燃煤电厂烟气湿度控制对颗粒物采样结果的影响研究

The Influence of the Flue Gas Humidity Control on Particulate Matter Measurement from Coal-fired Power Plant

为探究超低排放改造后燃煤电厂高湿烟气对低浓度颗粒物采样结果的影响,利用扩散干燥管控制湿度,可降低因蒸气凝结而产生的颗粒物转移损失。在实验室搭建烟气发生装置模拟电厂高湿烟气,研究相对湿度对低浓度颗粒物测量结果的影响,并对循环流化床燃煤电厂高湿烟气中低浓度颗粒物进行现场测试。结果表明,在电厂使用常规采样方法采集到的TSP、PM10和PM2.5质量浓度分别为2.73 mg/m^(3)、2.18 mg/m^(3)和1.69 mg/m^(3),控制烟气相对湿度在95.1%~96.4%后,所采集到的TSP、PM10和PM2.5质量浓度分别为相对湿度98.2%时的1.36~1.65倍、1.24~1.96倍和1.03~2.20倍。水溶性离子NH_(4)^(+)、Cl^(-)、SO_(4)^(2-)为采样电厂颗粒物中主要组成部分,约占总离子数的88.3%~99.7%。经扩散干燥管控制湿度后,采集到的颗粒物中TSP、PM_(10)和PM_(2.5)水溶性离子总质量浓度分别为采用传统方法时的1.72倍、1.82倍和1.74倍。实验证明了燃煤电厂颗粒物采样中使用扩散干燥管控制烟气湿度可降低凝结损失,提高颗粒物的采集效率和测定结果的准确性。

To investigate the effect of high humidity of the flue gas on the sampling results of low-concentration particulate matter in coal-fired power plants with ultra-low emission technologies,the flue gas humidity is con⁃trolled by using a diffusion dryer to reduce vapor condensation onto the surface of the sampling tube,thereby re⁃ducing particulate matter(PM)transfer losses due to the PM adsorption onto a wet surface.A high-humidity flue gas simulation is performed to investigate the effect of relative humidity on PM concentration reduction.A field study is carried out at a CFB coal-fired power plant to investigate the impact of relative humidity on the PM measurement.The results show that the mass concentrations of the TSP,PM10,and PM2.5 in the power plant using conventional sampling methods are 2.73 mg/m^(3),2.18 mg/m^(3),and 1.69 mg/m^(3),respectively.For the sampling method with humidity control in the range of 95.1%~96.4%,the mass concentrations of TSP,PM_(10),and PM_(2.5) are 1.36~1.65 times,1.24~1.96 times,and 1.03~2.20 times higher than those at a relative humidity of 98.2%,respectively.Water-soluble ions NH+4,Cl-,SO2-4 are the main components of the PM in the measured power plant,accounting for about 88.3%~99.7%of the total ions.After controlling the humidity by the diffusion drying tube,the total mass concentrations of TSP,PM10 and PM2.5 water-soluble ions collected were using traditional methods’1.72 times,1.82 times and 1.74 times,respectively.It showes that flue gas humidity control helps to reduce the PM transfer loss due to adsorption onto the inner surface of the sampling tube,improving the efficiency of PM collection to ensure the accuracy and representativeness of the samples.