论文总字数：27353字

摘 要

燃煤电厂现有的污染物控制装置对燃煤烟气中不同形态汞（单质汞Hg⁰、氧化态汞Hg² （HgCl₂为主）和颗粒汞Hg^P）拥有不同的脱除特性，因而实现分形态检测燃煤烟气汞浓度有助于汞排放控制技术的发展。受限于现有的汞分析技术仅能检测Hg⁰，开发一款能高效吸附HgCl₂但对Hg⁰完全穿透的汞形态选择性吸附剂，并将其应用于Hg-CEMS装置，有助于最终实现燃煤烟气各形态汞浓度的连续在线监测。

为此，本文以CaO为活性组分，介孔材料SiO₂、TiO₂和γ-Al₂O₃为载体，利用化学浸渍法制备担载型钙基吸附剂CaO/ SiO₂、CaO/ TiO₂、CaO/γ-Al₂O₃。在汞吸附固定床实验装置上分别探究了上述三种钙基吸附剂在N₂和SO₂气氛下对Hg⁰/HgCl₂的吸附性能，结果表明，三种钙基吸附剂对Hg⁰几乎不吸附，但对HgCl₂有较高的吸附效率，且三种吸附剂中，CaO/γ-Al₂O₃的HgCl₂选择性吸附和抗SO₂抑制性能最佳。结合N₂/吸附脱附、电镜扫描（SEM）和碱性位表征结果发现，CaO/γ-Al₂O₃具有最佳的孔隙结构和丰富的强碱性位，这导致其能高效吸附酸性HgCl₂分子。SO₂易与CaO发生反应，生成易堵塞孔道的CaSO₃和CaSO₄，隔绝了Hg⁰/HgCl₂与吸附剂内表面上吸附位的接触，同时，同为酸性的SO₂和HgCl₂分子对吸附剂表面的碱性位存在竞争吸附，这导致了SO₂对钙基吸附剂的HgCl₂选择吸附性能存在抑制作用。

为满足实际工业应用，探究了初始汞浓度、吸附温度、空速、吸附剂粒径等操作参数对CaO/γ-Al₂O₃吸附HgCl₂的影响规律，结果表明，随初始汞浓度或吸附温度的升高，CaO/γ-Al₂O₃对HgCl₂吸附率呈现先增加后减小的趋势，且最佳初始汞浓度和最佳吸附温度分别为38g/m^-3和160℃；随空速的减小，HgCl₂吸附效率增大后趋于不变，但在空速为40000h^-1时，既能保证CaO/γ-Al₂O₃高效的HgCl₂吸附性能，又能减少吸附剂的用量；吸附剂粒径由12目减小至100目时，CaO/γ-Al₂O₃对HgCl₂的吸附效率先上升后减少，且在粒径为24-40目时，吸附效率最高。

关键词：钙基吸附剂；Hg⁰/HgCl₂；选择性吸附；SO₂；操作参数

Abstract

Coal-fired power plant's existing pollutant control device for different forms of mercury in coal-fired flue gas (elemental mercury Hg⁰, oxidized mercury Hg² (mainly HgCl₂) and particulate mercury Hg^P) has different removal characteristics, so accurate measurement of different forms of mercury is conducive to promoting the development of mercury control technology. It is constrained by the fact that existing mercury analysis techniques can only detect Hg⁰. Thus developing a mercury-selective sorbent capable of efficiently adsorbing HgCl₂ but completely penetrating Hg⁰ and applying it to Hg-CEMS device will help to achieve continuous on-line monitoring of the mercury concentrations in various forms of coal-fired flue gas.

Therefore, this research uses CaO as the active component and regards mesoporous materials SiO₂, TiO₂ and γ-Al₂O₃ as carriers to prepare the supported Ca-based adsorbent CaO/SiO₂, CaO/TiO₂ and CaO/γ-Al₂O₃ by chemical impregnation. The adsorption performance of Hg⁰/HgCl₂ on the above three kinds of calcium-based sorbents in N₂ and SO₂ atmospheres is investigated on a mercury adsorption fixed-bed experimental device. These three adsorbents hardly adsorb Hg⁰, but have a high adsorption efficiency for HgCl₂. Among three adsorbents, it is the CaO/γ-Al₂O₃ that has the best properties of HgCl₂ adsorption and anti-SO ₂ inhibition. Combined with N₂/adsorptionamp;desorption, scanning electron microscopy (SEM) and basic position characterization, it is found that CaO/γ-Al₂O₃ has the best pore structure and abundant strong alkali sites. It causes CaO/γ-Al₂O₃ to efficiently adsorb acidic HgCl₂ molecules. SO₂ easily reacts with CaO to form CaSO₃ and CaSO₄ which tend to block the pores and isolate the contact of Hg⁰/HgCl₂ with the adsorption sites on the adsorbent's internal surface. The acidic SO₂ and HgCl₂ molecules have competitive adsorption on the basic sites of the adsorbent, which leads to the inhibition of SO₂ on the selective adsorption of the calcium-based adsorbent on HgCl₂.

In order to meet practical industrial applications, the influence of initial mercury concentration, adsorption temperature, airspeed, particle size and other operating parameters on the adsorption of CaO/γ-Al₂O₃ on HgCl₂ is investigated. With the increase of initial mercury concentration or adsorption temperature, the adsorption rate of CaO/γ-Al₂O₃ to HgCl₂ first increases and then decreases, and the best initial mercury concentration and adsorption temperature is 38g/m^-3 and 160°C respectively; as the airspeed decreases, the adsorption efficiency of HgCl₂ tends to increase and then remain unchanged. When the airspeed condition falls to 40000h^-1, it can not only ensure good divalent mercury selective adsorption performance, but also ensure high economic performance; when the particle size of the adsorbent reduces, the adsorption efficiency of CaO/γ-Al₂O₃ to HgCl₂ increases first and then decreases, and the adsorption efficiency is highest when the particle size was 24-40 mesh.

Key words: calcium-based adsorbent; Hg⁰/HgCl₂; selective adsorption; SO₂; operating parameter

目录

摘要 I

Abstract II

第一章 绪论 1

1.1课题研究背景 1

1.1.1 燃煤烟气汞排放及危害 1

1.1.2 燃煤烟气汞的迁移转化规律 1

1.2 燃煤烟气汞浓度检测方法 2

1.2.1 高锰酸钾溶液吸收法 2

1.2.2 吸附管离线采样法 3

1.2.3 安大略法 3

1.2.4 汞在线连续监测法 4

1.3汞形态选择性吸附剂 5

1.3.1 活性组分 5

1.3.2 载体材料 6

1.4本文主要研究内容 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 固定床汞吸附实验装置 8

2.1.2 汞形态分析仪 8

2.2吸附剂的表征仪器 9

2.2.1 比表面积及孔隙度分析仪 9

2.2.2 扫描电镜（SEM） 10

2.2.3 CO₂程序升温脱附仪(CO₂-TPD) 10

2.3吸附剂性能评价指标 10

2.4本章小结 11

第三章 担载型钙基吸附剂汞吸附实验研究 12

3.1 担载型钙基吸附剂的制备 12

3.2 担载型钙基吸附剂的表征 12

3.3 担载型钙基吸附剂Hg⁰吸附性能 13

3.4 担载型钙基吸附剂HgCl₂吸附性能 14

3.5 本章小结 15

第四章 操作参数对钙基吸附剂HgCl₂吸附性能影响实验研究 16

4.1 初始汞浓度对钙基吸附剂HgCl₂吸附性能的影响 16

4.2 吸附温度对钙基吸附剂HgCl₂吸附性能的影响 16

4.3 空速对钙基吸附剂HgCl₂吸附性能的影响 17

4.4 粒径大小对钙基吸附剂HgCl₂吸附性能的影响 18

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