Simultaneous Removal of SO₂ and Trace SeO₂ from Flue Gas:  Effect of SO₂ on Selenium Capture and Kinetics Study

Abstract

Sulfur dioxide (SO2) and trace elements are all pollutants derived from coal combustion. This study relates to the simultaneous removal of SO2 and trace selenium dioxide (SeO2) from flue gas by calcium oxide (CaO) adsorption in the moderate temperature range, especially the effect of SO2 presence on selenium capture. Experiments performed on a thermogravimetric analyzer (TGA) can reach the following conclusions. When the CaO conversion is relatively low and the reaction rate is controlled by chemical kinetics, the SO2 presence does not affect the selenium capture. When the CaO conversion is very high and the reaction rate is controlled by product layer diffusion, the SO2 presence and the product layer diffusion resistance jointly reduce the selenium capture. On the basis of the kinetics study, a method to estimate the trace selenium removal efficiency using kinetic parameters and the sulfur removal efficiency is developed.

Chemistry of coal and coal combustion products from Kentucky power plants: Results from the 2007 sampling, with emphasis on selenium

“…Ló pez-Antó n et al (2006) did not find Se to be bound to fly ash carbon, in agreement with five of the six ashes studied by Narukawa et al (2005). Li et al (2006) also noted a Ca association in their study of the removal of SO 2 and Se from flue gas. As with the modeling conducted by Urban and Wilcox (2006a, b), they noted that the actual determination of Se in flue gas is difficult due to its extremely low concentration.…”

DRIFTS Study of Ammonia Activation over CaO and Sulfated CaO for NO Reduction by NH3

“…Previous studies have found that strong Brönsted acidity formed during sulfation process (26,27). Nevertheless, it is ammonia adsorbed over acid sites, though the overall catalytic effects over CaO and sulfated CaO are very different, and this may be due to the different intermediates produced from adsorbed NH 3 . It has been revealed that the H-abstraction of adsorbed NH 3 over the catalyst is the key step to decide the direction of catalytic activity, and the H-abstraction intermediates from adsorbed NH 3 could be NH 2 or NH (28,29): If the H-abstraction intermediate is NH, it could react as routes 4 or 5:…”

Theoretical Study of As2O3 Adsorption Mechanisms on CaO surface

“…Under an oxidizing atmosphere, gaseous As 2 O 3 should be the main form of arsenic combustion products [ 10 ]. It has been proven that CaO could adsorb As 2 O 3 in the coal-fired flue gas, and the dominating products were arsenate (AsO 4 3− ) [ 11 , 12 , 13 , 14 ]. CaO component in fly ash leads to the enrichment of arsenic [ 15 , 16 , 17 , 18 ].…”