Pyrolysis of plastics

Industrial Engineering Chemistry Research 40, No.22, 31st Oct. 2001, p.4749-56 MICROWAVE-INDUCED PYROLYSIS OF PLASTIC WASTES... 

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. 

Defluidization modelling of pyrolysis of plastics in a conical spouted bed reactor... 

D.S. Scott, S.R. Czemik, J. Piskorz, A.G. Radlein, Fast pyrolysis of plastic wastes, Energy Fuels 4 (1990) 407-411. 

He is currently supervising a group of 15 students and scientists in the field of pyrolysis of plastic waste in a fluidized bed process and a group in the field of metal-locene/methylaluminoxane chemistry. His past experience includes the development of pilot plants for the feedstock recycling of plastic wastes and scrap tires, and discovering highly active metallocene catalysts for the polymerization of olefins. He has published more than 300 papers and books and holds 20 patents. He has organized several international symposia in the field of pyrolysis and olefin polymerization. 

As a rule, the pyrolysis of plastics follows complex routes that cannot be described by one or more chemical reactions, but only and still rather imperfectly by either empirical formnlas featnring fractional stoichiometric coefficients or comprehensive systems of elementary reactions, i.e. reactions that really proceed as written. Moreover, the composition and strnctnre of these reaction systems may vary with details of molecular structure, such as chain irregnlarities, incorporation of initiators or catalysts, etc. As a consequence, precise mechanisms are of only scientific interest, an industrial approach being limited to overall considerations, such as the heat effect and the product distribution resulting under particular reaction conditions. 

R. Reverse, Process and apparatus for the controlled pyrolysis of plastic materials, US Patent 0056214 Al, 2001. 

I. Nakamura, and K. Fujimoto, Development of new disposable catalyst for waste plastics treatment for high quality transportation fuel, Catal. Today, 27, 175 (1996). F. Pinto, P. Costa, I. Gulyurtlu, and I. Cabrita, Pyrolysis of plastic wastes 2. Effect of catalyst on product yield,. 1. Anal. Appl. Tyrol, 51, 57 (1999). CN1062918(1992). 

H. Bockhorn, J. Hentschel, A. Homung and U. Homung Environmental engineering stepwise pyrolysis of plastic waste, Chem. Eng. ScL, 54, 3043-3051 (1999). 

H. Sinn and W. Kaminsky Pyrolysis of Plastic Waste and Scrap Tires Using a Fluidized-Bed Process. Abstr. Pap. Am. Chem. Soc., 94 (1979). 

The liquid product obtained from thermal cracking can be either catalytically cracked/ hydrocracked or co-processed with a refinery feed. Since the catalytic cracking of oil derived from MWP is more or less problematic, any cracking catalyst can be applied to oil derived from pyrolysis of plastics. But the yield and the quality of gasohne obtained from cracking step vary with the type of catalyst and the properties of the pyrolytic oil derivated from waste plastics. 

E. Williams and P. T. Williams. Analysis products derived from the fast pyrolysis of plastic waste. Journal of Analytical and Applied Pyrolysis, 40-41, 347-363 (1997). 

F. Pinto, P. Costa, 1. Gnlyurtulu and 1. Cabrita, Pyrolysis of plastic waste 2. Effect of catalyst on product yield. Journal of Analytical and Applied Pyrolysis, 51, 57-71 (1999). 

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. 

The oils derived from pyrolysis of plastics have the potential to be used directly as fuels. However, to act as direct substitutes for established petroleum-derived fuels requires detailed analysis of their fuel properties in comparison with those of petroleum refined fuels. Table 11.8 shows the fuel properties of oils derived from the pyrolysis of various plastics [46, 47]. Table 11.9 shows comparative data for refined pefroleum fuels [48]. 

Composition of Liquid Fuels Derived from the Pyrolysis of Plastics... 

W. Kaminsky and H. Sinn, Pyrolysis of plastic wastes and scrap tyres using a fluidised bed process.In J. L. Jones and S. B. Radding(eds) Thermal Conversion of Solid Wastes and Biomass.ACS Syposium Series 130, American Chemical Society, Washington,D.C (1980). 

Table 15.1 Effect of slaked lime addition on the pyrolysis of plastic containing 1% PVC. (Reprodnced by permission of Masa-taka Tsnkada)...

The essential steps in the Thermofuel pyrolysis of plastics involve ... 

In the last decade several studies focused on the pyrolysis of plastic mixture in BFB reactors, operated under different conditions of temperatnre, flnidizing gas, bed material, reactor size and geometry [10, 12, 26, 27, 48], Particnlar attention has been devoted to the effect of PVC presence on the determination of yield of chlorinated aromatics [10, 12, 27]. The effect of temperature, which has been also well stndied [12, 27, 48], appears to be in accordance with that described for single polymer feeding an increase of temperature leads to an increase of yields in gas and aromatics and to a decrease of waxes. It is however noteworthy that the temperature value has to be selected on the basis of mixture composition, in order to optimize the desired products. In fact, most of polymers produces aromatics at higher temperatures and residence times (PE, PP) while others (like PS) do so at lower temperatures. 

M. L. Mastellone and U. Arena, Bed defluidization during the fluidized bed pyrolysis of plastic waste mixtures, Polymer Degradation and Stability, 85, 1051-1058 (2004). 

M. Ponte, M. L. Mastellone, F. Perugini and U. Arena, Fluidised bed pyrolysis of plastic mixtures, Joint Meeting of Italian and Greek Sections of The Combustion Institute, paper 4-section 4, Corfu, 17-19 June 2005. 

H. W. Schnecko, Pyrolysis of used tires, Chem. Ing. Techn., 48, 443-447 (1976). W. Kaminsky, Pyrolysis of plastic waste and scrap tyres in a fluid bed reactor. Resource Recovery Conserv., 5, 205-216 (1980). 

Figure 18.1 Schematic experimental set-up for pyrolysis of plastics and dehalogenation process. (Reproduced with permission from the American Chemical Society)...

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