On the development of a polyolefin gasification modelling approach

- A polyolefin air/steam gasification model for fluid bed reactors was developed.
- Contribution on the definition of pyrolysis, homogenous reactions and tar evolution.
- Model validation was performed against experimental tests and data from literature.
- The model is able to reproduce key gasification variables with acceptable error.
- The model provides a satisfactory prediction of tar generation.

Gasification is a promising alternative for polymeric waste valorization when mechanical recycling is unfeasible on account of its heterogeneity or partial contamination, or simply when it yields a product of lower quality than what the market requires. Apart from its application for electricity generation, the waste-derived syngas shows a great potential for chemical waste recycling for the synthesis of hydrogen, methane, natural gas or methanol. In spite of the effort devoted so far to the experimental demonstration of these processes to enable this technology to access commercial stage, it is still necessary to develop detailed models of the process that allow a precise prediction of the resulting syngas composition, as well as tar formation and global efficiency of the process. This research work presents the development of a polyolefin gasification model for fluidized bed reactors. The model details the behaviour of primary pyrolysis and homogeneous reactions of oxidation, steam reforming, aromatization and thermal cracking. To accomplish this, it adopts new modelling strategies for the definition of primary tar species in order to reflect their twofold nature (aliphatic and aromatic), as well as to describe kinetics and stoichiometry involved in thermal cracking processes of tar species. The model is able to successfully predict the generation, volume composition and heating value of the syngas, final tar generation and global efficiency of the process.