焙燒稻稈與生質纖維研究

Torrefaction of Rice Straw and Biofiber

楊子儀(Tuz-Zi Yang)

指導教授 ： 張慶源

國立臺灣大學/工學院/環境工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.03302

摘要

不論從溫室效應、環境污染或是化石燃料短缺問題等觀點考量，再生能源的發展都為未來不可或缺的重要議題，其中應用的最為廣泛就屬生質能。然而一般生質物有高水分、高吸濕性、低熱值、低能量密度、低可磨性與生物可分解性等缺點，不適用於現有燃燒系統之應用。但若是生質物經過焙燒(torrefaction)處理，則可改善原有缺點，適用於現有供熱與發電設施使用，相當適合做為農業廢棄物轉製能源物質的預處理方式。
　　本研究計畫以焙燒技術處理稻稈農業廢棄物與都市生活廢棄物經蒸煮程序後的生質纖維，以280、300及320 °C與10, 20-60 min不等的焙燒溫度、時間，針對固體產物(生質燃料或生質炭)與氣體產物做一系列的分析。結果顯示生質纖維以280 °C焙燒超過20 min後，從高溫爐移出後若是接觸空氣，則有明顯的自燃現象，造成濕基高位熱值(high heating value in wet basis, HHMW)下降。即使焙燒亦不易使熱值提升至台灣電力公司購煤品質D (以下簡稱品質D)的標準(HHMW > 5000 kcal/kg)。例如生質纖維以280 °C焙燒60 min，其HHMW僅達4309 kcal/kg，因此生質纖維宜直接與煤混燒，不宜再經過焙燒程序。
　　稻稈以280 °C焙燒50 min，其HHMW = 5025 kcal/kg，可符合品質D的標準，是很適合稻稈焙燒的溫度。焙燒所需時間可由產氣量或是CO2濃度評估焙燒完成時機。當兩者出現鋒值後進入緩速下降期時，約為焙燒完成。稻稈的質量產率、乾基熱值與顆粒粒徑之間成高度正相關。因此在批次反應時，可以質量產率直接推估其熱值。在連續式反應時，可以顆粒粒徑估算質量產率與熱值。此評估方法可得知該條件是否已達到焙燒目標。研究結果亦顯示稻稈經過焙燒已經擁有接近煤炭的性質，具有取代部份煤炭的潛力。

關鍵字

稻稈 ； 生質纖維 ； 焙燒 ； 能量密度 ； 預測熱值

並列摘要

Because of the greenhouse effect, environmental pollution and shortage of fossil fuel, the development of renewable energies is an important issue for the future. The most widely used renewable energy is biomass energy. However, the biomass has encountered several limitations in energy generation, including high moisture, hydrophilicity, low heating value, low energy density and low grindability, while biodegradable. Torrefaction can assist biomass overcoming those disadvantages so as to be applicable to the existing heating and energy generation systems. Therefore, torrefaction is one of the suitable pretreatments for converting agricultural waste to energy.
　　In this study, rice straw and biofiber were torrefied at 280, 300 and 320 oC with the residence times from 10 to 60 min. The biofiber examined is the product from the autoclaving of municipal solid waste. Key propesties of solid product (biofuel or biochar) and gas products were analyzed. The results indicate that after torrefation, biofiber becomes spontaneously combustible, thus lowering the heating value. For example, at 280 °C with 60 min torrefaction time, the high heating value in wet basis (HHMW) of torrefied biofiber is about 4309 kcal/kg. Therefore, it is suitable to co-fire the biofiber with coal directly without torrefaction.
　　HHMW of rice straw of 5025 kcal/kg torrefied at 280 °C for 50 min meets the coal standarnds D (HHMW > 5000 kcal/kg) of Taiwan Power Co. Torrefaction is completed when gas production rate and CO2 concentration decrease slowly after peakvalues. The mass yield, heating vale and pellet diameter of rice straw exhibit highly positive correlation. Therefore, these formation can be used to fleetly check whether the operation has reached the goal of torrefaction. For example, in batch reactor, one can directly estimate the heating value of biochar from mass yield. In continuous reactor, the mass yield and heating value can be directly estimated by the pellet diameter of biochar. The results indicate that the biochar from rice straw has the potential to replace a part of coal for either direct firing or co-firing.

並列關鍵字

Rice straw ； biofiber ； torrefaction ； energy density ； predict heating value

參考文獻

25. 王彥棋，「應用蒸煮程序處理都市廢棄物及其生質物回收再利用之研究」，碩士論文，環境工程學研究所，臺灣大學 (2011)。

30. 陳威榮，「以微波誘發焙燒反應處理稻稈及狼尾草之研究」，碩士論文，環境工程學研究所，臺灣大學 (2011)。

2. Arias, B., C. Pevida, J. Fermoso, M. G. Plaza, F. Rubiera and J. J. Pis, "Influence of torrefaction on the grindability and reactivity of woody biomass." Fuel Processing Technology 89(2): 169-175 (2008).

3. Balat, M., H. Balat and C. Oz, "Progress in bioethanol processing." Progress in Energy and Combustion Science 34(5): 551-573 (2008).

4. Balat, M., M. Balat, E. Kirtay and H. Balat, "Main routes for the thermo-conversion of biomass into fuels and chemicals. Part 1: Pyrolysis systems." Energy Conversion and Management 50(12): 3147-3157 (2009).