Research on laser online monitoring equipment for high-temperature corrosive gas in coal-fired boilers
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摘要:
燃煤锅炉燃烧场的经济性、安全性和环保性对于智慧电厂建设具有重要意义。H2S和CO是燃煤锅炉燃烧场的两种主要高温腐蚀气体，它们不仅腐蚀锅炉近壁面，尾气对大气环境的危害也极其严重。基于近红外可调谐半导体激光吸收光谱技术，结合波长调制光谱技术和频分复用技术，研制了一款无人值守的燃煤锅炉主燃区的H2S和CO气体浓度实时在线监测设备。仿真模拟了
6335 ~6341 cm−1范围内的气体吸收光谱，并选定1.5 μm附近的近红外激光器作为激光光源。研制了一套耐高温耐腐蚀的Herriott型多光程池，使激光与气体相互作用的有效光程达15 m；开发了硬件电路及相应的固件程序，实现了H2S和CO吸收光谱信号的二次解调与浓度反演。线性度和Allan方差实验表明，其线性拟合相关系数分别为0.9998 和0.9995 ，在73 s和53 s的积分时间下，H2S和CO的最低检测极限分别为0.2×10−6 mol/mol和0.344×10−6 mol/mol。最后，将研制的设备在某300 MW电负荷的四角切圆燃煤锅炉主燃区燃烧气氛场进行应用示范，对水冷壁附近的H2S和CO进行同步测量。结果表明，锅炉中H2S和CO的浓度呈正相关，厌氧燃烧会导致两种气体的含量增加，造成对水冷壁的腐蚀。Abstract:The coal-fired boiler combustion process's economic, safety, and environmental performance holds great significance when constructing smart power plants. In coal-fired boiler combustion, H2S and CO are the two main high-temperature corrosive gases. They not only corrode the boiler near the wall surface but also pose severe harm to the atmospheric environment through their exhaust gases. Based on the near-infrared tunable diode laser absorption spectroscopy technology, combined with wavelength modulation spectroscopy and frequency division multiplexing technology, an unstaffed online real-time monitoring instrument for H2S and CO gas concentrations in the main combustion zone of coal-fired boilers was developed. Gas absorption spectroscopy in the
6335 ~6341 cm−1 range was simulated, and two near-infrared lasers near 1.5 μm were selected as the laser source. A high-temperature resistant and corrosion-resistant Herriott-type multi-pass cell was developed to attain an effective optical path length of 15 m for the interaction between laser and gas. Hardware circuits and corresponding firmware programs were developed to attain secondary demodulation of the absorption spectroscopy signals of H2S and CO and concentration inversion. The linearity and Allan variance experiments showed linear fitting correlation coefficients of0.9998 and 0.9995. At 73 s and 53 s integration times, the minimum detection limits for H2S and CO were 0.2×10−6 mol/mol and 0.344×10−6 mol/mol, respectively. Finally, the developed instrument was applied in the combustion atmosphere of the main combustion zone of a 300 MW tangential four-corner coal-fired boiler, and synchronous measurements of H2S and CO near the water-cooled wall were conducted. The results indicated a positive correlation between the concentrations of H2S and CO in the boiler, with anaerobic combustion leading to an increase in the content of these gases and causing corrosion to the water-cooled wall. -
图 3 H2S和CO吸收信号的幅度与标准气体浓度的关系
Figure 3. The relationship between the amplitude and standard gas concentration for H2S and CO absorption signals
图 4 10×10−6 mol/mol的H2S和100×10−6 mol/mol的CO吸收信号的Allan方差随积分时间的变化情况
Figure 4. Allan variance of 10×10−6 mol/mol H2S and 100×10−6 mol/mol CO absorption signals varying with integration time
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