Jing Li - University of Maryland
This work is focused on developing and applying a systematic methodology for the characterization of pyrolysis of polymeric materials based on milligram-scale and bench-scale tests to isolate a specific chemical and/or physical process in each scale level. The entire study is divided into two parts corresponding to two different scales of tests and analysis. The first part is concentrated on the measurement of kinetics and thermodynamics of the thermal degradation of polymeric materials at milligram-scale. It employs a simultaneous thermal analysis instrument capable of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). All measured properties are incorporated into a continuum pyrolysis model. This model is subsequently employed to analyse DSC heat flow and extract sensible, melting and degradation reaction heats. The extracted set of kinetic and thermodynamic parameters is shown to simultaneously reproduce TGA and DSC curves. This procedure was used to characterize fifteen widely used commercial polymers.
The second part of this study was extended to bench-scale gasification experiments that were carried out using a controlled atmosphere calorimetric pyrolysis apparatus (CAPA), which has been recently developed in our group. The CAPA is used to measure material gravimetric and thermal changes during thermal decomposition in an anaerobic atmosphere with a capability of analysing material thermal transport properties. These properties, combined with material kinetics and thermodynamics from the first part of this study, served as inputs for this fully parametrized model simulating one-dimensional pyrolysis under wide range of external heat fluxes. The predictive power of this model and validity of its parameters are verified against the results of mass loss measurements. Seven out of fifteen polymers were validated in bench-scale and the parametrized simulations showed reasonable agreement with experimental data under wide range of conditions.