以CEMs分時監測三座氣渦輪機機組排放之氮氧化物濃度修正與總排放量誤差估算

CORRECTIONS OF NOX CONCENTRATION AND TOTAL EMISSION RATE OF THREE NATURAL GAS TURBINES TIME-SHARING BY ONE CEMS SYSTEM

吳克金(Ke-Chin Wu)

指導教授 ： 張幼珍

元智大學/工程學院/化學工程與材料科學學系/碩士(2008年)

https://doi.org/10.6838/YZU.2008.00253

摘要

本文研究之CEMs以分時監測氮氧化物與溫度，主要目的在針對國內某電廠以一套NOx監測設備，分時監測三套機組，在排放量估算上可能產生的誤差值進行評估，研究中針對連續排放監測系統CEMs量測到的氮氧化物、溫度的分布情形，以探討低氮氧化物燃燒器在空氣流量與天然氣使用量的配比及燃燒反應關係，進而建立溫度、含氧量與氮氧化物間的關聯性。其研究心得如下：
CEMs監測NOx的過程中，三部機組共同以分時的方式進行連續監測，因此在15分鐘內實際監測一部機組才5分鐘，當5分鐘監測結束後其監測值停留在最後一個值，並持續10分鐘，由此我們發現有可能造成與實際讀值的高估與低估，為此，在研究過程經由起機過程的負載變動，找出不同溫度下NOx的規律性，得到結果為實際排放的NOx總排放量大於CEMs連續監測後的總排放量約在10~12%的誤差結果。
在相同的當量比0.28下，溫度的變化約在1800~2300oF，此時NOx的變化可由60~130ppm的差距，更驗證溫度影響NOx的佐證，此時段起機的過程影響最大，NOx的排放最高濃度為127.7ppm，在實際運轉過程避免在此負載下長時間燃燒。當量比平均為0.38時，燃燒參考溫度超過2280~2350oF之後，低氮氧化物燃燒器DLN 2.6維持6Q的燃燒模式可瞬間使氮氧化物降低至10ppm以下，並維持含氧量在13.5~14%之間，此時為最佳的運轉模式。
起機過程NOx排放量為保證時段內排放之37%，停機過程NOx排放量為保證時段內排放之12%，可見起停機的NOx排放必須被環保單位正視。

關鍵字

乾低氮氧化物燃燒器 ； 分時連續監測 ； 氣渦輪機

並列摘要

The validity and correction for nitrogen oxides (NOx) concentration obtained by time-sharing CEMs monitoring of three sets of gas turbines (GT) equipped in a local power plant was investigated. Various parameters that may influence combustion, such as combustion reference temperature, airflow, natural gas flowrate were examined to find relations between NOx concentration and these combustion-related parameters.
The time-sharing works by monitoring one GT for 5-minute in every 15-minute cycle, and the last NOx value at the end of the 5-minute is used as default value for the remaining unmonitored 10-minute, thereby causing NOx concentration to be overestimated or underestimated particularly during startup and shutdown periods. Therefore, a search to find the relations between combustion-related parameters and actual NOx concentration was attempted. Through these relations, NOx concentration during unmonitored periods was corrected and the corrected total daily NOx emission was 10-12% higher than that based on timesharing CEMs values.
With an equivalence ratio of 0.28, the combustion reference temperature varies within 1800~2300oF range, and NOx concentration also varies notably from 60 to 130ppm, implying NOx concentration is closely related to the temperature. The highest NOx concentration was 127.7ppm. When the equivalence ratio was 0.38, the combustion reference temperature exceeded 2280oF. Low NOx burner (DLN 2.6) maintaining 6Q mode can reduce nitrogen oxide to 10ppm in the twinkling. During the guarantee period, Total NOx emission during GT start-up and shutdown processes were 37% and 12% of a daily emission, respectively.
Key Words: NOx, concentration correction, time-sharing CEMS monitoring, gas turbine (GT)

並列關鍵字

Gas Turbine ； Dry Low NOx Burner ； CEMs

參考文獻

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