Recycling plastics from automotive shredder residues: a review

Automotive shredder residue (ASR) is an inevitable by-product of car recycling, i.e. removal of all liquids and hazardous or valuable components from the car and shredding of the hulk, followed by the recovery of steel, iron, and non-ferrous scrap. The European Union (EU) ELV Directive requires attaining higher recovery and recycling rates, resulting in a reduction of the amount of ASR going to landfill. The most plausible methods to achieve a considerable reduction of ASR are as follows: either recycling of separated materials and dismantled bulky parts, such as bumpers, dashboards, cushions, and front and rear windows, or else systematic sorting of the commingled and size-reduced materials, resulting from shredding. After a brief comparison of the actual situation in the EU, the USA, and Japan, the characteristics of actual ASR are reviewed, as well as some of the most prominent efforts made to separate and recycle specific fractions, such as polyolefins, ABS, or polyurethane. Attention is paid to some major players in the EU and to some of the pitfalls that besiege these ventures.     

Co-combustion of agricultural residues with coal in a fluidized bed combustor

Power generation from biomass is an attractive technology that utilizes agricultural residual waste. In order to explain the behavior of biomass-fired fluidized bed incinerator, biomass sources from agricultural residues (rice husk and palm kernel) were co-fired with coal in a 0.15m diameter and 2.3m high fluidized bed combustor. The combustion efficiency and carbon monoxide emissions were studied and compared with those for pure coal combustion. Co-combustion of a mixture of biomass with coal in a fluidized bed combustor designed for coal combustion increased combustion efficiency up to 20% depending upon excess air levels. Observed carbon monoxide levels fluctuated between 200 and 900 ppm with the addition of coal. It is evident from this research that efficient co-firing of biomass with coal can be achieved with minimal modifications to existing coal-fired boilers.     

An innovative example of herb residues recycling by gasification in a fluidized bed

A utilization way of herb residues is designed to convert herb residues to gas fuel in industrial-scale by a circulating fluidized bed gasifier in this paper. The product gas is used in the production of Chinese medicine, and the heat of the flue gas from the boiler can be used in herb residues drying to realize the energy recycling and no herb residues discharge. The gasification characteristics of herb residues in the circulating fluidized bed of 300 kg/h were investigated for about 200 h. The results indicated that the gas composition and tar yield were affected by biomass flow rate, equivalence ratio (ER), moisture content and char circulating. The lower heating value of product gas was 4–5 MJ/m³ using herb residues as feedstock. When mean biomass flow rate was at 5.5 kg m^?2 s^?1 and ER at 0.35, the product gas reached a good condition with lower heating value of 4.89 MJ/m³ and cold gas efficiency of 62.36%. When the moisture content changed from 12.5% to 18.7%, the concentrations of H₂, CO and CO₂ changed from 4.66% to 6.92%, 11.23% to 10.15%, and 16.55% to 17.82% respectively, and the tar content in gas decreased from 15.1 g/m³ to 14.4 g/m³ when the moisture content increased from 12.5% to 15.4%. There are metal oxides in the ash of herb residues, especially CaO, MgO, K₂O, Al₂O₃, and Fe₂O₃ which have obvious function on tar catalytic decomposition. The ash that attaches to the char particles can decrease the tar yield and improve the quality of gas after returning to the gasifier.     

Washing treatment of automotive shredder residue (ASR)

Worldwide, the amount of end-of-life vehicles (ELVs) reaches 50 million units per year. Once the ELV has been processed, it may then be shredded and sorted to recover valuable metals that are recycled in iron and steelmaking processes. The residual fraction, called automotive shredder residue (ASR), represents 25% of the ELV and is usually landfilled. In order to deal with the leachable fraction of ASR that poses a potential threat to the environment, a washing treatment before landfilling was applied. To assess the potential for full-scale application of washing treatment, tests were carried out in different conditions (L/S = 3 and 5 L/kg_TS; t = 3 and 6 h). Moreover, to understand whether the grain size of waste could affect the washing efficiency, the treatment was applied to ground (<4 mm) and not-ground samples. The findings obtained revealed that, on average, washing treatment achieved removal rates of more than 60% for dissolved organic carbon (DOC), chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN). With regard to metals and chlorides, sulphates and fluoride leachable fraction, a removal efficiency of approximately 60% was obtained, as confirmed also by EC values. The comparison between the results for ground and not-ground samples did not highlight significant differences.     

Review of Italian experience on automotive shredder residue characterization and management

Automotive Shredder Residue (ASR) is a special waste that can be classified as either hazardous or non hazardous depending on the amount of hazardous substances and on the features of leachate gathered from EN12457/2 test. However both the strict regulation concerning landfills and the EU targets related to End-of-Life Vehicles (ELVs) recovery and recycling rate to achieve by 2015 (Directive 2000/53/EC), will limit current landfilling practice and will impose an increased efficiency of ELVs valorization. The present paper considers ELVs context in Italy, taking into account ASRs physical–chemical features and current processing practice, focusing on the enhancement of secondary materials recovery. The application in waste-to-energy plants, cement kilns or metallurgical processes is also analyzed, with a particular attention to the possible connected environmental impacts. Pyrolysis and gasification are considered as emerging technologies although the only use of ASR is debatable; its mixing with other waste streams is gradually being applied in commercial processes. The environmental impacts of the processes are acceptable, but more supporting data are needed and the advantage over (co-)incineration remains to be proven.     

An examination of the exothermic nature of fluidized bed combustion (FBC) residues

Circulating fluidized bed combustion (CFBC) ashes from nine operational periods at the 183 MWe CFBC boiler at Point Aconi were examined for exothermic behaviour. Bed ashes and fly ashes were investigated using a Parr 1455 solution calorimeter. Limited tests were also carried out with additional samples from Point Aconi and from the 160 MWe TVA Bubbling Fluidized Bed Combustion boiler to evaluate the effects of particle size and aging on exothermic behaviour. For the Point Aconi ashes, heat release from the bed ash ranged from 11 to 52 J/g, and the maximum heat release rates ranged from 0.06 to 0.17 J/g/s. For the fly ash heat release varied from 114 to 187 J/g and the maximum heat release rates ranged from 0.8 to 1.9 J/g/s. In the fly ash samples, 50% or more of available CaO was converted to Ca(OH)₂, while for the bed ash a third or less of the CaO was converted to Ca(OH)₂. The exothermicity of the bed ash is directly proportional to the CaO content of the ash. However, this is not true for the fly ash. The exothermic behaviour of fresh FBC ash appeared to be greatly reduced by exposure in air over a 48-h period. Another conclusion of this work is that particle size effects the exothermic behaviour.     

循环流化床锅炉床温控制方法

就目前电厂循环流化床锅炉运行中存在的床温波动问题，讨论了导致床温波动的因素，并针对性地提出了控制床温的一些措施。     

Characterisation of polycyclic aromatic hydrocarbons in flue gas and residues of a full scale fluidized bed combustor combusting non-hazardous industrial waste

This paper studies the fate of PAHs in full scale incinerators by analysing the concentration of the 16 EPA-PAHs in both the input waste and all the outputs of a full scale Fluidized Bed Combustor (FBC). Of the analysed waste inputs i.e. Waste Water Treatment (WWT) sludge, Refuse Derived Fuel (RDF) and Automotive Shredder Residue (ASR), RDF and ASR were the main PAH sources, with phenanthrene, fluoranthene and pyrene being the most important PAHs. In the flue gas sampled at the stack, naphthalene was the only predominant PAH, indicating that the PAHs in FBC’s combustion gas were newly formed and did not remain from the input waste. Of the other outputs, the boiler and fly ash contained no detectable levels of PAHs, whereas the flue gas cleaning residue contained only low concentrations of naphthalene, probably adsorbed from the flue gas. The PAH fingerprint of the bottom ash corresponded rather well to the PAH fingerprint of the RDF and ASR, indicating that the PAHs in this output, in contrast to the other outputs, were mainly remainders from the PAHs in the waste inputs. A PAH mass balance showed that the total PAH input/output ratio of the FBC ranged from about 100 to about 2600 depending on the waste input composition and the obtained combustion conditions. In all cases, the FBC was clearly a net PAH sink.     

Conventional and fast pyrolysis of automobile shredder residues (ASR)

This work aims at comparing performance and product yields in conventional pyrolysis and fast pyrolysis of automotive shredded residues. In both processes, carbon conversion to gaseous and liquid products was more than 80%. Gas production was maximised in conventional pyrolysis (about 35% by weight of the initial ASR weight), while fast pyrolysis led to an oil yield higher than 55%. Higher heating values (HHV) of both conventional pyrolysis gas and fast pyrolysis oil increased from 8.8 to 25.07 MJ/Nm3 and from 28.8 and 36.27 MJ/kg with increasing pyrolysis temperature.     

Management status of end-of-life vehicles and characteristics of automobile shredder residues in Korea

An end-of-life vehicle (ELV) is dismantled to recover and recycle any re-usable parts, then shipped to the shredding facility for further recovery of iron with any remaining Automobile Shredder Residue (ASR) to be considered as wastes and to be disposed of by either thermal treatment or landfill. Overall ELVs management status in Korea, including recycling resulting from the dismantling processes, was surveyed using some questionnaires given to dismantlers and other available information to provide some feasible means for future treatment. The averaged recycle rate in the dismantling stage showed a value of 44% and the rest of an ELV was then compressed and transported to shredding companies to recover mainly the iron content which averaged 38.7% of the mass of a new vehicle. The non-ferrous metals such as copper, antimony, zinc and aluminum accounted for only 1.5%. The Shredder dusts (SDs) were found to be composed of light and heavy fluffs and soil/dust and amounted to 15.8% based on the mass of a new vehicle. Dumping of fluff and inorganic residues into a landfill site, however, will be restricted when new regulations are implemented to reduce the disposal amount to less than 5% of a new car as done in European countries and Japan. The detailed characteristics of SDs were investigated to provide an idea of how to treat them in order to meet a future expected enforcement.     

基于PLC的烟气循环流化床脱硫控制系统

介绍了烟气脱硫控制系统的设计与实现，重点描述了西门子S7—300可编程序控制器在系统中的应用和软件设计思路。     

Evaluation of waste pyrolysis characteristics in a pressurized fluidized bed reactor

To obtain the distribution of fuel components to gas, tar and char in a pressurized fluidized bed waste pyrolyzer, experiments were conducted with a laboratory scale fluidized bed reactor. Waste samples were fed batchwise from the top of the reactor into the fluidized bed of silica sand and pyrolyzed by nitrogen/nitrogen-O2 gas and the effects of pressure, particle size, heating rate and oxygen addition were investigated. In the case of rubber, the char yield tended to increase a little and the tar yield decrease over the pressure of 304-709 kPa. In comparison with the thermogravimetry data it was clearly demonstrated that the char yield from fluidized bed pyrolysis is much lower. A small amount of oxygen addition decreased both tar and char yields but its further increase did not affect them very much.     

Treatment of tar pond sludge in a circulating fluidized bed combustor

A series of tests to burn mixtures of tar pond sludge and coal was carried out using a mini‐circulating fluidized bed combustor (mini‐CFBC). During the tests, carbon dioxide, oxygen, carbon monoxide, sulfur dioxide, and nitrogen oxides in the flue gas were monitored continuously. Stack gas sampling was carried out for hydrochloric acid, metals, particulate matter, volatile organic compounds (VOCs), total hydrocarbons, semivolatile organic compounds (SVOCs), dioxins and furans (PCDD/Fs), and polychlorinated biphenyls (PCBs). Results showed that hydrochloric acid, mercury, particulate matter, PCDD/F, and metal concentrations were all below both the current limits and the gas‐release limits to be implemented in 2008 in Canada. The new 2008 emissions limits will reduce the maximum allowable concentrations of most pollutants by half. Thus, the maximum concentration for particulate matter will be 5 mg/m³ (from the current maximum concentration of 10 mg/m³);the maximum concentration for hydrochloric acid will be 5 mg/m³ (from 10 mg/m³); and the‐maximum concentration for dioxins and furans will be 0.032 ng/m toxic equivalent (from 0.08 ng/mcurrently). Sulfur capture efficiency was 89–91 percent. The percentage of fuel nitrogen converted to nitrogen oxides was of the order of 4.7 to 6.1, which is significantly lower than that of conventional pulverized coal‐fired boilers and well within the normal range for fluidized bed combustors (FBCs). PCB and polycyclic aromatic hydrocarbon (PAH) emissions levels were comparable or lower than levels reported in the literature for industrial‐scale FBCs. VOC concentrations were low except for benzene, for which the concentration was higher than that reported for pulverized coal‐fired utility boilers. In addition, carbon monoxide concentration was high at 1,200 to 2,200 parts per million. However, these carbon monoxide concentrations are typical of the mini‐CFBC firing coal. The trials showed that for 10 percent by weight tar pond sludge mixed with 90 percent by weight coal, the combustion was both stable and efficient. The tests demonstrated that CFBC technology is an environmentally sound option for eliminating tar pond waste sludge. © 2005 Wiley Periodicals, Inc.     

Gasification of waste plastics by steam reforming in a fluidized bed

The process of producing synthetic gas from waste plastics by steam reforming was investigated. To evaluate this process, the steam reforming of the oils derived from low-density polyethylene and polystyrene were carried out using a laboratory-scale fluidized bed of Ni-Al₂O₃ catalysts. The performance of gasification in terms of carbon conversion, gas yield, and gas compositions was examined. Although oils derived from plastics contain many kinds of heavy hydrocarbons and aromatics, they were well gasified at temperatures above 1023 K with a steam/carbon ratio of 3.5 and a weight hourly space velocity of 1 h⁻¹. The hydrogen content of the product gas was very high at approximately 72 vol% for polyethylene-derived oil and 68 vol% for polystyrene-derived oil. These compositions agreed well with the values calculated from chemical equilibrium.     

Treatment of anti-osmotic drug based pharmaceutical effluent in an upflow anaerobic fluidized bed system

During the production of Cephradine (a main constituent of anti-osmotic drug) a large quantity of concentrated effluent was produced. The main polluting compounds in this effluent are osmotic drug, acetic acid and ammonia. The feasibility of using a fluidized bed reactor under anaerobic condition with bioaugmentation to treat anti-osmotic drug based pharmaceutical effluent was evaluated. The main objective of the study was to show that bioaugmentation could be used to promote biological treatment to applications where conventional operation might be difficult or unfavourable. The effluent with chemical oxygen demand (COD) of 14000-18000 mg/l was treated in a fluidized bed reactor with a hydraulic retention time of 3-12 h. The reactor was unable to maintain consistent removal in conventional mode of operation due to an inability to retain and grow biomass. The COD reduction (%) after inoculation from a sequencing batch reactor was related to influent concentration, mass of inoculum and hydraulic retention time characterized by calculating the initial food to microorganism ratio. The role of volatile fatty acid (VFA) as cosubstrate was assessed with respect to COD reduction (%). Continuous COD reduction (%) attained a maximum value of 88.5% using bioaugmentation through periodic addition of acclimated cells every 2 days with 30-73.2 g of cells from an off-line enricher reactor.     

彭城电厂回流式循环流化床烟气脱硫系统及其运行分析

介绍了彭城电厂回流式循环流化床烟气脱硫的主要设计参数及工艺流程，并对运行中需注意的一些问题进行了分析与探讨。     

Status of recycling end-of-life vehicles and efforts to reduce automobile shredder residues in Korea

The present end-of-life vehicle (ELV) recycle rate and management status during the dismantling stage were investigated to aid the establishment of policies for the management of ELVs by surveying information and using the results gained from questionnaires given to dismantlers. The average recycle rate at the dismantling stage was 44% of the mass of a new vehicle and the rest of the ELV was then compressed and transported to shredding companies to recover mainly the iron content, which averaged 38.7% of the mass of a new vehicle. Nonferrous metals such as copper, antimony, zinc, and aluminum accounted for only 1.5%. The automobile shredder residues (ASRs) were composed of light and heavy fluffs and soil/dust and amounted to 15.8% based on the mass of a new vehicle. The dumping of fluff and inorganic residues in landfill sites, however, will be restricted when new regulations are implemented to reduce the disposal amount to less than 5% of a new car, as has been done in European countries and in Japan. The detailed characteristics of ASR were investigated to suggest appropriate means of treatment such as volume reduction or the utilization of thermal technologies to meet future expected enforcement. Also, some concerns on hazardous pollutant release such as that of dioxins while utilizing such thermal treatment methods were considered. The present on-going research and development projects to meet such future management targets are also introduced.     

烟气循环流化床-悬浮吸收工艺的应用

详述了烟气循环流化床悬浮吸收工艺的脱硫原理、工艺流程、系统组成,为类似老电厂烟气脱硫工程改造提供有益的设计和管理经验。     

Circulating fluidized bed incineration of industrial solid wastes

A pilot scale test facility of a circulating fluidized bed incinerator was established to generate design and operation data and help assess the technical feasibility for industrial applications. The use of high turbulence in the combustion zone and feeding an acid-capturer directly into the incinerator to absorb acid gases eliminates the costly afterburner and scrubber. This paper presents some systematic incineration tests of uniform industrial wastes such as paper mill sludge cake, rubber waste and petroleum coke. Sludge cakes with high moisture and low heating values can be treated to a low emission level by co-firing with coal. The high superficial gas velocity has improved combustion efficiency but increases NO_x emissions. However, sulphur content has almost no influence on sulphur retention. The problems of CO/NO_x emissions and circulation stability are also discussed.