| 摘要: | 本研究係利用焚化飛灰與四種不同工程性質之下水污泥灰依不同比例摻配，進行鹽基度調質以降低灰渣熔流溫度，並進行調質灰組成份與鹽基度對熔流溫度迴歸分析，以探討都市垃圾焚化飛灰與下水污泥灰共同熔融之操作條件對熔流溫度之影響。另外，為建立共熔熔渣之基本材料特性，亦探討熔渣取代部分水泥之卜作嵐反應行為，包括熔渣水泥漿體抗壓強度、水化產物種類，水化程度，微結構觀察等。 實驗結果顯示，調質灰之組成份CaO、SiO2、Al2O3量對於熔流溫度R2分別為0.91、0.75、0.74。另外，調質灰熔流溫度隨CaO量之提高而逐漸增加，但隨SiO2和Al2O3提高則有降低之趨勢。調質灰CaO、SiO2、Al2O3三成份對熔流溫度之多變數迴歸方程式為FT = 1189.6＋4.19 CaO－0.96 SiO2－4.33 Al2O3，R2為0.91。7種鹽基度對熔流溫度之R2介於0.84~0.91之間，鹽基度1具有簡單判定及高相關性之優點，其中又以鹽基度5相關性最佳。整體而言，鹽基度低於1以下熔流溫度較低，超越1~1.2之後熔流溫度明顯呈現上升之趨勢。 XRF分析顯示，各熔渣之主要成分為CaO、SiO2、Al2O3、P2O5，接近於高爐爐石與class C fly ash，屬於延遲水化膠結材料。熔渣卜作嵐活性佳，介於87.9~103.2%之間，重金屬溶出濃度相當低且符合法規標準值。 取代量10及20%熔渣水泥漿體，養護28天後強度發展趨勢較純水泥漿體快，且經90天水化後熔渣水泥漿體強度與純水泥漿體相當或超越之，其中又以NH熔渣水泥漿體強度較高，而JJ與BL強度發展相當。XRD和FTIR分析顯示，水化產物主要包括CH、C-S-H、Tobermorite、Hydroganet、Gismodine。NMR分析顯示，隨齡期發展C-S-H 結構的聚合程度逐漸提高，且齡期90天時水化程度與聚矽陰離子長度皆大於OPC漿體，顯示熔渣晚期卜作嵐反應有助於漿體矽酸鹽類之聚合。SEM觀察發現，隨卜作嵐反應持續進行，C-S-H 膠體形成緻密的網狀結構，並與其他水化產物C-A-H和C-A-S-H等交結在一起，進而增加漿體的緻密度並提升物理強度。 The melting of municipal solid waste (MSW) fly ash is currently being practiced for recycling purposes under the sustainable waste management policy. Due to increasing concerns regarding the energy-intensivity of the process, in practice the basicity of MSW fly ash has been modified by the addition of sewage sludge ash (SSA),which lowers the melting temperature. However, it is essential that engineers and operators have a better understanding of how the basicity of the starting mixture affects the pouring point and the characteristics of the slag product produced by the co-melting process. Thus this study investigates the effects of the basicity on the pouring point of the fly ash-SSA mixture by using four kinds of SSAs as modifiers, which were collected from several primary and secondary sewage treatment plants (STPs) and were produced by different processes and sludge conditioning alternatives.The effects on the co-melted slags were determined by studying the slag's pozzolanic activity and its reactivity as a pozzolans in the slag-blended-cement (SBC) pastes. The results indicate that the pouring point of the mixture increased with increasing basicity, within the range from 0.65-1.90. As defined by Murakami Basicity=(MgO+CaO+Fe2O3+K2O+Na2O)/(SiO2+Al2O3). The pouring point is affected by the contents of the mixtures (CaO, SiO2, Al2O3 and the flux). It is suggested that an increase in the CaO content tended to increase the pouring point; whereas an increase in the SiO2 and/or the Al2O3 contents reacted adversely. The mineral compositions of the co-melted slags were determined by XRF analysis. Results indicate that the main components of the composition, CaO, SiO2, Al2O3 and P2O5 were close to those of the blast furnace slag and the class C fly ash. The co-melted slags also showed a high pozzolanic activity ranging from 87.9-103.2%, so could be classified as latent hydraulic materials. In addition, TCLP testing for the targete heavy metals indicate that all the slag samples in this study met the US EPA's regulatory thresholds. The pozzolanic reactivity of slag is determined by the compressive strength development of the SBC pastes and the product of the calcium silicate hydrate (C-S-H) in the pastes. SBC pastes with a replacement of cement by up to 20% showed a compressive strength at 90 days similar to or surpassing that of ordinary portland cement (OPC) paste. In particular, the SSA from Neihu STP,which was characterized by a high CaO content, due to the conditioning of the sludge by lime, outperformed the OPC paste in terms of compressive strength development. On the other hand, calcium hydroxide (CH), C-S-H, tobermorite, hydroganet and gismodine were confirmed by the XRD techniques,to be the main hydration products in the SBC pastes. NMR analyses also indicate that the formation of C-S-H in the SBC pastes increased with age, so that the degree of hydration and the growing length of the C-S-H at 90 days outperformed that of the OPC paste, as indicated by pozzolanic reactions in the slag at a later age. The pozzolanic reactions were further confirmed by SEM observation. A dense network of C-S-H which interpenetrated other hydrates, such as calcium aluminate hydrate (C-A-H) and calcium aluminate silicate hydrate (C-A-S-H) formed as the pozzolanic reactions proceeded. From the results of this study concluded that the modification of basicity of MSW fly ash by the addition of SSA to lower the pouring point leading to a energy-efficient melting process is feasible, and the SBC which incorporated the co-melted slag has a comparable engineering performance to that at the OPC pastes. |
