某燃煤電廠煙氣不透光率成因研究

Abstract

本研究利用美國電力研究所，針對燃煤電廠煙氣及煙柱不透光問題所發展的評估手冊，利用既有的煙氣檢測數據，評估台灣某一電廠在空污設備裝設前後，煙氣不透光率的組成及影響因子。 在僅安裝靜電集塵器條件下，某電廠煙囪煙氣中小於1μm細微粒佔煙氣不透光率組成的23.3~31.6%、大於1μm粗微粒佔41.0~49.5%、二氧化氮佔25.5~27.9%；而加裝SCR與濕式FGD設備後，小於1μm細微粒佔煙氣不透光率組成的77.7~86.2%、大於1μm粗微粒佔8.0~13.1%、二氧化氮僅佔5.8~9.2%。 本研究發現，加裝SCR及FGD後之煙囪粒狀物質量濃度高於僅安裝ESP條件，且主要質量負荷集中於0.1~1微米細粒徑範圍，佔煙氣不透光率組成的77.7~86.2%，為煙氣不透光率主因。安裝濕式FGD可去除粗微粒飛灰降低煙氣不透光率，但脫硫產物亦可受煙氣攜帶出煙囪，而增加不透光率。安裝SCR可降低二氧化氮濃度，但觸媒所轉化的亞硫酸與殘餘還原劑氨，會受濕式FGD冷凝及核化作用影響下形成細微粒，而增加粒狀物對煙氣不透光率貢獻度。

The thesis used the plume opacity model for the coal-fired power plant developed by the U.S. Electric Power Research Institute (EPRI) to investigate the causes of the opacity and its influencing parameters in a power plant in Taiwan. The study was based on the existing sampling and analysis data before and after the air pollution control devices were installed. When only the electrostatic precipitator (ESP) was installed, the contribution of the opacity by fine particles with the diameter less than 1 μm, coarse particles with the diameter greater than 1 μm and nitrogen dioxide was 23.3 ~ 31.6%, 41.0 ~ 49.5%, and 25.5 ~ 27.9%, respectively. By retrofitting the selective catalytic reduction (SCR) and the wet flue gas desulfurization (FGD) after the ESP, the contribution of the opacity by fine particles, coarse particles and nitrogen dioxide was changed to 77.7 ~ 86.2%, 8.0 ~ 13.1%, and 5.8 ~ 9.2%, respectively. This study found that by retrofitting the SCR and wet FGD, the particle concentration at the stack discharge was higher than the case when only the ESP was instualled. The majority of the particulate mass loading fell in 0.1~1 micrometer range, accounting for the majority of the opacity, 77.7~86.2%. Coarse particles, such as fly ash, could be removed by the wet FGD, but the by-products from the FGD could be carried over to the stack and increased the opacity. The concention of NO2 could be lowered by retrofitting the SCR, but the sulfite from the SCR catalyst and slipped NH3 could form condensible fine particles by nucleation and condensation effects of the wet FGD, resulting in an increase in the opacity of the flue gas.