Evolution of Condensable Fine Particle Size Distribution in Simulated Flue Gas by External Regulation for Growth Enhancement

摘要

Condensation fine particles (CFPs) from coal-fired flue gas harm humans and the environment after being emitted into the atmosphere. Given their small size (＜0.1 μm), difficulty arises in efficiently removing CFPs by wet electrostatic precipitators and mist eliminators. In this work, a laboratory apparatus was used to study the CFP growth under simulated power plant conditions. Four methods were independently investigated to increase the particle size: addition of ammonia, addition of fly ash, decreasing temperature, and applying an electrical discharge. Results demonstrated that the CFP size distribution possessed a unimodal structure with peak at 0.05 μm. At increased ammonia concentration from 10 to 30 ppm, the peak of growth factor shifted rightward and increased from 1.21 to 1.35 and the range of growth factor ＞1 was significantly broadened due to joint action of multiple mechanisms. Fly ash acted as the core, and CFPs adhered to the ash surface when forming ash-salt droplets. Cooling flue gas could also enhance the CFP growth due to vapor condensation. At decreased temperature from 45 to 30 ℃, the median diameter of CFPs increased by 15%. Finally, the growth and agglomeration of CFPs can be further enhanced when an external electrical field was utilized. The size range of growth factor ＞ 1 can be broadened, and the peak growth factor significantly increased at 8 kV applied voltage. The research findings provide valuable guidance for effectively improving the CFP removal efficiency by external regulation for growth enhancement.