- 學位論文
以高週波電漿及觸媒催化程序熱處理稻稈生質廢棄物之研究
Thermal Treatment of Biomass Waste of Rice Straw via the Combined Radio-frequency Plasma and Catalytic Process
摘要
現今全球的能源供需有八成以上仰賴化石燃料，其中石油就佔了三成以上。 但由於世界石油蘊藏量日益減少，且其燃燒後所排放之二氧化碳亦為造成地球溫室效應的主因之一。 也因此為了降低石油短缺所帶來之衝擊及減緩全球溫室效應，開發新的替代性及環保可再生能源將是21世紀人類的重要課題。 而合適的替代性能源，主要在其可提供無碳排放的能源及有大規模商業化的潛力，在眾多選擇中以生質能源在臺灣具有非常大的發展潛力。 生質物(Biomass)簡稱為生質，泛指由生物產生的有機物質。 而生質能(bioenergy)則是指將生質物利用各種轉換程序(氣化、熱解、直接燃燒、厭氣分解、及發酵等)進行能源轉換，並將轉換後之能源進行發電等其他用途。 生質物及有機廢棄物屬於生質能源之一部份，適當處理以回收能源及資源是趨近零廢棄全循環目標很重要的途徑。 稻米為臺灣地區之最大糧食來源，也因此每年會產生近140萬噸的稻桿廢棄物。 而其傳統處理方式為直接戶外露天燃燒和現地掩埋兩種，但這兩種方式均會對環境造成負擔。 傳統熱轉換程序受限於加熱方式而有加熱速率及質傳效率上的限制，因此本論文利用高週波電漿之高加熱速率及能產生高能量物種之特性來克服傳統熱轉換程序中常見的氣體產物量偏低且產物中常有焦油污染之缺點。 此外文獻中指出在生質物熱轉換過程中搭配合適的觸媒能促進生質物之轉換效率、減少焦油之生成及提升目標氣體(如氫氣和甲烷)之產量。 因此本論文研究重點即為以高週波電漿為新一代加熱源來建立高週波電漿熱裂解設備，並搭配K2CO3觸媒來提升稻稈之熱轉換效率及NiO/CaO-Al2O3觸媒及Fe2O3-Cr2O3觸媒來增加產氣中氫氣與甲烷之產量，以將稻稈生質廢棄物轉換為可使用之能源及資源。 本研究除了得到高週波電漿處理稻稈之最佳操作條件、不同供給電壓時之高週波電漿熱裂解動力模式、高週波電漿設備能量平衡等結果外。 最後更依據所得到之實驗結果來發展與一套高週波電漿多階段熱裂解稻稈流程以供作為未來實際應用與商業用設計之參考。
並列摘要
Bioenergy from biomass has a potential to provide a significant portion of the projected renewable energy provisions for the shortage of the oil. Among the available biomass wasrtes, rice straw is one of the favorable bioenergy sources, because it is the residue from the end use of the biomass products. The reutilization of rice straw not only saves the cost of disposal but also produces valuable bioenergy, achieving the goal of resources recovery and reuse. In Taiwan, rice is one of the principal foods and the total annual generation of rice straw is about 1.4 million tons. Transform of the biomass wastes into bioenergy can be efficiently achieved applying thermochemical methods such as pyrolysis and gasification. Two main disadvantages of the pyrolysis and gasification of biomass wastes for producing gases of medium calorific value via the traditional thermolysis technology are (1) the low gas yield, reducing the total energy value of gas and (2) the high content of tar in gas, causing the corroding problem of the gas collection equipment and increasing the need for the further treatment of the gas produced. Application of a novel heating method via the radio frequency (RF) plasma is one of the feasible choices for overcoming the disadvantages of thermolysis using traditional heating methods. The heating method using RF has many advantages such as high heating rate, short heating time to reach setting temperature, low heat loss and low residual tar. Hence, this novel method can overcome the problems encountered in the traditional pyrolysis of biomass. Low tar content in product obtained from RF plasma thermolysis also can be achieved because high energy species, such as electron, ion, atom and free radical, produced from RF plasma can enhance the decomposition of tar. According to the references, adding the suitable catalysts in the pyrolysis of biomass is helpful for improving the thermolysis of biomass, enhancing the decomposition of tar and modifying the gas products. In this study, the RF plasma thermolysis reactor was used for pyrolyzing the biomass waste of rice straw. The application of RF plasma combined with various catalysts of K2CO3, NiO/CaO-Al2O3 and Fe2O3-Cr2O3 was studied. The results indicate that the uses of the said three catalysts can improve the conversion of pyrolysis, yield of H2 and yield of CH4, respectively. The effects of some major system parameters on the performance of the pyrolysis of rice straw via RF plasma were studied and elucidated. The kinetic model employed to describe the pyrolytic conversion of rice straw at various loading powers agrees well with the experimental data. In addition, a multi-stage RF plasma treatment process for rice straw pyrolysis was presented and discussed. The data and information obtained are useful for the rational design and operation of pyrolysis of rice straw via RF plasma.