脉冲电晕放电过程中OH自由基等活性基团的空间分布特性对燃煤烟气污染物的氧化脱除具有重要作用。为了探索脉冲电晕放电污染物控制技术的机理, 采用激光诱导荧光法检测线板式反应器内部脉冲电晕放电过程中OH自由基的空间二维分布特性, 主要研究了不同相对湿度和含氧量对OH自由基空间二维分布特性的影响。实验表明, 脉冲电晕放电过程中OH自由基主要存在于线电极下方的区域中, 并以线电极为中心面向板电极呈现扇形分布, 并且其扇形分布区域的纵向长度和横向宽度的最大值均小于1 cm; 相对湿度的增大有利于OH自由基的生成, 促进OH自由基空间二维分布区域面积的扩大, 当相对湿度为65%时OH自由基的空间二维分布区域面积达到最大值; 当含氧量为2%时最有利于OH自由基的生成, 并且OH自由基的空间二维分布区域面积达到最大值, 当含氧量超过15%时对OH自由基的生成及其空间二维分布主要起抑制作用。同时, 相对湿度和含氧量的增加均提高了激发态OH自由基中猝灭部分所占的比重, 从而降低了OH自由基的荧光产率, 其中含氧量对OH自由基荧光产率和OH自由基空间二维分布的影响作用大于相对湿度。

Pulsed corona discharge in atmosphere has been widely regarded as an efficient flue gas treatment technology for the generation of active radical species, such as the OH radicals. The spatial distribution of OH radicals generated by pulsed corona discharge plays an important role in decomposing pollutants. The two-dimensional (2-D) distribution of OH radicals of positive wire–plate pulsed corona discharge was detected using laser-induced fluorescence (LIF). The influence of relative humidity (RH) and oxygen concentration on the 2-D distribution of OH radicals were investigated. The results indicated that the 2-D distribution of OH radicals was characterized by a fan-shaped distribution from the wire electrode to plate electrode, and both the maximum values of vertical length and horizontal width of the fan area was less than 1 cm. The 2-D distribution area of OH radicals increased significantly with increasing the RH and the optimum condition was 65% RH. The optimal level of the oxygen concentration for the 2-D distribution area of OH radicals was 2%. The process of OH radical generation and 2-D distribution area of OH radicals were significantly interfered when the oxygen concentration was larger than 15%. The total quenching rate coefficients for different RH values and oxygen concentration in this study were used to calculate the fluorescence yield of OH radical. The fluorescence yield, which is the ratio between the emission rate (Einstein coefficient) and the sum of the emission rate and quenching rate, was used to normalize the 2-D distribution area of OH radicals. The fluorescence yield of OH radical decreased with increasing the RH and oxygen concentration linearly and rapidly. It was also found that compared with the RH, the influence of the oxygen concentration had more notable effect on the fluorescence yield of OH radical and 2-D distribution area of OH radicals.