Ignited hard coal
Source: BAM, Division Reactive Substances and Systems
A reliable energy supply is of fundamental importance to the economy. Even if the transition from fossil fuels towards renewable energy is started and pushed on, coal has been and will continue to be one main energy resource for a longer time. However, coal combustion exhibits a high specific CO2 emission compared to other fossil fuels such as natural gas. Carbon capture and storage from waste gas of coal power plants is one promising technology to reduce the emission of large quantities of CO2 into the atmosphere. The so called oxy-fuel combustion, the combustion of coal under pure oxygen or a mixture of oxygen and recycled flue gases, is one possible prior condition for carbon capture and storage.
Handling combustible solids is always connected with fire and explosion risks. Safe handling of coal and coal dust under oxygen-enriched atmospheres is a major technological challenge. Particularly, the self-ignition and burning behaviour of coal dust may change compared to handling in air and become more critical.
In cooperation with KU University Leuven, Belgium, in division 2.2 Reactive Substances and Systems self-ignition and smouldering of coal dust in oxygen-enriched atmospheres was investigated. A new set-up, developed at BAM, allowed to measure the evolution of temperature, the mass change and the composition of flue gases of coal dust samples stored at defined conditions (temperature, ambient gas mixture) continuously.
The tests showed that the ignition risk is, as one might expect, increased in an oxy-fuel combustion system. The presence of CO2 reduces critical ignition temperatures and the maximum temperatures of the smouldering process; but the effect is comparatively low compared to the effect of increased oxygen mole fractions. The results also served to determine input parameters for numerical simulations (published in Wu et al.: Numerical investigation on the self-ignition behaviour of coal dust accumulations: The roles of oxygen, diluent gas and dust volume, Fuel Volume 188 (2017) 500-510).
Numerical investigation on the self-ignition behaviour of coal dust accumulations: The roles of oxygen, diluent gas and dust volume
Martin Schmidt, D. Wu, F. Norman, M. Vanierschot, F. Verplaetsen, J. Berghmans, E. van den Bulck
Fuel: Volume 188, 15 January 2017, Pages 500-510
BAM Abteilung Chemical Safety Engineering, Fachbereich Reactive Substances and Systems