Feedstock recycling mixed plastics waste

Current methods of feedstock recovery are reviewed. Brief details are given of pyrolysis, hydrogenation, gasification, and chemolysis. Activities of some European companies are briefly discussed in the areas of recycling mixed plastics waste and closed-loop recycling. 

Processes designed to use thermal treatment to decompose the plastics into liquid and/or gaseous materials have often had mixed technical and economic success. For example, BASF planned to build a 661-million-lb/year facility for recycling mixed plastic wastes into hydrocarbon feedstocks, but eventually canceled the plans. 

Section 3 discusses options for feedstock recycling of mixed plastic waste ... 

Concerning feedstock recycling of mixed plastic waste (MPW) with a low chlorine content, the following initiatives seem to be most promising. They are either operating in practice, have operated in the past, or have a fair chance of becoming operational in the short-term. Methods include ... 

Feedstock recycling is examined as a method of plastics recovery. The range of techno logics currently employed are described, and include pyrolysis, hydrogenation, gasification, and chemolysis. Methods for the recycling of mixed plastics wastes are discussed, which include work by BP Chemicals, VEBA Oil, Shell Chemicals and Leunawerke. 

The BP-led feedstock recycling consortium recently unveiled its new larger-scale fluidised bed pyrolysis pilot plant, located on the BP refinery site at Grangemouth. The 2 tonne/day plant will take mixed plastics waste from a variety of sources to provide more extensive trial results, to be used in the conceptual design of a 25,000 t/y semicommercial demonstration plant. The consortium envisages a series of plants, of around 25,000-50,000 t/y, scattered across Europe. 

Feedstock or chemical recycling is seen as complimentary to mechanical recycling and seems appropriate for cost effective treatment of mixed and contaminated plastic waste streams (115). A progress report, on potential technologies for high PVC content mixed plastic waste streams, is available (21). Promising developments, which look technically and economically viable, are ... 

The detailed analysis of the derived oil/wax and gas products from the pyrolysis of plastics in relation to process conditions and different types of plastic is essential in providing data for the assessment of the feedstock recycling process. In addition, the yields and composition of gases and oils from the pyrolysis of mixed plastic waste are important in assessment of the process and to determine the possibility of any interactions between the plastics during pyrolysis. 

A consortium of European plastic resin companies, the Plastics to Feedstock Recycling Consortium, has a pilot plant for thermal recycling in Grangemouth, Scotland, and hopes to use the technology in a full-scale commercial plant by late 2000. The system uses fluidized bed cracking to produce a waxlike material from mixed plastic waste. The product, when mixed with naptha, can be used as a raw material in a cracker or refinery to produce feedstocks such as ethylene and propylene. ... 

One of the most expensive and time-consuming aspects of polymer recycling is the separation process. It would therefore make economic sense if mixed plastics waste could be taken and recycled back to suitable feedstocks. The essential feature of feedstock recycling processes is the use of heat (thermolysis) to break bonds, similar to crude oil refining. The process may be carried out by heat alone (pyrolysis), in a hydrogen atmosphere, or in the presence of oxygen (gasification). In the latter case... 

Finally, other relevant treatment options for plastics waste include landfill and mechanical recycling. Since these options (unlike Vinyloop and cement kiln incineration) are not even similar to feedstock recycling we discuss them here only very briefly. Mechanical recycling of plastics (be it PVC or other plastics), needs dedicated collection of the plastic waste in question. This is only possible for selected plastic flows (high volumes, recognisable products, products consisting mainly of one plastic). Landfill can accept plastic waste in any waste context (pure plastic type, MPW, mixed materials). I will only address the costs of these alternative technologies. 

A 20ft-high mini plant has been built at BP s refinery at Grangemouth, near Edinburgh, as an experiment by several leading European petrochemical companies to address the difficult issue of plastic recycling. The 7501/ y pilot plant accepts mixed plastics ground into pieces a maximum of 2cm across and passes them over hot sand which converts them into a gas. This is distilled back into plastic feedstock which can be fed back into the petroehemical plant to make fresh plastic. This process eould be replieated at many small plants, located at ehemieal works or even beside municipal waste tips. 

The state of plastics recycling in Poland is presented and the results of research projects developed in this Institute concerning feedstock recycling of mixed plastics (KARBOTERM, a new process for the utilization of plastics wastes in coking plants) as well as recycling of... 

In principle, it makes no sense to collect waste streams separately, unless suitable outlets are secured for such flows. This seems the case for soiled and mixed plastic packaging wastes, since these cannot be reprocessed to any better materials than those that substitute low-grade wood and since the option of feedstock recycling is operating at a huge economic loss. Moreover, no serious health, toxicity, or safety problems become apparent in case of less strict collection requirements. 

Feedstock recycling is complementary to mechanical recycling since it is less sensitive to nnsorted or contaminated plastics waste and enlarges the overall recycling capacities for large waste qnantities to be snpplied in the future. Examples of such mixed streams are... 

During the pyrolysis of mixed waste plastic, one of the main problems associated with the feedstock recycling is the presence of plastic containing hetroatoms, e.g. PVC, ABS, PVDC, etc. Efforts are made to remove the heteroatoms before pyrolysis. Chlorine can be removed either by thermal degradation or by using a catalyst. The HCl generated in the process can be used as industrial hydrochloric acid. 

Pyrolysis is a tertiary or feedstock recycling technique capable of converting plastic waste into fuels, monomers, or other valuable materials by thermal and catalytic cracking processes. This method can be applied to transform both thermoplastics and thermosets in high-quality fuels and chemicals. Moreover it allows the treatment of mixed, unwashed plastic wastes. 

As feedstock recycling and pyrolysis is not incineration there are no toxic or environmentally harmful emissions. Pyrolysis recycling of mixed plastics thus has great potential for heterogenous plastic waste that cannot be economically separated. 

Thermal processes are mainly used for the feedstock recycling of addition polymers whereas, as stated in Chapter 2, condensation polymers are preferably depolymerized by reaction with certain chemical agents. The present chapter will deal with the thermal decomposition of polyethylene, polypropylene, polystyrene and polyvinyl chloride, which are the main components of the plastic waste stream (see Chapter 1). Nevertheless, the thermal degradation of some condensation polymers will also be mentioned, because they can appear mixed with polyolefins and other addition polymers in the plastic waste stream. Both the thermal decomposition of individual plastics and of plastic mixtures will be discussed. Likewise, the thermal coprocessing of plastic wastes with other materials (e.g. coal and biomass) will be considered in this chapter. Finally, the thermal degradation of rubber wastes will also be reviewed because in recent years much research effort has been devoted to the recovery of valuable products by the pyrolysis of used tyres. 

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