垃圾焚烧飞灰浸出特性及固化试验的研究

垃圾焚烧飞灰残留有重金属元素和二恶英等物质而被认为是危险废物,必须对之进行稳定化处理.通过试验研究分析了国内首家自主开发成功的广东省东莞市某回转窑垃圾焚烧发电厂垃圾焚烧飞灰的化学成分及矿物组成,研究了飞灰的浸出毒性,考察了水泥固化焚烧飞灰的效果,并与熔融/玻璃固化进行了比较.研究表明,该焚烧飞灰中重金属Cd的浸出毒性严重超标,并且随pH值的减小而增大,水泥固化效果随龄期的增大而更加显著.熔融/玻璃固化的效果优于水泥固化,但其经济性有待提高.     

A pilot and field investigation on mobility of PCDDs/PCDFs in landfill site with municipal solid waste incineration residue

A field investigation by boring was carried out in a landfill site primarily with municipal solid waste incineration residue. From the collected core samples, vertical profiles of homologous content of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs) in the landfill layer were traced and the behavior of PCDDs/PCDFs was examined. In addition, a pilot-scale study was conducted on the PCDDs/PCDFs leached from incineration fly ash and the treated one using large landfill simulation columns (lysimeters) and the leaching behavior of PCDDs/PCDFs was examined. As a result, it was found that the coexistence of dissolved coloring constituents (DCCs), which might be composed of constituents like dissolved humic matters having strong affinity for hydrophobic organic pollutants, could enhance the leachability of PCDDs/PCDFs, thus contributing to the vertical movement and leaching behavior of PCDDs/PCDFs in the landfill layers of the incineration residue. Moreover, it is highly probable that DCCs derive from the unburned carbon in the bottom ash mixed and buried with the fly ash containing a high content of PCDDs/PCDFs.     

Polycyclic aromatic hydrocarbons in solid residues from waste incineration

Polycyclic aromatic hydrocarbons (PAH) levels in solid residues from clinical waste incineration were measured using HPLC with fluorescence detection. PAH mass emission rates and emission rates as a function of waste burned are also reported. For bottom ash, PAH levels and physical properties were found to be quite consistent. Levels of high molecular mass PAHs were comparable to levels previously reported in the literature when adjusted for differences in sample preparation techniques. However, levels of low molecular mass PAHs were considerably elevated in this study. Possible reasons for this finding include the composition of the waste, combustion conditions and methods of sample preparation. In contrast, no PAHs were found in fly ash, an unexpected finding which is probably attributable to matrix effects resulting from a surfeit of lime in the fly ash. Factors effecting the partitioning of PAHs and their environmental fate are also discussed.     

Chlorobenzenes removal from municipal solid waste incineration fly ash by surfactant-assisted column flotation

The organic contaminants in municipal solid waste incineration (MSWI) fly ash, including chlorinated aromatic compounds and polycyclic aromatic hydrocarbons, have high toxicity and a potential negative impact on the environment. An effective and low energy consumption technique to remove the organic contaminants from MSWI fly ash is required urgently. Organic contaminants, such as chlorobenzenes (CBzs), in MSWI fly ash are known to become enriched in the unburnt carbon (UC) fraction. It is proposed that removal of UC from fly ash will result in the effective removal of most organic micropollutants. In this research, we use a technique of surfactant-assisted column flotation to decontaminate MSWI fly ash by removal of the CBzs-enriched UC from MSWI fly ash. We find that 39.8% of CBzs can be removed from fresh MSWI fly ash with 61.7% UC removal efficiency, whereas only 33.2% of CBzs can be removed from weathered MSWI fly ash with a low UC removal efficiency of 33.7%. By adding a mixture of two kinds of surfactants: sorbitan mono-oleate and polyoxyethylene (20) sorbitan mono-oleate to the weathered fly ash, 47.0% of CBzs were removed at the hydrophile lipophile balance value of 13.5, while the UC removal efficiency increased to 49.0%. The results show that surfactants can enhance CBzs and UC removal efficiencies during the column flotation process. Higher CBzs and UC removal efficiencies can be expected by further optimizing the conditions of surfactant-assisted column flotation.     

Limitations of the toxicity characteristic leaching procedure for providing a conservative estimate of landfilled municipal solid waste incineration ash leaching

Limitations of the toxicity characteristic leaching procedure (TCLP) for simulating pollutant leaching from wastes disposed of in full-scale landfills are well understood in the waste management profession; the TCLP solution has a lower pH and greater organic acid content than typical landfill leachate. The TCLP serves its intended regulatory objective, however, as long as a conservative estimate of leaching is provided. Here, we examine TCLP’s ability to represent worst-case leaching conditions for monofilled municipal solid waste incineration (MSWI) ash. A critical examination of TCLP’s applicability to MSWI ash is especially relevant, as ash management at MSWI facilities often centers on passing TCLP, regardless of environmental risk posed by the ash or its recyclability. Multiple batch leaching tests were conducted on different MSWI ash streams: mixed ash, fly ash, and different size fractions of bottom ash. Batch-test results were compared with leachate simulating MSWI ash monofills. The TCLP did not consistently provide the most conservative estimate of leaching, supporting the need to consider alternative methodologies in future regulatory development.

Implications: This paper analyzes the existing hazardous waste regulatory testing requirement for municipal solid waste incinerator (MSWI) ash management to evaluate whether the TCLP serves its intended purpose in providing the most conservative estimate of landfilled MSWI ash. The results will serve as guidance and motivation for policy makers and the regulatory community to reevaluate the TCLP’s application for characterizing MSWI ash leaching in certain disposal scenarios and could promote consideration of alternative testing procedures based upon results of this study. This study serves to promote representative and accurate quantification of leaching risk from MSWI ash.     

Leaching characteristics of PCDDs/DFs and dioxin-like PCBs from landfills containing municipal solid waste and incineration residues

To investigate the leaching characteristic of persistent organic pollutants (POPs), such as non-ortho and mono-ortho substituted chlorobiphebyls (dioxin-like PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/DFs), in leachate from municipal solid waste (MSW) landfill sites containing incineration residues, raw leachate samples were collected twice from 12 selected MSW landfill sites. The samples were divided into their liquid and solid phases using GF/B (pore size 1.0 microm), and the concentrations of POPs then determined. The concentrations of PCDDs/DFs ranged from 0.65 to 5.88 pg-TEQ/l (average 2.86 pg-TEQ/l), and those of dioxin-like PCBs from 0.05 to 0.32 pg-TEQ/l (average 0.18 pg-TEQ/l). The major congeners of leached PCDDs/DFs and dioxin-like PCBs in liquid and solid phases were OCDD (about 60%), 2,3',4,4',5-PeCBs (about 30%), and 2,3,4,4',5-PeCBs (about 54%). The relationship between landfill age and the leaching concentration of PCDDs/DFs, and effects of dissolved organic carbon (DOC) on the leaching of PCDDs/DFs are also discussed. Finally, a leaching prediction model of PCDDs/DFs from MSW landfills has been suggested using parameters, such as hydrophobic neutral organic carbons, total dissolved solid, and the ratio of non-biodegradable wastes in landfill sites.     

Effect of thermal processing on the characteristics of incineration fly ash

This work investigated the possibilities of immobilizing incineration fly ash by applying different processing methods. Direct sintering of fly ash at 1050 degrees C produced material with increased resistance to leaching; however, the high content of halides prevented the achievement of appropriate strength. Fly ash melting and casting into metallic moulds resulted in the formation of glass with good chemical resistivity and mechanical properties, which were further improved by devitrification, and the formation of glass-ceramics. The most successful combination of strength and resistance to leaching was obtained by a process consisting of fly ash melting, by pouring the melt into water, then grinding, and sintering without additives at 850-950 degrees C. In this way, a material was produced that cannot only be landfilled as a stabilised and non-reactive waste in landfills for non-hazardous wastes, but can also be utilized as a valuable material for manufacturing useful products. This article provided valuable results for policy-makers in Slovenia, about the handling fly ash from incineration plants. Implications: Fly ash from an incineration plant was thermally treated using several processing routes. Ash-melting, by pouring the melt into water and sintering, produced glass-ceramics having an optimal combination of strength and resistance to leaching that can find applications as useful products. These results provide important data for policy makers in Slovenia regarding the building of incineration plants, and handling the solid-waste products, especially fly ash.     

Performance evaluation of intermediate cover soil barrier for removal of heavy metals in landfill leachate

This pilot-scale study evaluated the use of intermediate cover soil barriers for removing heavy metals in leachate generated from test cells for co-disposed fly ash from municipal solid waste incinerators, ash melting plants, and shredder residue. Cover soil barriers were mixtures of Andisol (volcanic ash soil), waste iron powder, (grinder dust waste from iron foundries), and slag fragments. The cover soil barriers were installed in the test cells' bottom layer. Sorption/desorption is an important process in cover soil bottom barrier for removal of heavy metals in landfill leachate. Salt concentrations such as those of Na, K, and Ca in leachate were extremely high (often greater than 30 gL(-1)) because of high salt content in fly ash from ash melting plants. Concentrations of all heavy metals (nickel, manganese, copper, zinc, lead, and cadmium) in test cell leachates with a cover soil barrier were lower than those of the test cell without a cover soil barrier and were mostly below the discharge limit, probably because of dilution caused by the amount of leachate and heavy metal removal by the cover soil barrier. The cover soil barriers' heavy metal removal efficiency was calculated. About 50% of copper, nickel, and manganese were removed. About 20% of the zinc and boron were removed, but lead and cadmium were removed only slightly. Based on results of calculation of the Langelier saturation index and analyses of core samples, the reactivity of the cover soil barrier apparently decreases because of calcium carbonate precipitation on the cover soil barriers' surfaces.     

垃圾焚烧飞灰综合利用研究进展

焚烧处理是解决日益增长生活垃圾的有效方法。垃圾焚烧产生的飞灰因含有大量的重金属等污染物而属危险废物 ,目前常采用的处理方法是填埋。本文就垃圾飞灰的综合利用研究现状进行了论述。从环境和技术的角度看 ,垃圾飞灰的预处理、水泥固化和玻璃化是目前飞灰综合利用的主要研究方向     

SGA对垃圾焚烧飞灰中重金属的固化性能研究

根据EPA1311、HJ／T299—2007、HJ／T300—2007和HJ557—2009等国内外不同标准,研究了深圳某垃圾焚烧发电厂垃圾焚烧飞灰的浸出毒性,探讨了六硫代胍基甲酸（sixthioguanidineacid,SGA）、二甲基二硫代氨基甲酸盐（sodiumdimethyldithiocarbamate,SDD）和Ca（OH）2浓度对垃圾焚烧飞灰中重金属的固定性能的影响。研究结果表明,随着浸提液pH的降低,该厂焚烧飞灰中大部分金属元素的浸出量增大,焚烧飞灰浸出液中的cd、Ni、Ph和zn浓度分别超过国家危险废物鉴别标准（GB5085．3—2007）规定值的4．75倍、1．47倍、6．72倍和2．20倍,属于危险废弃物,必须进行稳定化处理。当固化剂SGA加入量为0．1mol／kg时,稳定化后的重金属浸出浓度已经低于危险废物鉴别标准,且对Cd、Cr、Cu和Pb的固化性能优于SDD和Ca（OH）2;当固化剂SGA、SDD和Ca（OH）2加入量为0．5mol／kg时,稳定化后的焚烧飞灰重金属浸出浓度均低于国家危险废物鉴别标准（GB5085．3-2007）中的规定值。与SDD和Ca（OH）：相比,SGA对垃圾焚烧飞灰中重金属的固化处理更具有优势。     

Curbing dioxin emissions from municipal solid waste incineration in China: Re-thinking about management policies and practices

As one of the countries with large amounts of dioxin releases, the control of dioxins is a major challenge for China. Municipal solid waste (MSW) incineration should be considered a high priority source of dioxin emissions because it is playing an increasingly more important role in waste management. MSW incineration in China has much higher emission rates of dioxins than in the developed countries, partially resulting from the gaps in the technologies of incineration and flue gas cleaning. Moreover, the current management policies and practices also contribute significantly to the problem. We recommend lowering dioxin emission standard, strengthening fly ash management, and improving regulation enforcement to reduce dioxin releases into the environment from MSW incineration. We also propose that alternative strategies should be considered on dioxin control and call for an expansion of economic instruments in waste management to reduce waste generation and thus the need for incineration.     

SGA对垃圾焚烧飞灰中重金属的固化性能研究简

根据EPA 1311、HJ/T 299-2007、HJ/T 300-2007和HJ 557-2009等国内外不同标准,研究了深圳某垃圾焚烧发电厂垃圾焚烧飞灰的浸出毒性,探讨了六硫代胍基甲酸（sixthio guanidine acid,SGA）、二甲基二硫代氨基甲酸盐（sodium dimethyl dithio carbamate,SDD）和Ca（OH）₂浓度对垃圾焚烧飞灰中重金属的固定性能的影响。研究结果表明,随着浸提液pH的降低,该厂焚烧飞灰中大部分金属元素的浸出量增大,焚烧飞灰浸出液中的Cd、Ni、Pb和Zn浓度分别超过国家危险废物鉴别标准（GB5085.3-2007）规定值的4.75倍、1.47倍、6.72倍和2.20倍,属于危险废弃物,必须进行稳定化处理。当固化剂SGA加入量为0.1 mol/kg时,稳定化后的重金属浸出浓度已经低于危险废物鉴别标准,且对Cd、Cr、Cu和Pb的固化性能优于SDD和Ca（OH）₂;当固化剂SGA、SDD和Ca（OH）₂加入量为0.5 mol/kg时,稳定化后的焚烧飞灰重金属浸出浓度均低于国家危险废物鉴别标准（GB 5085.3-2007）中的规定值。与SDD和Ca（OH）₂相比,SGA对垃圾焚烧飞灰中重金属的固化处理更具有优势。     

Thermal removal of PCDD/Fs from medical waste incineration fly ash--effect of temperature and nitrogen flow rate

The fly ash used in this study was collected from a bag filter in a medical waste rotary kiln incineration system, using lime and activated carbon injection followed by their collection as mixed fly ash. Experiments were conducted on fly ash in a quartz tube, heated in a laboratory-scale horizontal tube furnace, in order to study the effect of temperature and nitrogen flow rate on the removal of PCDD/Fs. Results indicated that in this study PCDD/Fs in the fly ash mostly were removed and desorbed very little into the flue gas under thermal treatment especially when the heating temperature was higher than 350 °C, and dechlorination and destruction reactions took important part in the removal of PCDD/Fs. However, in terms of flow rate, when flow rate was higher than 4 cm s⁻¹, destruction efficiency of PCDD/Fs decreased dramatically and the main contributors were P₅CDF, H₆CDF and H₇CDF desorbed to flue gas, the PCDD/Fs in the fly ash decreased with enhanced flow rate.     

Metal partitioning in products of incineration of municipal solid waste

Metals contained in the waste transfer to the waste incineration products, including flue gas, fly ash, and bottom ash, as different oxide, nitride, carbides, and other phases. Most of the metal-based phases formed in incineration are toxic and their emissions need to be strictly controlled. Therefore, behavior of metal species during incineration must be well understood. Such understanding is possible based on the experimental identification of the metal phases formed in the waste combustion and determination of their concentration in various incineration products. To avoid well-known experimental difficulties of the industrial waste incinerators associated with the poor fuel/conditions reproducibility and limited instrumentation, a 140,000 Btu/h pilot-scale, laboratory burner was constructed, characterized and operated at NJIT. A synthetic fuel representative of the municipal solid waste in the US was formulated and produced in 600-Lb batches. The solid fuel contained Fe and SiO2 as main constituents, and was doped with trace amounts of Al, Ni, Cr, Hg and PbO. Several experiments have been conducted on combustion of the synthetic fuel in the pilot-scale incinerator with varying fuel-air equivalence ratio. Both gaseous and condensed combustion products were sampled and analyzed. Atomic absorption spectroscopy and X-ray diffraction were used to analyze total metal contents and metal containing phases in the incineration products. Thermodynamic equilibrium computations were performed to obtain the adiabatic flame temperature and identify the phases of the metal-containing products formed at the equilibrium conditions. The results of the equilibrium computations performed at the varied fuel/air ratios were compared with the observed experimental results.     

粉煤灰的改性及其在垃圾渗滤液深度处理中的应用研究

实验采用物理方法和化学方法对粉煤灰进行改性,并用改性粉煤灰深度处理垃圾渗滤液。通过扫描电镜和X-射线衍射对改性前后粉煤灰的表面结构和主要晶相组成进行分析,同时考察其在垃圾渗滤液深度处理中的吸附效果。结果表明,改性后粉煤灰的比表面积和孔隙度增大,吸附能力增强。通过比较,吸附能力最强的改性粉煤灰是将引发剂A与粉煤灰以质量比为1∶9的比例混合,在800℃下恒温焙烧2 h所制得的改性粉煤灰,该改性粉煤灰对垃圾渗滤液中COD和色度的去除率可达到67.3%和87.3%,相对于改性前去除率提高了96.0%和57.8%。     

添加垃圾焚烧飞灰冷固小球的工业烧结实验

将垃圾焚烧飞灰添加进烧结冷固球团配料进行造球,对冷固小球的成分及强度进行分析,结果表明,添加垃圾焚烧飞灰冷固小球化学组成稳定,重金属浸出毒性远低于危险废物鉴别标准,落下强度较基准期略微降低,但符合运输、贮存的要求.并对添加了飞灰的冷固小球对其后续烧结、冶炼工序的影响进行分析,结果表明,用添加飞灰的冷固小球进行烧结所得烧结矿的转鼓强度、落下强度及常规化学成分较基准期没有太大变化,添加飞灰进行造球、烧结,对其后续冶炼工序的顺行几乎没有影响,所带来的额外的环境污染微乎其微.     

Batch test assessment of waste-to-energy combustion residues impacts on precipitate formation in landfill leachate collection systems

Disposal practices for bottom ash and fly ash from waste-to-energy (WTE) facilities include emplacement in ash monofills or co-disposal with municipal solid waste (MSW) and residues from water and wastewater treatment facilities. In some cases, WTE residues are used as daily cover in landfills that receive MSW. A recurring problem in many landfills is the development of calcium-based precipitates in leachate collection systems. Although MSW contains varying levels of calcium, WTE residues and treatment plant sludges have the potential to contribute concentrated sources of leachable minerals into landfill leachates. This study was conducted to evaluate the leachability of calcium and other minerals from residues generated by WTE combustion using residues obtained from three WTE facilities in Florida (two mass-burn and one refuse-derived fuel). Leaching potential was quantified as a function of contact time and liquid-to-solid ratios with batch tests and longer-term leaching tests using laboratory lysimeters to simulate an ash monofill containing fly ash and bottom ash. The leachate generated as a result of these tests had total dissolved solid (TDS) levels ranging from 5 to 320 mg TDS/g ash. Calcium was a major contributor to the TDS values, contributing from 20 to 105 g calcium/kg ash. Fly ash was a major contributor of leachable calcium. Precipitate formation in leachates from WTE combustion residues could be induced by adding mineral acids or through gas dissolution (carbon dioxide or air). Stabilization of residual calcium in fly ashes that are landfilled and/or the use of less leachable neutralization reagents during processing of acidic gases from WTE facilities could help to decrease the calcium levels in leachates and help to prevent precipitate formation in leachate collection systems.     

Effect of incineration on the removal of key offensive odorants released from a landfill leachate treatment station (LLTS)

As a basic means to control odorants released from a landfill leachate treatment station (LLTS), effluents venting from this station were treated via incineration with methane rich landfill gas (at 750 °C). A list of the key offensive odorants covering 22 chemicals was measured by collecting those gas samples both before and after the treatment. Upon incineration, the concentration levels of most odorants decreased drastically below threshold levels. The sum of odorant intensities (SOIs), if compared between before and after incineration, decreased from 6.94 (intolerable level) to 3.45 (distinct level). The results indicate that the thermal incineration method can be used as a highly efficient tool to remove most common odorants (e.g., reduced sulfur species), while it is not so for certain volatile species (e.g., carbonyls, fatty acids, etc.).     

Effect of dissolved humic matters on the leachability of PCDD/F from fly ash--laboratory experiment using Aldrich humic acid

The effect of dissolved humic matters (DHM) on the leachability of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) in fly ash was studied theoretically and in laboratorial condition to verify the previous results for pilot and field experiment of incineration residues landfill. In theoretical review, it was shown that DHM could influence the actual solubility and leachability of PCDD/F. The higher concentration of DHM showed the higher leachability of PCDD/F. In the leaching test, three different DHM concentrations and pHs of solutions were adopted to fly ash samples imaging the various characteristics of municipal solid waste leachate. It was proved experimentally that the leachability of PCDD/F increased with increasing DHM concentration in all pH conditions. The highest leachability was shown at the highest pH. Isomer distribution patterns of PCDD/F in all leachates were similar in all pH conditions. It backed up the distribution theory of PCDD/F between DHM and water.     

Removal of hydrogen sulfide gas and landfill leachate treatment using coal bottom ash.

Coal bottom ashes produced from three thermal power plants were used in column and batch experiments to investigate the adsorption capacity of the coal ash. Hydrogen sulfide and leachates collected from three sanitary landfill sites were used as adsorbate gas and solutions, respectively. Experimental results showed that coal bottom ash could remove H2S from waste gas or reduce the concentrations of various pollutants in the leachate. Each gram of bottom ash could remove up to 10.5 mg of H2S. In treating the landfill leachate, increasing ash dosage increased the removal efficiency but decreased the adsorption amount per unit mass of ash. For these tested ashes, the removal efficiencies of chemical oxygen demand (COD), NH3-N, total Kjeldhal nitrogen (TKN), P, Fe3+, Mn2+, and Zn2+ were 36.4-50, 24.2-39.4, 27.0-31.1, 82.2-92.9, 93.8-96.5, 93.7-95.4, and 80.5-82.2%, respectively; the highest adsorption capacities for those parameters were 3.5-5.6, 0.22-0.63, 0.36-0.45, 0.027-0.034, 0.050-0.053, 0.029-0.032, and 0.006 mg/g of bottom ash, respectively. The adsorption of pollutants in the leachate conformed to Freundlich's adsorption model.