垃圾焚烧飞灰处置与资源化利用研究进展

随着生活垃圾焚烧处理方式的不断推广,焚烧飞灰的产生量也不断增加。按照我国固体废物分类方法,焚烧飞灰属于危险废物,必须进一步处置才能进入填埋场或资源化利用。本文分析了飞灰物理化学特性,论述了常规处置技术（水泥固化、化学药剂稳定化、酸溶剂提取和熔融固化等）存在的问题。将原始飞灰直接应用于水泥、混凝土或路基材料,飞灰中高含量的重金属和盐类会产生新的环境问题。飞灰水洗可以高效去除其中的可溶性盐类,水洗飞灰在焙烧后重金属的浸出浓度远低于原始飞灰烧结后的相应浓度,飞灰水洗-焙烧技术具有很好的应用前景。     

水洗及酸洗过程对焚烧飞灰中重金属浸出特性的影响

以上海江桥和老港两家垃圾焚烧厂飞灰为研究对象,基于固体废物浸出毒性的醋酸缓冲溶液浸出法(HJ/T300-2007),研究了水洗和酸洗过程对焚烧飞灰中Cr、Cu、Cd、Pb等重金属元素浸出特性的影响,并结合XRD、SEM和EDS分析了飞灰在水洗和酸洗过程中矿物相组成和颗粒形态的变化,探索其与重金属浸出特性的关系。结果表明,水洗灰(GWF)和酸洗灰(AWF)中重金属含量的变化取决于重金属向液相转移以及在固相中浓缩这两种不同机制的共同作用。Pb向液相转移的作用大于浓缩作用,而Cr、Cu和Cd则相反。同GPF (原灰)和GWF (水洗飞灰)相比,AWF (酸洗飞灰)中产生了新的针状晶体;由于浓缩作用,水洗飞灰中元素硅明显增加,酸洗飞灰中Cu、Cr、Cd等重金属含量明显增加,Pb含量变化不大。决定重金属元素浸出能力的关键因素是各种重金属元素在飞灰中的存在形式,而不是其在飞灰中的绝对含量。pH值对飞灰中重金属的浸出具有较大影响,GWF的浸出毒性弱,AWF的浸出毒性强。水洗对飞灰中重金属的浸出特性有减弱作用,而酸洗对飞灰中重金属的浸出特性有增强作用。对于上海江桥和老港焚烧厂飞灰,水洗能够降低其Cr的浸出特性,酸洗处理后,Cd和Pb的浸出毒性超过卫生填埋标准。     

垃圾焚烧飞灰中重金属的固化/稳定化处理实验研究

研究了城市生活垃圾焚烧-电灰的特性及飞灰中重金属的特性,对利用水泥作粘结剂进行飞灰固化/稳定化处理效果开展了系统的实验研究,分析了水泥固化/稳定化飞灰的工艺特点和最佳工艺参数,并讨论了粘结剂固化飞灰机理以及重金属浸出毒性,为进一步研究城市生活垃圾焚烧飞灰的无害化处理与利用提供了有重要价值的参考依据.     

垃圾焚烧飞灰热分离处理后灰渣的特性研究

本文研究了上海某垃圾焚烧厂飞灰热分离处理后灰渣的无害化特性:减容率、减重率和浸出特性.结果表明:热处理温度越高,飞灰的减重率和减容率就越大,飞灰的减重率的变化可以分为650～1 050℃时缓增和1 050～1 350℃时剧增两部分,减容过程主要发生在熔融温度在1 205～1 250℃,其中1 150～1 250℃就减容了58.4％.随热处理时间的延长,飞灰的减重率和减容率的增幅都不大,分别由20 min的11.3％增加到300 min的17.7％及20 min的6.90％增加到300 min的16.7％.相对于时间而言,温度是影响飞灰热分离的主要因素.各重金属的浸出浓度随热处理温度的升高和时间的延长大体上呈降低的趋势.除Cr外,经不同温度(≥650℃)和时间(≥20 min)热处理后,灰渣中重金属的浸出浓度均低于原灰,但都达到了国家危险废物浸出毒性鉴别标准要求.     

欧盟废物焚烧指令的研究与借鉴

为进一步完善我国废物焚烧标准体系,防控废物焚烧环境风险,本文对欧盟废物焚烧指令与我国焚烧标准体系进行了对比分析。欧盟废物焚烧指令分别对专用焚烧厂和协同焚烧厂从废物运输到处理处置全过程的污染物排放控制做出了相关规定,适用于危险废物和非危险废物的焚烧以及常规污染物和有毒污染物的控制。欧盟废物焚烧指令对不同规模的焚烧设施采用统一标准,以日均值和半小时均值为污染物排放限值,更客观、准确地评价了污染物排放对环境的影响。与欧盟废物焚烧指令相比,我国废物焚烧标准涉及废物联合利用处置的相关条文较少,内容不详,项目缺失。我国烟尘、HCl的排放限值均在欧盟标准限值6倍以上,SO2的排放限值是欧盟标准的4~8倍。除CO、NOx的排放限值外,其他污染物排放限值也明显高于欧盟标准限值。我国采用抽样监测方法,监测结果可能在日常排放值的95%置信区间外,不具备代表性。我国可借鉴欧盟废物焚烧指令的成果制定协同焚烧标准,并严格污染物排放限值,考虑采用日均值或半小时均值的评价方法,提高我国废物焚烧标准的精确性和可执行性。     

有机螯合剂对城市生活垃圾焚烧飞灰中重金属的稳定化试验研究

选取乙二胺四乙酸二钠(EDTA)和亚硫基二乙酸(TDGA)两种有机稳定剂药剂,研究其对焚烧飞灰重金属的稳定化效果。实验表明,焚烧飞灰浸取液中重金属浓度依次为:Zn (124. 2mg/L) Pb (27. 98mg/L) Cu(15. 29mg/L) Cd (7. 68mg/L) TCr (1. 16mg/L),重金属Pb、Cd、Cu超出标准;在用EDTA和TDGA处理的稳定化样品浸出液中Pb、Cd、Cu、TCr的浓度随着有机螯合剂投加量的增加而减小,并且TDGA的处理效果优于EDTA;在TDGA投加量相同,且浸取剂p H在3到9的范围内时,随着p H的升高,Pb、Zn、Cu、TCr的浸出浓度逐渐减小,其中p H升高对Cd的浸出浓度影响较小;若有机螯合剂溶液与飞灰搅拌均匀,液固比的增加对螯合反应没有产生影响。     

危险废物处置中心物化处理浅析

介绍了一套危险废物处置中心物化处理系统的工艺原理、工艺流程（废酸碱及重金属废液处理、废乳化液处理）,与国内类似企业物化工艺进行对比,分析了系统的优缺点。结合国内危险废物处置现状和运行管理经验,进行了优化完善,进一步提高系统的经济性和稳定可靠性,为同类企业提供参考和借鉴。     

医疗废物、危险废物集中焚烧处置工程建设技术要求发布

国家环保总局于2004年1月19日发布了《医疗废物集中焚烧处置工程建设技术要求》(试行)和《危险废物集中焚烧处置工程建设技术要求》(试行)。“要求”对医疗废物、危险废物集中焚烧处置工程建设技术术语做出了界定。“要求”对医疗废物产生量、特性分析及焚烧处理适用范围;医疗、危险废物焚烧厂总体设计;医疗、危险废物接收、分析鉴别、贮存、输送;医疗、危险废物焚烧处置系统;配套(公用)工程;环境保护与安全;工程施工及验收;运营管理等方面都做出了明确的规定。其中明确了医疗废物产生量的计算方法,规定了危险废物特性分析鉴别的内容。在医…     

垃圾焚烧飞灰处理技术研究进展

垃圾焚烧飞灰是公认的危险废物,其处理处置技术的研究已成为环境领域的热点。综述了垃圾焚烧飞灰处理领域国内外的研究现状和发展趋势,对垃圾焚烧飞灰无害化处理和资源化利用技术的研究提供了参考。     

水泥窑协同处置危险废物中典型污染物迁移转化规律研究

水泥窑协同处置危险废物过程产生一系列的含Cr、Pb、Cl的危险废物。在实验室中,通过掺加不同Cr、Pb和Cl元素含量的典型危险废物,模拟煅烧熟料,研究Cr、Pb和Cl在水泥熟料中的固化率。结果表明:不挥发性重金属Cr在熟料中的固化率在50%以上,并随着生料中Cr掺加量的增加而增加;难挥发性重金属Pb元素在熟料中的固化率范围为19.69%~22.57%,在生料中Pb元素增加后,固化率则呈先增加后下降的趋势;非金属Cl元素在熟料中的固化率范围为3.30%~5.87%。Cl元素在熟料中的固化率在10%以下,并随着Cl元素掺加量的增加,Cl在熟料中的固化率减小。最后,对比《固体废物生产水泥污染控制标准》(征求意见稿)中水泥产品中Cr和Pb元素含量限值(0.1mg/L,0.05 mg/L),实验结果表明Cr和Pb的浸出含量都在限值范围内,满足标准的要求。     

生活垃圾焚烧中重金属行为的研究进展

垃圾中的金属以氧化物、氮化物、碳化物及其它形态转移到焚烧产物如烟气、飞灰和底灰中，需严格控制焚烧过程中重金属的排放，故清楚了解金属在焚烧中的行为是很必要的。经研究发现，飞灰中重金属含量远远大于底灰中的含量，因此以垃圾焚烧飞灰中重金属的稳定化处理为目标，分析了目前国内外处理垃圾焚烧飞灰的方法和重金属在各种影响因素下的行为，并进行了比较，为飞灰的无害化和资源化处理提供参考。     

湿法预处理对垃圾焚烧飞灰中重金属的形态及风险影响研究

以某典型城市生活垃圾焚烧飞灰为研究对象,采用X射线荧光光谱仪（XRF）、X射线衍射仪（XRD）和电感耦合等离子体光谱仪（ICP）测定了焚烧飞灰的主要成分、矿物学组成和重金属含量,探讨了湿法预处理工艺对飞灰的化学组成、矿物学形态、化学形态及风险水平的影响.结果表明,飞灰的主要化学组成为O、Ca、Cl、Na、K等,占飞灰总质量的93.54％,其次含有0.04％ ～0.68％的Zn、Pb、Cu、Cr等微量重金属元素;经过湿法预处理,飞灰中可溶性氯盐具有较好的去除效果,且几乎所有重金属元素的不稳定形态（弱酸提取态和可还原态）比例都有一定程度的减少,有效降低了重金属的毒性、生物有效性及环境风险水平.本研究有助于降低焚烧飞灰的环境风险和探寻其资源化的有效途径.     

The leaching characteristics of selenium from coal fly ashes

The leaching characteristics of selenium from several bituminous and subbituminous coal fly ashes under different pH conditions were investigated using batch methods. Results indicated that pH had a significant effect on selenium leaching from bituminous coal ash. The minimum selenium leaching occurred in the pH range between 3 and 4, while the maximum selenium leaching occurred at pH 12. The release of selenium from subbituminous coal ashes was very low for the entire experimental pH range, possibly due to the high content of calcium which can form hydration or precipitation products as a sink for selenium. The adsorption results for different selenium species indicated that Se(VI) was hardly adsorbable on either bituminous coal ashes or subbituminous coal ashes at any pH. However, Se(IV) was highly adsorbed by bituminous coal ashes under acidic pH conditions and was mostly removed by subbituminous coal ashes across the entire pH range. This result suggests that the majority of selenium released from the tested fly ashes was Se(IV). A speciation-based model was developed to simulate the adsorption of Se(IV) on bituminous coal fly ash, and the pH-independent adsorption constants of HSeO3* and SeO3 2* were determined. The modeling approach is useful for understanding and predicting the release process of selenium from fly ash.     

Leaching characteristics of solid wastes from thermal power plants of western Turkey and comparison of toxicity methodologies

Use of lignite in power generation has led to increasing environmental problems associated not only with gaseous emissions, but also with the disposal of ash residues. In particular, use of low quality coals with high ash content results in huge quantities of both fly and bottom ashes to be disposed of. A main problem related to coal ash disposal is the heavy metal content of the residue. In this regard, experimental results of numerous studies indicate that toxic trace metals may leach when fly and bottom ashes are in contact with water. In this study, fly and bottom ash samples obtained from thermal power plants, namely Yenikoy, Kemerkoy and Yatagan, located at the southwestern coast of Turkey, were subjected to toxicity tests such as the extraction (EP) and toxicity characteristic leaching (TCLP) procedures of the US Environmental Protection Agency (USEPA) and the so-called 'Method A' extraction procedure of the American Society of Testing and Material (ASTM). The geochemical composition of ash samples showed variations depending on the coal burned in the plants. Furthermore, the EP, TCLP and ASTM toxicity tests showed variations such that the ash samples were classified as 'toxic waste' based on EP and TCLP results whereas they were classified as 'non-toxic' based on ASTM results, indicating test results are pH dependent. When the extraction results were compared with the chemical composition of water samples obtained in the vicinity of the thermal power plants, it was found that the results obtained using the ASTM procedure cannot be used to predict subsurface contamination whereas the EP and TCLP procedures can be used.     

Properties of several fly ash materials in relation to use as soil amendments

Fly ash samples from five power stations in Western Australia and Queensland, and two soils used for horticulture in Western Australia, were evaluated for a series of physical and chemical properties. Soils were comprised primarily of coarse sand-sized particles, whereas most of the fly ashes were primarily fine sand- and silt-sized particles. Hydraulic conductivities in the fly ashes were 105- to 248-fold slower than in the soils. The water-holding capacities of fly ashes at "field capacity" were three times higher than those of the soils. Extractable P in the fly ashes (except Tarong and Callide) were 20- to 88-fold higher than in the soils. The pH showed considerable variation among the different sources of fly ash, with samples from Muja being the most acidic (pH = 3.8; 1:5 in CaCl2 extract) and from Gladstone the most alkaline (pH = 9.9). The toxicity characteristic leaching procedure (TCLP) values indicate that the potential for release of trace elements from the fly ashes was well below regulatory levels. When applied at sufficient rates (e.g., to achieve 10% w/w in surface layers) to sandy soils, fly ash altered texture and increased water-holding capacity. Depending on the source of fly ash used, such amendments could also provide P and aid nutrient retention by increasing the phosphorus retention index (PRI) and/or cation exchange capacity (CEC). The considerable variability in physical and chemical properties among the fly ash samples evaluated in the present study supports the notion that field trials are essential to the future development of soil amendment strategies making use of any particular source of fly ash.     

A study of the extraction of vanadium and nickel in oil-fired fly ash

Annual production of oil-fired fly ash in Taiwan is approximately 43 000 tons, of this approximately 13 000 tons is electrostatically precipitated, the rest is cyclonically collected. Structurewise, both consist of porous unburned carbon, vanadium and nickel oxide, and water-soluble sulfate. Electrostatically precipitated fly ash contains large amounts of ammonium sulfate. If these ashes are not properly disposed of, they become environmental problems, such as dusting, leakage of acid liquids, and pollution with heavy metals. This paper discusses the experimental extraction of vanadium and nickel from oil-fired fly ash. The results indicated that leaching of oil-fired fly ash in 0.5 N of sulfuric acid led to an extraction of 65% vanadium, 60% nickel, and 42% iron, along with an increase in the concentration of sulfuric acid. When leached in 2 N sodium hydroxide solution, the extraction of vanadium was 80%, and the extraction of nickel was negligible. If leached in an ammonia water, the extraction of nickel increased, along with an increase in the concentration of ammonia in water. When leached with 4 N ammonia water, the extraction of nickel was 60%, the extraction of vanadium was less than that obtainable from leaching in sulfuric acid solution or in sodium hydroxide solution. If electrostatically precipitated fly ash was leached in a solution of 0.25 N ammonia water and 2 N ammonium sulfate, it would yield an extraction of 60% nickel and 8% vanadium—leading to a selective extraction of nickel. This study has established an extraction flowsheet in which fly ash was first leached in an ammoniacal solution containing ammonium sulfate to recover nickel. The leached residues were then leached in an alkaline solution to recover vanadium.     

Synthesis of calcium phosphate hydrogel from waste incineration fly ash and its application to fuel cell

Waste incineration fly ash was successfully recycled to calcium phosphate hydrogel, a type of fast proton conductor. The crystallized hydrogel from incineration fly ash had a lower electric conductivity and a lower crystallinity than that from calcium carbonate reagent. However, the difference in electric conductivity between these crystallized hydrogels decreases with temperature. This was due to the presence of potassium in the incineration fly ash. The fuel cell with a membrane electrode assembly (MEA) using the calcium phosphate hydrogel membrane prepared from incineration fly ash was observed to generate electricity. The performance of this fuel cell was almost equal to that of a mixture of K₂CO₃ and CaCO₃ reagents; further, the performance of the former was superior to the fuel cell with a perfluorosulfonic polymer membrane at temperatures greater than approximately 85 °C.     

The reuse of municipal solid waste incinerator fly ash slag as a cement substitute

The results of the treatment of fly ash from a municipal solid waste incinerator (MSWI) by melting are described, and the safety and the effectiveness of using the slag produced by this melting treatment are studied. The properties of the MSWI fly ash slag were analyzed, to evaluate the feasibility of its reuse as a substitute for part of the cement required in mortar preparation. This MSWI fly ash slag was found to be comprised mainly of SiO₂ and CaO, which can be substituted for up to 20% of the cement content in mortar, without sacrificing the quality of the resultant concrete. In fact, the concrete thus produced has greater compressive strength, 10% higher than that without the substitution. The setting time of the fresh mortar becomes lengthens as increasing amounts of cement are replaced; while the spread flow value increases with the increasing percentage of cement substitution. X-ray diffraction analysis reveals that when the W/C=0.38 and the curing AGE=28 days, the crystal patterns in the mortar samples, prepared with different amounts of cement having been replaced by MSWI fly ash slag are similar. According to the results of the toxic characteristic leaching procedure analysis, MSWI fly ash slag should be classified as general non-hazardous industrial waste, that meets the effluent standard. Therefore, the reuse of MSWI fly ash slag is feasible, and will not result in pollution due to the leaching of heavy metals.