Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments.
Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments.
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DOI：
10.1177/0003702821990445
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发表时间：
2021-09
影响因子：
3.5
通讯作者：
Li Z
中科院分区：
文献类型：
--
作者：
Weng W;Li S;Aldén M;Li Z
氨(NH3)被认为是重要的氮氧化物(NOx)前体，也是燃烧能源利用中脱除NOx的有效还原剂，近年来已成为一种有吸引力的非碳替代燃料。为了更好地了解NH3的热化学性质，需要在高温环境中对NH3进行准确的原位检测。紫外(UV)吸收光谱是一种可行的技术。为了实现定量测量，首次实验测量了不同温度(295~590 K)下NH3分子在热气体环境中的光谱分辨紫外吸收截面。根据实验结果，确定了NH_3分子的振动常数，并用PGOPHER软件计算了NH_3分子在590 K以上高温下的吸收截面。所研究的紫外光谱覆盖了从190 nm到230 nm的波长范围，其中识别了NH3在伞形弯曲模式下的跃迁的光谱结构v2。温度越高，吸收截面越小。例如，NH3分子(6，0)振动带的吸收截面峰值从∼2 × 10−17减小到∼0.5 × 10−17 / / ，温度从2 95 K增加到1570 K。利用获得的吸收截面，实现了对不同热气体环境中NH3的原位非侵入性定量，检测下限从小于10 ppm到约200 ppm。测量了不同当量比下NH3-甲烷(CH4)-空气预混火焰火焰后区NH3和NO的浓度。
Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of NH3, accurate in situ detection of NH3 in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectrally resolved UV absorption cross-sections of NH3 in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of NH3 were determined and used for the calculation of the absorption cross-section of NH3 at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 nm to 230 nm, where spectral structures of the transition of NH3 in the umbrella bending mode, v2, were recognized. The absorption cross-section was found to decrease at higher temperatures. For example, the absorption cross-section peak of the (6, 0) vibrational band of NH3 decreases from ∼2 × 10−17 to ∼0.5 × 10−17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross-section, in situ nonintrusive quantification of NH3 in different hot gas environments was achieved with a detection limit varying from below 10 parts per million (ppm) to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of NH3 combustion process. The concentrations of NH3 and nitric oxide (NO) in the post flame zone of NH3–methane (CH4)–air premixed flames at different equivalence ratios were measured.
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