废弃混凝土回收制备轻质混凝土的实验研究

回收废弃混凝土经破碎、磨细后,匹配适量氢氧化钙、水泥和水,在高温饱和水蒸气环境中反应固化,经系统优化实验,获得了具有显著力学性能的块状制品,进而引入铝粉作为发气剂,制备出轻质多孔加气混凝土材料,产品容重、导热系数等性能指标均符合相应国家标准对BO6级加气混凝土的质量要求.研究结果对废弃混凝土的综合回收利用及加气混凝土生产实践具有一定理论指导意义.     

废弃塑料回收方法概述

塑料材料在人类社会与生产生活中发挥着越来越重要的作用。塑料的过度使用不仅带来日益严重的环境污染问题,同时也造成了大量的资源浪费。因此,废弃塑料回收与利用技术和生产工艺的开发不仅具有重大社会意义和生态意义,同时具有非常大的经济效益。主要介绍了废弃塑料的来源,结合具体案例对当前常用的塑料回收方法进行介绍,指出了不同回收利用方式的优势与挑战,同时对该领域的发展前景进行展望。     

废弃塑料的回收利用

论述了目前废弃塑料回收利用方面的发展现状,介绍了聚丙烯、聚乙烯、聚对苯二甲酸乙二醇酯、聚氯乙烯、聚苯乙烯等废弃塑料的回收利用方法,以实现保护人类健康和减少环境污染和资源循环使用的目的。     

中国废弃塑料行业状况与回收处置原则初探

中国废弃塑料情况及回收。     

利用废弃混凝土制备再生胶凝材料

为了提高废弃混凝土再生资源的利用效率,提出实现各组分高效再生利用技术路线和方法.将分离出来的水泥石组分经过低温煅烧处理,制备得到可再次水化并形成胶凝能力的再生胶凝材料.利用X射线衍射、扫描电子显微镜、力学测试等手段对其矿物组成、水化硬化过程等进行了研究.实验结果表明:不同煅烧温度下制备得到的再生胶凝材料矿物组成及其结构不同,使其水化活性存在差异.其中在650℃煅烧得到的再生胶凝材料以不完全结晶的β-C2S矿物相为主要成分,具有优良的水化胶凝能力.     

废弃塑料的化学回收：方法，现状及前景展望

塑料产品具有成本低、密度小、耐用性强和性能可调等优点,与人们的衣食住行密不可分。但是,由于塑料的降解性能较差和缺乏完备的回收机制,一系列的生态问题也随之而来。伴随着能源危机的加剧和材料经济效率的低下,探寻废弃塑料的回收再利用途径是实现可持续发展的必要条件。传统的物理回收方法存在着适用条件有限和聚合物性能降低等问题,而化学回收在理论上可对塑料进行分子层面的拆解与重组,形成单体或其他高附加值的产物。本文立足于塑料回收的化学方法,对化学回收的行业现状和研究进展进行总结梳理,分析了对应的回收机理和制约回收的因素,为开发塑料的化学回收再利用技术提供一定的参考。通过开发新型的催化工艺和设计高效的反应体系,化学回收或可成为推动循环塑料经济发展的关键。     

废弃印刷线路板热解回收研究进展

综述了近年来国内外废弃印刷线路板热解回收的研究现状,着重介绍了废线路板热解的产物利用、影响因素、动力学和机理等方面的研究进展,讨论了该技术亟待解决的问题和未来的研究方向.     

废弃黏土砖的回收再利用

对某钢厂废弃黏土砖进行拣选、破碎、筛分、除铁、均化等综合再生技术得到粒度分别为8～5、5～3、3～1和1～0.5 mm的再生黏土颗粒料,再以此为骨料,以一级矾土为细粉,矾土水泥为结合剂,石英、活性氧化铝微粉、二氧化硅微粉为添加剂,研制出了高强浇注料C-1300、高铝浇注料C-1400、高强低水泥浇注料C-1450;以高铝矾土为细粉,水玻璃或矾土水泥为结合剂,石英、氟硅酸钠为添加剂,研制出了耐酸喷涂料MS、中重质喷涂料FN-130和重质喷涂料FN-140。检测结果表明:研制的6种产品性能指标优越,超过现有同类产品。废砖利用分析表明:将废弃黏土砖回收再利用,将产生较大经济效益,同时又节能环保。     

运用信息化手段提高建筑废弃混凝土回收利用水平的策略

介绍了建筑废弃混凝土产生及回收利用现状,提出建立建筑废弃混凝土回收利用信息管理系统或运用区块链技术两种信息化手段加强回收利用管理的策略,并对应用上述策略的效果进行了总结.     

搅拌站废弃泥浆循环利用方法的研究

分析了搅拌站废弃泥浆的性质,通过试验研究了掺废弃泥浆混凝土的工作性能和力学性能.在此基础上,提出了废弃泥浆的循环利用方法,即:将废弃泥浆作为混凝土生产原材料,以废弃泥浆中水溶液等量取代混凝土拌合水使用,以废弃泥浆中的不溶物(固体颗粒)等量取代水泥使用,且以不溶物的含固取代量为废弃泥浆用量的控制指标,并要求含固取代量≤2％.     

废旧塑料的再生利用

废旧塑料不仅污染了环境,而且也极大地浪费了资源.对废旧塑料在能量回收、用于油品生产及制取新材料等方面的进展情况进行了介绍和评述.废旧塑料的再生利用已成为急待解决的问题,有效的废旧塑料再生利用对于治理白色污染具有重要作用.     

Recycling Nylon 6 Carpet to Caprolactam

The recycling of nylon 6 carpet via depolymerization provides the potential for an environmentally benign new process to produce world-class caprolactam. This article describes the depolymerization of nylon 6 carpet in the presence of steam under medium pressure (800-1500 kPa, 100-200 psig). A small laboratory apparatus was set up to demonstrate the feasibility of the scheme. A total of eight runs were carried out using ～180 g of pellitized carpet and 2-6 g/min steam (at 101-1500 kPa, 0-200 psig, and 300-340°C). In our best run at 340°C, 6 g/min of steam, and 1500 kPa (200 psig) for 3 h, we obtained a 95% yield of crude caprolactam. The lactam purity was 94.4%, resulting in an overall 89.7% yield of caprolactam. The laboratory data were used to construct a computer model of the process for both batch and continuous-flow stirred reactors.     

Conversion of waste plastics into fuels: Recycling polyethylene in FCC

Low density polyethylene was dissolved into toluene and converted at 500 °C over three different commercial FCC catalysts in a laboratory Riser Simulator reactor. Short reaction-times up to 12 s were used. All the catalysts had qualitatively similar behaviors. The specific contribution of the polymer to the product slate of FCC was centered in hydrocarbons in the range of gasoline, with high aromatic content and highly olefinic C₃–C₄ gases. Saturated C₄–C₅ products were mainly isoparaffins. The additional coke formed by the polymer would make coke yields to increase moderately in relation to the standard operation. These facts confirmed that this recycling option, which is based on a proven technology, represents an interesting alternative to solve a major environmental problem.     

Towards a Structured Framework for Techno-Economic Analyses of Chemical Recycling Technologies

The role of chemical recycling (CR) as a valuable complementary strategy to mechanical recycling in closing the carbon cycle for carbon-containing waste is currently being discussed in political, economic, and social spheres. However, CR deployment is hindered by uncertainties regarding its environmental impacts and costs compared to conventional waste treatment and chemical production routes. While methods for assessing CR's environmental impacts are the focus of socio-political debates and investigations, techno-economic analyses (TEA) to evaluate costs of CR remain scarce. To contribute to a standardized framework for assessing the economic viability of CR technologies, this article draws on life cycle assessment and TEA literature to develop a six-stage TEA process for CR. A checklist is also presented to support transparent and comprehensive analyses.     

Recycling the insoluble residue from titania slag dissolution (tionite) in clay bricks

Tionite is the insoluble residue from the titania slag dissolution process for TiO₂ manufacturing. It is a fine-grained sludge consisting of rutile, anatase, amorphous phase and bassanite. Chemical composition is TiO₂ (ca. 50%), SiO₂ (ca. 30%) and minor Al, Ca, Mg, and Fe, plus residual sulfur, implying an acidic pH of waste. Moisture is about 35% of dry weight. The potential of tionite as colouring agent in clay bricks was appraised by admixing (up to 9%) either as-produced or neutralized tionite to four industrial clay bodies. The effect on technological behaviour was assessed by laboratory simulation of the industrial brickmaking process and determining working moisture, drying sensitivity, shrinkage and bending strength, water absorption, bulk density, efflorescence, and colour. The use of tionite is technologically feasible, with little adjustment of industrial cycle, and resulting brick performances depend remarkably on the composition and properties of clay bodies. Carbonate-rich bodies seem to be affected by tionite more during drying than during firing; carbonate-poor bodies range from little changes to consistent worsening of brick performances. No relevant changes of process and product parameters were found up to 3% tionite. Additions over 5% induce significant variations, such as increase of working moisture and water absorption, decrease of bulk density and bending strength. A definite and consistent improvement of this technological behaviour is achieved by using neutralized tionite. The yearly output of tionite could be entirely recycled by approximately four average-size brickworks adding about 3% of residue (dry weight).     

Beyond Plastics-to-Plastics to Waste-to-Products: Opportunities for Closing the Carbon Cycle via Chemical Recycling

The plastic crisis is a key driver for chemical recycling (CR), with focus placed on plastics circularity via Plastics-to-Plastics. This neglects its potential in enabling circularity for a wide range of carbon-containing waste and hinders a critical discussion of its broader contributions to decarbonizing the chemical sector. To address this gap, four CR routes and their integration in the conventional waste treatment and chemical production value chains are briefly reviewed, and reasons proposed for a focus expansion to Waste-to-Products to realize opportunities for closing the carbon cycle via chemical recycling.     

合成纤维的回收再利用技术

综述了废旧服装纺织品、废旧地毯、纤维增强复合材料、车用纺织品中合成纤维的各种回收再利用方法:详述了废旧涤纶及锦纶的化学回收及物理回收再利用技术;指出了我国合成纤维回收再利用的技术瓶颈,并建议我国应集中科研力量开展合成纤维回收再利用关键技术和设备的研究,建立合成纤维回收再利用示范基地。     

Prospective LCA of Waste Electrical and Electronic Equipment Thermo-Chemical Recycling by Pyrolysis

Waste electrical and electronic equipment (WEEE) is a particularly difficult waste to manage, characterized by hazardous and valuable chemicals. Emerging chemical recycling technologies are developed to unveil the possibility of sustainable treatment providing valuable resources from WEEE. This study develops a framework for prospective life cycle assessment (LCA) to explore a range of future scenarios in which the technology can be operated with low environmental impact. This is demonstrated in a case study focusing on plastics from WEEE, which are currently predominantly incinerated. The results reveal environmental benefits by WEEE treated via chemical recycling. In terms of climate change impacts, the best-case scenario of chemical recycling shows a reduction potential of 74 % compared to current treatment.     

Recycling of bottom ash from biomass combustion in porcelain stoneware tiles: Effects on technological properties,phase evolution and microstructure

This work aims to evaluate the use of bottom biomass ash as an alternative raw material in porcelain stoneware bodies. For this purpose, ash coming from a biomass thermoelectric power plant in Emilia-Romagna (Italy) was selected and its chemical, mineralogical and thermal properties determined. Data indicated its technological role as a flux, so it was introduced in a porcelain stoneware batch in partial replacement of feldspars and experimented at laboratory scale. A bottleneck, relative to the rheological behavior of the slips, was overcome by a slight deflocculant increase. The powder compacts were fired from 1000° to 1220 °C in order to follow the evolution of the technological properties, phase composition (XRPD-Rietveld) and microstructure (SEM). The introduction of ash allowed to lower the firing temperature by 20 °C, while keeping the technological properties comparable with those of the benchmark. Moreover, the mineralogical and microstructural data revealed different sintering kinetics.