In situ detection of potassium atoms in high-temperature coal-combustion systems using near-infrared-diode lasers.
In situ detection of potassium atoms in high-temperature coal-combustion systems using near-infrared-diode lasers.
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DOI：
10.1016/s1386-1425(02)00049-5
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发表时间：
2002-09
期刊：
影响因子：
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通讯作者：
E. Schlosser;T. Fernholz;H. Teichert;Volker Ebert
中科院分区：
文献类型：
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作者：
E. Schlosser;T. Fernholz;H. Teichert;Volker Ebert
采用769.9 nm和767.5 nm的直接可调谐二极管激光吸收光谱测量了两种不同煤粉燃烧系统（大气或加压（12 bar））的高温（高达1650 K）烟气中钾(K)原子的原位浓度。采用两种类型的激光器（fabry - prot （FP）和垂直腔面发射激光器（VCSEL）），对其静态和动态波长调谐特性的幅度和线性进行了表征。VCSEL的宽连续电流感应调谐范围为20 cm−1（与FP的1 cm−1相比），使该激光器成为高压过程中物种监测的理想选择。将两个vcsel进行时间复用，实现对D1和D2钾的同时检测。同时检测到a波段的多条氧吸收谱线，这些谱线与K谱线的光谱距离很近，显示了用一个激光进行多种探测的可能性。在大气过程中使用FP-DL，在高压过程中使用VCSEL，确定了光谱展宽的压力依赖系数和烟气中K线的位移分别为（0.18±0.01）和（- 0.060±0.003）cm−1 / atm（在1540 K和11.2 bar下）。D1线的总宽度为60 GHz，总位移为- 20 GHz （11.2 bar/1540 K）。在不同的操作条件下，连续数天测定两个装置的K原子浓度。大气植物的典型浓度约为2 μg m−3，范围为50 ng m−3 ~ 30 μg m−3。对每个浓度值进行平均100次扫描，我们获得了1.7 s的时间分辨率和10 ng m−3的检测限，这对应于10−3 - 10−4范围内的分数吸收。与氧浓度有较强的反相关关系。在12 bar的植物中，K的浓度通常在2 μg m−3左右，但观察到K的浓度高达60 μg m−3。在这里，可以验证k信号对燃料类型的强烈依赖性。
Direct tunable diode laser absorption spectroscopy at 769.9 and 767.5 nm was used to measure potassium (K) atom concentrations in situ in the high temperature (up to 1650 K) flue gas of two different pulverized coal dust combustion systems (atmospheric or pressurized (12 bar)). Two laser types (Fabry-Pérot (FP) and vertical-cavity surface-emitting lasers (VCSEL)) were used for the spectrometer and characterized with respect to the magnitude and linearity of their static and dynamic wavelength tuning properties. The wide continuous current-induced tuning range of the VCSEL of 20 cm−1(compared to 1 cm−1for the FP) make this laser ideal for species monitoring in high pressure processes. Two VCSELs were time-multiplexed to realize the simultaneous detection of the potassium D1 and D2 lines. Several oxygen absorption lines in the A-band, which are in close spectral vicinity of the K lines, were detected simultaneously, showing the possibility of multi-species detection with one laser. Using the FP-DL for the atmospheric process and the VCSEL for the high pressure process, the pressure-dependent coefficients for spectral broadening as well as a shift of the K line in the flue gas were determined to be (0.18±0.01) and (−0.060±0.003) cm−1per atm (at 1540 K and 11.2 bar). The total width and shift of the D1 line (11.2 bar/1540 K) were 60 and −20 GHz, respectively. The K atom concentration was determined continuously for several days in both plants under various operation conditions. Typical concentrations in the atmospheric plant were around 2 μg m−3with a range of 50 ng m−3–30 μg m−3. Averaging 100 scans for each concentration value, we achieved a time resolution of 1.7 s and a detection limit of 10 ng m−3, which corresponds to a fractional absorption in the 10−3–10−4range. A strong anti-correlation with the oxygen concentration could be verified. At the 12 bar plant, the concentration was again typically around 2 μg m−3but K levels up to 60 μg m−3were observed. Here, a strong dependence of the K-signal on the type of fuel could be verified.