| 摘要: | 本研究利用實驗室規模流體化床氣化爐，探討廢水污泥(Wastewater Sludge, WS)及沼渣(Anaerobic Digestate, AD)共同氣化產能，以及應用高溫淨化系統(Hot gas cleaning system)評估提高產氣品質及去除重金屬之可行性。試驗條件主要包括氣化溫度700、800及900℃、當量比(Equivalence Ratio, ER)為0.3，摻混比例分別為WS:AD = 3:1、1:1及1:3。至於高溫淨化系統則分別填充沸石、煅燒白雲石及活性碳三種吸附劑。
研究結果顯示，廢水污泥氣化反應產氫組成比例，由氣化溫度700℃之1.40 vol.%增加至900℃之5.21 vol.%，其冷燃氣效率由8.96%增加至18.71%，平均產氣熱值則由1.79 MJ/Nm3增加至3.69 MJ/Nm3。而沼渣氣化試驗之產氣中氫氣組成比例，亦由700℃之3.07 vol.%增加至900℃之6.57 vol.%，合成氣之冷燃氣效率則由9.55%增加至16.27%，平均產氣熱值亦由2.04 MJ/Nm3增加至3.43 MJ/Nm3。依據上述研究結果可知，增加氣化溫度有助於促進水氣(Water-gas)、Boudouard反應及焦油裂解等吸熱反應，產生較多可燃氣體，進而提升產氣熱值。
廢水污泥及沼渣共同氣化反應試驗，結果顯示，在氣化溫度900℃條件下，合成氣之氫氣組成比例介於4.99~5.80 vol.%，其中以WS:AD = 1:3條件下，氫氣組成比例最高，就合成氣之平均產氣熱值而言，主要介於3.56~3.65 MJ/Nm3；而冷燃氣效率則介於16.96~17.46%之間。若考量共同氣化反應之平均產氣熱值而言，以摻混比例1:1之條件，有較佳之產氣熱值。
應用高溫淨化系統之氣化試驗結果顯示，合成氣之組成比例均有增加之趨勢，其中以沼渣氣化結果而言，合成氣之氫氣組成比例介於7.79~9.52 vol.%之間，較未使用高溫淨化系統之試驗結果為高。至於平均產氣熱值介於3.96~4.16 MJ/Nm3之間，亦是有增加之現象。根據氣化產物之重金屬分析可知，應用高溫淨化系統之試驗可去除部分氣相產物中之重金屬，其中銅(Cu)之去除率介於10.83~28.31%，鉻(Cr)之去除率介於19.77~40.10%，鋅(Zn)之去除率介於18.76~28.84%，鎵(Ga)之去除率介於54.80~70.85%，銦(In)之去除率介於30.76~49.57%。整體而言，廢水污泥及沼渣具有共同氣化產能應用之潛力，同時應用高溫淨化系統，可有效提升產氣品質及去除重金屬，本研究初步獲得之成果，可供後續工程應用之參考依據。
;This study investigates the co-gasification of wastewater sludge (WS) and anaerobic digestate (AD) using a laboratory-scale fluidized bed gasifier, focusing on enhancing gas production quality and assessing the feasibility of heavy metal removal via a hot gas cleaning system. The experiments were conducted at gasification temperatures of 700, 800 and 900℃, an equivalence ratio (ER) of 0.3, and blending ratios of WS to AD at 3:1, 1:1 and 1:3. The hot gas cleaning system was equipped with three adsorbents: zeolite, calcined dolomite and activated carbon.
For WS gasification, the study revealed a significant enhancement in hydrogen production, from 1.40 vol.% at 700℃ to 5.21 vol.% at 900℃, with a corresponding rise in cold gas efficiency (CGE) from 8.96% to 18.71%. The heating value of the product gas also saw a substantial improvement, from 1.79 MJ/Nm3 to 3.69 MJ/Nm3. In the case of AD gasification, a similar trend was observed, with hydrogen production increased from 3.07 vol.% at 700℃ to 6.57 vol.% at 900℃, and CGE rising from 9.55% to 16.27%. The heating value of the product gas also saw a significant increase, from 2.04 MJ/Nm3 to 3.43 MJ/Nm3. These results, underscore the efficiency of the gasification process, with higher gasification temperatures favoring endothermic reactions and leading to more combustible gas production and a higher heating value of the produced gas. During the co-gasification of WS and AD at 900℃, hydrogen production ranged from 4.99 to 5.80 vol.%, with the highest yield observed at a WS:AD = 1:3. The heating value of the product gas varied between 3.56 and 3.65 MJ/Nm3; while CGE ranged from 16.96 to 17.46%. A blending ratio of 1:1 was found to optimize the heating value of the product gas.
The gasification tests incorporating the hot gas cleaning system revealed a notable increase in the syngas composition ratio. For AD gasification, the syngas′ hydrogen content surged to 7.79 and 9.52 vol.%, surpassing the results obtained without the hot gas cleaning system. The heating value of the product gas also saw a significant increase, ranging from 3.96 to 4.16 MJ/Nm³. Most importantly, the hot gas cleaning system played a pivotal role in effectively removing heavy metals from the gas phase products, with impressive removal rates of 10.83% to 28.31% for copper (Cu), 19.77% to 40.10% for chromium (Cr), 18.76% to 28.84% for zinc (Zn), 54.80% to 70.85% for gallium (Ga), and 30.76% to 49.57% for indium (In).
Overall, the study underscores the promising potential of WS and AD for co-gasification. The hot gas cleaning system emerges as a significant player, enhancing gas production quality and enabling the removal of heavy metals. These preliminary findings provide a beacon of hope for future engineering applications in the field of waste management and environmental engineering. |
