Mixed plastic

Styrene block copolymers have been used as compatihilizers for mixed plastics to permit their processing for appHcations such as those outlined earlier (52,61). 

Results obtained for two mixed plastics are summarized in Table 4. A balance exists between process temperature, plastics feed rate, and product yields (67). For example, lower temperatures increase wax formation due to incomplete depolymerization. Slower feed rates and increased residence times reduce wax formation and increase the yield of Hquids. The data summarized in Table 4 illustrate that the addition of PET to a HDPE PP PS mixture changes the performance of the Conrad process. Compared to the reference HDPE PP PS mixture, increased amounts of soHds ate formed. These are 95% terephthahc acid and 5% mono- and bis-hydroxyethyl esters. At higher temperatures, apparentiy enough water remains to promote decarboxylation. 

Plastic Refractories and Ramming Mixes. Plastic refractories are mixtures of refractory grains and plastic clays or plasticizers with water. Ramming mixes may or may not contain clay and are generally used with forms or steel work. The amount of water used in these products varies but is held to a minimum to faciUtate drying. Plastics are generally suppHed in a ready-to-use state. 

A new application oF triboeleetrie separation involves the separation oF PVC From PET and other plasties. Recent developments in pre-eharging technology permit PVC to assume a strong negative charge and be removed cFFieientlv From properly protected mixed plastic Feedstocks (Fig, 19-62),... 

The BP Chemicals polymer cracking process is based at Grangemouth in Scotland and uses mixed plastics as the raw material. The reactor uses a fluidised bed which operates at 500 °C in the absence of air, and under these conditions the plastics crack thermally to yield hydrocarbons. These vaporize and are carried away from the bed with the fluidising gas. Solid impurities such as metals from PVC stabilisers accumulate in the bed or are carried away in the hot gas to be captured by a cyclone further along in the plant. PVC decomposes to HCl and this is neutralized on a solid lime absorbent to yield CaCl2 which is disposed of in landfill. The purified gas is cooled to condense most of the hydrocarbon which can be employed as commercially useful distillate feedstock. The light hydrocarbons which are less easy to condense are compressed, reheated and recycled as fluidising gas. 

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

Section 6 discusses some alternative options for mixed plastic waste (MPW) treatment ... 

Mixed plastic waste (MPW) with a limited chlorine (i.e., PVC) content ... 

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 ... 

Synthesis gas. 150 tonnes of mixed plastics per day produces roughly 350,000 Nm per day of clean synthesis gas (mainly H2/CO) that can be used as feedstock in petrochemical processes. 

From the description above it already can be deduced that this plant can deal with a lot of waste types and hence is rather robust in terms of acceptance criteria. S VZ has experience with treating mixed plastics waste, waste derived fuel (a mixture of plastics, wood and paper), the shredder light fraction of car wrecks, and the plastic fraction from shredded white goods and electronics. SVZ can handle on average 2% chlorine in MPW, with short-term excursions to 6%. The overall chlorine content has to be controlled by a right blend with other waste types. SVZ does not favour a high... 

The testing does not yet allow for setting specific input criteria. However, the testing made clear that the process probably can handle a broad spectrum of materials, such as wood, biomass, mixed plastic and pure PVC waste. For instance tests have been done on PVC waste but also with a mixture of PVC, PE, other polymers, Cu, Al, chalk, cement and fibres. 

Other Treatment Options for Mixed Plastic Waste... 

Note MPW is Mixed Plastic Waste MSW ca is municipal solid waste and comparable material Typical capacities considered are 50 ktpa to 200 tpa Theoretical potential if most blast furnaces and cement kilns in the EU start to replace regular fossil resources by MPW ... 

Macromolecular Symposia Vol.152, March 2000, p. 191-9 RECYCLING OF MIXED PLASTICS BY PYROLYSIS IN A FLUIDISED BED... 

The thermal cracking of a light ffaction of mixed plastics waste was carried out in a fluidised bed reactor and the fractions obtained were analysed by elemental analysis, gas chromatography and ashing. The main components of the waste were PE and PP with a small amount of PS and the bed was fluidised by pyrolysis gas, nitrogen or preheated steam. Experiments conducted at different temperatures and residence times were compared by calculating the crack severity for each experiment. The results obtained revealed that the amounts of ethene and propene obtained by pyrolysis with steam were comparable with those obtained using a commercial steam cracker. 

ROLE OF PVC IN THE RESOURCE RECOVERY OF HYDROCARBONS FROM MIXED PLASTIC WASTES BY PYROLYSIS... 

ENERGY RECOVERY THROUGH COMBINED INCINERATION OF MIXED PLASTICS WASTE AND SOLID MUNICIPAL WASTE... 

This comprehensive article supplies details of a new catalytic process for the degradation of municipal waste plastics in a glass reactor. The degradation of plastics was carried out at atmospheric pressure and 410 degrees C in batch and continuous feed operation. The waste plastics and simulated mixed plastics are composed of polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile butadiene styrene, and polyethylene terephthalate. In the study, the degradation rate and yield of fuel oil recovery promoted by the use of silica alumina catalysts are compared with the non-catalytic thermal degradation. 9 refs. lAPAN... 

Polymer Degradation and Stability 53,No.2, 1996,p.l89-97 THERMAL DEGRADATION OF MIXED PLASTIC WASTE TO AROMATICS AND GAS... 

A PVC-poor light fraction separated from mixed plastic household waste was pyrolysed to yield aromatic oils and heat-providing gas. Target products were benzene, toluene, xylenes, and styrene. Problematic pollutants were... 

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 use of mixed plastics waste as fuel for steel furnaces is briefly examined as NKK Corp., the second largest steelmaker in Japan plans to use about 66 million pounds of it. According to the company s test data, 440 pounds... 

Advances in Polymer Technology 14, No.4, Winter 1995, p.337-44 CHEMICAL RECYCLING OF MIXED PLASTICS BY PYROLYSIS... 

The use of pyrolysis for the recycling of mixed plastics is discussed and it is shown that fluidised bed pyrolysis is particularly advantageous. It is demonstrated that 25 to 45% of product gas with a high heating value and 30 to 50% of an oil rich in aromatics can be recovered. The oil is found to be comparable with that of a mixture of light benzene and bituminous coal tar. Up to 60% of ethylene and propylene can be produced by using mixed polyolefins as feedstock. It is suggested that, under appropriate conditions, the pyrolysis process could be successful commercially. 23 refs. 

This paper diseusses in detail the option of fluidised-bed reaetors to eraek mixed plastics waste into valuable raw materials, under the headings thermal cracking for feedstocks, pyrolysis of polyolefins, and other options. 7 refs. 

Brussels, 1994, pp.8. 12ins. 24/3/95. 8(13)5 ENERGY RECOVERY THROUGH COCOMBUSTION OF MIXED PLASTICS WASTE AND MUNICIPAL SOLID WASTE... 

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