Predicting the distribution of thermal pyrolysis of high density polyethylene products using a mechanistic model

Original Article


The increase of the plastic wastes has urged finding different solutions for their recycling. Thermal pyrolysis is a suitable solution for refining the combination of different plastics. The main goal of this research is developing a model to predict the distribution of products obtained from pyrolysis. To do this a mechanism model based on free radical mechanism is developed. In this model some kinetic stages are used including initiation, scission, abstraction, aromatic making and radical combination. After determining the kinetic constants, the equations were solved in MATLAB software. The results were compared with experimental results from a conical spouted bed reactor (CSBR) in temperature (500–900 °C) and residence time (0.016–0.032 s). the results show that the model can predict the experimental observation for different temperatures and residence time and estimate the amount of low and high density products in a way that the increase of that gas fraction increase and high density products decrease. Also in all the situation the amount of olefin fraction is more than paraffin and diolefin.


Polyethylene Pyrolysis Mechanistic model Temperature Residence time 

List of symbols


molar flow of n carbon atoms aromatic (mol/m3)


molar flow of n carbon atoms diolefin (mol/m3)


kinetic constant of H-abstraction reaction (m3/mol s)


kinetic constant of initial scission reaction (s− 1)


kinetic constant of H-abstraction reaction (m3/mol s)


kinetic constant of termination reaction (m3/mol s)


kinetic constant of production of aromatics 1reaction (m3/mol s)


kinetic constant of production of aromatics 2reaction (m3/mol s)


kinetic constant of β-scission reaction (s− 1)


molar flow of n carbon atoms olefin (mol/m3)


molar flow of n carbon atoms paraffin (mol/m3)


rate of production of i via β-scission (mol/m3 s)


rate of production of i via aromatization (mol/m3 s)


rate of production of i via H-abstraction (mol/m3 s)


rate of production of i via initial scission (mol/m3 s)


rate of production of i via H-abstraction (mol/m3 s)


rate of production of i via termination (mol/m3 s)


rate of production of the j reaction (kg/m3 s)


molar flow of n carbon atoms radical diolefin (mol/m3)


molar flow of n carbon atoms radical olefin (mol/m3)


molar flow of n carbon atoms radical paraffin (mol/m3)


  1. Al-Salem S, Lettieri P (2010) Kinetic study of high density polyethylene (HDPE) pyrolysis. Chemical engineering research design 88(12):1599–1606CrossRefGoogle Scholar
  2. Artetxe M et al (2012) Production of light olefins from polyethylene in a two-step process: pyrolysis in a conical spouted bed and downstream high-temperature thermal cracking. Ind Eng Chem Res 51(43):13915–13923CrossRefGoogle Scholar
  3. Biswas S, Mohanty P, Sharma D (2013) Studies on synergism in the cracking and co-cracking of Jatropha oil, vacuum residue and high density polyethylene: kinetic analysis. Fuel Process Technol 106:673–683CrossRefGoogle Scholar
  4. Bockhorn H, Hentschel J, Hornung A, Hornung U (1999a) Environmental engineering: stepwise pyrolysis of plastic waste. Chem Eng Sci 54(15):3043–3051CrossRefGoogle Scholar
  5. Bockhorn H, Hornung A, Hornung U (1999b) Mechanisms and kinetics of thermal decomposition of plastics from isothermal and dynamic measurements. J Anal Appl Pyrolysis 50(2):77–101CrossRefGoogle Scholar
  6. Churkina G, Brown DG, Keoleian G (2010) Carbon stored in human settlements: the conterminous United States. Glob Change Biol 16(1):135–143CrossRefGoogle Scholar
  7. Conesa J, Marcilla A, Caballero J, Font R (2001) Comments on the validity and utility of the different methods for kinetic analysis of thermogravimetric data. J Anal Appl Pyrolysis 58:617–633CrossRefGoogle Scholar
  8. Elordi G, Lopez G, Olazar M, Aguado R, Bilbao J (2007) Product distribution modelling in the thermal pyrolysis of high density polyethylene. J Hazard Mater 144(3):708–714CrossRefGoogle Scholar
  9. Faravelli T (1999) Gas product distribution from polyethylene pyrolysis. J Anal Appl Pyrolysis 52(1):87–103CrossRefGoogle Scholar
  10. Gascoin N, Navarro-Rodriguez A, Gillard P, Mangeot A (2012) Kinetic modelling of high density polyethylene pyrolysis: Part 1. Comparison of existing models. Polym Degrad Stab 97(8):1466–1474CrossRefGoogle Scholar
  11. Jiang L (2015) Application of genetic algorithm to pyrolysis of typical polymers. Fuel Process Technol 138:48–55CrossRefGoogle Scholar
  12. Kaminsky W, Schlesselmann B, Simon C (1995) Olefins from polyolefins and mixed plastics by pyrolysis. J Anal Appl Pyrolysis 32:19–27CrossRefGoogle Scholar
  13. Levine SE, Broadbelt LJ (2009) Detailed mechanistic modeling of high-density polyethylene pyrolysis: Low molecular weight product evolution. Polym Degrad Stab 94(5):810–822CrossRefGoogle Scholar
  14. Marongiu A, Faravelli T, Ranzi E (2007) Detailed kinetic modeling of the thermal degradation of vinyl polymers. J Anal Appl Pyrolysis 78(2):343–362CrossRefGoogle Scholar
  15. Mastral J, Berrueco C, Ceamanos J (2007a) Modelling of the pyrolysis of high density polyethylene: product distribution in a fluidized bed reactor. J Anal Appl Pyrolysis 79(1):313–322CrossRefGoogle Scholar
  16. Mastral J, Berrueco C, Ceamanos J (2007b) Theoretical prediction of product distribution of the pyrolysis of high density polyethylene. J Anal Appl Pyrolysis 80(2):427–438CrossRefGoogle Scholar
  17. Poutsma ML (2003) Reexamination of the pyrolysis of polyethylene: data needs, free-radical mechanistic considerations, and thermochemical kinetic simulation of initial product-forming pathways. Macromolecules 36(24):8931–8957CrossRefGoogle Scholar
  18. Ranzi E (1997) Kinetic modeling of polyethylene and polypropylene thermal degradation. J Anal Appl Pyrolysis 40:305–319CrossRefGoogle Scholar
  19. Ranzi E, Dente M, Goldaniga A, Bozzano G, Faravelli T (2001) Lumping procedures in detailed kinetic modeling of gasification, pyrolysis, partial oxidation and combustion of hydrocarbon mixtures. Prog Energy Combust Sci 27(1):99–139CrossRefGoogle Scholar
  20. Sezgi NA, Cha WS, Smith J, McCoy BJ (1998) Polyethylene pyrolysis: Theory and experiments for molecular-weight-distribution kinetics. Ind Eng Chem Res 37(7):2582–2591CrossRefGoogle Scholar
  21. Violi A, D’Anna A, D’Alessio A (1999) Modeling of particulate formation in combustion and pyrolysis. Chem Eng Sci 54(15):3433–3442CrossRefGoogle Scholar
  22. Wall L, Madorsky S, Brown D, Straus S, Simha R (1954) The depolymerization of polymethylene and polyethylene. J Am Chem Soc 76(13):3430–3437CrossRefGoogle Scholar
  23. Wallis MD, Bhatia SK (2007) Thermal degradation of high density polyethylene in a reactive extruder. Polym Degrad Stab 92(9):1721–1729CrossRefGoogle Scholar
  24. Williams PT, Williams EA (1999) Fluidised bed pyrolysis of low density polyethylene to produce petrochemical feedstock. J Anal Appl Pyrolysis 51(1):107–126CrossRefGoogle Scholar

Copyright information

© Springer International Publishing Switzerland 2017

Authors and Affiliations

  1. 1.Department of Chemical Engineering, School of Engineering, Tehran North BranchIslamic Azad UniversityTehranIran
  2. 2.Faculty of EngineeringIran Polymer and Petrochemical Institute (IPPI)TehranIran

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