Experimental investigations of pyrolysis and char conversion kinetics in a well-stirred reactor under atmospheric and pressurised conditions

The Oxyflame project A1 investigates the combustion of synthetic carbon, coal and biomass under conditions similar to pulverized coal (PC) burners. The objective is to model the kinetics in Oxy-Fuel atmosphere, i.e. the release of mass and energy from a fuel particle. When using solid fuels, combustion can be divided into the two sub-processes pyrolysis and char burnout. Pyrolysis depicts the process of releasing volatiles (e.g. hydrocarbons and nitrogen compounds) from a fuel particle, char burnout is the oxidation of the remaining carbon-rich particle.

The conditions in the hot zone of PC boilers are being approximated in a fluidized bed reactor (FBR), in which high particle heat-up rates and long residence times can be realized. Long residence times are an essential advantage of this system, because it allows for the investigation of effects in the late burnout phase, e.g. annealing or ash layer formation. Furthermore, the gas phase composition can be chosen in a wide parameter range. This enables the separate analysis of pyrolysis in pure N2 or CO2 atmosphere and char burnout depending on O2 and H2O concentration of the carrier gas. To expand the validity range of existing models, the focus in the second phase of the CRC/TRR 129 is set on the investigation of char burnout under pressures of up to 2 MPa.