利用焙燒程序將廢棄竹筷轉製固態生質燃料之研究

Abstract

本研究探討以孟宗竹為原料的廢棄竹筷(WBC)經由焙燒轉製成固體生質燃料(即焙燒後之WBC, WBCT)的可行性，並分析焙燒後的液體產物與氣體產物。焙燒之目標為使WBC經焙燒後的產物WBCT其質量產率(YM)能維持約70 wt.%且乾基高位熱值(high heating value in dry basis, HHD)能提高至5500 kcal kg-1以上。在管狀高溫爐內的合適焙燒條件為563 K焙燒溫度(Tr)及40分鐘的焙燒時間(tr)。經前述焙燒條件所得的固體產物WBCT，其質量產率YM為69 wt.%，乾基高位熱值HHD可由原本WBC之4615.86 kcal kg-1提升至5506.80 kcal kg-1，而其能量緻密因子(ED)也能提升至1.19。藉由前述合適條件焙燒所得的液體產物及氣體產物的組成探討，可得知液、氣產物的特性及可利用性。液體主要為水分佔總液體產物62 wt.%，其餘主要為酸性低碳數有機物，類似木醋液。由連續氣體偵測可看出氣體大量出現時間約在10到20分鐘之間。而氣體因高溫爐受空氣流入影響，主要產物為氧氣、二氧化碳及水氣，另有甲烷及一些非甲烷碳氫化合物。最終藉由固、液、氣分析，計算系統之氣體平衡(balance)及碳平衡，以瞭解未測到的物種所佔比例。由本論文結果可得知，廢棄竹筷經焙燒轉製竹筷固體生質燃料為一可行方法，不僅可解決過量廢棄竹筷的問題並提供較高熱質及品質之固體生質燃料。

Torrefaction of waste bamboo chopsticks (WBCs) for producing solid biofuel, i.e., torrefied WBC (WBCT), liquid, and gas products was investigated in this study. The goal was set to have WBCT retaining about 70 wt.% mass while raising the high heating value in dry basis (HHD) to around 5500 kcal kg-1 from original WBC. Proper torrefaction reaction temperature (Tr) and detention time (tr) were found at 563 K and 40 min for carrying out the torrefaction in a tubular furnace with carrier nitrogen. The comparison between WBC and WBCT were characterized by proximate, ultimate, and heating value analyses. The said proper conditions gave mass yield (YM) of 69 wt.% of WBCT relative to original WBC. The HHD of WBC was enhanced from 4615.86 to 5506.80 kcal kg-1 while the energy densification factor (ED) increased to 1.19 of WBCT. The results thus deduce that torrefaction process is advantageous to upgrade WBC to high energy containing solid biofuel. The difference of properties between Moso bamboo and WBC were assessed. Although the upgraded WBCT is the primary demand of torrefaction, this study also explored whether some useful components would be formed in liquid and gas products. The liquid products compose of water as high as 62 wt.% along with some organic acids. Some medicine components were also found in liquid products with potential medicine applications. During torrefaction, the gaseous pollutants of CO, NOX, SO2, and CO2 were largely discharged from 10 to 20 min of detention time. O2, CO2, and H2O are the major compounds in the total gas products collected. Some combustible gases of C1 to C6 hydrocarbons were also produced. Moreover, carbon and gas volume balances were computed and evaluated.