Experimental study of nitrogen balance in the process of flue gas denitration by ozone low-temperature oxidation

doi:10.11949/0438-1157.20211570

Abstract

Abstract:

The synergistic removal technology of ozone oxidation pollutants utilizes the strong oxidizing property of ozone to oxidize various pollutants such as NO _x, Hg, VOCs and other pollutants with low solubility in flue gas into high valence or easily soluble forms, and combined with the tail wet spray system to achieve simultaneous removal of pollutants. Due to its advantages of low temperature window, high denitration efficiency, fast reaction rate and less difficulty in transformation, it is widely used in industrial boilers, kilns and non-electric industries. However, the actual transformation path of pollutants in this process, especially the input/output balance of NO _x, has not been verified in detail by experiments. Therefore, for the typical ozone oxidation denitrification process, this paper analyzes NO _x input/output balance and nitrogen flow direction in the process of pollutant removal. The experimental results show that the NO input in the gas phase is gradually converted into nitrate and nitrite in the liquid phase after ozone oxidation coupled with wet spraying. Under different O₃/NO molar ratios, the reduction of nitrogen in the gas phase is converted into the increase of nitrate and nitrite in the liquid phase, and there is no other nitrogen- containing form. At the same time, the conversion rate of nitrate and nitrite in the absorption slurry is also matched with the NO _x removal rate in the flue gas. Under the condition of simultaneous oxidation of NO/SO₂, adjusting the O₃/NO molar ratio, combined with the wet absorption system, it can achieve simultaneous and high-efficiency removal of NO _x /SO₂, and the system can satisfy the nitrogen input/output balance. It can provide a basis for the engineering application and popularization of ozone oxidation pollutant synergistic removal technology.

Key words: ozone oxidation, nitrogen balance, pollution, spray absorption, NO _x, reaction

摘要：

臭氧氧化污染物协同脱除技术利用臭氧的强氧化性，将烟气中溶解度较低的NO _x 、Hg、VOCs等多种污染物氧化为高价态或易溶解的形式，并结合尾部湿法喷淋系统实现污染物的同时脱除。由于其具有温度窗口低、脱硝效率高、反应速率快及改造难度小等优点，在工业锅炉、窑炉及非电行业得到广泛应用。但是在此过程中的污染物实际转化路径，尤其是氮氧化物的输入/输出平衡，目前还未有详细的验证试验支撑。因此本文针对典型臭氧氧化脱硝过程，对污染物脱除过程中的氮氧化物输入/输出平衡及氮元素流向进行了分析试验。试验结果表明，气相输入的NO经过臭氧氧化耦合湿法喷淋后逐渐转化为液相中硝酸根和亚硝酸根离子。在不同O₃/NO摩尔比下，气相氮元素的减少量均以液相中硝酸根及亚硝酸根的增加量存在，不存在其他含氮形式。同时，吸收浆液中硝酸盐及亚硝酸盐的转化率也与烟气中NO _x 脱除率相匹配。在NO/SO₂同时氧化条件下，调节O₃/NO摩尔比，结合湿法喷淋系统可以实现NO _x /SO₂的协同高效脱除，同时系统满足氮元素输入/输出平衡，为臭氧氧化污染物协同脱除技术的工程应用推广提供了依据。

关键词: 臭氧氧化, 氮平衡, 污染, 喷淋吸收, 氮氧化物, 反应

CLC Number:

X 511

Yiwei ZHANG, Hairong TANG, Yong HE, Yanqun ZHU, Zhihua WANG. Experimental study of nitrogen balance in the process of flue gas denitration by ozone low-temperature oxidation[J]. CIESC Journal, 2022, 73(4): 1732-1742.

张逸伟, 唐海荣, 何勇, 朱燕群, 王智化. 臭氧低温氧化烟气脱硝过程中的氮平衡试验研究[J]. 化工学报, 2022, 73(4): 1732-1742.

Figures/Tables 12

Fig.1 Flow direction of nitrogen in ozone oxidation denitration facilities

Fig.2 Diagram of test system

Table 1 Working conditions during the test

工况序号	测试工况
1#	O₃/NO=2，初始约250 μl/L NO，无SO₂
2#	O₃/NO=1.6，初始约250 μl/L NO，无SO₂
3#	O₃/NO=1.3，初始约250 μl/L NO，无SO₂
4#	O₃/NO=1，初始约250 μl/L NO，无SO₂
5#	O₃/NO=0.6，初始约250 μl/L NO，无SO₂
6#	O₃/NO=2，初始约250 μl/L NO，约100 μl/L SO₂
7#	O₃/NO=1.6，初始约250 μl/L NO，约100 μl/L SO₂
8#	O₃/NO=1.3，初始约250 μl/L NO，约100 μl/L SO₂
9#	O₃/NO=1，初始约250 μl/L NO，约100 μl/L SO₂
10#	O₃/NO=0.6，初始约250 μl/L NO，约100 μl/L SO₂

Fig.3 Linear fitting of NO3--N in absorption slurry at different molar ratios

Fig.4 Effect of O3 /NO molar ratio on NO x removal efficiency during single oxidation and simultaneous oxidation

Fig.5 The test result of NO oxidation alone at O3/NO=0.6

Fig.6 The test result of NO oxidation alone at O3/NO=1.3

Fig.7 The test result of NO oxidation alone at O3/NO=1.6

Fig.8 The test result of NO/SO2 simultaneous oxidation at O3/NO=0.6

Fig.9 The test result of NO/SO2 simultaneous oxidation at O3/NO=1.3

Fig.10 The test result of NO/SO2 simultaneous oxidation at O3/NO=1.6

Fig.11 The existence forms of nitrogen element under different O3/NO molar ratios

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