多种负荷工况下湿式电除尘器的PM2.5脱除效率及排放特征

在燃煤发电机组带100%、75%、50%负荷，每种负荷下湿式电除尘器（WESP）以高功率和节能优化2种模式运行共6种工况下，使用ELPI+测试湿式电除尘器入口和出口烟尘的质量浓度和排放特征。实验结果表明，在高负荷下，湿式电除尘器采用节能模式会导致总烟尘、PM₁₀、PM_2.5浓度均显著升高，甚至排放质量浓度超过5 mg/m³；而在中低负荷下，湿式电除尘器采用节能模式会导致总烟尘排放浓度显著升高，但PM₁₀、PM_2.5浓度则变化不显著，且粒径越小变化越小；PM₁₀、PM_2.5浓度变化对总排放的影响较小，除尘系统节能优化试验可为机组实现超低排放下的优化运行提供有力支持；湿式电除尘器入口和出口飞灰颗粒质量呈现出典型的双模态分布；湿式电除尘器以高功率运行时，2~10 μm的颗粒仅占PM₁₀质量的30%左右，湿式电除尘器以节能模式运行时，2~10 μm的颗粒可占到PM₁₀质量的50%以上。

Experimental Study on Fine Particulate Matter Removal Efficiency and the Emission Characteristics of WESP under Different Loads

In this paper, the dust mass concentrations and emission characteristics are tested using ELPI+ device at the inlet and outlet of a wet electric-static precipitator (WESP) under six different conditions, i.e., the combination of the boiler load at 100%, 75%, and 50%, with the WESP operated at high power and optimized energy-saving modes, respectively. From the experimental results, under 100% load and WESP energy-saving operation mode, significant increases are observed in the concentration of total dust emission, PM₁₀ and PM_2.5. Particularly, the total dust emission mass concentrations have even exceeded 5 mg/m³. However, under medium or low loads with WESP energy-saving operation mode, the total dust emission concentration still increases significantly, while the concentrations of PM₁₀ and PM_2.5 do not change much. The smaller the particle size, the less change of concentrations is noticed. Therefore, the energy-saving optimization test can provide technical assistance for the optimized unit operation mode with the goal of ultra-low emission also achieved at the same time. Additionally, PM₁₀ and PM_2.5 have little influence on the total dust emission under medium or low loads. The fly ash particles at the inlet and outlet of the WESP demonstrate the pattern of typical bimodal distribution. Under low or medium loads, the mass of the particles of 2~10 μm accounts for about 30% of all PM₁₀ particle mass if the WESP operates at high power mode, while that percentage jumps to 50% if it operates at energy-saving mode.