應用高溫淨化技術提昇廢水污泥與沼渣共氣化產能效率及 重金屬去除之評估研究;Enhancement of energy conversion efficiency and heavy metals removal in co-gasification of wastewater sludge and anaerobic digestate using hot gas cleaning system

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Title:	應用高溫淨化技術提昇廢水污泥與沼渣共氣化產能效率及重金屬去除之評估研究;Enhancement of energy conversion efficiency and heavy metals removal in co-gasification of wastewater sludge and anaerobic digestate using hot gas cleaning system
Authors:	彭翊茹;Peng, Yi-Ju
Contributors:	環境工程研究所
Keywords:	廢水污泥;沼渣;氣化;高溫淨化系統;重金屬;Ｗastewater sludge;Anaerobic digestate;Gasfication;Hot gas cleaning system;Heavy metals
Date:	2024-08-19
Issue Date:	2024-10-09 17:28:53 (UTC+8)
Publisher:	國立中央大學
Abstract:	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.
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