Research progress on the characteristics and control methods of SO3 and NH4HSO4 formation in coal-fired flue gas

doi:10.16085/j.issn.1000-6613.2020-1049

Abstract

Abstract:

SCR technology is widely used in treating coal-fired flue gas due to its high denitrification efficiency and good selectivity. However, SCR catalyst will oxidize the SO₂in flue gas to SO₃, which will subsequently react with NH₃ to generate ammonium bisulfate (ABS) and ammonium sulfate (AS). When the flue gas temperature is lower than the precipitation temperature of ammonium sulfate, it will deposit on the catalyst, air preheater and other attached equipment, which has caused many serious problems and brought a negative impact on the operation and environment of power plant. In this paper, the characteristics and control methods of SO₃ and ammonium bisulfate formation in coal-fired flue gas are reviewed. The formation mechanism and migration transformation characteristics of SO₃ in boiler and SCR system are analyzed. The effects of different active components on the generation of SO₃ and ammonium bisulfate on catalyst’s surface are introduced. Finally, it is proposed that the development of new catalysts is the key research direction for the control of SO₃and ammonium bisulfate formation in coal-fired flue gas.

Key words: sulfur trioxide, nitrogen oxide, selective catalytic reduction catalyst, ammonium hydrogen sulfate

摘要：

在燃煤烟气中选择性催化还原（SCR）技术由于脱硝效率高、选择性好被广泛应用，然而SCR催化剂的催化作用会使烟气中的SO₂氧化成SO₃，SO₃会与NH₃等反应生成硫酸氢铵（ABS）和硫酸铵（AS），当烟气温度低于硫酸铵盐的凝结温度时，其会沉积在催化剂、空预器及其附属设备上，引发诸多严重的问题，对电厂的运行和环境造成了不利影响。本文综述了燃煤烟气中SO₃与硫酸氢铵的生成特性及其控制方法最新进展，分析了SO₃在锅炉和SCR系统中的形成机理、迁徙转化特性，阐述了控制SO₃与硫酸氢铵生成的方法，介绍了不同活性组分对催化剂表面SO₃和硫酸氢铵生成的影响。最后提出了开发新型催化剂是燃煤烟气中SO₃与硫酸氢铵生成控制的重点研究方向。

关键词: 三氧化硫, 氮氧化物, 选择性催化还原催化剂, 硫酸氢铵

CLC Number:

X511

YIN Zijun, SU Sheng, WANG Zhonghui, WANG Lele, AN Xiaoxue, ZHAO Zhigang, CHEN Yifeng, LIU Tao, WANG Yi, HU Song, XIANG Jun. Research progress on the characteristics and control methods of SO₃and NH₄HSO₄ formation in coal-fired flue gas[J]. Chemical Industry and Engineering Progress, 2021, 40(4): 2328-2337.

尹子骏, 苏胜, 王中辉, 王乐乐, 安晓雪, 赵志刚, 陈逸峰, 刘涛, 汪一, 胡松, 向军. 燃煤烟气中SO₃与NH₄HSO₄生成特性及其控制方法研究进展[J]. 化工进展, 2021, 40(4): 2328-2337.

Figures/Tables 14

References 44

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机组编号	装机容量/MW	SO₃质量浓度/mg·m^-3
机组编号	装机容量/MW	SCR入口	SCR出口	空预器出口	电除尘器出口	脱硫装置出口	湿式电除尘器出口
A	600	19.82	30.61	28.54	24.73	18.00	—
B	600	33.14	67.45	62.62	50.61	30.65	8.22
C	600	16.61	32.52	30.21	22.69	16.68	—
D	660	34.55	74.23	70.22	53.41	40.88	—
E	660	29373	68.66	65.76	50.91	33.76	—

机组编号	装机容量/MW	SO₃质量浓度/mg·m^-3
机组编号	装机容量/MW	SCR入口	SCR出口	空预器出口	电除尘器出口	脱硫装置出口	湿式电除尘器出口
A	600	19.82	30.61	28.54	24.73	18.00	—
B	600	33.14	67.45	62.62	50.61	30.65	8.22
C	600	16.61	32.52	30.21	22.69	16.68	—
D	660	34.55	74.23	70.22	53.41	40.88	—
E	660	29373	68.66	65.76	50.91	33.76	—

吸附剂	锅炉内		SCR		空预器
吸附剂	优点	缺点	优点	缺点	优点	缺点
石灰石	可同时脱除SO₂和SO₃	导致催化剂中毒，影响ESP除尘效率	—	—	—	—
Ca(OH)₂	可同时脱除SO₂和SO₃	易结焦	延缓空预器堵塞，对飞灰质量影响小	SO₃脱除效率低，影响ESP除尘效率	SO₃脱除效率高	SO₃脱除效率低，影响ESP除尘效率
MgO	SO₃脱除产物可通过吹灰设备去除	脱除效率低于Na基和Ca基吸附剂	对ESP除尘效率影响小，延缓空预器堵塞	脱除效率低于Na基和Ca基吸附剂	—	—
Mg(OH)₂	不结焦，对催化剂影响小	吸附剂用量大，成本高	—	—	—	—
天然碱 NaHCO₃	可同时脱除SO₂和SO₃	易结焦，导致催化剂中毒	对ESP除尘效率影响小	需增加研磨设备，成本高	避免NaHSO₄在空预器沉积	与上游相比脱除效率降低
SBS Na₂CO₃	SCR宽负荷运行，脱出效率高	导致催化剂中毒	对ESP除尘效率影响小，SO₃脱除效率高	NaHSO₄会在空预器和烟道沉积	避免NaHSO₄在空预器沉积	NaHSO₄会烟道沉积，对飞灰质量影响大

吸附剂	锅炉内		SCR		空预器
吸附剂	优点	缺点	优点	缺点	优点	缺点
石灰石	可同时脱除SO₂和SO₃	导致催化剂中毒，影响ESP除尘效率	—	—	—	—
Ca(OH)₂	可同时脱除SO₂和SO₃	易结焦	延缓空预器堵塞，对飞灰质量影响小	SO₃脱除效率低，影响ESP除尘效率	SO₃脱除效率高	SO₃脱除效率低，影响ESP除尘效率
MgO	SO₃脱除产物可通过吹灰设备去除	脱除效率低于Na基和Ca基吸附剂	对ESP除尘效率影响小，延缓空预器堵塞	脱除效率低于Na基和Ca基吸附剂	—	—
Mg(OH)₂	不结焦，对催化剂影响小	吸附剂用量大，成本高	—	—	—	—
天然碱 NaHCO₃	可同时脱除SO₂和SO₃	易结焦，导致催化剂中毒	对ESP除尘效率影响小	需增加研磨设备，成本高	避免NaHSO₄在空预器沉积	与上游相比脱除效率降低
SBS Na₂CO₃	SCR宽负荷运行，脱出效率高	导致催化剂中毒	对ESP除尘效率影响小，SO₃脱除效率高	NaHSO₄会在空预器和烟道沉积	避免NaHSO₄在空预器沉积	NaHSO₄会烟道沉积，对飞灰质量影响大

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Research progress on the characteristics and control methods of SO₃and NH₄HSO₄ formation in coal-fired flue gas

燃煤烟气中SO₃与NH₄HSO₄生成特性及其控制方法研究进展

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