Pyrolysis and combustion characteristics of coals in oxyfuel combustion

Oxyfuel combustion technology is one of the near-zero emission clean coal technologies, which can realise the large-scale CO2 capture, low NOx emission, and easier removing of SO2. This paper describes the characteristics of pyrolysis, gasification and combustion of coals and chars in oxyfuel combustion applying the non-isothermal thermogravimetric analysis. Experimental results show that the pyrolysis reactivity is highly similar in N2 and CO2 at low temperature. The mass loss rate of experimental coals in CO2 increases significantly at around 810 °C. In comparison to the conventional combustion, thermogravimetric curves of coal and char combustion in O2/CO2 tend towards higher temperature zone. Sample mass, particle size and heating rate all have considerable effects on the heat and mass transport process, which influences the whole combustion process of coal particles in oxyfuel conditions. Char reactivity prepared in CO2 is almost equivalent to that prepared in N2. The results of kinetics analysis indicate that compensation effect exists between apparent activation energy and pre-exponential factor in different oxygen concentrations during both coal and char combustion.

► Pyrolysis reactivity of coals is highly similar in N2 and CO2 at low temperature.
► Coal combustion performance in O2/CO2 conditions is deteriorated.
► Sample mass, particle size and heating rate all have influence on diffusion process.
► Compensation effect exists between the two apparent kinetic parameters.