粉煤灰的资源化利用与循环经济

阐述了燃煤固体产物粉煤灰的形成过程及其物理和化学特性,并对其利用潜力进行了系统评价,提出了建立粉煤灰资源化利用和发展循环经济相结合的发展模式。     

Composite materials based on wastes of flat glass processing

Glass mirrors scrap and poly (vinyl) butiral waste (PVB) obtained from flat glass processing plants were investigated as raw materials to produce composites. The emphasis was on studying the influence of milled glass mirror waste contents on properties of composites produced with PVB. The characterization involved: elongation under rupture, water absorption, tensile strength and elastic modulus tests. The results showed that the composite containing 10 wt% of filler powder had the best properties among the compositions studied. The influence of the time of exposure in humid atmosphere on the composite properties was investigated. It was found that the admixture of PVB iso-propanol solution to the scrap of glass mirrors during milling provided stabilization of the properties of the composites produced.     

Attenuation of hydrogen sulfide at construction and demolition debris landfills using alternative cover materials

The attenuation of H₂S emissions by various landfill cover materials was evaluated using both laboratory and field experiments. The results demonstrated that cover materials consisting of selected waste products (compost and yard trash) and soils amended with quicklime and calcium carbonate effectively attenuated H₂S emissions and detectable H₂S emissions were only encountered in a testing plot using a sandy soil cover (average emission rate was 4.67 × 10^?6 mg m^?2 s^?1). H₂S concentration profiles in the cover materials indicated that H₂S was removed as it migrated through the cover materials. At the same depth in the testing area, the H₂S concentration in the sandy soil field plot was always higher than that of other testing plots because the sand (a) demonstrated less ability to remove H₂S and (b) exhibited a higher H₂S concentration at the base of the cover. Laboratory experiments confirmed these observations, with a combination of physical adsorption, chemical reactions, and biological oxidation, accounting for the enhanced removal. In addition to removal, the results suggest that some of the cover materials reduced H₂S generation by creating less favorable conditions for sulfate-reducing bacteria (e.g., high pH and temperature).     

再生聚丙烯的洁净化和高质化应用

聚丙烯以其优异的机械性能、高的性价比和多重改性方式成为重要的通用树脂之一,这些产品废弃后产生了种类繁多和数量巨大的再生聚丙烯.通过将再生聚丙烯根据性能和来源进行分类,然后分类阐述各再生聚丙烯物料特点,结合再生聚丙烯改性方式,为高质化应用提出方向.     

Formation of recycled plastics from depolymerized monomers derived from waste fiber-reinforced plastics

To develop a new method for the chemical recycling of plastics, we examined the formation of recycled polymers from the recovered monomeric materials of solubilized waste fiber-reinforced plastics (FRP) under supercritical alcoholic conditions. Treatment of waste FRP with supercritical MeOH resulted in the formation of monomeric organic compounds that mainly contained dimethyl phthalate (DMP) and propylene glycol. The presence of these materials was confirmed by gas chromatography and nuclear magnetic resonance analyses and they were mixed with new DMP and glycols in various ratios to form unsaturated polyesters. The polymerization progressed successfully for all mixing ratios of the recovered and new DMP. Hardness tests on these recycled polymers indicated that the polymer made from a 1:1 mixture of recovered and new dimethyl phthalate had almost the same level of hardness as the polymers made from new materials. We also examined the formation of recycled FRP by using glass fibers and monomeric materials recovered through the present depolymerization method. Chemical Feedstock Recycling & Other Innovative Recycling Techniques 6     

Assessment of the methane oxidation capacity of compacted soils intended for use as landfill cover materials

The microbial oxidation of methane in engineered cover soils is considered a potent option for the mitigation of emissions from old landfills or sites containing wastes of low methane generation rates. A laboratory column study was conducted in order to derive design criteria that enable construction of an effective methane oxidising cover from the range of soils that are available to the landfill operator. Therefore, the methane oxidation capacity of different soils was assessed under simulated landfill conditions. Five sandy potential landfill top cover materials with varying contents of silt and clay were investigated with respect to methane oxidation and corresponding soil gas composition over a period of four months. The soils were compacted to 95% of their specific proctor density, resulting in bulk densities of 1.4-1.7 g cm⁻³, reflecting considerably unfavourable conditions for methane oxidation due to reduced air-filled porosity. The soil water content was adjusted to field capacity, resulting in water contents ranging from 16.2 to 48.5 vol.%. The investigated inlet fluxes ranged from 25 to about 100 g CH₄ m⁻² d⁻¹, covering the methane load proposed to allow for complete oxidation in landfill covers under Western European climate conditions and hence being suggested as a criterion for release from aftercare. The vertical distribution of gas concentrations, methane flux balances as well as stable carbon isotope studies allowed for clear process identifications. Higher inlet fluxes led to a reduction of the aerated zone, an increase in the absolute methane oxidation rate and a decline of the relative proportion of oxidized methane. For each material, a specific maximum oxidation rate was determined, which varied between 20 and 95 g CH₄ m⁻² d⁻¹ and which was positively correlated to the air-filled porosity of the soil. Methane oxidation efficiencies and gas profile data imply a strong link between oxidation capacity and diffusive ingress of atmospheric air. For one material with elevated levels of fine particles and high organic matter content, methane production impeded the quantification of methane oxidation potentials. Regarding the design of landfill cover layers it was concluded that the magnitude of the expected methane load, the texture and expected compaction of the cover material are key variables that need to be known. Based on these, a column study can serve as an appropriate testing system to determine the methane oxidation capacity of a soil intended as landfill cover material.     

Modelling piloted ignition of wood and plastics

To gain insight in the startup of an incinerator, this article deals with piloted ignition. A newly developed model is described to predict the piloted ignition times of wood, PMMA and PVC. The model is based on the lower flammability limit and the adiabatic flame temperature at this limit. The incoming radiative heat flux, sample thickness and moisture content are some of the used variables. Not only the ignition time can be calculated with the model, but also the mass flux and surface temperature at ignition. The ignition times for softwoods and PMMA are mainly under-predicted. For hardwoods and PVC the predicted ignition times agree well with experimental results. Due to a significant scatter in the experimental data the mass flux and surface temperature calculated with the model are hard to validate. The model is applied on the startup of a municipal waste incineration plant. For this process a maximum allowable primary air flow is derived. When the primary air flow is above this maximum air flow, no ignition can be obtained.     

Trends in waste plastics and recycling

Zero emission is an ambitious project aimed at the conversion of the conventional top-down or one-directional flow type production systems of modern society to those of a recycling type. The basic idea underlying this project is to understand in detail the material flow mechanism in a particular segment of society and to evaluate the transformability of the hitherto one-directional types of process into recycling types. The authors, members of the Zero-Emission Research Group of Japan, are investigating the material flow of plastics in Japan. The present work describes the features of this project, as well as the results obtained so far. Received: May 28, 1998 / Accepted: October 16, 1998     

Neutralization of an extremely acidic sludge and stabilization of heavy metals in flyash aggregates

An extremely acidic, heavy metal-rich sludge (pH=-1.2) was scrubbed with a Class-F fly ash in order to simultaneously neutralize the acidity and stabilize the heavy metals contained in both wastes. This paper outlines the leaching behavior of the aggregate material generated by scrubbing. For proper fly ash/sludge ratios, the fly ash acted as an outstanding neutralizer for the acidic waste. Leaching of heavy metals from the aggregate samples was below the environmental limits within a pH range between 3 and 9. Subsequent washing of the leached aggregate with acidic CALWET solutions did not result in an additional release of heavy metals. It is proposed that coordinative bonding of the metal cations onto neutral surface sites and electrostatic adsorption led to stabilization of the heavy metals within the aggregate structure below hydrolysis pHs.     

废旧塑料综合利用技术的应用

废旧塑料的回收利用是环境污染控制所面临的一个重要课题,近年来,人们在这方面进行了大量的研究工作,取得了很多成果.详细叙述了国内外废旧塑料回收处理的方法,分析了我国在废旧塑料回收利用方面的现状及存在的问题,并对如何进一步开展废旧塑料回收利用工作提出了一系列切实可行的建议.