| 摘要: | 氮氧化物對環境之衝擊廣泛且深遠，環保單位為改善空氣品質要求氮氧化物主要貢獻源進行排放量減量及改善，本研究選定北部某石化廠之原油常壓蒸餾程序(M01)，探討以選擇性觸媒還原法(SCR)降低加熱爐後端排放管道之氮氧化物濃度及效率。研究顯示選擇性觸媒還原系統(SCR)於入口溫度250℃、進口風量972.5 Nm3/min、空間流速6,008 hr-1、入口氮氧化物濃度93.4 ppm、液氨注入量4.3 kg/hr，氨當量比為1.05之操作條件下達最高去除效率96%，且出口氮氧化物濃度為3.5 ppm、逃逸氨僅1.2 ppm，為維持去除效率達80%以上，當入口濃度介於49 ppm至77 ppm時，液氨注入量須維持在2.5 kg/hr至4.0 kg/hr，入口濃度介於80 ppm至95 ppm時，液氨注入量須維持在4.3 kg/hr至5.4 kg/hr，液氨注入量如低於上述區間去除效率將明顯降低，比對增設選擇性觸媒還原系統(SCR)前後之變化，氮氧化物於增設前平均出口濃度為66.3 ppm，增設後出口濃度為3.5 ppm至12.5 ppm，出口濃度減少81%至95%；氮氧化物排放量於增設前為144 ton/year，增設後為28 ton/year，減量116 ton/year；每年空污費於增設前1,440,000元，增設後280,000元，每年可減少1,160,000元。;The impact of nitrogen oxides (NOx) on the environment and human health is extensive and far-reaching. The government has taken action to improve the air quality by reducing NOx emissions from major stationary sources. This study investigates the efficacy of selective catalytic reduction (SCR) system installed in a crude oil distillation process (M01) of the petrochemical plant in northern Taiwan for reducing NOx emission via the analysis of operating parameters and CEMS data. The results show that as the SCR was operated with the temperature of 250℃, gas flow rate of 972.5 Nm3/min, space velocity of 6,008 hr-1, inlet NOx concentration of 93.4 ppm, ammonia injection rate of 4.3 kg/hr, and ammonia equivalence ratio of 1.05, the best NOx removal efficiency (96%) could be achieved. In the meantime, the outlet NOx concentration was reduced to 3.5 ppm and the ammonia slip was low (1.2 ppm). In order to maintain the NOx removal efficiency above 80%, when the inlet NOx concentration is between 49 ppm ~ 77 ppm, the ammonia injection rate needs to be maintained at 2.5 kg/hr ~ 4.0 kg/hr. As the inlet NOx concentration is between 80 ppm ~ 95 ppm, the ammonia injection rate should be controlled at 4.3 kg/hr ~ 5.4 kg/hr. If the ammonia injection rate is lower than the above-mentioned range, the removal efficiency will be significantly reduced. Comparing the differences before and after installing selective catalytic reduction (SCR) system, the outlet NOx concentration is reduced from 66.3 ppm to 3.5 ppm ~12.5 ppm. It decreases by 81%~95% and the NOx emission is reduced from 144 ton/year to 28 ton/year. Meanwhile, the air pollution fee is reduced from NT$ 1,440,000/yr to NT$ 280,000/yr. |
