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In light of Title I of the Clean Air Act Amendments of 1990, selenium will most probably be considered for regulation in the electric power industry. This has generated interest for removing this element from fossil-fired flue gas. This study deals with coal combustion: selenium volatilization and its speciation in the cooled flue gas were investigated to better understand its chemical behavior to validate the thermodynamic approach to such complex systems and to begin developing emission control strategies. Se volatility is influenced by several factors such as temperature, residence time, fuel type, particle size, and Se speciation of the fuels, as well as the forms of the Se inthe spiked coal/coke. Spiked coke and coal samples were burned in a thermobalance, and atomic Se and its dioxide were identified in the cooled combustion flue gas by X-ray photoelectron spectroscopy (XPS). A thermodynamic calculation was applied to a complex system including 54 elements and 3,200 species that describes the coal combustion. Several theoretical predictions concerning Se behavior, such as its speciation in flue gas, agreed well with experiments, which supports using thermodynamics for predicting trace element chemistry in combustion systems.

) 1-x (CeO 2 ) 2x (ZrO 2 ) 2 mixed oxides (LCZ) where 0 ≤ x ≤ 1 were synthesised from commercial La 2 O 3 , CeO 2 and ZrO 2 powders and co-melted in a 2-kW solar furnace. These samples were re-oxidised in air at temperatures that ranged from 900 K to 1100 K. The microstructures of the LC, LCZ and CZ oxides were investigated by XPS and XRD. Core-level spectroscopy (XPS) has been used to study electronic states (III) and (IV) of the Ce 3 d 5/2 and Ce 3 d 3/2 levels. The resolved components of the Ce 3 d 3/2 , 5/2 features were identified. The rate of Ce 3+ and Ce 4+ states were calculated for different values of x (0.1-1). The nature of the chemical bonds of Ce and O were determined from the Ce 3 d 3/2,5/2 and O 1 s photoelectron peaks, respectively.The XRD study revealed the presence of solid solutions (LCZ and CZ). The presence of crystalline phases (pyrochlore and fluoritelike structures) depends on the value of x. A decrease in the lattice parameter was observed with increasing x. La atoms were substituted by Ce atoms in a solid solution, and the oxygen vacancies were filled. The amount of fluorite-like phase increases with an increasing amount of Ce atoms.

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