Ce-MnTiO2吸附剂脱汞及热再生特性实验研究

论文总字数：30645字

摘 要

重金属汞作为燃煤第四大污染物，对生态环境和人类健康的危害日益彰显。燃煤烟气中的汞主要以三种形态存在：元素汞（Hg⁰）、氧化汞（Hg² ）和颗粒汞（Hg^p）。Hg² 可通过湿法脱硫装置去除，而Hg^p可通过除尘装置去除，Hg⁰因为难溶于水，易挥发，难以被现有的空气污染物控制装置脱除，成为汞污染治理的重点和难点。现有的烟道活性炭喷射脱汞技术，具有高效性但吸附剂无法回收，运行成本高，难以广泛推广利用。因此，研究高效可再生的脱汞吸附剂显得尤为重要。

本文选择以Ce改性的锰氧化物作为活性成分，TiO₂为担载材料，使用浸渍法制备Ce-Mn/TiO₂吸附剂。在固定床汞吸附实验台上，探究了O₂，HCl，SO₂，NO对吸附剂脱汞效率的影响。结果表明，O₂、HCl和NO能提高脱汞效率，SO₂会降低脱汞效率。通过对脱汞试验后的Ce-Mn/TiO₂吸附剂进行Hg-TPD实验，确定了Ce-Mn/TiO₂吸附剂热再生的可行性。进一步讨论了再生温度和再生气氛对吸附剂再生性能的影响。实验结果表明，最佳再生温度为400 °C，再生气氛为N₂ 50%O₂。考虑到实用性，考察了吸附剂的热再生稳定性。四次吸附-再生循环脱汞结果表明，吸附剂再生稳定性良好。

为探究Ce-Mn/TiO₂吸附剂的失活及热再生机理，对脱汞及热再生前后的吸附剂进行XPS表征分析，结果表明，在Mn⁴ 及Ce⁴ 的作用下，Hg⁰被氧化成Hg² ，Hg² 与氧反应生成HgO并吸附在吸附剂表面，占据活性位点，致使脱汞效率下降。在热再生高温作用下，HgO分解，暴露活性位点，同时在氧气的作用下，Mn⁴ 及Ce⁴ 的含量得到了一定程度的恢复，继而实现了吸附剂的再生。

关键词：Ce-Mn/TiO₂；脱汞；吸附剂；Ce改性；锰氧化物；热再生

ABSTRACT

As the fourth largest pollutant in coal combustion, heavy metal mercury is increasingly harmful to ecological environment and human health. In coal-fired flue gas, there are three forms of mercury: elemental mercury (Hg⁰), oxidized mercury (Hg² ) and particulate mercury (Hg^P) . Hg² can be removed by the a wet flue gas desulfurization device, and Hg^P can be removed by a dust removal device. Because Hg⁰ is insoluble in water and volatile, it is difficult to remove it by the existing air pollutant control devices, which has become the focus and difficulty of mercury pollution control. The existing flue gas activated carbon injection mercury removal technology has high mercury-removal efficiency, but sorbents can not be recovered and the operation cost is high, which limit its widespread use. Therefore, It is particularly important to develop highly efficient and renewable mercury removal sorbents..

In this work, Ce-Mn/TiO₂ sorbents were prepared by impregnation method, which selected Ce-modified manganese oxide as active component and TiO₂ as the supporting material, respectively. The effects of O₂，HCl，SO₂，and NO on the mercury removal efficiency by the sorbents were investigated on a fixed bed mercury adsorption test bench. The results show that O₂, HCl and NO can improve the mercury removal efficiency, while SO₂ can reduce the mercury removal efficiency. The feasibility of thermal regeneration of Ce-Mn/TiO₂ sorbent was determined by Hg-TPD experiment on Ce-Mn/TiO₂ sorbent after mercury removal test. In further, the effects of regeneration temperature and regeneration atmosphere on the regeneration performance of the sorbent were discussed. The experimental results show that the optimum regeneration temperature is 400 °C and the regeneration atmosphere is N₂ 50%O₂. Considering the practicality, the thermal regeneration stability of sorbents was investigated. The results of four adsorption-regeneration cycle mercury removal show that the regeneration stability of the sorbent was good.

In order to investigate the mechanism of deactivation and thermal regeneration of CeMn/TiO₂ sorbent, the XPS characterization and analysis of the sorbent before and after mercury removal and thermal regeneration were carried out. The results show that under the action of Mn⁴ and Ce⁴ , Hg⁰ is oxidized to Hg² , then Hg² reacts with oxygen to form HgO and adsorbs on the surface of the sorbent, which occupies the active site. It leads to a decrease in mercury removal efficiency. Under the action of high temperature in heat regeneration, HgO decomposes and exposes the active sites. At the same time, under the action of oxygen, the content of Mn⁴ and Ce⁴ is restored to a certain extent. Then, the regeneration of the sorbent is realized.

Key words：Ce-Mn/TiO₂; mercury removal; sorbents; Ce modification; manganese oxide; thermal regeneration

目 录

摘要 Ⅰ

ABSTRACT Ⅱ

第一章 绪论 3

1.1课题研究背景 3

1.1.1汞的性质及危害 3

1.1.2燃煤汞的迁移 3

1.2燃煤电厂汞污染控制技术 4

1.2.1燃烧前脱汞 4

1.2.2燃烧中脱汞 4

1.2.3燃烧后脱汞 4

1.3脱汞吸附剂的再生 5

1.3.1汞吸附剂再生方法 5

1.3.2可再生汞吸附剂 5

1.4本课题主要研究内容 6

1.5本章小结 7

第二章 实验装置及方法 8

2.1实验装置 8

2.1.1固定床汞吸附实验台 8

2.1.2程序升温脱附实验台 9

2.2主要测量仪器 9

2.2.1VM 3000测汞仪 9

2.2.2比表面积及孔隙度分析仪 10

2.3本章小结 10

第三章 Ce-Mn/TiO₂吸附剂脱汞特性研究 11

3.1 Ce-Mn/TiO₂吸附剂的制备 11

3.2 Ce-Mn/TiO₂吸附剂的表征分析 11

3.3 O₂对Ce-Mn/TiO₂吸附剂脱汞效率的影响 11

3.4 HCl对Ce-Mn/TiO₂吸附剂脱汞效率的影响 12

3.5 SO₂对Ce-Mn/TiO₂吸附剂脱汞效率的影响 13

3.6 NO对Ce-Mn/TiO₂吸附剂脱汞效率的影响 14

3.7本章小结 15

第四章 Ce-Mn/TiO₂吸附剂热再生特性研究 16

4.1程序升温脱附(Hg-TPD)研究 16

4.2再生温度对Ce-Mn/TiO₂吸附剂再生的影响 16

4.3气氛对Ce-Mn/TiO₂吸附剂再生的影响 17

4.4 Ce-Mn/TiO₂吸附剂热再生稳定性研究 18

4.5 Ce-Mn/TiO₂吸附剂热再生机理分析 18

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