改性赤泥基吸附剂对汞/酸性气体的协同脱除及稳定机理研究

Coal utilization has been considered as the largest anthropogenic source of mercury emissions. Mercury emission standard from industrial boilers has been released by many countries and regions. In recently years, the emission and control of mercury has drawn great attention worldwide and it is urgent to control mercury and various acid gases emission from flue gas. Simultaneous removal and immobilization of mercury and acid gas on non-carbon sorbent with sorbents using existing particulate matter control devices are regarded as an important and competitive method. The aim of the proposal is to investigate the removal of mercury and acid gas in flue gas during coal utilization. A new mineral, dispersed sorbent was involved which was derived from alumina production process using Bayer method. In our earlier study, the activated sorbent has been found that mercury capture was dominated by temperature and capture on sorbents over long scales. In this proposal, typical mineral samples will be collected. Complex mineral sorbent will be synthesized according to the industrial samples. Modified sorbent will be prepared by adding promoters to the former series raw or synthesized sorbents. The systematic experiments and theoretical studies will be conducted to analyze the effect of the sorbent components on the sorption of mercury and some other pollutants at different temperatures. The adsorption mechanism of mercury on the mineral surface will be investigated to further understand impacts of flue gas on mercury sorption process. The interaction mechanism between mercury - sorbent – acid gases will be developed and heterogeneous sorption kinetic model will be established. Mercury stability in subsequent fly ash recycling and red mud storage processes will also be evaluated. The ultimate goal is to provide a reliable theoretical basis to the removal of elemental mercury via multi-mineral sorbent in gas phase during low rank coal utilization that contributing to the development of integrated solid waste pollution control and resource utilization.

煤炭利用过程中释放的汞已成为最大的人为汞排放源。目前，对工业锅炉的汞排放限制日益严格，利用现有污染物控制设备实现汞及多种污染物的联合脱除是重要的研究和发展方向。前期研究结果表明，拜耳法氧化铝生产过程中产生的赤泥，经酸活化处理后得到的吸附剂对烟气中的气态汞和酸性气体有一定的吸附能力，但有关吸附剂组成在活化过程中的变化、单质汞和酸性气体在固体表面的吸附机理及稳定性等有待深入研究。本项目选取赤泥或模拟其组成制备用于汞和酸性气体脱除的吸附剂；通过实验并结合理论分析，研究吸附剂制备过程的组成结构变化对气态汞吸附性能的影响，获得性能优异的吸附剂；揭示汞—吸附剂—酸性气体之间的多相、多组分反应竞争/协同机制。通过研究吸附剂上汞/酸性气体的吸附/脱附特性，评估赤泥基吸附剂在安全处置过程中汞的稳定性。项目研究可为低阶燃煤烟气中污染物的一体化控制和固体废弃资源化利用提供科学依据。

煤炭利用过程中释放的汞已成为最大的人为汞排放源。目前，世界各国对工业的汞排放限制日益严格，利用现有污染物控制设备实现汞及多种污染物的联合脱除是重要的研究和发展方向。本项目基于燃煤烟气和天然气中的汞，提出以拜耳法氧化铝生产过程中产生的赤泥、廉价易得的二氧化钛和飞灰磁珠为吸附剂材料，将其改性应用在汞和酸性气体等多种污染物的联合脱除。研究了赤泥基、钛基和改性磁珠的热失重特性，得到了吸附剂的最佳焙烧温度；开展了针对不同气氛下吸附剂脱汞性能的研究，探讨了反应温度、金属种类及掺杂比例、光照强度对吸附剂性能的影响，确定了吸附剂的最佳反应条件。在最佳的反应条件下Cu/Ce改性的赤泥将反应温度区间拓宽到了150~300 ℃，且脱汞效率高于95% ；模拟赤泥主要成分的复合金属氧化物FAS在反应温度为350 °C时3 h平均脱汞率达到94.8%。反应后汞以HgO为主；所制备的钛基吸附剂12Mn-Ti-450的最佳脱汞效率98.46%，Fe改性后平均脱汞效率高达99.27%，且使样品的抗SO2性能显著提升；飞灰磁珠中的Cu:Fe为1:2 、Cu量为6 wt%时，吸附剂的脱汞效率高达97%。开展了酸性气体(HCl、NO、SO2、CO2和H2S)和O2对吸附剂性能的影响，发现，HCl、NO、O2可提高吸附剂的脱汞性能，H2S先促进后抑制，而CO2对吸附剂的影响表现为轻微的抑制或无影响。采用Hg-TPD、XPS及固定床反应器研究吸附剂反应前后表面的物质形态，探讨了汞脱除过程中吸附剂表面的反应机制。项目研究可为低阶燃煤烟气中污染物的一体化控制和固体废弃资源化利用以及低温下还原性气体中汞的脱除提供科学依据。

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