高温环境下NO气体紫外吸收截面的温变特性研究

为了研究NO气体在不同烟气排放温度下的紫外吸收特性变化规律，测量了温度在285～410 K范围内NO气体200～230 nm紫外吸收截面随温度变化规律。采用分辨率为0.2 nm三光栅单色仪、氘灯光源和特制闭式气样室。将NO气体吸收截面分解为离散吸收和连续吸收两部分。结果表明，离散吸收具有等波长间隔分布特征，间隔约为10.5 nm。随温度升高，离散吸收峰值呈现出先抑后扬的非单调变化趋势，最大相对变化率约为19.3%，峰值位置并未出现波长红移或蓝移，谱线半宽也未出现明显的变化;连续吸收截面整体上随温度升高单调增大，且这种增强趋势随波长红移逐渐减弱。利用吸收法在线测量NO浓度时不应假定NO气体吸收截面为常数，应根据对烟气温度对NO吸收截面进行实时补偿计算，能够有效提高NO气体浓度在线测量的精度。

Study on Temperature Dependence of Ultraviolet Absorption Cross Sections of Nitric Oxide at High Temperatures

To study the temperature dependence of ultraviolet absorption characteristics of NO species in flue gas, the absorption cross sections of NO in the spectral region 200-230 nm at temperatures ranging from 285 to 410 K were measured using a grating monochromator with 0. 2 nm resolution, a deuterium lamp and a specially-fabricated closed sample cell. The absorption spectrum of NO consists of discrete bands superimposed on a continuous base. Results indicated that discrete absorption bands were pres- ent with a fixed wavelength interval of roughly 10. 5 nm. The peaks of discrete bands decreased first and started to increase later as the temperature rose from 285 to 410 K, with a maximum relative variation of 19.3%. Peak position and half width of the absorption peaks did not exhibit apparent change with the variation of temperature. Continuous absorption cross section increased monotonously with the temperature, and the variation gradient gradually decrease with wavelength red shift. The absorption cross section of NO should not be considered as constant when applied in online monitoring of NO concentration in flue gas. A compensation calculation of absorption cross section with respect to temperature effect is indispensable for the purpose of improving online measurement precision of NO concentration.