Molecular Transformations of Arsenic Species in the Flue Gas of Typical Power Plants: A Density Functional Theory Study

摘要

The existing forms and their inter-transformations are important to study the behavior of arsenic and its capture technology in the flue gas of power plants. In this study, a density functional theory was applied to study the thermodynamic and kinetic aspects of arsenic substances in flue gas. Gibbs free energy comparison was used to evaluate the thermodynamic stability of various arsenic species at four temperatures (1200, 800, 370, and 25 degrees C), which represent the temperatures of flue gas in the area of the combustion center, horizontal flue, NOx removal reactor, and atmosphere, respectively. The results show that trivalent arsenic molecules are thermodynamically stable at high temperatures and pentavalent species are stable at low temperatures. The arsenic species vary with the temperature. At high temperatures, dehydrated compounds are the major species. These compounds will be hydrated and oxidized by O-2 when the temperature declines, as implied by the reaction path study. Arsenic acid becomes the most thermodynamically stable species at 25 degrees C.