Experimental investigations of pyrolysis and char conversion kinetics in plug flow configurations with a focus on the ignition and early char burnout phase

The reliable design of Oxy-Fuel combustion systems requires quantitative data about the kinetic rates of volatile release and char conversion. While the devolatilization is important for the fuel ignition, the char conversion is the time determining scale of the combustion process. The main factors of influence are macromolecular structure of the solid fuel, temperature, heating rate as well as composition of the gas phase.

The main focus of this project is to deliver a data base for the further development of network pyrolysis models in A1 and the further development of an advanced version of the char conversion kinetics model (CCK). Due to different approaches in measurement methods two test rings have been constructed: a laminar plug flow reactor with a gas analyzing system to investigate pyrolysis and a laminar flow reactor with optical access, applying an imaging two colour pyrometry system for particle size and temperature measurements. Both facilities work at heating rates typical for pulverized fuel boilers (105 K/s).  

While in the first reactor the devolatilization is measured through gas emissions and char sampling, the second reactor is used to measure particle temperature and diameter to close the energy balance around burning char particles to determine reaction rate parameters.

The focus of measurement and model development lies on:

  • The influence of elevated CO2 concentration in Oxy-Fuel systems, leading to increased gasification rates
  • Changes of surface reactions through competition of dissociative absorption of CO2/O2
  • Inclusion of the influence of catalytic active minerals, pore size dependent sorption effects, thermal annealing and pressure into char conversion kinetics