氯添加对燃煤过程中汞析出规律的影响

doi:10.16085/j.issn.1000-6613.2021-1362

摘要/Abstract

摘要：

首先利用管式炉对燃煤及燃煤加氯后煤中汞排放进行研究，结果表明，对于神混煤而言，原煤燃烧后烟气中单质Hg⁰和氧化态汞Hg²⁺的比例分别为74.3%、25.7%。添加Cl后，烟气中Hg²⁺的比例有所上升，当加氯量为0.015%、0.030%和0.045%时，烟气中Hg²⁺的比例分别上升为32.7%、36.1%和40%，随加氯量的增加，其对汞的氧化作用也随之增强。在现场工程示范试验中，利用脱硫废水中的氯氧化烟气中的汞，以达到脱硫废水与烟气中的汞协同脱除的目的。结果表明，随着脱硫废水喷洒煤的量越大，进入SCR烟气中Hg²⁺比例增大，经过SCR后Hg²⁺的比例随之增大。由于飞灰对Hg²⁺的吸附能力较Hg⁰强，电除尘系统的脱汞效率提高，但脱硫废水喷洒煤对湿电除尘系统的脱汞效率影响不大。总之，脱硫废水喷洒量越大，燃煤机组烟气净化设备对汞协同去除效率也随之提高。

关键词: 烟气脱汞, 管式炉, 氯添加, 脱硫废水

Abstract:

In this paper, mercury emissions from coal combustion and coal chlorination were investigated by using a tubular furnace. The results showed that the percentage of simple substance Hg⁰ and oxidized Hg²⁺ in the flue gas after the combustion of raw coal is 74.3% and 25.7%, respectively. With the addition of Cl, the proportion of Hg²⁺ in the flue gas increased. When the chlorine was 0.015%, 0.030% and 0.045%, the ratio of Hg²⁺ in the flue gas increased by 32.7%, 36.1% and 40%, respectively, with the increase of chlorine, and its oxidation of mercury was also enhanced. In the field engineering demonstration test, mercury in the hydraulitis in the desulfurized wastewater was utilized to achieve the purpose of desulfurization wastewater and the mercury in the flue gas. With the increase of the amount of desulfurization wastewater sprayed on coal, the proportion of Hg²⁺ in the flue gas entering the SCR and passing through the SCR increased. Since the adsorption capacity of fly ash to Hg²⁺ was higher than that of Hg⁰, the mercury removal efficiency of the electrostatic precipitation system was improved. However, desulfurization wastewater spray coal on the demellular efficiency of wet electric dust removal system was not affected. Conclusively, with increase in the amount of the desulfurization wastewater spray, removal efficiency of mercury by flue gas purification equipment of coal-fired units could be raised.

Key words: flue gas desimulation, tube furnace, chlorine addition, desulfurization wastewater

中图分类号:

TQ534.9

肖国振, 仲兆平, 姜超, 韩磊, 马天霆, 张杉, 金保昇. 氯添加对燃煤过程中汞析出规律的影响[J]. 化工进展, 2021, 40(12): 6557-6563.

XIAO Guozhen, ZHONG Zhaoping, JIANG Chao, HAN Lei, MA Tianting, ZHANG Shan, JIN Baosheng. Effect of chlorine addition on mercury precipitation during coal combustion[J]. Chemical Industry and Engineering Progress, 2021, 40(12): 6557-6563.

图/表 12

表1 燃煤元素分析及工业分析

工业分析/%					元素分析/%
M_ad	A_ad	V_ad	F_c，ad		C_ad	O_ad	N_ad	H_ad	S_t，ad	Cl_ad	Hg
15.49	12.19	30.50	41.82		52.31	11.24	0.85	4.56	0.55	0.13	1.502×10^-5

图1 管式炉实验系统

表2 脱硫废水中Cl-浓度

废水喷洒量/t·h^-1	Cl^-浓度/mg·L^-1	Cl^-相对含量/%
0	9600	0
3	10252	0.0151
6	10734	0.0322
9	11520	0.0518
12	11845	0.0711

图2 工艺流程1—输煤皮带；2—喷嘴；3—水泵；4—废水缓冲箱；5—PPR水管；6—电厂现有废水管路；7—废水池水泵；8—脱硫废水池

图3 煤燃烧过程中气态汞形态分布

图4 添加不同浓度氯煤中汞的析出情况

图5 添加不同浓度氯煤中汞形态及其分布比例

图6 脱硫废水喷洒量对SCR入口烟气中汞浓度及氧化态汞比例的影响

图7 SCR脱硝系统对烟气中汞的影响

图8 电除尘系统后烟气中汞的分布

图9 湿法脱硫系统后烟气中汞的分布

图10 湿式电除尘系统后烟气中汞的分布

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