Solidification of Municipal Solid Waste Incineration Fly Ash with Cement and Its Leaching Behaviors of Heavy Metals

The solidifying qffect of cement addition on municipal solid waste incineration fly ash ( MSWFA for short, collected from the gas exhaust system of MSW incinerator), the interaction of MSWFA with cement and water and the leaching of heavy metals from cement-solidified MSWFA are investigated. The main results show that : ( 1 ) when MSWFA is mixed with cement and water, 112 evolution, the formation and volume expansion of AFt will take place, the volume expansion can be reduced by ground rice husk ash addition ; (2) heavy metals do leach from cement-solidified MSWFA and at lower pH more leaching will occur; (3) compared with cement - so-lidified fly ash, the leachate of solidified MSWFA is with higher heavy metal contents ; (4) with the increment of cement addition leached heavy metals are decreased ; and (5) concentrations of Zn , Mn , Cu and Cd in all the leachates can meet the relevant Standards of Japan, but as the regulations for soil and groundwater protection of Japan are concerned, precautions against the leaching of Pb , Cl^- and Cr^6 and so on are needed.     

Utilization of municipal solid waste incineration fly ash in lightweight aggregates

Washing pre-treatment of municipal solid waste incineration (MSWI) fly ash blended with shale and sludge was utilized in the manufacture of light-weight aggregates and processed to form ceramic pellets. A formula uniform design was performed to arrange the mixture ratio of the materials. The optimal mixture ratio of the materials was determined by measuring the bulk density, granule strength, and 1 h water absorption of the pellets. It is shown that the optimal mixture ratios of materials, MSWI fly ash, shale, and sludge, are 23.16%, 62.58%, and 14.25% (mass fraction), respectively. The performance testing indicators of light-weight aggregates are obtained under the optimum mixture ratio: bulk density of 613 kg/m³, granule strength of 821N, and 1 h water absorption of 11.6%, meeting 700 grade light-aggregate of GB/T 17431.2—1998 standard. The results suggest that utilization of MSWI fly ash in light-weight aggregates is an effective method and a potential means to create much more values.     

Mechanism of high concentration phosphorus wastewater treated by municipal solid waste incineration fly ash

The mechanism of removing phosphate by MSWI （municipal solid waste incineration） fly ash was investigated by SEM （scanning electron microscopy） with EDS （energy dispersion spectrum）,XRD （X-ray diffraction）,FT-IR （Fourier transform infrared spectroscopy）,BET （specific surface area）,and BJH （pore size distribution）.The results indicate that the removal rate of phosphate （100 mg/L） in 50 mL phosphorus wastewater reaches at 99.9% as the dosage of MSWI fly ash being 0.9000 g under room temperature.The specific surface area of MSWI fly ash is less than 6.1 m2/g and the total pore volume is below 0.021 cm3/g,suggesting that the absorption capacity of calcite is too weak to play an important role in phosphate removal.SEM images show that drastic changes had taken place on its specific surface shape after reaction,and EDS tests indicate that some phosphate precipitates are formed and attached onto MSWI fly ash particles.Chemical precipitation is the main manner of phosphate removal and the main reaction is：3Ca2＋＋2 PO43-＋xH2O→Ca3（PO4）2↓·xH2O.Besides,XRD tests show that the composition of MSWI fly ash is complex,but CaSO4 is likely to be the main source of Ca2＋.The soluble heavy metals in MSWI fly ash are stabilized by phosphate.     

MSWI fly ash based novel solidification/stabilization matrices for heavy metals

The possibilities of MSWI fly ash as a major constituent of novel solidification/stabilization matrices for secure landfill were investigated by mixing MSWI fly ash with rich aluminum components, which was added as bauxite cement or metakaolinite instead, to form Friedel and Ettringite phases with high fixing capacities for heavy metals. The physical properties, heavy metals-fixing capacity, mineral phases and its vibration bands in the novel matrices were characterized by compressive strength, TCLP（toxic characteristic leaching procedure）, XRD （x-ray diffraction） , DTG （derivative thermogravimetry）, and FTIR （fourier transform infrared spectroscopy）, respectively. The Tessier＇s five-step sequential extraction procedure was used to analyze the fractions of chemical speciation for Pb, Cd and Zn ions. The experimental results indicate that Friedel-Ettringite based novel solidification/stabilization matrices can incorporate Pb, Cd and Zn ions effectively by physical encapsulation and chemical fixation, and it exhibits a great potential in co-landfill treatment of MSWI fly ash with some heavy metals-bearing hazardous wastes.     

垃圾焚烧飞灰熔融过程中重金属固化特性

为探索垃圾焚烧飞灰中重金属在熔融过程中的迁移特性,采用燃油式表面熔融炉,对杭州某生活垃圾焚烧厂的焚烧飞灰连续进行了6个多月日处理规模为500kg/d的熔融固化中试实验.采用X射线衍射仪、电感耦合等离子体质谱仪、X射线荧光光谱仪研究不同工艺参数(温度、添加剂、冷却方式)对飞灰中重金属固化率的影响.结果表明:随着温度的升高和添加剂比例的增大,重金属Cu、Zn的固化率显著提高,Pb、Cd和Cr则变化不明显;水冷却方式下,重金属固化率要略大于空气自然冷却.熔融过程中,烟气中常规污染物浓度和二噁英等污染物总毒性浓度均小于标准限值.     

Microstructures and thermal properties of municipal solid waste incineration fly ash

To analyze the feasibility of utilization of thermal technology in fly ash treatment, thermal properties and microstructures of municipal solid waste incineration (MSWI) fly ash were studied by measuring the chemical element composition, specific surface area, pore sizes, functional groups, TEM image, mineralogy and DSC-TG curves of raw and sintered fly ash specimens. The results show that MSWI fly ash particles mostly have irregular shapes and non-typical pore structure, and the supersonic treatment improves the pore structure; MSWI fly ash consists of such crystals as SiO₂, CaSO₄ and silica-aluminates, and some soluble salts like KCl and NaCl. During the sintering process, mineralogy changes largely and novel solid solutions are produced gradually with the rise of temperature. Therefore, the utilization of a proper thermal technology not only destructs those persistent organic toxicants but also stabilizes hazardous heavy metals in MSWI fly ash.     

焚烧飞灰熔融特性与熔渣利用技术研究进展

垃圾焚烧飞灰中含有高浸出浓度的Pb,Cd,Cu,Zn等重金属,属于危险废物。高温熔融技术可以有效地控制焚烧飞灰中的重金属污染物。从飞灰无害化和资源化2个角度介绍了熔融技术的研究进展,分析了熔融技术的优缺点,在综述国内外研究成果的基础上,为今后焚烧飞灰的热处理技术提出了研究方向。     

生活垃圾焚烧飞灰重金属特性分析

对国内四个不同的垃圾焚烧厂产生的飞灰进行物理及化学特性分析.四种飞灰在颗粒尺寸分布上有相似的规律,飞灰中重金属的质量分数分析结果表明采用纯垃圾焚烧的炉排炉飞灰中的质量分数高于掺煤混烧的流化床焚烧飞灰中的质量分数.随着飞灰颗粒尺寸的减小,飞灰中重金属的浓度呈现增加的趋势.飞灰的渗滤特性表明,飞灰中Ca质量分数越高,飞灰的酸中合能力越强,且重金属的渗出率受飞灰渗滤液的pH影响大,而在碱性渗滤条件下受飞灰中重金属质量分数的影响小.     

炉排垃圾焚烧飞灰二级逆流水洗特性

以炉排垃圾焚烧炉飞灰为研究对象,分析水洗液固比和时间对飞灰中氯盐溶出的影响,对二级逆流水洗工艺展开研究. 通过模拟飞灰的二级逆流水洗工艺,建立水洗所产生废液中的氯质量浓度、残渣中氯质量分数的理论计算模型. 结果表明,当水洗液固比为6 mL/g、水洗时间约为20 min时,氯盐溶出质量达到稳定;飞灰经一级、二级水洗后的质量损失分别约为32%、37%;在相同液固比下,与一级水洗相比,二级逆流水洗可以提升飞灰的脱氯效果,当水洗液固比为2~6 mL/g时,提升率可达15.40%~61.15%;模型所得的理论计算值与实验实测值相关性好、均方根误差小. 2种水洗工艺产生的水洗废液中COD、氨氮质量浓度和pH值均高于《污水排入城镇下水道水质标准》的规定,在被排入城市污水系统之前须经过进一步处理.     

差异含水率条件下飞灰及其螯合物的应力应变及环境特性

垃圾焚烧飞灰因极高的重金属含量而被认为是一种危险废弃物,但与火山灰成分的相似使该材料有着资源化利用的潜在价值。以飞灰及其螯合物为研究对象,探讨了含水率、养护条件等因素对材料应力应变及环境特性的影响。研究结果表明：飞灰螯合物重金属浸出浓度较低,并有着较强的吸水特性;飞灰及其螯合物强度早期随着养护时间的增长呈上升趋势,破坏应变随之减小,脆性不断增大;材料强度在中后期出现明显分化,飞灰（90%湿度养护）强度约为螯合飞灰的23.11倍。飞灰强度随含水率的增大而减小,可归结于孔隙水对压实能量的吸收和结构的影响;螯合飞灰强度均随养护时间和含水率增加而显著增大。     

城市生活垃圾焚烧渣工程特性试验研究

焚烧法减量效果显著,已成为生活垃圾的主要处理方法,然而城市生活垃圾焚烧会产生大量底渣,底渣如何处置利用是当前一个重要且亟待解决的难题。以武汉地区底渣为例,借助微观观测技术和室内测试试验,较为全面地分析武汉底渣的物理、化学及工程特性,与不同地区底渣特性进行对比,并进一步探讨武汉底渣在道路工程中作为路基填料、垃圾填埋场中用作防渗层的可行性。结果表明,底渣颗粒形状各异,表面光滑且有细小孔洞,是一种塑性较低、比重较高的级配不良砂性粗粒土;底渣重金属元素浸出浓度均未超过国家相关标准的规定限值;底渣的击实性与中细砂相似,有一定的压缩性,但其固结特性不明显;底渣的渗透系数略大于细砂,经掺和膨润土后可考虑用作垃圾填埋场防渗材料;底渣内摩擦角接近中细砂取值,同时还具有一定的黏聚力;在承载变形能力上,底渣的CBR测定值较高,满足路基工程材料对承载力的要求。     

垃圾焚烧飞灰制作碱激发砖的环境安全性评估

为探索垃圾焚烧飞灰的资源化利用,使用流化床焚烧炉产出的焚烧飞灰、燃煤飞灰及矿渣粉为主要原料,由氢氧化钠及硅酸钠调制为碱激发剂制备碱激发砖材.当焚烧飞灰最大添加比为40%时,其28 d的抗压强度达28.69 MPa,符合混凝土实心砖规范(GB/T21144—2007)要求.环境兼容性方面,28 d的垃圾焚烧飞灰碱激发砖材HJ/T 300浸出测试结果显示,重金属稳定于砖材中.长期pH相关联性浸出试验发现,砖材中重金属Ba的浸出量随pH的降低而增加;重金属Zn在pH小于7的环境下可检测到有浸出,而重金属Cd、Cr、Cu、Ni、Pb只有在pH为6以下的环境才会有浸出现象.桶槽扩散浸出试验结果显示,焚烧飞灰碱激发砖材环境稳定pH在11.0~11.5,且仅有微量重金属钡（Ba）及铬（Cr）出现释出现象,分析显示其浸出量为微量.     

Glass-ceramics made from arc-melting slag of waste incineration fly ash

Grate fly ash and fluidized bed fly ash mixed with glass cullet additive respectively were melted in the electronic arc-furnace. The product, arc-melting slag, was further treated by crushing, pressing and heat treatment in order to make the glass-ceramics. The crystallization behaviors of the produced glass-ceramics were examined by differential thermal analysis (DTA), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Results show that main crystalline phase of the glass-ceramics from grate fly ash is wollastonite (CaSiO₃) with small amount of diopside (Ca(Mg,Al)(Si,Al)₂O₆), and that from fluidized bed fly ash is diopside (Ca(Mg,Al)(Si,Al)₂O₆). It is found that the glass-ceramics sintered at 850 °C and 1 000 °C from grate fly ash and fluidized bed fly ash respectively have the optimal physical, mechanical and chemical characteristics. Glass-ceramics samples, produced from incinerator fly ash with desirable properties and the low leaching concentration of heavy metals, can be the substitute of nature materials such as marble, granite and porcelain tiles.     

医疗废物焚烧灰、渣对人体健康风险评价

针对医疗废物处置不当容易产生二次污染的的问题,指出焚烧法是目前最为可行的处置方法之一,但处置医疗废物产生的固体废弃物(飞灰、灰渣)若直接释放到环境中,仍可能存在潜在的环境风险与危害.通过浸出实验与模式预测相结合,研究飞灰与灰渣中重金属通过饮水途径对人体产生的健康风险值.铬在医疗飞灰和灰渣中个人年风险最大,分别达8.8865×10-5/a和8.2597×10-5/a,超过国际辐射防护委员会(ICR)推荐的最大可接受风险5.0×10-5/a.医疗废物焚烧处置后的飞灰、灰渣存在着健康风险隐患,应该对其按危险废物进行处置与环境管理.     

Influence of ultra-fine fly ash on hydration shrinkage of cement paste

1INTRODUCTION Hydrationshrinkageisalsoknownaschemicalshrinkage[1].Thesolidvolumeincreasesafterce menthydrating,buttheabsolutevolumeofcementwatersystemreduces.Usuallythetotalamountofvolumeshrinkageofcementwatersystemis7%9%[1,2].Withthedevelopmentofthetechno logyofcementandconcrete,concretewithhighstrengthandhighperformanceisthedevelopingtendencynow.However,nowadays,comparedwithordinaryconcrete,thehydrationshrinkageofhighperformancecementconcreteincreasesobvi ouslybecauseoftheaccelerationof…     

搅拌时间对粉煤灰水泥净浆流动性及早期抗压强度的影响

影响粉煤灰水泥净浆的流动性与早期抗压强度等问题一个重要原因就是拌合是否充分,搅拌时间是否合适。现有的相关规范中对于拌合时间的规定大都针对普通混凝土,随着高性能混凝土的发展,尤其是粉煤灰混凝土近几年来的广泛使用,导致现有的拌合时间规定无法满足粉煤灰混凝土均匀性的控制要求。为此,通过初步研究不同拌合时间对不同掺量的粉煤灰水泥净浆流动性及早期抗压强度的影响,最终确定合理的粉煤灰水泥净浆拌合时间,供进一步研究与工程应用参考。     

矿渣水泥中掺用大量粉煤灰的抗压强度特性

在矿渣水泥中大量掺用粉煤灰来生产水泥是一种新技术。这种复合水泥(代号P.O)由于参入了两种活性混合料,较单一混合料的水泥具有更好的使用效果,其性能一般受所用两种混合料的矿物成分、比表面积、掺量及配合比的影响。本文用矿渣水泥、粉煤灰、激发剂及填充料四种成分按一定比例配制复合水泥后,着重探讨了激发剂以及填充料对其抗压强度的影响。其结果表明,在矿渣水泥中大量掺用粉煤灰时,必须添加少量的激发剂,才能满足早期强度的技术性能,单独使用各种激发剂对早期强度的提高并没有显著的效果,各种激发剂之间存在最佳配合比。     

粉煤灰混合料的力学特性

以细磨粉煤灰、水泥和粉细沙为主要材料组成混合料,采用正交试验方法,研究胶沙比、灰胶比和龄期对混合料的抗压强度和抗拉强度等力学性能的影响.研究表明,灰胶比对混合料的抗拉强度有显著影响;其次是龄期和胶沙比,但二者影响不显著.各因素对粉煤灰混合料抗压强度的影响程度按自大到小的顺序依次为胶沙比、灰胶比和龄期,但均无显著影响.采用低胶沙比和灰胶比组合确定混合料的配合比,既可满足强度要求,又能达到经济性目的.     

复合浆体中粉煤灰和水泥水化反应程度的测定

采用盐酸选择溶解法测定粉煤灰的水化程度,再结合水化热法计算复合浆体中水泥的水化程度。试样结果表明,在水化早期粉煤灰仅作为惰性材料填充于复合浆体的孔隙中。随着粉煤灰掺量的增大,水泥的水化程度越高,单位体积中水化产物的总体数量仍为减少。     

利用热等离子体熔融垃圾焚烧飞灰

为了评价垃圾焚烧飞灰的热等离子体熔融处理效果, 研究SiO2和CaO对重金属固化效果和重金属毒性浸出特性的影响. 在飞灰中添加一定比例的SiO2和CaO, 配置成不同的配灰样品, 利用纯氩热等离子体在1 400～1 500 ℃下, 对飞灰及配灰进行熔融玻璃化的实验研究, 分别利用X射线能量色散谱仪(EDX)、场发射扫描电子显微镜(FSEM)、X射线衍射仪(XRD)和毒性浸出方法(TCLP)分析飞灰和熔渣的化学组成、微观结构、晶相组成和重金属毒性浸出特性. 结果表明, 热等离子体熔融所得熔渣为无定形的玻璃体, 重金属浸出质量浓度均远低于毒性标准. SiO2和CaO的添加都可以改善重金属固化效果, CaO比SiO2对Cu、Zn、Cd和Pb挥发的抑制效果更好. SiO2的添加可以改善熔渣中重金属的浸出特性, 而CaO的作用与之相反.