混燒飛灰特性研究及再利用之可行性評估

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Title:	混燒飛灰特性研究及再利用之可行性評估
Authors:	徐佩璇;XU, PEI-XUAN
Contributors:	土木工程學系
Keywords:	廢棄物再利用燃料;混燒飛灰;高壓混凝土地磚;透水混凝土;waste recycling fuel;mixed-fired fly ash;high-pressure concrete floor tiles;permeable concrete
Date:	2021-10-25
Issue Date:	2021-12-07 15:15:30 (UTC+8)
Publisher:	國立中央大學
Abstract:	因應鍋爐減少燃燒煤碳之需求，產業鍋爐使用廢棄物再利用燃料作為鍋爐輔助燃料或生質物與煤混合燃燒逐漸成國際趨勢。本研究針對以鍋爐輔助燃料替代部分燃煤所產生之混燒飛灰，然國內尚未完整規範解決其堆積問題，因此探討其材料相關物理與化學基本性質，並評估混燒飛灰資源再利用之可行性。依合作鍋爐業者使用循環式及氣泡式流體化床鍋爐，廢棄物再利用燃料選用RDF-5、廢木材、SRF及紡織污泥，個別與煤混燒後，產生本研究針對四種混燒飛灰，分別為混燒RDF飛灰、混燒廢木材飛灰、混燒SRF飛灰以及混燒紡織污泥飛灰。化學成分分析顯示，四種混燒飛灰的化學組成差異甚大，其中，混燒RDF飛灰與混燒紡織污泥飛灰以氧化鈣含量最高，而混燒廢木材與SRF飛灰則以二氧化矽、三氧化二鋁含量為主；混燒飛灰之灼燒減量普遍偏高，其中三種混燒飛灰超過20%。細度方面，濕篩法試驗結果顯示，混燒飛灰之篩餘量介於89%至11%間，顯示各種混燒飛灰間細度差異甚大。以混燒飛灰取代20%水泥重量製成水泥飛灰砂漿，強度活性指數於7天時混燒廢木材飛灰與混燒SRF飛灰分別為83.6%與81.9%，顯示兩者具有作為輔助膠凝材料之潛力。因混燒紡織污泥飛灰之物理性質、化學性質及成分分析與水泥砂漿試驗較為穩定，將其主要作為混凝土添加料與輔助膠凝材料為後續再利用試驗。依據混燒飛灰之基本性質應用於製作高壓混凝土地磚以及透水混凝土配合設計。以混燒飛灰取代20%細粒料製作混凝土磚，於28天抗壓強度可達A級磚標準，可見混燒飛灰可適用於製作非結構用混凝土製品之原料。透水混凝土則是參考ACI 522R進行相關試驗，孔隙率介於18.1%至24.3%，混燒紡織污泥飛灰當作膠結材取代部分水泥20%或10%重量，混燒廢木材飛灰則是外添加取代部分水泥20%或10%重量，混燒紡織污泥飛灰之7天與28天抗壓強度皆高於設計強度176kgf/cm2，其中混燒廢木材飛灰0.35F20才有達到設計強度，以28天滲透係數評估透水性皆為0.01m/s。所得試驗結果，本研究材料之混燒飛灰，具有高燒失量或細度不足之不利特性，僅有少數混燒飛灰具備作為輔助膠凝材料再利用之可行性，同時，因混燒飛灰材料變異性質較大，故於再利用時須謹慎評估其混燒飛灰來源及材料特性是否符合工程需求。;In response to the demand of boilers to reduce coal combustion, the use of waste reuse fuels as boiler auxiliary fuel or biotear and coal combustion has gradually become an international trend.This study is aimed at substituting boiler auxiliary fuel for part of the co-fired fly ash produced by burning coal.However, the domestic has not yet fully standardized to solve the accumulation problem, so the basic physical and chemical properties of its materials have been explored and the feasibility of the reuse of co-fired fly ash resources has been evaluated. According to the cooperative boiler industry, the circulating and bubbling fluidized bed boilers are used, and the waste reuse fuels are RDF-5, waste wood, SRF and textile sludge. After individual co-firing with coal, this study is aimed at four types of co-firing ashes are mixed-fired RDF fly ash, mixed-fired waste wood fly ash, mixed-fired SRF fly ash, and mixed-fired textile sludge fly ash. The chemical composition analysis shows that the chemical composition of the four mixed-fired fly ash is very different, among them, mixed-fired of RDF fly ash and mixed-fired of textile sludge fly ash with the highest calcium oxide content, while mixed-fired of waste wood and SRF fly ash are mainly silica, aluminum trioxide content; The ignition loss of mixed-fired fly ash is generally high, of which three kinds of mixed-fired fly ash exceed 20%. In terms of fineness, the results of the wet sieve test show that the sieve margin of mixed-fired fly ash flying ash is between 89% and 11%, which shows that the fineness varies greatly between various mixed-fired fly ash. Mixed-fired fly ash instead of 20% cement weight made of cement fly ash mortar, strength activity index in 7 days mixed-fired of waste wood fly ash and mixed-fired of SRF fly ash are 83.6% and 81.9%, respectively, showing that the two have the potential as supplementary cementitious materials(SCM). Because the physical properties, chemical properties and composition analysis of the mixed-fired textile sludge fly ash are relatively stable with the cement mortar test, it is mainly used as a concrete additive and auxiliary cementing material for subsequent reuse tests.According to the basic properties of mixed-fired fly ash, it is applied to the design of high-pressure concrete floor tiles and permeable concrete mix design. To mixed-fired fly ash instead of 20% fine aggregate to make concrete bricks, in 28 days pressure strength up to A-class brick standards, it can be seen that mixed-fired fly ash can be applied to the production of nonstructural concrete products raw materials.Permeable concrete is reference ACI 522R for related tests, porosity between 18.1% to 24.3%, mixed-fired of textile sludge fly ash as cementitious material to replace part of the cement 20% or 10% weight, mixed-fired of waste wood fly ash is added to replace part of the cement 20% or 10% weight, mixed-fired of textile sludge fly ash 7 days and 28 days of pressure strength are higher than the design strength of 176kgf/cm2, the permeability coefficient for 28 days is 0.01m/s. In summary the results of the test, the mixed-fired fly ash of this research material,with high loss on ignition or fineness of adverse characteristics, only a few mixed-fired fly ash has the feasibility of reuse as an supplementary cementitious materials, at the same time, because of the large variation of the mixed-fired fly ash material, it is necessary to carefully assess whether the source and material characteristics of the mixed-fired fly ash meet the engineering needs.
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