| 1. |
- Hu, Junhao, et al.
(author)
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Co-gasification of coal and biomass : Synergy, characterization and reactivity of the residual char
- 2017
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 244, s. 1-7
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Journal article (peer-reviewed)abstract
- The synergy effect between coal and biomass in their co-gasification was studied in a vertical fixed bed reactor, and the physic-chemical structural characteristics and gasification reactivity of the residual char obtained from co-gasification were also investigated. The results shows that, conversion of the residual char and tar into gas is enhanced due to the synergy effect between coal and biomass. The physical structure of residual char shows more pore on coal char when more biomass is added in the co-gasification. The migration of inorganic elements between coal and biomass was found, the formation and competitive role of K2SiO3, KAlSiO4, and Ca3Al2(SiO4)(3) is a mechanism behind the synergy. The graphization degree is enhanced but size of graphite crystallite in the residual char decreases with biomass blending ratio increasing. TGA results strongly suggest the big difference in the reactivity of chars derived from coal and biomass in spite of influence from co-gasification.
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| 2. |
- Sun, Shao, et al.
(author)
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Evolution of future precipitation extremes: Viewpoint of climate change classification
- 2022
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In: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 42:2, s. 1220-1230
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Journal article (peer-reviewed)abstract
- Climate change is often described as the average changes in temperature and precipitation; however, it is the change in climate extremes determines the levels of socioeconomic impacts related to climate change. It is generally believed that global warming drives increase in frequency, intensity and duration of precipitation extremes, but these changes vary regionally. Focusing on the relationships between evolution of extreme events and long-term climate change, here we propose a novel classification scheme based on Kӧppen's system and changes in mean and variability of precipitation, divide the global climate into 20 different changing types and reveal the regional evolution of precipitation extremes. We find that precipitation extremes ascend significantly in wetting regions, especially in tropical and temperate zones, independent with changed variability. As for drying regions, the evolution of extremes is related to precipitation variability. An increase of extremes can still be detected in fluctuant-drying areas, while a slight decrease can be seen in stabilized-drying areas. It is surprising to find increase in both wetness and dryness extremes which implies higher intensity of meteorological hazards in densely populated areas. Based on the current and projected growth of population exposure to precipitation extremes, we identify some hotspots with high potential risk in the future.
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| 3. |
- Zhu, Youjian, et al.
(author)
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Characterization of Hydrochar Pellets from Hydrothermal Carbonization of Agricultural Residues
- 2018
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In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 32:11, s. 11538-11546
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Journal article (peer-reviewed)abstract
- In this work, the effects of operating conditions of hydrothermal carbonization on the hydrochar pelletization and combustion characteristics were investigated. Corn stalk was carbonized under different conditions and then pelletized to obtain the hydrochar pellets. It was found that hydrothermal temperature and residence time greatly affect the pellet quality. When the temperature was raised up to 240 °C with the residence time longer than 60 min, the heating values of hydrochar were close to or even higher than those of lignite. After hydrothermal treatment, 73.71-94.71% K and 91.81-94.32% Cl contained in the feedstock were removed, indicating a low fouling and slagging tendency when the pellets are used in combustion. The compressive strength and durability increased first with increasing temperature and then decreased with further increasing the temperature from 240 to 300 °C. The influence of residence time showed a similar trend, and the compressive strength and durability reached its maximum value at the temperature of 240 °C and residence time of 60 min. The hydrophobicity of the hydrochar pellets increased with increasing the temperature and residence time. Hydrochar pellets obtained at the temperature of 240 °C with residence time of 60 min gives the best performance, which can meet the requirement of industrial fuel pellets. Finally, the combustion characteristics were investigated by thermogravimetric analysis, and the results indicated that hydrochar pellets were combusted in a comparatively mild way with a high thermal efficiency. As a general conclusion, the hydrochar pellets have much better qualities than the raw corn stalk, facilitating the transportation, long-term storage, and combustion application.
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| 4. |
- Zhu, Youjian, et al.
(author)
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P-Based Additive for Reducing Fine Particulate Matter Emissions during Agricultural Biomass Combustion
- 2019
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In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 33:11, s. 11274-11284
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Journal article (peer-reviewed)abstract
- To understand the influence of P-containing compounds on particulate matter (PM) emissions from the combustion of agricultural residues, the combustion of cornstalk was performed with the addition of a phosphorus-based additive, namely, ammonium dihydrogen phosphate (NH4H2PO4), in a fixed-bed combustion system. Simultaneously the ash samples, including PM collected by a Dekati low-pressure impactor (DLPI) and residual ash, were analyzed with variant analytical techniques. It was found that NH4H2PO4 addition significantly reduced PM0.1 and PM0.1-1 yields but increased PM1-10 yields. The maximum PM0.1 and PM1 reduction efficiency can reach up to 50% at an optimal P/K molar ratio equal to 1. Meanwhile, the addition of NH4H2PO4 to cornstalk changed the chemical composition of PM1 from being dominated by KCl and KOH/K2CO3 with a small amount of K2SO4 to a system dominated by KPO3 and KCl with a small amount of K2SO4. Simultaneously, the possible PM1 reduction mechanism was proposed. In addition, the residual ash after combustion was rich in K- and P-containing species, indicating a potential utilization as a fertilizer. It showed that the addition of NH4H2PO4 is a promising approach to reduce PM1 emissions during the combustion of agricultural biomass.
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| 5. |
- Zhu, Youjian, et al.
(author)
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Reduction of fine particulate matter emissions from cornstalk combustion by calcium phosphates additives
- 2021
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In: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 283
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Journal article (peer-reviewed)abstract
- The emission of fine particulate matters with an aerodynamic diameter of less than 1 µm (PM1) is usually high from straw biomass combustion, resulting in great danger to atmospheric environment and public health. In this work, the effect of three calcium phosphate additives on PM1 emission from cornstalk combustion was investigated using a lab-scale reactor. The addition of Ca(H2PO4)2, CaHPO4 and Ca3(PO4)2 reduced PM1 emission by 1.5–50.6%, 22–55.6% and 23–53.7%, respectively. For Ca(H2PO4)2, PM1 reduction rate reached its maximum values of 50.6% at P/K molar ratio equal to 1 and then decreased significantly with further increasing of P/K molar ratio. For both CaHPO4 and Ca3(PO4)2, PM1 reduction rate increased approximately linearly with increasing the amount of additives under the current operating conditions. Analyses of the collected particulate matters and residual ashes indicated that phosphorus was mainly transformed into PM1-10 and residual ash in the form of K-Ca/Mg phosphates and Ca/Mg phosphates, respectively. The PM1 reduction mechanism was proposed based on the characterization results. Finally, economic analysis showed that the addition of Ca3(PO4)2 is a potentially promising method to reduce PM1 emissions during straw biomass combustion.
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