第二代城市生活垃圾焚炉—气化熔融炉

本文介绍了一种新的城市生活垃圾焚烧处理方式-气化熔融炉的工艺过程,国外发展现状和研究进展.在分析国内外城市生活垃圾特点的基础上,提出了一种适合于我国垃圾现状的气化熔融处理方式.     

利用钢铁生产吹氧法的垃圾气化与熔融系统

利用高温冶金炼铁、炼钢技术,开发了一种新型的垃圾气化与熔融系统.住友金属开发的这种体系具有下列基本概念:用顶吹和侧吹氧枪实现稳态生产,产生无二恶英的高热值净化气和高质量的炉渣.系统的基本概念用一台规模为2 t/d的城市垃圾处理小型炉得到澄清.利用顶吹氧枪,由于在炉子上部产生均匀气流,从而可稳定炉子顶气的成分.顶吹氧枪的使用可防止粗粉尘(尺寸＞0.1 mm)的飞散,使熔化的粉尘均匀沉积在炉子内壁上.内壁上形成的粉尘沉积层不但可防止粉尘飞散,而且能保护炉子内壁.在2t/d规模小型炉试验结果的基础上,进一步启动了一台20 t/d规模的示范炉.示范炉和小型炉一样不用焦炭,能稳定地气化和熔化城市垃圾.由于在高温还原气氛下气化和快速冷却,结果可产生无二恶英的高热值净化气.垃圾中的灰分在高温还原气氛下熔融,得到不含重金属的高质量炉渣.     

城市生活垃圾自热焚烧新技术

介绍了一种城市生活垃圾直接气化熔融焚烧方法--垃圾自热焚烧新方法的工艺及特点.     

城市生活垃圾高温富氧空气熔融焚烧技术研究

针对我国城市生活垃圾的特性及垃圾焚烧过程中产生的二次污染,结合高温富氧空气的熔融燃烧机理,提出了以高温富氧空气为氧化剂的城市生活垃圾熔融焚烧技术,给出了该技术的工艺流程,剖析了其关键技术,并着重分析了其低污染特性.     

关于城市生活垃圾堆肥处理的思考

通过对垃圾的危害,环境保护政策,生活垃圾的处理方法比较,垃圾成分的变化,垃圾分类收集的推广和生态农业发展等诸方面的论述,说明城市生活垃圾堆肥处理方法的可行性,指出垃圾堆肥处理方法实施中要注意的一些问题和看法。     

城市垃圾填埋场渗沥液处理

介绍了城市垃圾填埋场渗沥液的产生产特点，结合垃圾填埋技术和渗沥液处理方案，举例对各种具体的处理方法的工艺特点及相应要术进行了分析讨论。     

焦炉处理城市垃圾新技术

现有的垃圾焚烧、热解技术,存在投资大,二次污染严重的问题.在分析垃圾构成和垃圾热解技术的基础上,提出采用焦炉工艺处理垃圾,实现垃圾与煤共焦化.针对城市垃圾的特点,提出切实可行的工艺路线.     

城市生活垃圾综合循环利用处理系统

本系统在综合分析比较现有城市生活垃圾处理技术的基础上，结合中国国情，提出了将城市生活垃圾处理对策前移，通过优化填埋法，焚烧法，堆肥法，BPY热解法的工艺组合，设计了人机一体化的“城市生活垃圾综合循环利用处理系统”（以下简称WRS）、WRS特别实用于中国中小城市的生活垃圾的“无害化、资源化、减量化”处理，由于其投资省、运行成本低，在中国具有广阔的发展和推广前景。     

城市生活垃圾资源化研究

主要介绍了我国城市生活垃圾的处理现状及存在的问题,总结了我国城市生活垃圾的资源潜力,提出了城市生活垃圾资源化的措施,为实现我国城市生活垃圾资源化提供了新的思路。     

水泥窑炉协同处理城市垃圾研究进展

水泥窑炉处理危险废物和城市生活垃圾是众多处理方法中实现减量化、无害化和资源化最好的方法之一。水泥窑焚烧垃圾可以利用垃圾的热量节省燃料,同时垃圾燃烧后的灰渣可以替代原料。另外,CaO和过渡性熟料矿物对有害物质的不良作用有抑制作用,也可以减少二恶英等有害气体的排放。     

Municipal Solid Waste Recycling Issues

Municipal solid waste (MSW) recycling targets have been set nationally and in many states. Unfortunately, the definitions of recycling, rates of recycling, and the appropriate components of MSW vary. MSW recycling has been found to be costly for most municipalities compared to landfill disposal. MSW recycling policy should be determined by the cost to the community and to society more generally. In particular, recycling is a good policy only if environmental impacts and the resources used to collect, sort, and recycle a material are less than the environmental impacts and resources needed to provide equivalent virgin material plus the resources needed to dispose of the postconsumer material safely. From a review of the existing economic experience with recycling and an analysis of the environmental benefits (including estimation of external social costs), we find that, for most communities, curbside recycling is only justifiable for some postconsumer waste, such as aluminum and other metals. We argue that alternatives to curbside recycling collection should be explored, including product takeback for products with a toxic content (such as batteries) or product redesign to permit more effective product remanufacture.     

Unit Weight of Municipal Solid Waste

The unit weight of municipal solid waste (MSW) is an important parameter in engineering analyses of landfill performance, but significant uncertainty currently exists regarding its value. A careful review of reliable field data shows that individual landfills have a characteristic MSW unit weight profile. Based on in situ unit weight data and trends observed in large-scale laboratory tests, a hyperbolic relationship was developed to represent this characteristic MSW unit weight profile. Within the context of this characteristic profile, landfill-specific values of MSW unit weight depend primarily on waste composition, operational practices (i.e., compaction, cover soil placement, and liquids management), and confining stress. Guidance is provided for developing landfill-specific MSW unit weight profiles, including procedures for performing large-scale tests for in situ measurement of MSW unit weight at a landfill.     

Shear Strength of Municipal Solid Waste

A comprehensive large-scale laboratory testing program using direct shear (DS), triaxial (TX), and simple shear tests was performed on municipal solid waste (MSW) retrieved from a landfill in the San Francisco Bay area to develop insights about and a framework for interpretation of the shear strength of MSW. Stability analyses of MSW landfills require characterization of the shear strength of MSW. Although MSW is variable and a difficult material to test, its shear strength can be evaluated rationally to develop reasonable estimates. The effects of waste composition, fibrous particle orientation, confining stress, rate of loading, stress path, stress-strain compatibility, and unit weight on the shear strength of MSW were evaluated in the testing program described herein. The results of this testing program indicate that the DS test is appropriate to evaluate the shear strength of MSW along its weakest orientation (i.e., on a plane parallel to the preferred orientation of the larger fibrous particles within MSW). These laboratory results and the results of more than 100 large-scale laboratory tests from other studies indicate that the DS static shear strength of MSW is best characterized by a cohesion of 15?kPa and a friction angle of 36° at normal stress of 1?atm with the friction angle decreasing by 5° for every log cycle increase in normal stress. Other shearing modes that engage the fibrous materials within MSW (e.g., TX) produce higher friction angles. The dynamic shear strength of MSW can be estimated conservatively to be 20% greater than its static strength. These recommendations are based on tests of MSW with a moisture content below its field capacity; therefore, cyclic degradation due to pore pressure generation has not been considered in its development.     

Compaction Characteristics of Municipal Solid Waste

Compaction characteristics of municipal solid waste (MSW) were determined in the laboratory and in the field as a function of moisture content, compactive effort, and seasonal effects. Laboratory tests were conducted on manufactured wastes using modified and 4X modified efforts. Field tests were conducted at a MSW landfill in Michigan on incoming wastes without modifications to size, shape, or composition, using typical operational compaction equipment and procedures. Field tests generally included higher efforts and resulted in higher unit weights at higher water contents than the laboratory tests. Moisture addition to wastes in the field was more effective in winter than in summer due to dry initial conditions and potential thawing and softening of wastes. The measured parameters in the laboratory were γdmax-mod = 5.2?kN/m3, wopt-mod = 65%, γdmax-4×mod = 6.0?kN/m3, and wopt-4×mod = 56%; in the field with effort were γdmax-low = 5.7?kN/m3, wopt-low = 70%; γdmax-high = 8.2?kN/m3, and wopt-high = 73%; and in the field with season were γdmax-cold = 8.2?kN/m3, wcold = 79.5%, γdmax-warm = 6.1?kN/m3, and wwarm = 70.5%. Soil compaction theory was reasonably applicable to wastes with the exception that the Gs of waste solids increased with compactive effort resulting in steep degree of saturation curves and low change in wopt between efforts. Moisture addition to wastes during compaction increased the workability, the unit weight, and the amount of incoming wastes disposed, and reduced the compaction time. The combined effects have significant environmental and economic implications for landfill operations.     

Constitutive Model for Municipal Solid Waste

Municipal solid waste (MSW) is a refuse composed of various materials with different properties. Some of the components are stable while others degrade as a result of biological and chemical processes. These aspects impart to MSW a complex behavior that has been modeled, with many limitations, within the concepts of soil mechanics. In this paper, a framework to model the MSW mechanical behavior is proposed based on results from laboratory tests, such as triaxial compression and confined compression of large samples. It is suggested that two different effects command MSW mechanical behavior: (a) the reinforcement of MSW by synthetic fibers (composed by many types of polymers) and (b) the behavior of the MSW paste, without fibers. Accordingly, two distinct frameworks were used to represent the main MSW characteristics: (a) a critical state framework for MSW paste and (b) an elastic perfectly plastic framework for waste fibers, with a time lag for fiber loading (function fm). The proposed model is capable of reproducing quite well the results obtained from triaxial and confined compression tests performed in the laboratory as well as the settlement recorded in a sanitary landfill.     

Air Permeability of Waste in a Municipal Solid Waste Landfill

The permeability of compacted municipal solid waste in a landfill with respect to air (or gas) flow was estimated using a short-term air injection test. Air was added to 134 vertical wells installed at three different depths at flow rates in the range of 0.14?–1.4?m3?min?1 and the corresponding steady state pressures were recorded. The permeability of the waste with respect to airflow (described here as the air permeability) was estimated for different anisotropy ratios (kr/kz = 1, 10, and 100) using a steady state, two-dimensional, axisymmetric analytical fluid flow model in conjunction with the measured flow and pressure data. The air permeability of landfilled municipal solid waste modeled as an isotropic medium was found to range from 1.6×10?13 to 3.2×10?11?m2. The estimated air permeability results were on the low end of values previously applied to model landfill gas flow. Estimated air permeability decreased significantly with increasing waste depth. The lower permeability encountered in the deeper layers was primarily attributed to the lower porosity of the waste caused by higher overburden pressures and higher moisture content of waste in deeper layers of the landfill than in shallow layers. The results suggest that multiple wells screened at different depths provide greater control of air distribution within the landfill. Leachate recirculation was documented to impact the ability to add air. In addition to limitations posed by standing water in many of the deeper wells, waste exposed to leachate recirculation was found to be significantly less permeable to air when compared to original conditions.