Materials recycling

Basically, there are two ways of recycling, namely, material recycling and recycling via a chemical reaction, the latter using mostly thermal processes. Of course, these two methods can be further subdivided. There are monographs on the basic aspects of recycling of plastics (116,117). 

From articles used in electronics, high value precious metals, electronic components and glass electronic components are separated from the plastic housings, which have been generally sent to landfill because there was no economical process to separate the plastics to sufficient purity to enable the plastics to be recycled. The housings are generally made of mixed plastics such as ABS and PC (118). Methods suitable for the recycling of ABS resins have been developed (81,118-120). 

The recycled ABS resin obtained by recycling an ABS resin can be formed into articles by injection molding in combination with a virgin material. 

Initial Steps. The process for recycling articles into the recycled ABS resin is a combination of grinding, washing, drying and foreign matter removal. The conditions of these steps must be carefully optimized in order to produce a recycled ABS resin having the desired properties with good productivity. 

The raw material ground to the predetermined size is passed through a magnetic separator in order to capture ferromagnetic metals inside the ground material. 

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Refuse-derived Other Materials Recycling fuels energy recovery of mixed... 

These processes are aH characterized by low isobutane conversion to achieve high isobutylene selectivity. The catalytic processes operate at conversions of 45—55% for isobutane. The Coastal process also operates at 45—55% isobutane conversion to minimize the production of light ends. This results in significant raw material recycle rates and imposing product separation sections. 

Adhesives and resins are one of the most important raw materials in wood-based panels. Thus, each question concerning the life cycle assessment and the recycling of bonded wood panels does bring into question the adhesive resins used. This includes, for example, the impact of the resin on various environmental aspects such as waste water and effluents, emission of noxious volatile chemicals during production and from the finished boards, or the reuse for energy generation of wood panels. The type of resin has also a crucial influence on feasibility and efficiency for several material recycling processes. 

Can the process be operated at less severe conditions If this results in lower yield or conversion, can raw material recycle compensate for this loss ... 

Urethane lacquers, 240 Urethane materials recycling of, 207-208 synthetic methods for, 246-258 Urethane oils, 202, 241 Urethane polymers, 197 Urethanes... 

Process efficiency, e.g. by material recycling into the process where possible, use of catalytic pathways use of catalysts that can be regenerated/ recycled rational use of energy, and reduction of the mrmber of intermediate steps. 

Material recycling implies the application of the material used, without changing the chemical structure, for a new application ... 

THERMAL METHODS OF RAW MATERIALS RECYCLING OF PLASTICS WASTES... 

An Ecoprofile is an assessment of the environmental and resource impacts of a waste disposal process. This paper describes ecoprofiles for six different ways of disposing the plastic fraction in municipal solid waste -two material recycling processes that include separation of the plastic waste, material recycling without separation of the plastic waste, pyrolysis, incineration with heat recovery, and landfill. 17 refs. 

A question being disputed in Germany, important with regard to the amendment of the German Waste Act, is which wastes or residuals should or must be recycled, and which can be used for energy reeovery This paper attempts to define the line between material recycling and thermal exploitation. 2 refs. 

Materials Recycling Week 164, No.9, 28th Oct. 1994, p.4 PLASTICS INCINERATION CHEAPEST RECYCLING, SAY DUTCH... 

Different methods available for material recycling of plastics waste into raw materials for the chemical industry are reviewed and discussed. The technical problems, energy efficiencies and cost efficiencies of the processes are examined. 35 refs. 

Details are given of the development of energy and material recycling processes for thermosetting polymer composites. Applications in the cement industry and in coal fired fluidised bed combustion plants are discussed. 3 refs. 

Material recycling is the objective for every material, but at some point reuse or collection, separation and further recycling will no longer yield a useful product. The so-called plastic waste still contains a high calorific value which can be recovered to produce heat or electricity. Even better it may be possible to recover the chemical feedstock originally manufactured from oil. These two possibilities are reviewed. 

The stream discharged from a process step may consist of a mixture of product and unconverted raw material, which must be separated and the unchanged raw material recycled to the reaction zone for further processing. 

There are three ways of accomplishing materials conservation (i) effective materials utilization (ii) materials substitution and (iii) materials recycling. 

Materials recycling or resource recycling is essentially resource recovery, which is the means by which waste resources usually destined for disposal are used as secondary resources or secondary raw materials to serve as valued inputs to the economy, fulfilling both producer and consumer needs. Resource recycling, as has been pointed out, increases the supply of available material, and thereby offers a potentially attractive means of reducing... 

In the production of ammonia from hydrogen and nitrogen the conversion, based on either raw material, is limited to 15 per cent. The ammonia produced is condensed from the reactor (converter) product stream and the unreacted material recycled. If the feed contains 0.2 per cent argon (from the nitrogen separation process), calculate the purge rate required to hold the argon in the recycle stream below 5.0 per cent. Percentages are by volume. 

Materials, however, are solid wastes and are not exempt if they are recycled in certain other ways. For example, materials recycled in the following ways are defined as solid wastes ... 

If the liquid from the phase split requires separation, then this can normally be accomplished by distillation, except under special circumstances. A distillation sequence is most often required with products and byproducts removed from the process and unreacted feed material recycled. In some situations, byproducts might be recycled for reasons discussed in the previous section. 

Additives often form a problem in recycling processes. Material recycling is often not possible or only with a considerable loss of quality. Plastics recycling is notoriously difficult due to the mixed composition of the plastics waste stream. The recycled material can only be used in certain applications that do not demand a pure material. Recycling of the additives themselves is theoretically possible only for metals, but in practice this type of recycling is not feasible. The metals occur only in low concentrations. Recovery from fly ash and bottom ash is possible, but expensive in view of growing scarcity problems it may become a viable options for at least some metals. 

Material recycling of the cushion vinyl floor covering... 

According to these results, landfill of the waste, assuming no DEHP emissions, is the most environmental friendly option, closely followed by the scenario assuming material recycling of the end of life PVC waste. The worst option from an environmental point of view is the incineration of the EoL PVC waste. 

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