焚化處理可達到減量之目的,且由於台灣生活型態具高人口密度、地形狹長以及高廢棄物成長率之特徵,因此國內廢棄物以焚化為主要處理方式。根據統計2009年國內廢棄物之年產量已達6,286,601噸,其中焚化處理約佔廢棄物總量之96.91%。而焚化後所衍生之灰渣產量約為19.90%,其中飛灰佔了其中的22.34%,因此焚化灰渣的處理亦是另一個議題。目前灰渣之再利用率可達52%,其中底渣則是佔大部分;相較於底渣來說,飛灰則顯少用於再利用之用途上,其主要因素在於飛灰具高重金屬、可溶性鹽類和有機物質,所以一直以來被認定為有害事業廢棄物。因此若能有效去除其內部之危害物質,則可作為再利用之材料,同時亦可降低環境污染。 灰渣一般常用水洗的方法進行再利用處理,其主因在於程序簡便、成本低廉且亦可有效將內部有害物質溶出。目前國內外之灰渣水洗相關研究以批次處理為主,且其設定參數亦只考慮時間及固液比,並無連續式水洗法結合顆粒分選之研究。故本研究以連續式水洗結合顆粒分選技術進行焚化飛灰之處理,並將淋洗液及淋洗後飛灰進行特性分析及毒性分析,同時探討經處理後之飛灰粉體之再利用性。 由研究結果可知,以去離子水當水洗劑時,其重金屬的水洗效率偏低,且水洗後殘渣經TCLP試驗後之溶液依然判定為有害物質;而以冰醋酸為水洗液時,不論是Al、Si或重金屬皆可有效的溶出;以硝酸為水洗液時,其水洗效率可高達90%以上。水洗試驗後之垃圾焚化飛灰粉體不僅能有效的分選,其中還含有SiO2、CaAl2SiO8‧4H2O、CaSO4、CaCO3及不結晶的玻璃質成份。含鈣的萃取液若能適度的鹼化、過濾及通入CO2氣體後,將在水中的鈣有效的回收成氫氧化鈣及碳酸鈣,其回收率可達99.85%。
With the development of municipal construction, management and treatment of municipal solid waste (MSW) has became more importance in Taiwan, and now the incineration technique has become a major method to treat MSW. According to the statistical data of Taiwan EPA, it is about totally 6,286,601 tons per year of MSW, and near 97% of MSW were treated by incineration. There is about 19.90% of ash wastes generated form the MSW incineration plants, including 22.34% of fly ash. At present, reuse rate of ash wastes is 52%, but the most recycled ash is bottom ash. Comparing to bottom ash, the fly ash is more difficult for recycling. Fly ash has a high alkalinity, cytotoxicity, and contains various hazardous species such as heavy metals, soluble salts and organic pollutants. So it is indispensable as a threat surrounding. The application of water-washing method to reuse MSW incineration fly ash waste would be a feasible process to remove toxic materials. In recent years, many studies used water-washing to treat ash by batch treatment, and experiment parameter was only focused on leaching time and L/S rate. In this study, we designed and used a apparatus for washing fly ash combined with a continuous size classification to treatment. Then, we can collect leachate and the washed fly ash powders to analyze its characteristics、cytotoxicity and Escherchia coli. The results showed that the concentrations of alkaline-earth metals, Cl- and pH were reduced day by day. When we used DI water as the leachant, the heavy metal cannot be leached effectively. When we used acetic acid as the leachant, Al, Si or heavy metal can be leachated effectively. When we used nitric acid as the leachant, the yield has 90%. After water washing, treatment the washed fly ash powder of MSWI can be sort effectively, and the compositions are SiO2、CaAl2SiO8‧4H2O、CaSO4、CaCO3 and amorphous matters. The calcium ion in the leachatees can be recycled after input CO2 gas to form Ca(OH)2 and CaCO3, the yield has max value of 99.85%.
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