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

Abstract

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 °C), which represent the temperatures of flue gas in the area of the combustion center, horizontal flue, NO x 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 °C.

The effect of H2O on formation mechanism of arsenic oxide during arsenopyrite oxidation: Experimental and theoretical analysis

“…In addition, it is difficult to clarify the reaction process accurately via experiments due to the inherently fast chemical reactions. Quantum chemistry calculations are, therefore, a useful way to study the reaction process, which can provide a molecular-level understanding of arsenic oxide formation during coal combustion [23][24][25].…”

Deactivation Mechanism of the Commercial V2O5–MoO3/TiO2 Selective Catalytic Reduction Catalyst by Arsenic Poisoning in Coal-Fired Power Plants

“…Arsenic in flue gas mainly existed in the form of As 2 O 3 , which could deposit on the catalysts and be oxidized to As 2 O 5 as a result of the interaction with the catalysts. 15 No arsenic signal was detected in the fresh catalyst. The arsenic species on the top layer catalysts were mainly in the form of As 2 O 5 (As 5+ ), indicating that a coating layer was formed to block the active sites on the catalyst, leading to physical deactivation of the catalysts.…”

Deep removal of arsenic from regenerated products of spent V2O5-WO3/TiO2 SCR catalysts and its concurrent activation by bioleaching through a novel mechanism

“…In addition, SCR catalysts suffer from deactivation during commercial applications due 3 to various reasons including sintering, blockage, poisoning, attrition, crushing, loss of vanadium or its speciation changes [4][5][6][7]. In particular, the extremely complex components of coal-fired flue gas accelerate SCR catalyst deactivation by adsorbing or depositing alkali, alkaline earth, metalloid and heavy metals (e.g., K, Na, Ca, Mg, As, Hg and Pb) [8][9][10]. On average, SCR catalysts have a service lifetime of ~3-5 years, resulting in a large amount of obsolete SCR catalyst materials [11].…”