| 摘要: | 本研究利用固定床管狀爐(以下簡稱固定床)及旋轉窯反應系統(以下簡稱旋轉窯)，評估生質塑膠(Polylactic Acid, PLA)熱裂解轉換為能源之可行性，試驗分別控制固定床反應溫度500 ℃、旋轉窯溫度500~600 ℃及斜率0.027~0.045等條件下，探討不同系統及不同操作條件，對生質塑膠轉換能源效率與裂解油物種特性變化之影響。研究結果顯示，應用固定床熱裂解反應系統，產物主要為氣體及裂解油，各約佔72.91~79.52 wt%及16.74~18.62 wt%，其中裂解油之熱值為1,795~1,951 kcal/kg。旋轉窯系統之熱傳反應較佳，熱裂解PLA之氣體產物較多，約為79.85~94.99 wt%，而裂解油之產量則介於4.89~20.06 wt%，其中裂解油之熱值介於1,146~3,730 kcal/kg。
根據不同系統產生裂解油品之輕質油(light fraction)及重質油(heavy fraction)之分析結果顯示，旋轉窯系統之輕質油比例較高，其中固定床及旋轉窯系統產生之輕質油及重質油比例，分別為54~56%及44~46%，以及63.88~77.99%及22.01~36.12%。本研究嘗試以裂解油品之氧/碳比(O/C比)，作為裂解油老化發生潛勢之評估指標，其中固定床及旋轉窯產生之輕質油O/C比分別為0.78及0.81~1.71，重質油O/C比則分別為0.50及0.18~1.05，均在老化發生潛勢之範圍。然旋轉窯系統操作在斜率0.027之條件下，其重質油O/C比介於0.18~0.31，明顯具有改善重質油老化現象之發生潛勢。
根據裂解油之官能基分析結果顯示，僅在旋轉窯斜率0.027條件下，有增強C-H伸縮震動(2,853、2,926 cm-1)之趨勢，亦即含甲基之化合物含量增加，其餘裂解油之官能基則為C-H變形震動結構(1,830、1,450、1,460 cm-1)以及C-H彎曲震動結果(600-900 cm-1)等。根據裂解油之GC-MS分析結果顯示，固定床裂解油主要物種為丙交酯(Dilactide)佔80%以上，旋轉窯裂解油主要物種，除丙交酯(Dilactide)外，尚包括乳酸(Lactic acid)及二丙酮醇(Diacetone alcohol)等，可見使用旋轉窯裂解PLA，有助於回收乳酸(Lactic acid)等物質，提升液體產物之後續應用。
;This research aims to evaluate the energy conversion eifficiency in pyrolysis of Polylactic Acid (PLA) by using fixed bed and rotary kiln system with controlled the temperature 500 ℃ (fixed bed system), 500~600 ℃ (rotary kiln system), and kiln slope 0.027-0.045. The different systems and experimental conditions effects on the energy conversion efficiency of PLA, pyrolytic oil characteristics and speciation were also conducted. The experimental results indicated that the major pyrolytic products of PLA produced by fixed bed system were consisted of 72.91-79.52 wt% gas and 16.74-18.62 wt% oil, respectively. Meanwhile, the heating value of pyrolytic oil was ranged from 1,795 to1,951 kcal/kg. The gaseous product yield was increased and ranged from 79.85 to 94.99 wt% with corresponding the pyrolytics oil decreased and ranged between 4.89 and 20.06 wt% by rotary kiln system. The heating valus of pyrolytic oil was approximately 1,146-3,730 kcal/kg and slightly higher than that of oil produced by fixed bed. This is due to the good heat transfer performance occurred in rotary kiln system.
To compare the pyrolysis system effects on pyrolytic oil characteristics, the light fraction pyrolytic oil yield by rotary kiln system was significantly higher than that of produced from fixed bed system. The light and heavy fraction pyrolytic oil produced form fixed bed and rotary kiln system are 54-56% and 44-46%, 63.88-77.99% and 22.01-36.12%, respectively. The oxygen-to-carbon ratio (O/C ratio) of pyrolytic oil is a good index for predicting the aged potential. The O/C ratio of light and heavy fraction produced from fixed bed and rotary kiln system were 0.78 and 0.81-1.71, 0.5 and 0.18-1.05, respectively. Accordingly, the pyrolytic oils produced in this research have the aged potential during the storage and/or transportation stage. However, In the case of rotary kiln system and kiln slope 0.027, the O/C ratio was approximately ranged from 0.18 and 0.31 that it implied that pyrolytic oil aged potential could be effectively inhibited.
According to the analysis results of functional group in pyrolytic oil, in the case of kiln slope 0.027, C-H Stretch (2,853、2,926 cm-1) speciation has enhanced by PLA pyrolysis. It means that the content of methyl group was increased. The main species of pyrolytic oil produced from fixed bed and rotary kiln system is dilactide. However, lactic acid and diacetone alcohol were also identified by PLA pyrolysis using rotary kiln system. The results obtained from this research could provide important information for developing the application of recycled Lactic acid produced from PLA pyrolysis using rotary kiln system. |
