不同農業廢棄物之焙燒反應特性

生質物之焙燒(torrefaction)技術又可稱為溫和裂解技術，係一種主要用來改善生質物性質，而生質物透過焙燒反應可以改善其原本不利於後續能源轉換程序之特性，是生質物藉由熱轉換成生質能常見的方法，有利於後端的運用；一般而言，焙燒執行於無氧或氮氣環境下，且溫度介於200～300℃之間。而未經處理的生質物有高含水率、低熱值、能源密度較化石燃料低等缺點，故可經由焙燒處理以改善缺點、提高熱值，增加能源密度。本研究以能源化的角度，探討三種農業廢棄物（檳榔梗、椰殼、蔗渣）及一種常見生質物（麻竹）在經焙燒處理前、後的燃料特性改變，以瞭結生質物焙燒後熱化學性質，以提供做為燃料使用的數據。其實驗分成兩個部分，第一部分將檳榔梗、椰殼、蔗渣以及麻竹經由三種不同溫度(200、250、300℃) 或不同持溫反應時間（30、60分鐘）的焙燒反應，接著將反應後產生之產物的燃料特性分析，以了解其熱轉換後產生的變化；第二部分是藉由熱重分析儀（Thermogravimetric analysis,TGA），了解其改質後生質燃料燃燒時點火溫度與燃燼溫度的變化。研究結果發現，隨著溫度提高，固態產率會隨之下降，主要是因為溫度提高可提升生質物內部半纖維素、纖維素及木質素之熱降解反應，並增強去揮發分的效果，因此固態產率隨溫度提升而明顯下降，而溫度越高其產生的熱量越高以及可有效降低H及O元素，並提高C元素含量，降低O/C和H/C比，以增加生質物的燃料特性；另外，生質物焙燒反應後，熱值可明顯提高，根據強化因子的分析最高可提升至原料之1.6倍，此外反應溫度對於碳含量、熱值、能量產率的影響皆高於焙燒反應時間，並且隨著反應溫度及反應時間增加，碳含量皆有上升的趨勢，因此使熱值也有上升的趨勢。在熱重分析儀中得知經焙燒後的生質物燃燒時的特性變化，從實驗結果可以得知隨著焙燒溫度越高點燃溫度越高，這樣的結果證實焙燒，主要是因為溫度提高可升生質物內部半纖維素、纖維素及木質素之熱降解反應，並增強去揮發分的效果，而燃燼溫度也隨著點燃溫度上升，燃燼溫度的上升是可以使生燃料更完全燃燒，因此焙燒可增加產物品質一致性，經焙燒後生質物化學和物理性質十分相近，有利於生質燃料之應用。

關鍵字

焙燒；生質物；熱重分析；農業廢棄物；點燃與燃燼溫度

並列摘要

The torrefaction technique is also known as minorpyrolysis technology, which is mainly used to improvethe properties of the raw materials, and the bakingreaction of the biomass can improve their characteristicsthat are not conducive to the subsequent energyconversion program. The conversion of heat to biomass is a common methodod that is beneficial for back-end applications. In general, roasting is performed in an　oxygen-free or nitrogen atmosphere at the temperatures between 200 and 300。C. Whereas the undisposed raw material has the disadvantages of high moisturecontent, low thermal mass and low energy densitycompared with fossil fuel, the solid must be improved　through the distribution of burning place to improve theheat quality and increase the energy density. In this study, the changes of fuel properties of three agricultural wastes (Areca catechu, Coconut fiber, Bagasse) and a common biogenic material (Bamboo) will be discussed in the view of energy utilization when it is torrefied before and after,in order to know the thermochemical properties to provide data for use as fuel. The experiment is divided into two parts. In the first part, torrefaction of Betel nut , Coconut fiberl,Bagasse and Bamboo was carried out at three different temperatures (200, 250, 300。C) and two different holding time (30 and 60 minutes) . Characteristics of raw and torrefied biomass were studied. The second part is to understand the changes of ignition temperature and burnout temperature with thermogravimetric analysis (TGA) when the modified bio-fuel combustion was burned. The results show that the solid-state yield decreases as the temperature increases, mainly because the rise in temperature can rise the thermal degradation reaction of material hemicellulose, cellulose and lignin, and enhance the effect of volatile. Therefore,the higher the temperature is,the lower the solid-state yields will be. When temperature rises, heat generation will be higher, in terms of decreasiy H and O elemente and increasing C element O / C and H / C ratio will reduce, in orde to increase the biomass fuel properties. In addition, the heat values significantly increase after the biomass torrefantion reaction. According to the analysis of strengthening factors,it can be enhanced up to 1.6 times than the raw materials. In addition, the influence of reaction temperature for carbon content, calorific value and energy yield are higher than torrefaction reaction time, and with the reaction temperature and reaction time increased, the carbon contents are both increased, and the heat value also has a rising trend. The thermogravimetric analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR) used to know the changes of burned biomass characteristics. From the experimental results, it can be seen that the higher the firing temperature is, the higher the ignition temperature is.The result confirms that torrefaction is mainly because the temperature rises can rise the material hemicellulose, cellulose and lignin thermal degradation reaction, and enhance the effect of volatile matter. Burnout temperature also increases with the ignition temperature,it helps burn more completely. Therefore, torrefaction can increase the consistency of the product quality, and after roasting, the biochemical and physical properties of the biocomposite are very similar, which is favorable to the application of the bio-fuel.