Study on effect of coal treatment with blast furnace slag on char reactivity in air

Waste heat of the blast furnace slag might be recovered in an allothermal coal gasification process to produce an alternative fuel for ironmaking. The effect of heat treatment of brown and sub-bituminous coals mixed with blast furnace slag on the properties of the produced chars was studied. More porous chars were formed at charring in contact with the slag. The development of better porosity in sub-bituminous coal chars was observed in contrast to brown coal, where charring was followed by cracking. Thermal analysis was used to study the behaviour of chars and to derive Arrhenius kinetic parameters for oxidation in air. The behaviour of chars is affected by the simultaneous development of thermally activated oxidation and decomposition processes. Higher volatile ignition temperature for chars produced with slag was observed. The activation energy for the combustion of chars produced with slag was essentially lower, while the pre-exponential factor is higher for chars produced without slag.