| 摘要: | 為減少二氧化碳排放量，避免溫室氣體對環境影響持續惡化，除了以法規政策限制產業界之二氧化碳排放總量外，亦可透過提高濃縮後二氧化碳之濃度，使其成為高附加價值產品來提供新應用途徑，以達成循環經濟(Circular economy)之工業應用。
變壓吸附法為一連續性循環程序氣體吸附分離技術，利用吸附劑對氣體混合物中各成分之吸附能力的不同而產生的吸附選擇性來篩選氣體，並利用高壓吸附、低壓脫附來得到高濃度的產物。
本研究首先為確認模擬程式之可靠度，建置一雙塔六步驟PSA程序實驗設備進行純化氣化合成氣經過富氧燃燒及除水後之氣體，並將兩者結果進行驗證。將研究內容分為兩部分，選用UOP 13X沸石作為吸附劑。第一部分為利用三塔九步驟變壓吸附系統，以亞臨界燃煤鍋爐排煙氣，經除硫、除水後之15%二氧化碳與85%氮氣為組成進料，處理氣體量為72.3 L/min (NTP)，進行模擬，得到在進料壓力2.6 atm、抽真空壓力0.05 atm、進料溫度298.14 K、高壓吸附時間390秒、同向減壓時間40秒、逆向減壓時間300秒、壓力平衡時間50秒下，得塔頂產物氮氣純度98.35% ，回收率94.06%，塔底產物二氧化碳純度89.94%，回收率89.54%，機械能耗則為1.38 GJ/tonne-CO2。
第二部分利用四塔二十步驟變壓吸附程序純化15 MW氣化爐合成氣經富氧燃燒及除水之氣體中二氧化碳。生質物/粉煤於氣化爐中氣化產生之合成氣經過富氧燃燒及除水後，其組成約為95% - 97.4%二氧化碳濃度氣體及少量氮氣、氬氣，我們以氮氣取代氬氣並保守以95%二氧化碳及5%氮氣作為進料，藉由探討塔直徑和高度比對進料流量、塔底產物二氧化碳純度及回收率之影響，得到在塔直徑131.678 cm，塔長407 cm，進料壓力5 atm，抽真空壓力0.238 atm，進料溫度338.14 K下，進料流量為111900 L/min (STP)，塔底產物二氧化碳純度99.999944%，回收率9.574%，機械能耗則為2.53 GJ/tonne-CO2。最後，為有效找出最佳操作條件，利用實驗設計(Design of Experiment, DOE)，結合變異數分析(Analysis of Variance, ANOVA)和反應曲面法(Response Surface Methodology, RSM)二階模型，進行中央合成設計實驗(Central Composite Design, CCD)，並結合迴歸分析以加速確定操作條件之範圍，有效分析變因結果進行模擬，得到在進料壓力5.3 atm，抽真空壓力0.2 atm，進料溫度343.14 K，步驟5/10/15/20時間55秒下，得塔底產物純度99.999984%，回收率11.0525%，機械能耗2.33 GJ/tonne-CO2。
;In order to reduce carbon dioxide emissions that worsen our environment continuously, we could concentrate CO2 and let it become the high value-added product to improve it.
To validate the accuracy of PSA program, we verified the simulation with the experiment of 2-bed 6-step PSA process at first. Next, this study could be taken into 2 parts and both of them used UOP 13X zeolite as adorbent. The first part of study, a 3-bed 9-step pressure swing adsorption(PSA) process for flue gas after desulphurization and water removal (15% CO2, 85% N2) of subcritical coal-fired power plant was designed. After simulation, we obtained a bottom product CO2 purity at 89.94%, a recovery at 89.54% while at feed pressure 2.6 atm, vacuum pressure 0.05 atm, feed temperature 298.14 K, adsorption time 390 s, cocurrent time 40 s, vacuum time 300 s, and pressurization equilibrium time 50 s. Also, the calculation of energy consumption is important. The mechanical energy consumption was estimated to be 1.38 GJ/tonne-CO2.
In the second part of this study, based on the syngas gas emission rate of a 1 kW power plant, a scaled up 15 MW PSA process was designed to capture CO2 with over 99.9% high concentration CO2 product. Since the syngas of a gasifier after oxy-fuel combustion and dehydration produces 95% - 97.4% CO2, we used 95% CO2 and 5% N2 as our inlet gas. After simulation, we obtained a bottom product CO2 purity at 99.999944%, a recovery at 9.574%, a top product N2 purity at 98.44%, and a recovery at 94.09% while at feed pressure 5 atm, vacuum pressure 0.238 atm, feed temperature 338.14 K, bed diameter 131.678 cm, and bed length 407 cm. The mechanical energy consumption was estimated to be 2.53 GJ/tonne-CO2. At last, in order to find the optimal operating conditions, we combined the results of 15 MW PSA process with design and analysis of simulation experiments. After analysis, we obtained a bottom product CO2 purity at 99.999984%, a recovery at 11.0525% while at feed pressure 5.3 atm, vacuum pressure 0.2 atm, feed temperature 343.14 K, and step 5/10/15/20 time 55 s as the optimal results. The mechanical energy consumption was estimated to be 2.33 GJ/tonne-CO2. |
