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空氣污染物自動連續測定儀各偵測原理之準確性評估

中文摘要 本研究目的為評估粒狀污染物及氮氧化物之自動連續檢測方法之差異。粒狀污染物部分,乃就貝他射線衰減法(NIEA A206.10C)和慣性質量法(NIEA A207.40C)兩種自動監測儀檢測方法之「檢測原理」、「適用範圍」、「偵測極限」、「反應時間」之差異與微粒種類(低原子量與高原子量)對兩種自動監測儀量測結果之影響。氮氧化物部分以化學發光法(NIEA A444.70C, CLD)及非分散性紅外線法 (NIEA A411.71A, NDIR)兩種排放管道自動連續檢測方法為探討對象,比較其「檢測原理」、「適用範圍」、「干擾物質」、「偵測極限」、「遲滯時間」、「上升時間」、「下降時間」之差異。另篩選不同類型之大氣及排放管道,以同時間、同污染源地點之現場連續監測,比較粒狀污染物及氮氧化物各兩方法實測數據之差異,並評估其數據準確性及相關性。周界空氣中氮氧化物(NIEA A417.10T)自動連續檢測干擾之探討,乃設計實驗評估NH3對該方法之結果影響。本計畫已完成粒狀污染物及氮氧化物自動連續測定儀各偵測原理之準確性評估,其研究成果概述如下: 粒狀物實驗室測試方面,濾紙面積比例評估顯示,隨著濾紙面積增加,Ipass減少,而Ipenetration增加,Itotal也成上升趨勢,濾紙面積所佔比例越多,整體射線強度下降越多。換言之微粒沉積於濾紙若不均勻將會造成Beta gauge量測值的低估。Home-made Beta gauge測試不同粒徑大小壓克力微粒和質量衰減係數關係,顯示微粒粒徑差異並不會影響所偵測之μ值。反應時間方面,Wedding需要三個小時才能夠達到穩定濃度,但是TEOM與VEREWA則在一個小時內即可達穩定濃度。不同微粒濃度比測結果顯示,TEOM測值與濾紙採樣值最為接近,VEREWA測值則略高於濾紙採樣值,高濃度微粒時Wedding測值有偏高的現象。溼度變異對於三台自動監測儀則影響不大。不同物質具有不同Z/A值,Z/A值越高則μ值越小,另外,Sample Equilibration System 之去水反應顯示Nafion能有效去除氣流中的水份,相對濕度20-90%下,氣流經過Nafion幾秒內溼度即迅速降到大約20%。但此去水系統易造成微粒穿透率的降低,且微粒累積會進一步造成空氣阻抗的增加與微粒穿透率的惡化。環境採樣方面,環境濃度大於40μg/m3時,VEREWA測值會大於TEOM,若環境濃度小於40μg/m3時,其測值會小於TEOM。 氮氧化物實驗室測試方面,參考環檢所及美國ETV測試方式,評估CLD與NDIR氮氧化物自動監測法之偵測極限分別為1.4 ppm、 8.6 ppm,兩方法平均上升應答時間分別為135、85 sec ;平均下降時間為150、120 sec。其次,CO2干擾測試顯示,煙氣CO2濃度超過5%時,兩方法監測值受其正干擾現象影響顯著,5%CO2致兩方法不同濃度氮氧化物之正干擾現象相當;8%CO2致CLD干擾影響較NDIR顯著;而兩氮氧化物自動方法受低濃度1%CO2干擾影響不甚明顯。CO干擾模擬試驗結果顯示,CO濃度(<1000ppm)致NDIR或CLD自動儀濃度干擾狀況不明顯。周界空氣NH3干擾測試顯示,NH3致周界空氣NOx自動儀監測之正干擾現象明顯,NH3致周界NOx之正干擾效應為非線性增加,其未干擾與顯著干擾間之臨界濃度約為20 ppb。 氮氧化物現場比測方面,六處排放管道現場比測結果顯示, NDIR與CLD監測儀經品保查核後之現場檢測數據,除資源回收廠A (P301) 之CLD方法相較於NDIR濃度平均仍存在8.3 ppm之差值外,其餘五處管道兩方法檢測濃度平均之絕對差值小於3 ppm。比較煙氣物化特性與SO2檢測結果顯示,CO2濃度超過8%之五處管道,其CLD 檢測平均濃度略高於NDIR檢測值。
中文關鍵字 空氣污染物,自動監測儀,偵測原理,準確性

基本資訊

專案計畫編號 EPA-92-E3S2-02-01 經費年度 092 計畫經費 1400 千元
專案開始日期 2003/01/01 專案結束日期 2003/12/31 專案主持人 許逸群
主辦單位 環檢所 承辦人 執行單位

成果下載

類型 檔名 檔案大小 說明
期末報告 0000036314.zip 3MB [期末報告]

Accuracy Estimate of Air Pollutant Automatic Monitor Measurement Technology

英文摘要 This research investigates the accuracy differences between the automatic monitoring methods of PM10 (β-gauge and TEOM) in ambient air and NOx ( NDIR and CLD) inside the stack. The estimated items in laboratory include the principles, the ranges of monitoring concentrations, interferences, the detection limits and the response times. Field samplings work at the same time to compare the factual differences in monitoring data for the above automatic monitoring methods of PM10 and NOx. We summarize the fruitful results as following: On the part of PM10, the results of uniformity test showed that the β-count increased with decreasing uniformity, indicating that the β-gauge might underestimate when non-uniform aerosol deposition occurred. From the perspective of response time that Wedding took longest (3 hours) to reach stable concentration, while VEREWA and TEOM can attain stable concentrations within one hour. In terms of accuracy, TEOM has the best agreement with the filter method. The relative humidity had no obvious effect on the performance of these real time instruments. The mass attenuation coefficient was found to decrease with increasing Z/A value, indicating a strong material dependence. The test results of Sample Equilibration System revealed that Nafion removed the water effectively. In the ambient RH range from 20% to 90%, moisture could be maintained around 20% in the sensing unit after the ambient air passing through the SES. On the part of NOx, the measured results of the detection limits for the automatic monitoring methods of NDIR and CLD were 1.4 and 8.6 ppm, respectively. The results of interfered tests by CO2 showed that NO monitoring values both increased with increasing CO2 concentrations, indicating that NO monitoring values of NDIR and CLD inside the stack might overestimate when the additive interference occurred, CO2 concentrations more than 5% especially. On the other hand, the additive interference of NH3 were obvious and non-linear in ambient NO monitoring. The critical concentration was about 20 ppb.
英文關鍵字 air pollutant,automatic monitor,monitoring technology,accuracy