| 摘要: | 本研究利用不鏽鋼集塵灰、淨水污泥及機械工廠邊料鋁屑，配置成廢棄物鋁熱反應熔融劑，鋁熱反應為氧化還原反應，反應間產生高溫使三種原料共同熔融，生成熔渣與鐵鉻合金，淨水污泥內含有高濃度二氧化矽，藉由二氧化矽稀釋熱量延長反應時間幫助金屬錠與熔渣分離同時進行熔渣改質。 不鏽鋼集塵灰鋁熱處理最佳配比實驗，不鏽鋼集塵灰與鋁屑以重量百分比3.89:1(不鏽鋼集塵灰80克和鋁屑20.56克)混合時，有最大放熱溫度2102℃，產生鈣鋁石熔渣及鐵鉻合金，回收之熔渣毒性溶出皆符合法規標準；金屬錠部分，主要物種為鐵及鉻金屬，且鉻含量皆有達到不鏽鋼製程標準(>11%)，將所回收之金屬錠當作不鏽鋼原料，達到資源循環及處理有害事業廢棄物之雙重目的。 添加淨水污泥—熔渣改質實驗，上述最佳配比添加10-60%淨水污泥，藉由原料中含有高濃度的二氧化矽，幫助金屬錠與熔渣分離並改善熔渣品質，淨水污泥的有機質，反應間揮發至大氣，造成孔洞逐漸增加，吸水率也相較提高，產物熔渣為Ca2Al2SiO7，此物質具有質輕、堅固、孔隙率大與吸水性佳等特性；金屬錠由SEM-EDS分析並無氧原子存在，表示以元素形式存在金屬錠，且鐵、鉻含量合為81-89%，添加淨水污泥明顯增加鐵鉻濃度。 鋁屑與不鏽鋼集塵灰進行鋁熱反應之動力學分析，利用Kissinger及Arrhenius方程式，將最大波峰溫度Tp及升溫速率β，繪製ln(β/Tp^2)和1/Tp關係曲線圖，若配比所含氧化鐵與鋁以化學計量式之反應路徑進行反應，並忽略其餘雜質於加熱過程中因亂度變小造成擴散活化能變大之影響，依照定律其擴散為一種與時間相關的過程，分別與單位時間通過擴散界面原子量(擴散通量)及擴散係數有關，藉此計算出擴散活化能，求得之活化能為165 kJ/mole。 It is beneficial to recover Cr and Fe as Cr-Fe alloy from the electric arc furnace dust (EAFD) since the dust is abundant in Cr2O3 and Fe2O3. This study investigated a new recovery approach by taking the advantage of thermite reactions between metallic oxides(ie., chromium oxide and iron oxide) and aluminum powder (i.e., prepared from waste, parings and scrap, referred to as aluminum scrap, AS). Sludge from water treatment plant(referred to as WTS), with silicon dioxide (SiO2) as main constituent, was added as a glass-former to facilitate the separation of metal and slag and to improves the resultant quality of the slag. This study determined the appropriate mix ratio of aluminum to EAFD by experiments based on the stoichiometry of the assumed thermite reactants in the tested wastws and reaction paths. The highest reaction temperature developed reflected the mix of EAFD to aluminum scrap is optimum under the balanced effects of factors such as species, oxidized degree, reaction path, impurities, non-reactive oxides, aluminum stoichiometry, and heat loss from the reactor wall. The results show that a mix ratio of EAFD: AS=3.89:1 is optimum in this study. The alloy retrieved in this case consisted of 86.27%(w/w) Fe-Cr alloy (i.e., 71.77% Fe and 14.50% Cr)., which is to be used as ore iron for producing stainless steel. In the experiments with 10-40% (w/w) WTS added, the retrieved alloy consisting of Fe-Cr alloy, ranging from 89.27 to 86.77(w/w). The Fe content in the alloy ranged from74.77-75.83%(w/w) Fe, and 14.50-10.94%(w/w), showing that Fe concentration in retrieved alloy increased approximately from 72%(w/w) to 75%(w/w), with the increasing addition of WTS. The increased concentration of Fe in alloy indicates the separation of alloy from slag was enhanced with the addition of WTS. On the other hand, with the addition of WTS, the retrieved slag became porous, resulting in the increase of absorption, which is supposed to be contributed by the formation of Ca2Al2SiO7 slag. The reaction kinetics of aluminum- electric arc furnace dust system was analyzed by Kissinger equation: d[ln(β/Tp2)]/d[1/Tp]= -E/R. where β: dT / dt , heating rate(K/min) Tp: peak temperature(K) E: activation energy(KJ/mole) R: gas constant(8.314JK-1mole) Differental scanning calorimetric analysis was conducted at different Heating rates ranging from 5 to 20 K/min and peak temperature measured as 165 KJ/mole for Al-Fe2O3 system. The results of this work suggest that to recover Fe and Cr from EAFD and WTS using thermite reactions is a promising technology not only energy conservative but also recycling- beneficial. |
