SO2-NO2-NH3-H2O四元反应体系中气溶胶的生成特性

通过烟雾箱实验，研究了SO₂-NO₂-NH₃-H₂O四元反应体系在气-粒转化过程中新形成颗粒物数浓度与粒径分布的变化.研究发现，SO₂-NO₂-NH₃-H₂O四元反应体系具有显著的成核能力，且其成核强度大，持续时间短.当SO₂、NO₂浓度为200mg/m³，NH₃浓度为12x10^-6时，反应体系的气溶胶总个数浓度在2min时达到峰值2.5x10⁶cm^-3.缺少任一种气体均会使气溶胶成核强度下降.SO₂、NO₂及NH₃浓度分别为0的工况下气溶胶总个数浓度峰值分别下降了41.0%、83.6%及98.5%.在电厂污染气体排放浓度区间内，NO₂对气溶胶生成影响大于SO₂.燃煤电厂控制NO_x排放浓度对改善烟囱出口气溶胶数浓度更有效.在实验基础上，对颗粒物成核特性进行拟合，反应体系在气-粒转化过程中产生的新颗粒物总个数浓度及中值粒径与气态前体物浓度线性相关；采用布朗团聚模型对气溶胶成核后的团聚过程总个数浓度及粒径变化进行模拟计算，根据给定的燃煤电厂SO₂、NO₂、NH₃排放浓度，给出预测气溶胶颗粒成核速率、粒径分布及总个数浓度变化的方法.

Formation characteristics of aerosols in the SO2-NO2-NH3-H2O quaternary system

The variations in concentration and diameter distribution of newly formed particulate matter, during the gas-to-solid conversion of the SO₂-NO₂-NH₃-H₂O quaternary system, were experimentally investigated with the smog chamber in this article. This quaternary system had a significant capability of nucleation, and a large nucleation intensity in such a short duration. When both of SO₂ and NO₂ concentrations were 200mg/m³ and NH₃ concentration was 12×10^-6, the total concentration of aerosols in this system reached a peak of 2.5×10⁶cm^-3 over two minute. Moreover, the nucleation strength of the aerosol would be reduced lacking in any one among three gases. Like this typical condition that SO₂, NO₂ or NH₃ concentration was zero, the maximum concentration of aerosols decreased by 41.0%, 83.6% and 98.5%, respectively. Within the concentration ranges of SO₂, NO₂ or NH₃ emitted from coal-fired power plants, the NO₂ had a greater influence than SO₂ on the formation and agglomeration of newly formed particles. Based on experimental results, the fitting curves for nucleation characteristics of particulate matters were made. A linear correlation was observed between the total number concentration of newly formed particles and median particle diameter, and gaseous pollutant concentrations. The Brown agglomeration model was adopted to simulate the changes in total number concentration and particle size distribution of aerosols after nucleation in the agglomeration process. Finally, a method was proposed for predicting the change in the particle size distribution and total number concentration of aerosol particles, based on the typical emission concentrations of SO₂, NO₂ and NH₃ from coal-fired power plants.