焚化飛灰與電弧爐集塵灰共熔轉換微晶玻璃材料之特性與結晶動力學研究

Characterization and Crystallization Kinetics of glass-ceramics prepared from a mixture of MSWI fly ash and EAF dust

朱天鈞(Tien-Chun Chu)

指導教授 ： 王鯤生

國立中央大學/工學院/環境工程研究所/碩士(2011年)

摘要

近年來都市垃圾焚化飛灰及電弧爐集塵灰為有害事業廢棄物之大宗，急待妥善處理與資源化。本研究係結合玻璃化/再結晶處理技術，選用都市垃圾焚化飛灰、電弧爐集塵灰及廢玻璃作為初始原料，分別進行調質熔融程序、控制結晶熱處理程序，以及非等溫模式的熱差分析(DTA)程序，評估熔渣玻璃的再結晶作用行為及反應動力參數，以探討調質灰渣處理轉換成微晶玻璃材料之可行性。研究結果顯示，當混合調質配比為(60wt.%)焚化飛灰-(20wt.%)廢玻璃-(20wt.%)電弧爐集塵灰時，熔渣玻璃已具適當的玻璃形成能力、化學耐久性及較高的再結晶趨勢。由預成核試驗結果得知，最大成核速率溫度發生在700°C，最佳的成核處理時間為30min；在較低晶體成長溫度(750-850°C)，主要結晶礦物相為鈣鋁黃長石(Gehlenite, Ca2Al2SiO7)和鈣鎂黃長石(Akermanite, Ca2MgSi2O7)固溶體，次要結晶礦物相則為透輝石和鈣鐵輝石固溶體(diopside–hedenbergite solid solutions-Ca(FeMg)Si2O6)，而當結晶溫度超過900°C 時，逐漸會有第三結晶礦物相鈣鉻榴石(Uvarovite, Ca3Cr2(SiO4)3)產生。結晶動力學分析結果，未預成核的調質熔渣玻璃，其結晶活化能為367.4-395.2 kJ/mol，Avrami constant=1.8；預成核的調質熔渣玻璃，其結晶活化能為199.8-214.6 kJ/mol，Avrami constant=1.5；兩者的結晶活化能差距甚大，證明本調質熔渣玻璃適用於二階段的成核-晶體成長之熱處理方法。微晶玻璃性能分析結果，較高的晶體長溫度(950-1000°C)，具有較優異的微結構特徵、重金屬溶出特性、化學耐久性以及機械性質，鹼骨材反應判斷也都皆落在無害區域內，可廣泛運用在建築結構或裝飾材料上，為具高度資源化價值之環保材料。

關鍵字

預成核 ； 焚化飛灰 ； 結晶動力學 ； 微晶玻璃 ； 再結晶 ； 玻璃化

並列摘要

Municipal incinerator fly ash (MSWI fly ash) and electeric arc furnace dust (EAF dust) account for the main of the industrial hazadours waste in the past decade. For environmental concerns, the safe treatment and recycling of such waste has been in great demand in the nation. This study explores the properties of glass-ceramic prepared by combined vitrification/recrystallization approach from a mixture of MSWI fly ash, EAF dust and waste glass cullet. The experimental procedures involving the modification of fly ash and controlled crystallization heat-treatments were performed to convert modified ash into useful glass-ceramic composites. The re-crystallization behavior and kinetics of a waste-derived glass-ceramic was evaluated under non-isothermal conditions using differential thermal analysis (DTA).
With respect to the modification of MSWI fly ash compositions, it was found that a relatively stable slag-derived glass with suitable glass-forming ability, chemical durability and higher the re-crystallization tendency could be obtained by mixing 60 wt.% MSWI fly ash, 20 wt.% EAF dust, and 20 wt.% waste glass cullet.
Pre-nucleation experimental results indicated that the temperature and time of maximum nucleation rate were 700 oC and 30 min, respectively. The crystallographic and microstructural analysis of the produced glass-ceramic that nucleated at 700 oC for 30 min and crystallized at 750-1000 oC for 1 h, revealed the presence of three major crystalline phases, melilite (gehlenite (Ca2Al2SiO7)-akermanite (Ca2MgSi2O7) solid solutions), augite (diopside–hedenbergite solid solutions, Ca(Mg,Fe)Si2O6) and uvarovite (Ca3Cr2(SiO4)3) together with an equiaxed grain morphology that was embedded in the glassy matrix. But third crystalline phase of uvarovite begins to appear at crystallization treatment temperature of above 900°C and the amount of augite and uvarovite increased with increasing crystallization temperature.
The activation energies (Ec) of the crystallization of the annealed and pre-nucleated glass samples, determined by modified Kissinger and Ozawa equations, were in the range of 367.4-395.2 and 199.8-214.6 kJ/mol, respectively, and the obtained Avrami constant (n) was 1.8 for the annealed glass and 1.5 for the pre-nucleated glass. These results verify that the difference between the Ec values of the annealed and pre-nucleated glasses is very significant, suggesting that mixed ash-based glass is suitable for use in the two-stage crystallization thermal-treatment in this study.
The best physical, microstructural, mechanical and chemical durability properties of the glass-ceramic were produced at 950-1000°C for 1 hour heat-treatment, making them suitable for use as construction and decoration materials.

並列關鍵字

Pre-nucleation ； Incinerator fly ash ； Crystallization kinetics ； Glass-ceramic ； Recrystallization ； Vitrification

參考文獻

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