Browsing by Author "Liu, Huimin"

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    Effect of H2O on the volatilization characteristics of arsenic during isothermal O2/CO2 combustion
    (Elsevier, 2019-03-06) Zou, Chan; Wang, Chunbo; Liu, Huimin; Chen, Liang; Anthony, Edward J.
    The effect of H2O on the volatilization behavior of arsenic in coal was studied under O2/CO2 combustion conditions at 800–1300 ºC, which covers the effective range of coal combustion temperatures appropriate for conventional coal combustion technologies. By controlling the combustion time of the coal, the volatilization percentage and rate of As emissions versus time were obtained. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were used to study the evolution of minerals with and without H2O under O2/CO2 combustion conditions. The effect of CO2 on As volatilization was first investigated and it was found that increasing CO2 concentrations inhibits the volatilization of As, with this effect decreasing with increasing temperature. When a fraction of the CO2 was replaced with H2O, the volatilization of As increased, but the positive effect of H2O also decreased with increasing temperature. The volatilization percentage of As with 30% H2O was 6.1% higher than that without H2O at 800 ºC, while it was only 2.7% higher at 1300 ºC. When the concentration of H2O increased from 0 to 30%, the peak value of the As volatilization rate increased and the time needed to reach the peak value decreased. The volatilization characteristics of As for three coals were very similar, which demonstrates that the effect of H2O was not limited to only one specific coal.
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    Review of arsenic behavior during coal combustion: Volatilization, transformation, emission and removal technologies
    (Elsevier, 2018-04-17) Wang, Chunbo; Liu, Huimin; Zhang, Yue; Zou, Chan; Anthony, Edward J.
    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 pathways 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 effectiveness of flue gas arsenic removal technologies with different kinds of adsorbents, including calcium-based adsorbents, metal oxides, activated carbon, and fly ash.
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    Vaporization model for arsenic during single-particle coal combustion: Model development
    (Elsevier, 2019-03-15) Liu, Huimin; Wang, Chunbo; Zhang, Yue; Zou, Chan; Anthony, Edward J.
    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.