燃煤电厂脱硫浆液中汞迁移转化及添加剂对石膏中汞稳定性影响

苏银皎; 滕阳; 张锴; 李丽锋; 王鹏程; 李圳

doi:10.19906/j.cnki.JFCT.2021055

燃煤电厂脱硫浆液中汞迁移转化及添加剂对石膏中汞稳定性影响

doi: 10.19906/j.cnki.JFCT.2021055

苏银皎^1,,
滕阳¹,
张锴^1, ,,
李丽锋²,
王鹏程²,
李圳²

1.
华北电力大学热电生产过程污染物监测与控制北京市重点实验室，北京 102206
2.
山西河坡发电有限责任公司，山西阳泉 045011

基金项目: 国家重点研发计划（2020YFB0606201），国家自然科学基金委与山西煤基低碳联合基金重点项目（U1910215）和中央高校基本科研业务费（2019QN020，2019QN019）资助

详细信息

通讯作者:
E-mail: kzhang@ncepu.edu.cn

中图分类号: TQ53
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出版历程
- 收稿日期: 2021-03-24
- 修回日期: 2021-05-07
- 网络出版日期: 2021-06-01
- 刊出日期: 2021-07-15

Migration and transformation of mercury in WFGD slurry from a coal-fired power unit and the effect of additive on mercury stability in gypsum

1.
Beijing Key Laboratory of Emission Surveillance and Control for Thermal Power Generation, North China Electric Power University, Beijing 102206, China
2.
Shanxi Hepo Power Generation Company Limited, Yangquan 045011, China

Funds: The project was supported by the National Key R&D Program of China (2020YFB0606201), the National Natural Science Foundation of China (U1910215) and the Fundamental Research Funds for the Central Universities (2019QN020，2019QN019)

More Information

Corresponding author: E-mail: kzhang@ncepu.edu.cn

摘要

摘要: 以某300 MW超低排放燃煤机组现场脱硫浆液为研究对象，考察了浆液中汞迁移转化及添加剂对其影响行为，探讨了固相石膏中汞的热释放特性和环境风险。结果表明温度升高仅导致气相Hg⁰增加，而浆液pH升高会导致气相和固相中汞含量均有增加，Cl⁻或$ {\rm{SO}}^{2-}_{4} $浓度升高既可以抑制浆液中汞还原为Hg⁰也可以促进固相石膏中汞含量增加，而$ {\rm{SO}}^{2-}_{3} $浓度升高虽然有利于汞富集于固相但会引起Hg²⁺部分转化为Hg⁰。Na₂S、EDTA-2Na或DTCR-4添加剂与Hg²⁺反应分别生成HgS、Hg(EDTA)₂或[ −Hg-DTCR] −_n，使浆液中75%以上汞转移至固相石膏中，并抑制了Hg²⁺还原为Hg⁰，其中DTCR-4对汞的固化效果最好，但热稳定性依次为Gypsum + EDTA-2Na < Gypsum + DTCR-4 < Gypsum + Na₂S < Gypsum，主要原因是所生成Hg(EDTA)₂、[ −Hg-DTCR] −_n和HgS(black)的稳定性差异所致。进而采用TCLP、SPLP和MEP三种方法获得了样品中汞的化学稳定性为Gypsum < Gypsum + Na₂S < Gypsum + EDTA-2Na < Gypsum + DTCR-4，其原因是石膏中水溶态汞、酸溶态汞和可氧化态汞含量的差异所致。
- 燃煤机组 /
- 脱硫浆液 /
- 汞 /
- 迁移转化 /
- 添加剂 /
- 石膏 /
- 稳定性
Abstract: Slurry sample was collected from a 300 MW ultra-low emissions coal-fired power unit. The migration and transformation behaviors of mercury in the sample were investigated, and the effect of additive on the stability of mercury in solid gypsum was explored by considering the thermal release behavior and environmental risk. The results show that gaseous Hg⁰ is increased with the increase of slurry temperature, while Hg is increased in both gas phase and gypsum with the increase of slurry pH. The concentration of Cl⁻ or $ {\rm{SO}}^{2-}_{4} $ increases in slurry could inhibit the reduction of Hg²⁺ to Hg⁰ and increase Hg proportion in gypsum. However, the increase of $ {\rm{SO}}^{2-}_{3} $ concentration is beneficial to the Hg enriched in gypsum and a part of Hg²⁺ reduced to Hg⁰. When Na₂S, EDTA-2Na or DTCR-4 is added, Hg²⁺ is turned into HgS, Hg(EDTA)₂ or [ −Hg-DTCR] −_n, respectively among which more than 75% Hg is transferred to gypsum and Hg²⁺ is inhibited to reduce into Hg⁰. The thermal stability of Hg in gypsum can be ordered as Gypsum + EDTA-2Na < Gypsum + DTCR-4 < Gypsum + Na₂S < Gypsum due to the stability difference among Hg(EDTA)₂, [ −Hg-DTCR] −_n and HgS(black). By using TCLP, SPLP and MEP, the chemical stability of Hg in gypsum can be ordered as Gypsum < Gypsum + Na₂S < Gypsum + EDTA-2Na < Gypsum + DTCR-4 due to the concentration difference of water soluble mercury, acid soluble mercury and oxidizable mercury among gypsums.
- coal-fired power unit /
- WFGD slurry /
- mercury /
- migration and transformation /
- additive /
- gypsum /
- stability

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FIG. 808. FIG. 808.

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图 1 脱硫浆液汞迁移转化实验原理及流程图

Figure 1 Schematic diagram of the migration and transformation of mercury in WFGD slurry

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图 2 温度对脱硫石膏浆液中汞迁移转化的影响

Figure 2 Effect of temperature on mercury migration and transformation in WFGD slurry

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图 3 浆液pH值对脱硫石膏浆液中汞迁移转化的影响

Figure 3 Effect of pH value on mercury migration and transformation in WFGD slurry

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图 4 离子浓度对脱硫石膏浆液中汞迁移转化的影响

Figure 4 Effect of ion concentration on mercury migration and transformation in WFGD slurry

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图 5 Hg²⁺与EDTA-2Na和DTCR-4的反应产物

Figure 5 Reaction products of Hg²⁺ with EDTA-2Na and DTCR-4

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图 6 温度对加入添加剂的脱硫浆液中汞迁移转化的影响

Figure 6 Effect of temperature on Hg migration and transformation in WFGD slurry with additives

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图 7 pH值对加入添加剂的脱硫浆液中汞迁移转化的影响

Figure 7 Effect of pH value on Hg migration and transformation in WFGD slurry with additives

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图 8 离子浓度对加入添加剂的脱硫浆液中汞迁移转化的影响

Figure 8 Effect of ion concentration on Hg migration and transformation in WFGD slurry with additives

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图 9 石膏样品中总汞的热释放谱图

Figure 9 Thermograms of total Hg in gypsum samples

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图 10 石膏样品中不同形态汞的热释放谱图

Figure 10 Thermograms of Hg speciation in gypsum samples

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图 11 基于TCLP法、SPLP法和MEP法的汞浸出特性评估

Figure 11 Leaching Hg assessment by TCLP, SPLP and MEP

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图 12 固体石膏样品中汞的逐级提取结果

Figure 12 Distribution of Hg fractions in the gypsums by sequential-chemical-extraction method

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表 1 入炉煤的工业分析以及氯和汞含量

Table 1 Proximate analysis, chlorine and mercury content of feed coal

Proximate analysis w/%				S content/%	Cl content/ (mg·kg⁻¹)	Hg content/ (mg·kg⁻¹)
M	A	V	FC	S content/%	Cl content/ (mg·kg⁻¹)	Hg content/ (mg·kg⁻¹)
2.57	14.84	30.09	52.50	0.37	0.078	0.0621
not: air drying base

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表 2 本研究测量的脱硫浆液基本物性参数

Table 2 Main properties of WFGD slurry measured in this study

Sample	Hg/ (μg·L⁻¹)	Temperature/ ℃	pH	Cl⁻/ (mg·L⁻¹)	$ {\rm{SO}}^{2-}_{3} $/ (mg·L⁻¹)	$ {\rm{SO}}^{2-}_{4} $/ (mg·L⁻¹)
Slurry	157	50	5.82	4414	296	1413

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表 3 对比的燃煤机组脱硫浆液基本参数^[33-35]

Table 3 Basic properties of desulfurization slurry in coal-fired power units^[33-35]

Sample	Temperature/ ℃	pH	Cl⁻/ (mg·L⁻¹)	$ {\rm{SO}}^{2-}_{4} $/ (mg·L⁻¹)
Slurry-1^[33]	40−50	5.5−6.5	7000−20000	800−5000
Slurry-2^[34]	46	4.0−6.0	20000	11000
Slurry-3^[35]	−	4.0−5.5	6000−12000	−

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表 4 含汞化合物的释放温度特征

Table 4 Release temperatures of Hg-containing compounds

Hg-containing compounds	Temperature range of Hg release/℃	Peak temperature of Hg release/℃
Hg₂Cl₂	110−220	119 ± 10
HgCl₂	95−350	138 ± 4
HgS(black)	150−280	220 ± 11
HgS(red)	210−340	305 ± 12
HgO(yellow)	250−450	284 ± 7
HgO(red)	360−500	420 ± 10
HgSO₄	495−600	560 ± 10

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表 5 Hg²⁺与有机添加剂反应产物中汞的释放温度

Table 5 Release temperatures of mercury in the reaction products of Hg²⁺ and organic additives

Reaction product	Temperature range of Hg release/℃	Peak temperature of Hg release/℃
Hg(EDTA)₂	100−210	164 ± 4
[ −Hg-DTCR] −_n	105−230	186 ± 4

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