| 摘要: | 生質沼氣平均成分為60~70%甲烷、30~40%二氧化碳、0~4000 ppm硫化氫及其他微量氣體等，然而甲烷與二氧化碳為溫室效應之主要氣體，其中，甲烷的全球暖化潛勢為二氧化碳之25倍，對於溫室效應的影響力不容小覷，而硫化氫易造成機器損壞及管線腐蝕。因此本研究目的為設計出可分離硫化氫、純化生質沼氣中甲烷至高純度供後續再生能源使用且同時回收二氧化碳將溫室氣體減量之生質沼氣分離程序，此程序可謂一舉數得。
本研究使用模擬程序以變壓吸附法(pressure swing adsorption, PSA)進行生質沼氣純化分離，依據文獻資料擇定以沸石13X做為吸附劑，比較三個廠牌生產之沸石13X於溫度298K下由等溫平衡吸附數據計算之平衡選擇性(equilibrium selectivity)後，選出最適合的吸附劑為COSMO沸石13X，隨後，本研究以模擬程序結合實驗設計(design of experiment, DOE)，找出以進料條件為台灣6,000頭豬隻每日產生之排泄物經厭氧發酵後所產生的氣體量與進料組成64.8%甲烷、34.8%二氧化碳及4,000 ppm硫化氫時之雙塔八步驟PSA程序之分離最適化操作條件，經分析後，最佳化程序可使塔頂甲烷輕產物純度達99.34%、回收率91.93%，塔底重產物二氧化碳純度為可達96.37%、回收率49.16%，純化每噸甲烷產物所需能耗為1.02 GJ，捕獲每噸二氧化碳所需能耗為1.35 GJ，甲烷每日產能可達841.7 kg。
;The average composition of biogas is 60~70% methane, 30~40% carbon dioxide, 0~4,000 ppm hydrogen sulfide, and other trace gases. However, methane and carbon dioxide are both greenhouse gases. Furthermore, the global warming potential of methane is 25 times more than that of carbon dioxide. Its influence on the greenhouse effect cannot be underestimated. Moreover, hydrogen sulfide is able to cause machine damage and pipeline corrosion easily. Therefore, the purpose of this study is to design a pressure swing adsorption separation process which can separate hydrogen sulfide, produce high-purity methane as the resources for renewable energy, and capture carbon dioxide to reduce greenhouse gas emission.
In this study, PSA simulation program was applied to separate biogas. The adsorbent is chosen based on literature, and the sorbent parameter calculated from experimental data of the adsorption equilibrium curve. The simulation process combined with the design of experiments is used to find out the optimal operating conditions for the separation of the three-component feed which contained CH4/CO2/H2S. To find the optimal operating conditions, the central composite design was conducted. Considering the biogas produced from the anaerobic fermentation of the excrement of 6,000 pigs per day, with the composition of 64.8% methane, 34.8% carbon dioxide, and 4,000 ppm hydrogen sulfide as the feed conditions. After analysis, the optimal operating conditions were obtained to produce a top product at 99.34% CH4 purity with 91.93 % recovery, and a bottom product at 96.37% CO2 purity with 49.16% recovery. The mechanical energy consumption was estimated to be 1.02 GJ/t-CH4 and 1.35 GJ/t-CO2. The methane production is 841.7 kg per day. |
