Combustion reactivity of different oil-fired fly ashes as received and leached

The combustion of heavy fuel oil for power generation leads to a great production of fly ashes, usually disposed of in controlled expensive landfills. As possible alternatives to their conventional disposal, hydrometallurgical processes are used for the recovery of valuable metals such as vanadium and nickel and the carbonaceous residues, so obtained, could be burned to recover energy. In this study, the combustion of oil-fired fly ashes, as received and leached, was investigated by thermo-analysis in atmospheres at different oxygen concentration (6, 12 and 21 vol%). Two commercial coals were used as reference samples. The ignition temperature and the thermo-kinetic analysis were used to compare the reactivity of the different samples. Besides, in order to value the feasibility of co-combustion of leached fly ashes with coals in pre-existent coal boilers, blends of leached fly ash with coal were prepared and their combustion behaviour was investigated.