Modeling of Plume Opacity

• Main Authors: Lin, Yun-Yi, 林芸伊
• Other Authors: Tsai, Chuen-Jinn
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/68667367106664497811

碩士 === 國立交通大學 === 環境工程系所 === 99 === Plume opacity is a criterion of visible discharge of a factory. The solutions of white smoke are important topics in air pollution. In this thesis, plume opacity model has been developed to simulate the dispersion of normal temperature and high temperature plumes emitted by a stack of an electro-optical factory or a coal-fired power plant. The plume dispersion, mass balance, energy balance, particle growth and deliquescence were considered in the model. Mie scattering theory was used to calculate the light extinction of white plumes. The properties of the plume and plume opacity will be simulated. The plume boundaries, temperature, water vapor concentration, particle diameter and plume opacity can be predicted by the model under different conditions. The results indicate that the flue gases of an electro-optical factory are submicron particles, mainly composed of SiO2 and (NH4)2SO4. The number median diameter of the particles is found between 88.6-332.5nm, and geometric standard deviation is between 1.6-2.0. In winter, particulate matter (PM) emitted by the stack mixed with the ambient air and induced particle growth due to supersaturated water vapor. White smoke is observed clearly near the exit of a stack. The plume opacity is about 91% and the length of 10 m(wind speed 0.5 m/s), decreasing while wind speed is faster. If the relative humidity of flue gases is lower, the opacity is about 3% without particle growth which fits in with the regulations. The flue gases of a coal-fired power plant are micron particles, mainly composed of sulfate. The number median diameter of the particles is found between 180 nm, and geometric standard deviation is between 2.51. The plume temperature decrease fast, and the particle growth occurs at 2-5.7 times length of source diameter. The plume opacity reaches 100% and the length of 13(wind speed 10 m/s)-35 m(wind speed 1 m/s). The influences on plume opacity are due to particle growth and high number concentration of particles. If the emission temperature is about 100℃, particle growth will not occur in the plume. Furthermore, the decrease of discharging particles is also to reduce opacity of white smokes. The highest extinction coefficient of the particle was found to range between 0.5-1μm. As a result, removal of these particles should be able to reduce the plume opacity.