飞灰熔融分离过程中重金属Cu的迁移分布规律

为研究危险固体废弃物飞灰中的重金属Cu在垃圾焚烧飞灰熔融分离过程中的迁移分布规律,采用重庆同兴垃圾焚烧发电厂产生的焚烧飞灰进行熔融分离实验, 以重金属Cu为研究对象,探讨熔融温度、熔融时间、碱度、熔池配比等因素对熔融过程中Cu的迁移分布规律的影响。结果表明, 熔融温度对Cu在熔融分离过程中的迁移分布影响最大,随着熔融温度的升高,重金属Cu在铁相中的分布呈现上升趋势,熔融时间、碱度和熔池配比的影响相对小一些。       

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.     

垃圾焚烧飞灰中二噁英污染控制技术研究进展

垃圾焚烧发电技术凭借多项优势正成为我国大多数城市处理垃圾的首要选择。而焚烧飞灰作为垃圾焚烧的副产物之一，由于富集重金属和二噁英(PCDD/Fs)等被划定为危险废物，规定在其最终处置前需要进行无害化处理。在垃圾焚烧飞灰无害化处理前，对其中的PCDD/Fs进行减量和降解是十分必要的。因此，本文对焚烧飞灰中PCDD/Fs的污染控制技术(包括源头控制、过程控制和末端控制)进行了综述，针对焚烧过程飞灰PCDD/Fs的高温气相反应和低温多相反应(从头合成、前体催化合成)，以及末端控制方法中的催化还原、热处理、光催化、机械化学处理和水热处理等技术的最新研究进展进行了介绍，并讨论了不同处理技术的特点、挑战和未来的发展方向，为焚烧飞灰中PCDD/Fs的污染控制技术发展提供参考。     

城市生活垃圾焚烧飞灰中重金属的固化/稳定化处理

城市生活垃圾焚烧飞灰已被明确规定为危险废物,其中含有的大量有毒重金属对自然环境和人类生存会造成严重危害.综述了目前常用的水泥固化、烧结固化、熔融固化、药剂稳定化四种固化/稳定化垃圾焚烧飞灰中有毒重金属的方法,对比分析了各项技术的优缺点;对城市生活垃圾焚烧飞灰中重金属固化/稳定化处理的发展前景进行了展望,指出资源化利用是未来发展的必然趋势.     

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.     

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.     

脲酶菌的筛选及其对垃圾焚烧飞灰的固化

焚烧是当前城市垃圾处置的重要方式,焚烧飞灰及其重金属却是威胁周围环境的一种污染源。为降低这种污染,从植物根际筛选获得高活性脲酶菌,并比较脲酶菌固化焚烧飞灰后的抗压强度、颗粒级配及重金属稳定化效果。结果表明:从丹参根际土壤内分离获得2株高效脲酶菌Bacillus aryabhattai UR-F51和Pseudomonas taiwanensis UR-121;将脲酶菌与飞灰按一定比例混合后固化,菌株UR-F51和UR-121使固化飞灰的抗压强度分别增加48.00%和27.00%,固化颗粒粒径增加10.00%～145.00%;飞灰中重金属(Cr、Ni、Cu、Cd、Hg和Pb)的固化率分别为15.27%～37.23%、41.49%～90.43%、37.17%～99.73%、42.86%～71.42%、20.00%～40.00%和47.06%～82.35%。脲酶菌可显著提升飞灰及其重金属的固化效果,菌株UR-F51的固化效果最好,为缓解城市生活垃圾焚烧飞灰污染提供一种新途径。     

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.     

地聚物对固化焚烧飞灰的研究

垃圾焚烧处理技术产生的飞灰浓缩了重金属等一些高毒性当量的危险成分, 如果处理不当会 产生二次污染, 因此焚烧飞灰被认为是危险废物, 必须进行特殊处理.论文对地聚物固化垃圾焚烧 飞灰的工艺及养护条件进行了实验研究, 以抗压强度和重金属浸出质量浓度为效果表征量, 研究了 地聚物固化飞灰的合成配方.结果表明:氧化物配比为m(Na2O)∶m(SiO2)=0 .30 , m(SiO2)∶m (Al2O3)=4 .7 时, 飞灰掺量为40 %的固化体在养护7 天后抗压强度能达到31 .25 MPa , 固化体中 Pb , Zn ,Cu 和Cr 的浸出质量浓度分别达到0 .183 8 , 0 .023 1 , 0 .008 1 , 0 .367 9 mg/L .     

飞灰熔融气相产物盐分布规律

生活垃圾焚烧飞灰（简称“飞灰”）熔融技术具有无害化彻底、减容比高、资源化程度深、环境风险小、节约土地资源等特点,工业化前景广阔,但飞灰熔融技术应用过程中产生的二次飞灰问题成为掣肘,二次飞灰量约占飞灰的20~30%。对飞灰熔融气相产物盐分布规律的掌握,有利于二次飞灰无害化和资源化利用技术开发,对飞灰熔融烟气净化设备设计和生产运行具有借鉴作用。本文选用江苏省某生活垃圾焚烧电厂产生的飞灰,考查其熔融过程中气相产物盐的组成及分布,利用自主研发的等离子体飞灰熔融中试系统进行飞灰高温熔融试验并对气相产物盐和熔渣进行收集分析。通过重量差减法、X射线荧光光谱仪、电化学法等测定飞灰熔融过程中气相产物盐及熔渣组成和产量,获得Na、K、Ca、Mg和Fe的气相迁移率。利用热力学模型模拟1000~1600 ℃（试验温度为1450℃左右）、不同气氛（不通气体、氮气气氛或空气气氛）、添加0~50%的辅料、飞灰含水率0~12%条件下,气相产物盐的组成及分布规律。模拟结果表明：飞灰熔融过程中气相产物盐主要以NaCl、(NaCl)2、KCl、(KCl)2、CaCl2、KCaCl3、KMgCl3、FeCl2等的形态存在,其分布规律受熔融温度影响较大,受熔融气氛、辅料添加量、飞灰含水率影响相对较小。空气气氛条件下,飞灰熔融气相产物盐中出现新产物Na2SO4。对比中试试验和热力学模型模拟结果,碱金属Na和K气相迁移率的模拟值与试验值吻合较好,碱土金属Ca、Mg和Fe气相迁移率的模拟值远小于试验值。建议利用气相产物盐的分布规律开发分盐或氯盐利用技术,实现二次飞灰的综合利用,改变二次飞灰以填埋为主的现状,彻底实现飞灰的无害化和资源化。     

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.     

The Cement Solidification of Municipal Solid Waste Incineration Fly Ash

The chemical composition, the content and the leachability of heavy metals in municipal solid waste incineration （ MSWI） fly ash were tested and analyzed. It is shown that the leachability of Pb and Cr exceeds the leaching toxicity standard, and so the MSWI fly ash is considered as hazardous waste and must be solidifled. The effect of solidifying the MSWI fly ash by cement was studied, and it is indicated that the heavy metals can be well immobilized if the mass fraction of the fly ash is appropriate. The heavy metals were immobilized within cement hydration products through either physical fixation, substhtaion, deposition or adsorption mechanisms.     

Effect of MSWI fly ash and incineration residues on cement performances

The activities of municipal solid waste incineration (MSWI) fly ash and incineration residues were studied contrastively, through the component analysis and the activity ratio tests. The mechanical properties, hydration mechanism and leaching toxicity of the hardened cement paste mixing with MSWI fly ash and incineration residues were investigated. The experimental results indicated that the active constituents (CaO+Al₂O₃+Fe₂O₃) in MSWI fly ash were higher than those in incineration residues. Therefore the activity ratio of MSWI fly ash was 43.58%, twice as much as that of incineration residues. Meanwhile, the hydration of cement was delayed by mixing with MSWI fly ash and incineration residues, which also reduced the cement strength markedly. By adding with exceeding 20% MSWI fly ash, the specimens expanded and microcracks appeared. The leaching toxicities of cement pasted mixed with MSWI fly ash and incineration residues were lower than the Chinese national standard. Accordingly the cement mixed by MSWI fly ash and incineration residues can be considered as the environment-friendly materials.     

Effect of MSWI Fly Ash and Incineration Residues on Cement Performances

The activities of municipal solid waste incineration (MSWI) fly ash and incineration residues were studied contrastively, through the component analysis and the activity ratio tests. The mechanical properties, hydration mechanism and leaching toxicity of the hardened cement paste mixing with MSWI fly ash and incineration residues were investigated. The experimental results indicated that the active constituents (CaO+Al2O3+Fe2O3) in MSWI fly ash were higher than those in incineration residues. Therefore the ...     

Characteristics of MSWI fly ash during vitrification

The vitrification characteristics of municipal solid waste incinerator (MSWI) fly ash were investigated. Effects of temperature on the binding efficiency of heavy metals, the change of chemical compositions and the weight loss of fly ash in the range of 800-1350 ℃ were studied. Toxicity Characteristic Leaching Procedure (TCLP) of the United States was used to analyze the leaching characteristics of heavy metals in fly ash and molten slag. Results indicate that chemical compositions, the weight loss of fly ash and the binding efficiency of heavy metals in fly ash have a tremendous change in the range of 1150-1260 ℃. The percentage of CaO, SiO2 and Al2O3 increases with the increasing temperature, whereas it is contrary for SO3, K2O, Na2O and Cl; especially when the temperature is 1260 ℃, the percentage of these four elements decreases sharply from 43.72% to 0.71%. The weight loss occurs obviously in the range of 1150-1260 ℃. Heavy metals of Pb and Cd are almost vaporized above 1000 ℃. Cr is not volatile and its binding efficiency can reach 100% below 1000 ℃. Results of TCLP indicate that the heavy metal content of molten slag is beyond stipulated limit values.     

Solidification/Adsorption of Heavy Metals by FA/FA-MSWI based Al-Substituted Tobermorite

Fly ash(FA) was utilized to hydrothermally synthesize FA based Al-substituted tobermorites, and was combined with raw materials of FA and municipal solid waste incineration fly ash(MSWI) to hydrothermally synthesize FA-MSWI based Al-substituted tobermorites. Then optimum samples named FA-T and FM-T were selected, correspondingly. Their intrinsic properties as well as their solidification/stabilization and adsorption of heavy metals were studied. The experimental results showed that the specific surface area of FA-T and FM-T was 28.259 m~2/g and 45.939 m~2/g, respectively. Their pore size distribution, particle size distribution, and median particle size were approximately the same. FA-T and FM-T both had great potential of solidification/stabilization heavy metal to dispose hazardous solid waste. Further, FA-T and FM-T also showed good adsorption efficiency for heavy metals Pb~(2+) and Cu~(2+) as adsorbent to treat waste water.     

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.