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。     

Introduction of a waste incineration tax: Effects on the Swedish waste flows

A tax on waste-to-energy incineration of fossil carbon in municipal solid waste from households was introduced in Sweden on July 1, 2006. The tax has led to higher incineration gate fees. One of the main purposes with the tax is to increase the incentive for recycling of materials, including biological treatment. We investigate whether and to what extent this effect can be expected. A spreadsheet model is developed in order to estimate the net marginal cost of alternative waste treatment methods, i.e., the marginal cost of alternative treatment minus avoided cost of incineration. The value of the households’ time needed for source separation is discussed and included. The model includes the nine largest fractions, totalling 85% (weight), of the household waste currently being sent to waste incineration: food waste, newsprint, paper packaging, soft and hard plastic packaging, diapers, yard waste, other paper waste, and non-combustible waste. Our results indicate that the incineration tax will have the largest effect on biological treatment of kitchen and garden waste, which may increase by 9%. The consequences of an incineration tax depend on: (a) the level of the tax, (b) whether the tax is based on an assumed average Swedish fossil carbon content or on the measured carbon content in each incineration plant, (c) institutional factors such as the cooperation between waste incinerators, and (d) technological factors such as the availability of central sorting of waste or techniques for measurement of fossil carbon in exhaust gases, etc. Information turns out to be a key factor in transferring the governing force of the tax to the households as well improving the households’ attitudes towards material recycling.     

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.     

A preliminary assessment on reusage of flyash emitted from fluidized bed incineration of sludge cake

Reusage or recycle of flyash can eliminate the cost of final disposal and prevent secondary pollution caused by inappropriate flyash disposal. It is well known that the flyash emitted from fluidized bed incineration (FBI) is fine particle. Moreover its properties are more similar to concrete than that of ash from other incinerators. A promising and economical reusage of flyash is in concrete material. Prior to this application, it is necessary to explore the characteristics of cement mixed with flyash. Besides analyzing the general physical and chemical properties of FBI flyash, this article presents a preliminary assessment on reusage of FBI flyash in concrete by a series of experimental tests on the characteristics of flyash-cement paste, including the macrocharacteristics of fresh cement paste e.g. workability, bleeding water, setting time, compressive and tensile strengths, and micro-characteristics, e.g. paste hardening, pore distribution, and crystal structure. Effects of flyash amount in the paste and of flyash size on these properties are also studied. An approach to evaluate the reusage of flyash by inspecting the characteristics of flyash-cement paste is proposed, and leads to a potential reusage scheme for the FBI flyash as a concrete material resource.     

Effects of planned expansion of waste incineration in the Swedish district heating systems

Recent targets for reduced amounts of waste to landfills in Sweden will result in a large increase in waste incineration with recovery of energy, used primarily for district heating. The aim of this study is to investigate what changes in the usage of other fuels and technologies for district heat production would be caused by this increase. A questionnaire was sent out to the largest district heating companies, and simulations in an energy systems model were carried out. The analysis shows that increased waste incineration reduces the demand for other fuels, especially biomass, for district heat production. The effects include reductions in operating hours as well as the avoidance or postponement of investments in new plants for district heat production. Increased waste incineration will also lead to a greater use of district heating in Sweden.     

A generic comparison of the airborne risks to human health from landfill and incinerator disposal of municipal solid waste

A comparison of the potential risks to human health from municipal solid waste (MSW) incineration and landfill on a generic basis is attempted. For this purpose a 'worst case' approach is adopted and a number of assumptions regarding the size and activities of each waste disposal method are made. The airborne pollutants measured for an incinerator are different from those for a landfill with or without gas collection. However, based on the available information it appears that as far as airborne pollution is concerned, landfill sites without gas collection pose a potentially higher generic risk to human health than MSW incinerators performing to Environmental Agency (UK) standards. This analysis cannot be used to replace specific evaluations for a particular incinerator or a landfill site because local conditions can have a very large impact on the magnitude of risks involved.     

Zeolite formation from coal fly ash and heavy metal ion removal characteristics of thus-obtained Zeolite X in multi-metal systems

Zeolitic materials have been prepared from coal fly ash as well as from a SiO₂–Al₂O₃ system upon NaOH fusion treatment, followed by subsequent hydrothermal processing at various NaOH concentrations and reaction times. During the preparation process, the starting material initially decomposed to an amorphous form, and the nucleation process of the zeolite began. The carbon content of the starting material influenced the formation of the zeolite by providing an active surface for nucleation. Zeolite A (Na-A) was transformed into zeolite X (Na-X) with increasing NaOH concentration and reaction time. The adsorption isotherms of the obtained Na-X based on the characteristics required to remove heavy ions such as Ni²⁺, Cu²⁺, Cd²⁺ and Pb²⁺ were examined in multi-metal systems. Thus obtained experimental data suggests that the Langmuir and Freundlich models are more accurate compared to the Dubinin–Kaganer–Radushkevich (DKR) model. However, the sorption energy obtained from the DKR model was helpful in elucidating the mechanism of the sorption process. Further, in going from a single- to multi-metal system, the degree of fitting for the Freundlich model compared with the Langmuir model was favored due to its basic assumption of a heterogeneity factor. The Extended-Langmuir model may be used in multi-metal systems, but gives a lower value for equilibrium sorption compared with the Langmuir model.     

The potential contribution of sustainable waste management to energy use and greenhouse gas emission reduction in the Netherlands

Future limitations on the availability of selected resources stress the need for increased material efficiency. In addition, in a climate-constrained world the impact of resource use on greenhouse gas emissions should be minimized. Waste management is key to achieve sustainable resource management. Ways to use resources more efficiently include prevention of waste, reuse of products and materials, and recycling of materials, while incineration and anaerobic digestion may recover part of the embodied energy of materials. This study used iWaste, a simulation model, to investigate the extent to which savings in energy consumption and CO₂ emissions can be achieved in the Netherlands through recycling of waste streams versus waste incineration, and to assess the extent to which this potential is reflected in the LAP2 (currently initiated policy). Three waste streams (i.e. household waste, bulky household waste, and construction and demolition waste) and three scenarios compare current policy to scenarios that focus on high-quality recycling (Recycling+) or incineration with increased efficiency (Incineration+). The results show that aiming for more and high-quality recycling can result in emission reductions of 2.3 MtCO₂ annually in the Netherlands compared to the reference situation in 2008. The main contributors to this reduction potential are found in optimizing the recycling of plastics (PET, PE and PP), textiles, paper, and organic waste. A scenario assuming a higher energy conversion efficiency of the incinerator treating the residual waste stream, achieves an emission reduction equivalent to only one third (0.7 MtCO₂/year) of the reduction achieved in the Recycling+ scenario. Furthermore, the results of the study show that currently initiated policy only partially realizes the full potential identified. A focus on highest quality use of recovered materials is essential to realize the full potential energy and CO₂ emission reduction identified for the Netherlands. Detailed economic and technical analyses of high quality recycling are recommended to further evaluate viable integrated waste management policies.     

A study on recovery of oil from sludge containing oil using froth flotation

Induced air flotation was used to recover oil from synthetically prepared sludge containing oil. A commercial surfactant was used as the collector and frother. The effects of various parameters, namely flotation time, initial amount of oil in the feed and the amount of surfactant used on the recovery of oil were investigated. Within the range of operating conditions studied herein, the maximum oil recovery obtained was about 55%. A detailed study of flotation kinetics based on oil recovery was carried out. It showed that the process followed first-order kinetics.     

Characterization of waste materials originating from Quebec supermarkets and an assessment of recycling potential

This study evaluated, both qualitatively and quantitatively, waste materials from several major Quebec grocery stores. Averaged over nine sampling dates, cardboard, paper and wood products represented 43 and 74% of waste material, based on weight and volume, respectively while organic matter including fruits, vegetables, baked goods and meat products represented 40 and 10% of waste material based on weight and volume. Plastics, wrapping and bagging materials, represented over 7 and 13% of waste material based on weight and volume, respectively, and other recyclable waste materials such as glass, metal and various miscellaneous objects, represented 4 and 2% of waste material based on weight and volume. On average, 60.6 kg waste/employee per week was generated by the three stores. Store size was not a determining factor in the composition of grocery store waste material. These results suggest that costs associated with supermarket waste disposal may be substantially reduced by source-separation of recyclable and compostable materials while reducing pressure for incineration or landfill. Therefore, the adoption of recycling and source-separation programs, and studies to determine problems and costs associated with the implementation of such programs are recommended.     

我国南方某城市垃圾焚烧飞灰特性及固化/稳定化处置实验

我国南方某城市主要采用焚烧法处理生活垃圾,已建7个焚烧厂日产生飞灰量为101.62 t/d。文章分析了各个垃圾焚烧厂飞灰的化学组成和重金属浸出毒性,其主要成分为CaO、SiO2、MgO、Al2O3、Fe2O3、Na2O、SO3和Cl,所有焚烧飞灰都有至少一种重金属浸出浓度超标,属于危险废物。在飞灰处置出路亟待解决的背景下,实验探讨了飞灰稳定化工艺,结果表明10%的水泥添加量可以使飞灰中超标重金属(Cd、Pb和Zn)的浸出浓度满足危险废物鉴别浓度限值和安全填埋场入场浓度限值。同时,通过人体健康风险评价分析了飞灰豁免管理的可行性,并对近期和远期该城市焚烧厂飞灰的处理处置及管理提出建议。     

Bioethanol from waste: Life cycle estimation of the greenhouse gas saving potential

This paper considers two alternative feedstocks for bioethanol production, both derived from household waste—Refuse Derived Fuel (RDF) and Biodegradable Municipal Waste (BMW). Life Cycle Assessment (LCA) has been carried out to estimate the GHG emissions from bioethanol using these two feedstocks. An integrated waste management system has been considered, taking into account recycling of materials and production of bioethanol in a combined gasification/bio-catalytic process. For the functional unit defined as the ‘total amount of waste treated in the integrated waste management system’, the best option is to produce bioethanol from RDF—this saves up to 196 kg CO₂ equiv. per tonne of MSW, compared to the current waste management practice in the UK.However, if the functional unit is defined as ‘MJ of fuel equiv.’ and bioethanol is compared with petrol on an equivalent energy basis, the results show that bioethanol from RDF offers no saving of GHG emissions compared to petrol. For example, for a typical biogenic carbon content in RDF of around 60%, the life cycle GHG emissions from bioethanol are 87 g CO₂ equiv./MJ while for petrol they are 85 g CO₂ equiv./MJ. On the other hand, bioethanol from BMW offers a significant GHG saving potential over petrol. For a biogenic carbon content of 95%, the life cycle GHG emissions from bioethanol are 6.1 g CO₂ equiv./MJ which represents a saving of 92.5% compared to petrol. In comparison, bioethanol from UK wheat saves 28% of GHG while that from Brazilian sugar cane – the best performing bioethanol with respect to GHG emissions – saves 70%. If the biogenic carbon of the BMW feedstock exceeds 97%, the bioethanol system becomes a carbon sequester. For instance, if waste paper with the biogenic carbon content of almost 100% and a calorific value of 18 MJ/kg is converted into bioethanol, a saving of 107% compared to petrol could be achieved. Compared to paper recycling, converting waste paper into bioethanol saves 460 kg CO₂ equiv./t waste paper or eight times more than recycling.     

Electronic waste recycling: A review of U.S. infrastructure and technology options

The useful life of consumer electronic devices is relatively short, and decreasing as a result of rapid changes in equipment features and capabilities. This creates a large waste stream of obsolete electronic equipment, electronic waste (e-waste).Even though there are conventional disposal methods for e-waste, these methods have disadvantages from both the economic and environmental viewpoints. As a result, new e-waste management options need to be considered, for example, recycling. But electronic recycling has a short history, so there is not yet a solid infrastructure in place.In this paper, the first half describes trends in the amount of e-waste, existing recycling programs, and collection methods. The second half describes various methods available to recover materials from e-waste. In particular, various recycling technologies for the glass, plastics, and metals found in e-waste are discussed. For glass, glass-to-glass recycling and glass-to-lead recycling technologies are presented. For plastics, chemical (feedstock) recycling, mechanical recycling, and thermal recycling methods are analyzed. Recovery processes for copper, lead, and precious metals such as silver, gold, platinum, and palladium are reviewed. These processes are described and compared on the basis of available technologies, resources, and material input–output systems.     

生活垃圾焚烧发电厂设计新思路探讨

以兴义市生活垃圾焚烧发电厂工程为例,介绍了该项目设计的主要内容;总结了项目设计中节省投资和改善环境的新思路,以助于推进生活垃圾焚烧处理技术的应用。     

Assessing potential bioavailability of metals in sediments: A proposed approach

Due to anthropogenic inputs, elevated concentrations of metals frequently occur in aquatic sediments. In order to make defensible estimates of the potential risk of metals in sediments and/or develop sediment quality criteria for metals, it is essential to identify that fraction of the total metal in the sediments that is bioavailable. Studies with a variety of benthic invertebrates indicate that interstitial (pore) water concentrations of metals correspond very well with the bioavailability of metals in test sediments. Many factors may influence pore water concentrations of metals; however, in anaerobic sediments a key phase controlling partitioning of several cationic metals (cadmium, nickel, lead, zinc, copper) into pore water is acid volatile sulfide (AVS). In this paper, we present an overview of the technical basis for predicting bioavailability of cationic metals to benthic organisms based on pore water metal concentrations and metal-AVS relationships. Included are discussions of the advantages and limitations of metal bioavailability predictions based on these parameters, relative both to site-specific assessments and the development of sediment quality criteria.     

从炼厂含油污泥中回收油及残渣无害化治理的研究

通过对某油田石化厂的含油污泥中回收油及其残渣无害化治理问题的研究，确定了用热洗加离心分离实现污油回收及残渣无害化。根据实验室数据，处理此种含油污泥可达到如下结果：油回收率９５％，残渣中油及主要污染物含量基本符合ＧＢ４２８－８４标准，工艺污水符合进入污水场的要求。采用此法，按照２ｔ／ｈ的处理量计算，预计设备投资４５．７万元。     

Techno-economic analysis and environmental impact assessment of energy recovery from Municipal Solid Waste (MSW) in Brazil

Due to the lack of appropriate policies in the last decades, 60% of Brazilian cities still dump their waste in non-regulated landfills (the remaining ones dump their trash in regulated landfills), which represent a serious environmental and social problem. The key objective of this study is to compare, from a techno-economic and environmental point of view, different alternatives to the energy recovery from the Municipal Solid Waste (MSW) generated in Brazilian cities. The environmental analysis was carried out using current data collected in Betim, a 450,000 inhabitants city that currently produces 200 tonnes of MSW/day. Four scenarios were designed, whose environmental behaviour were studied applying the Life Cycle Assessment (LCA) methodology, in accordance with the ISO 14040 and ISO 14044 standards. The results show the landfill systems as the worst waste management option and that a significant environmental savings is achieved when a wasted energy recovery is done. The best option, which presented the best performance based on considered indicators, is the direct combustion of waste as fuel for electricity generation. The study also includes a techno-economical evaluation of the options, using a developed computer simulation tool. The economic indicators of an MSW energy recovery project were calculated. The selected methodology allows to calculate the energy content of the MSW and the CH₄ generated by the landfill, the costs and incomes associated with the energy recovery, the sales of electricity and carbon credits from the Clean Development Mechanism (CDM). The studies were based on urban centres of 100,000, 500,000 and 1,000,000 inhabitants, using the MSW characteristics of the metropolitan region of Belo Horizonte. Two alternatives to recovering waste energy were analyzed: a landfill that used landfill biogas to generate electricity through generator modules and a Waste-to-Energy (WtE) facility also with electricity generation. The results show that power generation projects using landfill biogas in Brazil strongly depend on the existence of a market for emissions reduction credits. The WtE plant projects, due to its high installation, Operation and Maintenance (O&M) costs, are highly dependent on MSW treatment fees. And they still rely on an increase of three times the city taxes to become attractive.     

A mechanical pre-treatment process for the valorization of useful fractions from spent batteries

In this paper the authors propose a full-scale plant aimed to pre-treat spent batteries in order to obtain cleaned useful fractions (magnetic and non-magnetic metals, paper, plastic, a fine-sized material made of a metal-carbon mixture). The treating process was designed after having analyzed and tested a representative sample coming from the whole amount of spent batteries collected in 1 month by the public service in and around Turin. The analyses performed on the sample allowed the authors to determine its in-percentage composition in term of type of batteries: 60-70% b.w. (by weight) alkaline, 25-30% b.w. Zn-C and 5-10% b.w. other types. For each type, the composition in term of size (AAA or LR03; AA or LR6; C or LR14; D or LR20; 9 V or 6F22A; 4.5 V or 3R12A) has also been determined.The treatment for the recovery of secondary raw materials foresees the following phases:

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separation of useful types/sizes of exhaust batteries to undergo further treatments by means of a first sieving process;

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liberation of the single components taking advantage of a crushing operation;

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separation of a fine-sized material (to subject to pyro or hydro metallurgic recovery) from a coarse-sized material (to send to secondary smelt foundries and incinerators) by means of a second sieving phase.

On the basis of the results obtained from the crushing/sieving laboratory tests and the chemical characterization, a full-scale plant able to treat about 76,000 t/y of spent batteries has been designed. The cost analysis performed on the proposed treatment plant has given back a unit pre-treatment cost equal to 3€ per ton of processed spent batteries.     

The recycling of rare earths from waste tricolor phosphors in fluorescent lamps: A review of processes and technologies

Rare earths have become the most important strategic resources, widely used as functional materials in industry and many other aspects of life due to its optical, electrical, and magnetic characteristics. As a consequence, a considerable number of wastes containing rare earths such as abandoned fluorescent lamps are generated and lost. Considering the scarcity in availability and supply of certain raw materials, waste tricolor phosphors are viewed as potential resources that can be mined in urban areas for their reutilization as rare earths. A number of studies in this area have been carried out all over the world.The purpose of this paper is to review the current status of recycling technologies of rare earths from waste tricolor phosphors in fluorescent lamps. The main characteristics of the tricolor phosphors were introduced, and also a detail review of the typical single recycling and reusing technologies with regard to waste tricolor phosphors was carried out in present paper. After that, several combined recycling processes and technologies were evaluated. Based on the review, the prospects of recycling technologies were suggested.     

Kerbside collection: A case study from the north-west of England

It is widely agreed that public support is vital to the success of most recycling schemes; the actions of householders are paramount to the success of sustainable waste policies. However, the success of recycling schemes is not just dependent on public participation; it is also dependent on careful planning, effective design and tailoring to local needs.This study has evaluated a kerbside recycling scheme in the north-west of England by comparing the recycling performance of those on alternate collections of residual waste and recyclates with those on weekly residual collections and fortnightly recyclate collections. Three data collection methodologies were adopted: postal questionnaires, set-out rate monitoring, and personal interviews with policy writers.The results demonstrated that alternate collections produce higher recycling set-out rates, suggesting that alternate collections will also generate higher recycling rates. The research showed that if designed and complemented by other services, then an alternate collection system is a realistic waste management approach. However, the local authority and the public appear to use different indicators of success for the scheme. The local authority uses governmental performance indicators (such as best value performance indicators—BVPIs) to measure success, whereas the public's indicators of success tend to focus more on issues such as required changes to established behaviours, convenience and personal preferences.A key recommendation from this study is that all local authorities should carry out local opinion surveys on an annual basis to supplement the BVPIs required by statute. This should help them to fill the information gaps in order to provide a comprehensive, up-to-date and user-responsive waste management service to the public.