| 摘要: | 案例廠在製造半導體使用的清洗劑以異丙醇為主，異丙醇屬於低沸點揮發性有機氣體，對人體健康及環境造成潛在的威脅。案例廠在評估各種處理技術優缺點後，選擇活性碳流體化床連續吸脫附後焚化(本文稱為活性碳流體化床)技術控制製程排氣污染。案例廠活性碳流體化床係由吸附塔、脫附塔、氧化塔及預熱塔等設備所組成，吸附異丙醇後的活性碳經由脫附塔脫附處理後，回流至吸附塔使用；脫附塔脫附的排氣則經由氧化塔高溫燃燒。
本文控制氧化塔燃燒溫度在850 ℃至600 ℃區間，每個階段往下調整50 ℃，尋找可以達到出口排放量在0.3 kg/hr (法定值為0.6 kg/hr)以下，排氣處理削減率達90%以上的排氣入口端異丙醇(以CH4表示)濃度上限。在前述要求下，當氧化塔燃燒溫度階段調控在850、800、750、700 ℃，可處理排氣入口端異丙醇濃度上限值分別為275、232、210、185 ppm。然而，當氧化塔燃燒溫度為650及600 ℃時，製程排氣入口端濃度需以166及147 ppm為排氣入口端處理上限值，這兩個燃燒溫度雖然出口排放量符合設定值，但排氣處理削減率未符合規劃目標。
案例廠108年度製程排氣入口端異丙醇濃度分布頻率最高為150至200 ppm間，次高為200至250 ppm間；累積頻率分布中位數為180.5 ppm。109年2月案例廠設定氧化塔最適燃燒溫度為800℃，當製程排氣入口端異丙醇濃度最高為225 ppm時，仍可符合排氣出口排放量在0.3 kg/hr下，排氣處理削減率達90%以上的條件。在熱能再利用方面，案例廠氧化塔燃燒需電能成本約136萬元/年，但燃燒可提供預熱塔及脫附塔熱能191萬元/年產值。
;The studied factory used isopropanol as a major cleaning agent in the semiconductor manufacturing process. Isopropanol is a volatile organic gas with a low-boiling point and poses potential threats to human health and the environment. After evaluating the advantages and disadvantages of various treatment technologies, the studied factory chose an activated carbon fluidized bed with continuous adsorption and desorption followed by combustion technology (herein referred to as activated carbon fluidized bed) for controlling process exhaust pollution. The activated carbon fluidized bed of the studied factory is composed of an adsorption tower, desorption tower, oxidation tower, and preheating tower. The activated carbon after isopropanol adsorption is desorbed by the desorption tower and then returned to the adsorption tower for reusing; the exhaust gas desorbed by the desorption tower is combusted at the oxidation tower with high temperature.
This study seeks the upper limit of isopropanol (expressed in CH4) concentration at the exhaust inlet for a step of 50 ℃ in the range of 850 to 600 ℃ in oxidation tower, which meets 0.3 kg/hr (the legal value is 0.6 kg/hr) and over 90% reduction rate of the exhaust at the outlet. Under the previous requirements, the upper limit of isopropanol concentrations at the exhaust inlet from stepwise temperature adjustment in the oxidation tower for 850, 800, 750, and 700 ℃ were 275, 232, 210, and 185 ppm, respectively. However, the upper limit of isopropanol concentrations at the exhaust inlet was 166 and 147 ppm when the combustion temperatures of the oxidation tower were 650 and 600 ℃, respectively. Although these two combustion temperatures met exhaust requirements, the reduction rate of exhaust did not reach the planning objective.
The highest frequency distribution of isopropanol concentration in the exhaust inlet was between 150 and 200 ppm, the second-highest one was ranged from 200 and 250 ppm, and the median value of cumulative frequency distribution was 180.5 ppm for the studied factory in 2019. In February 2020, the studied factory determined to set the combustion temperature of the oxidation tower at 800 °C. Based on the monitored data, the exhaust at the outlet could still meet the exhaust emission requirements at 0.3 kg/hr and over 90% reduction rate when the isopropanol concentration at the exhaust inlet reached as high as 225 ppm. As to heat energy reuse, this study assessed that the electricity cost of the oxidation tower was about NT$1.36 million/yr in contrast to about NT$1.909 million/yr worth of the heat produced from the combustion and provided for preheating and desorption towers. |
