垃圾焚烧脱硝催化剂钙镁失活与活性恢复特性

doi:10.16085/j.issn.1000-6613.2022-1392

摘要/Abstract

摘要：

以国内某垃圾焚烧电厂失活选择性催化还原（SCR）脱硝催化剂为研究对象，针对Ca、Mg失活因素进行失活特性研究，同时探讨垃圾焚烧失活催化剂的活性恢复方法与原理。对新催化剂、失活催化剂和再生催化剂样品进行脱硝性能对比测试。利用扫描电子显微镜（SEM）、N₂吸附-脱附和X射线荧光光谱（XRF）表征催化剂样品的表面结构和化学组成；进行X射线光电子能谱（XPS）和傅里叶变换红外光谱（FTIR）测试，分析失活和再生催化剂的化学形态变化；采用NH₃程序升温脱附（NH₃-TPD）和H₂程序升温还原（H₂-TPR）研究催化剂的酸性位点变化和氧化还原特性。结果表明，由于受到Ca、Mg等失活因素的影响，失活催化剂脱硝性能大幅下降，300~350℃温度区间内的脱硝效率从新催化剂的95%以上下降到80%左右；利用“EDTA清洗+活性物质负载”方法再生后的催化剂脱硝能力明显恢复，RegCat样品在300~350℃温度区间的脱硝效率可恢复至新催化剂水平。Ca、Mg在催化剂表面形成性质稳定的硫酸盐，同时消耗大量表面活性氧，从而抑制催化剂的活性。此外，Ca还会以CaO的形式在催化剂表面沉积，对催化剂造成物理失活。活性恢复后的催化剂表面Ca、Mg、S等有害物质被有效去除，催化剂表面酸性位点和氧化性能得以明显恢复。

关键词: 烟道气, 选择催化还原, 催化剂, 失活, 活性, 碱土金属

Abstract:

The deactivation characteristics of Ca and Mg of selective catalytic reduction (SCR) denitration catalyst were studied on the catalyst from a domestic waste incineration power plant, and the activity recovery method and mechanism of the waste catalyst were discussed. The denitration performance of new catalyst, deactivated catalyst and regenerated catalyst samples was compared and tested. Scanning electron microscopy (SEM), N₂ adsorption-desorption and X-ray fluorescence spectroscopy (XRF) were used to characterize the surface structure and chemical composition of the catalyst samples. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the chemical changes between the deactivated and regenerated catalysts, while NH₃ temperature programmed desorption (NH₃-TPD) and H₂ temperature programmed reduction (H₂-TPR) were used to study the acid site changes and redox characteristics of the catalysts. The results showed that due to the deactivation of Ca and Mg, the denitration performance of the deactivated catalyst decreased significantly, and the denitration efficiency in the temperature range of 300—350℃ decreased from more than 95% of the new catalyst to about 80%. However, the denitration capacity was significantly restored by using the method of “EDTA cleaning + active material loading”, and the denitration efficiency of RegCat could be restored to the level of new catalyst in the temperature range of 300—350℃. Ca and Mg formed sulfate on the surface of the catalyst, and consumed a large amount of surface active oxygen, so as to lower the activity of the catalyst. In addition, Ca would also deposit on the catalyst surface in the form of CaO, causing physical deactivation of the catalyst. After the activity recovery, the harmful substances such as Ca, Mg and S on the catalyst surface were effectively removed, and the acid sites and oxidation properties of the catalyst surface were significantly restored.

Key words: flue gas, selective catalytic reduction, catalyst, deactivation, reactivity, alkaline-earth metal

中图分类号:

X511

何川, 吴国勋, 李昂, 张发捷, 卞子君, 卢承政, 王丽朋, 赵民. 垃圾焚烧脱硝催化剂钙镁失活与活性恢复特性[J]. 化工进展, 2023, 42(5): 2413-2420.

HE Chuan, WU Guoxun, LI Ang, ZHANG Fajie, BIAN Zijun, LU Chengzheng, WANG Lipeng, ZHAO Min. Characteristics of calcium and magnesium deactivation and regeneration of waste incineration SCR catalyst[J]. Chemical Industry and Engineering Progress, 2023, 42(5): 2413-2420.

图/表 11

图1 脱硝性能测试系统示意图

图2 催化剂脱硝性能测试结果

图3 新催化剂、失活催化剂和活性恢复后催化剂的SEM图像

表1 催化剂样品BET比表面积、孔容、孔径测试结果

样品	BET比表面积/m²·g^-1	孔容/cm³·g^-1	平均孔径/nm
NewCat	95.23	0.32	13.31
SpentCat	67.19	0.22	16.24
RegCat	88.36	0.30	14.27

表2 催化剂样品成分分析

样品	质量分数/%
样品	TiO₂	WO₃	V₂O₅	CaO	MgO	SO₃	Al₂O₃	SiO₂
NewCat	81.25	5.35	4.61	1.09	0.25	0.20	0.53	4.64
SpentCat	77.01	4.26	3.50	2.87	1.27	0.93	1.92	7.02
RegCat	80.20	4.84	4.83	1.24	0.34	0.35	0.88	5.12

图4 新催化剂和失活催化剂的O 1s、V 2p XPS图谱

图5 失活催化剂的Ca 2p、Mg 1s和S 2p XPS图谱

图6 失活催化剂的FTIR图谱

图7 活性恢复后催化剂的O 1s、V 2p XPS图谱

图8 催化剂的NH3-TPD结果

图9 催化剂的H2-TPR结果

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