Browsing by Author "Zhang, Yue"

Now showing 1 - 8 of 8
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    Ammonia inhibition and toxicity in anaerobic digestion: a critical review
    (Elsevier, 2019-07-20) Jiang, Ying; McAdam, Ewan; Zhang, Yue; Heaven, Sonia; Banks, Charles J.; Longhurst, Philip
    As a waste management technology which offers environmental benefit and renewable energy production, anaerobic digestion (AD) has become the preferred technology for the treatment of organic waste. However, in such waste streams nitrogen contents are likely to be high. There is prevailing literature evidence suggests that high ammonia concentration especially its free molecular form (NH3), derived from nitrogen content in substrates is the cause of inhibition and sudden failure of the AD process. This paper comprehensively reviews previous knowledge from digestion studies using high nitrogen waste streams as feedstocks and critically analysed the considerable variations in the inhibition/toxicity levels reported for ammonia. Literature evidences suggest methanogens, particularly acetoclastic methanogens are most susceptible to ammonia toxicity, and therefore this review has a particular focus on the mechanism of the ‘selective’ inhibition to methanogens and the impact of ammonia toxicity to the overall methanogen population in an AD digester. This population change explains in many reported cases that sufficient acclimatisation can significantly alleviate the phenomenon of inhibition and specific requirement of certain trace nutrients. Currently available mitigation strategies for high nitrogen content feedstock digestion are reviewed and discussed in relation to the population change and trace nutrient requirements.
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    The effect of H2O on formation mechanism of arsenic oxide during arsenopyrite oxidation: Experimental and theoretical analysis
    (Elsevier, 2019-12-07) Zou, Chan; Wang, Chunbo; Chen, Liang; Zhang, Yue; Xing, Jiaying; Anthony, Edward J.
    The effect of H2O on arsenic release behavior was investigated via experiment and first-principles density functional theory (DFT). The experimental results show that sulfide-bound arsenic is the main form present in coal, and that H2O has a positive influence on the release of arsenic during coal combustion. Furthermore, DFT calculations were performed to investigate the mechanism for H2O influence on arsenic oxidation. Thermodynamic and kinetic analyses were also conducted to study the influence of temperature on the reaction process. From thermodynamic analysis, arsenic oxide formation on the FeS2 (1 0 0) surface with and without H2O weakens with increasing temperature. In addition, the equilibrium constant for the reaction with H2O addition is slightly higher than that for the reaction without H2O, which suggests that the degree of the chemical reaction in the presence of H2O should increase. From kinetic analysis, the reaction rate constants increase with temperature, and the activation energy of the arsenic oxide formation reaction with and without H2O is 100.72 kJ/mol and 124.08 kJ/mol, respectively. This indicates that H2O adsorption on the surface can decrease the energy barrier and accelerate the reaction forming arsenic oxide. Based on the thermodynamic and kinetic analyses, it can be concluded that temperature has an inhibitory influence on reaction equilibrium and positive influence on the reaction rate. The experiment and calculation results explain the influence of H2O on the formation mechanism of arsenic oxide and provide a theoretical foundation for the emission and control of arsenic.
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    Investigation of the impact of trace elements on anaerobic volatile fatty acid degradation using a fractional factorial experimental design
    (Elsevier, 2017-09-05) Jiang, Ying; Zhang, Yue; Banks, Charles; Heaven, Sonia; Longhurst, Philip
    The requirement of trace elements (TE) in anaerobic digestion process is widely documented. However, little is understood regarding the specific requirement of elements and their critical concentrations under different operating conditions such as substrate characterisation and temperature. In this study, a flask batch trial using fractional factorial design is conducted to investigate volatile fatty acids (VFA) anaerobic degradation rate under the influence of the individual and combined effect of six TEs (Co, Ni, Mo, Se, Fe and W). The experiment inoculated with food waste digestate, spiked with sodium acetate and sodium propionate both to 10 g/l. This is followed by the addition of a selection of the six elements in accordance with a 26−2 fractional factorial principle. The experiment is conducted in duplicate and the degradation of VFA is regularly monitored. Factorial effect analysis on the experimental results reveals that within these experimental conditions, Se has a key role in promoting the degradation rates of both acetic and propionic acids; Mo and Co are found to have a modest effect on increasing propionic acid degradation rate. It is also revealed that Ni shows some inhibitory effects on VFA degradation, possibly due to its toxicity. Additionally, regression coefficients for the main and second order effects are calculated to establish regression models for VFA degradation.
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    Quantifying the percentage of methane formation via acetoclastic and syntrophic acetate oxidation pathways in anaerobic digesters
    (Elsevier, 2017-04-07) Jiang, Ying; Banks, Charles; Zhang, Yue; Heaven, Sonia; Longhurst, Philip J.
    Ammonia concentration is one of the key factors influencing the methanogenic community composition and dominant methanogenic pathway in anaerobic digesters. This study adopted a radiolabelling technique using [2-14C] acetate to investigate the relationship between total ammonia nitrogen (TAN) and the methanogenic pathway. The radiolabelling experiments determined the ratio of 14CO2 and 14CH4 in the biogas which was used to quantitatively determine the percentage of CH4 derived from acetoclastic and syntrophic acetate oxidation routes, respectively. This technique was performed on a selection of mesophilic digesters representing samples of low to high TAN concentrations (0.2–11.1 g kg−1 wet weight). In high TAN digesters, the ratio between 14CO2 and 14CH4 was in the range 2.1–3.0; indicating 68–75% of methane was produced via the hydrogenotrophic route; whereas in low ammonia samples the ratio was 0.1–0.3, indicating 9–23% of methane was produced by the hydrogenotrophic route. These findings have been confirmed further by phylogenetic studies.
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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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    Scaling-up engineering biology for enhanced environmental solutions
    (American Chemical Society, 2024-06-21) Hassard, Francis; Curtis, Thomas P.; Dotro, Gabriela C.; Golyshin, Peter; Gutierrez, Tony; Heaven, Sonia; Horsfall, Louise; Jefferson, Bruce; Jones, Davey L.; Krasnogor, Natalio; Kumar, Vinod; Lea-Smith, David J.; Le Corre Pidou, Kristell; Liu, Yongqiang; Lyu, Tao; McCarthy, Ronan R.; McKew, Boyd; Smith, Cindy; Yakunin, Alexander; Yang, Zhugen; Zhang, Yue; Coulon, Frederic
    Synthetic biology (SynBio) offers transformative solutions for addressing environmental challenges by engineering organisms capable of degrading pollutants, enhancing carbon sequestration, and valorizing waste (Figure 1). These innovations hold the potential to revolutionize bioremediation strategies, ecosystem restoration, and sustainable environmental management.
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    Simultaneous removal of SO2 and NOx by a new combined spray-and-scattered-bubble technology based on preozonation: from lab scale to pilot scale
    (Elsevier, 2019-03-28) Si, Tong; Wang, Chunbo; Yan, Xuenan; Zhang, Yue; Ren, Yujie; Hu, Jian; Anthony, Edward J.
    A new technology (called here, spray-and-scattered-bubble technology) based on preozonation was designed and tested for simultaneous removal of SO2 and NOx from power plant flue gas. It combines the advantages of the common spray tower and the jet bubble reactor, in which the flue gas experiences an initial SO2/NOx removal in the spray zone and then undergoes further removal in the bubble zone. Factors that affect the simultaneous removal of SO2/NOx were investigated through lab-scale experiments, by varying the O3/NO molar ratio, liquid/gas ratio and the immersion depth. The results showed the removal of SO2 and NOx can be significantly improved as compared to a separate spray column or bubble reactor, by as much as 17%, for the spray column and 18% for the bubble reactor for NOx and 11% for the spray column, and 13% for the bubble reactor for SO2, for liquid/gas ratio of 4 dm3/m3 or immersion depth of 100 mm. The O3/NO molar ratio had little effect on the SO2 removal, but it strongly affected the removal efficiency of NOx especially when it was less than 1.0. Both the liquid/gas ratio and immersion depth demonstrated a positive correlation with the removal efficiency. However, a balance must be maintained between efficiency and economics, since the liquid/gas ratio directly influences the performance and number of the circulating pumps, and the depth is closely related to the flue gas pressure drop, and both factors affect energy requirements. To further confirm its industrial feasibility, a 30 h test using real coal-fired flue gas was conducted in a pilot-scale experimental facility (flue gas volume of 5000 Nm3/h). Increasing SO2 concentration in flue gas can promote the removal efficiency of NOx, but the SO2 removal was almost complete under all conditions tested. Finally, taking a 300 MW unit as an example,- the total energy cost of this new technology is estimated as being 10% lower than that of the common spray tower technology, based on an analysis using Aspen Plus™, with the largest difference reflected in the energy requirements of the circulating pumps and the ozonizer. Over all, the new technology offers the joint advantages of reducing emissions and saving energy.
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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.