麻瘋樹籽油渣之焙燒

Abstract

本研究利用焙燒程序處理麻瘋樹種籽搾油後油渣，以提升其燃料性能。生質廢棄物有水分含量高、熱值低以及運輸貯存上的問題，若透過熱處理程序，雖然有部份質量損失，但仍能保存大部份熱能，可達到熱值提升，以及能量密度增加，並且焙燒產物具疏水性之效果。 本研究先進行熱重分析(thermagravimetric analysis, TGA)，決定油渣與脫脂油渣較合適之焙燒溫度(Tr)，與決定焙燒時間(tr)。依TGA結果擇定以260、280、300 °C及時間10-60 min進行焙燒，觀察兩種樣本於各操作條件下之焙燒反應情形。實驗結果顯示油渣在260、280、300 °C能量密度提升之最高值分別為1.25、1.29、1.30，脫脂油渣則分別為1.28、1.37、1.39，兩者焙燒產物之平均乾基熱值(high heating value in dry basis, HHMD)在5,000-6,000 kcal kg-1。焙燒產物固定碳比例上升，顯示更具燃煤特性。結果經迴歸分析後可歸納出熱值與固定碳之間呈現高度相關性質。與台電燃煤採購標準(STP)作為比較，油渣及脫脂油渣之焙燒產物之含硫量、灰分含量均在STP標準D之規範值以內。本研究綜合各項產物特性分析以作為最適操作條件之評估，結果顯示Tr = 280 °C，tr = 40 min之焙燒產物濕基高位熱值(high heating value in wet basis, HHMW)為5,700 kcal kg-1，符合STP標準D (HHMW ≧ 5000 kcal kg-1)之規範。

Torrefaction is a thermal treatment used to enhance the properties of fuels. In this study, Jatropha curcas L. seed cake after mechanically expelling ectraction of oil (denoted as Jatropha pressed cake or JPC) and the de-oiled JPC after further solvent extraction of residual oil using n-hexane (symboled as JDPC), were examined for their torrefaction performances. The thermogravimetric analysis (TGA) were employed to elucidate the thermal decomposition behaviors of JPC and JDPC. Temperatures with acceptable mass loss of 5-10% of JPC in TGA were in the range of 260-310 °C, suggesting the further tests of the torrefaction at 260, 280 and 300 °C. The torrefaction temperature (Tr) and time (tr) play important roles on the production yield of bio-char. The tr employed were 10 to 60 min. During the torrefaction at a setting temperature Tr, the biomass further lost its mass. The characteristics of torrefied products were measured and assessed. Proper torrefaction conditions were elucidated, considering the balance of enhancing the energy density (ED) while retaining the yield (Ym). The results indicate that at Tr= 260, 280 and 300 °C, ED values of torrefaction products of JPC are 1.25, 1.29 and 1.30, while those of JDPC are 1.28 1.37 and 1.39, respectively. The high heating values per mass in dry basis (HHMD) for the cases using JPC and JDPC are about 5,000-6000 kcal kg-1. The fixed carbon content (MFC) increases after torrefaction, enhancing its coal-alike property. The MFC is highly and positively correlated with HHMD. Employing the appropriate conditions of Tr = 280 °C and tr = 40min, the torrefied products containing negligible sulfur, ash of 9.27 wt.% and HHMW of 5700 kcal kg-1 meet the D quality of coal standards of Taiwan Power Co. with sulfur < 1.1 wt.%, ash < 16 wt.% and HHMW >5000 kcal kg-1.