Experiment and mechanism research on gas-phase As2O3 adsorption of Fe2O3/γ-Al2O3

Progress in Energy and Combustion Science

Liu

Zhang

et al. 2018

Self Cite

170

Growing public awareness of the environmental impact of coal combustion has raised serious concerns about the various hazardous trace elements produced by coal firing. Arsenic deserves special attention due to its toxicity, volatility, bioaccumulation in the environment, and potential carcinogenic properties. As the main anthropogenic source of arsenic is coal combustion, its behavior in power plants is of concern. Unlike mercury, arsenic behavior in coal combustion has not been subjected to systematic, in-depth research. Different researchers have reached opposing conclusions about the behavior of arsenic in combustion systems and as yet there is relatively little research on arsenic-removal technologies. In this paper, the volatilization, transformation, and emission behavior of arsenic and its removal technologies are discussed in depth. Factors affecting the volatilization characteristics of arsenic are summarized, including temperature, pressure, mode of occurrence of arsenic, coal rank, mineral matter, and the sulfur and chlorine content of the fuel. The behavior of arsenic during oxy-fuel combustion and the effect of combustion atmosphere (O2, CO2, SO2 and H2O(g)) are also reviewed in detail. In order to better understand the pathway of arsenic in a power plant environment, a particular focus in this work is the transformation mechanism of ultra-fine ash particles and the partitioning behavior of arsenic. Finally, the effects of air pollution control devices (APCDs) on arsenic emissions are examined, along with the

Section: Removal Of Arsenic By Metal Oxide Sorbentsmentioning

confidence: 99%

Review of arsenic behavior during coal combustion: Volatilization, transformation, emission and removal technologies

Progress in Energy and Combustion Science

Liu

Zhang

et al. 2018

Self Cite

170

“…Song et al have demonstrated that As 2 O 3 (g) could be fixed on the surface of CaO to form Ca 3 (AsO 4 ) 2 due to the chemical bonding between the adsorbates and adsorbents . Zhang et al pointed out that Fe 2 O 3 /γ-Al 2 O 3 could adsorb As 2 O 3 with the effect of catalytic oxidation . Yaming et al illustrated that As 2 O 3 could be transformed into AsO 4 3– and AsO 3 3– with or without O 2 on the CaO (0 0 1) surface, while tricalcium orthoarsenate (Ca 3 As 2 O 8 ) and dicalcium pyroarsenate (Ca 2 As 2 O 7 ) could be formed according to different adsorption structures .…”

Section: Introductionmentioning

confidence: 99%

“…4 Zhang et al pointed out that Fe 2 O 3 /γ-Al 2 O 3 could adsorb As 2 O 3 with the effect of catalytic oxidation. 5 Yaming et al illustrated that As 2 O 3 could be transformed into AsO 4 3− and AsO 3 3− with or without O 2 on the CaO (0 0 1) surface, while tricalcium orthoarsenate (Ca 3 As 2 O 8 ) and dicalcium pyroarsenate (Ca 2 As 2 O 7 ) could be formed according to different adsorption structures. 6 Lee et al pointed out that TiO 2 could demonstrate a decent arsenic retention property which could be further enhanced after being sulfated because of the increment of Lewis and Bronsted acid sites.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of NO_xwith NH₃on γ-Al₂O₃and Its Effects on the Adsorption of As₂O₃Based on DFT

2021

Ind. Eng. Chem. Res.

The characteristics of NO x (NO and NO2) and NH3 adsorptions and their impacts on As2O3 adsorption on γ-Al2O3 are essential for the development of catalyst protection technologies in the selective catalytic reduction (SCR) process. Mechanisms of the mentioned adsorption processes are calculated via density functional theory (DFT) in this study so as to reveal adsorption structures and other features. According to DFT calculation results, both NO x and NH3 could convert the physisorption structures from oxygen atoms of the first layer to chemisorption structures (with only one exception). In the meantime, other original chemisorption structures still belong to chemisorption even though their adsorption energies decrease a little. This phenomenon resulted from the different adsorption positions of NO x and NH3 on the surface of γ-Al2O3 and the changes of band structures incurred by the significantly increased electronegativity and nearby hydrogen bonds. Contents of this study could provide helpful information for understanding the behavior of γ-Al2O3 in the context of the SCR process.

“…Numerous studies have reported the vaporization characteristics of arsenic based on experimental measurements. The effects of coal properties [8,9], arsenic speciation [10][11][12][13][14], mineral components [15][16][17] as well as gas composition [18][19][20] on the vaporization ratio of arsenic have all been examined experimentally. However, all of these experiments are limited to providing a final vaporization ratio without considering how such emissions change during the coal burning process.…”

Section: Introductionmentioning

confidence: 99%

Vaporization model for arsenic during single-particle coal combustion: Model development

Liu

Zhang

et al. 2019

Combustion and Flame

Self Cite

The kinetic parameters for chemical reactions associated with the vaporization of arsenic species are rarely reported due to the difficulties in obtaining suitably purified arsenic compounds as well as the issues associated with the extreme toxicity of many arsenic species. Here, we used a single-particle coal combustion model combined with a vaporization yield model of arsenic fitted by experimental data, which was used to determine the activation energy and frequency factor of the oxidation/decomposition reactions of arsenic species in this work, namely: As-org, FeAsS, FeAsO4 and Ca3(AsO4)2. The combustion kinetics of volatile/char and arsenic thermodynamic properties were used to model the vaporization zone and intensity of emissions for arsenic compounds. The results show that the reaction kinetic parameters of these arsenic species could be determined within an order of magnitude despite the variation of compositions in the coal sample and temperature, and this approach provides a new method to determine the reaction kinetics of hazardous elements such as As. Combining the vaporization yield and reaction kinetics of arsenic species with the single-particle coal combustion model, a novel vaporization model of arsenic was developed. With this model, the temporal evolution of combustion parameters (temperature, conversion ratio of coal, particle porosity, flue gas concentration) as well as arsenic vaporization ratio and As2O3(g) concentration can be predicted at the microscopic level. Model applications and predictions can be found in Part 2 of this work [Vaporization model of arsenic during single-particle coal combustion: Part 2. Numerical simulation].