燃煤及煉鋼程序之PM與PAHs排放特性研究;Characteristics of PM and PAHs Emitted from Coal-fired and Steel-making Processes

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Title:	燃煤及煉鋼程序之PM與PAHs排放特性研究;Characteristics of PM and PAHs Emitted from Coal-fired and Steel-making Processes
Authors:	陳堂威;Chen, Tang-Wei
Contributors:	環境工程研究所
Keywords:	最佳可行控制技術;多環芳香烴化合物;氮氧化物;硫氧化物;細懸浮微粒;Best available control technologies (BACT);NOx;SOx;Fine particulate matter;polycyclic aromatic hydrocarbons (PAHs)
Date:	2021-07-29
Issue Date:	2021-12-07 13:31:40 (UTC+8)
Publisher:	國立中央大學
Abstract:	燃煤程序及鋼鐵業為國家不可或缺之基礎工業，其排放之PM、SOx、NOx及PAHs對大氣污染貢獻比重大。本研究針對兩座不同年份但具相同APCDs (SCR+ESP+WFGD+WESP)之燃煤鍋爐(A及B鍋爐)及鋼鐵業(燒結程序與電弧爐)進行排氣之PM、PM2.5 (FPM、CPM)、PAHs、SOx及NOx採樣分析，結果顯示燃煤A及B鍋爐之NOx排放濃度分別為59及15 ppm，以A鍋爐(η=47.2%)去除效率較B鍋爐(η=84.3%)低，且A鍋爐濃度高於BACT之規範(30 ppm)，燒結程序之NOx排放濃度為43 ppm (η=57.8%)，低於SCR預期之80%效能；燃煤鍋爐WFGD針對SOx之去除效率達99%，燒結程序之SOx排放濃度較高(17 ppm)，電弧爐袋式入口處測得之NOx及SOx濃度皆< 1 ppm。FPM採樣結果顯示燃煤A及B鍋爐之煙囪排氣分別為0.9及0.4 mg/Nm3，由SCR出口至煙囪其去除效率皆達99.9%，燒結程序及電弧爐煙囪排氣之FPM濃度則分別為8.2及 13.6 mg/Nm3，以電弧爐略高於BACT規範值(10 mg/Nm3)；此外，燃煤A及B鍋爐煙囪排氣之FPM2.5皆<0.09 mg/Nm3，燒結程序及電弧爐煙囪排氣之FPM2.5濃度則分別為1.8及3.2 mg/Nm3，整體顯示鋼鐵業之粒狀物皆略高於燃煤鍋爐；CPM排放濃度顯示燃煤A及B鍋爐分別為37.4及14.7 mg/Nm3，燒結程序及電弧爐煉鋼之CPM排放濃度則分別為 37.7及 3.4 mg /Nm3，顯示燃煤鍋爐及鋼鐵業之CPM排放濃度皆遠大於FPM，值得重視。PAHs方面，燃煤A鍋爐煙囪排氣之PAHs濃度為547 ng/Nm3，燒結程序及電弧爐煉鋼則分別為62.6及136 μg/Nm3，皆以氣相濃度遠高於固相，以2-3環數為主要物種，且部分PAHs物種有上升的趨勢，既有之APCDs難以有效去除，PAHs毒性排放濃度則以鋼鐵業(4.74-5.45 μg-BaPeq/Nm3)遠高於燃煤鍋爐(39.7 ng-BaPeq/Nm3)。另一方面，燃煤鍋爐及鋼鐵業之污染物排放係數計算，結果顯示燃煤鍋爐及燒結程序之FPM排放係數明顯低於先前文獻，僅電弧爐FPM則有較高之排放係數，且燃煤鍋爐及鋼鐵業之CPM排放係數皆遠高於FPM；此外，鋼鐵業PAHs排放係數遠大於燃煤鍋爐，值得重視。PCA結果表明燃煤鍋爐及鋼鐵業PAHs特徵物種多以4-6環PAHs為主要分布。;Coal-fired boilers and steel industry are crucial for economic development, however, emissions of NOx, SOx, PM and PAHs from these industries pose significant impact on local air quality. In this study, two coal-fired boilers (Boilers A and B) and steel-making processes including sintering process (SP) and electric arc furnace (EAF) are selected for sampling and analysis to evaluate the performance of APCDs adopted and the emission characteristics of PM, PM2.5 (FPM and CPM), SOx, NOx, and PAHs. The results show that the concentrations of NOx emitted from Boiler A and B are 59 and 15 ppm, respectively, and the removal efficiency of NOx achieved with Boiler A (η= 47.2%) is lower than that of boiler B (η=84.3%), and the NOx emitted from Boiler A is slightly higher than the BACT standard (30 ppm). The NOx concentration emitted from the SP is 43 ppm and the NOx removal efficiency is 57.8%, which is lower than the expected performance of SCR (η= 80%). Removal efficiencies of SOx achieved with WFGD of two coal-fired boilers are 99%. The SOx concentration emitted from the SP is 17 ppm, while the concentrations of NOx and SOx measured at EAF outlet are lower than 1 ppm. The FPM concentrations measured at stacks of Boiler A and B are 0.9 and 0.4 mg/Nm3, respectively, and the removal efficiencies of FPM are 99.9%. On the other hand, the FPM concentrations measured at the stacks of SP and EAF are 8.2 mg/Nm3 and 13.6 mg/Nm3, respectively. The FPM emitted from EAF is slightly higher than the BACT standard (10 mg/Nm3). The FPM2.5 emitted from both coal-fired boilers are < 0.09 mg/Nm3. FPM2.5 emitted from the SP is measured as 1.8 mg/Nm3, which is lower than that emitted from EAF (3.2 mg/Nm3). It shows that the FPM concentration emitted from the steel-making processes are higher than that of coal-fired boilers. The CPM emitted from coal-fired boilers A and B are 37.4 and 14.7 mg/Nm3, respectively, and those from SP and EAF are 37.7 and 3.4 mg/Nm3, respectively, indicating that CPM emitted from coal-fired boilers and steel-making processes are higher than FPM and deserve more attention. The PAHs concentration measured at the stack of coal-fired boiler A is 547 ng/Nm3, while those measured at SP and EAF are 62.6 and 136 μg/Nm3, respectively. The concentrations of gas-phase PAHs are higher than that of solid-phase PAHs, and are primarily composed of 2-3 ring, and existing APCDs cannot efficiently remove gas-phase PAHs. The toxic concentrations of PAHs emitted from steel-making processes (4.74-5.45 μg-BaPeq/Nm3) are significantly higher than those emitted from coal-fired boilers (39.7 ng-BaPeq/Nm3). In addition, this study shows that the PAHs of the coal-fired boiler is easily enriched in fine particles. On the other hand, the emission factors of FPM from coal-fired boiler and SP are significantly lower than other reports. However, the emission factors of particulate matter from EAF are relatively high. The emission factors of CPM from coal-fired boiler and steel-making processes are much higher than those of FPM. Moreover, the emission factors of PAHs in SP and EAF are significantly higher than those of coal-fired boilers, indicating there is room for improvement. PCA analysis results show that PAHs characteristic species of coal-fired boiler and steel-making process are 4-6 ring PAHs.
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