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Energy and Chemicals through Pyrolysis of Thermoplastic Polymers: Kinetics and Reactor Design

Recycling plastic solid waste (PSW) is becoming more and more important, due to (i) increasing landfilling constraints and taxes and (ii) the potential recovery of energy or chemicals.
Three different routes for the beneficial utilisation of PSW are primary (re-extrusion ofclean production scrap), secondary (mechanical treatment of production scrap and post consumer waste) and tertiary (energy recovery through incineration and co-incineration in cement kilns) recycling.  (Co-)incineration requires an extensive flue gas purification to meet the stringent emission norms, especially regarding some contaminants that arepresent in PSW, such as heavy metals (pigments), flame retardants (Br, Sb, P, ) and volatile organic compounds formed by incomplete combustion. A fourth PSW treatment route is therefore considered, namely the valorization of chemicals, which can be used as feedstock for the production of similar products.
Recently, the research focus has shifted towards thermo-chemical conversion of PSW into chemicals and/or fuel,i.e. by pyrolysis in the absence of oxygen. Pyrolysis can overcome certain drawbacks of recycling and incineration because of (i) the low process temperature (350 - 500°C), at which the contaminants remain in the carbonaceous char; (ii) the inert process atmosphere and (iii) the possibility to work on small scale.
The doctoral research focuses on thermo-chemical valorization of PSW and includes:
-          evaluation of theimpact of legislation on the evolution of the sector
-          critical literature surveyto determine strengths and weaknesses of previous research, which will result in a final research strategy (methods, analysis techniques, )
-          initial screening of plastic solid waste streams and their potential in the waste-to-chemicals concept: PE, PP, PS, PET, polycarbonate, rubber and bio-polymers
-          selection of the target polymers and/or elastomers
-          full characterization of decomposition (isothermal, dynamic, reactor) to obtain (i) kinetic expressions, (ii) product identification as function of varying process conditions and (iii) mass and energy balances for the processes
-          characterization of the formed formed and the potential and/or required further processing to enable reuse
-          selection of reactor types, preferably fluidized beds (in case they can meet the process condition requirements)
-          experimental analysis of the process conditions in these reactors
-          determination of the essential parameters (mixing, residence time, temperature, ) versus the required conversion
-          final combination of the different research topics in a practical design method together with calculation models
-          techno-economic evaluation with focus on product valorization
Date:1 Feb 2010  →  17 Sep 2013
Disciplines:Inorganic chemistry, Organic chemistry, Theoretical and computational chemistry, Other chemical sciences
Project type:PhD project