焚化飛灰微波燒結/融熔/玻璃化之研究

Sintering/Melting/Vitrification of the Municipal Solid Waste Incinerator Fly Ash by Microwave Process

周孫有(Sun-Yu Chou)

指導教授 ： 駱尚廉

國立臺灣大學/工學院/環境工程學研究所/博士(2011年)

https://doi.org/10.6342/NTU.2011.00464

摘要

本研究主要目的是要利用微波輻射研發一新的焚化飛灰(MSWI fly ash，MSWI：municipal solid waste incinerator)處理技術，以達到焚化飛灰中重金屬穩定化、無害化的目的。經過本研究長期實驗，成功地研發及驗證以微波燒結、熔融或玻璃化焚化飛灰的技衛，事實上只要能適當地控制微波的操作條件，任何固體物質皆可利用微波加熱，使之燒結、熔融或玻璃化。焚化飛灰會吸收微波並轉成熱能，因為其所含之C、Co2O3、CuO、Fe3O4、Fe2O3、MnO2、PbO、Al2O3、MgO等成分為微波吸收劑。任何物質(氣、液、固相)在微波場有電極化現象者，皆可利用微波加熱。
首批之微波燒結/熔融實驗之操作條件如下：每個批次實驗樣品為20 g 焚化飛灰，以SiO2、Al2O3陶瓷坩堝或SiC板為容器，並以去離子水將含水量調為75% (w水分/w飛灰)，使用微波頻率2.45 GHz ，功率600 W、微波照射時間10至50分鐘。實驗結果顯示，大部份的樣品可被燒結/熔融，所有被燒結/熔融後的飛灰其重金屬的毒性溶出程序(TCLP)溶出濃度遠低於法規標準。研究結果顯示，利用微波程序進行燒結焚化飛灰，可有效將安定其所含有之重金屬 (例如鉛、鋅及銅等)。本研究亦發現在大部份的樣品中，重金屬的安定效率隨微波照射時間的增加而增加，飛灰中有無鹽類存在與否也會加強微波程序對飛灰的燒結及安定化。在將燒結之焚化飛灰置室內大氣中的環境 0 ~ 30天，實驗結果也顯示此一期間內，燒結飛灰之毒性溶出程序(TCLP)鉛的溶出濃度仍低於法規標準(5mg/L)，其他重金屬亦低於法規標準，且無明顯毒性溶出增加之趨勢。
隨後在更新實驗設計中，將實廠焚化飛灰添加實廠銅污泥、火力發電廠煤灰、試葯級CaO、SiO2、Al2O3、高嶺土或粉狀活性碳混合後，以壓錠方式進行微波燒結/熔融/玻璃化處理，功率600 W、微波照射時間50分鐘，所獲得之燒結/熔融產品或熔渣，其重金屬溶出濃度低於法規標準，尤其是鉛的溶出濃度。鉛及銅等重金屬可匣限、穩定在玻璃-陶瓷物質、微晶材料或玻璃的網狀結構(Glassy network)、Silicate unit (SiO44–)n的長鏈玻璃結構中；焚化飛灰添加實廠銅污泥的抗壓強度實驗結果，發現可符合法規大於10 kgf/cm2的掩埋處置標準，焚化飛灰/實廠銅污泥FATD10 (15/1)樣品的抗壓強度高達222 kgf/cm2。而焚化飛灰/火力發電廠煤灰FC11微波熔融/玻璃化後，形成玻璃的網狀結構(Glassy network)，可將重金屬限制及穩定於無定形態玻璃網狀結構的熔渣中。
以壓錠的焚化飛灰進行微波燒結/熔融處理，功率500 ~ 800 W、微波照射時間1至50分鐘，隨著微波功率愈高，則(微波照射時間)處理時愈短，當微波功率增加至700及800 W時，4分鐘即可完成焚化飛灰微波燒結/熔融，而微波功率500W則需要10分鐘才能可完成焚化飛灰微波燒結/熔融。在實廠焚化飛灰添加試葯級CaO、SiO2、Al2O3、高嶺土壓錠微波處理實驗中，發現樣品燒結、熔融或玻璃化除與組成(配比)有關外，與樣品體積(質量)多寡亦有關係，在相同組成、微波功率及照射時間下，使用4顆錠(tablets)與10顆錠(tablets) 進行微波燒結/熔融處理時，4顆錠(tablets)的樣品大部份是不燒結/熔融，10顆錠(tablets)的樣品幾乎都燒結/熔融，僅FA/A及 FA/γ–A 的(1/1)及(2/1)不燒結，燒結之樣品經XRD分析，發現有鈣黄長石(gehlenite, Ca2Al2SiO7)、鈣鋁石(mayenite, Ca12Al14O33)、鈣長石(anorthite, CaAl2Si2O8•4H2O)、透長石(sanidine, (NaK)(Si3Al)O8)及鈣鋁榴石(grossular, Ca3Al2(SiO4)2(OH)4)等微晶材料。另焚化飛灰或固體物質以微波處理時，是否吸收微波或形成燒結、熔融或玻璃化與該物質組成有關，如能形成燒結、熔融或玻璃化體，則可有效匣限、穩定重金屬於玻璃-陶瓷物質、微晶材料或玻璃的網狀結構中，進入掩埋場最終處置時可減少對環境的衝擊及污染，如能大量製造出微晶或玻璃化材料產品，將可使焚化飛灰轉為資材化再利用。

關鍵字

微波 ； 焚化飛灰 ； 燒結/熔融/玻璃化 ； 重金屬 ； 熔渣 ； 電極化

並列摘要

The objective of research is to develop a new technology for the treatment of fly ash from municipal solid waste incineration (MSWI) by microwave. This study was successfully demonstrated and proven the sintering, melting and vitrifing of fly ash from MSW incineration by microwave energy. From the present study emerges that the microwave process applied to the tailored mixtures is a useful technique to valorize the fly ash. Actually, any solid materials can be heating or sintering, melting and vitrifing by microwave when a condition of suitable operating was served well. MSWI fly ash can absorb then heat itself. The composition of MSWI fly ash include C, Co2O3, CuO, Fe3O4, Fe2O3, MnO2, PbO, Al2O3, MgO, etc. Those materials are absorbers in the microwave field. Any materials (gas, liquid or solid phase) can utilize microwave to heat themselves when there are polarization phenomenon in the microwave field.
In those sintering/melting experiments, 20 g of fly ash samples were placed into a SiO2 ceramic crucible, an Al2O3 ceramic crucible, or a SiC plate, and the moisture content of the samples was adjusted to 75% (w/w) with deionized water. The experiments were conducted with microwave frequency of 2.45 GHz at 600 W for 10 to 50 minutes. All of the fly ash samples became sintered and the heavy metal concentrations in the leachates of sintered fly ash samples were smaller than the current regulatory limits in Taiwan. The results from that study showed that the microwave process can be utilized to sinter fly ash from MSW incineration to stabilize heavy metals (i.e., lead, zinc, and copper) contained in the fly ash samples. This study also found that the stabilization efficiency increased with an increase of processing time in most of the cases and the presence of salt in the fly ash could enhance the sintering and stabilization of fly ash. During the aging time of 0 ~ 30 days, negligible Pb in the sintered fly ash was leached out, and the leaching concentration was lower than the criterion.
In this study, a new modified process was served for the immobilization of heavy metals in MSWI fly ash/copper sludge, MSWI fly ash and washed fly ash/activated carbon, MSWI fly ash/coal ash, and MSWI fly ash/four different additives (Al2O3 powder, γ–Al2O3, SiO2, and Kaolin) by microwave heating. Fly ash with or without additives were formed into cylindrical tablets. MSWI fly ash tablets with or without additives were treated with microwave radiation for sintering, melting and vitrifing. The obtained sintered products or glassy materials show low metals’ ions releases with respect to the original ashes. From the thermal characterization it appears that the materials are also suitable for the obtainment of sintered products or glassy materials. Lead and copper metals were well restrained in the structure of glass–ceramics and the leaching concentration can meet the legal criteria. The hardness sintered products are higher compressive strength and meets the allowable limits (10 kgf/cm2) for landfill disposal in Taiwan. The compressive strength of FATD10 (15/1) reaches 222 kgf/cm2. The weight ratios of the fly ash/coal ash (1/1) can be vitrified (made glassy) by melting, and heavy metals in the fly ash can be immobilized in the amorphous to form highly stable glassy or slag.
The fly ash tablets could be sintered with a shorter radiation time and lower energy consumption when a larger microwave power was applied. From visual inspection, 10 tablets were completely sintered after 10 min of microwave radiation at 500 W. Under microwave radiation of 600 W and 700 W, the fly ash samples were sintered at 8 and 4 min, respectively. In addition, the volume of fly ash samples treated in a microwave reactor has a significant impact on the efficiency of microwave–assisted sintering. Four different additives (Al2O3 powder, γ–Al2O3, SiO2, and Kaolin) were used and evaluated for their effects on sintering. Glass–ceramics such as gehlenite (Ca2Al2SiO7), mayenite (Ca12Al14O33), anorthite (CaAl2Si2O8•4H2O), sanidine ((NaK)(Si3Al)O8), and grossular (Ca3Al2(SiO4)2(OH)4) were formed as fly ash samples were sintered by microwave radiation. Heavy metals were well restrained within the glass–ceramics and the sintered products. The TCLP leachate concentrations of these heavy metals can meet the regulatory limits for landfill disposal. An accurate selection and proper ratios of the used wastes allows producing glassy with suitable properties and suggests a possible way for MSWI fly ash re-utilization.

並列關鍵字

Microwave ； MSWI fly ash ； Heavy metals ； Sintering/melting/Vitrification ； Slag ； Polarization

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