论文总字数：22487字

摘 要

“温室效应”已经成为全世界急需解决的大气污染问题。CO₂是对“温室效应”影响最大的温室气体，燃煤电站是CO₂排放的最大来源。研究燃煤电厂CO₂减排技术有重要的意义。在目前降低CO₂排放的技术中，富氧燃烧被认为是最具应用前景和经济优势的减排技术，体现在NO_x排放量大大减少、极易捕获CO₂和锅炉工程造价降低等优势。但是在对富氧燃烧产生的烟气进行净化、压缩等工序时，烟气中的汞会与CO₂压缩存储设备中的铝制金属发生汞齐反应，造成安全问题。因此，富氧燃烧技术中，汞的脱除十分必要。

本课题选取一种商业原始活性炭，使用比表面积及孔隙度分析仪和傅里叶红外光谱仪（FTIR）对该活性炭的微观物理结构和表面化学官能团的种类及分布进行测定。在小型固定床实验台上，考察模拟富氧烟气中O₂、CO₂、NO、SO₂、HCl各组分对活性炭吸附元素汞的影响机理，重点讨论酸性气氛存在的条件下，高H₂O含量对活性炭吸附Hg⁰的影响规律。

活性炭表征结果表明，该活性炭的比表面积较大，属于中孔活性炭。傅里叶红外光谱图（FTIR）的结果表明，该活性炭的表面含氧官能团主要有羧基和内酯基。模拟富氧燃烧烟气中活性炭固定床吸附实验表明，纯CO₂气氛不会影响活性炭对Hg⁰的吸附，原因可能是CO₂占据了活性炭表面的微孔活性位。O₂能够明显地促进活性炭对Hg⁰的脱除。SO₂因为占据了活性炭的细孔及活性位，从而抑制活性炭对Hg⁰的脱除。而在活性炭表面的催化作用下，NO与HCl也分别会与O₂生成NO₂与Cl₂，对汞有较高的氧化性，从而极大地促进活性炭对汞的吸附脱除。

在固定床汞吸附实验台上进行的模拟富氧燃烧烟气中H₂O含量对活性炭对Hg⁰吸附的实验表明：高浓度的H₂O对汞脱除具有明显的抑制作用；在含SO₂气氛下，加入H₂O对活性炭吸附汞有促进作用，但促进作用极为有限；在含NO气氛下，较低浓度的H₂O会抑制活性炭吸附Hg⁰；在含HCl气氛下，H₂O抑制活性炭吸附汞，且随着H₂O含量的增加，其抑制能力先增强后减弱。

关键词：富氧燃烧；酸性气体；H₂O；活性炭；汞吸附

ABSTRACT

The "greenhouse effect" has already been the world's urgent need to address air pollution problems. CO₂ has the greatest impact on the "greenhouse effect". Coal-fired power plants are one of the largest sources of CO₂ emissions. Among the many measures to reduce CO₂ emissions, oxygen-enriched combustion technology is currently considered to have broad application prospects and economic advantages of emission reduction technology, which reflected in the low NO_x emissions, low cost and large-scale CO₂ emission reduction even near-zero emissions advantage. However, when the flue gas produced by oxygen-enriched combustion is purified and compressed, the mercury in the flue gas reacts with the aluminum metal in the CO₂ compressed storage device, resulting in safety problems. Therefore, in order to successfully applicate the oxygen-rich combustion technology, mercury removal is necessary.

In this paper, a kind of raw activated carbon was selected. The microstructure and morphology was determined by N₂ adsorption/desorption and the surface chemical functional groups was determined by Fourier transform infrared spectroscopy (FTIR). The effects of O₂, CO₂, NO, SO₂, HCl and the composite components on the adsorption of elemental mercury in activated carbon were investigated on a small fixed bed reactor. The effects of the H₂O content on adsorption of Hg⁰ by activated carbon in the presence of acid atmosphere were investigated.

The characterization of the physical and chemical properties of activated carbon shows that the specific surface area of the activated carbon is large and belongs to mesoporous adsorption. Fourier transform infrared spectroscopy (FTIR) result shows that the oxygen functional groups in the surface of the activated carbon are mainly carboxyl and lactone. Activated carbon adsorption experiment showed that the pure CO₂ atmosphere did not affect the adsorption of Hg⁰ by activated carbon. The reason for the analysis may be that the CO₂ occupies the microporous structure of the activated carbon. O₂ can significantly promote the removal of Hg⁰ by activated carbon. In the simulated oxygen-enriched combustion flue gas, SO₂ can inhibit the removal of Hg⁰ by activated carbon because it occupies the pores and active sites of activated carbon. With the catalytic effects of activated surface, NO and HCl can react with O₂ to produce NO₂ and Cl₂,respectively, which can strongly enhance the retention of mercury on the activated surface. The mixture of SO₂, NO, HCl also played a great promoting role in mercury adsorption by activated carbon.

The experimental results of H₂O content on the adsorption of Hg⁰ by activated carbon in simulated oxygen-enriched combustion flue gas showed that high concentration of H₂O had an inhibitory effect on mercury removal. Low concentration of H₂O can promote the adsorption of mercury by activated carbon. In the presence of SO₂, the addition of H₂Opromoted the adsorption of mercury by activated carbon, but in the case of high concentration of SO₂, the promotion effect was very limited. When NO was present, the lower H₂O concentration inhibited the adsorption of Hg⁰. H₂O inhibited the adsorption of mercury on the surface of activated carbon in the HCl-containing atmosphere, and mercury removal rates decreased with the increase of the H₂O content.

Keyword: oxy-fuel combustion ; H₂O; activated carbon; mercury retention

目 录

摘 要 I

ABSTRACT II

第一章 绪论 2

1.1 课题研究背景 2

1.1.1 CO₂排放及控制技术 2

1.1.2 富氧燃烧技术 2

1.1.3 汞排放及其危害 3

1.2 燃煤电厂汞控制技术 3

1.2.1 燃烧前脱汞 3

1.2.2 燃烧中脱汞 4

1.2.3 燃烧后脱汞 4

1.3 活性炭脱汞吸附剂研究现状 5

1.4 课题研究内容 5

1.5 本章小结 6

第二章 实验装置与方法 7

2.1 固定床汞吸附实验装置 7

2.2 实验仪器 8

2.2.1 VM3000测汞仪 8

2.2.2 比表面积及孔隙度分析仪 8

2.2.3 气相色谱—傅立叶变换红外光谱联用仪 9

2.3 评价指标 9

2.4 本章小结 10

第三章 模拟富氧燃烧烟气中酸性气体影响活性炭Hg⁰吸附的实验研究 11

3.1 活性炭理化特性表征与分析 11

3.2 CO₂对活性炭吸附Hg⁰的影响 12

3.3 O₂对活性炭吸附汞的影响 13

3.4 SO₂对活性炭吸附汞的影响 14

3.5 NO对活性炭吸附汞的影响 14

3.6 HCl对活性炭吸附汞的影响 15

3.7 本章小结 16

第四章 模拟富氧燃烧烟气中H₂O含量影响活性炭Hg⁰吸附的实验研究 17

4.1 不同H₂O含量对活性炭吸附Hg⁰的影响 17

4.2 SO₂氛围下H₂O含量对活性炭吸附Hg⁰的影响 18

4.3 NO氛围下H₂O含量对活性炭吸附Hg⁰的影响 19

4.4 HCl氛围下H₂O含量对活性炭吸附Hg⁰的影响 20

4.5 本章小结 21

第五章 总结与展望 22

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