| 摘要: | 本研究主要探討下水污泥(Sewage sludge)與厭氧沼渣(Anaerobic digestate)共同氣化處理之可行性，實驗條件分別控制當量比(equivalence, ER)、氣化溫度(700 ~ 900°C)與摻混比例(1:1、2:1、3:1、1:2及1:3)等。同時根據產氣組成之變化，評估共同氣化反應過程之產能效率、產物分布特性，以及硫、氯污染物排放特性。
根據實驗室規模之流體化床試驗結果顯示，下水污泥及沼渣個別進行氣化反應，隨反應溫度由700°C增加至900℃時，其氫氣產生比例，分別由3.69 vol.%增加至19.05 vol.%，及3.11 vol.%增加至14.54 vol.%。在氣化反應穩定階段，下水污泥及沼渣產氣平均熱值，隨反應溫度由700°C增加至900℃時，分別從3.48MJ/Nm3增加至6.62 MJ/Nm3以及2.35MJ/Nm3增加至7.10 MJ/Nm3；冷燃氣效率則分別從16.32%增加至31.10%及11.87%增加至35.88%。根據能源轉換之結果，提高氣化溫度有助於Boudouard反應、水氣(Water-gas)反應及焦油裂解等吸熱反應作用進行。
下水污泥及沼渣共同氣化反應之試驗結果顯示，氣化反應溫度為900°C，隨著沼渣之摻混比例增加，產氣熱值呈現增加之趨勢，其中在下水污泥與沼渣比例為3:1之條件下，最大氫氣產率為19.07 vol%；當下水污泥與沼渣比例為1:3之條件下，最大產氣熱值為6.98 MJ/Nm3，且冷燃氣效率可達到最高34.60%。整體而言，控制不同沼渣與下水污泥之摻混比，總能源回收效率約介於30.25% ~ 47.28%。根據氣化產物之硫及氯分布特性結果可知，在氣化反應溫度900℃時，共同氣化之氣相產物中硫及氯之分布比例，皆高於80%以上，其中硫化氫之排放濃度分別為227.64 ppm(沼渣)、177.66 ppm(下水污泥)及201.2 ppm(下水污泥:沼渣1:3)，可見後續須規劃妥適之空氣污染控制技術予以收集去除。
整體而言，根據本研究成果已初步驗證下水污泥與沼渣，具有共同氣化處理之可行性，相關產氣熱值亦能提供未來氣化處理廠內之能源需求來源，達到能源自主供應之效果。透過本研究之試驗分析結果，可提供作為未來相關厭氧消化後之殘餘物，轉換能源應用技術及污染物排放控制之參考依據。
;This research investigates the evaluation of energy conversion, gasification products partitioning characteristics, and trace pollutants (e.g., sulfur and chlorine) in co-gasification of sewage sludge (SS) and anaerobic digestate (AD) using fluidized bed gasifier with controlling equivalence, temperature (700~900°C), blending ratio of 1:1, 2:1, 3:1, 1:2 and 1:3 at 900°C.
In the case of SS gasification, the hydrogen production was increased from 3.69 vol.% to 19.05 vol.% with the temperature rising from 700°C to 900°C. Meanwhile, hydrogen production increased from 3.11 vol.% to 14.54 vol.% in AD gasification. It implied that hydrogen production increased with an increase in temperature. The heating value of product gas was increased from 3.48 MJ/Nm3 to 6.62 MJ/Nm3 and 2.35 MJ/Nm3 to 7.10 MJ/Nm3, respectively. The cold gas efficiency (CGE) significantly increased from 16.32% to 31.10% and 11.87% to 35.88%, respectively. Based on the results of energy conversion efficiency, increasing the temperature will enhance the endothermic reactions such as the Boudouard reaction, water-gas reaction, and tar cracking.
In the case of SS and AD co-gasification with a temperature of 900°C, increasing the AD addition ratio could enhance the produced gas heating value. In the case of SS: AD = 3:1, the maximum hydrogen production was 19.07%. In the case of SS: AD = 1:3, the maximum gas heating value was 6.98 MJ/Nm3, and the CGE was 34.60%. The total energy recovery rate ranged between 30.25% and 47.28% in the co-gasification of SS and AD. According to the results of the sulfur and chlorine emission characteristics. In the case of SS and AD co-gasification, the sulfur and chlorine partitioning in the gas phase was above 80%. In the case of AD, SS, and SS: AD = 1:3, the concentration of hydrogen sulfide in the syngas were 227.64 ppm, 177.66 ppm, and 201.2 ppm, respectively. Air pollution control technologies must be planned to reduce the chloride and sulfide emissions in the syngas.
In summary, the experimental results verified that sewage sludge and anaerobic digestate could be used as co-gasification materials and feasibility of improving energy yields. Therefore, the results of this study could provide good information for energy conversion technologies′ selection of digestate after the anaerobic digestion process. |
