砷、汞排放具有价廉易得、不影响飞灰利用等优势，因此主要研究飞灰富集磁珠方法、飞灰及磁珠的脱砷性能及飞灰理化特性与砷吸附的相关关系，探索烟气组分、尾部烟气温度和晶态结构转变对磁珠脱砷性能的影响，研究磁珠脱砷的微观机理，同时考察其对汞的协同作用机制。研究结果表明，湿法磁选是从飞灰中富集高铁含量磁珠的有效方法，富集出的磁珠中，其Fe2O3含量可高达50%；磁珠吸附脱砷能力比相应的飞灰大大增强，实现了烟气中砷高达42.7%的脱除效率，比相应飞灰脱砷能力增强了1倍左右。飞灰自身含碳量、比表面积和无机组分等理化特性与砷吸附的相关关系随温度变化而不同。吸附温度是影响飞灰及磁珠吸附脱砷的重要因素，最佳的吸附温度为600℃。烟气杂质气体SO2对砷吸附具有抑制作用。飞灰及磁珠吸附脱砷能力的强弱主要由Fe活性组分决定，而与Ca、Si和Al组分相关性不大。磁珠脱除烟气中砷的同时，也能协同脱除烟气中的汞。这些研究结果为烟气重金属廉价、高效、一体化控制提供了理论基础和应用指导。