| 摘要: | 本研究利用固定床及流體化床系統熱裂解系統，評估廢車破碎殘餘物(Automobile Shredder Residue, ASR)轉換能源過程，產能效率及重金屬排放及分佈特性。此外，本研究為評估ASR分離純化之可能性，並嘗試以密度分離程序，探討液固比為5 L/kg、攪拌時間10分鐘以及靜置時間10分鐘之操作條件下，ASR主要物理組成(如硬質塑膠類、發泡塑膠類、紡織纖維類及皮革橡膠等)之分佈特性。
根據密度分離結果顯示，硬質塑膠主要密度範圍為1.00 g/cm3以下，約佔68.21%，主要種類包括聚乙烯及聚丙烯等塑膠；其次為密度範圍1.00~1.20 g/cm3，約佔21.82%，其中包括聚丙烯腈-苯乙烯-丁二烯樹脂、聚甲基丙烯酸甲酯、聚苯乙烯或尼龍等塑膠種類；而密度範圍1.20~1.35 g/cm3以及大於1.35 g/cm3則分別約佔6.61%及3.36%，分別以聚乙烯對苯二甲酸酯、聚甲醛塑膠以及聚氯乙烯為主。發泡塑膠類及紡織纖維類，則主要分佈在密度小於1.00 g/cm3之範圍，組成比例均達97%以上。至於皮革橡膠類之密度範圍分析結果顯示，小於1.00 g/cm3之比例約占18.45wt.%，主要之組成比例，平均分散於密度範圍1.00-1.20 g/cm3、1.20-1.35 g/cm3及大於1.35 g/cm3，分別約佔27.45%、26.43%以及27.67%。根據前述之分離結果，ASR中之重金屬、砂石、玻璃及PVC類之重質塑膠，均可有效達成分離純化之目的。
應用固定床及流體化床熱裂解反應系統，探討ASR與各物理組成轉換能源之結果顯示，應用固定床熱裂解反應系統，ASR各物理組成之產物，主要以生質油及生質碳為主，各約占22.49~55.97 %及29.44~57.14 %，其中生質油之熱值約介於8,200~11,200 kcal/kg。至於應用流體化床系統處理ASR，因其熱傳反應較佳，因此，ASR熱裂解之氣體產物較多，約佔20.06 %，而生質碳及生質油之產量降低，分別為36.66 %及34.27 %，其中生質油之熱值則介於9,300~10,300 kcal/kg。
根據重金屬之分佈特性分析結果可知，ASR中重金屬鎘，主要分佈於裂解油，分佈比例大於99%以上，其中流體化床熱裂解系統，由於其熱反應快速且爐內氣體擾流之故，少數比例之重金屬鎘分佈於氣相產物，僅約佔0.06%。重金屬鉻、銅、鉛及鋅，則主要分佈於生質碳，比例約達90%以上，至於裂解油及氣體產物分佈比例，則均低於5%，此係具有較高揮發溫度之重金屬，在熱裂解反應溫度500℃之條件下，揮發比例較少，致主要分佈於生質碳。ASR中氯及硫之分佈特性結果顯示，生質碳為氯及硫分佈之主要地點，其分佈比例分別約為79.58%及63.53%，而裂解油之比例約為17.68%及19.06%，至於氣體產物中之氯及硫分佈比例，則分別為2.75%及17.41%。另根據氣體產物之重金屬物種模擬分析，結果顯示於較低溫度範圍約300~500℃，均以固相產物之氯化重金屬及硫化重金屬形式存在，當溫度於500~800℃，則以氣相產物之氯化重金屬及硫化重金屬形式存在。整體而言，本研究初步之分析結果，已建立完成ASR基本特性、熱裂解技術評估能源轉換效率及重金屬排放特性，應可提供未來ASR轉換能源技術選擇及重金屬排放控制策略之重要參考依據。
關鍵字：熱裂解、廢車破碎殘餘物、分離純化、重金屬、分佈特性;This research aims to evaluate the energy conversion efficiency and heavy metal partitioning and emission characterization in pyrolysis of Automobile Shredder Residue (ASR) using fixed bed and fluidized bed gasifier. Meanwhile, the feasibility of separation and purification of ASR by density separation controlling at liquid to solid ratio (L/S) of 5 L/kg, stirring time of 10 minutes and standing time of 10 minutes was also discussed. The major components of ASR could be included plastic-rigid, plastic-foam, textile, leather and rubber.
According to the analysis results of density separation, the major density range of plastic-rigid was less than 1.00 g/cm3 with corresponding the weight percentage was approximately 68.21%. The light fractions of plastic-rigid were mainly composed of polyethylene and polypropylene. Approximately 21.82% of plastic-rigid was ranged between 1.00 g/cm3 and 1.20 g/cm3. The major components were including acrylonitrile butadiene styrene, polymethyl methacrylate, polystyrene or nylon. Approximately 6.61% and 3.36% of plastic-rigid were ranged between 1.20 g/cm3 and 1.35 g/cm3 or higher than 1.35 g/cm3, respectively. The polyethylene terephthalate, polyoxymethylene, and polyvinyl chloride were identified by separation and purification process. In the case of plastic-foam and textile separation, the major density range was less than 1.00 g/cm3 with corresponding the weight percentage was approximately 97% and above. However, the leather and rubber was only 18.45 wt% which the density was less than 1.00 g/cm3. The weight percentages of leather and rubber were relatively average in tested density ranges that of 27.45% (1.00-1.20 g/cm3), 26.43% (1.20-1.35 g/cm3), and 27.67% (higher than 1.35 g/cm3), respectively. Based on the density separation results, the heavy metals, gravels, glasses, and PVC plastic in ASR could achieve the objectives of separation and purification by the tested density separation process.
The experimental results indicated that the bio-char and bio-oil produced from ASR and their derived components in fixed bed gasifier were approximately 22.49~55.97% and 29.44~57.14%, respectively. Especially for bio-oil, its higher heating value (HHV) was ranged between 8,200 kcal/kg and 11,200 kcal/kg. Due to the good heat transfer characteristics of fluidized bed gaifier, the yield of pyrolysis gas was increased to 20.6% with corresponding the yield of bio-char and bio-oil decreased to 36.66 % and 34.27 %, respectively. However, the HHV of bio-oil was slightly increased from 9,300 kcal/kg to 10,300 kcal/kg.
The heavy metals partitioning characteristics results showed that cadmium in ASR was mainly partitioned in bio-oil using the fixed bed gasifier which it was approximately 99%. However, in the case of fluidized bed gasifier, the Cd partitioning characteristics of syngas was increased to 0.06% resulting in rapidly thermal reaction and gas turbulent in the fluidized bed gasifier. The heavy metals, such as chromium, copper, lead and zinc, were approximately 90% and above partitioned in bio-char. It implied that the above metals partitioning percentage was less 5% partitioned in bio-oil and gas, respectively. This is because the volatilization temperature of the above heavy metals was relatively high, the less amounts of the above metals will partition in the bio-char during ASR pyrolysis process operated at temperature 500℃. The analysis results of chlorine and sulfur partitioning characteristics in ASR pyrolysis showed that the speciation containing chlorine and sulfur were mainly distributed in bio-char which their partitioning percentages were 79.58% and 63.53%, respectively. Meanwhile, the Cl and S partitioning percentages of bio-oil were 17.68% and 19.06%, respectively. The heavy metals speciation of gaseous products was simulated by chemical equilibrium model. The simulation results indicated that heavy metals chloride and sulfide speciation was presented in solid phase during the lower pyrolysis temperature range of 300-500℃. However, the pyrolysis temperature increased to 800℃, heavy metals chloride and sulfide speciation was mainly partitioned in gaseous phase. In summary, the basic properties of ASR and its energy conversion by pyrolysis were conducted. Meanwhile, the tested heavy metals emission and partitioning characteristics were also well established during ASR pyrolysis process. Therefore, the results of this research could provide the good information for selection of pyrolysis technologies and control strategies of metals emission in the future.
Keywords: Pyrolysis, automobile shredder residue (ASR), separation and purification, heavy metal, partitioning characterization |
