磁诱导燃煤电厂飞灰与烟气中零价汞及其脱除机理研究

Previous experimental results have manifested that the fly ash collected from coal-fired power plant exhibits a considerable improvement in the mercury removal capacity when the fly ash is imposed by the external magnetic field (EMF). But it is still unclear to us how the magnetism influences the fly ash and elemental mercury. This severely inhibits the utilization and application of magnetic technology on the mercury removal by the fly ash. The purpose of this project is to perform the fundamental works to understand the mechanism of the mercury removal of fly ash under the magnetic-induced technique. A combining strategy of experimental measurement, theoretical analysis, and numerical computation is designed to study the EMF on mercury removal. The associated experiments will be set up to observe the nature between EMF and organic chemical function, the adhesive between radical and mercury, and the characteristics between energy-level-splitting mercury and its capture. Furthermore, the magnetochemistry equations will be presented to model the mercury capture by fly ash under magnetic-induced technique. Finally, the quantum chemistry is employed to deduce the evolution tendency of electronic structure of elemental mercury and radical, and to understand the influence on mercury adsorption under magnetic-induced technique. As compared with the experimental results, this project will present the inner correlation between magnetic environment and elemental mercury. It can be seen that the magnetic field applied in this project activates the change in the electronic structures of fly ash and elemental mercury to enhance the mercury capture of fly ash. The results can provide the effective approach to analysis the mechanism of mercury removal by fly ash, and also facilitate forming theoretical and technical foundation for employing magnetic technique to control mercury pollution.

试验表明，外加磁场可有效提高燃煤电厂飞灰对烟气中零价汞的去除率，然而，磁场与飞灰和零价汞的作用机理仍不清楚，严重制约磁技术在飞灰汞污染治理中的发展和应用。本项目旨在对磁诱导燃煤电厂飞灰去除烟气中零价汞的特征和机制进行基础研究。拟采用实验研究、理论分析和数值仿真相结合，对施加外界磁场的飞灰去除烟气中零价汞的影响进行分析。利用飞灰去除零价汞的实验平台，获取外界磁场与飞灰中有机官能团，自由基与汞吸附，汞的能级分裂与汞去除率的作用规律；建立磁诱导飞灰去除烟气中零价汞的磁化学方程；利用量子化学计算方法解析磁诱导条件下自由基与零价汞电子结构的演化过程，掌握其与汞脱除的作用机理，结合实验结果，揭示飞灰去除零价汞与磁诱导的内在关联。本项目通过磁诱导飞灰与零价汞电子结构变化增强飞灰对汞的脱除能力，研究成果为提高飞灰对烟气中零价汞去除率提供新的工艺和技术，同时也为引入磁技术应用汞污染治理奠定理论和技术基础。

汞是具有高毒性的重金属之一，燃煤汞排放是造成汞环境污染的主要人为来源。研究燃煤电厂飞灰去除烟气中零价汞，对控制汞污染、节约生成成本，减少资源消耗和提高资源利用率具有十分重要价值。实验结果表明，磁诱导可以有效的提高飞灰去除零价汞的效率，为改善飞灰汞吸附和去除特性提供了有效手段。因此本项目对燃煤电厂飞灰在磁诱导作用下去除烟气中零价汞的特征和机理进行了基础性研究。采用实验研究、理论分析和量子化学计算相结合的方式，对磁诱导下燃煤电厂飞灰去除烟气中零价汞的影响规律进行分析。利用飞灰去除烟气中零价汞的实验平台，获取外界磁场与飞灰中有机官能团，自由基与汞吸附，汞的能级分裂与汞去除率的作用规律。结果表明：当飞灰里的未燃尽炭受到磁场的作用，有机官能团得到激发，产生自由基，从而使得零价汞在自由基的作用下容易氧化成二价汞。在磁场作用下，汞的能级发生分裂，能带间隙大幅减小，电子跃迁变得相对容易，化学反应速度加快，吸附性能得到有效提升；建立磁诱导燃煤电厂飞灰去除烟气中零价汞的磁化学方程。结果表明无外加磁场和有外加磁场的汞吸附数据分别可以很好地符合MPnO模型和准一级动力学模型的拟合数据；利用量子化学计算方法解析磁诱导条件下自由基与零价汞的电子轨道演化过程，掌握其与汞脱除的作用机理。本项目在碳基表面构建了C-H和C-O官能团，研究官能团对碳表面结构的影响，通过量子化学计算，结果表明汞吸附性能不仅与被吸附位置附近的碳原子性能有关，而且与碳表面吸附的官能基团的原子也有关系。汞吸附与官能基团的结构有较大关系，表明官能基团不仅改变了碳表面原子电子特性，也直接参与了汞吸附过程，表现出吸附过程中的复杂性。本项目揭示燃煤电厂飞灰去除零价汞与磁诱导的内在关联，为燃煤电厂飞灰去除烟气中零价汞的实际应用提供技术支持，为在燃煤电厂高效去除烟气中零价汞提供新的工艺方法。