城市垃圾预处理改善焚烧特性的探讨

针对目前我国城市垃圾的高水分、低热值的特性,提出了2种改善城市垃圾焚烧特性的有效措施:生物质垃圾源分类和生物干燥.在我国建立生物质垃圾源分类体系,将生物质垃圾源头分类后,剩余垃圾的热值可以提高约50%～120%,已适合直接入炉焚烧,同时分离出来的生物质垃圾也更易于好氧堆肥或厌氧消化.另外一项技术措施是在焚烧前利用生物干燥技术,降低城市垃圾的水分含量,提高入炉垃圾的热值,这种方法主要是利用生物反应热来干燥城市生活垃圾,只需要在垃圾投入焚烧炉前增加一个预处理步骤,不必改变目前的垃圾收运体系,而且进行生物干燥后的垃圾更易于分选其中的可回收物质.     

Source separation of municipal solid waste: The effects of different separation methods and citizens’ inclination—case study of Changsha,China

A case study on the source separation of municipal solid waste (MSW) was performed in Changsha, the capital city of Hunan Province, China. The objective of this study is to analyze the effects of different separation methods and compare their effects with citizens’ attitudes and inclination. An effect evaluation method based on accuracy rate and miscellany rate was proposed to study the performance of different separation methods. A large-scale questionnaire survey was conducted to determine citizens’ attitudes and inclination toward source separation. Survey result shows that the vast majority of respondents hold consciously positive attitudes toward participation in source separation. Moreover, the respondents ignore the operability of separation methods and would rather choose the complex separation method involving four or more subclassed categories. For the effects of separation methods, the site experiment result demonstrates that the relatively simple separation method involving two categories (food waste and other waste) achieves the best effect with the highest accuracy rate (83.1%) and the lowest miscellany rate (16.9%) among the proposed experimental alternatives. The outcome reflects the inconsistency between people’s environmental awareness and behavior. Such inconsistency and conflict may be attributed to the lack of environmental knowledge. Environmental education is assumed to be a fundamental solution to improve the effect of source separation of MSW in Changsha. Important management tips on source separation, including the reformation of the current pay-as-you-throw (PAYT) system, are presented in this work.

Implications: A case study on the source separation of municipal solid waste was performed in Changsha. An effect evaluation method based on accuracy rate and miscellany rate was proposed to study the performance of different separation methods. The site experiment result demonstrates that the two-category (food waste and other waste) method achieves the best effect. The inconsistency between people’s inclination and the effect of source separation exists. The proposed method can be expanded to other cities to determine the most effective separation method during planning stages or to evaluate the performance of running source separation systems.     

Life cycle and economic assessment of source-separated MSW collection with regard to greenhouse gas emissions: a case study in China

In China, the continuously increasing amount of municipal solid waste (MSW) has resulted in an urgent need for changing the current municipal solid waste management (MSWM) system based on mixed collection. A pilot program focusing on source-separated MSW collection was thus launched (2010) in Hangzhou, China, to lessen the related environmental loads. And greenhouse gas (GHG) emissions (Kyoto Protocol) are singled out in particular. This paper uses life cycle assessment modeling to evaluate the potential environmental improvement with regard to GHG emissions. The pre-existing MSWM system is assessed as baseline, while the source separation scenario is compared internally. Results show that 23 % GHG emissions can be decreased by source-separated collection compared with the base scenario. In addition, the use of composting and anaerobic digestion (AD) is suggested for further optimizing the management of food waste. 260.79, 82.21, and ?86.21 thousand tonnes of GHG emissions are emitted from food waste landfill, composting, and AD, respectively, proving the emission reduction potential brought by advanced food waste treatment technologies. Realizing the fact, a modified MSWM system is proposed by taking AD as food waste substitution option, with additional 44 % GHG emissions saved than current source separation scenario. Moreover, a preliminary economic assessment is implemented. It is demonstrated that both source separation scenarios have a good cost reduction potential than mixed collection, with the proposed new system the most cost-effective one.     

填埋场不同深度垃圾土压缩性的室内试验研究

阐述了垃圾土的压缩机理,归纳了国内外垃圾土压缩性指标的研究成果。根据某填埋场3个不同深度的垃圾土试样,在改装后的高压固结仪上进行压缩试验,得到垃圾土的压缩系数a、主压缩指数C、修正主压缩指数C'、压缩模量E以及体积压缩系数m,并对试验结果进行分析。试验结果表明,垃圾土的初始孔隙比随填埋深度的增加而减小,垃圾土的压缩指数随其可降解度和有机质含量的减少而降低,垃圾土具有高压缩性,其压缩性指标与垃圾的组成和填埋深度有关。将得到的压缩性指标与国内外的资料进行了比较,可为填埋场的设计及变形计算提供参考。     

Biodegradation of organic matters from mixed unshredded municipal solid waste through air convection before landfilling

Landfilling is a dominant municipal solid waste (MSW) disposal method in most developing countries. In China, approximately 85% of the generated MSW is being disposed of in the landfills. The amount of MSW is growing rapidly with the rate of approximately 8-10% annually, which contains a high quantity of moisture and organic matters. The problems of leachate treatment and landfill gas (LFG) emissions are increasing gradually. Reducing the hazard before emplacement, pretreatment of MSW before landfilling has become very important for the conventional landfill. In this study, aerobic pretreatment of mixed MSW was used, and much attention has been given to the natural convection of air in the mixed and unshredded MSW for bioconversion of organic matter (OM). This study is an attempt to investigate aerobic pretreatment suitability for the mixed and unshredded MSW at Beijing. A pilot-scale aerobic pretreatment simulator (APS) was developed at Beishen Shu Landfill in Beijing. To work out the biodegradation of the OM in the APS, fresh and pretreated MSW samples were collected and analyzed for OM, moisture content, temperature, chemical oxygen demand, total organic carbon, carbon, nitrogen, hydrogen, lignocelluloses, and biochemical methane potential at various stages of the pretreatment. Furthermore, results of the fresh and pretreated MSW are compared. Significant reduction in the observed parameters of the pretreated waste samples is observed. This work demonstrates that pretreatment is significantly effective in reducing the landfill emissions that is leachate and LFG.     

Remedial strategies for municipal solid waste management in China

The purpose of this investigation is to evaluate the current status and to identify the problems of municipal solid waste (MSW) management in China to determine appropriate remedial strategies. This is the second of two papers proposed on this topic. Major problems or difficulties identified in MSW management in China include MSW land, air, and water pollution, commingled collection, poor administration, shortage of funds, lack of facilities, and problems of training and public awareness. In order to solve these problems and to improve MSW management in China, remedial strategies in three areas are recommended: institutional reform, technology development, and legislation and administrative improvement. The primary principle involved in institutional reform is unifying legislative responsibilities into one body and developing a market mechanism for handling MSW. Composting, landfills, and incineration should be equally developed in accordance with China's needs. The feasibility of developing technology to handle MSW in China is discussed. Also recommended is the establishment of sound regulatory systems, including a service fee system, a source separation system, and a training program. China is presently undergoing economic and institutional reform at the national and local levels. Results of this study will provide useful information on MSW management in China.     

Remedial Strategies for Municipal Solid Waste Management in China

ABSTRACT

The purpose of this investigation is to evaluate the current status and to identify the problems of municipal solid waste (MSW) management in China to determine appropriate remedial strategies. This is the second of two papers proposed on this topic. Major problems or difficulties identified in MSW management in China include MSW land, air, and water pollution, commingled collection, poor administration, shortage of funds, lack of facilities, and problems of training and public awareness.

In order to solve these problems and to improve MSW management in China, remedial strategies in three areas are recommended: institutional reform, technology development, and legislation and administrative improvement. The primary principle involved in institutional reform is unifying legislative responsibilities into one body and developing a market mechanism for handling MSW. Composting, landfills, and incineration should be equally developed in accordance with China's needs. The feasibility of developing technology to handle MSW in China is discussed. Also recommended is the establishment of sound regulatory systems, including a service fee system, a source separation system, and a training program. China is presently undergoing economic and institutional reform at the national and local levels. Results of this study will provide useful information on MSW management in China.     

回转窑式纯氧熔融焚烧垃圾技术研究

生活垃圾安全无害化处理是目前迫切需要解决的问题,直接气化熔融焚烧垃圾技术以降低二恶英排放方面巨大优势得到广泛关注,在此基础上提出纯氧熔融焚烧垃圾技术,几乎可以实现所有二次污染物近零排放。以350 t/d回转窑垃圾焚烧炉为例,对纯氧代替空气应用在回转窑上熔融焚烧垃圾系统进行了详细热力计算及分析。结果表明,纯氧熔融焚烧垃圾系统的锅炉效率可达90.56%,回转窑熔融焚烧系统还可以在垃圾焚烧后灰渣达到熔融温度的条件下,保持该系统热量平衡,稳定燃烧。并参考回转窑设计标准对该纯氧熔融焚烧城市生活垃圾的回转窑参数进行确定。     

北京市生活垃圾处理的环境影响评价

目前北京市生活垃圾产生量不断增加,处理设施能力日渐不足,生活垃圾管理正面临着减量化与资源化必然趋势。在未来5～10年内,堆肥处理、焚烧处理和综合处理等方式将取代卫生填埋成为北京市垃圾处理的主要方式。本研究采用生命周期评价的方法,对北京市4处垃圾处理设施采用的不同工艺（卫生填埋、好氧堆肥、焚烧处理和综合处理）的环境影响进行比较。评价结果表明4,种处理方式中填埋、堆肥、焚烧和综合处理的环境影响负荷分别为4.82×10-2、1.10×10-21、.31×10-1和2.31×10-2,焚烧处理的总环境影响潜值最大,填埋处理次之,综合处理再次,堆肥处理最小。4种处理方式的资源耗竭系数分别为-2.39×10-51、.11×10-5、-3.45×10-4和-1.04×10-6,焚烧处理的资源耗竭系数最小。     

Food waste collection and recycling for value-added products: potential applications and challenges in Hong Kong

About 3600 tonnes food waste are discarded in the landfills in Hong Kong daily. It is expected that the three strategic landfills in Hong Kong will be exhausted by 2020. In consideration of the food waste management environment and community needs in Hong Kong, as well as with reference to the food waste management systems in cities such as Linköping in Sweden and Oslo in Norway, a framework of food waste separation, collection, and recycling for food waste valorization is proposed in this paper. Food waste can be packed in an optic bag (i.e., a bag in green color), while the residual municipal solid waste (MSW) can be packed in a common plastic bag. All the wastes are then sent to the refuse transfer stations, in which food waste is separated from the residual MSW using an optic sensor. On the one hand, the sorted food waste can be converted into valuable materials (e.g., compost, swine feed, fish feed). On the other hand, the sorted food waste can be sent to the proposed Organic Waste Treatment Facilities and sewage treatment works for producing biogas. The biogas can be recovered to produce electricity and city gas (i.e., heating fuel for cooking purpose). Due to the challenges faced by the value-added products in Hong Kong, the biogas is recommended to be upgraded as a biogas fuel for vehicle use. Hopefully, the proposed framework will provide a simple and effective approach to food waste separation at source and promote sustainable use of waste to resource in Hong Kong.     

Control of mercury emissions from a municipal solid waste incinerator in Japan

The control of Hg emissions from a municipal solid waste incinerator (MSWI) is very important, because more than 78% of municipal solid waste (MSW) is incinerated. The Hg content of coal used in utility boilers is relatively low in Japan. In this study, recent trends in the Hg content of MSW in Japan and activated carbon (AC) injection as a control technology of Hg emission from an MSWI are discussed. The effect of AC injection on Hg removal from flue gas in an MSWI was investigated by pilot-scale experiments using a bag filter (BF). The injection of AC increases the Hg reduction ratio by 20-30% compared with cases without AC injection. The Hg reduction ratio increases as the flue gas temperature decreases. The Hg reduction ratio is closely related to the inlet Hg concentration and was expressed with a Langmuir-type adsorption isotherm.     

Phytoavaelability and extractability of copper and zinc in calcareous soil amended with composted Urban wastes

Abstract

A greenhouse experiment was conducted under simulated field conditions using large‐capacity plastic pots, filled each one with 25 kg of air‐dried calcareous soil. Besides the control, four treatments were prepared by applying separately two rates (20 and 80 Mg ha^‐1) of municipal solid waste (MSW) compost, and co‐composted municipal solid waste and sewage sludge (MSW‐SS). Lettuce was planted and harvested 2.5 months later. The application of composted urban wastes tended to increase Cu concentration in lettuce with respect to the control, but it was only significant when the higher rate of MSW compost was applied. The control showed values of Zn concentration in plant within a deficient range. In general, composted urban wastes treatments had increased Zn concentration values, which were within the sufficiency range. Both treatments with MSW compost increased Cu and Zn uptake in comparison with MSW‐SS co‐compost treatments. At the postharvest, all composted urban wastes treatments increased significantly DTPA‐extractable Cu content in soil with respect to the control; it was also significant the increase in AAAc‐EDTA‐extractable Cu in soil produced by the addition of the higher rate of MSW compost. The application of composted urban wastes increased significantly DTPA‐extractable and AAAc‐EDTA‐extractable Zn contents in soil versus the control, except for the lower rate of MSW‐SS co‐compost. The values of DTPA‐extractable/total ratio for Cu and Zn were under 10%, except for the treatment applying the higher rate of MSW compost which promoted higher values. The values of AAAc‐EDTA‐extractable/total ratio for Cu were above 10% in all treatments including the control. This tendency was also observed in AAAc‐EDTA‐extractable/total ratio for Zn when applying both rates of MSW compost or the higher rate of MSW‐SS co‐compost.     

A survey of municipal solid waste landfills in Beijing during 2009–2011

The investigation of municipal solid waste (MSW) treatment in China is rare due to its sensitivity and difficulty in terms of access. We chose Beijing, the capital of China, as an example to identify the characteristics of MSW landfill treatments using a 2-month investigation with 20 participants. MSW landfill treatments account for nearly 70% of the annual MSW disposal in Beijing; the landfill processes are equipped with many kinds of technologies and consume a large amount of energy and produce a variety of contaminants. The cover method (the most obvious difference in landfill tamping) mainly includes high-density polyethylene (HDPE) geomembranes with loess and soil alone (i.e., loess or sandy soil). We investigated the actual conditions of landfills and collected data on leachate and landfill gas (LFG) emissions and energy consumption during 2009–2011. The results indicated that the cover method employed by landfills was related to treatment quantity, operation, and especially landfill location. Early large-scale landfills located in plains were covered with HDPE geomembranes, and newly built landfills covered with soil tended to be equipped with HDPE covers. Using HDPE cover also contributed greatly to LFG production due to its impermeability but had no remarkable effect on leachate yield reduction due to the dry climate in Beijing. The potential was reinforced by the potentials of decrement and reuse. The disposal method of LFG can be optimized, and the power generated by the LFG process can meet the landfill demand. The gray water recycled from the leachate could be used in the landfill process.

     

Control of Mercury Emissions from a Municipal Solid Waste Incinerator in Japan

Abstract

The control of Hg emissions from a municipal solid waste incinerator (MSWI) is very important, because more than 78% of municipal solid waste (MSW) is incinerated. The Hg content of coal used in utility boilers is relatively low in Japan. In this study, recent trends in the Hg content of MSW in Japan and activated carbon (AC) injection as a control technology of Hg emission from an MSWI are discussed. The effect of AC injection on Hg removal from flue gas in an MSWI was investigated by pilot-scale experiments using a bag filter (BF). The injection of AC increases the Hg reduction ratio by 20–30% compared with cases without AC injection. The Hg reduction ratio increases as the flue gas temperature decreases. The Hg reduction ratio is closely related to the inlet Hg concentration and was expressed with a Langmuir-type adsorption isotherm.     

Phytoavailability and extractability of copper and zinc in calcareous soil amended with composted urban wastes

A greenhouse experiment was conducted under simulated field conditions using large-capacity plastic pots, filled each one with 25 kg of air-dried calcareous soil. Besides the control, four treatments were prepared by applying separately two rates (20 and 80 Mg ha-1) of municipal solid waste (MSW) compost, and co-composted municipal solid waste and sewage sludge (MSW-SS). Lettuce was planted and harvested 2.5 months later. The application of composted urban wastes tended to increase Cu concentration in lettuce with respect to the control, but it was only significant when the higher rate of MSW compost was applied. The control showed values of Zn concentration in plant within a deficient range. In general, composted urban wastes treatments had increased Zn concentration values, which were within the sufficiency range. Both treatments with MSW compost increased Cu and Zn uptake in comparison with MSW-SS co-compost treatments. At the postharvest, all composted urban wastes treatments increased significantly DTPA-extractable Cu content in soil with respect to the control; it was also significant the increase in AAAc-EDTA-extractable Cu in soil produced by the addition of the higher rate of MSW compost. The application of composted urban wastes increased significantly DTPA-extractable and AAAc-EDTA-extractable Zn contents in soil versus the control, except for the lower rate of MSW-SS co-compost. The values of DTPA-extractable/total ratio for Cu and Zn were under 10%, except for the treatment applying the higher rate of MSW compost which promoted higher values. The values of AAAc-EDTA-extractable/total ratio for Cu were above 10% in all treatments including the control. This tendency was also observed in AAAc-EDTA-extractable/total ratio for Zn when applying both rates of MSW compost or the higher rate of MSW-SS co-compost.     

复合微生物菌剂强化堆肥技术研究

采用复合微生物菌剂对生活垃圾的接种堆肥技术进行了实验研究。通过测定堆肥过程中反应器出口O2、CO2与H2S气体浓度及对堆肥样品扫描电镜照片分析，比较了3个接种组与1个对照组中堆料中微生物总数变化、种群结构演替及堆肥腐熟速度。试验结果表明，在原料成分为：生活垃圾／成熟堆肥=80／20，有机物约为60％，初始含水率为55％，初始C／N-30时，对于不同接种量的复合微生物接种系统堆料中分别接种0．2％、0．3％、0．5％(质量百分含量)，与加入0．3％灭活菌的对照组进行对比实验，接种复合微生物菌剂堆肥系统不仅微生物总数高于对照组，而且其种群结构合理，能明显提高堆肥效率，有效控制臭气的产生，提高堆肥腐熟度。     

Improvements to the UK PCDD/F and PCB atmospheric emission inventory following an emissions measurement programme

PCDD/F data are presented from 75 samples of primary emissions sampled between 1995-97 as part of the compliance monitoring survey undertaken by the UK Environment Agency. Municipal solid waste (MSW), chemical waste and clinical waste incinerators, cement kilns, sinter plants and sewage sludge incinerators were the source categories monitored and reported here. Based on this monitoring programme, the previous national UK emission estimates by Eduljee and Dyke (1) of 560-1100 g I-TEQ a(-1) for 1993 have been revised downwards to 220-660 g I-TEQ a(-1). Despite source reduction measures, MSW incinerators remain a significant source of PCDD/Fs to the atmosphere, contributing between 30-50% of the EPCDD/F I-TEQ emission, rather than the approximately 80% they were estimated to contribute in 1993. 2,3,7,8-substituted PCDD/F congener profile data are presented for some of the source categories and generally support the view that differences in the mixtures ('fingerprints') of PCDD/Fs emitted from different sources are observed. New data on the dioxin-like PCB emissions are presented for cement kilns and sinter plants. These show that TEQ-rated PCBs can make an important contribution to the I-TEQ emitted from certain combustion sources. High concentrations of a full range of PCB congeners/homologues have been measured in the atmosphere close to sintering strands, although the precise source of PCBs from this process remains unclear.     

垃圾焚烧炉炉膛温度的影响因素

垃圾焚烧过程的不稳定会导致大量有害物质的生成,为确保垃圾的清洁燃烧需要将炉膛温度控制在850℃以上,为此测试了焚烧炉运行的主要可控参数对炉膛温度的影响。结果表明,垃圾堆放位置在垃圾池深3～8 m处,并经过6 d以上发酵脱水后适合焚烧;炉膛温度随给料量、一次风率和一次风温增加而增大,随过量空气系数增加而降低,其中给料量宜控制在95%～110%之间;当过量空气系数为1.6、一次风率为90%、一次风温为260℃、给料量为100%时炉膛温度达901℃。     

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.     

生活垃圾焚烧烟气排放中二噁英对人体健康的风险评价

随着垃圾焚烧的广泛应用,由此产生的二次污染问题也日益显现出来,特别是二嗯英污染已引起世界的关注。这也是垃圾焚烧设施在环评阶段遭到周围公众反对的原因之一。文中介绍了二嗯英的危害、垃圾焚烧烟气中的二嗯英来源以及二嗯英的相关标准。以某垃圾焚烧发电厂为例,对垃圾焚烧烟气中的二嗯英类物质对人体健康的风险进行了评价,并提出了如何最大限度地减少垃圾焚烧处理过程中的二唔英排放量。