冷卻方式對焚化底渣/氟化鈣污泥 共同熔融資材化之影響研究

Abstract

本研究利用熔融技術，將垃圾焚化底渣與氟化鈣污泥進行共同熔融處理，並將所得之氣冷熔渣作為取代水泥之攙料，探討氣冷熔渣之卜作嵐性質；同時將所得之氣冷熔渣過篩符合細骨材之級配要求，用以取代水泥砂漿中之細骨材，並與水冷熔渣相比較。本實驗總共分成三階段，第一階段為尋求焚化底渣與氟化鈣污泥共同熔融之最低溫度，第二階段為氣冷熔渣之基本性質分析，第三階段則是將熔渣粉體取代部分水泥之後，利用各種試驗，如抗壓試驗、MIP、SEM等試驗，探討其卜作嵐性質；同時製備氣冷及水冷熔渣取代細骨材，評估熔渣取代細骨材之合適性。 實驗結果顯示，當焚化底渣與氟化鈣污泥之配比為7：3時，鹽基度CaO/SiO2約為1.15，具有最低之熔流溫度1079℃，此配比經熔融氣冷降溫之後具有部份結晶質，成分為與C級飛灰接近之卜作嵐材料。將熔渣粉體依不同水泥取代率添加至水泥砂漿中，經由各項試驗結果顯示，氣冷熔渣粉體作為水泥攙料具有「綜效作用」(Synergic effect)，不但具有卜作嵐特性可使內部結構更緻密且因其具有較多結晶化排列結構，可使得抗壓強度提升，且在相同之水泥取代率條件下，並不亞於水冷熔渣作為水泥攙料之效益。利用氣冷熔渣取代細骨材，其表乾比重為2.98，吸水率為0.65，單位容積為1750kg/cm3，皆符合CNS之細骨材級配標準，取代至40%之水泥砂漿其抗壓強度仍持續上升，且強度皆大於水冷熔渣取代之水泥砂漿，相對的，水冷熔渣作為細骨材之最大抗壓強度時之取代率為30%，易言之，氣冷熔渣較水冷熔渣有更大之細骨材取代量，就廢棄物骨材化之應用而言，氣冷熔渣具有更高之市場競爭力，也更顯示熔渣冷卻方式對熔渣造成之影響，也應視為廢棄物資材化之重要指標。

The purpose of this research was to study the effect of co-melting slags produced from MSWI bottom ash and industrial calcium fluoride on pozzolanic reaction in cement-based composites, and to investigate the suitability of using slag as fine aggregate. The co-melting slag was air-cooled(AS) under room temperature, and then compared with water-cooled slag(WS). The experiments were divided into three stages：(1) Determine the lowest pouring temperature of co-melting ash and sludge at various proportions. (2) Analyze the physical and chemical characteristics of the air-cooled slag, such as chemical composition, TCLP, XRD patterns and strength activity index(SAI). (3) Incorporate the slag with the cement-based composites material as mineral admixtures to replace a fraction of the cement, and evaluate the influence of the replacement ratio on performance of the cement-based composites materials in terms of setting times, compressive strengths, (MIP), etc. Additionally, the effect of replacing fine sand in cement-based composites at various curing ages on compressive strengths and porosity were explored in order to evaluate the feasibility of replacing fine aggregate by slag. The experimental results showed that the lowest pouring temperature was 1079℃ when the co-melting ash and sludge were in the ratio of 7：3. The molten samples were cooled at room temperature and their properties were then examined. It was observed that the air-cooled slag was more crystalline than that of water-cooled slag, and its chemical composition was close to Class C fly ash. The test results of compressive strengths, degree of hydration, MIP and SEM indicated that the slag was a latent pozzlan and it could replace 3% to 20% cement in mortar. It was also demonstrated that the pulverized slag as mineral admixtures has the synergic effect. The air-cooled slag had not only pozzolanic activity but also crystalline structure, so it could cause higher compressive strength as compared with water-cooled slag. In addition to replacement of cement, the air-cooled slag could be used to replace the fine aggregates due to its physical properties complied with the CNS requirements. The compressive strength of the air-cooled slag was ascendant continuity with the replacement ratio of 40% and its strength was higher than that of the water-cooled slag. Corresponsively, the water-cooled slag could reach its highest strength with replacement ratio of 30%. Altogether, the air-cooled slag could be a more suitable replacement of the natural fine aggregate. As far as the waste reutilization was concerned, the air-cooled slag was more competitive regarding market mechanism. It also exhibited that the cooling conditions of the melting process could be employed as the indicator for selecting the target reutilization route.