Mercury emission and speciation in fly ash from a 35 MW th large pilot boiler of oxyfuel combustion with different flue gas recycle

Self Cite

La1–x A x Mn1–y B y O3 (A = Ca, Sr and Ce, B = Cu, Co and Fe, x = 0/0.2, y = 0/0.2) perovskite catalysts were employed for simultaneous NO and Hg0 removal. The perovskite structure is beneficial for low temperature catalysis. The substitution of A-site cations with cerium (Ce) cations significantly improved the catalytic activity of perovskite catalyst. 90% NO conversion and 98% Hg0 oxidation was attained using La0.8Ce0.2MnO3 catalyst at 200 °C. Hg0 oxidation posed negligible effect on NO reduction. Compared to the N2 plus 4% O2 atmosphere, Hg0 oxidation was significantly facilitated by selective catalytic reduction atmosphere. The enhancement in Hg0 oxidation was probably attributed to NO2 originated from NO. Furthermore, a possible reaction mechanism was proposed, in which surface oxygen, Mn4+ and Ce4+ contributed to NO and Hg0 removal. Such knowledge provides useful information for the development of effective and economical NO and Hg0 removal technology for coal-fired power plants.

Section: Industrial and Engineering Chemistry Researchmentioning

confidence: 99%

Simultaneous NO Reduction and Hg⁰ Oxidation over La_0.8Ce_0.2MnO₃ Perovskite Catalysts at Low Temperature

Yang

Zhang

et al. 2018

Self Cite

“…Figure 11 shows that the mercury on the catalyst decomposed in the temperature range 400−500 °C with a peak at about 480 °C, which was matched with the decomposition temperature of HgO. 48 There was no other mercury species observed over the TPD spectra. Thus, during the photocatalytic removal process, most of Hg 0 was oxidized by O 2…”

Section: Industrial and Engineering Chemistry Researchmentioning

confidence: 73%

Elemental Mercury Removal from Flue Gas over TiO₂ Catalyst in an Internal-Illuminated Honeycomb Photoreactor

Yang

Zhao

et al. 2018

Self Cite

TiO 2 catalyst in an internal-illuminated honeycomb photoreactor was prepared for Hg 0 removal from flue gas. The Hg 0 removal efficiency was above 95% under the optimal operation condition. With the increasing TiO 2 coating value, the Hg 0 removal efficiency significantly increased. The catalyst calcined at 400 °C presented optimal Hg 0 removal performance, while higher calcination temperature weakened the Hg 0 photocatalytic removal activity. Similar Hg 0 removal performances were obtained under UV irradiation when the reaction temperature was in the range 25−90 °C, and 1.5 mW/cm 2 of UV light irradiation was competent for Hg 0 photocatalytic removal. With the same quantity utilization of TiO 2 catalyst, the internal-illuminated honeycomb photoreactor presented better Hg 0 removal performance than the fixed-bed reactor. Finally, the procedure of Hg removal from flue gas over TiO 2 catalyst in internal-illuminated honeycomb photoreactor was proposed, and the product in the Hg 0 photocatalytic removal process was analyzed as well.

“…Some mercury remained in the solid state during the actual coal gasification process. In principle, the retention of mercury in ash is generally attributed to the adsorption and oxidation of mercury by magnetite in fly ash and unburned charcoal (carbon residue). , In summary, the adsorption and oxidation of mercury by metal oxides in coal ash during the traditional coal gasification process plays an important role in the retention of Hg(g).…”

Section: Resultsmentioning

confidence: 99%

Transformation and Migration of Mercury during Chemical-Looping Gasification of Coal

Guo

2019

Transformation and migration of mercury during coal chemical-looping gasification (CLG) of lignite were studied in a batch-fluidized bed with magnetic CuFe2O4 as the oxygen carrier. The results showed that mercury distribution in CLG was similar to that in conventional coal gasification. Compared to conventional coal gasification, the CuFe2O4 oxygen carrier promoted transformation of Hg(g) to particle-bound mercury (Hgp) and elemental mercury (Hg0) to gaseous oxidized mercury (Hg2+). X-ray photoelectron spectroscopy results indicated the CuFe2O4 oxygen carrier can promote the Hg(g) transformation into Hgp because of the adsorption and oxidation of mercury on their surface. Thermodynamic calculations showed that the oxygen carrier can affect the concentration of oxidizing gases (e.g., Cl2, SO2, or NO2); this indirectly affected the transformation of Hg0 to Hg2+. In addition, 10 reducing–oxidizing cycles were investigated, and the reduced CuFe2O4 oxygen carriers were regenerated in an air reactor. The ability of the CuFe2O4 oxygen carrier to retain mercury increased slightly after 10 regeneration cycles.