Secondary Recycling Research Articles

Impact of Plastic Labelling, Coloring and Printing on Material Value Conservation in the Products of Secondary Recycling

Flexible plastic packaging which rejected or with low acceptance as raw materials for secondary recycling need relevant evidence and explanation of its cause, and then, need a systemic solution on how to increase the acceptance level. Coloring and printing on flexible plastic packaging were predicted as the significant source of impurity that reduces the value of plastic material at the end of packaging life cycle. Otherwise, optimum use of label or sticker as printing media for informational and promotional purpose on the packaging proposed as a key solution in material value conservation. The existing practices which focused on how to manage abundant plastic waste generation, replaced by a new paradigm which focused on how avoid waste generation by conserving the material value systematically. This research revealed that flexible plastic packaging materials with no color pigment and no printing ink were suitable for secondary recycling to produce high quality of recycled plastic pellets and leverage the selling price. Therefore, labelling on the surface of packaging that protect purity of the material can be considered as one of methods in the implementation of material value conservation on flexible plastic packaging. Another benefits of the implementation of material value conservation are to improve the utilization of virgin plastic and its recycled plastic pellets as raw materials with better quality.

Analysis of Impact and Tensile Properties of Recycled Polypropylene

The present research proposed to evaluate the tensile and impact properties of polypropylene originating from secondary recycling. The polymer chosen for the studies was polypropylene (PP) for its high application and availability. The tensile and impact tests were performed on virgin polypropylene, recycled polypropylene and mixtures of different proportions of both. Thus, for each sample, values of yield strength, elastic modulus, yield elongation and impact strength were obtained. The results of the averages obtained demonstrated that the tensile properties of virgin PP and recycled PP are similar, as well as those of the mixtures between both. Regarding the impact properties, it was observed that the energy absorbed by the recycled polymers is lower than that of the virgin polypropylene. Consequently, recycled polypropylene can replace virgin polypropylene in applications which are subjected to tension stress but not in those subjected it to impact.

Environmental and economic evaluation of pre-disaster waste management

Disaster waste management should be conducted in an environmentally and economically friendly manner, although disaster waste should be demolished and removed as soon as possible after a natural disaster. The aim of this study was to develop methods to conduct environmental and economic evaluation of pre-disaster waste management. A disaster waste management system consists of processes such as transportation, storage and separation at primary and secondary temporary storage sites, incineration, crushing, landfilling and recycling. Firstly, environmental and economic intensity data for each process was created via interview and literature surveys. Then, proposed methods was applied to the disaster waste management related to the 2016 Kumamoto Earthquakes, which occurred in Kumamoto Prefecture, Japan as the case study. Our results indicate that CO2 emission, SOx emission and cost from this disaster waste management method were 390 – 630 kt, 2,500 – 3,000 t and 630–710 kUSD. In particular, the SOx emission from such corresponded to 29 – 35 % of total annual SOx emission in Kumamoto Prefecture. This result revealed that the impact on regional air pollution via managing disaster waste is considerable.

Thermal degradation characteristics and products obtained after pyrolysis of specific polymers found in Waste Electrical and Electronic Equipment

Modern societies strongly support the recycling practices over simple waste accumulation due to environmental harm caused. In the framework of sustainable recycling of plastics from WEEE, pyrolysis is proposed here as a means of obtaining secondary value-added products. The aim of this study was to investigate the thermal degradation and the products obtained after pyrolysis of specific polymers found in the plastic part of WEEE, using thermogravimetric analysis and a pyrolizer equipped with a GC/MS. Polymers studied include ABS, HIPS, PC and a blend having a composition similar to that appearing in WEEE. It was found that, PC shows greater heat endurance compared to the other polymers, whereas ABS depolymerizes in three-steps. The existence of several polymers in the blend results in synergistic effects which decrease the onset and final temperature of degradation. Moreover, the fragmentation occurred in the pyrolyzer, at certain temperatures, resulted in a great variety of compounds, depending on the polymer type, such as monomers, aromatic products, phenolic compounds and hydrocarbons. The main conclusion from this investigation is that pyrolysis could be an effective method for the sustainable recycling of the plastic part of WEEE resulting in a mixture of chemicals with varying composition but being excellent to be used as fuel retrieved from secondary recycling sources.

Supply chain risk management for critical commodities: A system dynamics model for the case of the rare earth elements

We investigate mitigation strategies that potentially reduce the supply chain risk caused by exogenous interventions for critical commodities. We apply a system dynamics approach to examine the individual company’s reaction in the rare earth elements (REEs) supply chain to China’s introduction of export restrictions over a three-stage supply chain for 11 REEs, 10 semi-finished goods (SFG), and 21 finished goods (FG) between 2004 and 2015. We analyze how FG and SFG substitution, secondary recycling, supply extension and research and development (R&D) affect dynamic variables such as the price level, supply and demand on each stage to determine the effectiveness of each strategy for mining companies, SFG and FG producers.FG and SFG substitution show the highest potential for mitigating supply unavailability. Substitution is especially beneficial for FG producers. It also has the advantage of offering a quick development of alternatives for reducing REE supply unavailability risk. Due to the fact that the necessary infrastructure and technology are not available, secondary recycling shows only a low mitigation potential for FG companies. It was shown that mining companies do not invest proactively in supply capacities beyond China, as our simulation shows that it took 6 years until a new REE mine was opened. R&D is identified as a key element for REE mining companies, SFG and FG producers when it comes to developing alternative products and recycling techniques. Nonetheless, SFG producers face huge difficulties when trying to develop substitutes as alternative materials are not present.

Plasticwaste management and disposal techniques - Indian scenario

Plastic one of the major product which is versatile and having a wide range of application with very low cost and having large life duration makes it very important material of our life. In India itself the consumption of plastic has increased from 400 Tonn/year in 1992 to 5 Metric Tonn/year in 2005 to 8 Million tonnes/year in 2008 and expected to rise 24million tonnes by 2020. After completing its average life it is becoming the major problem for the environment as it is a non-degradable product. Advance research in the field of bio degradable/green plastic is going within a limit. Plastic waste or post-consumer plastic is being embarrassed us to intensifies the considerable demand for alternative disposal other than land filling. For plastic waste management the general ways practiced are reduce, reuse, and recycle (primary recycling) out of which later two are more followed by different means. Other alternatives are mechanical and chemical recycling. Mechanical recycling (secondary recycling) converts physical state of plastic waste into other similar products without any components structural change, whereas chemical recycling (tertiary recycling) is used to dissociate its chemical structure into its monomers or light hydrocarbons or to obtain hydrogen which can be used as an energy source. Various plastic waste management techniques and different types of reactors are discussed in this paper to ensure the waste management as well as the energy recovery from it. For better advancement in fuel oil recovery from plastic waste the effect of catalyst and the reaction conditions were also discussed in this paper.

A split concept for HRSG (heat recovery steam generators) with simultaneous area reduction and performance improvement

A split concept for boilers and heat recovery steam generators (HRSG), where flue gas recycling is required for controlling the maximal temperature, is proposed for reducing the heat exchange area and/or the recycling power requirements. The concept is demonstrated in the context of an HRSG of a pressurized oxy-coal combustion process, where the hot flue gas entering the HRSG is diluted by recycled flue gas to comply with the temperature constraint. The split concept proposes splitting the hot flue gas prior to dilution, and introducing the splitted fraction, with or without a secondary recycling stream, at an intermediate point in the HRSG. As a result, the split allows for lower recycling power requirements (lower diluent flowrate) and a smaller heat exchange area because the average temperature difference between the hot and cold streams in the heat exchanger is increased. Multi-objective optimization, for area and power requirements, is performed and the Pareto front is constructed. Results include a reduction by 37% without a change in the compensation power requirements, or a decrease in the power requirements by 18% (corresponding to 0.15 percentage points in cycle efficiency increase) while simultaneously reducing the area by 12%.

100 MWe급 순산소연소 발전소 보일러계통 공정설계 및 운전변수 민감도 예측

The oxy-fuel combustion is <TEX>$CO_2$</TEX> capture technology that uses mixture of pure <TEX>$O_2$</TEX> and recirculated exhaust as oxidizer. Currently some Oxy-fuel power plants demonstration project is underway in worldwide. Meanwhile research project for converting 125 MWe Young-Dong power plant to 100 MWe oxy-fuel power plants is progress. In this paper, 1 D process analytical approach was applied for conducting process design and operating parameters sensitivity analysis for oxy-fuel combustion of Young-Dong power plant. As a result, appropriate gas recirculation rates was 74.3% that in order to maintain normal rating superheater, reheater steam temperature and boiler heat transfer patterns. And boiler efficiency 85.0%, CPU inlet <TEX>$CO_2$</TEX> mole concentration 71.34% was predicted for retrofitted boiler. The oxygen concentration in the secondary recycle gas is predicted as 27.1%. Meanwhile the oxygen concentration 22.4% and moisture concentration 5.3% predicted for primary recycle gas. As the primary and secondary gas recirculation increases, then heat absorption of the reheater is tends to increases whereas superheater side is decreased, and also the efficiency is tends to decrease, according to results of sensitivity analysis for operating parameters. In addition, the ambient air ingression have a tendency to lead to decline of efficiency for boiler as well as decline of <TEX>$CO_2$</TEX> purity of CPU inlet.

Poly(ethylene terephthalate) waste derived chemicals as an antistripping additive for bitumen – An environment friendly approach for disposal of environmentally hazardous material

The increasing accumulation of poly(ethylene terephthalate) polymer and poor recycle/disposal practices have made them omnipresent and a major culprit for environmental pollution. Currently global research efforts are focused on primary and secondary recycling of PET waste or through landfills. Chemical recycling of PET through hydrolytic or aminolytic route has been attempted by many researchers however with limited end applications. In our investigations we have used PET waste as a synthon and chemically converted it through a new non-catalytic route into several benzamide derivatives. We have successfully tested them for antistripping performance in bitumen. Our results as elaborated in the paper indicate a comparable performance of the new chemistry products based on PET, to commercially used antistripping chemicals. Our research work thus opens a new route for the recycling of used PET in bituminous concrete roads which may help in alleviating a major environmental problem and disposal of waste PET polymer in large scale.

Assessment of the Flue Gas Recycle Strategies on Oxy-Coal Power Plants using an Exergy-based Methodology

While oxy-combustion CO2 capture was foreseen to have higher improvement potential than post-combustion a decade ago, research has not been carried out at the same pace since then and today, the latter exhibits higher technological maturity along with low energy penalty thanks to advanced process integration and solvents formulation. Thus, significant efficiency improvement is needed for the oxy-combustion route to be competitive with post-combustion for carbon capture on coal-fired power plants. In order to achieve such improvements, process integration at system level is required to assess the true energy savings potential of oxy-combustion. In this study, an exergy-based methodology is performed to compare various flue gas recirculation strategies on a state-of-the-art 1100 MWe gross oxy-fired power plant. Exergy analysis at unit operation level allows the identification of the location and the magnitude of the thermodynamic irreversibilities occurring in the process, leading to an enhanced understanding of the studied system. In addition to the reference case in which the secondary recycle is fully depolluted and dehydrated; three alternative flue gas recirculation options have been investigated. Among the studied strategies, recirculation of the secondary flow prior the regenerative heat exchanger with a high temperature particle removal device leads to the highest net plant efficiency. This option not only allows the minimal exergy losses in the boiler but also minimizes the flowrate going through the downstream depollution devices. The net plant efficiency obtained for this architecture is 38.0%LHV, which represents a 3% increase compared to the reference oxy-combustion plant. Comparing this figure to an air-fired power plant modeled with the same set of hypotheses, the energy penalty is 8.1%-pts.

Inter correlation between soil properties and growth of Azadirachta indica in various types of plantations of Jodhpur region (Rajasthan, India)

Physico-chemical properties do not vary rapidly for short distance in arid and semiarid regions in absence of plantation or some manual intervention. In case of barren land, it is difficult to enhance soil health and its productivity until and unless a large quantity of fertilizer and irrigation facilities are employed. Application of high dose of fertilisers and insecticides result in short-term increase in production, but it deteriorates the quality of soil and eventually reduces its productivity. There are hundreds of instances where trees improved the soil productivity. Microbial communities in soil have large impact on overall soil health due to production of secondary metabolites, nutrient recycling and decomposition. Various researches have demonstrated that Azadirachta indicaextract also acts as an antimicrobial agent and affects the structure and function soil microbial community. Therefore, it was critical to examine how its extract from different types of plantations becomes necessary to fully appreciate ramifications of its use on the environment for improving soil fertility. For the study, soil samples were collected from 53 different sites, in and around Jodhpur, Rajasthan, India, where A. indica was growing in different types of plantations. The data was analyzed for different properties of soil for separate types of plantations. Key words: Azadirachta indica, pH, electrical conductivity (EC), organic matters (OM), Kruskal Wallis test, sigmoidal growth modal.

Research of Cement Stabilized Secondary Recycling Materials

Cold recycling technology has been widely used in road maintenance projects. Many roads which have been reconstructed with cold recycling technology have emerged some diseases after a long-term used. In this condition, these roads can be rebuilt by secondary recycling technology. The microstructure characteristics of secondary recycled road materials after cement stabilizing were observed by SEM; then, material properties after being long-term used and secondary recycled were analyzed. CBR value and aggregate crush value are put forward for the evaluation indexes of secondary recycling. The unconfined compressive strength, splitting strength and modulus of cement stabilized secondary recycling materials are determined by laboratory tests. The results indicate that the existence of asphalt components lead the strength lower than ordinary base materials stabilized by cement. And temperature exerts an obviously influence on the compressive strength. Frost resistance, water stability and anti-erosion resistance are also determined by laboratory tests. The results indicate that the strength and pavement performance of cement secondary recycling materials can meet the requirements for base and sub base in asphalt pavement.

Recycling and recovery routes of plastic solid waste (PSW): A review

Plastic solid waste (PSW) presents challenges and opportunities to societies regardless of their sustainability awareness and technological advances. In this paper, recent progress in the recycling and recovery of PSW is reviewed. A special emphasis is paid on waste generated from polyolefinic sources, which makes up a great percentage of our daily single-life cycle plastic products. The four routes of PSW treatment are detailed and discussed covering primary (re-extrusion), secondary (mechanical), tertiary (chemical) and quaternary (energy recovery) schemes and technologies. Primary recycling, which involves the re-introduction of clean scrap of single polymer to the extrusion cycle in order to produce products of the similar material, is commonly applied in the processing line itself but rarely applied among recyclers, as recycling materials rarely possess the required quality. The various waste products, consisting of either end-of-life or production (scrap) waste, are the feedstock of secondary techniques, thereby generally reduced in size to a more desirable shape and form, such as pellets, flakes or powders, depending on the source, shape and usability. Tertiary treatment schemes have contributed greatly to the recycling status of PSW in recent years. Advanced thermo-chemical treatment methods cover a wide range of technologies and produce either fuels or petrochemical feedstock. Nowadays, non-catalytic thermal cracking (thermolysis) is receiving renewed attention, due to the fact of added value on a crude oil barrel and its very valuable yielded products. But a fact remains that advanced thermo-chemical recycling of PSW (namely polyolefins) still lacks the proper design and kinetic background to target certain desired products and/or chemicals. Energy recovery was found to be an attainable solution to PSW in general and municipal solid waste (MSW) in particular. The amount of energy produced in kilns and reactors applied in this route is sufficiently investigated up to the point of operation, but not in terms of integration with either petrochemical or converting plants. Although primary and secondary recycling schemes are well established and widely applied, it is concluded that many of the PSW tertiary and quaternary treatment schemes appear to be robust and worthy of additional investigation.

Cooperative Secondary Authorization Recycling

As enterprise systems, Grids, and other distributed applications scale up and become increasingly complex, their authorization infrastructures--based predominantly on the request-response paradigm--are facing the challenges of fragility and poor scalability. We propose an approach where each application server recycles previously received authorizations and shares them with other application servers to mask authorization server failures and network delays. This paper presents the design of our cooperative secondary authorization recycling system and its evaluation using simulation and prototype implementation. The results demonstrate that our approach improves the availability and performance of authorization infrastructures. Specifically, by sharing authorizations, the cache hit rate--an indirect metric of availability--can reach 70 percent, even when only 10 percent of authorizations are cached. Depending on the deployment scenario, the average time for authorizing an application request can be reduced by up to a factor of two compared with systems that do not employ cooperation.

Advances in synthesis of azeotropic distillation column sequences: internal secondary recycles

AbstractAn algorithm for automatic generation of sequences of distillation columns and decanters for separation of azeotropic mixtures has been developed (S.K. Wasylkiewicz, 54th Canadian Chemical Engineering Conference, paper No. 243, Calgary, October 2004; S.K. Wasylkiewicz, AIChE Spring National Meeting, paper No. 83e, Atlanta, GA, April 2005) where distillation boundaries can be crossed by moving them with pressure change, by exploring curvatures of distillation boundaries, or by liquid‐liquid splits in decanters. In the first step of the algorithm, open‐loop sequences are generated and primary recycles are automatically detected. Then, mass balances are calculated to finish the sequences. In this paper, we are focused on internal secondary recycles where species present in the sequence feed are introduced as separating agents. This can be a pure component produced somewhere downstream in the sequence or any other intermediate stream. On the basis of a broad knowledge about distillation regions and boundaries for the separated mixture, a preferred distillation region can be identified and a suitable recycle stream can be selected. These types of recycles can simplify tremendously, the whole sequence and reduce significantly the total cost of separation. We present in detail an example based on an industrial case where the internal secondary recycle was efficiently found and calculated during synthesis of column sequences by using the Split Generator in Distil and the mass balance calculation in MS Excel. Copyright © 2007 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Preparation and characterization of blends of recycled polystyrene with cassava starch

Secondary recycling is an alternative to solve at least part of the worldwide pollution problem caused by persistence of petrochemical plastic materials in the environment. In this work we report the secondary recycling of disposable polystyrene (PS) using cassava starch (Manihot esculenta Crantz) and a natural plasticizer extracted from a palm tree of the Amazon: Buriti (Mauritia flexuosa L.) oil. 13C-NMR spectroscopy reveals incorporation of the oil in the polymer matrix. Although phase separation had occurred, SEM depicts a very good dispersion of the thermoplastic starch (TPS) in the PS matrix with distinct domains. Thermal analyses indicate smaller thermal stability of the PS/TPS blends compared to PS and that possess intermediate characteristics between the pure PS and TPS, confirmed by DRX. Kinetic study shows a lowering of the activation energy for the thermal degradation of the blends.

A novel process integration, optimization and design approach for large-scale implementation of oxy-fired coal power plants with CO 2 capture

The widespread use of fossil fuels within the current energy infrastructure is considered as the largest source of anthropogenic emissions of carbon dioxide, which is largely blamed for global warming and climate change. At the current state of development, the risks and costs of non-fossil energy alternatives, such as nuclear, biomass, solar, and wind energy, are so high that they cannot replace the entire share of fossil fuels in the near future timeframe. Additionally, any rapid change towards non-fossil energy sources, even if possible, would result in large disruptions to the existing energy supply infrastructure. As an alternative, the existing and new fossil fuel-based plants can be modified or designed to be either “capture” or “capture-ready” plants in order to reduce their emission intensity through the capture and permanent storage of carbon dioxide in geological formations. This would give the coal-fired power generation units the option to sustain their operations for longer time, while meeting the stringent environmental regulations on air pollutants and carbon emissions in years to come. Currently, there are three main approaches to capturing CO 2 from the combustion of fossil fuels, namely, pre-combustion capture, post-combustion capture, and oxy-fuel combustion. Among these technology options, oxy-fuel combustion provides an elegant approach to CO 2 capture. In this approach, by replacing air with oxygen in the combustion process, a CO 2-rich flue gas stream is produced that can be readily compressed for pipeline transport and storage. In this paper, we propose a new approach that allows air to be partially used in the oxy-fired coal power plants. In this novel approach, the air can be used to carry the coal from the mills to the boiler (similar to the conventional air-fired coal power plants), while O 2 is added to the secondary recycle flow as well as directly to the combustion zone (if needed). From a practical point of view, this approach eliminates problems with the primary recycle and also lessens concerns about the air leakage into the system. At the same time, it allows the boiler and its back-end piping to operate under slight suction; this avoids the potential danger to the plant operators and equipment due to possible exposure to hot combustion gases, CO 2 and particulates. As well, by integrating oxy-fuel system components and optimizing the overall process over a wide range of operating conditions, an optimum or near-optimum design can be achieved that is both cost-effective and practical for large-scale implementation of oxy-fired coal power plants.

Impact of Basel convention on secondary-lead industry in economies in transition

Substantial trade in scrap and waste is not merely an exercise in waste management, but more importantly an element in efficient materials utilization, that has significant impact on the economy. In fact, it is an environmentally desirable and friendly activity and economically worthwhile pursuing for developing countries. Secondary recycling of materials and re-integrating them into the economy is crucial in reducing the overall demand for virgin materials for the developing economies. Scrap, ash and residues generated indigenously need to be recycled. Otherwise their disposal/dispersal will undoubtedly pose greater hazard in the future. Further, recycling of scraps and residues avoids degradation of the environment. Environmental control and monitoring in lead operations will require assiduous implementation to ensure that transportation, handling and processing are managed with greater care and the entire operation is environmental friendly.

Welfare gains from aluminium recycling in the USA

In this paper we estimate a flexible form cost function of the aluminium industry in the USA and use our estimates to obtain derived demand curves for aluminium inputs such as electricity and bauxite. We then calculate the welfare gains arising from decreased energy use when the level of secondary recycling is increased. The process is repeated for several model specifications. All of our tests, however, yield similar results and indicate that substitution of scrap for only 5% of the bauxite presently used in US aluminium manufacturing would result in annual savings of close to a quarter of a billion dollars.

Secondary recycling of plastics

Increasing environmental pressures may result in the establishment of a secondary plastics recycling industry. This paper reviews the present position and describes principal routes for secondary recycling of plastics which are likely to be in use in future.