Polymer waste pyrolysis

The qualitative and quantitative determination of the thermal and thermo-oxidative decomposition and combustion products advances closely with the development of high-performance investigation techniques. Early on, only the main products or classes of compounds were studied, whereas recently, special importance has been given to the evidence of products appearing as traces, since these might cause serious problems both for human life (by their toxicity, especially in incomplete combustion) and for the purification of the products obtained from polymer waste pyrolysis (or incineration), applied for their recovery as high-grade materials. 

CHEMICALS AND ENERGY FROM MEDICAL POLYMER WASTES. II. MALEATED PYROLYSIS PRODUCTS IN IPP/LLDPE PROCESSING... 

Schaumburg, 11., 3rd-4th Nov. 1994, p.232-45. 8(13) PYROLYSIS OF POLYMER WASTE Agarwal K General Motors Corp. 

Thus, for the development of polymer waste recycling technologies it is helpful to be aware of the chemical composition of the pyrolysis products of those polymers which are typical components of plastic wastes. 

Extmders are often used in continnons pyrolysis plants for supplying a molten stream of plastic to the main pyrolysis vessel. The extmder may also be vented to eliminate HCl (from PVC) and water vaponr from the waste plastics. In contrast to conventional extmsion, there is no need to bnild np high melt pressnre or to shear the polymer. These pyrolysis extruders are more like heated augers than polymer processing eqnipment. 

The Hamburg Fluidized-bed Pyrolysis Process to Recycle Polymer Wastes and Tires... 

The methods that will be dealt with here are those used to obtain hydrocarbon vapours from this first phase. The treatment of plastic wastes of all sorts by pyrolysis, being still in its early stages, workers keeping practised procedures confidential, and often protects them by patents. As a consequence, this chapter deals exhaustively only with the procedures that have been personally tested and developed by the author. The general principle of polyolefin waste pyrolysis consists of heating plastic materials in isolation to a sufficient temperature such that the polymers decompose into small hydrocarbon molecules. 

It can be shown that it is possible to recover high amounts of monomers from special polymers by pyrolysis in a tluidized-bed process. Up to 98 wt% of MMA can be recovered from filled or coloured PMMA wastes. In the case of polystyrene the rate of recovered styrene is limited to about 77 wt% the rest is oligomers. The high yields of TFE, HFP and C-C4F8 obtained from PTFE compounds in the experiments described show that tluidized-bed pyrolysis of pure PTFE or PTEE compounds is a feasible and interesting opportunity for the chemical recycling of this polymer. 

Thermal properties of ethylene copolymers are studied frequently and reported in literature [64-70]. These studies were directed to the evaluation of copolymer properties, use of various catalysts for achieving pyrolysis in order to recover polymer waste [71-75]. Some studies on thermal properties of ethylene copolymers are summarized in Table 6.1.4. 

For waste decomposition, studies have extensively investigated wood and synthetic polymers. Surface pyrolysis of woods may be assumed to be a first-order reaction 28... 

Wong HW, Broadbelt LJ. Tertiary resource recovery from waste polymers via pyrolysis neat and binary mixture reactions of polypropylene and polystyrene. Ind Eng Chem Res 2001 40 (22) 4716-4723. 

Significant effort has recently been put in for the elimination of polymer wastes from electric and electronic equipment (WEEE) by pyrolysis. WEEE includes mainly epoxy resins and styrene polymers. They often contain brominated aromatics, which are highly contaminant. However, their elimination by simple thermal treatments is no longer possible as one of the most important drawbacks in dealing with thermal treatment of WEEE is the likely production of supertoxic halogenated dibenzodiox-ins and dibenzofurans. A pyrolysis method at low temperature range was developed, which limited the formation of such toxic by-products and reduced pyrolysis costs, even at relatively long residence times in the reactor. 

Luda, M.P. Euringer, N. Moratti, U. Zanetti, M. WEEE recycling Pyrolysis of fire retardant model polymers. Waste Manag. 2005, 25, 203-208. 

Materials and energy recovery from polymer wastes by pyrolysis and combustion. 

Microwave heating is an appropriate tool for recycling polymer waste. For example, it can be applied to separate metal from polymer/metal laminates by pyrolysis, to depolymerize polyamide and poly(ethylene terephthalate) by solvolysis, or to devulcanize rubber (see Table 1.6). Detailed information on this topic is available in Ref. [19]. 

Pyrolysis of polymer wastes to produce useful gases and liquids is still another route of recycling. ... 

The results of research into the fluidised bed pyrolysis of plastic wastes are reported, with reference to determining the optimum process conditions for the process with respect to the reactor behaviour. The study investigates the effects of process variables such as bed temperature, polymer feed rate, bed hold-up, fluidising velocity, and size of inert material. Findings illustrate the importance of the knowledge of the hydrodynamics of the fluidised bed and of the interactions between bed and polymer particles in the design and operation of the reactor. 15 refs. 

The pyrolysis produets obtained from a variety of mixed plasties eontaining PVC are investigated. While hydroehlorie aeid is the major chlorinated product produced by PVC pyrolysis, other chlorinated hydroearbons are produced. However, the composition and yield of these compounds are very much dependent upon the other polymers present in the plastic mixture. In the ease of a polymeric waste stream containing inorganic fillers, sueh as ealcium carbonate, the HCl produced by the PVC ean be neutralised in situ, leading to the produetion of inorganic chlorides, alleviating many of the concerns associated with HCl formation. 9 refs. 

The present state of technology is reviewed (mainly from German literature of 1993 -4) in the Add of three principal thermal methods used for plastics wastes, namely pyrolysis (high-temperature carbonisation, coking), hydrocracking and gasification. 36 refs. Articles from this journal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. 

A pilot plant for the high temperature pyrolysis of polymers to recycle plastic waste to valuable products based on rotating cone reactor (RCR) technology. The RCR used in this pilot plant, the continuous RCR was an improved version of the bench-scale RCR previously used for the pyrolysis of biomass, PE and PP. 9 refs. 

Among the most frequently used nitrogen containing polymers in electrical, electronic, and automotive applications are PA and ABS. Pyrolysis proved to be a suitable method for recycling plastic waste. 

In an analogous way as described above, in the case of ABS polymers that are equipped with bromine containing flame retardants, pyrolysis oils with low bromine content can be obtained (133). This issue is important for processing scrap plastics from waste of elec-... 

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