Vanadium and nickel speciation in pulverized coal and petroleum coke co-combustion

Vanadium and nickel in emissions from fossil-fuel combustion and in the fly ash can be an environmental concern. The fly ash from the combustion of a 70% coal/30% petroleum coke blend in a 500 MW pulverized-fuel utility boiler was studied by a variety of X-ray, optical microscopy, and electron beam methods. The fly ash V and Ni are present in heterogeneous silicates, glass, sulfates, oxides and oxyhydroxides, and crystalline and/or amorphous mixed clay minerals, and also in Ni, detrital ferromagnesian silicates. Vanadium- and Ni-bearing spinels are incorporated into magnetite structures. Multiwalled nanotubes encapsulate V and Ni, and C₆₀, C₇₀, and C₈₀ fullerenes and their derivatives are present.